Infratentorial Ependymoma

KEY FACTS

TERMINOLOGY

• Posterior fossa ependymoma (PF-EPN)

IMAGING

• Ependymoma can occur anywhere in neuraxis

• Most common site: Posterior fossa (2/3 of cases)

○ Lobulated mass in body/inferior 4th ventricle

– Soft or "plastic" tumor

□ Accommodates to shape of ventricle

□ Squeezes through foramen of Magendie into

cisterna magna

□ ± extension through foramina of Luschka into

cerebellopontine angle cisterns

• NECT

○ Ca++ common (50%)

○ ± cysts, hemorrhage

○ Obstructive hydrocephalus common

• MR

○ Variable enhancement; usually does not restrict on DWI

PATHOLOGY

• 3 posterior fossa ependymoma molecular subtypes

○ Posterior fossa ependymoma subtype A (PF-EPN-A)

– Most common (50%)

– Predominately infants

– Poor prognosis

○ PF-EPN-B

– 10% of PF-EPNs

– Older children, adults

– Better prognosis

○ Subependymoma (PF-SE)

CLINICAL ISSUES

• Signs of increased intracranial pressure

• 3-17% cerebrospinal fluid dissemination

DIAGNOSTIC CHECKLIST

• Much less common than primitive neuroectodermal tumormedulloblastoma or pilocytic astrocytoma

(Left) Posterior fossa

ependymoma (PF-EPN)

extends through the 4th

ventricle outlet foramina into

the cisterna magna ﬇ and

CPA cistern ſt; "plastic"

pattern of growth is typical of

ependymoma in this location,

increases the difficulty of

surgical resection. (Right)

Sagittal T1 C+ MR shows

classic PF-EPN as a lobulated

mixed cystic/solid enhancing

mass displacing the brainstem

anteriorly, expanding the 4th

ventricle. Tumor extrudes

posteroinferiorly through the

foramen of Magendie st into

the cisterna magna ﬊.

(Left) Axial T1 C+ FS MR scan

in the same case shows the

enhancing mixed cystic ﬇ and

solid ſt tumor expanding,

filling the 4th ventricle st.

(Right) Coronal T1 C+ MR scan

in the same case again shows

the mixed cystic/solid

enhancing mass conforming to

the shape of the expanded 4th

ventricle ſt. The tumor

extrudes inferiorly through the

enlarged foramen of

Magendie st and extends into

the upper cervical spinal canal

﬊. WHO II cellular

ependymoma was found at

surgery.

Brain: Pathology-Based Diagnoses: Neoplasms,

Cysts, and Disorders

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