Outcomes review of modern hearing preservation technique in cochlear implant

Preservation of residual hearing in cochlear implantation is a main concern for patients and otologists. New electrode arrays as well as development of minimally invasive technique have allowed the expansion of indication criteria for cochlear implantation. The loss of residual low-frequency hearing is thought to be the result of many factors. Opinions differ in regards with the electrodes array characteristics, the surgical implantation technique and the pharmacological therapy used.

The aim of this research is to analyze the available information pertaining to hearing preservation with cochlear implantation.

Both cochleostomy and round window approaches are adequate, but should rely on the anatomic position of the round window membrane. No electrode design had a higher rate of hearing preservation, either a standard or shorter length was used, or a straight or contoured array. The speed of insertion has a significant impact on hearing preservation and vestibular function. A slow insertion should be used for all cochlear implant insertion, hearing preservation or not. However, the optimal speed of insertion is still unclear. Moreover, the use of steroids regardless of the route or the timing, along with intraoperative topical steroids, had a positive impact on hearing preservation.

Classic atraumatic insertion maneuvers, very slow and delicate insertion and the use of intraoperative corticosteroids improve hearing outcomes. Whichever the surgeon's preferences, all surgical modifications are aimed at the same goal: protection of the delicate intracochlear structures with preservation of residual low-frequency hearing to improve speech perception abilities.