Presentation
Headache, nausea, and vomiting.
Patient Data
There is a well-circumscribed CSF intensity lesion within the right cerebellopontine angle with indentation of the medulla, middle cerebellar peduncle, and vestibulocochlear nerve. Content follows CSF on all sequences including diffusion-weighted imaging. No abnormal enhancement. The seventh and eighth cranial nerves are displaced superiorly. The ventricles are unremarkable in appearance with no evidence of hydrocephalus.
Case Discussion
The features, in this case, are pathognomonic of an arachnoid cyst, in a typical location for an epidermoid cyst. The absence of any significant diffusion restriction confirms the diagnosis.