Hearing preservation in cochlear implantation for electric acoustic stimulation

TLDR

The study aims to assess whether atraumatic cochlear implant electrode insertion can preserve low‑frequency hearing and to explore potential improvements with newer electrode designs. Twenty‑one patients received a MED EL C40+ cochlear implant via an atraumatic insertion technique; pre‑ and postoperative pure‑tone thresholds and speech discrimination were measured to evaluate hearing preservation. Atraumatic insertion preserved low‑frequency hearing in 85.7% of patients (18/21), with complete preservation in 61.9% and partial in 23.8%; speech discrimination improved markedly with combined electric and acoustic stimulation, supporting the feasibility of hearing preservation.

Abstract

Objective To evaluate the possibility of preservation of low-frequency hearing in atraumatic cochlear implant electrode insertion procedures for combined, ipsilateral electric and acoustic stimulation. Material and Methods A total of 21 patients were implanted with a MED EL C40+ cochlear implant using an atraumatic electrode insertion technique to preserve residual low-frequency hearing. Pure-tone audiometric thresholds were measured pre- and postoperatively to evaluate the degree of preserved hearing. Speech discrimination tests in quiet and with background noise were performed in a patient with successful hearing preservation. Results Using the atraumatic electrode insertion procedure with an insertion depth of 360° (18–24 mm), hearing preservation could be achieved in 18/21 patients (85.7%). Three patients (14.3%) lost their residual low-frequency hearing after the implantation. Residual hearing was preserved completely in 13 patients (61.9%) and partial hearing preservation was possible in 5 (23.8%). Preliminary speech discrimination tests showed a dramatic benefit for the combined electric and acoustic stimulation mode compared to cochlear implantation alone. Conclusion Preservation of low-frequency hearing in cochlear implantation is possible in patients implanted because of profound high-frequency deafness. With the development of new, more atraumatic electrode designs, preservation of residual hearing should be further improved.