Neuroradiology On the Net

Band heterotopia

2011-03-14T16:00:00.000+01:00

CASE 1 (7-month-old)

CASE 2 (Pre-adolescent)

Findings

Case 1: Axial and coronal T2-weighted images of the brain in a 7-month-old girl with seizures demonstrate a band of isointense signal within the subcortical white matter, characteristic of band heterotopia.
Case 2: Axial and coronal T1-weighted images demonstrate band heterotopia, better seen in this preadolescent girl due to completion of myelination.

Diagnosis: Band heterotopia

Band heterotopia is a rare neuronal migration anomaly which manifests as homogenous bands of gray matter are interposed between the lateral ventricles and cortical mantle with normal appearing white matter on either side. The overlying cortex may be normal, pachygyric, or display a simplified gyral pattern with short gyri and shallow sulci. At least six morphologically distinct subtypes have been described. Band heterotopias represent a subset of gray matter heterotopia which also includes subependymal and subcortical heterotopia subtypes.

Band heterotopia typically affects female patients as a result of an X-linked dominant inheritance pattern secondary to abnormal function of the doublecortin (DCX) gene (Xp22.3-p23) or less frequently the LIS1 (17p13.3) gene. Male patients can be affected due to sporadic mutations of these genes (41 reported cases in the literature by D’Agostino, et al in 2002). The rate of detectable mutations involving DCX or LIS1 in male patients (42%) is lower than the rate of 85% described in female patients. Dysmorphic features described in patients with band heterotopia include microcephaly (most common), wide nasal bridge, high arched palate, and short stature.

The clinical presentation of band heterotopia can range from normal to nearly normal intelligence and mild developmental delay to frank mental retardation. Seizures are often also present and may begin in the first decade, ranging from partial to generalized or multiple seizure types. The discovery of the underlying brain malformation is due to the onset of seizures in 65% of patients. Eventually 95% of patients with band heterotopias will develop epilepsy. Seizures associated with band heterotopia are often refractory to medical therapy, and surgical therapies such as callosotomy may be performed in these patients. In the series of 30 male patients published in 2002, 46% of patients were refractory to medical therapy and experienced up to 20-30 seizures daily despite trails of multiple therapeutic regimens. Affected male patients tend to have either mild or severe symptoms, whereas, female patients tend to have symptoms within the mild to moderate range of the spectrum from minimal cognitive impairment to severe mental retardation. Posterior involvement, in particular the partial posterior and intermediate posterior subtypes, occur more commonly in male patients. Frontal and diffuse subtypes are more often present in affected female patients.

Chloroma of epidural space

2011-03-07T16:00:00.000+01:00

Additional clinical history: Acute leukemia.

Findings

Large anterior epidural mass extending from posterior clinoid to the cervicothoracic junction measuring approx. 6x3x1.5 cm with mass effect on the anterior pons, medulla, and upper cervical cord. No post-contrast imaging obtained.

Differential diagnosis: Epidural mass
- Metastatic disease
- Lymphoma
- Leukemia/chloroma
- Chordoma
- Osteomyelitis/epidural abscess
- Epidural hematoma
- Primary tumor such as neurofibroma/schwannoma

Diagnosis: Chloroma of epidural space

Key points

AKA granulocytic sarcoma, extramedullary myeloblastoma.
Most commonly occurs in the setting of AML.
Can also occur in setting of chronic myelogenous leukemia and other myeloproliferative disorders.
These tumors can involve any part of the body, either concurrently or sequentially.

Imaging characteristics:
- NECT: Isodense or hyper dense to brain or muscle
- MR: Hypo intense or Iso intense on T1-weighted MR images, heterogeneously Iso intense or hyper intense on T2-weighted MR images
- MR+C: Enhance homogeneously after injection of contrast medium

Paraspinal and intraspinal lesions are also thought to arise from perivenous arachnoid spread of leukemic cells. Uncommonly, spinal involvement by granulocytic sarcoma may cause compression of the spinal cord, cauda equina, or nerve roots

Basilar dolichoectasia determining a vascular loop compression syndrome

2011-03-01T16:00:00.009+01:00

Findings

Figure 1, Figure 2, Figure 3, Figure 4, and Figure 5: Axial high resolution T2 fiesta images show a dilated and tortuous basilar artery which extends into the left cerebellopontine angle. The visualized inner ear structures are normal.
Figure 6: The basilar artery appears to contact the left trigeminal nerve at the root-exit zone.

Diagnosis: Basilar dolichoectasia

Trigeminal neuralgia is a clinical syndrome composed of paroxysmal facial pain usually confined to the maxillary (V2) and/or mandibular (V3) branches of the trigeminal nerve. Occasionally the opthalmic division (V1) is also affected. This syndrome is more common in patients over the age of 65, with no gender specificity.

VLCS is a recognized cause of trigeminal neuralgia. The offending vessel courses into the anterior cerebellopontine cistern with subsequent irritation of the 5th cranial nerve at the preganglionic root entry zone (REnZ). Additional causes of trigeminal neuralgia include anuersysms, AVMs, and tumors of the cerebello-pontine angle. Demyelinating disorders such as multiple sclerosis are also described as a potential cause.

Thin section high resolution T2 MRI of the CPA/IAC allows the best visualization of the vascular loop. These images also show the anatomic course of the 5th cranial nerve from the root entry zone into meckel’s cave. The imaging protocol should include whole brain T2/FLAIR to exclude additional etiologies such as multiple sclerosis. Axial and coronal T1 of the brainstem with gadolinium enhancement is also helpful to look for cranial neuritis, perineural tumor, and cisternal tumor such as an epidermoid, schwanomma, or meningioma.

Lateral medullary syndrome (Wallenberg syndrome)

2011-02-23T16:00:00.001+01:00

Findings

Axial FLAIR (Figure 1 and Figure 2) and T2-weighted (Figure 3 and Figure 4) images demonstrate mild signal hyperintensity in region of the left lateral and posterior medulla PICA territory.
Axial DWI (Figure 5 and Figure 6) and matching ADC maps (Figure 7 and Figure 8) demonstrate true restricted diffusion in the left lateral and posterior medulla PICA suggestive of cytotoxic edema fort an acute infarction.
3D TOF posterior circulation MIP projection (Figure 9) demonstrates absence of a normal left PICA. It's possibile to see the right PICA for comparison, arising from the distal right intracranial vertebral artery. There is also a mild narrowing of the basilar artery. It's possibile also to appreciate bith the superior cerebellar arteries.

Diagnosis: Lateral medullary syndrome (Wallenberg syndrome)

Adolf Wallenberg (November 10, 1862-1949) was a German internist and neurologist who first described the clinical manifestations (1895) and the autopsy findings (1901) in occlusions of the arteria cerebelli posterior inferior (Wallenberg syndrome).

Lateral medullary syndrome is characterized by sensory deficits affecting the trunk and extremities on the opposite side of the infarct and sensory, and motor deficits affecting the face and cranial nerves on the same side with the infarct. Other clinical symptoms and findings include ataxia, facial pain, vertigo, nystagmus, diplopia, Horner syndrome, and dysphagia. The cause of this syndrome is secondary to occlusion of the PICA near its origin. Similar symptoms may be produced by vertebral artery occlusion near the origin of the PICA.

Afflicted persons can have dysphagia resulting from involvement of the nucleus ambiguus and slurred speech (dysphonia and dysarthria). Damage to the spinal trigeminal nucleus causes absence of pain on the ipsilateral side of the face as well as an absent corneal reflex. The spinothalamic tract can be damaged, resulting in loss of pain and temperature sensation to the opposite side of the body. Damage to the cerebellum can cause ataxia. Damage to the hypothalamospinal fibers disrupts sympathetic nervous system relay and gives symptoms analogous to Horner syndrome (ptosis, anhidrosis, and miosis).

In older patients, the most common cause of posterior circulation ischemia is thromboembolic disease resulting from accelerated atheromatous disease or embolic disease from a cardiac source. In young patients with posterior fossa ischemia, in addition to embolic disease, the diagnosis of arterial dissection should also be considered.
Wallenberg syndrome synonyms: dorsolateral medullary syndrome, lateral bulbar syndrome, lateral medullary infarction syndrome, and PICA syndrome.

Subdural empyema

2011-02-08T16:00:00.001+01:00

Findings

A large left middle cranial fossa subdural empyema is demonstrated, with a relatively thin rim of enhancement. Internally, there is a large quantity of debris. There is mass effect, with a modest midline shift and effacement of the left lateral ventricle. Inflammatory changes are demonstrated in the left temporal bone which is likely the source of the abscess. There is diffusion restriction, not marked, consistent with abscess. There is extensive dural enhancement, along with considerable surrounding edema.

Differential diagnosis:
- Subdural empyema
- Chronic subdural hematoma
- Subdural effusion
- Subdural hygroma
- Dural metastasis

Diagnosis: Large left middle cranial fossa subdural empyema; left mastoiditis

Key points

Loculated collection of pus in subdural space
Best diagnostic clue: Extra-axial collection with contrast enhancing rim
Supratentorial typical
Infratentorial (up to 10%), often associated with mastoiditis
Crescentic typical; may be lens shaped on coronal images
CT demonstrates extra-axial collection, iso-to hyper dense to CSF on noncontrasted CT; shows strong peripheral enhancement with contrast
Best imaging tool: MR with DWI to demonstrate presence, nature, extent and complications
T1W image shows:
Extra-axial collection hyper intense to CSF
Crescentic extra-axial collection
T2WI demonstrates a lesion that is Iso-to hyper intense to CSF,
FLAIR shows a crescentic fluid collection which is hyper intense to CSF, underlying brain may be hyper intense
DWI shows restricted diffusion (increased signal intensity); Differentiates subdural empyema from subdural effusions
T1WI post contrast shows:
Prominent enhancement at margin related to granulomatous tissue and inflammation
Encapsulating membranes enhance strongly, may be loculated with internal fibrous strands
May see enhancement of adjacent brain parenchyma
MRV may show venous thrombosis seen as a lack of flow
CT may miss small collections
Complications include cerebritis and brain abscess, cortical vein and dural sinus thrombosis, and cerebral edema
Subdural empyema is much more common than epidural empyema
In older children, adults: Related to paranasal sinus disease (>2/3), in infants and young children it can be a complication of bacterial meningitis
Most common signs/symptoms include fever, headaches, meningismus, sinusitis, cerebritis
Sinus or ear infection in > 75% of cases
Confused with meningitis which may lead to delayed diagnosis
Can occur at any age
Rare, yet high mortality rate.
If subdural or epidural abscess is discovered, look also for sinusitis, otomastoiditis, dural sinus thrombosis and brain abscess
Progresses rapidly, neurosurgical emergency
Surgical drainage via wide craniotomy is gold standard

Benign perimesencephalic SAH

2010-12-31T16:00:00.000+01:00

Findings

Figure 1, Figure 2, and Figure 3: Axial CT images of the brain demonstrate SAH in the premedullary, prepontine, suprasellar, and interpeduncular cisterns.
Other figures (not shown): Representative images from a 4-vessel cerebral angiogram demonstrate no evidence of aneurysm or vascular malformation.

Diagnosis: Benign perimesencephalic SAH

Trauma and aneurysm are the two most common causes of SAH. At least 80% of cases of atraumatic SAH are caused by rupture of an intracranial aneurysm. When SAH is present, many clinicians request CT or MR angiography in order to quickly and non-invasively diagnose aneurysm. If an aneurysm is not detected with one of these modalities, conventional cerebral angiography (the gold standard for exclusion of aneurysm) is necessary. If the initial angiogram is negative, a second cerebral angiogram, typically performed 1-3 weeks after the first, is mandatory. This is because occasionally an aneurysm will be missed on the initial angiogram due to spasm or partial/complete thrombosis. The diagnosis of non-aneurysmal SAH can be applied to patients who have two consecutive negative technically adequate 4-vessel cerebral angiograms. Additionally, many clinicians request MRI of the spine to exclude the possibility of spinal AVM as a source for SAH.

The classic variety of non-aneurysmal SAH is known as benign perimesencephalic SAH or pretruncal nonaneurysmal SAH. As the name implies, the hemorrhage is situated around the midbrain and anterior to the brainstem in the ambient, interpeduncular, and prepontine cisterns. The term “benign” refers to the fact that after recovery from the initial episode, there is no increased risk of repeat hemorrhage. Cerebral vasospasm is less likely in these patients, but does occur. Hydrocephalus also remains a possibility during the acute phase. Although not clearly understood, one proposed mechanism of benign perimesencephalic SAH is rupture of the venous plexus anterior to the pons (the anterior pontomesencephalic plexus). This is postulated to occur as a result of increased venous pressure from strenuous activities such as exercise. Intramural hematoma of the basilar artery and rupture of a basilar perforating artery have also been suggested as alternate hypotheses.

Although benign perimesencephalic SAH has been known as a distinct clinical entity for some time, patients may present with non-aneurysmal SAH in an atypical distribution (non-perimesencephalic). In some of these patients, the total volume of hemorrhage is increased such that blood is present throughout the basal cisterns and extends over the cerebral convexities. In other patients, the hemorrhage is confined to the convexities, quadrigeminal cistern, or other atypical locations. In today’s case, Patient #1 presented with the classic variety of benign perimesencephalic SAH. Patient #2 presented with atypical non-aneurysmal SAH. Both patients recovered, and have had no repeat episodes of hemorrhage to date.

Possible causes of SAH:
- Trauma
- Aneurysm
- AVM
- Vasculitis
- Dural AV fistula
- Extension from intraparenchymal hemorrhage
- Dural venous sinus thrombosis
- Infection
- Neoplasm
- Idiopathic

Lumbar disc extrusion with a wrapped disc

2010-12-27T16:00:00.001+01:00

Findings

There is a left central disc extrusion at L5-S1 that causes mild to moderate left lateral recess narrowing and nerve root displacement without nerve root compression. At this level there is also contrast enhancement traversing the left laminectomy defect and encasing the disc extrusion, consistent with a wrapped disc. There is enhancement in the left lateral recess, suggesting post-operative fibrosis.

Differential diagnosis:
- Wrapped disc
- Peridural fibrosis
- Epidural abscess
- Epidural metastasis
- Nerve sheath tumor
- Disc pseudobulge
- Intervertebral disc protrusion
- Intervertebral disc extrusion
- Recurrent intervertebral disc herniation

Diagnosis: Lumbar disc extrusion with a wrapped disc

Key points: "Wrapped" disc

Disc herniation (protrusion, extrusion, or fragment) may be caused by trauma, repetitive or acute, and are a common source of pain and subsequent back surgery in the general population. In the acute phase, the herniated disc stimulates a fibrovascular response. A "wrapped disc" is the focal herniation (protrusion, extrusion, or fragment) that is encased in vascular scar tissue stimulated by this response and is evident by enhancement on contrast-enhanced T1-weighted images.

Asymptomatic or low back pain and/or radiculopathy are most common in the lumbar spine at L4-L5 and L5-S1. A wrapped disc is a post-surgical sequela, particularly following surgery for spinal stenosis in which the surgical procedure is more extensive, involving a laminectomy and a medial facetectomy.

Best imaging modality: MR (sequences: sagittal and axial T2WI and T1WI, as well as contrast-enhanced axial and sagittal T1WI)
Other imaging modalities: CT, myelography

Imaging findings

MR: Anterior extradural mass contiguous with the disc space extending into the spinal canal
*Contrast-enhanced T1WI: Peripheral enhancement surrounding the disc herniation or fragment with/without central canal, lateral recess, or foraminal stenosis and cord or nerve root impingement. (*most helpful MR sequence)
Non-enhanced T1WI: Isointense to parent disc
T2WI: Iso- to hyper intense to parent disc
General disc hypointensity and height loss at the level of the herniation, as well as postoperative changes (laminectomy defects, etc), degenerative facet disease, and osteophytes, are common associated findings.
CT:
Non-contrast CT: An anterior extradural soft tissue mass that may displace the nerve root / indent the thecal sac
Contrast-enhanced CT: Mild peripheral enhancement of the disc herniation/fragment
Myelography: An extradural mass that indents the thecal sac and nerve root sleeves
Imaging findings of other common differential diagnoses
Peridural fibrosis: Scar within epidural space after lumbar surgery that infiltrates epidural fat, causing homogeneous enhancement that diffusely surrounds the thecal sac and nerve root; increased in T2 signal relative to adjacent disc herniation
Epidural abscess: A distinct fluid collection in the epidural space with peripheral enhancement on post-contrast images, often associated with findings of diskitis
Epidural metastasis: Elongated (cranial-caudal orientation) enhancing mass with osseous involvement and may demonstrate paravertebral extension
Nerve sheath tumor: Avid enhancement surrounding the nerve root, some of which are in a "dumbbell" shape
Disc pseudobulge: Smooth generalized extension of the disc margin without a focal defect due to "uncovering" of disc related to spondylolisthesis
Intervertebral disc protrusion: Anterior extradural mass contiguous with disc space and triangular in shape with broader base than apex; no enhancement
Intervertebral disc extrusion: Anterior extradural mass contiguous with disc space by a "neck," in which this herniated disc material then widens in the epidural space
Recurrent intervertebral disc herniation: Extradural mass contiguous with intervertebral disc margin, demonstrating enhancement peripherally but without central enhancement
Treatment
Conservative: Anti-inflammatory and pain medications, avoid trauma
Surgical: Repeat surgery to remove herniated disc (protrusion, extrusion, fragment)

Pseudotumor cerebri - Idiopathic Intracranial Hypertension (IIH)

2010-12-24T16:00:00.001+01:00

Findings

T2W axial MRI (Figure 1) shows signs of increased ICP, but only increased fluid within the optic nerve sheaths, flattening of the posterior orbit, and a partially empty sella.
The 3D TOF MRV Towne and RPO projections (Figure 2 and Figure 3) show bilateral, right greater than left, focal transverse-sigmoid venous sinus junction narrowing’s. It is not a normal MRV given the pt’s history, with more explanation in the discussion. There is no aneurysm or collection of collateral blood vessels seen in these images.

The AP and lateral (Figure 4 and Figure 5) venous phase carotid arteriogram shows long segment stenosis at transverse-sigmoid venous sinus junction distal to the vein of Labbé. Pre procedure venography showed a venous pressure gradient across this lesion of 17 mmH2O with 37 mmH2O on transverse sinus side and 15 mmH2O on internal jugular vein side.

AP and lateral (Figure 6 and Figure 7) venous phase carotid arteriogram shows long segment stenosis at transverse-sigmoid venous sinus junction with a balloon crossing the gradient lesion.

Diagnosis: Pseudotumor cerebri - Idiopathic Intracranial Hypertension (IIH)

Pseudotumor cerebri is defined by typical clinical symptoms which occur in the setting of elevated “idiopathic” ICP and a normal composition of CSF. Classic clinical symptoms include diffuse recalcitrant headaches, vision changes (including vision loss), and hearing changes (e.g., tinnitus), and the disease is typically seen in obese women who are 20-50 years of age. Papilledema is the most common physical exam finding, but visual loss and sixth nerve palsy are also seen. Other symptoms include disabling headaches and blindness. LP opening pressure is greater than 25 cm H2O. Brain computed tomography (CT) and magnetic resonance imaging (MRI) are typically normal, however, the following suggestive non-pathognomonic findings are frequently present:

– Cerebral venous sinus stenoses
– Flattening of the bilateral posterior sclera
– Partially or fully empty sella; enlargement of the chiasmatic recess of the 3rd ventricle
– Distension of perioptic nerve subarachnoid space
– Intraocular protrusion of the optic nerve head
– Orbital optic nerve vertical tortuosity

Treatment for pseudotumor cerebri typically includes medical management with acetazolamide and pain control for headaches. Furosemide and corticosteroids have been used, as well. Surgical interventions to treat pseudotumor cerebri include lumboperitoneal shunt (LPS) and ventriculoperitoneal shunt (VPS), which often produce immediate results, however, eventual return of pseudotumor symptoms occur in approximately 50% within three years. Optic nerve sheath fenestration is also used to treat vision changes, with variable headache relief. Dominant transverse/sigmoid venous sinus angioplasty and stenting are relatively new methods for the treatment of pseudotumor cerebri for those who have significant dural sinus stenosis. Given that 80% of intracranial vascular compliance is provided from the venous vasculature, reduction of pressure in the sinuses reduces CSF pressure. Better results are achieved in patients with documented high pressure gradients, and greater efficacy is seen with regard to arrest of visual loss (>90%) than with headache relief (~50%). Long-term results are lacking. however.

In this case, cerebral angiography demonstrated bilateral high-grade transverse/sigmoid sinus stenoses distal to vein of Labbe insertions. Selective catheterization of the right transverse sinus revealed an estimated 80% narrowing to a luminal diameter of 1mm, and a pressure gradient across the stenosis of 13 mmHg (normal <5 mmHg). The contralateral sinus was smaller, but distally stenotic. A stent was placed across the right sided stenosis.
The patient was placed on antiplatelet medication to preserve stent patency immediately after the procedure. She had no headaches after the procedure and demonstrated objective visual improvement at her one- and six-week follow-up examinations.

Intracranial pseudotumor (Tolosa-Hunt syndrome)

2010-12-22T16:00:00.001+01:00

Findings

Increased CSF signal demonstrated by T2 hyper intensity within the right optic sheath. Nodular enhancement at the superior aspect of the right optic nerve at the orbital apex, which extends with prominent nodular enhancement posteriorly along the dural reflection of the right cavernous sinus. Asymmetric dilatation of the right superior ophthalmic vein.

Differential diagnosis:
- Meningitis
- Sarcoidosis
- En plaque meningioma
- Meningeal metastases
- Meningeal Non-Hodgkin's lymphoma
- Tolosa-Hunt syndrome

Diagnosis: Intracranial pseudotumor (Tolosa-Hunt syndrome)

Discussion

Intracranial pseudotumor (Tolosa-Hunt syndrome) is a part of a spectrum of "quasineoplastic" lesions that demonstrate orbital, intracranial, or pulmonary involvement, and include such other disorders as plasma cell granuloma and hypertrophic cranial pachymeningitis. It is a chronic granulomatous disease of unknown origin, which has been hypothesized to represent a low grade fibrosarcoma of inflammatory cells versus an autoimmune phenomenon. While Tolosa-Hunt syndrome is rare, orbital pseudotumor is the third most common ophthalmic disorder, and encompasses 5-8% of all orbital masses. Histologically, the lesions of Tolosa-Hunt demonstrate mixed lymphocytic and plasma cell infiltrate, with a variable degree of fibrosis. Lesions favor the cavernous sinus and basal meninges, although falcine and tentorial lesions have been described.

Patients with intracranial lesions are more frequently young adults, who present initially with chronic headaches or cranial nerve palsies. Patients with orbital involvement are more frequently middle-aged, and may present with painful proptosis and vision loss . Symptoms may be intractable, leading to severe disability. Untreated or unresponsive disease may progress to death. First-line treatment is invariably high-dose steroids, with radiotherapy or surgical resection reserved for patients with incomplete response to steroids .

Radiologic Overview of the diagnosis

The imaging hallmarks of Tolosa-Hunt syndrome are characterized by an enhancing, infiltrating meningeal mass, which favors the cavernous sinus or basal meninges, although falcine and tentorial involvement has been described . Focal meningeal thickening may range from just a few millimeters to a greater than 2 cm rind. With intracranial pseudotumor, orbital involvement is spared more than 90% of the time. Tolosa-Hunt remains a diagnosis of exclusion, once meningitis, en plaque meningioma, and meningeal metastases are ruled out.

The imaging modality of choice for imaging patients with Tolosa-Hunt remains MRI, although useful information may be gleaned from other modalities. On non-contrast enhanced CT (NECT), there are no specific findings to suggest the diagnosis; however, this modality may be of some value in differentiating the lesion from en plaque meningioma. On contrast enhanced CT (CECT), salient imaging findings include enhancing, thickened meninges or a curvilinear appearance of a single meningeal region. As aforementioned, MRI remains the primary modality for diagnosis of Tolosa-Hunt syndrome, and each sequence may provide critical information required to make the diagnosis. On T1WI, one may find focal thickening of the meninges that is isointense to gray matter. On T2WI, lesions are characterized as iso- to hypo intense regions of focal meningeal thickening, which may be more hypo intense as they become more fibrotic. FLAIR is of little help in making the diagnosis, but it is unlikely to demonstrate focal brain edema underlying the lesion . Contrast enhanced T1WI is the single most valuable sequence for evaluation of Tolosa-Hunt syndrome, and is characterized by diffusely enhancing region of meningeal thickening, which may range from a few millimeters to greater than 2 cm in some cases. Diffuse boney infiltrates may be appreciated on fat saturated contrast enhanced T1 sequence. While angiography is not considered a primary modality, severe disease may result in carotid artery narrowing, thus MRA may be a useful adjunct in the appropriate clinical setting.

The appropriate differential diagnosis of Tolosa-Hunt syndrome includes meningitis, sarcoidosis, en plaque meningioma, meningeal metastases, and meningeal Non-Hodgkin's lymphoma.

Hypertensive intracranial hemorrhage

2010-12-17T16:00:00.002+01:00

Findings

Axial CT of the head shows a large hyper dense focus with peripheral hypo density in the left frontal lobe, causing sulcal effacement at the frontal cortex but no significant midline shift. Surrounding rim of low density represents edema (image 1). Unenhanced MRI of the brain shows an the same mass-like focus in the left frontal lobe, which has an isointense center with a hyper intense rim (image 2). Post gadolinium-enhanced T1 image of the brain shows no internal enhancement of this lesion (image 3).

Differential diagnosis:
- Hypertensive intracranial hemorrhage
- Ruptured arteriovenous malformation (AVM)
- Hemorrhagic intracranial mass
- Posttraumatic cerebral contusion

Diagnosis: Hypertensive intracranial hemorrhage

Acute blood appears hyper dense of unenhanced head CT.
Without a history of trauma, intraparenchymal brain hemorrhage on head CT could represent a hemorrhagic mass, a ruptured AVM, or a hemorrhagic brain tumor (primary or metastatic).
MRI with and without contrast is the best diagnostic tool for determining if a mass lesion is present, and for evaluating the age of the intracranial hemorrhage.
Acute blood products on T1 appear hypo intense to isointense (image 2), whereas subacute and chronic hematoma are hyper intense.
Neoplasms should enhance on post contrast T1. The lack of enhancement in this patient on post contrast T1 excludes neoplasm (image 3).

Sequestered disk

2010-12-16T16:00:00.000+01:00

Findings

There is an non- enhancing ovoid mass slightly hyper intense to muscle on both T1 and T2 sequences, in the anterior epidural space at the L3 level, measuring approximatelyl 12 x 8 x 12 mm. This is not contiguous with any adjacent disks. No signal dropout on fat-saturated sequences. The mass causes severe stenosis of the left half of the spinal canal at the L3 level, compressing the left descending nerve roots. T1 and T2 hyper intensity at the endplates abutting L2-L3 disc space representing Modic Type II changes. There is intervertebral disk space height loss at L2-L3 with severe disk desiccation changes.

Differential diagnosis:
- Sequestered disk
- Extruded disk
- Failed back surgery
- Epidermoid
- Epidural abscess
- Epidural hematoma
- Lipoma

Diagnosis: Sequestered disk

A focal disk protrusion is an extension of intervertebral disc material (nucleus pulposus) beyond the vertebral margin (AP diameter < mediolateral diameter). An extruded disk is one in which the nucleus pulposus has herniated through a rent in the annulus fibrosis. The AP diameter > ML diameter, and the disk may migrate craniocaudally, but maintains attachment to the parent disk (frequently symptomatic).
When extruded disk material loses its attachment to the parent disk, it is referred to as a sequestered disk. Sequestered discs usually lodge in the anterior epidural space (AES), just anterior to the posterior longitudinal ligament, and migrate either cephalad or caudad (with equal frequency). Because there is a midline septum associated with the PLL in the AES, the fragment is usually just off midline (to the right or left). Rarely, the sequestered fragment may migrate beyond the PLL into the posterior epidural space, through the dural ( intrathecal location), or into the paraspinal muscles.
They usually resemble the parent disk on MR, with T1 hypo intense and T2 iso- / hypo intense. There may be surrounding T2 hyper intensity and a rim of enhancement from inflammatory changes.
This is a crucial diagnosis to make, as a sequestered disk is a contraindication to limited disk procedures (e.g. Percutaneous discectomy) and may result in failed back surgery.

Myxopapillary ependymoma

2010-12-14T16:00:00.002+01:00

Findings

Figure 1: Sagittal T1-weighted images reveals an isointense lobulated intradural mass at the level of the conus medullaris.
Figure 2: Sagittal T2-weighted images shows a hyperintense lobulated intradural mass extending from T11 through L2 with numerous small flow voids.
Figure 3: Sagittal T1 post-contrast images demonstrates intense enhancement of the intradural mass centered around the conus.

Diagnosis: Myxopapillary ependymoma

Myxopapillary ependymoma is a slow-growing tumor arising from the ependymal cells of the filum terminale. These tumors compromise 13% of all spinal ependymomas, and they occur almost exclusively in the conus, filum terminale, and cauda equina although extradural occurence in the sacrum and presacral region has also been reported.

The lesions tend to span two to four vertebral segments, and appear as a well-circumscribed intradural masses. In most cases the tumor is intrinsic to the conus medullaris but this is often difficult to recognize on imaging as the bulk of the mass is extramedullary. Typical MR characteristics include T1 isointensity, T2 hyperintensity, and avid enhancement on post-contrast images. As these tumors are prone to hemorrhage, a hypointensity at the tumor margin is often seen indicative of hemosiderin. Calcification and cyst formation within the mass are not infrequent.

On radiography and CT, vertebral changes can be seen which include widened interpediculate distance, thinned pedicles, posterior vertebral scalloping, and intervertebral foraminal widening due to tumor extension.

They are more common in males (M:F=2:1) with a mean age of 35 at diagnosis. Clinically, they present with back pain, paraparesis, radiculopathy, and occasionally bowel and bladder dysfunction. Because these symptoms can mimic those of disc herniation, there is often a delay in diagnosis. Treatment consists of surgical resection, and the prognosis is excellent with complete resection. Leptomeningeal seeding metastasis in myxopapillary variety is not as frequent as it is in classic spinal cord ependymomas and associated with poorer prognosis when present. Radiotheraphy after surgery improves outcome.

Capillary Telangiectasia

2010-12-10T16:00:00.003+01:00

Findings

There is an ill-defined enhancing focus in the medial right temporal lobe on post gadolinium contrast T1-weighted imaging (Figure 4). There is no corresponding signal abnormality or mass on the precontrast T1-weighted, T2-weighted, or FLAIR images (Figure 1, Figure 2, and Figure 3, respectively). There is no mass effect. On susceptibility-weighted imaging (SWI) the lesion shows hypointensity (Figure 5).

Diagnosis: Capillary Telangiectasia

Brain capillary telangiectasias are benign vascular malformations which are often found incidentally.
They can be visualized by gadolinium contrast and gradient-echo susceptibility or susceptibility weighted imaging, but not through catheter angiography, and may often not be visible on conventional T1/T2, FLAIR, or diffusion-weighted imaging.
Often asymptomatic and usually no treatment is required.

Brain capillary telangiectasias (BCTs) are one of four major types of vascular malformations which occur in the brain (the other three are arteriovenous malformations, cavernous malformations (cavernous angiomas), and developmental venous anomalies (venous angiomas), and represent up to 20% of all intracranial vascular lesions. BCTs consist of multiple ectatic capillaries surrounded by normal brain parenchyma and are usually devoid of calcification, gliosis, extraluminal hemorrhage, and hemosiderin-laden macrophages. BCTs are most common in the midbrain, pons, medulla, and spinal cord, but they are found throughout the central nervous system. Multiple BCTs are possible, especially in certain syndromes (e.g.; ataxia telangiectasia, Osler-Weber-Rendu, or Sturge-Weber syndrome).

Often found incidentally, BCTs are usually benign, small in size, and rarely grow over time. They are rarely symptomatic and are not associated with any particular clinical feature but have been reported to be associated with headache, vertigo, and tinnitus.

BCTs are relatively well visualized through susceptibility weighted imaging where they demonstrate marked signal intensity loss due to deoxyhemoglobin present in slow flowing blood. They are also well visualized through gadolinium-enhanced T1-weighted imaging sequences where they are seen as small faint lesions. BCTs are difficult to visualize through conventional T1/T2, FLAIR, or diffusion-weighted imaging and are considered to be one of the “angiographically occult vascular malformations” due to their small size, tendency to occlude, and sluggish flow.

Wernicke’s Encephalopathy

2010-12-10T16:00:00.001+01:00

Findings

On axial images, abnormal FLAIR signal is demonstrated at the pontomedullary junction adjoining the fourth ventricle, periaqueductal gray matter in the pons and midbrain (Figure 1), the superior aspect of the mamillary bodies (Figure 2), the tissue surrounding the third ventricle and the medial thalami (Figure 3).
On coronal slices, abnormal FLAIR signal again appears in the mamillary bodies (Figure 8), in the tissue surrounding the third ventricle (Figure 8 and Figure 10), medial thalami (Figure 10), and periaqueductal gray matter (Figure 11).

Diagnosis: Wernicke’s Encephalopathy

Wernicke’s encephalopathy is caused by thiamine deficiency, most often seen in chronic alcohol abuse. It has also been described in anorexia nervosa, prolonged starvation, hyperemesis gravidarum, patients on long-term hemodialysis, and patients with AIDS. Patients with this condition classically present with the triad of ataxia, acute mental confusion, and oculomotor dysfunction, although a minority (16-38%) of patients with the condition present with all three elements. If the symptoms also include amnesia and confabulation, then these manifestations are called Korsakoff syndrome. Wernicke’s encephalopathy is a significantly disabling and potentially lethal condition that can be prevented and reversed if treated early with thiamine supplementation.

On CT and MR imaging the brain demonstrates diffuse cerebral and cerebellar atrophy. Mamillary body enhancement or abnormal T2 signal may be the sole manifestation of Wernicke’s encephalopathy. Other typical MR findings include symmetric high T2 signal and variable enhancement within the periaqueductal gray matter of the midbrain, the tectal plate, the mamillothalamic tract, the thalami, and the tissue surrounding the third ventricle. The mamillary bodies may also show atrophy in patients with chronic Wernicke’s encephalopathy, though this finding can also be present in chronic alcoholic patients without Wernicke’s syndrome. Atypical changes may also be seen, almost always in non-alcoholic patients, and may include signal changes in cranial nerve nuclei, basal ganglia, cerebellum and dentate nuclei, the splenium, and frontal and parietal cortex. These atypical findings are very similar to the pattern seen in metronidazole-induced encephalopathy, and it is has been hypothesized that the two syndromes share a common metabolic pathway. The reason why these brain regions are more affected by thiamine deficiency is poorly understood, but it is speculated that they may be characterized by more intense thiamine metabolism.

Methotrexate neurotoxicity

2010-12-07T16:00:00.004+01:00

Additional clinical history: Patient was diagnosed with acute lymphocytic leukemia 2 months previously. He is status post induction therapy with a negative bone marrow biopsy, and is currently receiving consolidation chemotherapy with methotrexate, and presents with right upper extremity weakness.

Findings

MR images of the brain demonstrate a focal area of diffusion restriction involving the left frontoparietal white matter. There is minimal associated T2/FLAIR hyperintensity. No associated enhancement. Remainder of the brain was within normal limits.
Imaging done four months later shows lesion has nearly resolved.

Diagnosis: Methotrexate neurotoxicity

Discussion

Methotrexate is a folic acid analogue. Its cytotoxic effects are carried out through inhibition of the enzyme dihydrofolate reductase, which reduces tetrahydrofolic acid levels, ultimately inhibiting cell division.

From bone marrow cell precursors to the quickly dividing cells of the intestinal tract, methotrexate exerts its effects on all dividing cells in the body. One of its rare side effects is CNS toxicity. The decreased folate levels achieved with methotrexate have implications on metabolism of adenosine, homocysteine, and biopterin. Low folate levels lead to a subsequent decrease in S-adenosyl-methionine(SAM) concentrations. This eventually leads to chronic demyelination and neurologic symptoms.

An additional side effect of MTX is the elevated levels of adenosine in the CSF. Adenosine is a vasodilator, which causes dilatation of cerebral vasculature resulting in neurotoxicity. The increased homocysteine levels caused by MTX have been shown to damage vascular endothelium and lead to subsequent strokes and thromboemboli. Methotrexate has also been found to cause cytotoxic edema, which is the most common cause of lesions that enhance on MRI DWI.

The neurotoxicity caused by MTX can be immediate, acute to subacute, or delayed. Symptoms of the disease can range from headache, nausea, vomiting, and fever, to transient or permanent focal neurologic symptoms. The immediate form occurs within a day of MTX administration and presents as a chemical meningitis. The acute to subacute form presents from days to weeks after administration of MTX, and presents with seizures or focal neurologic symptoms. The delayed form presents as leukoencephalopathy and a generalized decrease in higher cognitive function.

Radiological findings

A case series containing nine cases of MTX neurotoxicity revealed that lesions found in this disease tend to be focal and show up on DWI as well as T2 and FLAIR imaging. These abnormalities can continue to persist on imaging long after the symptoms have resolved. The DWI shows diffusion restriction with T2/FLAIR hyperintensity being less conspicuous.

In another independent case study on MTX neurotoxicity, MRI demonstrated restriction diffusion with no significant T2 or FLAIR signal abnormality. Based on a combination of these imaging findings, it was determined that cytotoxic edema was likely the cause of focal neurologic symptoms on the patient, and demyelination was a less likely cause based on the MRI findings.

A different case study had MRI findings showing subtle signal changes in the left centrum semiovale, with an obviously abnormal area of restricted diffusion, indicating the presence of increased fluid. The authors of this case also mentioned a relation between elevated choline levels in lesion areas with myelin breakdown.

The lesion in this disease is similar in appearance to ischemic stroke, but differs in distribution. The lesions in MTX neurotoxicity can show up in many different patterns, whereas ischemic strokes often follow a vascular distribution, helping differentiate the two.

Radiology

MRI:
MRI with DWI is the gold standard for diagnosis
Will show focal areas of demyelination and/or edema throughout the brain
Can be normal, even in the presence of symptoms
Must perform early to avoid unnecessary workup

CT:
Can be used to rule out other etiologies that may cause focal symptoms, but is not a sensitive test for demyelination and edema found with MTX neurotoxicity
Ultimately need MRI to make diagnosis as CT is often negative
Angiography
Not very useful as it is usually normal

Basilar invagination secondary to rheumatoid arthritis

2010-12-03T16:00:00.001+01:00

Findings

Axial and sagittal CT images demonstrate severe basilar invagination (Figure 1). The tip of the odontoid process measures 2.3 cm above Chamberlain’s line (yellow line in Figure 2). McGregor's line (red line in Figure 2) is also shown. Incidentally noted are right-sided opacified mastoid air cells (Figure 1).
Once again, severe basilar invagination is evident. On the sagittal T2 image the foramen magnum is narrowed and obliteration of the CSF space is noted at the C2-C3 level (Figure 3). On the axial T2 weighted image increased T2 signal (Figure 4) is seen within the cord at the C2-C3 level indicating edema versus myelomalacia.

Diagnosis: Basilar invagination (impression) secondary to rheumatoid arthritis.

Basilar invagination refers to a condition in which the odontoid process protrudes upward into the intracranial space. Basilar invagination may be classified as primary (congenital) or secondary (acquired). Down syndrome, Klippel-Feil syndrome and Chiari malformations are congenital causes of basilar invagination. Acquired basilar invagination, also known as basilar impression, is associated with softening of the skull base and is often due to rheumatoid arthritis, Paget disease, osteomalacia, hyperparathyroidism and osteogenesis imperfecta. Basilar invagination is probably better described as a radiologic finding rather than a diagnosis. Once the finding is identified, a cause of basilar invagination should be diligently pursued.

Plain lateral radiographs with odontoid views, although not 100% sensitive, are often the initial study used to diagnose basilar invagination. MRI is the optimal study, which also assesses the cervicomedullary junction and cervical cord. Two craniovertebral junction lines are particularly useful in defining basilar invagination. Chamberlain’s line extends between the posterior pole of the hard palate and the posterior edge of the foramen magnum (opisthion). If the dens is >3.0 mm above this line basilar invagination is present. McGregor’s line, a modification of Chamberlain’s line was developed because the opisthion could not always be seen on plain radiographs. This line extends from the posterior pole of the hard palate to the undersurface of the occiput. If the dens extends >4.5 mm above this line basilar invagination is present.

Clinical manifestations of basilar invagination include posterior skull pain, headache, signs and symptoms of brainstem and upper cervical cord compression or disturbances of CSF circulation causing obstructive hydrocephalus. The brainstem may be compressed at the level of the foramen magnum possibly resulting in compromise of the autonomic centers resulting in labile blood pressures, arrhythmias, or sudden death. Neurosurgery is recommended in patients that are symptomatic with concomitant MRI findings indicating compression. Although asymptomatic patients are often followed conservatively, many authors favor surgery even if no symptoms of cord compression are evident in rheumatoid patients.

Although often appearing together, basilar invagination or impression should not be confused with platybasia; which literally means “flattening of the base of the skull”. Platybasia, which can be seen in Klippel-Feil anomalies, cleidocranial dysplasia and achondroplasia, is present when the basal angle formed by intersecting lines from the nasion to the tuberculum sellae and from the tuberculum along the clivus to the anterior aspect of the foramen magnum (basion) is greater than 143 degrees.

Intraventricular oligodendroglioma

2010-11-29T16:00:00.001+01:00

Findings:

Figure 1: Non-contrast CT shows a large rounded mass in the lateral ventricles with intermediate density and large foci of calcification within it. This is causing significant hydrocephalus with enlargement of the third ventricle.

Intraventricular oligodendroglioma

Oligodentrogliomas are well differentiated, slowly growing but diffusely infiltrating cortical and subcortical tumors. Although most of them involve the frontal and frontotemporal cortex, a small proportion of them are seen in the ventricular walls (1-10%), cerebellum and exceedingly rarely within the brainstem, spinal cord and leptomeninges. No age is exempt and the peak incidence is in the 4th or 5th decades. It usually have a long standing history of symptoms and the most common being seizures and headaches.

Intraventricular oligodentrogliomas can present with hydrocephalus. Pathologically, they are well defined, grayish-pink soft unencapsulated mass and calcification is extremely common. Focal cystic degeneration and hemorrhage are frequent findings. CSF seeding is uncommon. Histopathologically, these are moderately cellular tumors with occasional mitosis. Perinuclear halos or the "fried egg artifact" is a distinctive feature of oligodentroglioma. Majority of the "intraventricular oligodentrogliomas" described in the literature are central neurocytomas and immunohistochemistry helps to distinguish them.

On CT, oligodentrogliomas usually have mixed density with nodular, clumped or linear tumoral calcification seen in majority (50-90%). Cystic degeneration is common. Intratumoral hemorrhage and edema is uncommon. The hemispheric lesions may expand, remodel or erode the calvarium. Enhancement is variable. On MR, oligodentrogliomas are typically heterogeneously hypointense or isointense to grey matter on T1 and heterogeneously hyperintense on T2 and FLAIR due to calcification, cystic change and hemorrhage. Nearly 50% show heterogeneous enhancement following contrast administration. Areas of calcification and hemorrhage demonstrate "blooming" on gradient echo MR sequences. No diffusion restriction on DWI.

Surgical resection is the primary treatment of choice. Radiation therapy and chemotherapy is reserved for recurrent tumors. Local recurrence is common and hence regular surveillance is recommended.

Ewing sarcoma of the occipital bone

2010-11-26T16:00:00.001+01:00

Findings

Figure 1: Unenhanced CT shows a heterogeneous attenuation mass with cystic spaces in the posterior fossa.
Figure 2: Intense enhancement is noted after contrast administration.
Figure 3: Bone window section showing permeative destruction of the left occipital bone.
Figure 4: Axial T1 weighted image showing extra- axial mass with multiple cystic spaces.
Figure 5: Coronal T2 image showing the extra-axial origin clearly with mass effect on the cerebellum. The cystic spaces appear hyperintense.
Figure 6: Axial T1 weighted image showing intense enhancement of the mass.

Diagnosis: Ewing sarcoma of the occipital bone

Ewing sarcoma is a small round-cell tumor arising from mesenchymal cells. These tumors affect children and young adults in the age group of 5-15 years. The long bones, flat bones like the scapula and the vertebrae are the most common sites. Primary Ewing sarcoma affecting the calvarium is extremely rare, making just 1% of the cases. In the skull, the tumor more often arises from the frontal and parietal bones and less common locations include ethmoid, temporal and occipital bones.

CT scans (bone window) reveal poorly marginated permeative destructive lesion involving both inner and outer tables of the skull. The "onion peel" appearance typical of Ewing sarcoma in long bones is not seen commonly in the calvarium. The extra-dural soft tissue shows intense enhancement on contrast administration.

MR imaging provides better soft tissue delineation of these tumors. The extra dural soft tissue appears hypointense on T1 weighted images while the cystic and necrotic areas appear hyperintense on T2 weighted images. Good contrast enhancement is noted.
The differential diagnosis should include rhabdomyosarcoma, metastatic neuroblastoma and lymphomas.

Treatment is surgery followed by chemotherapy and radiation.

Suprasellar arachnoid cyst

2010-11-22T16:00:00.002+01:00

Findings:

Figure 1, Figure 2 and Figure 3 show severe hydrocephalus involving the lateral and third ventricles.
Figure 4, Figure 5, Figure 6, show a suprasellar mass lesion which follows CSF signal on all sequences, including FLAIR.

Diagnosis: Suprasellar arachnoid cyst

Arachnoid cyst is the most common congenital lesion of the brain. It is typically an incidental imaging finding and is rarely symptomatic. However, in this case the size and location of the lesion in the suprasellar cistern resulted in severe obstructive hydrocephalus and precocious puberty. Both of these complications resolved following surgical drainage of the cyst.

Arachnoid cysts arise from a splitting of the arachnoid membrane with formation of a cyst wall consisting of fibrous connective tissue. There is no epithelial lining in the wall. Expansion occurs following trapping of cerebral spinal fluid through defects in the cyst wall. Arachnoid cysts occur most commonly in the middle cranial fossa and have a 4-to-1 male-to-female ratio. Even large cysts tend to be asymptomatic. Associated clinical features in symptomatic patients include headache, calvarial bulging, intracranial hypertension, craniomegaly, developmental delay, visual loss, precocious puberty, and seizures. Treatment of arachnoid cysts is not recommended by many unless there is a clear cause and effect relationship between the cyst and symptoms as shown in this case.

MRI is the preferred diagnostic modality for arachnoid cysts because of its ability to demonstrate the location, extent and relationship of the cyst to surrounding neurologic structures. Lesions typically have the signal intensity of CSF on all sequences, do not enhance and do not demonstrate restricted diffusion. The most important differential diagnostic consideration is between arachnoid and epidermoid cysts. Epidermoid cysts show restricted diffusion on diffusion-weighted images. In addition, unlike epidermoid cysts, arachnoid cysts show suppressed signal on fluid-attenuated inversion recovery (FLAIR) images.

Malignant melanoma of the uvea

2010-11-19T16:00:00.000+01:00

Findings

Thin section axial fat-suppressed fast spin-echo T2-weighted imaging
Figure 1 and Figure 2 show a V-shaped retinal detachment pointing toward the optic nerve. There is increased T1 signal posterior to the detachment suggesting hemorrhage.

Thin section axial fat-suppressed T1-weighted imaging
Figure 3 and Figure 4 show a mass arising from the nasal aspect of the right ocular globe. There is a collar button configuration to this mass, which assumes the typical configuration strongly suggesting elevation of Bruch’s membrane. The mass is near isointense to muscle on precontrast T1 and T2 weighted images. This mass extends towards the vitreous but no extension beyond the sclera is identified.

Postcontrast fat-suppressed T1-weighted imaging
Figure 5 and Figure 6: The mass is near isointense to muscle on pre-contrast T1 and T2 weighted images and demonstrates prominent contrast enhancement.

Diagnosis: Malignant melanoma of the uvea

Uveal melanoma is the most frequent primary intraocular malignant tumor in adults. It is rare in children. Its importance is that it is the main intraocular disease that can be fatal in adults.
Uveal melanoma can erupt through Bruch's Membrane. When this occurs, they develop a characteristic collar button configuration that extends through the vitreous chamber.
Uveal melanomas have differing MR characteristics, depending on the amount of melanin, which has paramagnetic properties. Melanomas containing a lot of melanin will demonstrate T1 hyperintensity, and markedly decreased T2 signal. However, in amelanotic or slightly melanotic melanomas, the typical MR pattern is isointense on T1, and slightly hypointense on T2.

Uveal melanoma is the most frequent form of intraocular malignancy in adulthood (4). As the uvea is the most vascular region of the globe, it is a common site for primary and metastatic neoplasm. Uveal melanomas comprise 70% of malignant intraocular tumors. It affects approximately 5-7 out of 1,000,000 people (3). Uveal melanoma can occur in any of the three subdivisions of the uvea: the iris, ciliary body, and choroid.

Uveal melanomas start with a flat growth profile along the choroid. With progression, they become elevated, and frequently extend through Bruch's membrane, where they can track into the subretinal space. With spread through Bruch's membrane, the melanoma can have a "mushroom shape" or "collar button" appearance that extends through the vitreous chamber.

Uveal melanomas typically appear as a solid, well-defined mass on magnetic resonance imaging. Melanin is paramagnetic, so in melanomas containing a lot of melanin, there is increased T1 signal with markedly decreased T2 signal. This signal intensity pattern is pathognomonic for uveal melanoma, as there are no other intraocular lesions with this appearance. In low-melanin or amelanotic melanomas, Magnetic Resonance imaging is less specific, but typically shows isointense signal on T1-weight images and slightly hypointense signal on T2-weighted images. Uveal melanomas typically have moderate to strong contrast enhancement following administration of gadolinium.

B-mode ultrasound typically shows a rounded, hypoechoic, highly vascular lesion. Retinal elevation and vitreous hemorrhage can also be seen, as these are complications of uveal melanomas. Uveal melanomas on unenhanced computed tomography appear sharply marginated, hyperattenuating, and elevated.

Uveal melanomas also have a propensity to metastasize hematogenously, and do so most frequently to the liver. Uveal melanoma is the most common fatal intraocular disease in the adult population.

Optimal treatment for uveal melanomas is controversial and clinical trials are ongoing. Large melanomas, typically greater than 10-mm in thickness, are usually managed with enucleation. For medium sized melanomas, 3-mm to 10-mm thick, plaque brachytherapy and external-beam radiation therapy have been accepted as alternatives to enucleation. For small lesions, less than 3-mm, routine monitoring with ultrasound is recommended as these may represent benign choroid nevi. These small lesions may also be biopsied, with a positive result placing the small melanomas into the medium melanoma treatment category.

Prognosis is dependent on many factors. Increasing tumor pigmentation is associated with a less favorable prognosis. Additionally, increasing size, infiltration through Bruch's membrane, and retinal detachment are all associated with a poorer prognosis. In metastatic disease to the liver, the mean survival has been reported to be nine months.

Internal Carotid Artery Dissection

2010-11-15T16:00:00.000+01:00

Findings

CT: Multifocal areas of hypoattenuation in the right frontal lobe which are confirmed acute infarctions on MRI with diffusion weighted imaging.
MRI: Axial MRI DWI and matching ADC maps demonstrate multifocal areas of true restricted diffusion in the right frontal lobe indicating acute infarctions from thromboemboli secondary to more proximal right internal carotid artery dissection.
CTA: Sequential Axial Neck CTA images from caudal to rostral demonstrate tapering to occlusion of the right internal carotid artery just distal to the Right common carotid artery bifurcation.
CTA neck exam frontal, oblique, and Sagittal 3D volume rendered and Sagittal MIP images demonstrate ‘flame shaped’ tapering to occlusion of the cervical right internal carotid artery just distal to the common carotid artery bifurcation, typical of dissection.

Diagnosis: Internal Carotid Artery Dissection

Carotid and vertebral artery dissection should be considered among the etiologies of brain infarct, particularly in young patients.
Symptoms typically include neck and face pain, headache, acute onset Horner’s syndrome, and ischemic symptoms that may occur initially or days to weeks after dissection.
Primarily treated with anticoagulation and aspirin.

Spontaneous carotid dissection can occur at any age but is most frequently seen in the fifth decade of life. The most common location for dissection of the internal carotid artery is the proximal extracranial segment. While brain infarct is the most feared complication, some carotid dissections may be asymptomatic from a neurologic standpoint.

Once thought to be a rare occurrence, spontaneous dissection of the internal carotid artery has become increasingly recognized as a cause of anterior circulation infarction, largely due to the advent of MR angiography. Predisposing factors include hypertension, Ehlers-Danlos disease, Marfan syndrome, fibromuscular dysplasia, migraine, oral contraceptives, and pharyngeal infections although most carotid dissections are seen in completely healthy individuals. A history of minor trauma is often elicited. The most studied association is chiropractic spinal manipulation, but carotid dissection has been described in various other minor traumas such as: yoga, ceiling painting, nose blowing, judo, coughing, sneezing, vomiting, and even ventilation associated with resuscitation or anesthesia. Blunt or penetrating major trauma to the head and neck is also a well-recognized cause of carotid dissection.

The underlying abnormality in spontaneous carotid artery dissection is thought to be an expanding hematoma within the vessel wall and, as a result, on CT angiogram an intimal flap is not always seen (unlike aortic artery dissection where contrast commonly tracks into the false lumen). Patients with carotid artery dissection can present with headaches, neck pain, acute onset Horner’s syndrome, or transient ischemic attack (TIA’s) and stroke (as in our case example). The dreaded complication of vascular dissection is thromboembolic phenomenon that may occur days to weeks after the dissection.

Imaging findings in carotid artery dissection include a tapered narrowing and occlusion of the vessel, as seen on current CTA exams with MIP images and 3D rendering. A hyperintense intramural hematoma may sometimes be seen on noncontrast axial T1 weighted imaging with fat-saturation, when blood products are in the subacute phase, representing methemoglobin. On occasion, it may also be termed the “crescent sign” because of its morphology. Signs of anterior circulation infarction can be seen on CT and MR at the time of initial presentation (as in our case).

Treatment in uncomplicated cases usually includes anticoagulation therapy and aspirin. It is important to obtain follow up MR imaging in these patients to assess for recanalization of the vascular lumen or progressive stenosis. These patients are also more prone to development of pseudoaneurysms.

Idiopathic Thoracic Cord Herniation

2010-11-12T16:00:00.000+01:00

Findings

These MR images demonstrate focal anterior displacement of the spinal in the mid thoracic spine. The cord (Images 1,2 and 3) appears to be either tethered anteriorly or compressed from the posterior aspect. The intradural space behind the cord is widened and has signal characteristics identical to CSF (Images 1,2 and 3).

Diagnosis: Idiopathic Thoracic Cord Herniation

Spinal cord herniation occurs when the cord herniates through a defect in the dura mater. These dural defects are typically located anteriorly or laterally, and occur most often in the mid-thoracic region. They may be idiopathic, post-traumatic or iatrogenic related to prior spinal surgery. Some have suggested that a herniated and calcified disk may cause thinning, erosion, or rupture of the dura, which may also be secondary to congenital weakening of the ventral dural fibers. The presence of free flow of cerebral spinal fluid dorsal to the herniated cord is key to differentiating a spinal cord herniation from an arachnoid cyst. Spinal cord herniation occurs most commonly in the middle-aged. Symptoms of myelopathy including chronic leg pain, gait disturbance, incontinence, and leg weakness are commonly seen and may slowly worsen over time if left untreated. The most common clinical feature reported is the Brown-Séquard syndrome consisting of hemiplegia and contralateral temperature sensation deficits and pain.

Typical imaging findings are focal anterior displacement of the spinal cord with expansion of the dorsal subarachnoid space. The preferred imaging modality in the setting of myelopathy is MRI, which is often sufficient for making the correct diagnosis. Myelography with CT may be required in ambiguous cases and to demonstrate the exact location of the dural defect. With cord herniation, myelography reveals uninterrupted flow of contrast and the absence of a filling defect posterior to the herniated cord segment. An arachnoid cyst will present during myelography as an early filling defect posterior to the displaced cord. Contrast may fill the cyst with time, so rapid acquisition of CT-myelograpgy after the initial myelographic images is essential. Phase contrast cine MR imaging may provide similar CSF flow information, in addition to restricted cord motion.

Treatment consists of surgically reducing the herniation by repositioning the protruding spinal cord back into the thecal sac followed by the repair of the defect in the dural mater in order to prevent recurring herniation. After surgery, symptoms typically improve and may completely resolve, even when longstanding. Patients whose symptoms are milder and non-progressive may be eligible for less invasive therapy or conservative management with monitoring.

Methotrexate (MTX) induced transient neurotoxicity

2010-11-10T16:00:00.001+01:00

14-year-old child with history of Acute Lymphoblastic Leukemia (ALL), on induction chemotherapy complaining of left sided weakness and facial asymmetry of acute onset.

The patient was given supportive treatment and aminophylline, symptoms resolved and an MRI was repeated after 3 days.

Findings

Diffusion weighted images with corresponding ADC maps show restricted diffusion involving bilateral centrum semiovale (Figure 1 and Figure 2).
Diffusion weighted images with corresponding ADC maps, from the MRI done after clinical improvement, show resolution of abnormalities seen on DW and ADC Maps in the initial study (Figure 3 and Figure 4).

Diagnosis: Methotrexate (MTX) induced transient neurotoxicity

With improvements in antileukemic treatment there has been a steady increase in long term survivors of ALL. However a myriad of neurological complications are seen during and after treatment. These maybe broadly categorized into those related to chemotherapeutic agents, radiation therapy, coagulopathy, immunosuppression and marrow transplantation.

Methotrexate is an essential component of treatment regimens in ALL. It can be administered both intravenously and intrathecally. Though hematologic and mucocutaneous consequences are more common, the CNS adverse effects are more worrisome. Chronic leukoencephalopathy as a result of methotrexate and radiotherapy is a well recognized complication and usuallly associated with cognitive deficits rather than focal neurologic deficits although subacuteacute encephalopathy after methotrexate may occur as well and usually presents as headache, confusion, disorientation, seizure, and focal neurologic deficit. A vast majority of patients show hemiparesis and aphasia.

High level of adenosine is thought to be responsible for methotrexate induced toxicity. Statistically the periventricular white matter is the most common area affected. On diffusion weighted imaging these areas show increased signal intensity and hypointensity on corresponding apparent diffusion coefficient (ADC) maps. There may be no abnormality identified on T1, T2, and FLAIR sequences during the acute symptomatic phase.

Clinical resolution is followed by the appearance of residual FLAIR hyperintensities in the involved areas, which show gradual regression. There is no established treatment, however several anecdotes report symptomatic resolution with aminophylline therapy.

Neuroblastoma metastases

2010-11-08T16:00:00.000+01:00

Findings

Figure 1: Axial post gadolinium T1 weighted image showing solid enhancing parenchymal lesion in the right temporal lobe with dural and leptomeningeal disease.
Figure 2: Coronal post gadolinium image showing dural enhancement along the tentorium and leptomeningeal enhancement.
Figure 3: Axial susceptibility weighted imaging revealing the hemorrhagic nature of the lesion.

Diagnosis: Neuroblastoma metastases

Neuroblastoma metastatic to the central nervous system is extremely rare, and the reported incidence varies from 1% to 16% at recurrence. Paediatric tumors that metastasise to the brain, in order of frequency, include neuroblastoma, osteosarcoma, Ewing sarcoma, rhabdomyosarcoma and Wilm tumor.

Risk factors for developing intracranial metastases include lumbar puncture at diagnosis, ages 2 to 3 years, bone marrow involvement, and MYCN gene amplification. Newer chemotherapeutic agents with better activity fail to penetrate the blood-brain barrier, thus facilitating a sanctuary for tumor cells within the central nervous system. As a result, the metastases evolve and become extensive before becoming clinically evident. Metastatic spread of tumor cells to central nervous system may occur either via hematogenous or cerebrospinal fluid routes and involve the neuroparenchyma, leptomeninges or dura.

Neuroparenchymal metastases from neuroblastoma have varied appearances. They may be cystic lesions with calcified mural nodules. The wall and mural nodules show intense enhancement with contrast. Metastases may also be solid and hemorrhagic and show homogeneous enhancement. Gradient or susceptibility weighted imaging would help in detecting hemorrhagic components. Leptomeningeal and dural metastatic involvement if present indicates poor prognosis.

Pallister-Hall syndrome

2010-11-05T16:00:00.001+01:00

60-year-old female with history of a childhood seizure disorder, polydactyly, esophageal narrowing and imperforate anus presents to the ER with acute onset headache.

Findings

Figure 1: T1 weighted coronal MRI demonstrates an isointense homogeneous suprasellar mass extending from the floor of the third ventricle.
Figure 3: T2 weighted coronal image, again demonstrating a solid homogeneous suprasellar mass with lack of any cystic components or surrounding edema.
Figure 3: T1 post-gadolinium coronal image shows a homogeneous mass that does not enhance

Diagnosis: Pallister-Hall syndrome

Pallister Hall syndrome is an extremely rare autosomal dominant disorder first described by Judith Hall and Phillip Pallister, both pediatricians and geneticists, in 1980. The underlying mutation causing this syndrome involves the GLI3 protein which participates in gene expression and early development. The manifestations of this disorder result from both the congenital anomalies associated with the genetic mutation and from the hypothalamic hamartomas. Described congenital anomalies include but are not limited to polydactyly, imperforate anus, bifid epiglottis, and renal abnormalities. Despite variability in presentations patients consistently present with polydactyly and frequently with imperforate anus, both of which were included in this patient's medical history.

Hypothalamic hamartomas typically involve a very specific region of the hypothalamus called the tuber cinereum, which consist of gray matter situated between the mammillary bodies and optic chiasm. This region of the brain secretes histamine in association with circadian rhythms. It is most easily identified on sagittal T1 sequences. MRI remains the best imaging modality for appreciating the position and characteristics of hamartomas. The classic image findings are a homogeneous mass in the region of the tuber cinereum which is isointense to gray matter and does not enhance after the administration of gadolinium. Following gadolinium administration, normal pituitary tissue should enhance and be easily identified separate from the tumor. Coronal sequences best demonstrate the mass extending from the floor of the third ventricle. On CT a mass which is isodense to gray matter may be seen in the suprasellar cistern, depending on the size of the lesion. The lesions typically do not calcify.

While specific treatment does not exist for Pallister-Hall syndrome certain measures should be taken in these patients. First, due to the autosomal dominant nature of the disease genetic counseling should be provided to these patients especially if considering conception. Considering the benign nature of the hypothalamic hamartomas, regardless of any syndrome association removal should be based on severity of symptoms. Patients who elect to not have the tumor removed should be evaluated regularly for visual disturbances, neurological changes, and hormonal derangement. Furthermore, consideration should be made for routinely scanning any patient with polydactyly for hypothalamic hamartomas, especially if the patient has other congenital anomalies.

Sulcal artery syndrome following vertebral artery dissection

2010-11-04T16:00:00.001+01:00

Findings

Figure 1: Sagittal T2-weighted image demonstrates an elliptical focus of high signal in the spinal cord from the mid C3 to the upper C4 vertebral body level. There is slight cord expansion.
Figure 2: Axial T2-weighted image at the C3 level demonstrates high signal in the right side of the spinal cord. There is slight extension of the abnormal signal across midline. Note the absence of the normal flow void in the right vertebral artery.
Figure 3: Aortic arch angiogram demonstrates no filling of the right vertebral artery consistent with occlusion.

Diagnosis: Sulcal artery syndrome following vertebral artery dissection

Most spinal cord infarctions involve the anterior two thirds of the spinal cord in an anterior spinal artery distribution. As both anterior horns are affected, patients typically present with bilateral extremity weakness and dissociated sensory deficits secondary to the involvement of cortical spinal and spinal thalamic tracts. Vibration and proprioception testing are normal as there is sparing of the posterior columns. In acute cases, MRI imaging demonstrate swelling of the cord with high T2-weighted signal intensity in the central aspect of the cord which creates the "owl's eye" appearance on the axial images due to involvement of the central gray matter.

A second, rarer cord ischemia syndrome is cord infarct due to occlusion of the posterior spinal artery. Patients present with deficits in vibration and proprioception testing as well as ataxia. Except for elevation in protein, CSF analysis is usually normal in all types of spinal cord infarction.

The rarest form of cord infarction involves only a unilateral sulcal artery. Unlike anterior spinal artery infarcts, where both anterior hemicords are involved, in unilateral sulcal artery infarctions only one-half of the anterior spinal cord is involved. Thus patients present with an acute Brown-Séquard-like syndrome without vibratory sensation or proprioception as the posterior columns are not involved. This type of lesion appears to involve only the upper cervical spinal cord. This may be due to the better vascular and possible collateral supply of the cervical cord than then thoracic spinal cord.

On axial imaging there is a unilateral central cord lesion with a linear extension to the contralateral central cord suggesting involvement of the crossing spinothalamic pathways. Contrary to the common belief that patients with spinal cord infarction have a poor prognosis, all patients with such sulcal artery infarction improve quickly and significantly with minimal or no deficits at the follow-up, most likely owing to the rapid development of collateral flow from other branches of the anterior or the posterior spinal artery. It is worth pointing out that dissection might not be the only mechanism to explain such a syndrome as similar sulcal artery syndromes have also been reported due to other etiology such as atherosclerosis or aortic emboli.

Our patient’s MRI findings are consistent with an infarction in the sulcal artery which is the penetrating branch of the anterior spinal artery. The sulcal arteries arise from the anterior spinal artery through the anterior median fissure. Successive sulcal arteries generally alternate in their distribution to the left or right side of the spinal cord but not both. The sulcal arteries supply the anterior two-thirds of the spinal cord at any cross-sectional level. The sulcal artery occlusion in this case could be due to an embolus traveling from vertebral artery dissection site via anterior radicular artery around the C3/4. A mechanism of hypoperfusion is unlikely for such an infarction in a terminal branch artery territory.

Review of the literature identified a few additional reported cases of sulcal artery territory infarction although other forms of spinal cord infarct following vertebral artery dissection are more common. All the patients with sulcal artery territory infarction had involvement of the upper cervical spinal cord. All had unilateral Brown-Séquard-like presentations with ipsilateral arm and leg weakness, contralateral sensory loss to temperature or hyperalgesia, and minimal or no loss of vibratory sensation and proprioception. All patients had significant improvement at short-term follow up with minimal or no neurological deficits. Spinal fluid examination was normal in two of the four patients tested. Three of the four patients had MRI and all showed a pencil like appearance on the sagittal plane. On axial image, two patients had a characteristic hemi-central cord lesion with anterior extension to the contralateral central counterpart.

Retinoblastoma with recurrence following enucleation

2010-11-01T16:00:00.001+01:00

Findings

Figure 1: Contrast enhanced CT scan shows a heterogeneously enhancing intra-ocular mass in the right eye with calcification.
Figure 2: Contrast enhanced CT image shows enlargement of the right optic nerve suggestive of orbital recurrence following enucleation. Note the presence of a prosthetic globe.

Diagnosis: Retinoblastoma with recurrence following enucleation

The differential diagnosis of leukocoria in a child includes retinoblastoma, Coat’s disease, toxocariasis, retinopathy of prematurity, optic nerve drusen, persistent hyperplastic primary vitreous and phthisis bulbi. With a normal sized globe and intra-ocular calcifications the differential narrows down to retinoblastoma, Coat’s disease and toxocariasis with retinoblastoma being the most common.

Most patients with unilateral, non-metastatic retinoblastoma can be cured with enucleation alone. In patients with histologic risk factors, adjuvant chemotherapy is recommended, with the addition of orbital radiation for patients with trans-scleral involvement or tumor present at the level of the cut end of the optic nerve. Patients with metastases require intensive chemotherapy and consolidation with autologous hematopoietic stem cell rescue.

Recurrent retinoblastoma or a second primary neoplasm may be observed during follow-up. Optic nerve invasion, scleral invasion and choriodal invasion have been regarded as risk factors for recurrent disease. In general recurrent tumors have a short latent period as compared to second primary neoplasms; however this may not always be true. Recurrent retinoblastoma after enucleation can occur in the contralateral eye (type A), in the ipsilateral orbit (type B) or extend from the orbit into the brain (type C)

The most common presentation of orbital recurrence is a clinical complaint such as eyelid swelling or chemosis, suggesting that clinicians should not attribute periocular or orbital symptoms during the first year after enucleation as a sign of a benign conjunctivitis or preseptal cellulitis. A problem with the ocular prosthesis is also a frequent mode of presentation in these patients, and extrusion or displacement of a previously satisfactory prosthesis should be considered a suspicious sign for possible tumour recurrence.

Calcification maybe seen within the recurrent tumors on unenhanced CT. Most recurrent tumors appear iso to hypointense to normal temporal muscle on T1 weighted images and show moderately high signal on T2 weighted images. Contrast enhanced scans, CT or MRI, show heterogeneous enhancement of the tumor.

Cases with recurrence following enucleation should be evaluated for distant metastasis. Treatment consists of systemic chemotherapy combined with other modalities like orbital radiotherapy and stem cell rescue, depending upon the extent of metastatic disease.

Pott's Puffy Tumor

2010-10-29T16:00:00.000+02:00

Findings

Figure 1: The image shows a large collection anterior to the frontal bone and a large epidural abscess with peripheral enhancement.
Figure 2: Erosion of the frontal bone. Sinus tract of the bone into the large anterior collection.
Figure 3: Large collection anterior to the frontal bone.
Figure 4: Large epidural abscess.
Figure 5: Large epidural abscess with peripheral enhancement.
Figure 6: Large collection anterior to the frontal bone. Large epidural abscess. Normal bone marrow signal. Abnormal bone marrow signal in the frontal bone.
Figure 7: Large collection anterior to the frontal bone with peripheral enhancement. Large epidural abscess with peripheral enhancement.
Figure 8: Abnormal bone marrow signal in the frontal bone. There is a lack of enhancement of the frontal bone. The abnormal dark bone marrow signal on T1 images and lack of enhancement on T1 post gad fat sat is consistent with dead necrotic bone from severe osteomyelitis.

Diagnosis: Pott's Puffy Tumor

Pott’s puffy tumor is a subperiosteal abscess of the frontal bone that appears as a localized swelling of the forehead associated with frontal osteomyelitis. Pott’s puffy tumor is a complication of frontal sinusitis or trauma, which is predominatly seen in the adolescent age group. However, there are a few case reports in adults. Pott’s puffy tumor is a rare complication of frontal sinusitis in the post antibiotic era but can be seen in patients with undiagnosed or partially treated sinusitis. Patients will typically present with frontal scalp swelling, headache, fever, nasal drainage, and frontal sinus tenderness. Ocassionally, Pott’s puffy tumor can mimic findings of preseptal or orbital cellulitis. In severe cases, there will be neurologic decompensation. Varying degrees of hemiparesis, obtundation, papillary dilatation or aphasia have been described in case reports.

Imaging is necessary to exclude intracranial complications such as epidural abscess. Pott’s puffy tumor can also be associated with dural sinus thrombosis, meningitis, subdural empyema, epidural abscess, brain abscess, and rarely seizure. Intracranial infection is caused by posterior extension from the frontal sinus while preseptal and orbital cellulitis is caused by downward spread from the frontal sinus to the orbit. Younger children who do not have pneumatized frontal sinuses, are more likely to have ethmoid sinusitis. Orbital cellulitis is a more common complication in patients with ethmoid sinusitis.

Patients must be treated with a combination of surgery and long-term antibiotic therapy.

Infected 4th Branchial apparatus cyst

2010-10-25T16:00:00.002+02:00

Findings

Figure 1: Neck CT, contrast enhanced, at level of pyriform sinus. The left pyriform sinus is effaced by an inflammatory mass.
Figure 2: Neck CT, contrast enhanced, at level of subglottic trachea. The image demonstrates continuation of the large inflammatory mass with small areas of necrosis or abscesses. Note displacement of the trachea to the right and lateral displacement of the carotid sheath vessels. Reactive lymphadenopathy is present in the internal jugular chain.
Figure 3: Neck CT, contrast enhanced, at level of the thyroid gland. The image shows a mixed attenuation mass in the enlarged left lobe of the thyroid. This mass arises from extention of the extrinsic anterior and lateral inflammatory mass with phlegmon and abscesses from an infected 4th branchial apparatus cyst.
Figure 4: Neck CT coronal reformation, contrast enhanced. There is extensive phlegmon with multiloculated abscesses, extending from the left lower pharyngeal wall into the left lobe of the thyroid gland. Reactive lymphadenopathy in the left internal jugular lymph node chain is present.

Diagnosis: Infected 4th Branchial apparatus cyst

The main differential diagnostic considerations for a cystic neck mass in children include suppurative lymph nodes, abscess, thyroglossal duct cyst, lymphatic malformation, ranula, and branchial apparatus cyst. A branchial apparatus cyst (BAC) results from maldevelopment of an embryonic branchial apparatus (branchial cleft, arch, and pouch). Embryologically, 6 mesodermal branchial arches, separated by 5 external ectodermal branchial grooves (clefts) and 5 internal endodermal branchial pouches are present bilaterally. The majority of branchial apparatus anomalies are cysts that can arise from a remnant of a groove, arch, or pouch. A 2nd BAC is the most common and accounts for >90% all branchial cleft anomalies discovered in teens and adults. It represents 66%-75% of these anomalies discovered in children.

A 1st BAC is typically found as a cystic mass around the pinna or extending from external auditory canal (EAC) to the angle of the mandible. It can communicate with the external auditory canal. The 2nd BAC is typically found at or immediately caudal to the angle of the mandible, lateral to the carotid space and anteromedial to the sternocleidomastoid muscle. An associated fistulous track may extend from the cyst between the external & internal carotid arteries to the palatine tonsil. The cyst can extend to the carotid bifurcation, producing a beaked configuration, which has been called the "notch sign" and which is considered pathognomonic for a 2nd BAC. The 3rd BAC is typically found in the posterior cervical space behind the carotid sheath in the upper neck and along the anterior border of sternocleidomastoid muscle in the lower neck.

A 4th BAC is rare and seen more often in female infants. It can occur anywhere from the apex of pyriform sinus to the ipsilateral thyroid lobe. Involvement with the thyroid can be understood by noting that the thyroid gland arises from the 4th branchial arch. The most typical imaging finding of a non-infected 4th BAC is a unilocular thin-walled cyst found adjacent to or within the superior lateral aspect of the left thyroid lobe. Ninety-four percent of BACs involve the left side of the neck. These cysts normally show minimal or no peripheral contrast enhancement and no calcification. When infected, a thickened cyst wall is seen and often enhances with intravenous contrast media. Infected cysts often develop higher attenuation than noninfected cysts on CT images. Associated thyroiditis/thyroid abscess is not uncommon. An esophagram may demonstrate fistulous communication between the pyriform sinus and a 4th BAC, providing a pathway for spread of infection. Surgical resection of the cyst and its associated sinus or fistulous tract is necessary for complete cure. Medically treated or incompletely resected cysts/tracts are prone to recur.

Adenoid cystic carcinoma with perineural spread of tumor

2010-10-22T16:00:00.001+02:00

Findings

There is a large mass centered on the left greater sphenoid wing, extending into the left sphenoid sinus and left pterygopalatine fossa. It also extends into the left middle cranial fossa, left cavernous sinus, and left Meckel's cave. The tumor has involved V3, and foramen ovale is markedly widened on the left. There tumor has extended along the GSPN to the geniculate ganglion, and from there it has involved the tympanic and intracanalicular segments of the 7th nerve. The mass is isointense to brain on T1-weighted images and hypo- to isointense on T2-weighted images, consistent with hypercellularity. There is moderate enhancement of the mass. No macroscopic flow voids are seen to suggest a highly vascular lesion.

Figure 1: A mass lesion involving the skull base and pterygopalatine fossa on the left is shown on this axial FIESTA image. Abnormal soft tissue is seen in the left IAC as compared to fluid in the right IAC. The normal right greater wing of the sphenoid bone is shown. On the left, the greater wing of the sphenoid has been destroyed by the mass.
Figure 2: The soft tissue intensity skull base mass is again shown on the left. Infiltration of fat in the L pterygopalatine fossa is present, as compared with normal bright fatty signal in the R PPF. Asymmetrical signal is again seen in the left vs right IAC.
Figure 3: Following injection of gadolinium, moderate homogeneous enhancement of the mass lesion is shown. Also appreciated is extension into the L sphenoid sinus and displacement of the left cavernous segment of the L internal carotid artery. Meckel’s cave on the L is obliterated. Abnormal enhancement in the left IAC and abnormal thickening and enhancement of the tympanic segment of the facial nerve are also shown. Subtle linear enhancement extends posteriorly from the dominant mass along the greater superficial petrosal nerve on the left.
Figure 4: A more superior post-gadolinium image more discretely defines enhancement and enlargement of V3 on the left, posterior to the main bulk of the tumor mass. Tumor is again seen to extend posteriorly along the GSPN to the geniculate ganglion.
Figure 5: Tumor is seen to involve and expand Meckel’s cave on the left, replacing the normal CSF signal with intermediate signal intensity of a highly cellular tumor. The unaffected Meckel’s cave on the right, filled with CSF, is shown for comparison. The tumor is confined to Meckel’s cave on this image and has not extended through the dura to involve the adjacent temporal lobe.
Figure 6: A more anterior coronal T2-weighted image shows extension of the tumor into the cavernous sinus on the left, adjacent to the flow void of the internal carotid artery. Marked thickening of the third or mandibular division of the trigeminal nerve is shown on the left. The mass has markedly expanded foramen ovale on the left. This image also demonstrates atrophy and mild T2 hyperintensity of the muscles of mastication on the left, due to V3 dysfunction and resultant subacute to chronic denervation change. The masticator muscles on the right have normal bulk.
Figure 7: The enhancing tumor mass involving Meckel’s cave and the cavernous sinus on the left is again shown. This image better demonstrates the unaffected foramen ovale on the right. Also demonstrated on this image is volume loss and diffuse mild enhancement of the left temporalis muscle as compared to the right, consistent with denervation change as previously discussed). Signal drop-off due to dental hardware and inhomogeneity of the magnetic field has resulted in artifact and poor fat suppression in the right masticator space.

Diagnosis: Adenoid cystic carcinoma with perineural spread of tumor

Adenoid cystic carcinomas have a high propensity for perineural invasion and extension.
The facial and trigeminal nerves are the cranial nerves most commonly involved by perineural spread of tumor.
The facial nerve may be invaded directly by tumors of the parotid gland, or the tumor may involve the trigeminal nerve and then extend along the greater superficial petrosal nerve to reach the facial nerve.
A second “five-to-seven” connection is the auriculotemporal nerve, which also provides an important route for perineural spread of tumor.
The proximal greater superficial petrosal nerve, geniculate ganglion, and tympanic segment of the facial nerve often show normal mild enhancement due to investment by a rich vascular plexus in these regions.
Characteristics of perineural extension of tumor include abnormal enhancement and enlargement of nerves, replacement of fat in neural foramina, and widening of neural foramina. Denervation changes in innervated muscles may also be observed.

Adenoid cystic carcinoma (ACC) is the second most common malignant salivary gland tumor after mucoepidermoid carcinoma. It can arise from either the major or minor salivary glands. It is the most common malignancy of the submandibular and sublingual glands. It most commonly presents as a painless enlarging mass, though the initial presentation may be due to perineural extension of tumor (pain or paresthesia, for example) if the tumor is in a deep location. ACC is associated with a high risk of distant metastases (most commonly to the lung), and these can occur 10-20 years after initial diagnosis and treatment of the primary lesion. ACC may spread through local or direct extension of the tumor, hematogenous and lymphatic dissemination, and perineural extension.

ACC has a high propensity for perineural invasion and extension. SCCs also have a high tendency to spread perineurally, and because they are the most common head and neck cancer, one will likely encounter more cases of perineural tumor spread from SCC than from ACC in practice. Other cancers of the head and neck, including melanomas, basal cell carcinomas, and mucoepidermoid carcinomas also extend perineurally, but less commonly. Branches of the facial and trigeminal nerves are most commonly involved as they innervate the cutaneous and mucosal surfaces of the head and neck, where most tumors arise, as well as the salivary glands. The facial nerve can be invaded directly when ACC occurs in the parotid gland, or the tumor may involve the trigeminal nerve and then extend along the greater superficial petrosal nerve to reach the facial nerve. An alternate route for cranial nerve 5 to cranial nerve 7 spread (or vice versa) is the auriculotemporal nerve, which is located posterior to the neck of the mandible.

The greater superficial petrosal nerve emerges from the geniculate ganglion of cranial nerve VII carrying sensory (from the soft palate mucosa) and parasympathetic fibers. It courses anteromedially through the temporal bone and emerges through the facial hiatus. It then travels underneath Meckel’s cave and combines with the deep petrosal nerve (carrying sympathetic fibers) to form the vidian nerve. The vidian nerve travels anteriorly to the pterygopalatine ganglion, where the parasympathetic fibers synapse before being distributed to the lacrimal gland and mucosal glands of the nasal and oral cavities. This nerve pathway is vulnerable to tumor infiltration and is a common pathway for perineural extension of tumor.

Portions of the facial nerve that are invested with a rich vascular plexus may normally enhance on MRI. These normally enhancing regions are the proximal greater superficial petrosal nerve, geniculate ganglion, and tympanic segment of the facial nerve; the labyrinthine and descending mastoid segments of the facial nerve may also show mild enhancement under normal circumstances. The more distal and anterior portions of the greater superficial petrosal nerve, however, are not invested by a vascular plexus and should not enhance with contrast on MRI. Similarly, the facial nerve in the IAC does not demonstrate any enhancement under normal conditions at 1.5T. Characteristics of perineural spread to the facial nerve include thickening and abnormally intense enhancement of nerve segments, as well as replacement of fat in neural foramina by tumor. Denervation changes in the muscles of facial expression may be observed, but these are often extremely subtle due the small size of the affected muscles. Due to ACC’s high propensity for perineural spread and high tendency to recur, it is important to regularly assess for perineural extension of these tumors when MR images are being interpreted.

Sialadenitis with an obstructing sialolith in the right submandibular gland duct

2010-10-20T16:00:00.003+02:00

Findings

Coronal and axial post contrast CT images show a swollen right submandibular gland with dilatation of the intraglandular ducts and an obstructing stone.

Diagnosis: Sialadenitis with an obstructing sialolith in the right submandibular gland duct

The most common cause of sialadenitis of the SMG is an obstructing calculus with subsequent suppurative sialadenitis. Less common causes are suppurative sialadenitis leading to duct stenosis and chronic sialadenitis. Rare etiologies include include Sjogren syndrome, AIDS and bacterial/viral infection.

SMG accounts for 10% of sialadenitis of all major salivary glands. Other diagnostic considerations in SM space include reactive submandibular lymph node, mandibular osteomyelitis, benign mixed tumor, submandibular carcinoma and metastases.

Calculi are more common in the SMG duct. Compared to the parotid gland, the saliva in the SMG is thicker, much more mucinous and more alkaline. The SMG duct courses superiorly which makes it more prone to stasis. SMG duct is larger in diameter.

When sialadenitis is present therapy may depend on stone location. If the stone is in the anterior portion of the duct, the stone can be removed and gland salvaged. If stone is in the posterior duct, the duct and gland will likely be removed with the stone.

Basilar meningitis of unknown etiology

2010-10-18T16:00:00.000+02:00

Findings

Figure 1,Figure 2, Figure 3, Figure 4: Axial and sagittal T1 weighted images postcontrast demonstrate thick and nodular predominantly basilar meningeal enhancement which on sagittal images encases the middle cerebral arteries. Cerebellar parenchymal enhancement (Figure 4) secondary to late subacute infarction and infectious/inflammatory exudates.
Figure 5: Axial T2 weighted image demonstrates slight increased size of lateral ventricles with more prominent frontal horn lateral ventricles and bilateral lateral ventricle atria in a 2 week follow-up study (initial study slightly motion degraded.)

Diagnosis: Basilar meningitis of unknown etiology (presumed MDR-Tuberculosis)

This young patient with immunocompromise and altered mental status presented initially with left posterior circulation infarctions of unclear etiology. In a young patient with posterior circulation infarctions, acute vertebral artery dissection/ injury in the setting of trauma or spontaneous etiology should be considered. However, when given a history of immunocompromise and HIV, other differential diagnostic considerations such as infectious (Tuberculous, fungal, or pyogenic), inflammatory (Neurosarcoidosis), vascular (infectious vasculitis from Neurosyphilis or HIV), or neoplastic (lymphoma, leukemia, leptomeningeal carcinomatosis) etiologies should all be taken into account. To date, laboratory and CSF values for this patient continue to be non-diagnostic as to the source of this patient's basilar meningitis/vasculitis. The top consideration after discussing with the neurology team is Multi-drug resistant tuberculosis (MDR-TB) due to unimpressive response to conventional treatment regimens and inconclusive microbiological testing.

Tuberculous CNS infections are mostly caused by M. tuberculosis; atypical organisms are rare except in immunosuppressed patients. 30% of patients are HIV positive (particularly IV drug users.) Due to hematogenous dissemination, lesions usually occur at the gray-white junctions of cerebral hemispheres, basal ganglia, or cerebellum (especially in children). Hematogenous dissemination is from a systemic source, most commonly the lung, but also possibly the GU system or GI tract.

Most common manifestations of CNS Tuberculosis are meningitis, seen predominantly in the basilar cisterns, and hydrocephalus. Acutely, cerebritis can be seen, which then can progress to ring-enhancing tuberculoma lesions. Tuberculosis can also result in vasculitis and cerebral infarctions. The thick and nodular basilar meningeal enhancement in association with hydrocephalus and left posterior circulation multifocal infarctions in our patient can all be seen in tuberculosis.

Leptomeningeal sarcoidosis must be distinguished clinically from carcinomatous, lymphomatous/leukemic, and infectious meningitis. Dramatic response can be seen in some cases with steroid therapy. Sarcoid has replaced syphilis as the great mimicker. Neurosyphilis can cause arteritis of intracranial and extracranial large and medium sized arteries

2010-10-14T16:00:00.000+02:00

Findings

There is a poorly circumscribed jugular foramen mass with a permeative-sclerotic appearance of the involved bone with irregular margins and loss of the normal cortex with relative preservation of the bone density and architecture. There is centrifugal spread into the posterior fossa with a prominent dural tail and diffuse homogenous enhancement.

Jugular foramen meningioma

Jugular foramen meningiomas arise from the arachnoidal cap cells of the meninges which follow cranial nerves IX, X and XI into the jugular foramen. 5% of posterior fossa meningiomas arise in the jugular foramen and meningioma is the third most common jugular foramen mass after paraganglioma and schwannoma. If there are additional meningiomas or schwannomas, consider an association with neurofibromatosis II.

Meningiomas characteristically appear isointense to gray matter on both T1 and T2 weighted MR imaging but this appearance is variable. A relative T2 hypointensity is suggestive of a dense cellularity. There is an absence of high velocity flow voids within the mass which can help to distinguish from paraganglioma. There is dense, uniform contrast enhancement on MR and CT imaging which can help to identify a dural tail. Tumor matrix calcification is uncommon and internal hemorrhage is also rare.

Jugular foramen meningiomas typically infiltrate the surrounding skull base with relative preservation of the bone architecture. The margins of the jugular foramen are typically irregular with loss of the normal cortex. This combination of findings results in a permeative-sclerotic appearance and is different from the pemeative-destructive pattern of paragangliomas with erosion and infiltration without preservation of the underlying architecture or bone density. Additionally, schwannomas have a characteristic pattern of smooth enlargement without hyperostosis or permeative changes.

Intraorbital Lymphatic Malformation

2010-10-13T16:00:00.000+02:00

Findings

Figure 1: There is a multilobulated mass lesion in the retroorbital region with a fluid- fluid level.
Figure 3: There is an intraconal multilobulated mass with a fluid-fluid level and mild right globe proptosis.

Diagnosis: Intraorbital Lymphatic Malformation

Vascular lesions account for 5-20% of all orbital masses, and the two most common orbital vascular lesions are venous malformations (formerly known as cavernous hemangiomas) and lymphatic malformations (LM) ( formerly known as lymphangiomas). LMs are relatively uncommon in the pediatric population and account for only 4% of all childhood orbital masses. LMs are benign and most frequently found in the head and neck. Intraorbital LMs can arise in any orbital space, but are most commonly intraconal with frequent extraconal and preseptal expansion. Histologically, a vascular malformation can contain venous and lymphatic components, hence the name lymphaticovenous malformation. Of note, 70% of orbital lymphaticovenous malformations are associated with ipsilateral, noncontiguous, intracranial vascular abnormalities.

Intraorbital venous-lymphatic malformations are present at birth, but tend not to be discovered clinically until early childhood when they enlarge as a result of either intralesional hemorrhage or lymphoid hyperplasia and result in acute proptosis. Approximately one-half of all patients with orbital LMs also complain of limited ocular mobility. Additionally, conjunctival, facial, or oral vesicles may also be observed.

Radiologic imaging of intraorbital LMs demonstrates unencapsulated, irregular, lobulated, and multicompartmental masses. These lesions can have cystic as well as more solid components. The cystic elements of these masses commonly exhibit fluid-fluid levels as a result of intralesional hemorrhage. Additionally, LMs are frequently both pre- and postseptal and intra- and extraconal. They often display orbital expansion with irregular margins that traverse tissue planes. Ultrasound images of LMs demonstrate heterogeneous, ill-defined lesions with anechoic cystic portions and extraconal extension. On CT, these masses exhibit ill-defined borders, irregular attenuations, and variable enhancement with peripheral rim enhancement in cystic regions. Additionally, calcified phleboliths can be seen on CT in venous portions of these lesions. MR imaging is the preferred imaging modality to evaluate the location, vascular components and evolving blood products of venous-lymphatic malformations. LMs demonstrate iso- to slightly high signal intensities on T1-weighted images and very high signal intensities on T2-weighted images. MR imaging also allows for the simultaneous evaluation of the brain in an effort to detect any associated intracranial vascular anomalies.

The differential diagnosis for pediatric orbital tumors can be divided into osseous and non-osseous lesions. Pediatric osseous lesions of the orbit include dermoid inclusion cysts, which are most common, fibrous dysplasia, juvenile ossifying fibroma, osteosarcoma, Langerhans cell histocytosis, granulocytic sarcoma and neuroblastoma bone metastases. Non-osseous lesions of the pediatric orbit include most commonly rhabdomyosarcoma, but additionally infantile fibromatosis, infantile hemangioma, and LM.

Orbital lymphaticovenous malformations are histologically benign, but can demonstrate aggressive behavior, such as vision loss, as they expand. The treatment of such lesions is focused on ameliorating pain, alleviating optic nerve compression, maintaining ocular alignment and improving cosmetic appearance. Surgical resection is the preferred treatment for these lesions, and while complete removal can often be achieved with well-demarcated extraconal lesions, more diffuse intraconal lesions tend to be treated with subtotal resection.

Hypertrophic olivary degeneration

2010-10-07T16:00:00.002+02:00

Findings

Figure 1 and Figure 2: Noncontrast head CT shows acute hemorrhage in the superior and middle cerebellar peduncles.
Figure 3, Figure 4, Figure 6 and Figure 7: FLAIR and T2 show chronic blood products in the superior and middle cerebellar peduncles.
Figure 5 and Figure 8: Axial FLAIR and T2 show T2 prolongation and mild enlargement
of the inferior olivary nucleus of the medulla.

Diagnosis: Hypertrophic olivary degeneration

Hypertrophic olivary degeneration is a unique type of transynaptic degeneration which results in hypertrophy rather than atrophy of the affected structure, the inferior olivary nucleus. The affected circuit involves dentrorubral-olivary connections which were described by Guillain and Mollaret in 1931 as the anatomic connections related to palatal myoclonus, and is commonly referred to as the "Guillain-Mollaret triangle."

The "triangle" consists of 3 nuclei: 1) ipsilateral inferior olivary nucleus (medulla) 2) ipsilateral red nucleus (midbrain) and 3) contralateral dentate nucleus (cerebellum). The ipsilateral red nucleus and contralateral dentate nucleus are connected by the superior cerebellar peduncle. The ipsilateral red nucleus and ipsilateral inferior olivary nucleus are connected by the central tegmental tract. There are no direct anatomic connections between the inferior olivary nucleus and the contralteral dentate nucleus.

Olivary degeneration is typically seen several months after the insult. The side of olivary degeneration depends on the location of original insult and can be predicted by familiarity with the "Guillain-Mollaret triangle." When the primary lesion is in the central tegmental tract, olivary hypertrophy is ipsilateral. When the primary lesion is in the superior cerebellar peduncle or dentate nucleus, the olivary hypertrophy is contralateral. When the primary insult involves both the central tegmental tract and superior cerebellar peduncle, the olivary hypertrophy is bilateral.

The classic clinical finding associated with hypertrophic olivary degeneration is palatal myoclonus, a cyclic jerk of the soft palate.

Labyrinthitis ossificans

2010-10-06T16:00:00.004+02:00

Findings

Figure 1: Axial CT image through the left temporal bone shows complete ossification of the left superior semicircular canal.
Figure 3: Axial CT image at the level of the internal auditory canal shows non-erosive soft tissue attenuation lateral to the malleus and incus as well as partial ossification of the lateral semicircular canal.

Diagnosis: Labyrinthitis ossificans

Labyrinthitis ossificans (LO) is the end result of suppurative labyrinthitis where inflammation of the membranous labyrinth progresses to fibrosis and ossification. Suppurative labyrinthitis typically arises following meningitis, although other causes include direct infection from hematogenous sources or trauma.

LO is the most common cause of acquired childhood deafness and can be detected by CT as early as 2 months following an episode of meningitis. Following meningitis, approximately 6% to 30% of children develop some degree of sensorineural hearing loss which is typically bilateral.

On CT, osseous deposition is seen within the membranous labyrinth. On MRI, loss of the normal high signal on T2-weighted images from displacement of the endolymphatic fluid is suggestive of this diagnosis. It is important to the clinician to distinguish between cochlear involvement, non-cochlear involvement, or both as prognosis is determined by response to cochlear implantation. The degree of ossification is important in surgical planning and severe LO may preclude cochlear implantation.

Tornwaldt cyst

2010-10-01T16:00:00.000+02:00

Findings

There is no intracranial hemorrhage, calvarial fracture or transtentorial herniation. On the lower images of the brain, there is a cystic hypoattenuating lesion at the posterior wall of the nasopharynx measuring 1.4 x 1.2 cm.

Diagnosis: Tornwaldt cyst

A Tornwaldt cyst is a benign proteinaceous cyst that is located in the midline of the posterior nasopharynx, superficial to the superior constrictor muscle of the pharynx. It is surrounded by adenoid tissue and arises from notochordal remnants in the pharyngeal bursa (pouch of Luschka). They are seen in up to 4% of the population (equally in males and females) and are usually asymptomatic unless they become infected. If infected, they can cause a variety of symptoms including purulent drainage, sore throat, prevertebral muscle spasms, halitosis and Eustachian tube obstruction.

These fluid-filled cysts are usually discovered on imaging (both CT and MRI) as incidental findings. The cyst is well-circumscribed and located in the midline in the posterior nasopharynx (between the longus coli muscles). On CT, it is hypo-attenuating and appears cystic. It will almost invariably appear bright on T2-weighted images. The T1 signal will vary from CSF signal to very bright hyperintensity depending on the amount of protein, fat, hemorrhage and mucus within the cyst. A thin rim of peripheral enhancement may be seen with gadolinium administration. Nasopharyngoscopy, although not necessary for asymptomatic cases, can help supplement the diagnosis.

Treatment is not necessary in most cases. For the rare symptomatic cases treatment options include surgical excision, electrocoagulation or marsupialization.

Neurovascular compression syndrome of VII-VIII cranial nerves

2010-09-28T16:00:00.001+02:00

Findings

High resolution T2 images at the level of the internal auditory meatus demonstrate the facial and vestibulocochlear cranial nerves entering the internal auditory meatus. The facial nerve lies anterior while the eighth cranial nerves courses posteriorly. With the left side used for reference, a tortuous basilar artery is seen posteriorly displacing the normal course of the right vestibulocochlear/facial nerve complex. The presumed point of symptomatic compression is encountered posteriorly as the nerve complex “bends” over posterior aspect of the internal auditory meatus. Although sometimes seen in asymptomatic individuals, when findings are viewed in the appropriate clinical setting, NVCS should be raised as a diagnostic possibility.

Diagnosis: Dolichoectasia of the basilar artery causing right sided sensorineural hearing loss

Hearing loss can be characterized as either conductive or sensorineural based on clinical exam and audiometry. Conductive hearing loss involves an abnormality of the external auditory canal to the oval window and is best evaluated with high resolution CT as it is able to display the external auditory canal and middle ear structures, particularly the ossicles. Sensorineural deafness implies an abnormality of the inner ear, vestibulocochlear nerve, or its central components which are best evaluated with MRI.

Neurovascular compression syndrome (NVCS) refers to a group of disorders in which an aberrant or tortuous vessel causes nerve compression with subsequent hyperexcitation and neuropathy. Vascular compression syndrome has been described as a causative etiology for cranial nerves III, V, VII, VIII, and IX. Controversy exists, however, because of the normal intimate apposition of nerves and vasculature around the brainstem and the frequency with which it is seen in asymptomatic patients.

Vestibulocochlear NVCS is symptomatic vascular compression of cranial nerve VIII. Clinical symptoms are often non-specific including tinnitus, vertigo, and sensineural hearing loss. A recent article in the American Journal of Neuroradiology failed to reliably determine neurovascular compression as a cause of tinnitus although some authors maintain it may still be considered when presenting with so called "typewriter" tinnitus. In decreasing order of frequency, vessels indicated in NVCS include the anterior inferior cerebellar artery, posterior inferior cerebellar artery, and vertebral artery.

The following MRI classification system for neurovascular compression has been proposed to aid in surgical planning.
- Type I: Point compression where a limited segment of the nerve is in contact with the vessel.
- Type II: Longitudinal compression in which the nerve and vessel traverse parallel to each other.
- Type III: A vascular loop encircling the neve.
- Type IV: The nerve contour is deformed and/or thinned.

Definitive treatment involves retromastoid craniectomy and microvascular decompression in which a small synthetic sponge is interposed between the offending vascular structure and nerve.

Filar cyst

2010-09-23T16:00:00.002+02:00

Findings

Figure 1: Axial T2-weighted image demonstrates a cystic structure in the filum terminale.
Figure 2 and Figure 3: Coronal T2-weighted images demonstrate a cystic structure in the proximal filum terminale.

Diagnosis: Filar cyst

The human spinal cord develops through three distinct stages: neurulation, canalization, and retrogressive differentiation. The conus medullaris, filum terminale, and cauda equine are mainly developed and formed in the retrogressive differentiation stage as the caudal cell mass regresses.

Cystic structures within the distal spinal cord, conus medullaris, and filum terminale are commonly seen on routine lumbosacral spine sonography in the neonates. These patients often present with abnormal laboratory values and/or external body features that are suggestive of underlying spinal dysraphism or neural tube defects. The diagnostic consideration of a cystic lesion in this region includes: syrinx, neoplasm (ependymoma or astrocytoma), persistent ventriculus terminalis in the conus medullaris, and filar cyst in the filum terminale of the cord.

Filar cysts are a relatively common entity in the neonates usually detected on screening lumbosacral sonograms. However, it has not been extensively reported in the literature. It is considered a normal variant when found as an isolated finding. The exact etiology of a filar cyst has not been reported. Literature has suggested that filar cysts are developmentally similar to the septum pellucidum and ventriculus terminalis, which can regress with age. On ultrasound, it is usually describes as an anechoic, cystic structure completely contained within the filum terminale. MRI of the lumbosacral spine can be obtained in cases that are questionable on ultrasound. Filar cyst follows the typical characteristic of a simple cyst in all sequences of an MR study. Ventriculus terminalis is a normal developmental variant described as a nonenhancing dilation of the ependyma-lined central canal at the level of the conus medullaris. Persistent ventriculus terminalis deserves special attention such that it is often used interchangeably with filar cyst in the literature, in the setting of cystic lesions seen in the distal lumbar spinal cord proximal to the conus medullaris. A cystic lesion in the absence of a solid component makes a neoplastic process less likely. A syrinx isolated to the distal spinal cord is also less common as it usually has a superior extension.

Treatment options are primarily based on patient's symptomatology. In asymptomatic neonates/infants, no further imaging is needed.

Melanotic Neuroectodermal Tumor of Infancy (MNTI)

2010-09-22T16:00:00.000+02:00

Findings

Large mass involving left side of face with invasion, mass effect, and extensive bony involvement. The mass does not appear to cross the midline. Enhancing focus on MR adjacent to the superior aspect of the falx and superior sagittal sinus. FDG-avid spine lesions.

Diagnosis: Pathology-proven melanotic neuroectodermal tumor of infancy (MNTI)

Discussion

MNTI is a rare osteolytic, pigmented neoplasm that typically affects the head and neck, predominantly the maxilla, of infants. It is typically considered a benign lesion, with only a few reported cases of metastatic disease reported in the literature. It usually presents in the first year of life. It may appear as a rapidly expanding, non-ulcerated, lightly pigmented, blue or black lesion on the anterior aspect of the maxilla. It may extend intraorally, cause bone destruction and dislodgement of teeth.

MNTI is considered to be of neural crest origin, and some patients will high urinary excretion of vanillylmandelic acid (VMA). The tumor is typically non-encapsulated, showing local invasion of bone. The histologic appearance is similar to other cells of neural crest origin, demonstrating small, round blue cells, as well as containing a moderately vascular fibrous background. Part of the lesion may contain large polygonal cells arranged in sheets that contain melanin. Immunohistochemistry and electron microscopy can aid in the final diagnosis. The few reported cases of malignant disease have noted increased numbers of mitoses per high-powered field.

Conventional radiography may demonstrate a well-circumscribed or ill-defined radiolucency, with destruction of bone as the lesion progresses. CT can delineate the extent of soft tissue involvement and osteolysis. Contrast-enhanced MRI can demonstrate soft tissue tumors with nonenhancing, heterogeneous tissue density and can also demonstrate osseous involvement. There may be foci of T1-hyper/T2-hypointensity secondary to melanin.

Surgical excision with partial maxillectomy and 5 mm margins are typically curative, with 10-15% recurrence rates. There are no standards of care for malignant disease.

Initial biopsy of this patient's facial lesion demonstrated a high mitotic index. After 2 surgical excisions and recurrence, the patient developed intracranial and spinal column metastases. The patient underwent multiple cycles of radiotherapy and chemotherapy. The intracranial lesion was never biopsied due to the precarious location, however it has regressed, and there appears to be a slight interval decrease in size of the soft tissue component of the maxillary lesion.

Wernicke’s encephalopathy

2010-09-16T16:00:00.004+02:00

Findings

There is increased T2 signal and diffusion restriction in the thalami bilaterally. There is no contrast enhancement.

Diagnosis: Wernicke’s encephalopathy

Discussion

Wernicke's encephalopathy occurs with vitamin B1 (thiamine) deficiency. It is associated with malnutrition and is commonly seen in alcoholics. Wernicke's encephalopathy manifests itself as memory loss, ataxia and oculomotor dysfunction. Thiamine plays a vital role as a cofactor for several enzymes involved in carbohydrate metabolism. Without thiamine, the energy requirements of neuronal cells are not met resulting in cell death and neurologic dysfunction.

Wernicke's encephalopathy is reversible and if suspected, treatment should begin promptly. Parenteral thiamine should be administered promptly. The thiamine should be given prior to any glucose infusion. The addition of glucose in a thiamine deficient patient will exacerbate the encephalopathy. Patient's with thiamine deficiency are also likely to be hypomagnesemic and parenteral magnesium sulfate should also be administered.

Radiologic overview of the diagnosis

Wernicke's encephalopathy manifests itself as increased T2 signal in the medial thalami, hypothalamus and periaqueductal grey matter. There is associated diffusion restriction in affected areas. In chronic cases, there is atrophy of the mamillary bodies. The sensitivity of MR to diagnose Wernicke's is estimated at approximately 50% so the lack of these imaging findings, do not exclude the diagnosis of Wernicke's encephalopathy. CT is even worse than MR in the diagnosis of Wernicke's and should be used to rule out an acute intracranial process. Alcoholic induced Wernicke's will manifest the same above findings, but will also show superior vermian atrophy.

In this case, there is increased T2 signal and diffusion restriction in the medial thalami bilaterally. There is no contrast enhancement. The patient has lymphoma and a chronic history of vomiting. With this history, Wernicke's encephalopathy was thought to be the cause of the patient's altered mental status. The lack of contrast enhancement makes the diagnosis of lymphoma highly unlikely.

Anterior communicating artery aneurysm

2010-09-15T16:00:00.002+02:00

Findings

The head CT without contrast shows a region of hyper density along the anterior falx along the course of the anterior cerebral artery concerning for acute blood products. CT angiogram shows an anterior communicating artery aneurysm that splays both anterior cerebral arteries and points anteriorly No definite blood products within the suprasellar cistern are seen. There is no intraventricular hemorrhage.

Diagnosis: Anterior communicating artery (ACom) aneurysm (unruptured)

Key points

Aneurysm development and rupture risk reflect complex combination of inherited susceptibility and acquired mechanically-mediated vessel wall stresses4."
Associated with connective tissue disorders such as fibromuscular dysplasia, Ehlers-Danlos syndrome (type IV), ADPCKD
Familial intracranial aneurysms: Occur in clusters of 1st degree relatives

Location: 90% arise from circle of Willis
- 90% anterior circulation (Acom and internal carotid-com most common sites)
- 10 % posterior (Basilar artery bifurcation, PICA most common)
- 1-3% misc sites distal to COW (often traumatic, mycotic, oncotic)

Risk of rupture:
- Increased risk of rupture:
- Size
- Multilobed
- Apical "bleb"
- Length: neck aspect ratio >1.6

Giant aneurysms (>2.5cm) present both the risk of rupture and symptoms related to mass effect
15-20 % multiple
Estimated risk of rupture: 1-2% year cumulative for unruptured aneurysms

Demographics:
- F>M (especially with multiple aneurysms)
- Incidence: 1/100000 (<35yo); 44/100000 (>65yo)

Treatment: Cost-effective strategy for unruptured aneurysms
- Endovascular treatment was most cost effective for anterior circulation aneurysms 7-25 mm in size
- No treatment was most cost-effective for anterior circulation aneurysms < 7mm
- Surgical treatment was most cost effective for anterior circulation aneurysms > 25m
- Endovascular coiling has been accepted as effective treatment, though controversy still exists between surgical and endovascular therapy.

Long-term (10yr) followup of 1036 coiled aneurysms required retreatment in 7% and rebleeding in 0.5%

Postictal Imaging Findings

2010-09-14T16:00:00.001+02:00

46-year-old male presented to the emergency room after a first seizure. He has no significant or contributory past medical history.

Follow-up FLAIR imaging obtained approximately 5 weeks later.

Findings

Figure 1 and Figure 2: FLAIR and DWI images show abnormal increased signal in the left temporal lobe. The right temporal lobe is questionably involved. The differential diagnosis for these findings included, but is not limited to, neoplasm, infection, and postictal changes.
Figure 3: Follow-up FLAIR imaging obtained approximately 5 weeks later demonstrates resolution of these findings, consistent with postictal change.

Diagnosis: Postictal Imaging Findings

A seizure is "a sudden alteration of the CNS resulting from a paroxysmal high frequency or synchronous low frequency, high voltage electrical discharge". Imaging (CT or MRI) is indicated in cases of:
- New onset of seizure activity
- Change in pattern of previous seizure pattern
- Patients with focal neurological defects or altered mental status
- Prolonged postictal state, especially if associated with neurological defects

Following seizure activity, imaging is used to identify an underlying etiology. Differential possibilities include structural/anatomical abnormalities, space-occupying masses (primary or secondary brain neoplasms, abscesses), cerebrovascular accidents, transient ischemic attacks, hemorrhage, infectious processes (meningitis, encephalitis) venous thrombosis, and vasculitis. If performed shortly after the ictal event, CT and MR imaging may demonstrate findings that are secondary to the physiological mechanisms related to the seizure itself. These findings are most likely to occur following status epilepticus.

The mechanism and pathophysiology of these findings are unknown. Some theories are that the findings occur as a result of breakdown of the blood brain barrier. This results in transient focal brain edema, accounting for various imaging findings. Other theories propose arteriovenous shunting of blood during seizure activity that results in accumulation of toxic metabolites, ischemia, and acidosis. Most theories implicate ischemia and transient cytotoxic edema as the cause of brain changes.

Imaging findings are nonspecific and can overlap with those seen in other disease entities such as infarction/ischemia, venous thrombosis, vasculitis, infection, neoplasm, arterial thromboembolism and metabolic encephalopathy. History, presenting signs and symptoms, follow-up imaging and other relevant laboratory data can further narrow the differential diagnosis.

On CT, possible postictal imaging findings include:
- effacement of adjacent cortical sulci
- focal gyral edema
- decreased gyral attenuation
- mild to moderate gyral enhancement on contrast-enhanced images

On MRI, possible findings include:
- increased signal on T2WI (most common in the frontal and parietal lobes but also seen in the temporal and occipital lobes as well as other regions in the brain such as the hippocampus)
- corresponding hypointensity on T1WI
- abnormal contrast enhancement
- diffusion restriction and reduced ADC
- gyral swelling with effacement of adjacent sulci

Bilateral involvement is more common than unilateral. Lesions usually overlap arterial and watershed territories. In addition, lesions are usually in the cortex or subcortical white matter and spare the basal ganglia. Studies have shown leptomeningeal enhancement on post-contrast MRI. Follow-up imaging reveals complete or near-complete resolution of these findings.

It is important to recognize the various imaging findings that can be seen in the postictal period to avoid unnecessary biopsy and further workup such as angiography and biopsy. The postictal imaging appearance can be confused with other entities such as neoplasm, infection and infarction. The amount of time until resolution of these transient imaging findings is unclear. Studies have shown resolution of postictal changes in as low as 5 days. However, the majority of cases resolve over weeks - months. Patients should be re-imaged to confirm the transient nature of abnormal MR findings, usually within 4 - 6 weeks. It is important for patients to be re-imaged only after a seizure-free interval.

Adult Onset Adrenoleukodystrophy

2010-09-07T16:00:00.002+02:00

Findings

Figure 1 and Figure 2: Axial T2 weighted and FLAIR images demonstrate confluent symmetric hyperintensity in the peritrigonal parietoccipital deep white matter, compatible with adult onset X-ALD.

Diagnosis: Adult Onset Adrenoleukodystrophy

Adrenoleukodystrophy is an x-linked inherited disease involving the central nervous system and adrenal cortex. It results from an inability of peroxisomes to oxidize fatty acids. While seen most commonly in young males, it is also known to present in female heterozygotes. In adults, patients present with varying degrees of cognitive impairment, peripheral neuropathy, bladder and sexual dysfunction.

On imaging, "classic" adrenoleukodystrophy will demonstrate bilateral confluent hyperintense areas in the parietoccipital deep white matter on T2WI and FLAIR. If contrast is administered, it is common to see peripheral linear areas of enhancement with a “leading edge”. In AMN, T2 hyperintensity is also common in the spinal tract fibers of the pons, cerebral peduncles, and internal capsule.

Adult onset adrenoleukodystrophy has been broken down into four main subgroups. The first group is referred to as Pure AMN and is the most common subtype. Patients in this group present with thoracic spinal cord atrophy without any focal lesions and a normal brain MR. Clinically they present with spastic paraparesis and bladder dysfunction. The second group is referred to as AMN Type 1, in which MR will demonstrate T2 hyperintensity along the long tracts of the brain, such as the corticospinal, spinothalamic, and auditory pathways. AMN Type 2 demonstrates extension beyond the long tracts and crosses the corpus collosum. These patients deteriorate much more rapidly and this form most accurately fits this case presentation. The fourth type, Adult Cerebral ALD, results in severe lobar white matter involvement with marked cerebral atrophy.

It is important to consider adult onset ALD/AMN in the differential diagnosis of all adult demyelinating disorders, since it is commonly thought of as a pediatric diagnosis and patients are frequently misdiagnosed with multiple sclerosis or ALS. Early recognition can affect prognosis and delay rapidly progressive neurological deterioration.

Confirmation of the diagnosis can be obtained by various laboratory examinations. Patients will demonstrate elevated concentrations of plasma VLCF. Adrenal function testing will show diminished levels of ACTH. Genetic testing can clinch the diagnosis with a mutation of the ABCD1 locus. Treatment subsequently consists of dietary restriction, Lorenzo’s oil, and statins.

Bilateral ectopia lentis

2010-09-01T16:00:00.000+02:00

Findings

Figure 1: Axial noncontrast CT of the head at the level of the orbits demonstrates posterior dislocation of both lenses, which now rest dependently in the vitreous. The etiology in this particular patient was repetitive trauma from serial falls.

Diagnosis: Bilateral ectopia lentis

The crystalline lens of the eye is designed to refract the light entering the iris and project/focus it onto the retina. The lens itself contains no vasculature, nerves, or connective tissue. It sits behind the iris and the front of the lens is in contact with the aqueous fluid of the anterior chamber while the posterior surface of the lens is in contact with the vitreous. The lens is held in place by zonular fibers, otherwise known as suspensory ligaments. These fibers connect to the cilliary body around the circumference of the lens.

Subluxation (partial dislocation) or luxation (complete dislocation) of the crystalline lens, otherwise known as ectopia lentis, is caused by dysfunction or disruption of these zonular fibers. Trauma is the most common cause of this disorder. The absence of a traumatic history should prompt consideration of hereditary causes of zonular fiber dysfunction; predisposing conditions include Marfan syndrome, homocystinurea, tertiary syphilis, and Weil-Marchesani syndrome.

Patients will complain of monocular diplopia, markedly decreased visual acuity in the affected eye(s), and/or poor near vision.

Treatment is determined by lens position, with anterior chamber dislocation often being a surgical emergency. As the aqueous humor of the eye flows in the anterior chamber, around the iris from the cilliary body to the canal of Schlemm, this route can become acutely obstructed with anterior dislocation leading to acute glaucoma. The cornea and iris are also at risk for damage. Posterior dislocation may be treated conservatively depending on lens position, but may also lead to uveitis or glaucoma in some cases.

Germinal matrix hemorrhage

2010-08-26T16:00:00.000+02:00

Findings

Hyperechogenic mass like hemorrhage into the right caudothalamic groove with ventricular extension, extension into the septum pellucidum, and resultant hydrocephalus; Grade 3 intraventricular germinal matrix hemorrhage.

Diagnosis: Germinal matrix hemorrhage

Key points

Risks for germinal matrix hemorrhage:
- Less than 32 weeks gestational age
- Under 1500g
- 20-25% risk in premature, low birth weight infant

Germinal matrix
- Proliferating cells; lines the periventricular spaces of the lateral ventricles and third ventricle
- Largest at 24-26 weeks, then involutes
- Begins involuting at the level of the third ventricle
- Involuted completely at 36 weeks

Mechanisms behind germinal matrix hemorrhage-
- Venous bleed
- From cardiovascular instability from lack of autoregulatory mechanism in the preterm infant
- Watershed bleed
- Nearly exclusively occurs in the first 1 wk of life, 50% on day 1
- Identifying and grading germinal matrix hemorrhage
- Blood is always as dense as choroid plexus
- Classic hemorrhage in the caudothalamic groove looks like a mass. May extend into the ventricles

Classification:
- Grade 1: Classic case caudothalamic groove looks like a mass
- Grade 2: Intraventricular extension, usually no long term sequelae
- Grade 3: Dilated ventricles
- Grade 4: Parenchyma, actually from venous hemorrhagic infarct

Non-hemorrhagic pituitary apoplexy

2010-08-24T16:00:00.009+02:00

Findings

A mixed signal (mildly hyper intense on T1-weighted and mixed hyper/hypo intense on T2 weighted sequences) lobular mass with thin rim-enhancement arises from the sella, extending superiorly above the diaphragm sellae (“snowman sign”), deviating the optic chiasm upwards. There is no diffusion restriction, and no susceptibility artifact (on B0 DWI sequences) to suggest hemorrhage. The clivus, and bony sella are intact. A thick rim of dural enhancement dorsal to the clivus is noted.

Diagnosis: Non-hemorrhagic pituitary apoplexy (with underlying macroadenoma)

Key points

Pituitary apoplexy (PA) (e.g. "necrosis") refers to hemorrhage or infarction of the pituitary.
Commonly there is a pre-existing macroadenoma (65-90%).
Acute clinical syndrome includes HA, visual defects/ophthalmoplegia, AMS, and variable endocrine deficiencies.
Acute imaging features show enlarged gland (T1/T2 isointense) with peripheral enhancement, with or without hemorrhage.
Subacutely – gland T1/T2 hyper intense, and chronically – appears as "empty sella" (filled with CSF) with T1 hypo / T2 hyper signal
T2*GRE sequence is very sensitive in looking for hemorrhagic products.
Sometimes there is subarachnoid hemorrhage.
Thickening/enhancement of adjacent dura (50%) and sphenoid mucosa (80%)
Differential diagnosis includes: Pituitary macroadenoma (non-hemorrhagic), craniopharyngioma, Rathke's cleft cyst, pituitary abscess, primary intrapituitary hemorrhage, or giant thrombosed intrasellar aneurysm.
Patients often suffer from long-term pituitary hormonal insufficiency.
Treatment of PA includes: Steroids, fluid/electrolyte replacement, and sometimes surgical decompression.

Discussion of disease

Pituitary adenomas are benign, slow-growing tumors which arise from the adenohypophysis, classified as either micro (< 10mm, 40 %) or macro (> 10 mm, 60%). However, occasionally leptomeningeal metastases can be seen. Patients present with indolent onset of headache, bitemporal hemianopsia (from optic chiasm compression), endocrinologic symptoms.

Pituitary apoplexy (PA), or pituitary necrosis, is usually caused by hemorrhage or infarction of the gland. There can, however, be bland necrosis (without either). The clinical syndrome is of somewhat acute onset with headache, visual defects/ophthalmoplegia, altered mental status, and variable endocrine deficiencies. Pre-existing macroadenoma is very common (65-90%). There is often associated subarachnoid hemorrhage. Thickening / enhancement of the adjacent dura and sphenoid sinus mucosa is very common. Sheehan’s syndrome is a rare peri-partum or post-partum (can be up to 15-20 yrs after index pregnancy) infarction of the pituitary with loss of anterior pituitary hormonal function. Long-term pituitary insufficiency is very common after PA. Treatment may include steroids, fluid/electrolyte replacement, or even surgical decompression.

Radiologic overview

CT (macroadenoma) – isodense to grey matter; fill and expand the sella turcica. CT is excellent for evaluating for sphenoid sinus invasion / bony destruction. Hemorrhage 10%, rarely calcify; pituitary apoplexy appears as hyper dense (acute), or as an "empty sella" if chronic, and very characteristic rim-enhancement.

MR – sellar mass without separate identifiable gland (mass is the gland) with "figure of 8" or "snowman" configuration (coronal), from constriction is caused by diaphragma sellae. Pituitary apoplexy has similar findings, with signal changes based presence/age of hemorrhage. Chronic PA will appear as an "empty sella" (T1 hypo, T2 hyper = filled with CSF). There is thickening / enhancement of adjacent dura in 50% of cases (seen in the presented case), and thickening / enhancement of sphenoid sinus mucosa 80% of the time.

Florid Cemento Osseous Dysplasia

2010-08-24T16:00:00.000+02:00

Findings

Figure 1, Figure 2, Figure 3, and Figure 4: Mandibular and maxillary cystic lesions with central calcification, bony expansion and selective involvement of the periapical regions are noted.

Diagnosis: Florid Cemento Osseous Dysplasia

Florid cemento-osseous dysplasia is a slow growing benign lesion which is extremely aggressive and infiltrative. It involves the periapical regions of both the maxilla and mandible with a diffuse distribution of mixed lucent-opaque osseous changes. The lesions are benign fibro-osseous lesions, which histologically, represent normal bone replaced by highly cellular fibrous connective tissue and cementum. Cemento-osseous dysplasia predominantly affects females greater than males (10-14:1) with a predilection for African American patients. Treatment of these lesions should be further radiographic follow-up without surgery unless the lesions become symptomatic, necrotic, or super-infected. Odontoma would also be in the differential as it is a hamartomatous malformation composed of odontogenic tissues. These lesions are usually discovered in the 2nd decade of life and can cause impaction, malpositioning or resorption of adjacent teeth. Ameloblastoma is the most common odontogenic tumor arising from follicular epithelium, dental lamina or enamel. It is a benign lesion but extremely aggressive and infiltrative. It most commonly occurs as an expansile lesion in the posterior mandible in the region of the third molar within the 3rd to 5th decades of life. The unicystic variant occurs in adolescents and has a soap bubble like appearance and involves the ramus and posterior body of the mandible. Large tumors may erode the bony cortex and infiltrate adjacent soft tissues. More malignant processes such as osteosarcoma exhibit a more pronounced periosteal reaction, bone destruction and the presence of a soft tissue mass. Multifocal osteosarcoma is rare. Also, chronic diffuse osteomyelitis is less likely, as it is usually unilateral, associated with pain and fever, exhibits poorly defined borders and would not be exclusively confined to tooth bearing areas.

Joubert syndrome

2010-08-19T16:00:00.003+02:00

Findings

There is agenesis of the vermis. The interpeduncular fossa is deep. There is a cerebellar cleft. There is prominence and thickening of the superior cerebellar peduncle. There is a bat wing configuration of the fourth ventricle.

Diagnosis: Joubert syndrome

Key points

Joubert syndrome is an autosomal recessive genetic disorder that affects the cerebellum and midbrain. There is agenesis/hypogenesis of the cerebellar vermis and malformation of the midbrain and brainstem.

With poor development of the cerebellar vermis and brainstem, patients can present with ataxia, hypotonia, and hyperpnea. One of the first clinical signs of Joubert is episodic hyperpnea or apnea in an infant. Breathing can reach upwards of 160 breaths/minute. Mild mental retardation is often seen, though some may have normal intelligence. Patient health and growth are usually not affected. Patients with Joubert benefit from physical, occupational, and speech therapy. Infants with respiratory abnormalities require respiratory monitoring.

Radiologic overview of the diagnosis

The initial radiologic manifestations are often seen on fetal ultrasound with increased nuchal lucency being the most apparent finding. Fetal or Brain MR is the best modality to evaluate the presence of Joubert syndrome.

The classic findings are a hypoplastic/aplastic vermis, thick superior cerebellar peduncles, a deep interpeduncular fossa, and an abnormal midbrain. This configuration resembles a molar tooth and is often referred to as the "molar tooth" sign. The fourth ventricle also takes on a bat wing configuration. The midbrain is usually decreased in AP dimension. In this case, there is complete agenesis of the vermis and the molar tooth sign can be seen with thickening of the superior cerebellar peduncles. The corpus callosum and pars intermedia is thickened and may reflect a compensatory response by the brain adapting to the lack of a vermis.

Spinal Cavernous Angiolipoma

2010-08-18T16:00:00.004+02:00

Findings

Figure 1: Sagittal T1 image of the thoracic spine demonstrates a mixed signal soft tissue epidural mass posterior to the cord at the T4-T5 level causing posterior impression upon the thecal sac. There is also a T1-bright infiltrating lesion within the T5 vertebral body.
Figure 2 and Figure 3: Sagittal post-contrast T1 imaging shows an enhancing lesion with both bony and soft tissue components. This was localized to the right paraspinal soft tissues and there is compression of the cord. Bony involvement is seen in the vertebral bodies of T11 and L1 and in the posterior elements of multiple other thoracic levels.

Diagnosis: Spinal Cavernous Angiolipoma

Spinal angiolipomas are a rare entity that are histologically benign. These fatty tissue lesions have been quoted in the literature as representing 0.14-1.2% of all spinal axis tumors. Spinal angiolipomas are typically found in the thoracic vertebrae owing to the spine's regional variation in blood supply. The vast majority of epidural noninfiltrating angiolipomas are posterior or posterolateral in location. Patients are more commonly female and usually present in the fourth or fifth decades of life. Symptoms are slow and progressive over several months, with cord compression commonly seen at presentation. Other commonly seen symptoms include: back pain, sphincter dysfunction, progressive paraparesis, lower extremity paresthesias, and hyperreflexia. In rare cases, symptomatology may be acute due to factors such as spontaneous hemorrhage, venous thrombosis, or “steal” phenomenon.

Spinal angiolipomas are divided into two subtypes: the more common noninfiltrating type and the more aggressive (but still histologically benign) infiltrating type. An angiolipoma is termed infiltrating based on bony involvement.

Classically, spinal angiolipomas are T1 hypointense enhancing epidural lesions with or without bony involvement. The intraosseous component is usually heterogenous on T1 imaging. MR is frequently obtained due to patients symptoms of possible cord compression, and it is important to rule this entity out. Differential diagnosis would include hemangiomas, metastatic melanoma and lipid-rich metastases like liposarcoma and the clear cell variant of renal cell carcinoma. On CT, these are indistinguishable from hemangiomas. When viewed in bone windows, the typical “corduroy” appearance with linear streaks of high attenuation can be seen as well as the more stippled foci of increased density seen on axial imaging. To distinguish the two, a pathologic diagnosis is essential

The mainstay of treatment for patients with neurologic symptoms is cord decompression. When possible, surgical excision is preferred with an excellent prognosis for these patients. Heavy bleeding is typical, especially with the infiltrating type owing to the rich vascularity of these lesions. Typically, the neurosurgeon will have multiple blood products available at the time of surgery. For the case discussed above, the estimated blood loss at the time of surgery was 1800cc with 5 units of packed red blood cells administered.

Aneurysm of the right cervical internal carotid artery causing vocal cord paralysis

2010-08-12T16:00:00.002+02:00

Findings

CT imaging through the neck demonstrates findings suggestive of right vocal cord paralysis.
Figure 1 shows dilation of the right pyriform sinus.
Figure 2 shows thickening and medial positioning of right aryepiglottic fold.
Figure 3 shows dilation of the laryngeal ventricle.
Figure 4: CT through the skull base reveals a rounded well defined brightly enhancing mass in the right carotid space displacing the carotid and internal jugular vein.
Figure 5: MR images demonstrate flow void on T2 weighted images.
Conventional angiography confirms an aneurysm of right internal carotid artery.

Diagnosis: Aneurysm of the right cervical internal carotid artery causing vocal cord paralysis

Unilateral vocal fold paralysis (UVFP) occurs from a dysfunction of the recurrent laryngeal or vagus nerve innervating the larynx. Clinical presentation includes characteristic hoarseness often accompanied by swallowing disabilty, weak cough, and sometimes shortness of breath. Its is important to note that a high vagal lesion results in both a recurrent laryngeal nerve and superior laryngeal nerve palsy with the latter resulting in significant anesthesia of the pharynx and increasing the risk for aspiration

CT scanning or MRI should be performed as part of a workup for a unilateral vocal fold paralysis (UVFP) of unknown etiology. The imaging should include the entire path of the vagus/recurrent laryngeal nerve involved. For left unilateral vocal fold paralysis (UVFP), imaging should extend from the base of skull to the mid chest (arch of the aorta) with right sided vocal fold paralysis including the base of the skull to the clavicle.

Unilateral vocal cord paralysis can be reliably identified on cross sectional imaging. Characteristic findings include:
1. Medial positioning and thickening of the ipsilateral aryepiglottic fold.
2. Ipsilateral pyriform sinus dilatation.
3. Ipsilateral laryngeal ventricle dilatation.
4. Fullness of the ipsilateral true vocal cord.
5. Anteromedial positioning of the ipsilateral arytenoid cartilage.

Causes of vocal cord paralysis are varied with nearly 25% classified as toxic or idopathic. Post-surgical cord paralysis is another important consideration often without specific imaging findings. Identifiable causes include mass compression and or malignant invasion. Although rare, aneurysm or pseudoaneurysm of the cervical internal carotid artery should be considered in the differential diagnosis of a carotid space mass. Because of the intimate proximity of structures within the carotid space, it is sometimes difficult to definitively determine the epicenter of an enhancing lesion. However, as the resolution of cross-sectional imaging improves, preoperative characterization is increasingly possible. A demonstrable arterial connection, arterial enhancement, peripheral calcification, and flow void on MR imaging is suggestive of the diagnosis.

Pleomorphic Adenoma of the lacrimal gland

2010-08-10T16:00:00.000+02:00

Findings

Completely ossified left lacrimal gland with no soft tissue mass, associated superficial inflammatory change or proptosis.

Diagnosis: Pleomorphic Adenoma of the lacrimal gland

Pleomorphic adenomas (benign mixed tumors) are the most common major salivary gland tumor often found in the parotid glands. When seen in minor salivary glands, the hard palate and the upper lip are the most common locations. It is, however, the most common epithelial tumor of the lacrimal gland. Approximately 50% of lacrimal masses are secondary to epithelial tumors; the other 50% are due to lymphoid and inflammatory causes. It will usually present as a palpable lacrimal fossa mass or proptosis. Other lacrimal gland tumors include: germ cell (dermoid and epidermoid), lymphoma/leukemia, metastasis, and sarcoma.

Pleomorphic adenomas are composed of epithelial and connective tissue components. Lesions may have a variable histology with growth patterns in sheets, strands, or islands of spindle and stellate cells with a myxoid configuration occasionally predominating. Cystic degeneration, squamous metaplasia, calcification or ossification may be observed in lacrimal gland pleomorphic adenomas. There may or may not be lytic remodeling or erosion of adjacent bone depending upon the chronicity of the tumor; adjacent bone abnormality does not necessarily confer malignancy. A small percentage of pleomorphic adenomas may undergo malignant transformation.

Sinonasal and orbital lymphoma

2010-08-06T16:00:00.000+02:00

Findings

Figure 1: Coronal image from CECT shows enhancing mass involving the maxillary and ethmoid sinuses and left orbit.
Figure 2: Coronal image from CECT shows mass in maxillary sinus causing dehiscence of floor of left orbit.
Figure 3: Axial image from CECT shows enhancing mass in ethmoid sinuses and intraconal portion of left orbit causing proptosis.

Diagnosis: Sinonasal and orbital lymphoma (Diffuse Large B-cell Lymphoma)

Malignant neoplasms of the nasal cavity and paranasal sinuses occur primarily in the 5th to 6th decade. Exposure to industrial fumes, leather tanning and even wood dust have been implicated in the carcinogenesis of certain malignant sinonasal tumors. Interestingly cigarette smoking and heavy alcohol consumption have not been linked to sinonasal cancers despite there strong association with other head and neck cancers.

Lymphomas of the sinonasal tract are uncommon neoplasms that can be clinically and radiologically difficult to distinguish from destructive non-malignant processes such as aggressive sinusitis or benign neoplasms. Primary sinonasal lymphoma is rare in western populations, but is more common among Chinese and Japanese populations. Approximately 2000 cases of sinonasal cancer are diagnosed each year in the United States. Lymphoma accounts for less than 5% of all sinonasal cancers and less than 1% of all head and neck cancers.

Low grade lymphomas usually present with a nasal cavity or paranasal sinus mass associated with obstructive symptoms. High grade lymphomas are more likely to present with aggressive signs and symptoms including nonhealing ulcer, cranial nerve manifestations, facial swelling, epistaxis, or pain. Of note, the high grade B-cell lymphomas tend to present with soft tissue or osseous destruction, particularly of the orbit with associated proptosis, whereas T-cell lymphomas are associated with nasal septal perforation and/or destruction.

In Asian populations Natural Killer or T-cell (NK/T-cell) immunophenotypes are more common then B-cell where-as in western populations, there seems to be a slight B-cell predominance. Prognostically NK/T-cell lineage lymphomas have a worse outcome then B-cell. The reason of this discrepancy is not clear but may be related to NK/T-cell frequent expression of an energy-dependent efflux pump capable of transporting chemotherapeutic drugs out of the cell.

Computed tomography (CT) and magnetic resonance imaging (MRI) play complementary roles in determining the full extent of a sinonasal neoplasm. CT is useful to detect bone erosion but can be limited to differentiate the extent of the tumor particularly as the mass approaches the periobita. MRI provides excellent delineation of tumor from surrounding inflammatory tissue and secretions within the sinuses which often accompany obstructive masses. Most sinonasal tumors are highly cellular and give intermediate signal intensity on both T1 and T2 weighted imaging and demonstrate diffuse enhancement.

Intramedullary spinal cord metastases

2010-07-30T16:00:00.001+02:00

Findings

Figure 1: Sagittal T1 weighted image shows focal expansion of the cord substance in the region of the upper dorsal vertebrae (T3 and T4). The area is isointense to the cord.
Figure 2 and Figure 3: Sagittal T2 weighted and STIR images show a hyperintense lesion involving the dorsal spinal cord with edema, seen at its rostral and caudal ends. Incidentally seen is a hemangioma (Figure 1 and Figure 2) involving the T7 vertebral body.

Figure 4 and Figure 5: Post contrast axial and sagittal T1 weighted images show almost homogeneous enhancement in the lesion. Incidentally seen are pleural effusion (Figure 5) and pulmonary metastasis (Figure 5).

Diagnosis: Intramedullary spinal cord metastases (ISCM)

The most common neurological complications of breast cancer are brain metastases and spinal cord compression. In most instances spinal cord compression is caused by extra-dural soft tissue masses, however ISCM is a rare and a distinct diagnostic possibility.

ISCM is an unusual presentation of systemic malignancies. Close to 50% of all ISCMs arise from primary lung tumors, with small cell carcinoma being the most common. The remainder originate from primary cancers of the breast, colon, melanoma, lymphoma, and kidney. ISCMs are typically solitary and extend over a length of 2-3 vertebral segments.

The clinical manifestations of metastatic intramedullary spinal cord tumors are typically back pain, paresthesia, paraparesis, spasticity of the lower extremities, and autonomic dysfunction.

Magnetic resonance imaging is considered the gold standard for the diagnosis of tumors affecting the spinal cord. The typical ISCM seen on MRI is a small, isolated, oval-shaped lesion with or without slight deformation of the spinal cord profile. It is isointense on T1-weighted images with a nodular contrast enhancement and a pencil-shaped hyperintensity on T2-weighted sequences, most frequently extending proximal to the lesion. Cysts are rare, in contrast to primary intramedullary neoplasm.

External beam radiation with or without concomitant corticosteroids has been the most effective method of treating ISCM. In a small group of selected patients, surgical resection seems be a reasonable option, especially in cases presenting with previously undiagnosed or limited primary tumors and rapid neurologic deterioration. Also, when the primary tumor is well known to be radioresistant, as in the case of melanoma or renal cell carcinoma, surgical decompression or subtotal resection would be indicated.

Patients with ISCM have a very short life expectancy; their median survival is 3 to 4 months from the time of diagnosis. Those with breast cancer as the primary source of ISCM, tend to do better than other types of cancer; their median survival is 13 months.

Chronic progressive external ophthalmoplegia

2010-07-26T16:00:00.000+02:00

Findings

The extraocular muscles are atrophic and to some degree show fatty replacement. No abnormal enhancement is present. The globes are intact bilaterally. The intraorbital fat appears slightly increased. There is bilateral orbital proptosis with both globes anterior to the interzygomatic line.

Diagnosis: Chronic progressive external ophthalmoplegia

Key points

Chronic progressive external ophthalmoplegia (CPEO) is characterized by slowly progressive paralysis of the extraocular muscles.
Mitochondrial myopathy usually associated with skeletal muscle weakness.
Presents with bilateral, symmetrical, progressive ptosis, followed by ophthalmoparesis months to years later.

Kearns-Sayre syndrome: Related mitochondrial myopathy with CPEO, onset before age 20 years, pigmentary retinopathy, and at least one of the following: cardiac conduction defects, CSF protein of greater than 100 mg/dL, and/or cerebellar syndrome.
KSS can include mental retardation, hearing loss, seizures, short stature, delayed puberty, and various endocrine disorders.
Frequency: Rare. Males=Females.

Imaging studies: MRI, CT, and ultrasound may show thin, symmetrical extraocular muscles in CPEO, in contrast to enlarged extraocular muscles sometimes seen with Graves disease.
Those with KSS and CPEO display a wide spectrum of MRI findings, including normal brain, diffuse atrophy, and T2 prolongation in subcortical cerebral white matter, cerebellar white matter, globi pallidi, thalami, and substantia nigra.
Diagnosis: Muscle biopsy is definitive test but PCR also shown to be conclusive.

Mesial temporal sclerosis with infarct of the parahippocampal gyrus

2010-07-16T16:00:00.001+02:00

Findings

There is expansion and abnormal FLAIR and T2 signal within the right hippocampal formation and parahippocampal gyrus. There is diffusion restriction of the parahippocampal gyrus.

Diagnosis: Mesial temporal sclerosis with infarct of the parahippocampal gyrus

Discussion

Mesial temporal sclerosis (MTS) is a poorly understood phenomenon involving atrophy and sclerosis of the hippocampus and adjacent structures, namely, the amygdala, parahippocampal gyrus, and uncus. MTS may be acquired in the setting of prolonged febrile seizures, status epilepticus, or cerebral ischemia. Histopathology demonstrates neuronal loss and fibrillary gliosis. There has been controversy regarding whether MTS is the cause or the result of temporal lobe epilepsy. However, there is a clear connection since the majority of temporal lobe resection specimens done for temporal lobe epilepsy demonstrate MTS. Approximately 15% of temporal lobe resection specimens exhibit both MTS and another lesion such as cortical dysplasia. Approximately 25% of patients are successful with medical therapy. The patient presented here had longstanding seizures and had a recent seizure which resulted in acute infarction of the parahippocampal gyrus. This may result from seizure related hypoxemia.

Radiologic overview

MR demonstrates increased T2 signal as a result of neuronal loss and gliosis. Increased FLAIR signal is also seen but caution is necessary as limbic structures all demonstrate slight hyper intensity on FLAIR. Magnetic resonance spectroscopy can be used to evaluate MTS since interictal N- acetyl aspartate (NAA) is reduced in the ipsilateral temporal lobe compared with the uninvolved temporal lobe. Lactate and lipid peaks may be increased if scanned within 24 hours of seizure. Nuclear medicine studies demonstrate reduced activity if injected interictally and increased activity if injected ictally.

Fogging

2010-07-14T16:00:00.003+02:00

Findings

Interval near normalization of hypo densities in the right posterior cerebral artery distribution and right thalamus in the area of previously noted infarction. This is likely represents fogging secondary to luxury perfusion. Areas of increased density may represent laminar necrosis and petechial hemorrhage.

Diagnosis: Fogging

Following infarction, there may be normalization of previous hypo density secondary to luxury perfusion. This typically occurs 2-4 weeks following the acute event. If given contrast, the area will intensely enhance homogeneously. The fogging effect occurs during the resorption stage when macrophages phagocytize necrotic material. There is loss of edema and associated mass effect. As the phagocytized material is altered and the macrophages later exit, the infarcted area becomes increasingly hypodense and finally cystic. The fogging effect is to be distinguished from the normalization of density in a low density infarct secondary to the administration of intravenous contrast.

Methylamalonic acidemia

2010-07-07T16:00:00.002+02:00

Findings

There are oblong areas of hypointense T1, hyperintense T2 signal in the bilateral globus pallidus (Figure 1 and Figure 2). Figure 3 is a FLAIR image which does not demonstrate edema in this region. Figure 4 is a diffusion weighted image which does not show restricted diffusion, essentially excluding acute infarction.

Diagnosis: Methylamalonic acidemia

Inborn disorders of amino acid metabolism may commonly present with vomiting, feeding difficulties, lethargy, dehydration and metabolic acidosis. Neurologic symptoms include seizures, hypotonia, spasticity, developmental delay, mental retardation, and movement disorders often prompting evaluation with MR imaging.

Briefly, isoleucine, valine, methionine, and threonine are normally converted to propionic acid, methylmalonic acid, and succinic acid, the last step of which requires methylmalonyl CoA mutase and a coenzyme, adenosyl cobalamine. A deficiency in either the enzyme or coenzyme, in an autosomal recessive manner, results in the accumulation of methylmalonic acid. This build up results in the inhibition of succinate dehydrogenase; this enzyme facilitates mitochondrial aerobic glucose oxidation. The globus pallidus is particularly sensitive to mitochondrial dysfunction.

Deficiency in methylmalonyl CoA mutase generally produces earlier onset of symptoms and a more severe course with a mean survival time of 1.5 to 6.4 years.

Neuroimaging in these patients ranges from normal, with a subtle MR spectroscopy finding of elevated CSF lactate, to chronic infarction in the globus pallidus. In general, prominence of the ventricles and sulci with delayed white matter myelination may be seen. In our case, the patient was found to have chronic infarctions of the bilateral globus pallidus without additional parenchymal findings. In cases of suspected methylmalonic academia, correlation with genetic studies may be confirmatory.

Diving Ranula

2010-06-30T16:00:00.000+02:00

Findings

Figure 1 and Figure 2 Axial contrast-enhanced CT demonstrates a thin-walled, well-defined hypodense lesion in the right sublingual space (Figure 1) which herniates posteriorly into the submandibular space (Figure 1). This lesion also tracks into the sublingual space lateral to the right genioglossus muscle (Figure 2). It is located anterior and lateral to the right internal and external carotid arteries and effaces the submandibular gland.

Diagnosis: Diving Ranula

A diving ranula is an extravasation pseudocyst of a simple ranula in the sublingual space rupturing out into the submandibular and or parapharyngeal space. It originates from trauma or inflammation of the sublingual gland or minor salivary glands in the sublingual space. With obstruction of the gland duct, the duct dilates and eventually ruptures, allowing its secretions to leak into the surrounding soft tissue.

CT is the imaging study of choice. On CT, the lesion demonstrates water content and thin walls with subtle or no wall enhancement. If the lesion is infected, it may show thick, enhancing walls. The characteristic shape is a collapsed cystic portion in the sublingual space - “tail sign,” with its head extending into the submandibular space. The sublingual spaces are located on the floor of the mouth on either side of the midline genioglossus muscles. They are separated from the submandibular space by the mylohyoid muscle that extends from the medial inferior aspect of the mandible to the hyoid bone. Thus, the sublingual space is superomedial to the mylohyoid muscle and the submandibular space is inferolateral to the muscle. Ultrasound and MR can also be used to characterize these lesions. Ultrasound demonstrates a well-defined hypoechoic mass in the sublingual and submandibular space. MR images show the lesion with signal intensity of water, though if infected, signal intensity can vary according to the protein content or presence of hemorrhage with some wall enhancement.

The differential diagnosis would include epidermoid or dermoid cyst, lymphangioma or cystic hygroma, abscess, submandibular gland cyst (mucocele), and second branchial cleft cyst. These lesions differ in appearance on CT.

The treatment of a diving ranula is removal of the ipsilateral sublingual gland via the cervical or intraoral approach. It is not necessary to excise the pseudocyst since it puts the surrounding structures at risk for damage. Biopsy can be done to confirm the diagnosis.

Primary osteosarcoma of the mandible

2010-06-29T16:00:00.001+02:00

Findings

There is destruction of the vertical ramus of the mandible on the left side with associated periosteal reaction and osteoid matrix (Figure 2 and Figure 3). Multiple lamellae are seen radiating from the lesion giving it a sunburst appearance. Also there is extension into the soft tissue of the face (Figure 1).

Diagnosis: Primary osteosarcoma of the mandible

Malignant tumors of the mandible can be grouped as odontogenic and non-odontogenic. Examples of non-odontogenic solid malignant tumors include sarcomas, metastases, multiple myeloma, lymphoma/leukemia, and squamous carcinomas. Osteosarcomas of the mandible are rare non-odontogenic tumors and account for 5-13% of all osteosarcomas.

Osteosarcomas of the jaw generally peak during the 3rd or 4th decade, as opposed to osteosarcomas of long bones which peak during adolescence. There is no conclusive gender predilection. It can be secondary to Paget disease, fibrous dysplasia and irradiation to the jaw. Clinically the patients present with painful jaw swelling.

Typical osteosarcomas show matrix mineralization, which may be osteoid or chondroid, with associated bone destruction and soft tissue extension. With large tumor size these signs are identified on a plain radiograph, and CT scan helps in describing the extent of involvement. For cases presenting early CT helps in identifying those missed with conventional radiography. Differentiating osteosarcomas from chondrosarcomas can be troublesome radiologically and sometimes even histopathologically; however chondrsarcomas are even rarer in the head and neck region.

Histologically, this tumor is less aggressive and less frequently high grade as compared to its conventional counterpart in the long bones. The spread of the disease to the cervical lymph nodes is seldom seen.

Osteosarcoma of the jaw should be treated with radical surgery as the primary modality. The single most important factor in curative therapy for osteosarcoma of the jaw is its amenability to radical resection with clear margins. Neoadjuvant chemotherapy is not used as a routine as against osteosarcoma of long bones. There is no general consensus over the role of radiation therapy in management of patients. In one study Delgado, et al. reported that when surgical margins are not free of disease, the use of radiation does not improve the outcome.

Trigonocephaly

2010-06-23T16:00:00.001+02:00

Findings

CT 3D surface reconstructions show near-complete fusion of the metopic suture with trigonocephaly and "beaking" of the frontal bone along the midline. The sagittal, lambdoid, and coronal sutures are normal.

Diagnosis: Trigonocephaly

Craniosynostoses are calvarial dysmorphsims that result from premature closure of one or more sutures. Trigonocephaly, which involves the metopic suture, comprises less than 10% of all forms of craniosynostoses. It manifests prominent frontal keel, narrow forehead, and hypotelorism, which produces the appearance of a triangular skull. 3D CT reconstructions of the skull are well-suited for imaging the cranial sutures and osseous deformities. Trigonocephaly usually only poses an aesthetic concern and is amenable to reconstructive surgery. This craniosynostosis is infrequently associated with intracranial pathology or genetic disease such as Opitz "C" syndrome.

Orbital Dermoid

2010-06-07T16:00:00.000+02:00

Findings

Figure 1 and Figure 2: Ovoid well-circumscribed ventromedial left orbital extraconal mass resulting in mass effect on the intraorbital contents displacing the globe laterally, demonstrating nonaggressive features. Internal areas of fat attenuation.

Figure 3and Figure 4: Ovoid well-circumscribed mass centered in the post-septal, extraconal left orbit which exerts mass effect on the left globe, displacing it laterally. Signal characteristics of the lesion are most consistent with an intraorbital dermoid, including fat signal layering within the nondependent portion of this predominantly cystic lesion. This fat floats on underlying proteinacous cystic material.

Diagnosis: Orbital Dermoid

Patients with this diagnosis generally complain of an orbital mass, which may be visible on physical examination. Growth of these lesions is generally slow. In adults, dermoids may become symptomatic for the first time and grow considerably over a year. Based on this fact, some authors have concluded that these lesions may be dormant for many years and/or have intermittent growth, such as in our case example.

Dermoids are the most common benign congenital lesion of the orbit, accounting for 1-2% of all orbital masses. Dermoid and epidermoid cysts are examples of choristomas, tumors that originate from aberrant primordial tissue. These tumors contain normal-appearing tissue in an abnormal location. As two suture lines of the skull close during embryonic development, dermal or epidermal elements are pinched off and form cysts, which are adjacent to the suture line. Approximately 50% of these tumors that involve the head are found in or adjacent to the orbit. They arise most often in the superolateral portion of the orbit at the frontozygomatic suture. They can also arise inferiorly, posteriorly, or medially (as in our case example). These lesions are extraconal and displace the globe. If the displacement is great, interference with vision by compression of the optic nerve may result or ocular motility may be disturbed, typically resulting in diplopia.

On MR the diagnosis is usually clinched with high signal on T1WI in the region which suppresses with fat saturation techniques. Fat may be seen floating in cystic fluid on T1WI.

These tumors are most often noted in young children; however, they may appear or grow at any age. In adults, they are more likely to displace the globe, possibly growing or eroding their way into adjacent

Skull base Langerhans cell histiocytosis (LCH)

2010-05-25T16:00:00.001+02:00

Findings:

Figure 1and Figure 2: There is diffuse sclerosis of the left mastoid with near complete opacification of the mastoid air cells.
Figure 3 and Figure 4: There is diffuse sclerosis of the mastoid with a soft tissue thickening identified in the cavernous sinus. There is additional dural extension suggested along the left leaf of the tentorium.

Diagnosis: Langerhans cell histiocytosis (LCH), skull base

Langerhans cell histiocytosis (LCH) is the term used to describe the spectrum of diseases characterized by proliferation of specialized bone marrow-derived dendritic cells, called Langerhans cells (LC) with bone and/or soft tissue involvement. Although the etiology and pathogenesis of LCH is poorly understood, studies suggest that it is a reactive disease caused by immune dysregulation. The disorders once collectively called Histiocytosis X (eosinophilic granuloma, Hand-Schüller-Christian disease, and Letterer-Siwe disease) are now part of this category. LCH is defined in terms of whether it involves a single site, multiple sites, a single organ, or multiple organs. Prognosis and treatment are closely linked to the extent of disease at presentation and whether or not “risk” organs (ie: liver, spleen, lung, bone marrow) are involved. In general, patients with LCH localized to the bone have a favorable prognosis whereas patients with multisystem involvement incur a poor prognosis.

Langerhans cell histiocytosis of the bone is a relatively rare disorder with an incidence of one case per 2 million persons per year. The skull is the most commonly involved bony site in the pediatric age group. Otologic involvement usually occurs during the course of multisystemic disease, and may be the only symptom in up to 25% of patients. Because the otologic symptoms are similar to otomastoiditis, diagnosis of LCH of the skull is often delayed. The most frequent otologic symptom is otorrhea resistant to medical treatment. Other findings include mastoid swelling, aural polyps, periauricular eczema, sagging of the canal wall skin from erosion of the posterior bony external auditory canal, conductive hearing loss, and otalgia. Neurosensorial deafness, vertigo from involvement of bony labyrinth, and paralysis of cranial nerves (particularly VII and VIII) have been described. The classic clinical profile is a young man with otalgia, otorrhea, and post-auricular mass. If the diagnosis is suspected, a full examination and work-up is warranted to exclude the possibility of multisystemic or multiostotic disease.

The best imaging modality to diagnose LCH of the skull base is dedicated temporal bone CT. The skull base may show focal or diffuse bone destructive change and may present as: 1) sharply-defined “punched out” appearance, 2) irregular sclerotic lesions or 3) fragments of bone within soft tissue component. Other locations that are affected include the petrous apex, mandible, maxilla, and vertebral body. Ossicular and otic capsule destruction are common. Bilateral disease occurs in up to 30% of patients. The radiologic differential diagnosis for LCH of the skull base includes mastoiditis, cholesteatoma, cholesterol granuloma, and rhabdomyosarcoma. Rhabdomyosarcoma may exactly mimic unilateral LCH- biopsy may be required to differentiate the two entities.

Contrast-enhanced examination may help differentiate inflammatory mastoid lesions from LCH. Findings include a heterogeneously enhancing mass in the temporal bone, including mastoid complex, middle ear, extracalvarial, intracranial, and extra-dural compartments. The skull base tends to show a variable amount of enhancing soft tissue. On MR, T1 weighted images reveal iso- to hypointense mastoid, middle ear or skull base mass. T2 weighted images reveal hyper- to isointense soft tissue mass. Contrast-enhanced T1 weighted images show a heterogeneously-enhancing mastoid, middle ear, or skull base mass. MR may be obtained to delineate boundaries of soft tissue component which generally displays poorly defined borders.

The prognosis of LCH localized to the temporal bone is excellent, with a cure rate of 90%. The soft tissue component resolves initially, followed by reossification of the bone lesion. The treatment of choice for LCH localized to the mastoid-middle ear consists of surgical curettage or mastoidectomy. Low dose radiotherapy is used for larger, destructive lesions. Systemic disease is treated with chemotherapy in combination with radiation therapy.

Multiple bilateral infarcts secondary to IV drug abuse-related cerebral vasculitis

2010-05-24T16:00:00.002+02:00

Additional clinical history: Woman in acute heroin withdrawal who also has bilateral lower extremity weakness.

Findings:

Brain MRI shows restricted diffusion within the bilateral parietal and occipital lobes as well as over the motor cortex of the frontal lobes bilaterally, left greater than right. T2 prolongation is noted in all the locations where restricted diffusion is seen. Coronal and sagittal reformatted CTA images show areas of subtle beaded appearance of arteries, with focal narrowing and dilatation.

Diagnosis: Multiple bilateral infarcts secondary to IV drug abuse-related cerebral vasculitis

Key points

Increased T2 signal lesions with restricted diffusion have a broad differential
Clinical history, distribution (vascular territories involved, unilateral vs. bilateral), number (single vs. multiple), the presence or absence of mass effect, and the presence or absence of a peripheral ring or central necrosis are key diagnostic clues.
Abscesses may be single or multiple, may be unilateral or bilateral, often have a peripheral ring, and often display mass effect.
Tumors often have mass effect, often have a peripheral ring, may be single or multiple, may be unilateral or bilateral, and may show central necrosis.
Hemorrhage is often in the subdural or subarachnoid space, but may be intraparenchymal, especially if there is history of head trauma or associated fracture.
In acute infarct, there is no mass effect, no peripheral ring, and no central necrosis and the lesions are usually in a single vascular distribution and are usually- but not always- unilateral.
Examples of bilateral acute infarcts, as seen in this patient (note multiple bilateral lesions without mass effect, peripheral ring or central necrosis), are watershed infarcts occurring in typical watershed zones and infarcts occurring secondary to cardiac emboli or vasculitis, both of which are not distributed with respect to single vascular territories (as in this patient).
Besides IV drug abuse (as in this patient), cerebral vasculitis with secondary infarct can be seen in bacterial meningitis, tuberculous meningitis, viral, mycotic, syphilitic or post radiation arteritis, cell mediated arteritis, collagen vascular disease, sarcoid, Wegener's granulomatosis, and Moyamoya disease.

Focal cortical dysplasia

2010-05-17T16:00:00.002+02:00

Findings:

Figure 1 and Figure 2: Axial FLAIR and T2W MR images demonstrate blurring of the grey-white junction with high signal intensity in the subcortical white matter of the right frontal lobe. Adjacent cortical ribbon thickening is also present. These findings are characteristic of focal cortical dysplasia.

Diagnosis: Focal cortical dysplasia

Focal cortical dysplasia (FCD) is a congenital disease in which the neurons arrange abnormally in focal areas of the cerebral cortex. It is a common cause of intractable and drug resistant epilepsy, and while seen mostly in the pediatric population, it is not uncommon to see the disease manifest itself in adulthood. Radiologic diagnosis is important for pre-surgical planning and can have prognostic implications.

FCD can be further sub-typed based on histopathology. In Type I FCD there is architectural distortion of the cerebral cortex alone without any abnormal cells. In Type II FCD, however, pathology will demonstrate both architectural distortion and dysmorphic neurons. This includes the characteristic elliptically shaped neuron with a displaced nucleus and lack of axons, known as the “balloon cell”. While the pathologic diagnosis is made retrospectively, clinically those with Type I FCD generally are responsive to medical therapy, while those with Type II FCD are resistant.

Regardless of the pathologic type of FCD, patients that demonstrate preoperative imaging findings tend to have a better outcome after surgery than those who do not demonstrate any findings. The characteristic MR abnormalities in FCD include blurring of the grey-white junction, abnormal high T2 signal in the subcortical white matter, and adjacent focal cortical thickening. Often these findings are very subtle and may not be detected on MR imaging alone. In such cases MR/FDG-PET fusion has been utilized for more sensitive detection. Surgery is the mainstay of treatment for these patients.

Extra: Balloon cells are large elliptical shaped cells with displaced nuclei and are characteristic of focal cortical dysplasia.

Poorly differentiated orbital malignant lymphoma

2010-05-13T16:00:00.000+02:00

Findigs:

Figure 1: Axial CT through the orbital floors at the level of the inferior orbital foramen demonstrates an erosive mass, containing calcifications, with expansion through the floor of the orbit and into the maxillary sinus.
Figure 2: Contrast enhanced coronal CT image demonstrates a heterogeneously enhancing, soft tissue mass involving the floor of the orbit, with bony invasion.

Diagnosis: Poorly differentiated orbital malignant lymphoma (Non-Hodgkin's type) (biopsy proven)

In the adult population the differential diagnosis of malignant orbital tumors differs from that of children. Whereas, carcinoma is the frequently enountered in adults (often from contiguous spread from the paranasal sinus, etc), metastatic neuroblastoma is the more frequently encountered malignant neoplasm in children.

Neoplasms of the paranasal sinuses are uncommon, but frequently extend to involve the orbit when they do occur. Benign tumors tend to push the periorbital tissues aside, while malignant lesions tend to invade the periosteum.

Evaluation of the paranasal sinus mass is best done utilizing multidetector CT, because of its ability to detect bony destruction and possible intracranial extension of disease. CT usually demonstrates a homogeneous mass with well-defined borders that demonstrates heterogeneous enhancement.

Lymphoid tumors are one of the most common orbital tumors despite the orbit not containing lymph nodes or a well defined lymphatic vasculature. Ocular malignant lymphomas are uncommon. The incidence ranges from 1-4%. Involvement of the orbit as a presenting sign is rare and few such cases are seen in the literature. Although most orbital lymphomas are localized to the orbit at diagnosis, many patients will develop systemic lymphoma over time. Orbital lymphoma is an adult disease, usually presenting in patients between the age of 50-70 years. The course is usually of an anterior mass that causes painless proptosis over several weeks to months.

Radiation therapy is the mainstay of treatment since surgical resection plays a limited role. Response rate and prognosis depends upon cell type, the extent of disease and whether the orbital disease represents the primary site or the site of spread of disease from an extra-ocular primary. Five year survival rates range from 54-78%.

Parapharyngeal abscess

2010-05-10T16:00:00.000+02:00

Findings

The right parapharyngeal space contains a hypo attenuating collection near simple fluid in attenuation. Collection extends from just below the level of the hyoid to just below the right mandibular condyle, is anterior to the carotid space inferiorly, anteromedial to the carotid space superiorly. No significant rim enhancement. No inflammatory fat stranding is present. Right submandibular gland is along the anterolateral margin of this collection. Multiple prominent lymph nodes were visible.

Differential diagnosis:
- Abscess
- Lymphangioma
- Second branchial cleft cyst
- Ranula

Diagnosis: Parapharyngeal abscess

Aplasia of right submandibular gland with compensatory parotid and sublingual gland hypertrophy

2010-05-07T16:00:00.005+02:00

Findings

There is aplasia of the right submandibular gland, and severe atrophy of the left submandibular gland. There is hypertrophy of the sublingual glands bilaterally, with herniation of the right sublingual gland through the mylohyoid boutonniere. There is also hypertrophy of the parotid glands bilaterally, without a discrete mass and without ductal dilatation or sialolithiasis.

Differential diagnosis:
- Parotiditis
- Parotid gland tumor
- Parotid hyperplasia
- Lymphadenopathy
- Amyloidoma

Diagnosis: Aplasia of right submandibular gland with compensatory parotid and sublingual gland hypertrophy

Key points

Congenital absence of a major salivary gland is extremely rare. It is reported to be associated with other congenital craniofacial anomalies and absence of all four major salivary glands is the most common pattern.
Most patients are asymptomatic. Hypertrophy of other salivary glands may result in an asymptomatic neck mass.
Symptoms such as dysphagia, xerostomia, dental caries, and local pain have been reported. Symptomatic patients generally have aplasia of multiple glands.
Agenesis of the major salivary glands may be associated with other first and second branchial arch defects.
The cause is not known , but is thought to be a result of a fetal development disturbance in the 4th-8th weeks of gestation
Enlargement of the other salivary glands is felt to be compensatory in etiology.

IVC thrombosis with enlarged epidural veins causing a lumbar radiculopathy

2010-05-03T16:00:00.001+02:00

Findings

Figure 1 and Figure 2: Sagittal T1 and T2 weighted images reveal the presence of signal in the IVC and iliac veins indicative of thrombus. Prominent epidural veins are appreciated here as well.
Figure 3 and Figure 4: Axial T2 weighted sequences reveal enlarged epidural veins as demonstrated by prominent flow voids in the epidural space. Note absent flow void in the IVC and iliac veins. Normal flow voids are seen in the associated arterial structures on these images.

Diagnosis: IVC thrombosis with enlarged epidural veins causing a lumbar radiculopathy

Lumbar radiculopathy and low back pain is a frequently encountered complaint in the general population. The most common etiology is structural spine disease, including disc herniation and spondylosis. However, nonstructural diseases, such as cytomegalovirus polyradiculopathy in immunocompromised individuals as well as other infections, neoplasms, and inflammatory conditions have also been shown to cause lumbar radiculopathy. Vascular causes are unusual as patients with vascular pathology tend to present with myelopathy.

Enlarged epidural veins are commonly a result of arteriovenous malformations, fistulas, and varicose veins. In the cervical spine, the epidural veins function as collateral pathways and become enlarged as they receive more blood flow when the jugular veins are compromised. Similarly, it can be inferred that in the case of an IVC obstruction or occlusion, the lumbar epidural veins become enlarged by the same mechanism; when IVC blood flow is compromised, blood is able to return to the heart through the azygos and hemiazygos veins via collateral pathways including the epidural venous system. While many epidural veins become enlarged as a result of this process, the vein implicated in causing the radiculopathy is the vein below the pedicle. This vein lies in close proximity to the existing nerve root and as the vein becomes larger, it will impinge directly upon the nerve root leading to the radiculopathy. Therefore, the best way to eliminate the radicular symptoms is by treating the underlying cause of the IVC thrombosis.

Risk factors for the development of IVC thrombosis and venous thromboembolism (VTE) include hypercoaguable states such as factor V Leiden mutation, prothrombin gene mutation, protein S deficiency, protein C deficiency, antithrombin deficiency, and dysfibrinogenemia. Acquired risk factors include a prior thrombotic event, recent major surgery, presence of a central venous catheter, trauma, immobilization, malignancy, pregnancy, oral contraceptives, heparin, myeloproliferative disorders, and antiphospholipid syndrome.

Pars flaccida cholesteatoma

2010-04-22T16:00:00.000+02:00

Findings

There is an 8mm mass in Prussak’s space with erosion of the malleus and scutum.

Differential diagnosis:
- Pars flaccida cholesteatoma
- Cholesterol granuloma
- Paraganglioma
- Pars tensa cholesteatoma

Diagnosis: Pars flaccida cholesteatoma

Key points

A pars flaccida cholesteatoma often occurs when a patient has chronic middle ear inflammation and/or TM perforation. The cholesteatoma forms when there is an accumulation of stratified epithelial cells in Prussak's space. The cholesteatoma can be seen in all age groups, but tend to be more aggressive in children. Patients can present with aural discharge, conductive hearing loss, and otalgia. Early treatment with surgery can preserve hearing.

Radiologic overview of the diagnosis

A pars flaccida cholesteatoma appears as a mass in Prussak's space with erosion of the scutum and/or adjacent ossicle. Ossicle erosion is seen ~70% of the cases. There is no enhancement of the cholesteatoma itself, though surrounding granulation tissue may enhance.

High resolution temporal bone CT is the best modality to evaluate a suspected cholesteatoma. A pars tensa cholesteatoma is far less common and involves the sinus tympanum. A cholesterol granuloma appears blue on otoscopy and may have similar bony erosions as that of a cholesteatoma. A paraganglioma appears as a cherry red mass on otoscopy and usually does not erode bone.

In this case, there is an 8mm mass in Prussak's space with erosion of the malleus and scutum.

Leptomeningeal carcinomatosis from esophageal adenocarcinoma

2010-04-19T16:00:00.010+02:00

Findings

Figure 1, Figure 2, Figure 3, and Figure 4: Postgadolinium T1 weighted images demonstrate linear contrast enhancement in the subarachnoid space, most notably interdigitating between the folia of the superior cerebellum and in the sulci of the parietal and occipital lobes. The T1 weighted precontrast images are unremarkable.
On FLAIR imaging in Figure 5, there is corresponding hyperintensity in the subarachnoid space.
Chest TC (not shown) demonstrates a high-attenuation central mass within the esophagus, which is expanding the lumen.

Diagnosis: Leptomeningeal carcinomatosis from esophageal adenocarcinoma

The leptomeninges consist of two layers; the pia mater and the arachnoid mater, which enclose the subarachnoid space and the CSF. The leptomeninges are a frequently missed site of metastastic involvement, especially for non-hematologic primary malignancies. There are many proposed routes of entry for tumor cells into the CSF including hematogenous spread via the arachnoid vessels or choroid plexus, direct extension from the skull, vertebrae, dura or retrograde perineural spread via the peripheral or cranial nerves. Once tumor cells reach the CSF, rapid dissemination can occur.

Up to 50% of patients with leptomeningeal metastases present with signs of increased intracranial pressure and/or hydrocephalus including headaches, back pain, nausea, vomiting and dizziness. These symptoms are most likely secondary to obstruction of CSF flow by tumor cells. Other clinical manifestations include seizures, focal cranial nerve deficits and meningeal signs such as nuchal rigidity and photophobia.

CSF cytology is the definitive test for diagnosis of leptomeningeal involvement. However, while highly specific, cytology is often falsely negative. The accuracy of a single lumbar puncture is approximately 50%, which increases to 90% with three LPs. Cytology remains negative in 10-20% of patients, presumably in situations in which the malignant cells are more adherent to the leptomeninges.

Contrast enhanced MR imaging is the diagnostic test of choice as an adjunct to CSF cytology when leptomeningeal metastases are suspected. Gadolinium enhanced MRI is more sensitive than a single lumbar puncture, but is less specific. The most common imaging findings include diffuse leptomeningeal contrast enhancement, multiple masses or nodules within the subarachnoid space and/or hydrocephalus. The diffuse leptomeningeal enhancement pattern has been referred to as sugar-coating or zuckerguss (German for icing or sugar-coating). Studies have shown that contrast-enhanced T1-weighted MR imaging is the most sensitive single sequence for detection of leptomeningeal metastases.

Prognosis for leptomeningeal metastases is poor. Without treatment, the average survival is 1-2 months. Treatment options include corticosteroids, intrathecal chemotherapy and radiation therapy. Despite aggressive therapy, the median survival in most randomized-controlled trials is 3-4 months.

Acute infarction secondary to occlusion of artery of Percheron

2010-04-06T16:00:00.001+02:00

Findings

Figure 1: Coronal DWI image demonstrates restricted diffusion within bilateral medial inferior thalami and superior midbrain.
Figure 2: Coronal DWI image, obtained 12 days later demonstrates relatively decreased diffusion hyperintensity.
Figure 3: Coronal post-contrast coronal T1 weighted image demonstrates new enhancement involving bilateral inferior medial thalami and superior midbrain, secondary to breakdown of blood-brain barrier.
Figure 4: Diagram illustrating normal paramedian thalamic mesencephalic arterial supply, with many perforating vessels arising from bilateral P1 segments of the PCA. (Reprinted with permission from AJNR)
Figure 5: Diagram illustrating the variant, “artery of Percheron” a single perforating blood vessel arising from one P1 segment.

Diagnosis: Acute infarction secondary to occlusion of artery of Percheron

The thalami and the midbrain receive their blood supply from both the anterior and posterior circulations, and several variations in this supply are known to exist. The anterior circulation usually supplies the anteroinferior aspects of the thalami and midbrain, with thalamoperforator arteries arising from the posterior communicating arteries. The posterior circulation usually supplies the medial aspects of the thalami and midbrain via branches arising from P1 segments and the lateral and superior aspects with branches arising from P2 segments of the posterior cerebral arteries. Most of the perforating branches from the P1 segments have an ipisilateral distribution (78%); bilateral or even contralateral distributions may be observed in 22% of individuals.

Percheron studied the variations of this arterial supply and its distributions and described three different variations involving the paramedian thalamic-mesencephalic arterial supply: (1) small branches arising from both P1 segments, (2) an asymmetrical common trunk arising from a P1 segment (this variation is called the artery of Percheron), (3) or an arterial arcade emanating from an artery bridging the two P1 segments. In the second type, a common trunk arising from one of the P1 segments provides bilateral distribution. Occlusion of this trunk results in bilateral infarctions in the middle aspects of thalami and brain stem.

The thalami contain strategic nuclei and integrate several important cortical functions. Thus, infarcts at the mesencephalic-diencephalic junctions may result in complex clinical syndromes, with patients exhibiting a wide range of symptoms varying from motor deficits to behavioral and sensory alterations. The third nerve palsy demonstrated in this particular patient may have been due to involvement of the midbrain at the level of the Edinger-Westphal nucleus.

Performing conventional angiography may not be indicated, because lack of visualization of the artery does not exclude its presence (because it is occluded).

Fahr disease

2010-03-30T16:00:00.000+02:00

Findings

Figure 1 and Figure 2: Select axial non-contrast CT images demonstrate dense symmetric calcification in the basal ganglia (Figure 1) and dentate nuclei (Figure 2). Cortical atrophy is also seen.
Figure 3: Axial T1-weighted image demonstrates symmetric cerebellar hyperintense foci corresponding to calcification seen on CT.

Diagnosis: Fahr disease (Idiopathic familial basal ganglia calcification)

Fahr disease (Idiopathic familial basal ganglia calcification, bilateral striopallidodentate calcification, Familial cerebrovascular ferrocalcinosis) is a rare disorder characterized by idiopathic basal ganglia calcification with associated cognitive and neurobehavioral manifestations.

Calcification is found primarily in the globus pallidus, but the putamen, caudate, thalamus, cerebellum (especially dentate nucleus), corona radiata, and subcortical white matter can also be affected. There are no detectable abnormalities of calcium or phosphate metabolism. Patients develop progressive parkinsonism, dystonia, and neuropsychiatric disturbance.

There is a bimodal pattern of onset. Those affected in early adulthood may be asymptomatic in the first two decades, despite the presence of basal ganglia calcification. The disease presents with schizophreniform psychosis. A second peak of onset is seen in late middle age, when patients present with subcortical dementia or Parkinsonian symptoms, which are permanent and progressive. Paroxysmal dystonic choreoathetosis and seizures are common. Eventually patients develop symmetrical spastic paralysis progressing to a decerebrate state.

The disease process involves the deposition of calcium in the walls of the capillaries and larger arteries and veins. Other elements, including magnesium, zinc, aluminum, and iron have also been found deposited in the vessels. No definitive treatment is available.

In studying a three-generation family with an autosomal dominant form of the disease, Geschwind et al, established that the chromosomal locus, IBGC1, lies on chromosome 14, and found that this form of the disease demonstrates genetic anticipation. Autosomal recessive inheritance has also been documented. The disease demonstrates variable expressivity.

CT images demonstrate bilateral, symmetric calcification in the globus pallidus, cerebellum, and white matter. On T1-weighted MR images calcifications are hyperintense, while on T2-weighted and FLAIR images, calcification may be hypo- or hyperintense. T2 hyperintense regions in the white matter, which do not correspond to calcification can also be seen. This finding may reflect progressive inflammation.

Differential diagnosis for inherited and acquired basal ganglia calcification
Postinflammatory causes:
- Tuberculosis
- Toxoplasmosis
- Cystercercosis
- Congenital HIV

Endocrine causes:
- Hyperparathyroidism
- Hypoparathyroidism
- Pseudohypoparathyroidism
- Hypothyroidism

Congenital causes:
- Tuberous sclerosis
- Down syndrome
- MELAS
- Neurofibromatosis

Toxic causes:
- Exposure to carbon monoxide
- Chemotherapy
- Radiation therapy
- Lead intoxication

In addition, incidental basal ganglia calcification is seen frequently on CT imaging in patients over the age of 50.

Mechanical thrombectomy of the MCA

2010-03-26T16:00:00.001+01:00

Findings

Figure 1: CT angiography of the head demonstrates a left MCA occlusion at the distal M1 area. There is visualization of distal vessels with filling by collaterals.

Figure 2, Figure 3, Figure 4, and Figure 5: CT perfusion images demonstrate increased transit time and poor flow in the left MCA territory. There is poor flow in the right posteroparietal region. There is generally preserved blood volume except for decreased volume in the left posterior watershed area. These findings are compatible with ischemia with some areas of infarct and fairly large area of preserved viability.

Diagnostic/therapeutic cerebral angiogram findings: Digital angiography confirms that the left M1 segment is occluded at its mid-portion (Figure 6). Subsequently, the Merci catheter is deployed in the region of the thrombus (Figure 7). Following Merci thrombectomy, there is recanalization of the left M1 segment of the middle cerebral artery (Figure 8).

Diagnosis: Mechanical thrombectomy of the MCA

Catheter-directed thrombectomy systems can be successfully applied towards salvaging areas of reversible ischemia detected on cerebral perfusion imaging.
The MERCI catheter thrombectomy technique involves insinuating the catheter’s coiled tip beyond the thrombus and then retracting the catheter, thereby extracting the clot material.

Until recent years, intravenous recombinant tissue plasminogen activator (TPA) administered within three hours following symptom onset was the only FDA approved treatment for acute stroke. However, mechanical thrombectomy has since emerged as an effective treatment option for acute cerebral ischemia. Indeed, satisfactory results have been achieved with mechanical thrombectomy in some patients that present beyond the time period for intravenous TPA administration has passed, up to about 8 hours. Specifically recanalization rates of nearly 70% have been reported using mechanical thrombectomy.

Various catheter-based devices and techniques have now been devised for mechanical thrombectomy in the cerebral arteries. Some of these include the use of a snare, the alligator retrieval system, the Phenox clot retriever, the Merci catheter, among others.

The Merci catheter thrombectomy technique consists of obtaining femoral artery access, guidewire insertion, and advancement of the catheter to the site of occlusion. Subsequently, the balloon is inflated and the coiled tip of the catheter is passed across the clot and engaged under angiography. The mesh helps trap thrombus material. Clot is retracted into the balloon guide catheter and out of the body. Finally, the balloon is deflated, thereby restoring blood flow.

The main complication of mechanical thrombectomy is intracranial hemorrhage, which occurs in an estimated 5 to 10% of patients.