The misplaced cochlear implant electrode array.

OBJECTIVES/HYPOTHESIS: Evaluation of the clinical, electrophysiologic findings, the management plans of the misplaced cochlear implant electrode array and the possible causes of misplacement. Also to provide recommendations to prevent a repeat of cochlear implant electrode misplacement into abnormal sites.

STUDY DESIGN

Retrospective study.

METHODS

Pediatric cochlear implant recipients implanted from January 2012 till January 2018 whose electrode arrays were misplaced outside the cochlea into the surrounding structures.

RESULTS

Eight pediatric cochlear implant recipients, were identified to have a misplaced cochlear implant electrode array. Different sites of improper placement included one case in the eustachian tube, another one in the vestibule, one electrode array was found to be in the petrous apex lateral to the internal carotid canal, and another one in the internal auditory canal (IAC), and in three cases the electrode arrays were packed in the hypotympanum, and lastly an electrode array recoiled after perfect insertion and was found to be in the facial recess. Six cases were initially identified immediate because of their poor intraoperative implant testing which prompted imaging while in two cases, the one found in the petrous apex and the other one in the internal auditory canal (IAC) were diagnosed several months after surgery due to unsatisfactory auditory skills development or absent behavioral responses following implantation.

CONCLUSIONS

Electrode array misplacement may be due to either failure to identify the anatomical landmarks during surgery specially the infracochlear air cell track or unidentified inner ear malformation. The routine use of intraoperative electrophysiologic testing and postoperative imaging should help to avoid such complications. Misplacement is a rare but still correctable complication after cochlear implant surgery. The diagnosis of misplacement can be delayed for years and in this occasion, it is suspected when benefit from the implant is limited or absent. Once misplacement is diagnosed revision surgery has to be done.