Performance on tests of central auditory processing by individuals exposed to high-intensity blasts

Abstract

Abstract-Thirty-six blast-exposed patients and twenty-nine non-blast-exposed control subjects were tested on a battery of behavioral and electrophysiological tests that have been shown to be sensitive to central auditory processing deficits. Abnormal performance among the blast-exposed patients was assessed with reference to normative values established as the mean performance on each test by the control subjects plus or minus two standard deviations. Blast-exposed patients performed abnormally at rates significantly above that which would occur by chance on three of the behavioral tests of central auditory processing: the Gaps-In-Noise, Masking Level Difference, and Staggered Spondaic Words tests. The proportion of blast-exposed patients performing abnormally on a speech-in-noise test (Quick Speech-In-Noise) was also significantly above that expected by chance. These results suggest that, for some patients, blast exposure may lead to difficulties with hearing in complex auditory environments, even when peripheral hearing sensitivity is near normal limits.Key words: audiometric evaluation, auditory dysfunction, auditory processing disorder, blast, central auditory processing, evoked potential, hearing loss, rehabilitation, traumatic brain injury, Veterans. INTRODUCTION The recent conflicts in Afghanistan and

Implications of blast exposure for central auditory function: A review

“…The most pressing need is for corroboration and extension of the results of Gallun et al [60], in which the overall rate of abnormal performance for those subjects exposed to blasts was more than four times that of the controls without blast exposure. It is essential to determine the degree to which abnormal performance on central auditory tests in the laboratory and the clinic correlates with patient complaints and with difficulties in more naturalistic environments.…”

“…Each test has been used in the general population in the diagnosis of central auditory dysfunction and has been shown to discriminate between participants with brain injuries and control participants of similar age and peripheral hearing status without brain injury. Analyses by Gallun et al suggest that participants exposed to blasts were statistically more likely than were controls to perform abnormally on the Staggered Spondaic Words test, the Gaps-in-Noise test, and the Masking Level Difference test [60]. The groups did not differ reliably on the proportion of participants performing abnormally on the other two tests, suggesting that these results were not due to generalized difficulties with the attention or memory demands of psychoacoustical testing.…”

“…A study conducted at the Department of Veterans Affairs (VA) Rehabilitation Research and Development (RR&D) National Center for Rehabilitative Auditory Research and the (former) Walter Reed Army Medical Center provides an example of how a battery of tests can be used to examine central auditory system dysfunction [60]. Participants who had been exposed to blasts were compared with age-and hearing-loss matched control participants who had not been blast exposed.…”

“…This allows the primary sound to be heard and more likely to be understood at intensity levels lower than would be possible without the use of a remote microphone [67]. The findings of Gallun et al, that blast exposure is particularly likely to result in difficulties with competing speech (e.g., the Staggered Spondaic Words test), suggest that a remote microphone system may be particularly effective [60]. Although two recent articles exploring the use of remote-microphone technology in individuals with central auditory dysfunction suggest this may be the case, it still needs to be confirmed through clinical research [68][69].…”

“…To date, very few data sets exist that can be used to estimate the prevalence of CAPD in the OIF/OEF/OND Veteran population. The rate may be quite high, however, given the combination of high rates of blast exposure [73] and TBI [74] and the data of Gallun et al [60] and Turgeon et al [71], which suggest that abnormal central auditory processing abilities are potentially associated with even mild brain injury.…”