How Much Cochlea Do You Need for Cochlear Implantation?

Abstract

Objective: To assess the efficacy of cochlear implantation (CI) after surgical removal of sporadic intracochlear or intravestibulocochlear schwannomas. Study Design: Nonconcurrent cohort study. Setting: Monocentric study at a tertiary referral center. Patients: 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. Interventions: Partial or subtotal cochleoectomy for tumor removal and single-stage CI. Outcome Measures: Main outcome measure: word recognition score for monosyllables in quiet at 65 dB SPL. Results: 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. Conclusions: 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.

Management of transmodiolar and transmacular cochleovestibular schwannomas with and without cochlear implantation

“…These results are also similar to or better than those reported in small case series with CI after translabyrinthine resection of classical VS (IAC ± CPA) [4,17,22,42,57]. The WRS65 values, however, were not as good and consistent as those reported for patients with CI after removal of solely intracochlear and intravestibulocochlear schwannomas [35,36,56]. There were no serious adverse events.…”

“…Similar initial results for hearing rehabilitation are available for CI after radiotherapy [9,28,31] and with a wait and test and scan strategy [5]. For ILS limited to the inner ear, surprisingly good results with CI with respect to speech understanding have been reported, despite substantial cochlear trauma from the surgical tumor removal [2,35,36,38].…”

“…Depending on tumor location and extension, surgery involved a translabyrinthine/transotic approach to the IAC and the CPA or a transmeatal partial or subtotal cochleoectomy (for details see . Table 2 and "Results"; [2,33,35,36,38,39]).…”

“…Selection of the type of cochlear implant and electrode array was based on experience and audiological results with previous surgery for ILS [35][36][37][38]. In addition, we ascribed to the hypothesis that a perimodiolar electrode array position with close contact of the electrode pads to the spiral ganglion cells in Rosenthal's canal (here: CI512, CI612, CMD electrodes) with cartilage and fibrosis lateral to the array will lead to reduced spread of the electric field, contributing to a good hearing result after partial and subtotal cochleoectomy [56].…”

“…5d-h). Incomplete tumor removal was carried out by a transmeatal partial or subtotal cochleoectomy [33,35,36,38] or via push-through or pullthrough techniques (also called pipe cleaner, beach towel, or dental floss techniques) [2,26,36,39]. The video (2D and 3D versions, see QR code) shows the transmeatal surgical removal of the intracochlear tumor parts through a partial cochleoectomy and CI in the patient with NF2.…”