Labyrinthine ossificans

Findings

On the left, there is severe ossification and encroachment of the cochlea with extension to the vestibule and semicircular canals, which are also severely involved. The cochlear aqueduct is slightly stenotic. On the right, there is peripheral osseous hyper density of the cochlea with mild encroachment.

Differential diagnosis:
- Labyrinthine ossificans
- Cochlear aplasia
- Intravestibular schwannoma
- Cochlear otosclerosis
- Labyrinthine schwannoma


Diagnosis: Labyrinthine ossificans


Key points

Most common cause of acquired childhood deafness
Most common clinical presentation – bilateral sensorineural hearing loss 2-18 months after meningitis
May also occur after other infectious, inflammatory, trauma, or surgery
After meningitis or hematogenous infection – bilateral
After otitis media – unilateral
Rarely – severe vertigo
Suppurative membranous labyrinthitis starts inflammatory cascade which leads to fibrosis and eventually ossification
Dedicated IAC/temporal bone CT best for detection
Mild – mild increased haziness in the fluid spaces of the membranous labyrinth and prominent modiolus
Severe – complete obliteration of the membranous labyrinth with bony replacement of the fluid spaces
On MR, low signal bone encroaches (mild) or obliterates (severe), high signal fluid spaces of the membranous labyrinth
Importance – must identify cochlear labyrinthitis ossificans before cochlear implant so that it may be surgically treated
Treatment – cochlear implant, or labyrinthectomy for severe vertigo

Colloid cyst

Findings

The CT of the paranasal sinus shows a circumscribed hyper dense homogenous mass at midline anterior to third ventricle. The MRI of the brain shows an approximately 1 cm circumscribed mass location as above. Isointense on T1. Iso/slight hyper intense on T2. Hyperintense on FLAIR. No diffusion restriction or enhancement. Some heterogeneity of inferior margin (seen on sagittal). There is hydrocephalus of the left lateral ventricle.

Differential diagnosis:
- Colloid cyst
- Pseudocyst (CSF flow artifact)
- Choroid plexus papilloma
- Glioma
- Hamartoma
- Neurocysticercosis
- Granulomatous disease


Diagnosis: Colloid cyst


Colloid cyst

Not a true neoplasm; rather a remnant from embryonic endoderm
Contains variable contents including mucinous secretions and desquamated epithelial cells. This variability accounts for variable MRI signal characteristic
Usually present in 3rd to 4th decade
2% of all intracranial masses, 15-20% of all intraventricular masses
Only 10% show growth
Classic clinical scenario is acute onset headache (duet to acute obstruction and hydrocephalus) which is reproduced with tilting head forward (Brun phenomenon)
Fatalities reported due to this lesion (though not common)


Radiologic overview of the diagnosis

The location of this lesion is nearly pathognomonic = Attached to anterior/superior 3rd ventricular roof, wedged into foramen of Monro, with pillars of fornix draped around cyst.
Variable size at presentation, mean size = 15 cm
May be associated with ventriculomegaly

CT:
- 2/3 hyper dense, 1/3 iso- to hypo- dense (dependent on hydration state)
- Usually no enhancement, rarely rim enhances

MRI:
- T1WI usually hyper intense (2/3), 1/3 isointense
- T2WI majority isointense, but more variable, reflects hydration content of internal materials
- Can see fluid-fluid levels
- FLAIR: Does not suppress (hyper intense)
- DWI: No restriction
- Rare rim enhancement

Pituitary stalk interruption syndrome (PSIS)

Findings

Figure 1: Coronal T1-weighted non-contrast of the pituitary gland demonstrates complete absence of the anterior pituitary gland. The posterior pituitary gland is ectopic in location.
Figure 2: Sagittal T1-weighted noncontrast of the pituitary gland demonstrates complete absence of the anterior pituitary gland. The posterior pituitary gland is ectopic in location.
Figure 3: Contrast enhanced sagittal T1-weighted of the sella turcica demonstrates complete absence of anterior pituitary gland, truncated pituitary stalk and ectopic posterior pituitary gland.


Diagnosis: Pituitary stalk interruption (PSIS) syndrome


Pituitary stalk interruption syndrome, also known as pituitary stalk transection syndrome, is characterized by an (1) absent or hypoplastic adenohypophysis, (2) ectopic neurohypophysis, and (3) absent or hypoplastic pituitary stalk.

There are two proposed hypotheses for PSIS. The first one proposes that PSIS is an acquired injury caused by neonatal hypoxia, since there is a high association of PSIS with breech presentation and cesarean section delivery. This unexplained high incidence of breech deliveries associated with PSIS patients supports the traumatic hypothesis. However, high frequency of associated CNS malformations, such as coloboma, microcephaly, Arnold Chiari, microophthalmia, septooptic dysplasia, and corpus colossal agenesis, argues against a traumatic hypothesis. The alternative explanation is that there is failure of normal inductive events of the rostromedial neural fold during pituitary gland organogenesis and the high incidence of breech presentation can be explained by in utero hypotonia due to hormonal deficiency.

Clinically, presentation will depend on the extent of the hormonal deficiencies. Neonatal patients usually present with hypoglycemic seizure. Pediatric patients with isolated growth hormone deficiency present with variable delay in growth, while those with greater degree of hypoplasia of the pituitary stalk and anterior pituitary gland present with symptoms associated with panhypopituitarism early in life. Clinical suspicion of this syndrome is based on laboratory tests of low GH level, cortisol level, abnormal GH stimulation test, low FSH, LH, TSH and free T4. There is a high incidence of microphallus and cryptoorchidism in PSIS patients, which can be explained by the low levels of gonadotropins.

There is a male predominance with a male:female ratio of 3:1.

Imaging findings include an absent or hypoplastic anterior pituitary gland, most conspicuously seen on sagittal T1 or T2 weighted images. The pituitary infundibulum is either absent or truncated. In addition, the bright spot of the posterior pituitary gland, seen on T1 weighted sequence, is ectopic in location. The brightness of the posterior lobe does not change on a fat-suppression T1-weighted image.

Treatment consists of hormonal replacement.

Extramedullary hematopoiesis

Findings

There are at least three non-enhancing T1 mildly hypo intense, T2 hypo intense masses in the posterior epidural space of the mid thoracic spinal canal causing mass effect on the adjacent spinal cord. There is also abnormal T1 and T2 hypo intensity of the vertebral body marrow.

Differential diagnosis:
- Extramedullary hematopoiesis
- Epidural hematoma
- Epidural abscess
- Neurogenic tumor
- Lymphoma
- Metastases


Diagnosis: Extramedullary hematopoiesis


Key points

Extramedullary hematopoiesis (EH) is a compensatory response to deficient bone marrow blood cell production.
Either in response to continued RBC destruction (e.g. sickle cell disease, thalassemia, spherocytosis) or inability of normal RBC precursor to produce cells (e.g. iron deficiency, pernicious anemia, myelofibrosis, leukemia, lymphoma, diffuse osseous mets).
Liver and spleen most common sites followed by the spine. Other common sites include thymus, cardiac, adrenals, kidneys, lymph nodes, and GI tract.
Spinal involvement most common with thalassemia.
Epidural EH thought to arise from primitive rests in the dura mater or epidural space. Another theory attributes it to direct extension from vertebral bone marrow.
Typical imaging appearance is of a lobular multi-segmental mass in the mid thoracic posterior epidural space that is T1 isointense and T2 hypo intense to the cord with variable enhancement.
Cord and nerve root compression can occur.
Treatment: EH very radiosensitive with prompt response; surgery considered when severe symptoms or failed radiotherapy. Hydroxyurea and blood transfusions may also be used.

Multiple cavernous malformations (AKA cavernomas) with associated large hemispheric developmental venous anomaly (AKA DVA or venous angioma)

Findings

CT head: Multiple areas of intracranial hemorrhage in the left hemisphere. There is thrombosis of the superior sagittal sinus and a left cortical vein. Two focal hyper dense masses are seen in the left occipital lobe and the medial left temporal lobe.
MRI and MRV brain: Multiple intraaxial masses in the left cerebral hemisphere seen in the temporal lobe, basal ganglia, occipital lobe, and genu of the corpus callosum which show blooming artifact on gradient echo images, and a hypo intense rim on T2-weighted images. There is a large left hemispheric venous angioma with dilated medullary veins which drain to the internal cerebral vein best seen on post contrast images. The anterior superior sagittal sinus is hypoplastic or stenotic.
Cerebral angiogram: No evidence of aneurysm or AVM. There is a large left venous angioma draining the entire left hemisphere into the internal cerebral vein then to the vein of Galen. Left cortical vein thrombosis, nonocclusive posterior superior sagittal sinus thrombus, and absence of the anterior superior sagittal sinus.

Differential diagnosis:
- Multiple arteriovenous malformations
- Multiple cavernous malformations with large venous angioma and sagittal sinus stenosis and partial thrombosis
- Multiple cavernous malformations with venous stasis due to sinus stenosis and partial thrombosis
- Multiple hemorrhagic metastases with leptomeningeal enhancement
- Multiple calcified metastases and leptomeningeal enhancement
- Sturge Weber with arteriovenous malformations


Diagnosis: Multiple cavernous malformations (AKA cavernomas) with associated large hemispheric developmental venous anomaly (AKA DVA or venous angioma)


Key points

The diagnosis is favored over cavernomas with venous stasis because:
- There is a known association between cavernous malformations and developmental venous anomalies.
- The cerebral angiogram shows an embryologic drainage pattern.


Cavernous malformations

Clinical
- Presentation: Seizure 50%, neurologic deficit 25%
- Pathology: Collection of endothelial lined, blood filled vessels without intervening normal brain
- Genetics: Multiple cavernous malformations can be seen with an autosomal dominant chromosomal abnormality
- Prevalence: 0.5%
- 75% solitary, sporadic lesion
- 10-30% multiple, familial
- Hemorrhage rate: Sporadic 0.25-0.75%

- Associated anomalies:
Developmental venous anomaly
Superficial siderosis
Cutaneous findings: café au lait spots, cherry angiomas

Imaging:
- Cerebral angiography: Most common angiographically occult vascular malformation, i.e. not detectable. May be associated with a venous angioma
- MRI: Popcorn ball appearance; mixed signal intensity core with a hypo intense hemosiderin rim; prominent susceptibility artifact ("blooming"). Diffusion usually normal
- CT: Negative in 30-50%; may appear as an ovoid hyper dense lesion. 40-60% have Ca2+


Developmental venous anomaly (AKA venous angioma)

Clinical
- Embryology: Felt to be secondary to arrested medullary vein development resulting in persistence of large primitive deep embryonic white matter veins
- Most common vascular malformation at autopsy
- Usually asymptomatic
- 15-20% associated with cavernous malformations
- Radially oriented dilated medullary veins
- Hemorrhage risk increases with occlusion of the draining vein. Risk felt to be 0.15% per lesion/year
- Multiple can occur with blue rubber-bleb nevus syndrome

Imaging
- Prevalence: 2.5-9% of MRI scans
- Contain normal intervening brain
- Dilated medullary veins have the "medusa head" or umbrella-like appearance; located often at the angle of the ventricle; stellate, tubular vessels converse on a collector vein which drains into a dural sinus/ependymal vein
- Differential diagnosis includes dural sinus occlusion with venous stasis and collateral drainage.
- Cerebral angiography: Most common angiographically occult vascular malformation, i.e. not detectable; may be associated with a venous anomaly
- MRI:
T1 and T2 weighted images: Can be normal if small, or see flow void if large enough
T1+C: Stellate pattern of tubular vessels of strong enhancement draining to a collector vein to a dural sinus/ependymal vein
MRV: Demonstrates medusa head and drainage pattern
CT: Usually normal. Parenchymal hemorrhage if draining vein occluded

Squamous cell carcinoma of the external auditory canal

Findings

Figure 1, Figure 2, Figure 4, Figure 5 are axial and coronal T1 and T2 weighted images respectively. Figure 3 and Figure 6 are post contrast T1 weighted fat saturated images. A soft tissue mass is seen in the above images in the external auditory canal appearing isointense on T1 images and hyperintense on T2 images with post contrast enhancement. The middle ear is invaded with no intracranial extension. The internal carotid artery is uninvolved.

Differential Diagnosis:
- Squamous cell carcinoma of the external auditory canal
- Debris in the external auditory canal
- Malignant otitis externa
- External auditory canal cholesteatoma
- Keratosis obturans
- Medial canal fibrosis


Diagnosis: Squamous cell carcinoma of the external auditory canal


Carcinomas of the external auditory canal are rare and form less than 0.2% of head and neck malignancies. Various histological subtypes have been described, the commonest being squamous cell carcinoma followed by adenoid cystic carcinoma.

Squamous cell carcinoma of the external auditory canal is predominantly a disease of the elderly with slight male preponderance. Exposure to radiation therapy for head and neck malignancies, especially nasopharyngeal carcinoma, is a risk factor. The tumor is locally aggressive with a relatively lower tendency to metastasize.

Patients typically present with otorrhea, otalgia, and bloody discharge from the ear. Visible necrotic mass, swelling, tinnitus, hearing loss, facial palsy, otitis externa and otitis media are other presenting features.

Extent, description and staging of the tumor is based primarily on imaging as the region is inaccessible to a complete and satisfactory clinical examination. CT scan of the temporal bone is a routine investigation, and is done to look for bony erosion. Small tumor extent and more outer location of ear malignancy such as the auricle or external ear canal has better prognosis with a higher 5-year survival rate.

Surgical excision is the mainstay of management. There is no consensus over the surgical procedure and approaches vary from en bloc resection to piecemeal removal of the tumor. Invasion of the carotid, middle or posterior fossa renders the tumor inoperable. Any nodal involvement is regarded as advanced disease (stage III and IV) and changes the stage irrespective of the T status of the University of Pittsburgh TNM Classification.

In early stages the tumor is treated by en bloc resection, confirming negative margins, with post operative radiotherapy not offering a documented survival advantage over surgery alone. On the other hand, in advanced stages surgery is routinely followed by radiation and topical chemotherapy (5-FU mostly).

Right cerebellar encephalomalacia

Findings

There is increased signal in the right cerebellar hemisphere on T2 weighted images. On FLAIR images, there is decreased signal arising from the right cerebellar hemisphere secondary to fluid attenuation. There is also apparent diffusion restriction in the left cerebellar hemisphere on DWI and ADC map images. In fact the L side is the normal side.


Diagnosis: Right cerebellar encephalomalacia


Discussion

Encephalomalacia is usually a consequence of aging and/or brain insult, and in this case, the patient had a prior right cerebellar infarct. The brain parenchyma becomes atrophic and becomes replaced by CSF. Encephalomalacia usually does not cause acute symptoms and was likely not the cause of this patient's symptoms.


Radiologic overview

Diffusion weighted imaging is the most sensitive MR sequence to detect acute stroke. Changes in diffusion weighted images can be seen as early as 30 minutes after insult. At the cellular level, there is random movement and diffusion of water through cellular membranes. In tissues with greater water mobility, there is increased signal loss on diffusion weighted images. In stroke, there is a disruption of cellular membrane ion pumps, which leads to an influx of water into the intracellular space due to osmosis. Intracellular water does not move as freely as extracellular water and this decreased movement leads to increased signal on diffusion weighted images. An increased signal on diffusion weighted images alone is not sufficient to diagnose acute ischemia however, as tumor, infection and trauma can increase intra- and extra-cellular water leading to increased signal on DWI. The apparent diffusion coefficient map diminishes the increased signal associated with increased extracellular water and takes into account only the mobility of water. As the movement of water decreases in ischemic cells, the water diffusion coefficient decreases. This manifests as signal loss on ADC map images. Extracellular fluid on ADC map images will remain bright. Thus, acute ischemia is identified by increased signal on DWI and associated dark signal in the same region on ADC map. The use of DWI and ADC map images is sensitive (88-100%) and specific (86-100%) for acute stroke.

In this patient, there was a sequence of DWI images that demonstrated increased signal in the left cerebellar hemisphere. However, on ADC map images, there was no associated loss of signal. The adjacent right cerebellar encephalomalacia (and bright signal due to the high extracellular water e.g. CSF), gave the illusion of signal loss in the left cerebellar hemisphere. On T2 and FLAIR images, acute ischemia shows up as increased signal. In this case, there was no increased T2 signal throughout the brain parenchyma. The encephalomalacia in the right cerebellar hemisphere shows up bright on T2 weighted images due to CSF replacement of brain parenchyma.

Lymphangioma with components of hemangioma

Findings

Multilobular, infiltrative mass posterior to the lower cervical/upper thoracic spine, which is soft tissue density on CT and on MR is T1 iso intense to muscle, T2 hyper intense, homogeneously enhances, and shows evidence of flow voids. There is also enhancement of the adjacent spinous process.

Differential diagnosis:
- Hemangioma
- Lymphangioma
- Liposarcoma


Diagnosis: Lymphangioma with components of hemangioma


Key points

Endothelial malformations are currently divided into hemangiomas and vascular malformations.
Previously these lesions were categorized and named according to the channel size and contained fluid: i.e. capillary, strawberry and cavernous hemangiomas for blood containing lesions; and lymphangiomas or cystic hygromas for lymph containing lesions.
Vascular malformations are not true neoplasms and they are subdivided into high-flow and low-flow groups.
High-flow vascular malformations have an arterial component and include both arteriovenous malformations and arteriovenous fistulas.
Low–flow vascular malformations include lymphangiomas and venous malformations.
Hemangiomas are true, benign, neoplasms of the endothelium, and represent the most common tumor of childhood.
Hemangiomas are characterized by their absence or subtlety at birth, followed by a period of rapid proliferation, and then eventual involution.
MRI and ultrasound are the main modalities used for imaging hemangiomas and vascular malformations.

Goals of imaging of hemangiomas and vascular malformations are
- lesion characterization
- anatomic location/extent


MR features

Hemangiomas are usually isointense on T1, hyper intense on T2, and show diffuse enhancement.

Low flow vascular malformations:
- Venous malformations are dilated, "serpentine", lesions, which are hyper intense on T2 and intermediate signal on T1, and may have slow contrast enhancement of the vessel channels. Low signal phleboliths may be seen.
- Lymphangiomas tend to "infiltrate" the adjacent anatomic structures, and contain variably sized cystic spaces which are variable on T1 (due to variable protein content), hyper intense on T2 and do not demonstrate enhancement of the central cystic spaces.
- High-flow vascular malformations are characterized by flow voids suggestive of rapid blood flow.


Treatment

Treatment of hemangiomas is usually conservative.
Treatment of low flow vascular malformations is currently percutaneous sclerosis.
Treatment of high flow vascular malformations is arterial embolization.

Dural plasmacytoma

Findings


There is an extra-axial, dural based mass predominantly in the high left posterior parietal region which is relatively isointense signal on TI (Figure 1) and T2 (Figure 2) sequences.
The lesion demonstrates homogeneous contrast enhacement on post contrast sequences, (Figure 3). Extension along the interhemispheric fissure (Figure 4), encasement of the superior sagittal sinus (Figure 4) and extension across midline to the right (Figure 4) is demonstrated.


Diagnosis: Dural plasmacytoma


Plasmacytomas of the dura are uncommon plasma cell tumors that may occur as a solitary neoplasm or, more commonly, in association with multiple myeloma. The latter is usually accompanied by multiple lytic lesions of the skull. In distinction, solitary craniocerebral plasmacytomas are relatively benign and potentially curable. Therefore, distinction between the two has important clinical consequences. The differential diagnosis for dural plasmacytoma includes metastasis, lymphoma, dural sarcoma, plasma cell granuloma and meningioma.

Dural plasmacytomas are often confused with meningiomas (the most common extra-axial neoplasm found in adults) as the two have similar features and imaging characteristics. Both occur more commonly in women during the 5th decade of life with a predilection for similar sites of involvement including the cerebral convexities, sphenoid ridge, falx, and tentorium. On MR both may appear nearly isointense to brain on T1W images and iso- to hyperintense on T2W images with marked contrast enhancement. A characteristic "dural tail" and intratumoral calcifications may be seen in both lesions. Other manifestations of intracranial plasmacytoma may include diffuse leptomeningeal disease and rarely, intracerebral lesions with vasogenic edema.

These patients may present with intracranial hypertension and/or focal neurological signs from the dural origin of the tumor. Clinically, individuals with solitary dural plasmacytomas can be distinguished from those with multiple myeloma by the absence of hypercalcemia, renal insufficiency, anemia, lytic osseoues lesions, bone marrow plasmacytosis, and elevated serum or urinary paraprotein. Following surgical decompression and/or local radiotherapy for a solitary dural plasmacytoma, the prognosis is fairly good. This is in contrast to patients with plasmacytoma and multiple myeloma who typically have a much poorer prognosis.