Epidermoid Cyst of Cerebellopontine Angle

Synonyms: Epidermoid tumor,non-neoplastic inclusion cyst, congenital cholesteatoma of the cerebellopontine angle cistern.Definition: Congenital lesion arising from inclusion of ectodermal epithelial elements at time of neural tube closure during 3rd to 5th week of embryonic life, resulting in migration abnormalities of epiblastic cells.Classic imaging appearance:(1)Signal shows an insinuating cisternal lesion with low T1, high T2 close to that of cerebrospinal fluid (CSF).(2)FLAIR shows incomplete or absent attenuation.(3)Diffusion-weighted imaging shows epidermoid cyst has restricted diffusion(high-signal lesion).Other key facts:(1)3rd most common cerebellopontine angle-internal auditory canal (CPA-IAC) mass.(2)1% of all intracranial tumors.