Central Auditory Processing Deficits Associated With Blast Exposure
Condition: Blast Injuries; Brain Injuries; Age Factors
MeSH terms: Brain Injuries; Wounds and Injuries; Blast Injuries
Study type: Observational [Patient Registry]

Summary: 
      The current conflicts in Afghanistan and Iraq have resulted in unprecedented rates of
      exposure to high-intensity blasts and resulting brain injury. This research team has
      established that recently blast-exposed Soldiers show differences from controls on tests of
      central auditory function. This project will 1) develop a more accurate estimate of the
      prevalence of central auditory dysfunction among Veterans exposed to blasts over the past ten
      years, 2) identify the functional outcomes associated with abnormal performance on tests of
      central processing, and 3) improve understanding of the ways in which blast-exposure
      resembles and differs from both the normal aging process and non-blast-related TBI in terms
      of performance on tests of central auditory processing.
    

Detailed description: 
      The current conflicts in Afghanistan (Operation Enduring Freedom; OEF) and Iraq (Operation
      Iraqi Freedom; OIF) have resulted in unprecedented rates of exposure to high-intensity blasts
      and resulting brain injury. Dennis (2009) reports that during 2005-2007, 68% of U.S. military
      personnel injured in the OEF/OIF conflicts had blast-related injuries and 28%-31% of those
      evacuated to Walter Reed Army Medical Center (WRAMC), Washington, DC had brain injuries.
      While the common focus of auditory evaluation is on damage to the peripheral auditory system,
      the prevalence of brain injury among those exposed to high-intensity blasts suggests that
      damage to the central auditory system is an equally important concern for the blast-exposed
      Veteran. Discussions with clinical audiologists and OEF/OIF Veterans Service Office personnel
      suggest that a common complaint voiced by blast-exposed Veterans is an inability to
      understand speech in noisy environments, even when peripheral hearing is within normal or
      near-normal limits (see attached letters of support). Such complaints are consistent with
      damage to neural networks responsible for higher-order auditory processing. This proposal is
      the second phase of a research project focused on examining the degree to which central
      auditory processing (CAP) dysfunction is a result of blast exposure. Over the initial period
      of funding, data collection at WRAMC and the VA RR&D National Center for Rehabilitative
      Auditory Research (NCRAR) established that CAP dysfunction is present in Warfighters exposed
      to high-intensity blasts while serving in combat. Recently blast-exposed patients with and
      without diagnoses of mild traumatic brain injury (mTBI) tested at WRAMC showed differences
      from controls tested at NCRAR on one or more behavioral and neurophysiological tests used to
      evaluate central auditory function. This project will 1) develop a more accurate estimate of
      the prevalence of central auditory dysfunction among Veterans exposed to blasts over the past
      ten years, 2) identify the functional outcomes associated with abnormal performance on tests
      of central processing, and 3) improve understanding of the ways in which blast-exposure
      resembles and differs from both the normal aging process and non-blast-related TBI in terms
      of performance on tests of central auditory processing.

      Key Question 1: To what extent is CAP dysfunction observable among OEF/OIF Veterans who have
      been exposed to high intensity blasts? Based on preliminary data, the investigators
      hypothesize that the rate of abnormal performance on behavioral and neurophysiological tests
      of CAP dysfunction will be higher in a group of Veterans exposed to blasts than it will be in
      a control group of similar ages and hearing thresholds who have not been exposed to blasts.

      Key Question 2: How well can behavioral and neurophysiological tests of CAP predict
      functional auditory deficits measured behaviorally and through self report? It is
      hypothesized that tests of CAP ability will predict performance in a testing situation
      involving multiple talkers delivering competing messages. CAP tests will also correlate with
      responses blast-exposed Veterans make on the Speech and Spatial Qualities of Hearing (SSQ)
      questionnaire, designed to examine functional hearing ability in various acoustically complex
      environments.

      Key Question 3: To what extent do blast-exposed Veterans resemble older listeners and
      participants with mild TBI who have not been exposed to blasts in their performance on CAP
      tests and functional tests of hearing? It is hypothesized that comparisons of the
      blast-exposed group with an older group with matched pure-tone sensitivity and an age- and
      hearing-matched group with non-blast-related TBI will be consistent with premature aging in
      the blast-exposed group but demonstrate substantive differences with the non-blast group.
    

Intervention name(s): Diagnostic
Intervention type(s): Other
Intervention description(s): All participants will be evaluated with a battery of behavioral and electrophysiological measures to assess central auditory processing abilities.
Observational model: Case-Control
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        community sample
      
Biospecimen description: 
      None collected.
    
Keywords: Central Auditory Processing; Traumatic Brain Injury; Hearing Loss