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Dysfunction of the Cochlea Contributing to Hearing Loss in Acoustic Neuromas: An Underappreciated Entity

Roosli, Christof*†; Linthicum, Fred H. Jr.; Cureoglu, Sebahattin§; Merchant, Saumil N.*

doi: 10.1097/MAO.0b013e318248ee02
Tumors of the Ear and Cranial Base
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Objective Hearing loss is a common symptom in patients with cochleovestibular schwannoma. Clinical and histologic 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 vestibular schwannoma (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 presence of endolymphatic hydrops and precipitate within the endolymph or perilymph. Observed pathologies were correlated to nerve of origin, VS volume, and distance of VS from the cochlea. Hearing thresholds also were assessed.

Results VS caused significantly more inner and outer hair cell loss, cochlear neuronal loss, precipitate in endolymph and perilymph, and decreased pure tone average, when compared with the opposite ear. Tumor size, distance from the cochlea, and nerve of origin did not correlate with structural changes in the cochlea or the hearing threshold.

Conclusion There is significant degeneration of cochlear structures in ears with VS. Cochlear dysfunction may be an important contributor to the hearing loss caused by VS and can explain certain clinically observed phenomena in patients with VS.

*Massachusetts Eye and Ear and Infirmary, Harvard Medical School, Boston, Massachusetts, U.S.A.; †Clinic of Otorhinolaryngology–Head and Neck Surgery, University Hospital Zurich, Zurich, Switzerland; ‡House Ear Institute, Los Angeles, California; and §Department of Otolaryngology, University of Minnesota, Minneapolis, Minnesota, U.S.A.

Address correspondence and reprint requests to Christof Roosli, M.D., Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114, U.S.A; E-mail: christof_roosli@meei.harvard.edu

Supported by the National Institutes of Health (National Institute on Deafness and other Communcation Disorders) grant U24 DC011943, and the “Nachwuchsförderungskredit” of the University of Zurich.

The authors disclose no conflicts of interest.

© 2012 Otology & Neurotology, Inc.