Band heterotopia

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

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

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)

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

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