DYSFUNCTION OF THE COCHLEA CONTRIBUTING TO HEARING LOSS IN ACOUSTIC NEUROMAS: AN UNDER- APPRECIATED ENTITY

Objective—Hearing loss is a common symptom in patients with cochleovestibular schwannoma (VS). Clinical and histological observations have suggested that the hearing loss may be caused by both retrocochlear and cochlear mechanisms. Our goal was to perform a detailed assessment of cochlear pathology in patients with VS. Study Design—Retrospective analysis of temporal bone histopathology. Setting—Multi-center study. Material—Temporal bones from 32 patients with unilateral, sporadic VS within the internal auditory canal. Main Outcome Measures—Sections through the cochleae on the VS side and opposite (control) ear were evaluated for loss of inner and outer hair cells, atrophy of the stria vascularis, loss of cochlear neurons, and for presence of endolymphatic hydrops and precipitate within endolymph or perilymph. Observed pathologies were correlated to nerve of origin, VS volume, and distance of VS from the cochlea. Hearing thresholds were also assessed. Results—VS caused significantly more inner and outer hair cell loss, cochlear neuronal loss