Hearing preservation outcomes with a mid-scala electrode in cochlear implantation

Objective: To evaluate hearing preservation (HP) outcomes in adult cochlear implant recipients with a mid-scala electrode. Setting: Tertiary academic center. Patients: Adult patients implanted with a mid-scala electrode between May 2013 and July 2015. Interventions: Cochlear implantation. Main Outcome Measure(s): Age, sex, surgical approach, residual hearing changes post cochlear implantation, HP rates using different published classifications, and speech perception scores. Results: Fifty ears for 47 patients (mean age, 58.2 yr; range, 23-86) were implanted with the electrode. Recognizing that not all patients were true HP candidates and/or underwent generally accepted HP surgical techniques, 39 ears had preoperative low-frequency hearing (audiometric threshold-85 dB HL at 250 Hz), 24 preserved acoustic hearing postoperatively (75.0%). Patients who had preserved acoustic hearing were implanted via round window (N =18), extended round window (N =4), or via cochleostomy (N=2) approaches. Mean threshold elevation for lowfrequency pure-Tone average (125, 250, and 500 Hz) was 20.2 dB after surgery. 43.8% of patients had aidable lowfrequency hearing at activation, 30.0% at 6-months postoperatively, and 30.8% 1-year postoperatively. Using a formula outlined by Skarzynski and colleagues, at 6-months postoperatively, 15.0% of patients had complete HP, whereas 40.0% had partial HP. At 1-year, these percentages decreased to 0% and 38.5%, respectively. Age, type of approach, and perioperative steroid use were not correlated with HP outcomes at activation and 6-months postoperatively ( p>0.05). Conclusion: The mid-scala electrode evaluated allows preservation of low-frequency hearing in patients undergoing cochlear implantation at rates and degrees of preservation close to other reports in the cochlear implant literature.