An evidence-based guide for intraoperative cochlear implant backup use

Intraoperative assessment of electrode function and position is essential for cochlear implant outcomes. Electrophysiological measures and radiographic imaging modalities have been used for this purpose. This study was conducted to determine the relative utility of X-ray, impedance measurements and ECAP for cochlear implant function.

A retrospective review was conducted for 132 children (age range from 5 to 13 years old) who underwent cochlear implantation. 3 months after switch on, aided free field (FF) and Ling Six Sounds were compared between patients who had intraoperative ECAP and those who had not intraoperative ECAP (but with normally located electrode array as confirmed by plain X-ray).

Only 4 cases (3%) had abnormal impedance measurements that became normal after reinsertion of the same electrode array. 3 cases (2.3%) showed malposition of the electrode array on plain radiograph. They underwent immediate revision. 11 cases (8.3%) had absent intraoperative ECAP response for all electrodes, and 4 cases (3%) had absent intraoperative ECAP response for basal electrodes. These devices were not explanted at the time of surgery. 3 months after switch on, FF and the ling 6 sounds were tested for all patients. No statistical significant differences were found between cases with normal intraoperative ECAP and those who gave no response in ECAP.

From the study we can conclude that plain X-ray is the guideline for backup use. Results of plain X-ray impacted surgical decision making and led to the use of the backup device. In patients with correct electrode placement in normally developed cochlea as detected by X-ray, it is not recommended to use the backup even if there is no intraoperative ECAP. Also, it is recommended to follow how those children performed after 1 or 2 years to see if making the decision of using or not a backup device based in electrophysiology measures vs X-ray made a difference.