Intratemporal facial nerve perineurioma.

Forty-two cases of perineurioma have been reported in the literature. This report adds the first intratemporal facial nerve perineurioma to the literature and reviews the others. Unlike schwannoma and neurofibroma, the histological features of perineurioma demonstrate onion bulb-like structures with a strong positive immunoreactivity for epithelial membrane antigen. The clinical history of gradual facial nerve paresis was 15 years in the case presentation and the clinical diagnosis of tumor was overlooked.