Intraoperative localization of the electrode of the cochlear implant via Transimpedance Matrix Measurements

Objective During cochlear implantation, electrophysiological tests are performed to document correct technical functioning of implant and electrodes. The data from transimpedance matrix (TIM) measurements enables the generation of a heat map or TIM profile measuring the spatial distribution of voltage in relation to the electrode array. In rare cases, the electrode array of the cochlear implant (CI) is malpositioned (i.e. tip fold-over).

Methods Based on 200 patients with correct electrode positioning, regular SOE measurements and intraoperative imaging, the “regular” heat map profile was compared to aberrant heat map profiles and corresponding SOE measurements and imaging.

Results In the rare cases of tip-fold over, electrode buckling and extracochlear placement of the electrode array, intraoperative TIM measurements showed irregular results. In two cases, irregular TIM profiles were registered, but SOE data and 3D X-ray of the temporal bone didn’t display deviated electrode positioning. Mispositioning was successfully revised at the same surgery and all measurements normalized once the electrode position had been corrected.

Conclusion No false negative cases were detected if TIM measurements were used for the detection of electrode malpositioning. Correspondingly, TIM measurements successfully detect electrode malposition in an intraoperative setting. Different heat map patterns may be observed depending on location and type of malposition.

Publication History

Article published online:
24 May 2022