Objective: To establish the method of recording auditory brainstem responses electrically stimulated via round-window niche in cochlear implants.
Methods: Self-made platinum iridium alloy as a spherical electrode stimulation electrode, modified cochlear implants connected to in vitro speech processor as a electro-stimulator and evoke potential instrument for Bio-logic Navigator Pro, 17 cochlear implant patients with various ages and of different causes, including auditory neuropathy (2 cases), ossified cochlea (1 case), inner ear malformation (5 cases), leukodystrophy (1 case), unknown and reason (8 cases) were investigated during cochlear implant surgery. Before cochlear implantation, stimulation electrode was placed in the round-window niche while charge balanced biphasic constant current was used as electrical stimulation via round window niche, and then electrically evoked auditory brainstem response was recorded.
Results: Electrically evoked auditory brainstem response waveforms were clearly recorded in all 17 cases. The latencies of III and V waves were (2.12 +/- 0.18) ms and (4.18 +/- 0.19) ms respectively, with threshold as (220.0 +/- 16.04) CL. The waveforms of the 2 patients with auditory neuropathy, 5 patients with inner ear malformation, 1 patient with ossified cochlea and 1 patient with leukodystrophy were well differentiated.
Conclusions: Monitoring electrically evoked auditory brainstem response was an objective nerve electrophysiological testing method that accurately reflects function completeness of auditory pathway. It had important value for helping making the judgment whether patients could acquire auditory response after cochlear implantation. This method was safe and gave high emission of auditory response, therefore should be spread widely.