gms | German Medical Science

Fourth International Symposium and Workshops: Objective Measures in Cochlear Implants

Medical University of Hannover

01.06. bis 04.06.2005, Hannover

Objective Measurements with Nucleus System 4

Meeting Abstract

  • corresponding author T. Wesarg - Universitätsklinikum Freiburg
  • M. Stecker - Universitätsklinikum Freiburg
  • A. Aschendorff - Universitätsklinikum Freiburg
  • T. Klenzner - Universitätsklinikum Freiburg
  • R. Laszig - Universitätsklinikum Freiburg

Medical University of Hannover, Department of Otolaryngology. Fourth International Symposium and Workshops: Objective Measures in Cochlear Implants. Hannover, 01.-04.06.2005. Düsseldorf, Köln: German Medical Science; 2005. Doc05omci015

The electronic version of this article is the complete one and can be found online at: http://www.egms.de/en/meetings/omci2005/05omci015.shtml

Published: May 31, 2005

© 2005 Wesarg et al.
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Outline

Text

Introduction

The Nucleus System 4 contains an improved Neural Response Telemetry (NRT) system enabling the measurement of the Electrically evoked Compound Action Potential (ECAP). As the Nucleus System 3 it allows for the manual control of the ECAP measurement procedure (Conventional NRT). Additionally, the Nucleus 4 System includes an automated algorithm to determine ECAP thresholds (Auto-NRT). One objective of this study was to assess the usability of the Auto-NRT of the Nucleus System 4 for ECAP threshold determination. Another objective was the investigation of the relation between Auto-NRT thresholds and behavioural thresholds as well as between visually detected Electrically evoked Stapedius Reflex (ESR) thresholds and behavioural thresholds.

Materials and Methods

To date 6 postlingually deafened adults implanted with the Nucleus System 4 implant CI24RE(CA) participated in the study. Intraoperative ESRT measurements were performed in all patients and intraoperative Auto-NRT was applied with a stimulation rate of 80 Hz in 4 and with a stimulation rate of 250 Hz in 5 of the 6 patients at 5 different electrodes (1, 6, 11, 16, 22). During first fitting the patients were programmed with different strategies whereas they received the same strategies one month after first fitting. Therefore only the correlation between intraoperative Auto-NRT and ESR thresholds and the behavioural thresholds obtained one month after first fitting were assessed for 3 of the 5 electrodes (1, 11 and 22) as at these electrodes behavioural thresholds were obtained directly without interpolation.

Results

ESR thresholds were detected in 4 patients at all 5 electrodes and in 1 patient at 4 electrodes. In case of Auto-NRT with 80 Hz the automated algorithm could determine ECAP thresholds in 3 patients at all 5 electrodes and in 1 patient at 4 electrodes while in case of Auto-NRT with 250 Hz ECAP thresholds could be determined in 4 patients at all 5 electrodes and in 1 patient at 3 electrodes. The correlation between the ESR thresholds and the behavioural thresholds was 0.96 for electrode 1, 0.55 for electrode 11 and 0.72 for electrode 22. Between 80 Hz Auto-NRT thresholds and behavioural thresholds the correlation was 0.62 for electrode 1, 0.80 for electrode 11 and 0.77 for electrode 22, while between 250 Hz Auto-NRT thresholds and behavioural thresholds a correlation of 0.81 for electrode 1, 0.74 for electrode 11 and 0.80 for electrode 22 was found.

Conclusions

The preliminary results demonstrate a good usability of the Nucleus System 4 Auto-NRT tool for ECAP threshold determination shortening the recording and analysis time compared to Conventional NRT measurements. The medium to high correlation between Auto-NRT and behavioural thresholds is promising. The relation between these thresholds should be investigated in more patients at different intervals and additional electrodes to assess the usability of Auto-NRT thresholds for the prediction of behavioural thresholds in patients with the Nucleus System 4 cochlear implant.