Angiogenesis from the eighth cranial nerve to vestibular schwannomas.

Vascularization between vestibular schwannomas and the adjacent eighth cranial nerve was examined in order to elucidate the angiogenic effect of these tumours. Specimens from 12 patients were examined by light microscopy and immunohistochemistry (series 1), while specimens from another 17 patients were examined by light and transmission electron microscopy (series 2). Slight to marked angiogenesis was found in 5 patients from series 1 and 7 patients from series 2. Ultrastructural examination indicated that these blood vessels were more fragile than those in the normal eighth cranial nerve. These findings suggested that sudden hearing loss in vestibular schwannoma patients may be related to the disruption of such blood vessels. In addition, surgical injury to these blood vessels may cause postoperative hearing loss despite preservation of the cochlear nerve.