Conservation of Residual Acoustic Hearing After Cochlear Implantation

TLDR

In severely to profoundly hearing‑impaired patients, studies often overestimate hearing conservation due to a ceiling effect. The study tested whether partial hearing conservation can be achieved after cochlear implantation with a long perimodiolar electrode. Twenty‑eight adults with measurable pre‑operative hearing underwent a prospective, single‑subject repeated‑measures design using the Nucleus Freedom Contour Advance electrode, with pre‑ and post‑implant pure‑tone thresholds and speech scores assessed at an average of nine months. Pure‑tone hearing was conserved in 89% of patients, yet residual speech perception was not preserved—only one subject showed partial open‑set speech recognition, and implant performance did not improve in those with hearing conservation.

Abstract

This study was designed to test the hypothesis that partial hearing conservation is attainable after cochlear implantation with a long perimodiolar electrode. Surgical strategies for hearing conservation during cochlear implantation are described.Prospective, single-subject, repeated-measures design.Academic tertiary care center.Twenty-eight severely to profoundly hearing-impaired adult cochlear implant recipients who had some measurable hearing preoperatively.Cochlear implantation using Nucleus Freedom Contour Advance electrode.Preimplant and postimplant pure-tone thresholds and speech recognition scores were obtained to determine the incidence and degree of conserved hearing at a mean interval of 9 (+/-3.9) months.Thirty-two percent of subjects experienced complete conservation of hearing (0- to 10-dB loss), and 57% experienced partial conservation of hearing (>11 dB) after implantation. However, open-set speech recognition was partially conserved in only one subject. Cochlear implant performance was not better in patients with conservation of residual hearing.Conservation of pure-tone hearing was possible in 89% of implanted patients; however, residual speech perception was not conserved with this long perimodiolar electrode. A ceiling effect tends to inflate the prevalence of hearing conservation in implantation studies of severely to profoundly hearing-impaired patients.