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.