Clinical Significance of the Extratympanic Electrocochleography

Cho, Song Lae; Yoon, Tae Hyun; Chung, Jong Woo; Lee, Kwang Sun

Abstract

Electrocochleography(ECoG) is used to evaluate the cochlear function in patients with Meniere's disease. Endolymphatic hydrops is widely accepted as the underlying pathological finding in Meniere's disease and may cause the elevation of the ratio of summating potential amplitude to action potential amplitude. So, SP/AP amplitude ratio has been suggested as a diagnostic indicator for Meniere's disease. A variety of electrode locations have been employed to record the precise cochlear potentials better. In this study, we peformed extratympanic ECoG with an electrode(TIP trode(R)) that was placed in contact with the ear canal wall in normal subjects and Meniere's patients. The SP/AP amplitude ratio and the SP amplitude measured in the ears of patients with bilateral Meniere's disease and in the involved ear of patients with unilateral Meniere's disease were significantly larger than in the ears of normal subjects. In the contralateral ear of patients with unilateral Meniere's disease, the SP/AP amplitude ratio was significantly larger than in the ears of normal subjects; however, it was below the level for the diagnostic criteria of endolymphatic hydrops in Meniere's disease. This study suggests that ECoG can be a useful tool for the diagnosis of Meniere's disease and the early detection of incipient Meniere's disease in the contralateral ear of a patient with unilateral Meniere's disease.