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

Correlation between Speech Recognition Score and NRT-Map-Mismatch

Meeting Abstract

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  • corresponding author M. Stecker - HNO-Klink der Albert-Ludwigs-Univ. Freiburg
  • R. Laszig - HNO-Klink der Albert-Ludwigs-Univ. 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. Doc05omci034

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Veröffentlicht: 31. Mai 2005

© 2005 Stecker et al.
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Neural Response Telemetry (NRT) is an elegant method for fast evoked response recording in Cochlea Implant patients. NRT therefore offers the opportunity of objective threshold estimation for speech processor fitting in very young children. The disadvantage of NRT, however, is that only peripheral hearing is tested by NRT, and necessary speech processor map thresholds, that include central hearing functions too, cannot be determined directly. We investigated this threshold mis match and looked for possible reasons.

Materials and Methods

In 30 adult patients, using a Cochlear CI24-System, NRT was performed in addition to standard psycho acoustic map threshold determination and speech discrimination tests. Measurements were restricted to electrode 10 in the middle of the array. For speech testing Freiburger monosyllable words were used at 70 dB.


NRT thresholds and map thresholds prove to have large inter individual variability. Also the gap between map threshold and NRT threshold varies extremely. This gap reveals a clear correlation to monosyllable speech understanding score.


The found correlation between speech understanding score and map threshold estimation error of NRT supports the assumption, that neural signal processing causes the threshold discrepancy between NRT and speech processor map. Small gaps indicate poor speech performance, large gaps, on the other hand, allow us to predict a good performance for the patient after some time of wearing the speech processor. This is in contrast to our expectations before we started our study.