Importance of Perimodiolar Electrode Position for Psychoacoustic Discrimination in Cochlear Implantation.

Hypothesis: Modiolar proximity of the cochlear implant electrodes and low impedance values have a positive effect on electrical pitch discrimination.

Background: The proximity of the cochlear electrode to the modiolar wall can determine changes in tissue and fluid environment. With the onset of soft-surgery techniques, the trauma caused during surgery has been reduced, minimizing fibrous growth.

Methods: Computed tomography-scan measurements of electrode-inner wall distance and psychoacoustic electrode discrimination tests were done. Neural Response Telemery and impedance data were used in the study.

Results: It was found that patients fitted with perimodiolar arrays have lower impedance values and smaller electrode-inner wall distances than those fitted with straight arrays. These variables were significantly correlated to electrode discrimination. It was found that a closer distance to the modiolus also results in better electrode discrimination.

Conclusion: Perimodiolar electrodes could be a better solution in terms of pitch discrimination both because they are closer to the modiolus and because their impedance is lower.