Evaluation of Transimpedance Matrix Measurement (TIM) heatmap for the assessment of cochlear implant electrode...

Introduction: It is estimated that 20% of pediatric patients eligible for implantation have various forms of Inner Ear Malformations (IEM). Transimpedance Matrix Measurement (TIM) is a relatively novel electrophysiological measurement protocol of the impedance patterns of electrode contacts within the cochlea. Aim: Presentation of TIM measurements, in the form of a heatmap, in patients with IEM. Materials and methods: Among 112 implantations performed between 2018 and 2024 in the pediatric group, 23 patients were diagnosed with IEM (20.5%). TIM and Stenver's plain X-ray were performed for all patients. Results: In 19 patients, standard approach with mastoidectomy and posterior tympanotomy was performed, in 2 cases retrofacial approach, in 2 petrosectomy with blind sac procedure, and in 2 "banana technique". In most patients, electrode Contour Advance (CA) was used. One case of tip fold-over showed a characteristic cross pattern. For all other IEM there were normal diagonals but voltage distribution showed abnormal distribution within the cochlea. Discussion: Most patients received a CA electrode because of its greater rigidity and the possibility of inhibiting CSF leakage by applying a piece of connective tissue for sealing to the electrode. Heatmaps for different IEM types differ from each other, but it is still possible to recognize TFO. The voltage spread in the cochlea in IEM shows different patterns for particular types of anomalies. Conclusions: TIM measurement as a heatmap seems to be a quick and reliable method for detecting electrode array tip fold-over intraoperatively for patients with inner ear malformations. Our study complements the knowledge about the use of research based on TIM heatmap.