How Much Cochlea Do You Need for Cochlear Implantation?

Abstract

To assess the efficacy of cochlear implantation (CI) after surgical removal of sporadic intracochlear or intravestibulocochlear schwannomas. Nonconcurrent cohort study. Monocentric study at a tertiary referral center. Patients with tumor resection and CI between 2011 and 2018 and a historic control group of CI patients matched by age, CI electrode type, and follow-up. Partial or subtotal cochleoectomy for tumor removal and single-stage CI. Main outcome measure: word recognition score for monosyllables in quiet at 65 dB SPL. Sixteen patients with tumor removal and CI (6 female, 10 male; mean age 55 ± 14 years) and 16 control patients (6 female, 10 male; mean age 55 ± 15 years) were identified. In the tumor group, surprisingly good word recognition scores were reached even after substantial structural defects in the cochlear capsule. While 12 months after cochlear implantation mean word recognition score for monosyllables in quiet was 58% (SD: 26) and 41% (SD: 26) in the control groups, it was 75% (SD: 19%) in the tumor group. In patients with intracochlear schwannomas, despite substantial structural damage to the cochlear capsule by partial or subtotal cochleoectomy, a tendency toward better performance with respect to word recognition with CI was observed as compared with other CI patients. The surprisingly good functional results despite substantial cochlear trauma may change clinical thinking with respect to cochlear implantation also beyond this special indication.