Loss of vestibular neurons in clinical otosclerosis.

Abstract

Although the principal functional deficit caused by otosclerosis is hearing loss, some patients also experience dysequilibrium and/or vestibular test abnormalities. A study was performed to determine the populations of vestibular neurons in subjects with clinical otosclerosis. Reduced neuronal counts were found when the otosclerotic lesions were large enough to involve the cribrose areas. Decreased cell counts were found principally in the superior division of the vestibular ganglion. In some cases, however, normal populations of neurons were found in spite of involvement of the cribrose areas. In some ears there were bundles of vestibular nerve fibers deviating from their normal course to pass within the focus of otosclerotic bone. It seems probable that a loss in vestibular neuronal population caused by involvement of dendritic fibers in the cribrose areas is at least partially responsible for the dysequilibrium or vestibular test abnormalities occurring in some patients with otosclerosis.