The solitary schwannoma of the eighth cranial nerve. An immunohistochemical study of the cochlear nerve-tumor interface.

Given recent controversy concerning hearing preservation surgery of the acoustic neurinoma, an immunohistochemical study was undertaken to investigate the cochlear nerve-tumor interface. Ten intact medium-sized acoustic neurinomas were studied by means of classic staining procedures and an immunohistochemical technique using monoclonal mouse antibodies to human neurofilaments. Our observations indicate that the cochlear nerve is histologically involved in the tumoral process in those cases in which macroscopically visible adherences between the cochlear nerve and the tumor are present. We were not able to discern a clear cleavage plane. Six of the 10 specimens showed tumoral invasion of the cochlear nerve. Several therapeutic attitudes are discussed in view of these observations and reports from the international literature. In conclusion, the principle of hearing preservation surgery is rejected in favor of total tumor removal in every case in which surgery is indicated.