Electrophysiological effects of electrode pull-back in cochlear implant surgery

Abstract

Conclusion. The surgical technique of electrode pull-back had a significant improving effect on the spread of excitation (SOE). However, the long-term clinical and audiological outcome of this modified surgical technique should be a subject of further studies. Objective. To observe the intraoperative electrophysiological effects of a surgical electrode insertion technique (i.e. pull-back) in cochlear implantation. Patients and methods. The influence of the pull-back technique on intraoperatively recorded electrophysiological parameters (including T-NRT, ECAP amplitude, SOE) was investigated in a prospective, non-randomized, intraoperative study. In addition, we observed the correlation of insertion depth and SOE differences after a controlled electrode pull-back. We implanted 13 patients (aged 18–76 years) with a Nucleus 24CI RE cochlear implant with a perimodiolar electrode. Results. After a controlled pull-back, a significant decrease of the SOE at different electrodes (upon recording from electrodes 5, 10, 15) was observed. Electrode 10 was the SOE area with the most significant and homogeneous changes after pull-back. The change in the ECAP amplitudes was highly variable in correlation with the changes in the SOE.