Can Electrocochleography Help Preserve Hearing after Cochlear Implantation with Full Electrode Insertion?

Objectives To evaluate the utility of intracochlear electrocochleography (ECochG) monitoring during cochlear implant (CI) surgery on postoperative hearing preservation. Study Design Prospective, randomized clinical trial. Setting Ten high-volume, tertiary care CI centers. Patients Adult patients with sensorineural hearing loss meeting the CI criteria who selected an Advanced Bionics CI. Methods Patients were randomized to CI surgery either with audible ECochG monitoring available to the surgeon during electrode insertion or without ECochG monitoring. Hearing preservation was determined by comparing preoperative unaided low-frequency (125-, 250-, and 500-Hz) pure-tone average (LF-PTA) to postoperative LF-PTA at CI activation. Pre- and post-CI computed tomography was used to determine electrode scalar location and electrode translocation. Results Eighty-five adult CI candidates were enrolled. The mean (standard deviation [SD]) unaided preoperative LF-PTA across the sample was 54 (17) dB HL. For the whole sample, hearing preservation was "good"(i.e., LF-PTA change 0-15 dB) in 34.5%, "fair"(i.e., LF-PTA change >15-29 dB) in 22.5%, and "poor"(i.e., LF-PTA change ≥30 dB) in 43%. For patients randomized to ECochG "on,"mean (SD) LF-PTA change was 27 (20) dB compared with 27 (23) dB for patients randomized to ECochG "off"(p = 0.89). Seven percent of patients, all of whom were randomized to ECochG off, showed electrode translocation from the scala tympani into the scala vestibuli. Conclusions Although intracochlear ECochG during CI surgery has important prognostic utility, our data did not show significantly better hearing preservation in patients randomized to ECochG "on"compared with ECochG "off."