Estimating Performance Using Tonotopic Measurements of Intracochlear Electrocochleography: Comparison of Lateral Wall and Perimodiolar Arrays.

Abstract

To assess intracochlear electrocochleography (ECochG) for estimating cochlear implant (CI) performance for lateral wall and perimodiolar electrode arrays. Prospective cohort study. Tertiary referral center. From December 2021 to June 2024, ECochG was measured intraoperatively using the Active Insertion Monitoring (AIM) system by Advanced Bionics. After insertion, multifrequency tone bursts were delivered via a sound tube from 250 Hz to 2 kHz at 95 to 105 dB HL with recordings at each internal electrode. Using spectral analysis, the maximal amplitude (MA) response electrode was identified by frequency and summed into a single value of total response (MA-ECochG-TR). Postoperative CI performance was routinely monitored. Of 57 participants with ECochG recordings, 43 completed 6-month testing. Of these, 23 were perimodiolar (Mid-Scala [MS]), and 20 were lateral wall (SlimJ [SJ]). MA-ECochG-TR had a moderately strong positive correlation to 6-month consonant-nucleus-consonant (CNC) word scores for MS cases (r = 0.73, 95% CI [0.46-0.88], P < .001), but showed no significant correlation for SJ cases (r = 0.04, 95% CI [-0.41 to 0.47], P = .87). For the 13 SJ recipients without electroacoustic stimulation (EAS), there was a moderate, non-significant positive correlation between MA-ECochG-TR and 6-month CNC (r = 0.44, 95% CI [-0.14 to 0.80], P = .13). MA-ECochG-TR independently estimates performance for perimodiolar arrays. Intracochlear ECochG is less predictive for lateral wall arrays; this may be due to confounding from EAS (though this was not statistically significant) or from signal degradation with a larger electrode-modiolar distance.