Balance of peripheral input and integrity of the electrode-nerve interface in a large cohort of children with bilateral cochlear implants

Abstract

The study aim was to determine whether asymmetries in the electrode-nerve interface were present in children using bilateral cochlear implants (CIs). Bilateral CIs improve hearing over unilateral CIs in children with profound deafness in both ears but benefits decrease with increasing asymmetric activity and function between ears. Effects of asymmetry between bilateral CI arrays, CI stimulation parameters, impedance and transimpedance measurements, and electrophysiological thresholds could exacerbate asymmetries at the electrode-nerve interface but these factors have not been assessed in children using bilateral CIs. Clinically generated data from a large cohort of Canadian children (n = 669 children, n = 1332 devices) was gathered retrospectively for analyses. To account for repeated measures, a mixed effects modeling analysis was conducted. Despite CI electrical stimulation levels and electrophysiological thresholds being largely stable over time, asymmetries based on implantation sequence were observed. The observed bilateral differences suggest spread of current and sensitivity to electrical stimulation vary between devices in the same individual. These peripheral asymmetries may coincide with previously reported plasticity-induced cortical changes to increase asymmetries in auditory function between ears and restrict access to binaural hearing cues.