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Epidermoid cyst - cerebellopontine angle

Case contributed by Bahman Rasuli
Diagnosis almost certain

Presentation

Vertigo and headache.

Patient Data

Age: 35 years
Gender: Female

There is a near CSF signal intensity mass with high signal on DWI and ADC values similar to the cerebellum in the right cerebellopontine angle associated with marked pressure effect on the lateral aspect of the pons, right brachium pontis, and right trigeminal nerve. The medial aspect of the lesion is adjacent to the basilar artery and the superior surface abuts the right posterior cerebral artery. The inferior aspect of the lesion comes in proximity to the origin of the seventh and eighth nerves without definite mass effect. 

High signal foci in T2 and flair sequences at subcortical and periventricular white matter of both cerebral hemispheres depict microvascular ischemic events.

Dilatation of the lateral and third ventricle is seen.

Case Discussion

Epidermoid cyst of the cerebellopontine angle is in the main differential diagnosis of an arachnoid cyst. Both of them are low density on CT scan, low signal on T1, and high signal on T2 weighted images and never enhances.  On Flair sequence, the arachnoid cyst demonstrates a similar signal to CSF, whereas epidermoid may have high or low signal intensity. But on DWI images, the epidermoid cyst appears bright however arachnoid cyst is not bright.

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