Infratentorial (Posterior Fossa) Ependymoma
Last Updated: September 13, 2020
- Slow-growing tumor arising from ependymal cells (radial glial cells) within the posterior fossa (PF)
- WHO grade II or III
- Three histologic subtypes
- PF ependymoma, PF ependymoma type A, PF ependymoma type B
- Useful for risk stratification
- Subtype A highly malignant
- Calcification common (50%); small cysts may be seen
- ±Cerebrospinal fluid (CSF) dissemination
- Subtype A: mean patient age at diagnosis, 3 years
- Subtype B: mean age, 30 years
- Slight male gender predilection
- Common presenting symptoms
- Headache, nausea, and vomiting due to increased intracranial pressure
- Irritability, lethargy, and developmental delay in infants
- 90%–95% 5-year survival for subtype B
- 50% 5-year survival for subtype A
- Treatment: gross-total resection followed by XRT; chemotherapy provides no survival benefit
- Well-marginated, lobulated mass
- Majority arise within fourth ventricle floor and extend through/widen ventricular foramina (Luschka, Magendie) into adjacent parenchyma and basal cisterns
- Displaces rather than invades adjacent parenchyma
- ±Hemorrhage, cysts, and necrosis
- Lobulated, often calcified mass arising within inferior portion of the fourth ventricle
- ±Cysts, hemorrhage
- Variable enhancement on contrast-enhanced CT
- T1WI: heterogeneous, often hypointense; areas of calcification and hemorrhage appear hyperintense
- T2WI: intermediate signal intensity; hyperintense cystic components; areas of hemorrhage and calcification appear hypointense
- FLAIR: heterogeneously hyperintense
- T2*GRE: signal blooming secondary to calcification and/or hemosiderin deposition from blood products
- DWI: usually does not show restricted diffusion
- T1WI+C: variable enhancement
- MR spectroscopy (MRS): elevated Cho and lactate, decreased NAA; MRS not generally helpful in distinguishing between posterior fossa medulloblastomas and astrocytomas
- MRI with contrast, CT for demonstration of calcification, MRS may be useful adjunct
For more information, please see the corresponding chapter in Radiopaedia.
Contributor: Rachel Seltman, MD
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