Inner Ear Disorders Caused by Barotrauma in Guinea Pigs

Abstract

To determine the mechanism of hair cell damage caused by barotrauma to the inner ear, we investigated morphological changes in the organ of Corti and stria vascularis using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Fractures of the stereocilia with minimal intracellular changes were observed immediately after trauma. One day later, there was marked degeneration of outer hair cells and expansion of supporting cells. The damage to stereocilia clearly preceded morphological alterations within the hair cell bodies. Most outer hair cells eventually disappeared and were replaced by supporting cells. Inner hair cells degenerated slowly: some were almost intact 1 month after the trauma despite the disappearance of stereocilia. The continuity of reticular lamina was maintained throughout the period of hair cell degeneration, preventing leakage of endolymph into the organ of Corti. Reversible dendritic swelling of inner hair cells occurred immediately after trauma. No change in the stria vascularis was observed over time. Our results suggest that the mechanism of hair cell damage caused by inner ear barotrauma is related to a deformity of the organ of Corti caused by a pressure discrepancy between the perilymph and endolymph, resulting in injury to stereocilia.