PATHOPHYSIOLOGY OF MENIERE'S DISIESE AS DEDUCED BY ELECTROCOCHLEOGRAPHY

Abstract

In order to grasp the pathophysiologic situation of the inner ears of patients with Meniere's disease, compound action potential (AP), summating potential (SP) and cochlear microphonics (CM) were examined by transtympanic electrocochleography.Hearing impairments were divided by the pure tone audiogram into three types. Type I indicates fluctuating hearing impairment resulting in a recovery to normal range at some interval, type II indicates fluctuating hearing impairment without recovery to normal range and type III indicates.. fixed hearing loss with a flat audiogram.In type I, asuper normal AP amplitude, CM amplitudes at 0.5kHz and 4kHz and an increased negative SP were noted in most cases.The ratio of AP to negative SP was lower and the ratio of AP to positive SP was higher than the other types. The CM thresholds at 0.5kHz and 4kHz were well maintained in typeI. In type III both AP and CM amplitudes were lower than control being 1/2-1/5 of the latterand further the ratio of AP to negative SP was higher and the ratio of AP to positive SP showed was lower than the other types. The threshold at 0.5kHz was well maintained in type III. In type II and III, the AP latency was prolonged in all cases. In type II, AP, SP and CM responses were intermediate between type I and III.In view of the above findings, the author considers that the main etiological factor in type I is a reversible change in the endolymphatic space with a temporary physiological blockage of the sensory cells, in type III, a structural change of the endolymphatic space with endolymphatic hydrops with partial lesion of sensory cells, and in type II a mixture of type I and III.