Title page for ETD etd-02222010-133535

Document Type Master's Dissertation
Author Biagio, Leigh
Email leigh.biagio@soundtalk.co.za
URN etd-02222010-133535
Document Title Slow cortical auditory evoked potentials and auditory steady-state evoked responses in adults exposed to occupational noise
Degree MCommunication Pathology
Department Communication Pathology
Advisor Name Title
Dr M Soer Co-Supervisor
Prof D C D Swanepoel Supervisor
  • nonorganic hearing loss
  • ASSR
  • stimulus and recording parameters
  • clinical efficiency
  • clinical effectiveness
  • auditory evoked potentials
  • slow cortical auditory evoked potentials
  • auditory steady state responses
  • occupational noise induced hearing loss
Date 2009-09-01
Availability unrestricted

In individuals claiming compensation for occupational noise induced hearing loss, a population with a high incidence of nonorganic hearing loss, a reliable and valid behavioural pure tone (PT) threshold is not always achievable. Recent studies have compared the accuracy of behavioural PT threshold estimation using the slow cortical auditory evoked potentials (SCAEP) and auditory steady-state responses (ASSR) but there is no consensus regarding recommended technique. A review of the literature indicated that no comparison has been completed on the use of SCAEP and a single frequency ASSR technique.

A research project was therefore initiated with the aim of comparing the clinical effectiveness (accuracy) and clinical efficiency (time required) of SCAEP and ASSR for behavioural PT threshold estimation in adults exposed to occupational noise. Adult participants were divided into a group with normal hearing (behavioural PT thresholds < 20 dBHL; n = 15) and a group of participants with hearing loss (n = 16 adults), the latter of which were recruited from individuals referred for audiometric screening, as part of hearing conservation programs, and who were, therefore, exposed to occupational noise. The GSI Audera electrophysiological system was used for both SCAEP and ASSR threshold measurement at 0.5, 1, 2 and 4 kHz. Use was made of tone burst stimuli for the SCAEP (rise and fall of 10 ms with 80 ms plateau), while amplitude and frequency modulated (AM/FM) stimuli was used during ASSR testing. The systemís 40 Hz protocol was chosen for use during ASSR recording while participants slept because this led to lparticipants. ASSR thresholds could not be measured in two of the three sleeping participants in the preliminary study using an 80 Hz modulation rate due to excessive noise.

The mean SCAEP difference scores (SCAEP threshold minus behavioural PT threshold) for both participant groups were -0.2+10.2, 2.8+10.1,5.8+9.7, 0.5+10.4 at 0.5, 1, 2, and 4 kHz respectively, while ASSR difference scores were 25.3+12.8, 21.7+11.3,32.3+12.2, 27.1+13.8. The SCAEP correlations with behavioural PT thresholds across frequencies (r = 0.85) were also stronger than ASSR correlations (r = 0.75). Therefore, with regard to proximity of auditory evoked potentials (AEP) to behavioural PT thresholds and consistency of this relationship, the SCAEP, rather than ASSR, is the AEP of choice. However, the SCAEP took on average 10.1 minutes longer to complete than the ASSR. Clinical effectiveness was given comparably more weight than the clinical efficiency of the AEP technique to estimate behavioural PT thresholds due to the impact on overcompensation for occupational noise induced hearing loss. As such, the study acknowledged the SCAEP as the AEP of choice for the purpose of behavioural PT thresholds in adults exposed to occupational noise.

It is important to note that the conclusion reached in the current study arose from the comparison of the SCAEP with a specific ASSR technique. Accuracy of ASSR estimation of behavioural PT thresholds is strongly influenced by stimulus and recording parameters of the system used, and by the participant variables.

Copyright © 2009, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Please cite as follows:

Biagio, L 2009, Slow cortical auditory evoked potentials and auditory steady-state evoked responses in adults exposed to occupational noise, MCommunication Pathology dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-02222010-133535/ >

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