Assessing the Placement of the Cochlear Slim Perimodiolar Electrode Array by Trans Impedance Matrix Analysis: A...

Area of Science:

• Otolaryngology
• Biomedical Engineering
• Medical Imaging

Background:

• Cochlear implant (CI) electrode arrays offer improved insertion but are prone to intraoperative fold-overs or displacements due to high flexibility.
• Accurate electrode positioning is crucial for CI efficacy and is typically confirmed with high-resolution computed tomography (CT).
• The trans-impedance matrix test (TIM) is an electrophysiological imaging technique that can assess electrode position and detect folding.

Purpose of the Study:

• To evaluate the efficacy of TIM in monitoring the intraoperative insertion of a precurved slim modiolar electrode array.
• To correlate TIM patterns with electrode positions determined by high-resolution computed tomography (CT) in human temporal bones.

Main Methods:

• Sixteen slim modiolar electrode arrays were inserted into eight fresh human temporal bones.
• Eight electrodes were inserted correctly, while eight were intentionally folded over.
• Following insertion, both trans-impedance matrix analysis and Cone Beam CT (CBCT) were performed on all temporal bones.

Main Results:

• A correlation was observed between TIM patterns and radiological electrode positions.
• More homogeneous TIM patterns corresponded to better intracochlear electrode placement.
• TIM successfully detected electrode fold-overs in all cases where radiological findings confirmed the anomaly.

Conclusions:

• Trans-impedance matrix test patterns correlate well with cochlear implant electrode positions.
• The presence of a secondary ridge in the TIM pattern reliably indicates electrode tip fold-over.
• TIM is a valuable electrophysiological tool for controlling electrode positioning during cochlear implant surgery.