Minimizing intracochlear trauma during cochlear implantation

Abstract

Several clinical trials have now demonstrated the feasibility and benefit of ipsilateral bimodal electric and acoustic stimulation of the auditory system for patients with varying degrees of hearing loss. Surgical techniques employed as a part of these investigations have been similar and focus on the implementation of atraumatic surgical principles. Each procedural step aims at minimizing intracochlear damage. A cochleostomy site inferior and slightly anterior to the round window membrane forms the basis for creating an opening into the scala tympani that avoids the critical structures of the inner ear. Electrode arrays have also been developed and refined to allow for relatively limited insertion-related damage. Using these specialized approaches, hearing preservation rates approaching 90% have been achieved. While impressive, this number reflects the conservation of only some degree of residual hearing. Complete preservation of hearing without any loss in pure tone thresholds and/ or discrimination abilities remains unusual, especially in subjects that have received a full-turn insertion. Thus, further work is clearly needed to optimize surgical protocols in an attempt to achieve total hearing preservation in all cases. A variety of biological and technological areas of investigation hold promise for fulfilling these goals. This report will review the current state of hearing preservation cochlear implantation as it relates to combined ipsi-lateral bimodal or electric acoustic stimulation.