Audiological Findings in Patients with Essential Retrocochlear Lesions

Five cases of so-called retrocochlear deafness with impaired speech intelligibility in spite of nearly normal pure-tone sensitivity were presented and discussed on the origins of this deafness. These patients presented with the following common audiological findings, as almost normal audiogram, extremely poor speech discrimination scores, fluctuation in hearing acuity, increased threshold of interaural time discrimination, essentially broad action potential in cochleogram and no auditory brainstem responses. Based on the above findings, we supposed that the impaired speech perception might be due to interference with the precise neural timing relations required by such tasks, and these patients might have main lesions in the peripheral auditory nerve. However, we could not confirm the presence of lesions on the other levels of the central auditory nervous system. We brought forward the tentative diagnostic name of “essential retrocochlear lesion” to such deafness, and we were accumulating the electrophysiological data of these patients.