The Effect of Etiology, Array Type and Duration of Deafness on Focused Detection Thresholds in Cochlear Implant Listeners.

Cochlear implants (CIs) are considered effective at restoring some hearing abilities to individuals with severe hearing loss. However, there is considerable variability in performance outcomes among adults with CIs. One likely source of variability is the quality of the electrode-neuron interface (ENI), which describes how well implanted electrodes stimulate nearby spiral-ganglion neurons (SGNs) in the cochlea. Absolute thresholds, measured via focused electrical stimulation, have been proposed as a behavioral estimate of ENI. In this retrospective study, focused-stimulation threshold patterns were compared for 92 ears from 74 adult cochlear implant listeners with various etiologies, durations of deafness, and electrode array types. The results showed that CI listeners implanted with a pre-curved array tended to have lower overall focused thresholds than listeners with straight arrays, as well as a threshold profile with lower (better) thresholds at each end of the array and highest thresholds near the middle of the array. CI listeners with etiologies related to auto-immune dysfunction, such as Meniere's disease, tended to have the opposite profile, with lowest thresholds near the middle of the array. No significant effect of duration of deafness on focused thresholds was observed. Further investigation into which demographic and device factors affect focused thresholds, and therefore potentially ENI, could shed light on the variability of CI outcomes and guide development of individualized treatment strategies.