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Mechanisms in noise-induced permanent hearing loss: an evoked otoacoustic emission and auditory brainstem response study

Published online by Cambridge University Press:  29 June 2007

Zheng-Min Xu*
Affiliation:
Department of Otolaryngology, University Hospital Ghent, Ghent, Belgium.
Bart Vinck
Affiliation:
Department of Otolaryngology, University Hospital Ghent, Ghent, Belgium.
Eddy De Vel
Affiliation:
Department of Otolaryngology, University Hospital Ghent, Ghent, Belgium.
Paul van Cauwenberge
Affiliation:
Department of Otolaryngology, University Hospital Ghent, Ghent, Belgium.
*
Address for correspondence: Zheng-Min Xu, M.D., Ph.D., Department of Otolaryngology, University Hospital Ghent, De Pintelaan 185 B–9000 Ghent, Belgium.

Abstract

In this study 22 patients (44 ears) with noise-induced permanent hearing loss were audiologically evaluated using transient-evoked otoacoustic emissions (TEOAE) and auditory brain-stem response (ABR). Twenty-one normal subjects (42 ears) without exposure to occupational noise were used as controls. Based upon the hearing loss at 4, 3, 2 and 1 kHz on the pure-tone audiogram, they were classified into four groups. In group 1 (eight ears), emissions were present in all ears but their TEOAE-noise level and their reproducibility (percentage) proved to be weak. The auditory brain-stem response (ABR) indicated that the I/V amplitude ratio, the latency values of wave V and the I–V intervals fell within the normal range in all ears. In Group 2 (14 ears), 40 per cent had no emissions, whereas the remaining ears showed weak emissions. The ABR revealed that in all ears the I/V amplitude ratio became small while wave V peak latency as well as I–V intervals were within the normal range. In Group 3 (10 ears), emissions were absent in 50 per cent, while in the other ears the emissions were very weak. The ABR revealed that the I/V amplitude ratio, which could be calculated in the 60 per cent in which wave I was present, was smaller than in Group 2. Wave V latency as well as I–V intervals were within the normal range. In Group 4 (12 ears), none of the ears showed emissions. The ABR indicated that the I/V amplitude ratio was much smaller when wave I was present (27 per cent) as well as I–V interval values being within the normal range. Wave V absolute latency value (δV index) indicated a positive index in 17 per cent of this group (two ears) when wave I was absent. In the present study a dynamic process from cochlear outer hair cells to cochlear neurons was seen, correlating with an increasing hearing loss.

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Main Articles
Copyright
Copyright © JLO (1984) Limited 1998

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