Utility of electrocochleography for cochlear implant recipients and its potential to predict post-operative hearing thresholds objectively

Abstract

The relationship between postoperative hearing threshold and CM measured using AIM system developed by Advanced Bionics was investigated in this study. Seven participants (eight ears) with hearing thresholds better than 85 dB HL at 500 Hz were enrolled so far. All were unilaterally or bilaterally implanted with Advanced Bionics HiFocus Mid-Scala or SlimJ electrode arrays. Electrocochleography (ECochG) amplitudes were recorded both intraoperatively and postoperatively at different follow-up sessions. Objective hearing thresholds predicted by the AIM system were compared to the participants’ behavioural hearing thresholds. The trace of CM amplitude showed patterns of either rising or steady responses, except decrease in one case (response amplitude dropped for 12 μV). For the eight participants, the mean difference between the objective hearing levels (ECochG thresholds) measured immediately post-operatively and the preoperative behavioural threshold across 125 Hz, 250 Hz, 500 Hz, and 1000 Hz is 4.90 dB, while its difference to postoperative behavioural threshold is 3 dB. AIM can assist the surgeon to optimize electrode array insertion and thus reduce the possibility of insertion trauma or translocation. Key Words: Hearing preservation, electrocochleography monitoring, cochlear microphonics, cochlear implantation.