Intraoperative Impedance Gradient as a Physiological Indicator of Electrode-Neural Interface in Pediatric Cochlear Implantation

To investigate the spatial gradient of intraoperative impedance across the cochlear electrode array in pediatric cochlear implant recipients and assess its potential as a physiological indicator for the electrode-neural interface.

A prospective observational study involving 56 pediatric patients underwent cochlear implantation with Cochlear Nucleus devices. Intraoperative polarized impedance and electrically evoked compound action potential (ECAP) threshold were recorded across all 1232 electrodes using AutoNRT software. Eight electrodes with open- or short-circuit were excluded, leaving 1,224 for analysis. Impedance values were categorized by cochlear region (basal, middle, apical), and electrodes with elevated impedance (10–20 kΩ) were analyzed for regional distribution and clinical relevance. Data were analyzed for spatial patterns and correlation with the ECAP threshold profiles.

A consistent basal-to-apical increase in impedance was observed (7.7 ± 1.9, 9.2 ± 1.4, 10.8 ± 1.5 kΩ; p<0.001). Impedance and ECAP threshold were weakly correlated (ρ = –0.20, p<0.001; β = –1.26, p<0.001), with a positive association in the apical region (ρ = 0.12, p = 0.048). Electrodes with higher impedance (10–20 kΩ) were less likely to show elevated or absent TNRT (OR = 0.175, p = 0.02). The impedance gradient persisted across age groups and was significantly correlated with ECAP threshold patterns.

Intraoperative impedance monitoring reveals a strong and physiologically consistent gradient, with higher values in apical electrodes. This gradient reflects anatomical and tissue interface variations, which may offer a valuable physiological indicator for intraoperative electrode positioning and neural interface integrity.