Infratentorial (Posterior Fossa) Ependymoma
- 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% to 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
Good CD, Wade AM, Hayward RD, et al. Surveillance neuroimaging in childhood intracranial ependymoma: how effective, how often, and for how long? J Neurosurg 2001;94:27–32. doi.org/10.3171/jns.2001.94.1.0027.
Louis DN, Ohgaki H, Wiestler OD, et al. The 2007 WHO classification of tumours of the central nervous system. Acta Neuropathol 2007;114:547. doi.org/10.1007/s00401-007-0243-4.
Merchant TE, Li C, Xiong X, et al. Conformal radiotherapy after surgery for paediatric ependymoma: a prospective study. Lancet Oncol 2009;10:258–266. doi.org/10.1016/s1470-2045(08)70342-5.
Osborn AG, Salzman KL, Jhaveri MD. Diagnostic Imaging (3rd ed). Elsevier, Philadelphia, PA; 2016.
Yuh EL, Barkovich AJ, Guptacorresponding N. Imaging of ependymomas: MRI and CT. Childs Nerv Syst 2009;25:1203–1213. doi.org/10.1007/s00381-009-0878-7.
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