A Multisite Study of the Relationships between Blast Exposures and Symptom Reporting in a Post-Deployment Active Duty Military Population with Mild Traumatic Brain Injury

Abstract

Explosive devices have been the most frequent cause of traumatic brain injury (TBI) among deployed contemporary U.S. service members. The purpose of this study was to examine the influence of previous cumulative blast exposures (that did or did not result in TBI) on later post-concussion and post-traumatic symptom reporting after sustaining a mild TBI (MTBI). Participants were 573 service members who sustained MTBI divided into four groups by number of blast exposures (1, 2, 3, and 4-10) and a nonblast control group. Post-concussion symptoms were measured using the Neurobehavioral Symptom Inventory (NSI) and post-traumatic stress disorder (PTSD) symptoms using the Post-traumatic Checklist-Civilian version (PCL-C). Results show groups significantly differed on total NSI scores ( p < 0.001), where symptom endorsement increased as number of reported blast exposures increased. Total NSI scores were significantly higher for the 3-and 4-10 blast groups compared with the 1-and 2-blast groups with effect sizes ranging from small to moderate (d = 0.31 to 0.63). After controlling for PTSD symptoms using the PCL-C total score, NSI total score differences remained between the 4-10-blast group and the 1-and 2-blast groups, but were less pronounced (d = 0.35 and d = 0.24, respectively). Analyses of NSI subscale scores using PCL-C scores as a covariate revealed significant between-blast group differences on cognitive, sensory, and somatic, but not affective symptoms. Regression analyses revealed that cumulative blast exposures accounted for a small but significant amount of the variance in total NSI scores (4.8%; p = 0.009) and total PCL-C scores (2.3%; p < 0.001). Among service members exposed to blast, post-concussion symptom reporting increased as a function of cumulative blast exposures. Future research will need to determine the relationship between cumulative blast exposures, symptom reporting, and neuropathological changes.

Discriminating military and civilian traumatic brain injuries

“…Even so, blast exposure is not a trivial piece of information. Recent evidence suggests that repeated blast exposure might have a cumulative effect on post-concussion symptom endorsement in service members who sustain TBI (Kontos et al, 2013;Reid et al, 2014), making the relative number of blasts experienced by a service member a potentially useful clinical, if not prognostic, piece of information.…”

Neuronal Injury and Glial Changes Are Hallmarks of Open Field Blast Exposure in Swine Frontal Lobe

“…For example, the history of blast related mTBI has been significantly associated with post-traumatic stress disorder (PTSD) and other physical problems in veterans from OIF [4] as well as those from OEF and Operation New Dawn [5,6]. In addition, the number of exposures also appears to be contributing to the neuropsychological sequelae with increased symptom reporting, as revealed by significant Neurobehavioral Symptom Inventory (NSI) scores in veterans with increased blast exposures [7]. There were also reports of abnormal hormonal levels in one or more pituitary axes [8] in those affected by blast mTBI.…”

Early Clinical Predictors of 5-Year Outcome After Concussive Blast Traumatic Brain Injury

“…13,14 Previous studies 15–18 have been based largely on self-report and screening tools to define TBI, rather than direct clinical assessments in cohorts identified at the time of injury and prospectively studied. Although much effort has been expended to better understand this type of concussive TBI, many studies in active-duty US military and veterans 16,19–26 have been restricted to cross-sectional evaluations, often involving retrospective medical record review 19–21 or self-report 16,18,22–24,26,27 and considering only later stages of injury. 25,28 …”