Hearing Preservation With a New Atraumatic Lateral Wall Electrode

Introduction: Many individuals have some residual hearing which should be preserved with cochlear implantation. To achieve this goal electrode arrays must fulfil certain design requirements. A new thin lateral wall electrode array (HiFocus SlimJ) was systematically designed on the basis of mu CT studies of human cochlea anatomy. The primary objective of this study was to report on initial retrospective hearing preservation results from a cohort of subjects consecutively implanted with this electrode. Secondary objectives were to report on insertion depth and speech perception results for this new array. Methods: Twenty subjects with considerable residual hearing in low frequencies were consecutively implanted with the SlimJ electrode array. The electrode was inserted slowly through the round window and the insertion process was controlled by intracochlear electrocochleography measuring cochlear microphonics through the cochlear implant. Postoperative cone beam computed tomography was conducted and precise scalar location and angular insertion depth was estimated following image fusion with the preoperative images. Results: Low frequency hearing at 1 month postsurgery was preserved within 30 dB HL in 85% of subjects and within 15 dB HL in 50% of subjects. Mean angular insertion depth was 393 degrees (SD 62 degrees) with a range from 294 to 520 degrees. All electrode contacts in all subjects were identified within scala tympani. Conclusion: The SlimJ electrode array is easy to handle for atraumatic insertion through the round window, adjusted insertion depth controlled by electrocochleography measurements, and reliable fixation at the posterior tympanotomy. Hearing preservation rates are encouraging on the short term. We aim to further report on larger data sets and long-term outcomes.