Insertion of Cochlear Implant Electrode Array Using the Underwater Technique for Preserving Residual Hearing

Objective: To describe a method of cochlear implantation in which the opening of the cochlea and the electrode array insertion are performed under water (underwater technique). Study Design: Retrospective patient review. Setting: Academic tertiary referral center. Patients: Fifteen implantations in children and adult patients with residual hearing at the frequencies 250, 500, and 1000 Hz on the unaided preoperative pure-tone audiometry were included in this study. Intervention(s): Cochlear implantation with a conventional full-length electrode, in which the opening of the cochlea and the electrode array insertion are performed after the tympanic cavity was filled with body-temperature Ringer solution. Main Outcome Measure(s): Changes on residual hearing 6 to 8 weeks after surgery and at subsequent follow-up appointments were analyzed. Preservation of residual hearing was defined as measurable postoperative threshold at the frequencies 250, 500, and 1000 Hz. Results: Overall postimplant hearing preservation 6 to 8 weeks after implantation was achieved in 13 of the patients (87%). Subsequent follow-up was performed on average 15.2 months after surgery (range, 7–32) in 14 out of 15 patients. At this late postoperative evaluation preservation of hearing was recorded in nine patients (64%), whereas in the remaining five patients (36%) no residual hearing was measured. Conclusion: The underwater technique offers a reliable nontraumatic method for electrode array insertions during cochlear implantation. The method respects the physiology of the cochlea und minimizes the pressure variations during cochlear opening and implantation.

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