Electrocochleographic study of low-tone hearing loss without vertigo.

Auditory nerve action potential (AP), cochlear microphonics (CM) and summating potential (SP) were recorded from 6 patients with low-tone hearing loss without vertigo. All these cases showed high AP and -SP amplitude and satisfactory CM response. These findings resembled the electrocochleographic findings of type 1, which is an early stage of Ménière's disease. Hearing returned to normal range in half of the cases but remained hardly changed in the other half. The difference between these two groups could not be clarified electrocochleographically. On the other hand, low-tone hearing loss due to retrolabyrinthine lesion and due to familial sensorineural deafness was shown to have a low AP amplitude.