Simultaneous recording of extra-tympanic electrocochleography and brainstem evoked responses in clinical practice.

Normal and clinical cases were investigated with simultaneous recording of extra tympanic electrocochleography and brainstem evoked responses. In group 3 cases where a non-recruiting hearing loss greater than or equal to 40 db. at 2 KHz and/or 4 KHz is present, brainstem recordings alone are not adequate for differential diagnosis of deafness due to the frequent inability to identify wave I. Therefore, electrocochleography is essential in these cases for determining the N1-V interpeak latency. Ideally cases as characterized in group 3 should be investigated by simultaneous recording of the brainstem evoked response and electrocochleography, preferably by a non-invasive technique. The test procedure is acceptable as a routine clinical investigation and avoids delay in diagnosis.