CT and MRI diagnosis of posterior fossa atypical ependymoma

Objective: To analyse the CT and MRI features of posterior fossa atypical ependymoma. Methods: Sixteen cases of posterior fossa atypical ependymoma proved by surgery and pathology had CT and (or) MRI scanning. There were 11 males and 5 females. The age ranged from 17 to 46 (mean, 31.2). Twelve cases ranged from 20 to 40 years old. the main symptoms of all cases were dizziness, unsteady walking and vomiting. Results: The locations of all cases were cerebellum (12 cases), vermis (3 cases) and cerebellopontile angle (1 cases). Fifteen cases were solid with multiple cystic changes and 1 case in the cerebellopontile angle was cystic. The tumor was usually close to the surface of cerebellum with rather extensive connection with dura mater or tentorium. Calcifications were shown in 3 cases. The tumors revealed inhomogeneous density on CT scan and inhomogeneous intensity on MRI. Mild inhomogeneous enhancement was shown in most cases, while intense irregular enhancement in the others. Conclusions: The characteristic findings of the posterior fossa atypical ependymoma ependymoma were cerebellar intraparenchymatous multiple small cystic changes within solid tumor in most cases and inhomogeneous density and intensity on CT and MRI. The differential diagnosis is meningioma, metastasis and acoustic schwannoma