Electrocochleography-Guided Pull-Back Technique of Perimodiolar Electrode for Improved Hearing Preservation

Objective To evaluate whether electrocochleography (ECochG)-guided pull-back of the perimodiolar electrode improves perimodiolar proximity, hearing preservation (HP), and cochlear implant performance. Study Design Prospective cohort study Setting Tertiary referral center. Patients 77 adult CI recipients with residual acoustic hearing (low-frequency pure-tone average of 125, 250, 500 Hz; LFPTA ≤80 dB HL) Intervention Unilateral implantation, comparing conventional insertion (N = 31) with ECochG-guided electrode pull-back (N = 46). The guided method uses active ECochG from the apical electrode during adjustment and post-insertion electrode sweep to identify "tonotopic response"(defined as maximum response for 250 Hz at most apical electrode on electrode sweep). Main Outcome Measures Perimodiolar proximity (wrapping factor on postoperative CT); speech-perception testing (CNC, AzBio in noise +10 dB SNR); and HP at 3 and 6 months post-activation (defined as LFPTA ≤80 dB HL). Results Of the subjects undergoing ECochG-guided insertion, 36 required pull-back based on lack of tonotopic responses, whereas the remaining 10 exhibited "optimal responses"post-insertion, needing no adjustment. Improved perimodiolar proximity was achieved with the ECochG-guided method (mean wrapping factor difference, 6.4; 95% CI, 3.0-9.9). The LFPTA shift was smaller using ECochG-guided pull-back when compared with conventional insertion by 17.0 dB HL (95% CI, 8.3-25.7) and 14.8 dB HL (95% CI, 6.5-23.2) at 3 and 6 months, respectively. Forty percent achieved HP using ECochG-guided pull-back versus 27.5% without. There was no difference in CNC scores among both cohorts, but AzBio in noise scores at 6 months was improved in the ECochG-guided pull-back cohort (mean difference, 19.1%; 95% CI, 5.8-32.4). Conclusions ECochG-guided pull-back increased perimodiolar proximity and HP rates. Although there was no difference in speech perception performance in quiet, a significant improvement was noted in noisy conditions, potentially attributable to HP and the utilization of hybrid stimulation.