Effect of early activation and perimodiolar electrodes on cochlear implant impedance

Cochlear implantation (CI) is a proven treatment for severe-to-profound hearing loss, yet outcomes vary widely due to individual, device, and surgical factors. Intracochlear changes, such as fibrosis and neo-ossification, influence electrode impedance and device performance, potentially affecting speech perception.

This study investigates the effects of early activation (EA) versus standard activation on intracochlear impedance telemetry across different electrode types (lateral vs. perimodiolar). It aims to assess whether EA reduces the impedance and improves CI outcomes.

This study involved 38 participants (54 CI ears) with Cochlear slim-straight or slim perimodiolar electrodes. Impedance telemetry was measured at four key time points, ranging from intra-operative to 12 months post-activation. Mixed-effects regression models evaluated the influence of activation timing and electrode type on impedance levels, with statistical significance determined using Bonferroni-corrected thresholds.

Perimodiolar electrodes demonstrated significantly lower impedances compared to lateral electrodes, particularly in EA cases. EA consistently resulted in reduced impedances across all cochlear regions, with the greatest reductions observed in the apical and middle regions at 3-6 months (p < 0.0001). By ≥ 1 year, impedance differences between activation modes diminished but remained significant in select regions (p = 0.012).

EA, particularly with perimodiolar electrodes, optimizes the electrode-tissue interface, reducing impedance and potentially improving CI performance. These findings highlight the clinical benefits of EA in enhancing CI outcomes and support its consideration in routine CI protocols.