Blast exposure in the military and its effects on sensory and cognitive auditory processing
Bressler, Scott Clarke
MetadataShow full item record
Blast-induced traumatic brain injury and hearing loss are two of the most common forms of the “invisible wounds of war” resulting from the United States’ Global War on Terror. Several published studies have been confirming recent reports from VA healthcare centers of blast-exposed Service Members complaining of auditory problems despite having hearing that is, for all intents and purposes, normal. Most common among these complaints is problems understanding speech in crowded and noisy situations. We hypothesized that problems with speech comprehension could either be the result of 1) damage to sensory areas in the auditory periphery or 2) blast-induced traumatic brain injury (TBI) to cortical networks associated with the processing of attention, memory, and other executive functions related to the processing of speech and linguistic information. In Chapter 1 of this thesis, we found that in a population of blast-exposed Veteran Service Members, problems with speech comprehension in noise were due to cognitive deficits likely resulting from issues related to their post-traumatic stress disorder (PTSD) diagnoses. Chapter 2 takes and expanded look at the topics of Chapter 1 with a more comprehensive battery of audiological, electrophysiological, and neuropsychological tests in active duty Service Members with and without a history of blast exposure. Unlike in veterans with PTSD, we found subclinical levels of peripheral auditory dysfunction, as well as evidence of compromised neural processing speed in the blast-exposed group. These deficits were also consistent with poorer performance on a standardized speech-in-noise test and lower self-reported ratings on an abbreviated version of the Speech, Spatial, and Qualities (SSQ) of Hearing questionnaire (Gatehouse and Noble, 2004). In Chapter 3,we modeled outcomes from the SSQ survey using objective measures of hearing function related to audibility, distortion of the neural representation of sound, attention, age, and blast status. We found for all subjects age and high frequency hearing thresholds predicted survey outcomes related to everyday listening ability. Within non-blast controls, however, measures of attention could differentiate between good and exceptional listening ability. Results from blast exposed subjects remained inconclusive. Collectively, these findings highlight the need for audiologists to take into account more than audiometric measures alone when diagnosing and treating hearing dysfunction in this unique and specialized patient population.