Electrode Location and Angular Insertion Depth Are Predictors of Audiologic Outcomes in Cochlear Implantation

TLDR

The study investigates how electrode type and surgical approach influence scalar electrode location and how that location relates to postoperative audiologic performance. The study enrolled 220 post‑lingually deafened adults at a tertiary academic hospital, recording scalar electrode location and postoperative audiologic performance, with 68 % of implants showing electrodes solely in the scala tympani. Perimodiolar and mid‑scala electrodes and cochleostomy approaches were associated with higher rates of scala vestibuli insertion, whereas round‑window and extended round‑window approaches reduced SV insertion; greater angular insertion depth, scala tympani placement, and younger age predicted higher consonant‑nucleus‑consonant scores, while scala vestibuli insertion and older age were linked to lower scores.

Abstract

1) Investigate the impact of electrode type and surgical approach on scalar electrode location; and 2) examine the relation between electrode location and postoperative audiologic performance.Tertiary academic hospital.Two hundred twenty post-lingually deafened adults undergoing cochlear implant (CI).Primary outcome measures of interest were scalar electrode location and postoperative audiologic performance.In 68% of implants, electrodes were observed to be located solely in the scala tympani (ST). Multivariate analysis demonstrated perimodiolar (PM) and mid-scala (MS) electrodes were 22.4 (95% CI: 6.3-80.0, p < 0.001) and 55.0 (95% CI: 9.7-312.8, p < 0.001) times more likely to have at least one electrode in the scala vestibuli (SV) compared with lateral wall (LW) electrodes, respectively. Compared with cochleostomy (C), round window (RW) and extended round window (ERW) approaches demonstrated 70% reduction in SV insertion (RW: OR 0.28, 95% CI: 0.1-0.8, p = 0.01; ERW: OR 0.28, 95% CI: 0.1-0.7, p = 0.005). Examining postoperative audiometric performance, consonant-nucleus-consonant (CNC) score increased 0.6% with every 10 degrees increase in angular insertion depth beyond the group minimum of 208 degrees (coefficient 0.0006, 95% CI: 0.0001-0.001, p = 0.03). SV insertion was associated with a 12% decrease in CNC score (coefficient -0.12, 95% CI: -0.22 to -0.02, p = 0.02). CNC score decreased 0.3% for every 1 year increase in age (coefficient -0.003, 95% CI: -0.006 to -0.0006, p = 0.02).Electrode design and surgical approach were predictors of scalar electrode location. Specifically, LW electrodes showed higher rates of ST insertion compared with PM or MS. RW and ERW approaches showed higher rates of ST insertion when compared with C. In regards to performance, ST insertion, younger age, and greater angular insertion depth were predictors of improved CNC scores.