Effect of the vertical facial canal to round window distance concerning neural response telemetry during cochlear implantation in children.

Abstract

To assess the correlation of the distance from the round window (RW) to the vertical facial canal (VFC) with neural response telemetry thresholds (T-NRT), which may have an influence on the insertion trajectory and aid in preoperative surgical planning and electrode selection. An observational study was conducted on 30 prelingually deaf children under five years diagnosed with bilateral severe to profound hearing loss and received a cochlear implant. The preoperative high resolution computed tomography (HRCT) images in the axial cut bone window setting at the round window level was used to calculate the distance from the RW to the VFC on the RadiAnt DICOM Viewer. The intraoperative distance was measured with ScopyDoc version 8.2.4 software. In Auto-NRT mode, software-based recordings (Cochlear's Custom Sound EP 6.0) were used to measure and evaluate the T-NRT current level. A statistically significant positive correlation of the RW to VFC distance with the average T-NRT p=0.02, r=-0.4 and with the mid-frequency, T-NRT p=0.003, r=-0.5 was found. The insertion trajectory can be ascertained by a statistically significant correlation between average T-NRT and mid-frequency T-NRT with RW and VFC distance, and this reliable factor can be taken into account in future surgical technique modulation, electrode selection, and electrode design.