Evaluation of a Transimpedance Matrix Algorithm to Detect Anomalous Cochlear Implant Electrode Position

Area of Science:

• Otoacoustic Emissions
• Electrophysiology
• Medical Devices

Background:

• Transimpedance measurements of cochlear implant electrodes can detect anomalous placements like tip fold-over (TFO).
• Analyzing transimpedance may replace intraoperative or post-operative radiological imaging for detecting misplacements.
• A previously developed transimpedance algorithm aimed to detect deviations from normal electrode position to identify TFO intraoperatively.

Purpose of the Study:

• To estimate the specificity of a TFO detection algorithm in patients through a prospective study.
• To evaluate the algorithm's effectiveness in identifying normally inserted electrode arrays.

Main Methods:

• Intracochlear voltages were recorded intraoperatively for 157 ears using Custom Sound™ EP 5 software for Nucleus® CI512 and CI532 electrode arrays.
• A 22 × 22 transimpedance matrix (TIM) was analyzed by the algorithm, displaying results as an intraoperative heatmap.
• The algorithm calculates the gradient phase range from transimpedance gradients and phase angles, classifying TFO if it exceeds a threshold.

Main Results:

• After excluding 9 ears due to missing or anomalous matrices, 148 data sets were analyzed.
• The algorithm achieved an average specificity of 98.6% (95.80%-99.75%) for detecting TFO in patient electrode arrays.

Conclusions:

• The transimpedance algorithm is an effective screening tool for identifying TFOs with acceptable specificity.
• The algorithm has a positive predictive value of 76% for TFO, with an estimated incidence of 4% in perimodiolar arrays.
• Easy intraoperative application allows the algorithm to be a routine clinical tool for confirming correct cochlear implant electrode placement.