Effects of CI Electrode Pullback on Electrophysiology, Audiology, and Postoperative Imaging

The position between the cochlea implant (CI) electrode array and the neural structures is crucial for the audiological outcome in CI surgery. Using the pullback technique, an electrode position closer to the modiolus can be achieved in perimodiolar electrode arrays. An approximation to the modiolus could be demonstrated by improved electrophysiological recordings after finalizing the pullback.

Forty-six patients were implanted with Nucleus Slim perimodiolar electrode arrays (Cochlear Pty, Sydney). After complete insertion of the electrode, a controlled pullback by about 1.5 mm was performed in 20 subjects. Electrophysiological measurements were performed before and after the pullback. Radiological examination was performed on the first day postoperative with flat-panel tomography.

Significant lower threshold neural response telemetry data were found between electrodes 7 and 11 after the pullback. Impedances remained unchanged during this procedure. Radiological and audiological examination revealed nonsignificant changes between both groups.

In this series, a pullback of the CI electrode after full insertion showed an improved electrophysiological pattern of neural response telemetry data intraoperatively. It remains a matter for further studies to correlate those data with long-term audiological outcome data.