The "pull-back" technique for Nucleus 24 perimodiolar electrode insertion.

Abstract

To observe the influence of electrode pull-back after cochlear implant insertion of Nucleus 24 perimodiolar electrodes. In a prospective intraoperative study, we analyzed the impedances, neural response telemetry responses, and the spread of excitation after cochlear implant electrode insertion and compared these data to those obtained after a subsequent, controlled pull-back of the electrode. Postoperative depth of electrode insertion was controlled by x-ray. Tertiary referral center. Six patients (4 male, 2 female; 18 to 69 years) were implanted with a Nucleus 24 (RCA) cochlear implant with a perimodiolar electrode. After a controlled pull-back, a significant decrease of the spread of excitation at the stimuli electrodes 5, 10, 15, and a nonsignificant decrease at stimuli electrode 20 compared to the recordings after the primary normal insertion procedure was found. The mean electric compound action potential amplitude was increased with an apical-to-basal tendency. Impedances remained unchanged by the pull-back. Mean insertion depth at the postoperative x-ray control was 372 degrees (+/- 10.2). Controlled cochlear implant electrode pull-back is a novel technique that optimizes objective intraoperative electrophysiological recordings in patients implanted with a Nucleus 24 perimodiolar cochlear implant by a greater approximation of the electrode to the modiolus.