Localisation by Impedance

Accurate intracochlear positioning of electrode arrays is critical for optimizing auditory outcomes during cochlear implantation (CI). While radiographic imaging remains the standard for postoperative evaluation, transimpedance matrix (TIM) measurements have emerged as a promising intraoperative technique for real-time assessment of electrode placement, particularly with a slim modiolar electrode array.

This retrospective observational study included 15 patients (24 ears) who underwent CI using CI532® and CI632® electrode arrays. Intraoperative TIM data were obtained and compared with intraoperative and immediate postoperative radiographic imaging data to determine the accuracy and reliability of TIM in detecting electrode placement anomalies. The electrode positioning patterns were analyzed using TIM heatmaps, with a focus on the voltage gradient distribution and identification of the electrode tip fold-over (TFO).

Of the 24 CIs, 23 (96%) exhibited a regular TIM voltage distribution consistent with proper modiolar placement. A single instance of TFO (4%) was identified intraoperatively using TIM and confirmed via radiographic imaging. The electrode was reinserted following intraoperative correction with TIM and imaging, subsequently confirming the optimal placement. In all remaining cases, the TIM findings were in concordance with radiological assessments.

TIM may be a reliable intraoperative monitoring tool for CI using slim modiolar CI532® and CI632® electrode arrays position during CI. Their ability to accurately detect deviations in electrode configuration, such as the TFO, affirms their potential to augment surgical precision, eliminate the need of intraoperative radiation exposure by providing real-time feedback, minimize postoperative imaging requirements, and enhance patient outcomes. Further prospective studies with larger cohorts are warranted to validate these preliminary findings and establish standardized protocols for clinical implementation.