The limitations of hearing preservation in acoustic neuroma surgery: histological study of the interface between the eighth cranial nerve and the tumor.

The interface between the eighth cranial nerve and acoustic neuroma was investigated by light microscopy and immunohistochemistry in paraffin sections in 13 patients, and in Epon sections in 19 patients. The cochlear nerve was severely invaded by tumor cells in two of six specimens examined, moderately invaded in two specimens, and not invaded in two specimens. Gliosis was frequently found within the cochlear and vestibular nerve. Hemangioma-like tissue was occasionally found attached to the cochlear and vestibular nerve adjacent to the tumor. These findings were considered to be related to difficulty in hearing preservation in some patients although acoustic neuroma surgery was successful.