When Can Stable AutoNRT Thresholds be Expected? A Clinical Implication When Fitting Young Children

Abstract

Objective measurements are important for programming cochlear implants in young children and other individuals who cannot participate in behavioral measurements. AutoNRT, the automatic method used to record responses from the auditory nerve in the Cochlear Ltd., implant system, is often used as a basis for estimating the threshold level and comfort level (C-level) for these patients. However, it has not been sufficiently established if AutoNRT measurements remain consistent over time.This study aimed to determine if/when AutoNRT thresholds stabilize.The study design was a longitudinal prospective study.AutoNRT thresholds were obtained from 52 young children and 80 adults. All subjects received the same implant (CI24RE Contour Advance).AutoNRT thresholds were measured on all intracochlear electrodes during the surgery and at the initial activation. During the following year, children were measured at 1, 3, 6, and 12 months, and adults were measured at 6 and 12 months. The results were analyzed based on mean values, correlation, and absolute mean differences.There were large variations for all electrodes between the intraoperative and postoperative AutoNRT thresholds of both children and adults. For children, the thresholds were considered to be stable from 1 month. The correlations obtained between the last two measurements, 6 and 12 months, for both children and adults were generally high for all electrodes.The present results demonstrate the importance of repeating the AutoNRT measurement postoperatively, at about 1 month after initial activation, to obtain reliable and stable thresholds for estimating the T- and C-level profiles.

Optimized SNR-based ECAP threshold determination is comparable to the judgement of human evaluators

“…The procedure was first performed separately for different CI users and for different stimulating electrodes, and then averaged across the individual CI users of the FLEX28 electrode array (i.e., the largest electrode population in this study). The analysis revealed that the 95% confidence intervals of the threshold estimates are maximally ± 1.24 nC wide (mean: 0.59; SD: 0.21), which makes the algorithm suitable also for discovering clinically relevant differences, e.g., in test-retest studies [26][27][28][29][30].…”