Neuro -- Infratentorium

Front 1

What is the DDX of cystic mass with mural nodule?

Back 1

In a child = JPA
In an adult = Hemangioblastoma; flow voids can be seen due to hypervascularity.

Front 2

What is the DDX of brainstem lesion that is T2/FLAIR hyperintese?

Back 2

- Central pontine myelinolysis
- Ischemia
- Multiple sclerosis
- Encephalitis
- Infiltrating glioma

Front 3

1. What are the imaging findings of JPA?
2. What are other common locations for jpa?

Back 3

1.
- JPAs may be cystic with a mural nodule, solid, or solid with cystic degeneration.
- intense enhancement of the solid portions.
- sharply demarcated with minimal surrounding edema
- cerebellar jpa often originate in the midline and extend into the crerbellar hemispheres.
2. Jpa can also occur n the hypothalamus, optic nerves, brainstem, and cerebral hemispheres.
2.

Front 4

1 what are imaging findings of hemangioblastoma?

Back 4

- benign tumor that represents the 2nd mos common posterior fossa mass in an adult (mets are the most common).
- classically described as a cyst with an enhancing nodule. However, 40%can be predominantly solid or both cystic and solid.
- solid mural nodule that abuts the pial surface.
- cyst is generally not neoplastic and does not need to be resected unless there s evidence of tumor involvement (as evidenced by enhancement of the cyst wall)
- 10-20% of cases are associated with VHL.
- pts may have polycythemia from erythropoietin production.
- flow voids representing feeding and draining vessels are seen adjacent to or within the nodule.

Front 5

1. Where do brainstem gliomas arise from?
2. How are branstem gliomas managed?
3. What are the imaging findings of tectal gliomas?

Back 5

1. Brainstem gliomas may arise from the pons or the tectal plate. Pontne gliomas may extend into the midbrain or medulla.
2. Brainstem gliomas are not usually bx'ed or treated. They are monitored with serial imaging to document stability
3.
- usually results in compression of the cerebral aqueduct with resultant hydrocephalus.
- tectal glioma may show loss of intercollicular depression of the tectal plate.
- enhancement is atypical and may indicate a need for bx and treatment.
- if a lesion extends beyond the tectum but is still confined to the midbrain, it is called peritectal tumor.
4.
- diffuse pontine enlargement with abnormal SI.
- basilar artery may be engulfed b exophytic growth of the tumor.
- infiltrates into midbrain and medulla.
5.
- brainstem encephalitis: more acute history, may have a fever and a reactive CSF profile.
- infiltrating neoplasm such as leukemia or lymphoma: pts usually have known systemic disease.
- acute demyelination: ms or ADEM.

Front 6

1. Where do medulloblastomas arise for in children?
2. Where do medulloblastomas arise for in adolescents and adults?

Back 6

1. Childhood medulloblastoma arises from the vermis and is located in the midline.
2. In adolescents and adults, medulloblastoma more commonly arises laterally in the cerebellar hemispheres.
3. Drop mets occur in 40% of cases.
4. round, circumscribed hyperdense (high cellularity) mass with mild to moderate surrounding edema and heterogeneous enhancement.
5. Systemic mets are rare but do occur (bone, lymph nodes, lung). Metastatic medulloblastoma may cause sclerotic lesions in bipone, while mets to the abdominal cavity may occur with a venticuloperitoneal shunt.
6. Medulloblastoma may grow n an exophytic fashion not the cerbellopontine angle, mimicking ependymoma.

7.
- Gorlin syndrome: basal cell nevi, odontogenic keratocyst, falx calcification.
- Turcot syndrome: colonic polyps, Cns malignancy -- medulloblastoma or GBM.

Front 7

What are the imaging findings of ependymoma?

Back 7

1.
- lobulated heterogeneous intraventricular mass that may be cystic, hemorrhagic, or partly calcified.
- extend out of the foramina of Luschka into the cerbellopontine and cerebellomedullary angles and out the foramen of Magendie into the upper cervical canal.
- may invade into adjacent brain parenchyma.
- drop mets are common.

Front 8

Posterior fossa mass in a child

Back 8

- Medulloblastoma
- Pilocytic astrocytoma
- Ependymoma
- Brainstem glioma

Front 9

Posterior fossa mass in an adult

Back 9

INFARCTION
- may have mass like appearance --edema, mass effect, subacute enhancement
- corresponds to a vascular teritorry
- restricted diffusion; vascular occlusion demostrated on CTA/MRA
METASTATIC DISEASE
- MCC of posterior fossa intra-axial mass.
HEMANGIOBLASTOMA
- 90-95% occur in the PF
- associated with VHL
- cystic mass with enhancing mural nodule
- smaller lesions present as solid enhancing masses
- when identified, the entire neuroaxis should be imaged to look for additional lesions especially within the spinal cord.
VASCULAR MALFORMATION
- Cavernous malformation
- AVMs (multiple seen with osler-weber-rendu syndrome): may mimic mets and hemangioblastomas.
HYPERTENSIVE HEMORRHAGE

Front 10

Posterior fossa cyst

Back 10

MEGA CISTERNA MAGNA
- normal variant in which the CSF filled cisterna magna is prominent
- normal appearance and size of posterior fossa, normal cerebellar vermis, and 4th ventricle
- presence of internal vessels
ARACHNOID CYST
- exert local mass effect
- majority occur along the middle cranial fossa; in the posterior fossa = cerebellopontine angle and cisterna magna
- when large, can compress 4th ventricle or cerebral aqueduct reslting in obstructive hydrocephalus.
DANDY-WALKER MALFORMATION
- dilated 4th ventricle that is in continuity with a psoterior fossa CSF filled fluid collection.
JOUBERT SYNDROME (VERMIAN HYPOPLASIA)
- dysplasic/hypoplastic cerebellar vermis
- bulbous 4th ventricle that has a characteristic bat wing configuration
- Molar tooth appearance of midbrain on axial images.

Front 11

Cerebellar atrophy

Back 11

ALCOHOL ABUSE
- disproportionate involvement of the SUPERIOR vermis and cerebellum.
- associated with Wernicke's encephalopathy = T2 hyperintensity in the periaqueductal gray matter, mammillary bodies, medial thalamus, and hypothalamus.
- Associated with Marchiafava-Bignami: T2 hyperintensity in CC.
ANTICONVULSANT THERAPY:]
- long term anticonvulsant therapy
- Phenytoin may also cause calvarial thickening.
PARANEOPLASTIC SYNDROME
- cerebellar degeneration from multiple malignancies (breast, lung, GI, GU, lymphoma, NB)
- may precede the diagnosis of primary tumor.
RARE CAUSES
Sporadic olivopontocerebellar atrophy:
- neurodegenerative disease with adult onset.
- atrophy of pons, midbrain, cerebellum (hemispheric > vermian) with resultant enlargement of the 4th ventricle.
Cerebello-olivary degeneration
- progrerssive atrophy of cerebellar cortex + volume loss within olivary nuclei of medulla.
- enlargement of the 4th ventricle.
Friedreich ataxia
- AKA spinocerebellar ataxia
- cerebellar and spinal cord atrophy

Front 12

Llhermite Duclos

Back 12

- AKA dysembryoplastic gangliocytoma
- Represents a hamartoma
- Look for corduroy appearance
- Associated with Cowden syndrome (50%)
- Cowden syndrome has increased risk of breast, thyroid, gu malignancies.

Front 13

Rhomboencephlosynapsis

Back 13

- Absence of the cerebellar vermis with fusion of cerebellar hemispheres

Front 14

Hot cross bun sign

Back 14

- seen in multiple system atrophy (neurodegenerative disorder in which there are features of Parkinsonism and/or cerebellar ataxia).
- look for hyperintense linear area forming a "cross" in the pons.
- look for associated atrophy of the brainstem, cerebellum, and cerebrum (prominence of sulci) and abnormal signal intensity in the middle cerebellar peduncle.

Front 15

1. What is the etiology of Lhhermite-Duclos disease (LDD) AKA Dysplastic gangliocytoma of the cerebellum?
2. What is imaging appearance of LDD?
3. What is included in the differential diagnosis?

Back 15

1. Unclear if LDD is dysplastic, hamartomatous, or neoplastic in origin.
2.
- Large, NON-ENHANCING mass located in the cerebellar hemisphere with occasional involvement of the vermis and/or cerebellar peduncle.
- T2 HYPERINTENSE mass with LINEAR LOW SIGNAL intensity STRIATIONS mimicking a CORDUROY appearance.
3.
- Cerebellar infarct
- Cerebellar neoplasm

Front 16

1. What is the most common posterior fossa mass in a child?
2. What are the imaging findings of medulloblastoma?

Back 16

1. Pilocytic astrocytoma. The second most common mass is a medulloblastoma.
2. Medulloblastoma are more common in males. They belong to the PNET family of tumors.
- arise from the roof of the 4th ventricle.
- dense cell packing leads to hyperdensity on CT scan and low SI on T2WI.
- may calcify or have cystic components. Usually enhance homogeneously.
- The tumor may spread via the CSF to basilar cisterns, ventricles or the spinal cord. Drop mets are best evaluated with contrast scans as they enhance brightly.

Front 17

1. What is the cause of ataxia-telangiectasia?
2. What are the imaging findings of ataxia-telangiectasia?
3. What is lacking in these patients?

Back 17

1. Mutation of a gene thought to control the cell cycle and DNA repair mechanisms.
2.
- Multiple capillary telangiectasias on the skin and mucous membranes.
- Progressive cerebellar degeneration (atrophy of the anterior vermis)
- Increased risk of lymphoma
3. Cellular immune deficiency is lacking in these pts. They do not have lymphoid tissues, spleen. thymus, and lymph nodes. Therefore, they usually die of overwhelming infection.