Endotoxic damage to the stria vascularis: the pathogenesis of sensorineural hearing loss secondary to otitis media

ABSTRACT

The incidence of sensorineural hearing loss [SNHL] secondary to otitis media is higher than recognied. This study presents animal experiments on endotoxin [LPS] damage to the inner ear with special reference to the stria vascularis. A dose of micro g / 5 microL LPS is injected into the perilymphatic space of the inner ear of guinea pigs. Only 5 microL normal saline is given in control group. Audiometric measurement with ultrastructural evaluation on the stria vascularis is done before and 1, 3, and 5 days after the treatment. In the control group no significant difference is found audiometrically as well as ultrastructurally. CAP thresholds of the LPS ears were raised and N 1/P 1 latencies prolonged, indicating SNHL induction. The stria vascularis in LPS ears shows marked damage of the organelles mainly in the marginal cells. The mitochondria were swollen with their crests in disorder, broken or vanished. Intercellular space is widened, Secondary lysosomes are increased and enzymal reactant of Na[+]-K[+] ATPase diminished. LPS induced otoxicity in the stria vascularis provides presumptive ion imbalance, causing change of endolymph composition and failure of energy supply to the Cotrical organ. The fact is responsible for the pathogenesis of SNHL secondary to otitis media