Posterior Fossa Ependymoma

The differential diagnosis of posterior fossa masses in children essentially comes down to medulloblastoma, astrocytoma (e.g., brainstem "glioma" and pilocytic astrocytoma), and ependymoma. Posterior fossa ependymomas are most commonly associated with the fourth ventricle and may extend out of the foramina of Luschka and Magendie.

CT may show an iso or hypoatyenuating mass. Compared to other posterior fossa masses in children, ependymomas have a greater tendency for calcification, which is usually punctate. Cysts are present in a minority of cases and are usually small. There is mild contrast enhancement

On MRI, ependymomas are T1-hypointense (upper left image) and intermediate intensity on T2 (upper right image) with foci of hypointensity due to calcifications or hemorrhage (GRE: bottom left image). There may be extension of the lesion out of the foramina of Luschka (post-contrast axial: bottom right image) and Magendie.

References

Neuroradiology Requisites (2nd ed). pp 127-128.