Mechanism underlying and prevention of electrode migration in cochlear implants.

PURPOSE: We investigate the clinical manifestations, mechanisms, and methods of preventing electrode migration in Cochlear Implantation (CI) patients, based on our practical experience with this problem.

STUDY DESIGN: This is a retrospective study in a single center.

METHODS: We retrospectively reviewed electrode migration in 4 (0.75%) of 532 patients who underwent CI at our tertiary institution from January 2002 to December 2022. Pre- and post-operative pure-tone audiometry, word recognition score, aided functional gain test, and sound field speech intelligibility test were evaluated.

RESULTS: All four patients underwent CIs with the straight electrode type. The following events or symptoms were observed in the patients before confirming electrode migration: an increase in high-frequency thresholds during the post-operative aided functional gain test and a decline in scores on the sound field speech intelligibility test. Electrode migration was confirmed through transocular view X-ray or temporal bone computer tomography. Two patients showed coiled electrodes within the mastoid cavity; while in the others, the electrodes were observed to be floating inside the cavity. To prevent migration of electrodes due to these issues, we mixed bone paste collected during the drilling of the mastoid cavity with glue and used it to secure the electrodes in place.

CONCLUSION: Electrode migration can result in a decrease in hearing ability and may necessitate a revision surgery to adjust the electrode placement. The main factors affecting electrode placement include the position of electrode within the mastoid cavity and the elasticity of straight electrodes. It is important for surgeons to recognize the factors that increase the risk of electrode migration and to take preventative measures to reduce this risk.