Is there a difference in the spread of excitation at different electrode locations along the cochlea?

To identify whether there are differences in the amplitude and width of spread of excitation (SOE) across the apical, medial and basal regions of the cochlea.

Cross-sectional retrospective study approved by the Ethics Committee of the institution. The study included adults with postlingual deafness, undergoing cochlear implant (CI) surgery, with present intraoperative neural responses in which the SOE was investigated in the basal (6), medial (11) and apical (16) electrodes. Neural response telemetry thresholds, peak amplitudes (µv) of the SOE function and SOE width in millimeters were collected and grouped by the electrode array type for analysis using the Mann Whitney and Kruskal Wallis tests.

Seventy-one subjects were selected, 27 with perimodiolar array and 44 with straight array. There were no significant differences in the peak amplitudes among evaluated electrodes in both groups. However, SOE width (mm) of the medial electrode was significantly wider in both arrays, followed by the width of the basal electrode.

Although the SOE amplitude was similar suggesting similar neural recruitment in different regions of the cochlea, wider spread was found in the medial region even in the perimodiolar array. Thus, the use of objective tests will become increasingly important to assist in CI mapping, aiming for more effective and individualized programming.