Abstract
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 .gtoreq. 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. Electrocochleography is essential in these cases for determining the N1-V interpeak latency. Ideally, cases 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.