Residual Effects of Combat-Related Mild Traumatic Brain Injury

Abstract

Mild traumatic brain injury (mTBI) has gained considerable notoriety during the past decade of conflict in Afghanistan and Iraq. However, the relationship between combat-related mTBI and residual mTBI symptoms, post-traumatic stress disorder (PTSD) symptoms, and neurocognitive deficits remains unclear. The purpose of the study was to compare residual mTBI and PTSD symptoms, and neurocognitive deficits among U.S. Army Special Operations Command (USASOC) personnel with diagnosed blunt, blast, and blast-blunt combination mTBIs. This study involved a retrospective medical records review of 27,169 USASOC personnel who completed a military version of the Immediate Post-Concussion Assessment Cognitive Test (ImPACT), Post-Concussion Symptom Scale (PCSS), and PTSD Checklist (PCL) between November 2009 and December 2011. Of the 22,203 personnel who met criteria for the study, 2,813 (12.7%) had a diagnosis of at least one mTBI. A total of 28% (n=410) of USASOC personnel with a history of diagnosed mTBI reported clinical levels of PTSD symptoms. Personnel with a history of diagnosed blunt (OR=3.58), blast (OR=4.23) or combination (OR=5.73) mTBI were at significantly (p=0.001) greater risk of reporting clinical levels of PTSD symptoms than those with no history of mTBI. A dose-response gradient for exposure to blast/combination mTBI on clinical levels of PTSD symptoms was also significant (p=0.001). Individuals with blast/combination mTBIs scored higher in residual mTBI (p=0.001) and PTSD symptoms (p=0.001), and performed worse on tests of visual memory (p=0.001), and reaction time (p=0.001) than those with blunt or no mTBI history. Individuals with combination mTBIs scored lower in verbal memory (p=0.02) than those with blunt mTBIs. Residual PTSD and mTBI symptoms appear to be more prevalent in personnel with blast mTBI. A dose-response gradient for blast mTBI and symptoms suggests that repeated exposures to these injuries may have lingering effects.

Diagnostic accuracy of Posttraumatic Stress Disorder Checklist in blast-exposed military personnel

“…Findings similar to ours have been reported in several investigations [32][33][34], while others have shown the opposite, that historical blast-related mTBI is associated with both PCS and PTSD symptom severity [15,35]. Differences in methodology among these studies, including differing operational definitions of mTBI, make the conflicting evidence difficult to reconcile.…”

“…While PTSD symptoms are reported to occur acutely in up to 40 percent of U.S. military personnel following an mTBI [13] and persistently in 42 percent of recent OIF/OEF Veterans with a history of mTBI [14], the actual PTSD risk and prevalence among those who sustained mTBI during OIF/OEF/OND is unknown because these and other investigations have determined PTSD status from PCL cut points that were derived from much different samples of combat Veterans, notably without high mTBI prevalence. For example, Kontos et al reported that military personnel with a selfreported blast-related mTBI diagnosis were at risk (odds ratio 4.2 vs no mTBI diagnosis) for reporting "clinical levels" of PTSD symptoms, but this was defined as a cut point 28 on the PCL, which was not crossvalidated for clinical PTSD [15].…”

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

“…These results indicate that a dose effect of blast exposures may exist in terms of neurobehavioral symptom reporting. A recent study by Kontos and associates 17 found a similarly graded pattern of postconcussion symptom endorsement after cumulative blast-related MTBIs with those experiencing more MTBIs endorsing more postconcussion symptoms. While they report on multiple blast-related MTBIs and the present study explored single episodes of MTBI with or without accompanying previous blast exposures, a similar pattern of increased symptom reporting is evident across our two studies.…”

“…These three clusters are labeled reexperiencing (items 1-5), avoidance or numbing (items 6-12) and hyperarousal (items [13][14][15][16][17]. This self-reported measure requires the subject to rate how much he/she has been bothered by that symptom in the past month, using a 1 (not at all) to 5 (extremely) Likert-scale value.…”

Effects of Blast Exposure on Subjective and Objective Sleep Measures in Combat Veterans with and without PTSD

“…6,7 While mTBI sustained from blast injuries are not the only means of sustaining mTBI (i.e., blunt trauma), blast injuries represent the most common type of mTBI reported in returning military personnel. 3,8 Of those exposed to blasts, the reported prevalence rates of subsequent mTBI in warfighters vary between 4.9% to 22%. 6,7,9,10 The projected 2-year costs associated with chronic mTBI, which refers to symptoms and impairments that last more than three months post-injury, could average as much as $591 billion.…”