Wide versus limited cochlear duct exposure: impact on intraoperative cochlear implant measurements

Abstract Background To study the difference in intraoperative Evoked Compound Action Potential (ECAP) and electrode impedance measurements between wide versus limited exposure of the cochlear duct (CD) during cochlear implant (CI) surgery. Methods A retrospective observational study included all patients operated on with CI at a tertiary center who met the inclusion criteria: normal anatomy, receipt of the same electrode array, use of the same round window surgical technique, and either wide or limited CD exposure. Cases with inner ear anomalies, hypoplastic cochlear nerve, auditory neuropathy, and cochleostomy were excluded. The patients were divided into two groups: Group A (wide CD exposure) and Group B (limited CD exposure). Demographic data of both groups were collected. Intraoperative ECAP and electrode impedance were recorded, verified, and analyzed using R Language. Results The study included 153 cases, with an average age of 7.7 ± 9.5 years; males represented 53.6%. About 91.5% of implanted ears were right-sided. The intraoperative ECAP analysis for 12 electrodes showed no significant differences: wide CD exposure averages ranged from 18.0 ± 6.9 to 18.9 ± 6.8, compared with limited CD exposure averages ranging from 17.9 ± 5.3 to 17.5 ± 6.7 ( p > 0.05). Impedance measures also showed no significant differences: wide CD exposure averages were 7.8 ± 3.0 to 4.7 ± 1.9 kΩ compared to limited exposure from 8.1 ± 2.9 to 5.5 ± 3.7 kΩ ( p > 0.05). Conclusions The results show that both wide- and limited-cochlear-duct surgical methods resulted in comparable intraoperative ECAP and impedance measurements.