Schwannoma

Findings:

A heterogeneously enhancing mass involves the CP angle cistern and internal auditory canal, associated with mass effect on the brachium pontis and mild distortion of the fourth ventricle. There is no surrounding edema. The mass is well-defined with heterogeneous central zones of cystic change and/or necrosis, and the mass is predominantly T2 hyperintense with some small zones of hypointensity.

Differential Diagnosis/Discussion:

The differential diagnoses of enhancing masses involving the CP angle cistern primarily includes schwannoma and meningioma. Rarely, metastasis and lymphoma can present in this way. More rarely, and exophytic high grade glial neoplasm may invade the CP angle cistern, but an irregular interface with adjacent brachium pontis would be expected. Meningiomas typically enhance more homogeneously and may have a dural tail as well as a broad base of contact to the IAC, and often will not extend into the IAC. Therefore, this lesion is most compatible with a schwannoma.

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