Cochlear Implant Electrode Deactivation Produces Higher Individual but Lower Average Outcome Scores.

Abstract

To evaluate cochlear implant (CI) performance in recipients with an intact electrode array compared to a subset with one or more electrodes deactivated to examine differences in speech perception outcomes. A review of a single CI centre database of adult recipients using an Advanced Bionics HiRes Mid-Scala electrode was performed. Comparisons between recipients with a fully functioning ("intact") array and recipients with one or more electrodes deactivated included aided thresholds and sentence recognition scores (AzBio). Forty-eight of 164 recipients (29%) had one or more electrodes deactivated (mean = 2.5, median = 2.0, SD = 1.4). Reasons included sound quality concerns (n = 22), lack of percept (n = 16), non-auditory stimulation (n = 4), incomplete insertion (n = 3), and abnormal loudness growth (n = 3). There were no significant differences in pre-operative status or demographics between the cohorts (p > 0.05). Analyses found small (~5 dB) yet significant differences in aided thresholds between cohorts across most frequencies (p < 0.05). At 1 year post activation, the mean AzBio score for the intact cohort was 68%. Individuals with deactivated electrodes owing to poor sound quality (55%) or incomplete insertion (39%) scored significantly worse than the intact cohort (p < 0.05). Individuals with two or more deactivated electrodes scored significantly worse (48%) than the intact cohort (p < 0.05). Comparison of a subset of individual scores pre-deactivation (32%) and post-deactivation (57%) revealed a significant individual improvement following deactivation (p = 0.02). Electrode deactivation is a common occurrence and is associated with higher individual, but lower average group, speech perception scores.