The Relation of Cochlear Implant Electrode Array Type and Position on Continued Hearing Preservation.

Abstract

To analyze the relationship of electrode array (EA) type and position on hearing preservation longevity following cochlear implantation. Retrospective chart review. Tertiary referral center. Adult cochlear implant recipients between 2013 and 2019 with hearing preserved postoperatively and postoperative CT scans. CT scan analysis of EA position. Stepwise regression to determine influence of EA position, EA type, and patient demographics on postoperative low frequency hearing. Low frequency pure tone average (LFPTA), LFPTA shift, angular insertion depth, base insertion depth, scalar position, mean perimodiolar distance. Of 792 cochlear implant recipients, 121 had preoperative LFPTA <80 dB HL with 60 of the 121 (49.6%) implanted with straight, 32 (26.4%) with precurved, styletted, and 29 (24.0%) implanted precurved, nonstyletted EA. Mean follow up was 28.6 months (range 1-103). There was no statistically significant difference in activation, 6- and 12-month, and last follow-up LFPTA (125, 250, and 500 Hz) shift based on EA type (straight p = 0.302, precurved, styletted p = 0.52, precurved, nonstyletted p = 0.77). Preoperative LFPTA and age of implantation were significant predictors of LFPTA shift at activation, accounting for 30.8% of variance ( F [2, 113] = 26.603, p < 0.0001). LFPTA shift at activation, scalar position, and base insertion depth were significant predictors of variability and accounted for 39.1% of variance in LFPTA shift at 6 months ( F [3, 87] = 20.269, p < 0.0001). Only LFPTA shift at 12 months was found to be a significant predictor of LFPTA shift at last follow up, accounting for 41.0% of variance ( F [1, 48] = 32.653, p < 0.0001). Patients had excellent long-term residual hearing regardless of EA type. Age, preoperative acoustic hearing, and base insertion depth may predict short term preservation, while 12-month outcomes significantly predicted long-term hearing preservation.