Electrode Location and Audiologic Performance after Cochlear Implantation: A Comparative Study between Nucleus CI422 and CI512 Electrode Arrays

Objectives: 1) Compare rates of scala tympani (ST) insertion between Nucleus CI422 Slim Straight electrodes and Nucleus CI512 Contour Advance electrodes; 2) examine audiometric performance with both electrode arrays, while controlling for electrode location. Setting: Tertiary academic hospital. Patients: Fifty-six post-lingually deafened adults undergoing cochlear implant (CI). Main Outcome Measures: Primary outcome measures of interest were scalar electrode location and postoperative audiologic performance. Results: Fifty-six implants in 49 patients were included; 20 were implanted with Nucleus CI422 Slim Straight electrodes, and 36 were implanted with Nucleus CI512 Contour Advance electrodes. Overall, 62.5% (35 of 56) of implants had all electrodes located within the ST. Significantly, higher rates of ST insertion (90%) were observed for Nucleus CI422 Slim Straight electrodes when compared with Nucleus CI512 Contour Advance electrodes (47.2%) (p = 0.002). In regards to audiologic performance, consonant-nucleus-consonant (CNC) scores were significantly higher for Nucleus CI422 Slim Straight electrodes (55.4%) compared with Nucleus CI512 Contour Advance electrodes (36.5%) (p = 0.005). In addition, AzBio scores were better for Nucleus CI422 Slim Straight electrodes (71.2%) when compared with Nucleus CI512 Contour Advance electrodes (46.7%) (p = 0.004). Controlling for ST insertion, higher AzBio scores were again observed for Nucleus CI422 Slim Straight electrodes (p = 0.02). Conclusions: The results of this study demonstrate that the Nucleus CI422 Slim Straight electrode is more likely to reside entirely within the ST when compared with the Nucleus CI512 Contour Advance electrode. Furthermore, AzBio scores were superior for patients with Nucleus CI422 Slim Straight electrodes in all patients, as well as those with only ST insertions.