Comparison Between Transimpedance Matrix (TIM) Measurement and X-ray Fluoroscopy for Intraoperative Electrode Array Tip Fold-Over Detection.

Objective: The aim of this study was to compare Transimpedance Matrix (TIM-) measurement and X-ray fluoroscopy for the intraoperative detection of electrode array tip fold-over in cochlear implant recipients.

Study Design: Retrospective agreement study.

Setting: Tertiary referral hospital.

Patients: Forty-two patients (47 ears) consecutively implanted with the Slim Modiolar Electrode.

Interventions: Five raters, with different levels of clinical experience, individually retrospectively evaluated the TIM-heatmaps and X-ray fluoroscopy images of all patients included in this study for electrode array tip fold-over.

Main Outcome Measures: Agreement between raters' individual evaluation and the diagnosis given during clinical intraoperative evaluation for both modalities, as well as the inter-method agreement between TIM-measurement and fluoroscopy, and the inter-rater agreement for both modalities.

Results: A tip fold-over was found in three of the forty-seven implantations (6.4%) included in this study. The average agreement between raters' evaluation and the intraoperative evaluation was 88% (Cohens κ = 0.378) for fluoroscopy and 99% (Cohens κ = 0.915) for TIM-measurement. Two raters misdiagnosed at least one tip fold-over as being correctly positioned when evaluating the fluoroscopy images (1/3 and 3/3, respectively). Each of the raters correctly detected all three tip fold-overs using the TIM-heatmaps. The inter-rater agreement for fluoroscopy was classified as "fair" (Fleiss' κ = 0.286), while the inter-rater agreement for TIM-measurement was classified as "near-perfect" (Fleiss' κ = 0.850).

Conclusions: TIM-measurement has a high potential to replace X-ray fluoroscopy for intraoperatively detecting electrode array tip fold-over in cochlear implantation, especially in patients implanted with flexible, precurved arrays.