Cochlear nerve in neurilemomas. Audiology and histopathology

Correlative data between the histopathologic changes in the cochlear nerve and audiologic findings are reported in 16 cases of neurilemomas. Poor speech discrimination, positive or absent recruitment, excessive adaptation, or separation of forward vs reverse continuous tone Bekesy tracings did not correlate with the number of preserved nerve fibers. There were several cases with profound hearing loss in which the nerve fiber population approached normal. Histologically, pathologic changes included dilated fibers and increased interfibrillary collagen. In many specimens the fibers were further apart than normally, especially in the immediate vicinity of the tumor, and many lay between tumor cells. The tumor-nerve interface was usually gradual and no abrupt change appeared at the transition from the nerve to the tumor, the Schwann cells appearing to continue as tumor cells. Nonspecific changes apparently due to specimen handling were seen in some areas of most specimens.