Long-Term Stability of Electrical Stimulation in Children with Bilateral Cochlear Implants

The long-term stability of neural responses to cochlear implant (CI) stimulation and programmed stimulation levels remains unclear. Although smaller cohort studies suggest stabilization within months postimplant, reprogramming still consumes significant clinical time. The aim of this study was to investigate the resilience of the auditory nerve to prolonged stimulation from CIs and identify changes in the clinically provided stimulation levels over time. Stimulation parameters (n = 14,072 MAPs), electrophysiological auditory nerve thresholds (n = 23,215), and slopes of amplitude growth functions (n = 17,849) were obtained from 664 bilaterally implanted children (n = 1,291 devices) followed between September 2003 and July 2022. Stimulation parameters stabilized within 12 months following implantation for most, but not all, devices (75.3% and 75.4% of devices for C-levels and T-levels, respectively). Electrophysiological measures demonstrated very minor changes per year postimplant (slopes: mean [SE] = 0.03 [0.002] μV/CU/year [95% CI: 0.02-0.03]; thresholds: mean [SE] = 0.35 [0.06] CU/year [95% CI: 0.24-0.47]). While age at implantation did not relate to clinically meaningful changes in electrophysiological measures (slopes: mean [SE] = 0.02 [0.002] μV/CU/year [95% CI: 0.01-0.02]; thresholds: mean [SE] = 0.07 [0.08] CU/year [95% CI: -0.08 to 0.23]), stimulation levels decreased for children implanted at older ages (T-levels before plateau: mean [SE] = -0.47 [0.03] CU/year [95% CI: -0.53 to -0.42]; C-levels before plateau: mean [SE] = -0.78 [0.03] CU/year [95% CI: -0.85 to -0.72]). These findings indicate long-term neural and CI programming stability, suggesting potential for directing clinical time to care in areas other than reprogramming after the first year of implant use.