Establishment And Rudimentary Application Of The Method Of Recording Electrically Evoked Auditory Brainstem Responses

[Objective]To establish the method of recording electrically auditory brainstem responses (EABR) in cochlear implantation .[Methods]37 patients due to different causes (including auditory neuropathy, ossified cochlea, Inner Ear Malformation, abnormal white matter, having a history of meningitis, etc.) and of different ages were tested with EABR during cochlear implantation. They were divided into two groups. The first group (20 cases) received a bipolar electrical stimulation from electrodes of cochlear implants after implantation surgery. EABR waveforms were recorded by GSI Audera evoked potential instrument. Based on the data of the first group, the second group (17 cases) was mono-polar electrically stimulated with a balanced two-phase pulse current before implantation, using modified cochlear implant connected to an in vitro speech processor as the stimulation device, and with self-made spherical iridium-platinum alloy electrode as positive stimulation electrode placed in round window niche. EABR was recorded by Bio-logic Navigator Pro evoked potential instrument. It has been preliminarily used in some special cases.[Results]Clear EABR waveforms were recorded in all 37 cases. In the first group, EABRⅡ～Ⅴwaveforms were recorded in all 20 patients, and some also have I waveform recorded. The average latencies of waveformⅢandⅤwere 2.04±0.20ms and 3.96±0.41ms respectively, with average response threshold at 148.46±11.63CL(current level). In the second group, EABR waveformsⅡ～Ⅴwere recorded in all 17 cases. The average latencies of waveformⅢandⅤwere 2.12±0.18ms and 4.18±0.19ms respectively, with average response threshold at 220.0±16.04CL. This group includes two cases of auditory neuropathy, seven cases of inner ear malformation, one case of cochlear ossification, two cases of abnormal white matter, and one case of having a history of meningitis. Well-differentiated waveform were recorded in all of them.[Conclusion]EABR is an objective nerve electrophysiological testing method that accurately reflects functional completeness of auditory pathway. It has an great value in making the judgement whether patients can acquire auditory response after cochlear implantation, especially for the patients without any residual hearing and with suspicious auditory neuropathy . This method is safe, gives high emission of auditory response and therefore is worthy of spreading to application.