一側性メニエール病の健耳のか電図検査

Abstract

It is well known that some patients with unilateral Meniere's disease subsequently develop bilateral involvement. Since electrocochleography (ECochG) is useful in assessing endolymphatic hydrops, extratympanic ECochG was performed on both ears of 44 patients with unilateral Meniere's disease from 1985 to 1992. We investigated the relationship between ECochG findings and the hearing level. The negative summating potential (SP)/action potential (AP) ratio of normal control subjects in response to 80 dBnHL clicks was 0.231±0.063 (n=40), so a negative SP/AP ratio of more than 0.36 (=mean±1.96SD) was regarded as a positive ECochG response.In 32 involved ears and 6 contralateral ears, the ECochG response was positive. The negative SP/AP ratio of the involved ears was larger than that of the contralateral ears in all cases. The negative SP/AP ratio showed a significant difference between the involved ears and the contralateral ears as well as between the involved ears and the ears of control subjects, but not between the contralateral ears and the control ears. The hearing level of the involved ears with a positive ECochG response was worse than that of the ears with normal ECochG findings. The hearing level of the involved ears was better when the contralateral ear was positive on ECochG than when it was not. The time from the first episode to the performance of ECochG was shorter when the contralateral ear was positive on ECochG than when it was not, but the difference was not significant. The largest negative SP/AP ratio in the contralateral ears was 0.48, which was not as large as that in the involved ears. It seems likely that patients with a positive ECochG response in the contralateral ear will develop bilateral Meniere's disease, but we have not yet confirmed this clinically.In conclusion, the contralateral ear may show a positive ECochG response even in the early stage of unilateral Meniere's disease.