Transimpedance Matrix Measurements Reliably Detect Electrode Tip Fold-over in Cochlear Implantation

Abstract

Objective: During cochlear implantation, electrophysiological tests are performed to document safe technical functioning of implant and electrodes. In rare cases, the apical part of the electrode folds over during insertion. The data from transimpedance matrix (TIM) measurements enable the generation of a heat map or TIM profile measuring the spatial distribution of voltage. The aim of this study was to determine the accuracy of heat-map TIM profiles and compare them with spread of excitation (SOE) measurements and intraoperative imaging for prediction of electrode malposition. Study Design: Non-randomized study. Setting: Tertiary referral center. Patients and Interventions: One hundred patients who underwent cochlear implantation with completed TIM measurements, SOE data and perioperative imaging met the inclusion criteria and were enrolled. Main Outcome Measure: The electrophysiological data on the electrode array positioning was compared with temporal bone imaging.Results: In seven cases, 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. A 3D x-ray of the skull displayed electrode tip fold-over in four cases and electrode buckling in one case. Sensitivity of TIM measurements and SOE data was 100%, specificity of TIM measurements was 97.89%, and specificity of SOE data was 98.93%. Conclusion: Out of 100 patients using TIM measurements for detection of electrode malpositioning, no false negative cases were detected. TIM measurements successfully detect electrode malposition in an intraoperative setting. Different heat map patterns may be observed depending on location and type of malposition.

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

“…However, there are some important points to be kept in mind: Some of these studies did not achieve significantly different results in TIM conditions, and there was considerable variation among subjects; as such, large groups are required to detect differences among groups. On the other hand, in our research, as the conditions were the same for both insertions, the results were more consistent [ 27 , 28 ]. In clinical trials, variables such as impedance modification, inner ear fluids, and the surgical effect of the applied cochlear approach will also affect the electrode placement and electrode discrimination [ 29 , 30 ].…”

“…Some of these studies did not achieve significantly different results in TIM conditions, and there was considerable variation among subjects; as such, large groups are required to detect differences among groups. On the other hand, in our research, as the conditions were the same for both insertions, the results were more consistent [ 27 , 28 ].…”

Detection of Tip Fold‐Over of the Slim Modiolar Electrode Using Intraoperative Mobile Cone‐Beam Computed Tomography

“…Several electrophysiological and imaging tests have been reported to be more effective for detecting electrodes with tip fold‐over. Transimpedance matrix (TIM) measurement 27,28 and spread of excitation (SOE) 21,27 are available using the telemetry functions of the electrodes. The specificities of TIM and SOE were 97.89% and 98.93%, respectively, and the sensitivity of the combination of these 2 modalities was 100% 27 .…”

“…Transimpedance matrix (TIM) measurement 27,28 and spread of excitation (SOE) 21,27 are available using the telemetry functions of the electrodes. The specificities of TIM and SOE were 97.89% and 98.93%, respectively, and the sensitivity of the combination of these 2 modalities was 100% 27 . However, clinical research software is necessary to perform these 2 tests, and their specificity is not 100% 27 .…”

“…27 However, clinical research software is necessary to perform these 2 tests, and their specificity is not 100%. 27 Since tip fold-over requires surgical treatment, false-positive cases should be avoided. CT 7,9,10,12,20,21,29 and fluoroscopy 28 are considered as morphological and imaging evaluations of the tip fold-over of the electrodes.…”