Outcome Trends after US Military Concussive Traumatic Brain Injury

Gender Disparities in Neurobehavioral Symptoms and the Role of Post-Traumatic Symptoms in US Service Members Following Mild Traumatic Brain Injury

Women are more directly involved in combat operations today than ever before, currently making up 18.6% of officers and 16.8% of enlisted personnel in the United States military. However, women continue to be under-represented in military research. Studies that do consider gender differences in traumatic brain injury (TBI) outcomes have shown that women report significantly more post-concussive symptoms than men. Conclusions for true gender differences related to TBI are hard to make without controlling for non-TBI factors. The effects previously identified in the literature may be an artifact of how men and women differ in their response to injury, unrelated to the neurological recovery process associated with TBI. The objective of this study was to examine the effects of gender specifics on mild TBI (mTBI) sequelae on injured and uninjured control groups, and to investigate the role of post-traumatic stress disorder (PTSD) on symptom reporting. It should be noted that the terms "gender" and "men/women" are used in this article in place of "sex" or "males/females" given that we are not discussing biological attributes. A total of 966 United States military service members and veterans were included in the study. Of the total sample, 455 men and 46 women were in the mTBI group, 285 men and 31 women were in the injured controls group (IC), and 111 men and 38 women in the non-injured controls group (NIC). Post-concussive and quality of life symptoms were compared for men and women while controlling for combat exposure. MTBI and IC groups were also stratified by PTSD presentation. Measures used included the Neurobehavioral Symptom Inventory (NSI), PTSD Checklist (PCL-C), Traumatic Brain Injury Quality of Life (TBI-QOL), and Combat Exposure Scale. In the mTBI group, women had worse scores on NSI total, NSI Somatosensory and Affective clusters, and the TBI-QOL Anxiety, Fatigue, and Headache scales (n2 = 0.018-0.032, small to small-medium effect sizes). When PTSD was present, women had worse scores on the NSI Somatosensory cluster only (n2 = 0.029, small-medium effect size). In contrast, when PTSD was absent, women had worse scores than men on the NSI Somatosensory and Affective clusters, and the TBI-QOL Anxiety and Headache scales (n2 = 0.032-0.063, small to medium effect sizes). In the IC group, women had worse scores on the NSI Cognitive cluster and the TBI-QOL Fatigue and Pain Interference scales (n2 = 0.024-0.042, small to small-medium effect sizes). However, group differences were no longer found when stratified by PTSD sub-groups. In the NIC group, there were no significant group differences for any analyses. We were able to identify symptoms unique to women recovering from mTBI that were not present following other forms of physical injury or in healthy controls. However, the impact of PTSD exacerbates the symptom profile and its comorbidity with mTBI equates to most of the noted gender differences.

Risk of Traumatic Brain Injury in Deployment and Nondeployment Settings Among Members of the Millennium Cohort Study

OBJECTIVE

To describe and quantify the prevalence and risk of deployment and nondeployment service-related traumatic brain injury (TBI) among participants of the Millennium Cohort Study.

SETTING

Survey data.

PARTICIPANTS

28 759 Millennium Cohort Study participants who were active duty, Reserves, or National Guard at the time of the survey.

DESIGN

Cross-sectional secondary data analysis.

MAIN MEASURES

Estimates of prevalence and rates of TBI were calculated. Multivariable Poisson regression estimated rate ratios of TBI overall and stratified by deployment and nondeployment settings.

RESULTS

The rate of TBI over the 362 535 person-years (PY) was 2.95 p/100 PY. the nondeployment rate was 2.15 p/100 PY, with a significantly higher rate (11.38 p/100 PY) in deployment settings. Bullets/blasts were the most common TBI mechanisms in deployed settings, while sports/physical training and military training were common in nondeployed settings.

CONCLUSIONS

The risk of TBI as well as its mechanism varies by deployment and nondeployment, suggesting that targeted prevention strategies are needed to reduce the risk for TBI among military personnel based on their deployment status.

Transcriptomic dynamics governing serotonergic dysregulation in the dorsal raphe nucleus following mild traumatic brain injury

Mild traumatic brain injury (mTBI) is a leading cause of disability in the United States, with neuropsychiatric disturbances such as depression, anxiety, PTSD, and social disturbances being common comorbidities following injury. The molecular mechanisms driving neuropsychiatric complications following neurotrauma are not well understood and current FDA-approved pharmacotherapies employed to ameliorate these comorbidities lack desired efficacy. Concerted efforts to understand the molecular mechanisms of and identify novel drug candidates for treating neurotrauma-elicited neuropsychiatric sequelae are clearly needed. Serotonin (5-HT) is linked to the etiology of neuropsychiatric disorders, however our understanding of how various forms of TBI directly affect 5-HT neurotransmission is limited. 5-HT neurons originate in the raphe nucleus (RN) of the midbrain and project throughout the brain to regulate diverse behavioral phenotypes. We hypothesize that the characterization of the dynamics governing 5-HT neurotransmission after injury will drive the discovery of novel drug targets and lead to a greater understanding of the mechanisms associated with neuropsychiatric disturbances following mild TBI (mTBI). Herein, we provide evidence that closed-head mTBI alters total DRN 5-HT levels, with RNA sequencing of the DRN revealing injury-derived alterations in transcripts required for the development, identity, and functional stability of 5-HT neurons. Further, using gene ontology analyses combined with immunohistological analyses, we have identified a novel mechanism of transcriptomic control within 5-HT neurons that may directly influence 5-HT neuron identity/function post-injury. These studies provide molecular evidence of injury-elicited 5-HT neuron dysregulation, data which may expedite the identification of novel therapeutic targets to attenuate TBI-elicited neuropsychiatric sequelae.

Exploring Interactions Between Traumatic Brain Injury History and Gender on Medical Comorbidities in Military Veterans: An Epidemiological Analysis in the VA Million Veteran Program

Epidemiological studies of medical comorbidities and possible gender differences associated with traumatic brain injury (TBI) are limited, especially among military veterans. The purpose of this study was to examine relationships between TBI history and a wide range of medical conditions in a large, national sample of veterans, and to explore interactions with gender. Participants of this cross-sectional epidemiological study included 491,604 veterans (9.9% TBI cases; 8.3% women) who enrolled in the VA Million Veteran Program (MVP). Outcomes of interest were medical comorbidities (i.e., neurological, mental health, circulatory, and other medical conditions) assessed using the MVP Baseline Survey, a self-report questionnaire. Logistic regression models adjusting for age and gender showed that veterans with TBI history consistently had significantly higher rates of medical comorbidities than controls, with the greatest differences observed across mental health (odds ratios [ORs] = 2.10-3.61) and neurological (ORs = 1.57-6.08) conditions. Similar patterns were found when evaluating men and women separately. Additionally, significant TBI-by-gender interactions were observed, particularly for mental health and neurological comorbidities, such that men with a history of TBI had greater odds of having several of these conditions than women with a history of TBI. These findings highlight the array of medical comorbidities experienced by veterans with a history of TBI, and illustrate that clinical outcomes differ for men and women with TBI history. Although these results are clinically informative, more research is needed to better understand the role of gender on health conditions in the context of TBI and how gender interacts with other social and cultural factors to influence clinical trajectories following TBI. Ultimately, understanding the biological, psychological, and social mechanisms underlying these comorbidities may help with tailoring TBI treatment by gender and improve quality of life for veterans with TBI history.

Combat Deployed Service Members by Blast TBI and Service Separation Status 5-years Post-deployment: Comparison of Cognitive, Neurobehavioral, and Psychological Profiles of Those Who Left vs. Those Still Serving

INTRODUCTION

Longitudinal research regarding the pre- and post-separation experience has been relatively limited, despite its potential as a major life transition. Separating from the military and re-integration to civilian life is noted to be a period of increased risk of significant adjustment challenges, which impacts a service member in a multitude of areas. Active duty service members with combat-related physical or mental health or pre-existing adjustment conditions may be more likely to separate from service and more at risk for post-military service adjustment problems.

MATERIALS AND METHODS

This is a secondary data analysis from a prospective, observational, longitudinal, multicohort study involving deployed service members originally enrolled between 2008 and 2013 in combat or following medical evacuation to Landstuhl, Germany. Two combat-deployed cohorts were examined: non-head-injured control without blast exposure (n = 109) and combat-related concussion arising from blast (n = 165). Comprehensive clinical evaluations performed at 1 year and 5 year follow-up included identical assessment batteries for neurobehavioral, psychiatric, and cognitive outcomes. In addition to demographics collected at each study visit, the current analysis leveraged the Glasgow Outcome Scale Extended (GOS-E), a measure of overall global disability. For neurobehavioral impairment, the Neurobehavioral Rating Scale-Revised (NRS) was used as well as the Headache Impact Test (HIT-6) to assess headache burden. To compare psychiatric symptom burden between those separated to those still serving, the Clinician-Administered PTSD Scale for DSM-IV (CAPS) and Montgomery-Asberg Depression Rating Scale (MADRS) for depression were used as well as the Michigan Alcohol Screening Test (MAST) to be able to compare alcohol misuse across groups. Overall cognitive function/performance was defined for each service member by aggregating the 19 neuropsychological measures.

RESULTS

Overall comparisons following adjustment by linear regression and correction for multiple comparisons by separation status subgroup for non-blast control or blast traumatic brain injury (TBI) identified significant differences at 5 years post-enrollment in measures of global disability, neurobehavioral impairment, and psychiatric symptom burden. Those who separated had worse global disability, worse neurobehavioral symptoms, worse Post-Traumatic Stress Disorder symptoms, and worse depression symptoms than active duty service members. While service members who sustain a mild blast TBI during combat are more likely to separate from service within 5 years, there is a proportion of those non-injured who also leave during this time frame. Clinical profiles of both groups suggest service members who separated have elevated psychiatric and neurobehavioral symptoms but not cognitive dysfunction. Interestingly, the symptom load in these same domains is lower for those without blast TBI who separated during this time frame.

CONCLUSIONS

These results appear to support previous research depicting that, for some service members, transitioning out of the military and re-integrating into civilian life can be a challenging adjustment. Many factors, including personal and social circumstances, prior mental or emotional difficulties, availability of social or community support or resources, can influence the adjustment outcomes of veterans. Service members with prior adjustment difficulties and/or those with blast TBI history (and ongoing neurobehavioral symptoms) may find the transition from military to civilian life even more challenging, given the potential substantial changes in lifestyle, structure, identity, and support.

Mild traumatic brain injury, PTSD symptom severity, and behavioral dyscontrol: a LIMBIC-CENC study

Background

Behavioral dyscontrol occurs commonly in the general population and in United States service members and Veterans (SM/V). This condition merits special attention in SM/V, particularly in the aftermath of deployments. Military deployments frequently give rise to posttraumatic stress disorder (PTSD) and deployment-related mild TBI traumatic brain injury (TBI), potentially leading to manifestations of behavioral dyscontrol.

Objective

Examine associations among PTSD symptom severity, deployment-related mild traumatic brain injury, and behavioral dyscontrol among SM/V.

Design

Secondary cross-sectional data analysis from the Long-Term Impact of Military-Relevant Brain Injury Consortium - Chronic Effects of Neurotrauma Consortium prospective longitudinal study among SM/V (N = 1,808).

Methods

Univariable and multivariable linear regression models assessed the association and interaction effects between PTSD symptom severity, as assessed by the PTSD Checklist for the Diagnostic and Statistical Manual, 5th edition (PCL-5), and deployment-related mild TBI on behavioral dyscontrol, adjusting for demographics, pain, social support, resilience, and general self-efficacy.

Results

Among the 1,808 individuals in our sample, PTSD symptom severity (B = 0.23, 95% CI: 0.22, 0.25, p < 0.001) and deployment-related mild TBI (B = 3.27, 95% CI: 2.63, 3.90, p < 0.001) were significantly associated with behavioral dyscontrol in univariable analysis. Interaction effects were significant between PTSD symptom severity and deployment mild TBI (B = -0.03, 95% CI: -0.06, -0.01, p = 0.029) in multivariable analysis, indicating that the effect of mild TBI on behavioral dyscontrol is no longer significant among those with a PCL-5 score > 22.96.

Conclusion

Results indicated an association between PTSD symptom severity, deployment-related mild TBI, and behavioral dyscontrol among SM/V. Notably, the effect of deployment-related mild TBI was pronounced for individuals with lower PTSD symptom severity. Higher social support scores were associated with lower dyscontrol, emphasizing the potential for social support to be a protective factor. General self-efficacy was also associated with reduced behavioral dyscontrol.

mTBI evaluation, management, and referral to allied healthcare: practices of first-line healthcare professionals

PRIMARY OBJECTIVE

To gain an understanding of current evaluation practices, post-injury recommendations, and referrals to allied healthcare professions (AHP) by first-line healthcare professionals (FHPs) providing care for people with mild traumatic brain injury (mTBI).

RESEARCH DESIGN

Survey study.

METHODS AND PROCEDURES

Physicians, physician assistants, nurse practitioners, nurses, and athletic trainers (n = 126) completed an online survey, including Likert scale and free response question relating to mTBI evaluation, management, and referral practices.

MAIN OUTCOMES AND RESULTS

FHPs surveyed reported being confident in their ability to evaluate patients with suspected mTBI, relying most heavily on patient-reported symptoms and physical signs as methods of evaluation. Most FHPs reported making recommendations to compensate for the symptoms experienced following mTBI diagnosis. In contrast, FHPs expressed challenges in the evaluation and management of symptoms associated with mTBI along with limited knowledge of and referrals to AHPs.

CONCLUSIONS

Overall, FHPs feel confident in the diagnosis of mTBI but experience assessment and management challenges. AHPs are underutilized on mTBI management teams calling for a need for multidisciplinary collaboration on research, education, and rehabilitation efforts to optimally care for people experiencing mTBI symptoms.

Chronic frontal neurobehavioural symptoms in combat-deployed military personnel with and without a history of blast-related mild traumatic brain injury

OBJECTIVE

This study evaluated frontal behavioural symptoms, via the FrSBe self-report, in military personnel with and without a history of blast-related mild traumatic brain injury (mild TBI).

METHODS

Prospective observational cohort study of combat-deployed service members leveraging 1-year and 5-year demographic and follow up clinical outcome data.

RESULTS

The blast mild TBI group (n = 164) showed greater frontal behavioural symptoms, including clinically elevated apathy, disinhibition, and executive dysfunction, during a 5-year follow-up, compared to a group of combat-deployed controls (n = 107) without mild TBI history or history of blast exposure. We also explored changes inbehaviourall symptoms over a 4-year span, which showed clinically significant increases in disinhibition in the blast mild TBI group, whereas the control group did not show significant increases in symptoms over time.

CONCLUSION

Our findings add to the growing evidence that a proportion of individuals who sustain mild TBI experience persistent behavioural symptoms. We also offer a demonstration of a novel use of the FrSBe as a tool for longitudinal symptom monitoring in a military mild TBI population.

Characterization of neural mechanotransduction response in human traumatic brain injury organoid model

The ability to model physiological systems through 3D neural in-vitro systems may enable new treatments for various diseases while lowering the need for challenging animal and human testing. Creating such an environment, and even more impactful, one that mimics human brain tissue under mechanical stimulation, would be extremely useful to study a range of human-specific biological processes and conditions related to brain trauma. One approach is to use human cerebral organoids (hCOs) in-vitro models. hCOs recreate key cytoarchitectural features of the human brain, distinguishing themselves from more traditional 2D cultures and organ-on-a-chip models, as well as in-vivo animal models. Here, we propose a novel approach to emulate mild and moderate traumatic brain injury (TBI) using hCOs that undergo strain rates indicative of TBI. We subjected the hCOs to mild (2 s[Formula: see text]) and moderate (14 s[Formula: see text]) loading conditions, examined the mechanotransduction response, and investigated downstream genomic effects and regulatory pathways. The revealed pathways of note were cell death and metabolic and biosynthetic pathways implicating genes such as CARD9, ENO1, and FOXP3, respectively. Additionally, we show a steeper ascent in calcium signaling as we imposed higher loading conditions on the organoids. The elucidation of neural response to mechanical stimulation in reliable human cerebral organoid models gives insights into a better understanding of TBI in humans.

Serum-based Raman spectroscopic diagnosis of blast-induced brain injury in a rat model

The diagnosis of blast-induced traumatic brain injury (bTBI) is of paramount importance for early care and clinical therapy. Therefore, the rapid diagnosis of bTBI is vital to the treatment and prognosis in clinic. In this paper, we reported a new strategy for label-free bTBI diagnosis through serum-based Raman spectroscopy. The Raman spectral characteristics of serum in rat were investigated at 3 h, 24 h, 48 h and 72 h after mild and moderate bTBIs. It has been demonstrated that both the position and intensity of Raman characteristic peaks exhibited apparent differences in the range of 800-3000cm^-1 compared with control group. It could be inferred that the content, structure and interaction of biomolecules in the serum were changed after blast exposure, which might help to understand the neurological syndromes caused by bTBI. Furthermore, the control group, mild and moderate bTBIs at different times (a total of 9 groups) were automatically classified by combining principal component analysis and four machine learning algorithms (quadratic discriminant analysis, support vector machine, k-nearest neighbor, neural network). The highest classification accuracy, sensitivity and precision were up to 95.4%, 95.9% and 95.7%. It is suggested that this method has great potential for high-sensitive, rapid, and label-free diagnosis of bTBI.

Feasibility and acceptability of a brief intervention to improve mild traumatic brain injury recovery: Problem-solving training-concussion

OBJECTIVE

Mild traumatic brain injuries (mTBIs) are common among Veterans. Although the majority of neurobehavioral symptoms resolve following mTBI, studies with Veteran samples demonstrate a high frequency and chronicity of neurobehavioral complaints (e.g., difficulties with attention, frustration tolerance) often attributed to mTBI. Recent opinions suggest the primacy of mental health treatment, and existing mTBI practice guidelines promote patient-centered intervention beginning in primary care (PC). However, trial evidence regarding effective clinical management in PC is lacking. This study evaluated the feasibility and acceptability of a brief, PC-based problem-solving intervention to reduce psychological distress and neurobehavioral complaints.

RESEARCH METHOD/DESIGN

Mixed method open clinical trial of 12 combat Veterans with a history of mTBI, chronic neurobehavioral complaints, and psychological distress. Measures included qualitative and quantitative indicators of feasibility (recruitment and retention metrics, interview feedback), patient acceptability (treatment satisfaction, perceived effectiveness), and change in psychological distress as measured by the Brief Symptom Inventory-18.

RESULTS

The protocol was successfully delivered via in-person and telehealth treatment modalities (4.3 sessions attended on average; 58% completed the full protocol). Patient interview data suggested that treatment content was personally relevant, and patients were satisfied with their experience. Treatment completers described the intervention as helpful and reported corresponding reductions in psychological distress (ES = 1.8). Dropout was influenced by the onset of the COVID-19 pandemic.

CONCLUSIONS/IMPLICATIONS

Further study with a more diverse, randomized sample is warranted. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Altered lateralization of the cingulum in deployment-related traumatic brain injury: An ENIGMA military-relevant brain injury study

Traumatic brain injury (TBI) in military populations can cause disruptions in brain structure and function, along with cognitive and psychological dysfunction. Diffusion magnetic resonance imaging (dMRI) can detect alterations in white matter (WM) microstructure, but few studies have examined brain asymmetry. Examining asymmetry in large samples may increase sensitivity to detect heterogeneous areas of WM alteration in mild TBI. Through the Enhancing Neuroimaging Genetics Through Meta-Analysis Military-Relevant Brain Injury working group, we conducted a mega-analysis of neuroimaging and clinical data from 16 cohorts of Active Duty Service Members and Veterans (n = 2598). dMRI data were processed together along with harmonized demographic, injury, psychiatric, and cognitive measures. Fractional anisotropy in the cingulum showed greater asymmetry in individuals with deployment-related TBI, driven by greater left lateralization in TBI. Results remained significant after accounting for potentially confounding variables including posttraumatic stress disorder, depression, and handedness, and were driven primarily by individuals whose worst TBI occurred before age 40. Alterations in the cingulum were also associated with slower processing speed and poorer set shifting. The results indicate an enhancement of the natural left laterality of the cingulum, possibly due to vulnerability of the nondominant hemisphere or compensatory mechanisms in the dominant hemisphere. The cingulum is one of the last WM tracts to mature, reaching peak FA around 42 years old. This effect was primarily detected in individuals whose worst injury occurred before age 40, suggesting that the protracted development of the cingulum may lead to increased vulnerability to insults, such as TBI.

Surveying the Landscape: A Review of Longitudinal TBI Studies in Service Member and Veteran Populations

Traumatic brain injury (TBI) is known to be a signature wound of the post-9/11 conflicts. In response, the U.S. Department of Defense (DOD) and other federal organizations have directed significant investments toward TBI research on characterizing injury populations and understanding long-term outcomes. To address legislative requirements and research gaps, several observational, longitudinal TBI studies were initiated as an effective means of investigating TBI clinical management, outcomes, and recovery. This review synthesizes the landscape (i.e., requirements and gaps, infrastructure, geography, timelines, TBI severity definitions, military and injury populations of interest, and measures) of DOD-funded longitudinal TBI studies being conducted in service member and veteran (SMV) populations. Based on the landscape described here, we present recommended actions and solutions that would allow a consolidated and cooperative future state of longitudinal TBI research, optimized continued investments, and advances in the state of the science without redundancy.

Development of a novel bioengineered 3D brain-like tissue for studying primary blast-induced traumatic brain injury

Primary blast injury is caused by the direct impact of an overpressurization wave on the body. Due to limitations of current models, we have developed a novel approach to study primary blast-induced traumatic brain injury. Specifically, we employ a bioengineered 3D brain-like human tissue culture system composed of collagen-infused silk protein donut-like hydrogels embedded with human IPSC-derived neurons, human astrocytes, and a human microglial cell line. We have utilized this system within an advanced blast simulator (ABS) to expose the 3D brain cultures to a blast wave that can be precisely controlled. These 3D cultures are enclosed in a 3D-printed surrogate skull-like material containing media which are then placed in a holder apparatus inside the ABS. This allows for exposure to the blast wave alone without any secondary injury occurring. We show that blast induces an increase in lactate dehydrogenase activity and glutamate release from the cultures, indicating cellular injury. Additionally, we observe a significant increase in axonal varicosities after blast. These varicosities can be stained with antibodies recognizing amyloid precursor protein. The presence of amyloid precursor protein deposits may indicate a blast-induced axonal transport deficit. After blast injury, we find a transient release of the known TBI biomarkers, UCHL1 and NF-H at 6 h and a delayed increase in S100B at 24 and 48 h. This in vitro model will enable us to gain a better understanding of clinically relevant pathological changes that occur following primary blast and can also be utilized for discovery and characterization of biomarkers.

Neuropsychological Performance and Functional Capacity Following Mild Traumatic Brain Injury in Veterans

OBJECTIVE

To examine the relationship between neuropsychological functioning and performance-based functional capacity in veterans with a history of mild traumatic brain injury (mTBI), as well as the moderating effects of age and psychiatric symptoms on this relationship.

SETTING

Three Veterans Affairs medical centers.

PARTICIPANTS

One hundred nineteen Iraq/Afghanistan veterans with a history of mTBI and self-reported cognitive difficulties.

DESIGN

Cross-sectional, secondary data analysis of baseline measures in a randomized controlled trial.

MAIN MEASURES

The main outcome measure, functional capacity, was assessed using the objective and performance-based University of California San Diego Performance-based Skills Assessment-Brief. A global deficit score (GDS) was created as a composite score for performance on a battery of neuropsychological measures assessing domains of attention, processing speed, executive functioning, and verbal memory performance. Posttraumatic stress disorder (PTSD) symptom severity was assessed using the PTSD Checklist-Military Version, and depressive symptom severity was assessed using the Beck Depression Inventory, Second Edition.

RESULTS

Bivariate analyses indicated that worse neuropsychological performance (ie, higher GDS) and greater PTSD symptom severity were associated with worse communication abilities and worse overall functional capacity. Multiple linear regressions demonstrated that GDS and PTSD symptom severity explained 9% of the variance in communication and 10% of the variance in overall functional capacity; however, GDS emerged as the only significant predictor in both regressions. Age, PTSD, and depressive symptom severity did not moderate the relationship between GDS and overall functional capacity. Performance in the verbal learning and memory domain emerged as the strongest neuropsychological predictor of communication and overall functional capacity.

CONCLUSIONS

Worse neuropsychological functioning was moderately associated with worse performance-based functional capacity, even when accounting for PTSD symptom severity. Verbal learning and memory was the primary neuropsychological domain driving the relationship with functional capacity; improvement in verbal learning and memory may translate into improved functional capacity.

Post-concussive symptoms mediate the relationship between sleep problems and participation restrictions among veterans with mild traumatic brain injury

Background

Sleep problems are common among Veterans with mild traumatic brain injury (mTBI) and may contribute to participation restrictions. However, explanatory mechanisms underlying this relationship are poorly understood. Sleep problems are associated with post-concussive symptoms (e.g., headaches). In turn, post-concussive symptoms contribute to participation restrictions. We hypothesized that post-concussive symptom severity mediates the purported relationship between sleep problems and participation restrictions among Veterans with mTBI.

Materials and Methods

This study was a retrospective analysis of clinical data among 8,733 Veterans with mTBI receiving Veterans Health Administration outpatient care. Sleep problems (yes/no) were identified using the sleep-related item from the Neurobehavioral Symptom Inventory (NSI). Post-concussive symptoms were measured using remaining NSI items. Participation restrictions were measured using the Mayo-Portland Adaptability Inventory Participation Index. We specified a latent variable path model to estimate relationships between: (1) sleep problems and three latent indicators of post-concussive symptoms [vestibular-sensory (e.g., headache)]; mood-behavioral [e.g., anxiety]; cognitive [e.g., forgetfulness]); and, (2) the three latent indicators of post-concussive symptoms and two latent indicators of participation restrictions (social and community participation [e.g., leisure activities]; productivity [e.g., financial management]). We examined the indirect effects of sleep problems upon participation restrictions, as mediated by post-concussive symptoms. Estimates were adjusted for sociodemographic factors (e.g., age), injury characteristics (e.g., blast), and co-morbid conditions (e.g., depression).

Results

87% of Veterans reported sleep problems. Sleep problems were associated with greater social and community participation restrictions, as mediated by mood-behavioral (β = 0.41, p < 0.001) and cognitive symptoms (β = 0.13, p < 0.001). There was no evidence that vestibular-sensory symptoms mediated this relationship (β = -0.01, p = 0.48). Sleep problems were associated with greater productivity restrictions, as mediated by vestibular-sensory (β = 0.16, p < 0.001) and cognitive symptoms (β = 0.14, p < 0.001). There was no evidence that mood-behavioral symptoms mediated this relationship (β = 0.02, p = 0.37).

Discussion

Findings suggest that evidence-based sleep treatment should occupy a prominent role in the rehabilitation of Veterans with mTBI. Indirect effects of sleep problems differed when considering impact on social and community participation vs. productivity, informing individualized rehabilitative care for Veterans with mTBI.

Altered Serotonin 2A (5-HT2A) Receptor Signaling Underlies Mild TBI-Elicited Deficits in Social Dominance

Various forms of traumatic brain injury (TBI) are a leading cause of disability in the United States, with the generation of neuropsychiatric complications such as depression, anxiety, social dysfunction, and suicidality being common comorbidities. Serotonin (5-HT) signaling is linked to psychiatric disorders; however, the effects of neurotrauma on normal, homeostatic 5-HT signaling within the central nervous system (CNS) have not been well characterized. We hypothesize that TBI alters specific components of 5-HT signaling within the CNS and that the elucidation of specific TBI-induced alterations in 5-HT signaling may identify novel targets for pharmacotherapies that ameliorate the neuropsychiatric complications of TBI. Herein, we provide evidence that closed-head blast-induced mild TBI (mTBI) results in selective alterations in cortical 5-HT_2A receptor signaling. We find that mTBI increases in vivo cortical 5-HT_2A receptor sensitivity and ex vivo radioligand binding at time points corresponding with mTBI-induced deficits in social behavior. In contrast, in vivo characterizations of 5-HT_1A receptor function revealed no effect of mTBI. Notably, we find that repeated pharmacologic activation of 5-HT_2A receptors post-injury reverses deficits in social dominance resulting from mTBI. Cumulatively, these studies provide evidence that mTBI drives alterations in cortical 5-HT_2A receptor function and that selective targeting of TBI-elicited alterations in 5-HT_2A receptor signaling may represent a promising avenue for the development of pharmacotherapies for TBI-induced generation of neuropsychiatric disorders.

Global Disability Trajectories Over the First Decade Following Combat Concussion

OBJECTIVE

To examine global disability trajectories in US military with and without traumatic brain injury (TBI) over the first decade following deployment to identify risk profiles for better intervention stratification, hopefully reducing long-term cost.

SETTING

Patients and participants were enrolled in combat or directly following medical evacuation at the time of injury and followed up every 6 months for 10 years.

PARTICIPANTS

There are 4 main groups (n = 475), 2 primary and 2 exploratory: (1) combat-deployed controls without a history of blast exposure "non-blast- control" (n = 143), (2) concussive blast TBI "'blast-TBI" (n = 236) (primary), (3) combat-deployed controls with a history of blast exposure "blast-control" (n = 54), and (4) patients sustaining a combat concussion not from blast "non-blast-TBI" (n = 42) (exploratory).

DESIGN

Prospective, observational, longitudinal study.

MAIN MEASURES

Combat concussion, blast exposure, and subsequent head injury exposure over the first decade post-deployment. Global disability measured by the Glasgow Outcome Scale Extended (GOSE).

RESULTS

Latent class growth analysis identified 4 main trajectories of global outcome, with service members sustaining combat concussion 37 to 49 times more likely to be in the worse disability trajectories than non-blast-controls (blast-TBI: odds ratio [OR] = 49.33; CI, 19.77-123.11; P < .001; non-blast-TBI: OR = 37.50; CI, 10.01-140.50; P < .001). Even blast-exposed-controls were 5 times more likely to be in these worse disability categories compared with non-blast-controls (OR = 5.00; CI, 1.59-15.99; P = .007). Adjustment for demographic factors and subsequent head injury exposure did not substantially alter these odds ratios.

CONCLUSIONS

Very high odds of poor long-term outcome trajectory were identified for those who sustained a concussion in combat, were younger at the time of injury, had lower education, and enlisted in the Army above the risk of deployment alone. These findings help identify a risk profile that could be used to target early intervention and screen for poor long-term outcome to aid in reducing the high public health cost and enhance the long-term quality of life for these service members following deployment.

Cingulo-Opercular and Frontoparietal Network Control of Effort and Fatigue in Mild Traumatic Brain Injury

Neural substrates of fatigue in traumatic brain injury (TBI) are not well understood despite the considerable burden of fatigue on return to productivity. Fatigue is associated with diminishing performance under conditions of high cognitive demand, sense of effort, or need for motivation, all of which are associated with cognitive control brain network integrity. We hypothesize that the pathophysiology of TBI results in damage to diffuse cognitive control networks, disrupting coordination of moment-to-moment monitoring, prediction, and regulation of behavior. We investigate the cingulo-opercular (CO) and frontoparietal (FP) networks, which are engaged to sustain attention for task and maintain performance. A total of 61 individuals with mild TBI and 42 orthopedic control subjects participated in functional MRI during performance of a constant effort task requiring altering the amount of effort (25, 50, or 75% of maximum effort) utilized to manually squeeze a pneumostatic bulb across six 30-s trials. Network-based statistics assessed within-network organization and fluctuation with task manipulations by group. Results demonstrate small group differences in network organization, but considerable group differences in the evolution of task-related modulation of connectivity. The mild TBI group demonstrated elevated CO connectivity throughout the task with little variation in effort level or time on task (TOT), while CO connectivity diminished over time in controls. Several interregional CO connections were predictive of fatigue in the TBI group. In contrast, FP connectivity fluctuated with task manipulations and predicted fatigue in the controls, but connectivity fluctuations were delayed in the mild traumatic brain injury (mTBI) group and did not relate to fatigue. Thus, the mTBI group's hyper-connectivity of the CO irrespective of task demands, along with hypo-connectivity and delayed peak connectivity of the FP, may allow for attainment of task goals, but also contributes to fatigue. Findings are discussed in relation to performance monitoring of prediction error that relies on internal cues from sensorimotor feedback during task performance. Delay or inability to detect and respond to prediction errors in TBI, particularly evident in bilateral insula-temporal CO connectivity, corresponds to day-to-day fatigue and fatigue during task performance.

Perspectives on Primary Blast Injury of the Brain: Translational Insights Into Non-inertial Low-Intensity Blast Injury

Most traumatic brain injuries (TBIs) during military deployment or training are clinically "mild" and frequently caused by non-impact blast exposures. Experimental models were developed to reproduce the biological consequences of high-intensity blasts causing moderate to severe brain injuries. However, the pathophysiological mechanisms of low-intensity blast (LIB)-induced neurological deficits have been understudied. This review provides perspectives on primary blast-induced mild TBI models and discusses translational aspects of LIB exposures as defined by standardized physical parameters including overpressure, impulse, and shock wave velocity. Our mouse LIB-exposure model, which reproduces deployment-related scenarios of open-field blast (OFB), caused neurobehavioral changes, including reduced exploratory activities, elevated anxiety-like levels, impaired nesting behavior, and compromised spatial reference learning and memory. These functional impairments associate with subcellular and ultrastructural neuropathological changes, such as myelinated axonal damage, synaptic alterations, and mitochondrial abnormalities occurring in the absence of gross- or cellular damage. Biochemically, we observed dysfunctional mitochondrial pathways that led to elevated oxidative stress, impaired fission-fusion dynamics, diminished mitophagy, decreased oxidative phosphorylation, and compensated cell respiration-relevant enzyme activity. LIB also induced increased levels of total tau, phosphorylated tau, and amyloid β peptide, suggesting initiation of signaling cascades leading to neurodegeneration. We also compare translational aspects of OFB findings to alternative blast injury models. By scoping relevant recent research findings, we provide recommendations for future preclinical studies to better reflect military-operational and clinical realities. Overall, better alignment of preclinical models with clinical observations and experience related to military injuries will facilitate development of more precise diagnosis, clinical evaluation, treatment, and rehabilitation.

Association Between Self-Reported Disability and Lifetime History of Traumatic Brain Injury With Loss of Consciousness Among Veterans and Nonveterans in North Carolina

BACKGROUND

Compared with civilians, service members and veterans who have a history of traumatic brain injury (TBI) are more likely to experience poorer physical and mental health. To investigate this further, this article examines the association between self-reported history of TBI with loss of consciousness and living with 1 or more current disabilities (ie, serious difficulty with hearing, vision, cognition, or mobility; any difficulty with self-care or independent living) for both veterans and nonveterans.

METHODS

A cross-sectional study using data from the North Carolina Behavioral Risk Factor Surveillance System for 4733 veterans and nonveterans aged 18 years and older.

RESULTS

Approximately 34.7% of veterans residing in North Carolina reported having a lifetime history of TBI compared with 23.6% of nonveterans. Veterans reporting a lifetime history of TBI had a 1.4 times greater risk of also reporting living with a current disability (adjusted prevalence ratio = 1.4; 95% confidence interval, 1.2-1.8) compared with nonveterans. The most common types of disabilities reported were mobility, cognitive, and hearing.

CONCLUSIONS

Compared with nonveterans, veterans who reported a lifetime history of TBI had an increased risk of reporting a current disability. Future studies, such as longitudinal studies, may further explore this to inform the development of interventions.

Concussion Knowledge and Attitudes in Reserve Officers' Training Corps Cadets

INTRODUCTION

Military members' knowledge of concussion signs and symptoms may be critical to appropriate concussion identification and health-seeking behavior, particularly for those in leadership roles. The current study aimed to characterize concussion knowledge and attitudes among future military officers undergoing U.S.-based Reserve Officers' Training Corps (ROTC) training.

MATERIALS AND METHODS

Army and Air Force ROTC cadets at 2 large, public universities were utilized for a survey-based observational study. The study was approved by the institutional review board at both university research sites. Cadets completed a modified Rosenbaum Concussion Knowledge and Attitude Survey to obtain cadets' Concussion Knowledge Index and Concussion Attitude Index, where higher scores are preferable. Cadets' concussion knowledge and attitudes were characterized via descriptive statistics.

RESULTS

Cadets (n = 110) had a mean Concussion Knowledge Index of 18.8 ± 3.2 (range = 9-23, out of 25). Potentially detrimental misconceptions included: belief that typically concussion symptoms no longer persist after 10 days (79.1%) and brain imaging shows visible physical damage following concussion (74.5%). Mean Concussion Attitude Index was 60.6 ± 7.4 (range = 46-75, out of 75). In general, cadets reported higher agreement with safe concussion behavior than what they believe peers would report.

CONCLUSIONS

Cadets were found to have a high concussion knowledge, yet common misconceptions remained. Cadets consistently reported safe choices but were less sure that peers felt similarly; future investigations should evaluate ROTC concussion social norms and education should note peers' beliefs supporting safe concussion attitudes.

Time Since Injury as a Factor in Post-Concussion Symptom Reporting among Military Service Members with Blast-Related Concussion

Over the last decade, much research has been devoted to concussion among military personnel. Post-concussion symptoms after blast-related concussion are common, but it is unknown whether symptom reporting differs over time. This study's objective was to assess the relationship between time since injury and post-concussion symptom reporting. We conducted a retrospective review of existing records to identify service members who experienced blast-related concussion during deployment between 2007 and 2012 and who responded to a Post-Deployment Health Assessment (PDHA). The study population included 3690 military personnel grouped by time between injury and PDHA completion: 1-90 days (45.3%, n = 1,673), 91-180 days (33.0%, n = 1,216), or 181-365 days (21.7%, n = 801). Post-concussion symptoms assessed on the PDHA included headache, tinnitus, memory problems, concentration problems, difficulty making decisions, irritability, dizziness, and sleep problems. All post-concussion symptoms were higher for 91-180 days and 181-365 days after injury relative to 1-90 days, with the exception of dizziness. After adjustment for loss of consciousness, mental health comorbidity, and other covariates, the odds of reporting three or more post-concussion symptoms were significantly higher in those who completed the PDHA 91-180 days (odds ratio: 1.29; 95% confidence interval: 1.09-1.51) or 181-365 days after injury (odds ratio: 1.33; 95% confidence interval: 1.09-1.61), compared with the 1-90 days group. These findings suggest that refinements to in-theater medical care may be needed to reduce post-concussion symptom burden and improve the prospect of concussion recovery.

Epidemiology of Chronic Effects of Traumatic Brain Injury

Although many patients diagnosed with traumatic brain injury (TBI), particularly mild TBI, recover from their symptoms within a few weeks, a small but meaningful subset experience symptoms that persist for months or years after injury and significantly impact quality of life for the person and their family. Factors associated with an increased likelihood of negative TBI outcomes include not only characteristics of the injury and injury mechanism, but also the person’s age, pre-injury status, comorbid conditions, environment, and propensity for resilience. In this article, as part of the Brain Trauma Blueprint: TBI State of the Science framework, we examine the epidemiology of long-term outcomes of TBI, including incidence, prevalence, and risk factors. We identify the need for increased longitudinal, global, standardized, and validated assessments on incidence, recovery, and treatments, as well as standardized assessments of the influence of genetics, race, ethnicity, sex, and environment on TBI outcomes. By identifying how epidemiological factors contribute to TBI outcomes in different groups of persons and potentially impact differential disease progression, we can guide investigators and clinicians toward more-precise patient diagnosis, along with tailored management, and improve clinical trial designs, data evaluation, and patient selection criteria.

Different methods for TBI diagnosis influence presence and symptoms of post-concussive syndrome in US Veterans

Common methods for evaluating history of traumatic brain injury (TBI) include self-report, electronic medical record review (EMR), and structured interviews such as the Head Trauma Events Characteristics (HTEC). Each has strengths and weaknesses, but little is known regarding how TBI diagnostic rates or the associated symptom profile differ among them. This study examined 200 Veterans recruited within the VA Portland Health Care System, each evaluated for TBI using self-report, EMR, and HTEC. Participants also completed validated questionnaires assessing chronic symptom severity in broad health-related domains (pain, sleep, quality of life, post-concussive symptoms). The HTEC was more sensitive (80% of participants in our cohort) than either self-report or EMR alone (40%). As expected from the high sensitivity, the HTEC+ group included many people with mild or no post-concussive symptoms. Participants were then grouped according to the degree of concordance across these three diagnostic methods: No-TBI, n=43; or TBI-positive in any one method (TBI-1dx, n=53), any two (TBI-2dx, n=45), or all three (TBI-3dx, n=59). The symptom profile of the TBI-1dx group was indistinguishable from the No TBI group. The TBI-3dx group carried the most severe symptom profile. These data show that understanding the method(s) used to ascertain TBI is essential when interpreting results from other studies, an issue that will be even more salient when interpreting data merged from multiple sources within centralized repositories (e.g., FITBIR). The development of a composite TBI assessment tool including self-report, medical record review, and neuropsychology outcomes is a crucial next step for the field.

Association of Lifetime TBI and Military Employment with Late-Life ADL Functioning: A Population-Based Prospective Cohort Study

OBJECTIVE

To determine associations of traumatic brain injury (TBI) and military employment with activities of daily living (ADL) in late life.

SETTING

Community-based integrated healthcare delivery system.

PARTICIPANTS

Male (n=2066) and female (n=2887), aged 65+ and dementia-free.

DESIGN

Population-based prospective cohort study with biennial follow-up and censoring at time of dementia diagnosis.

MAIN OUTCOME MEASURES

ADL difficulties at baseline and accumulation during follow-up.

RESULTS

TBI with loss of consciousness (LOC) before age 40 was associated with slightly higher ADL difficulty at baseline for females (RR=1.44, 95% CI: 1.08-1.93, p=0.01). For males, TBI with LOC at any age was associated with greater ADL difficulty at baseline (age <40: RR=1.58, 95% CI: 1.20 - 2.08, p = 0.001; age 40+: RR=2.14, 95% CI: 1.24 - 3.68, p = 0.006). TBI with LOC was not associated with the rate of accumulation of ADL difficulties over time in males or females. There was no evidence of an association between military employment and either outcome, nor of an interaction between military employment and TBI with LOC. Findings were consistent across a variety of sensitivity analyses.

CONCLUSION

Further investigation into factors underlying greater late-life functional impairment among TBI survivors is warranted.

Elevated Tau in Military Personnel Relates to Chronic Symptoms Following Traumatic Brain Injury

OBJECTIVE

To understand the relationships between traumatic brain injury (TBI), blood biomarkers, and symptoms of posttraumatic stress disorder (PTSD), depression, and postconcussive syndrome symptoms.

DESIGN

Cross-sectional cohort study using multivariate analyses.

PARTICIPANTS

One hundred nine military personnel and veterans, both with and without a history of TBI.

MAIN MEASURES

PTSD Checklist-Civilian Version (PCL-C); Neurobehavioral Symptom Inventory (NSI); Ohio State University TBI Identification Method; Patient Health Questionnaire-9 (PHQ-9); Simoa-measured concentrations of tau, amyloid-beta (Aβ) 40, Aβ42, and neurofilament light (NFL).

RESULTS

Controlling for age, sex, time since last injury (TSLI), and antianxiety/depression medication use, NFL was trending toward being significantly elevated in participants who had sustained 3 or more TBIs compared with those who had sustained 1 or 2 TBIs. Within the TBI group, partial correlations that controlled for age, sex, TSLI, and antianxiety/depression medication use showed that tau concentrations were significantly correlated with greater symptom severity, as measured with the NSI, PCL, and PHQ-9.

CONCLUSIONS

Elevations in tau are associated with symptom severity after TBI, while NFL levels are elevated in those with a history of repetitive TBIs and in military personnel and veterans. This study shows the utility of measuring biomarkers chronically postinjury. Furthermore, there is a critical need for studies of biomarkers longitudinally following TBI.

Poor sleep correlates with biomarkers of neurodegeneration in mild traumatic brain injury patients: a CENC study

STUDY OBJECTIVES

Sleep disorders affect over half of mild traumatic brain injury (mTBI) patients. Despite evidence linking sleep and neurodegeneration, longitudinal TBI-related dementia studies have not considered sleep. We hypothesized that poor sleepers with mTBI would have elevated markers of neurodegeneration and lower cognitive function compared to mTBI good sleepers and controls. Our objective was to compare biomarkers of neurodegeneration and cognitive function with sleep quality in warfighters with chronic mTBI.

METHODS

In an observational warfighters cohort (n = 138 mTBI, 44 controls), the Pittsburgh Sleep Quality Index (PSQI) was compared with plasma biomarkers of neurodegeneration and cognitive scores collected an average of 8 years after injury.

RESULTS

In the mTBI cohort, poor sleepers (PSQI ≥ 10, n = 86) had elevated plasma neurofilament light (NfL, x̅ = 11.86 vs 7.91 pg/mL, p = 0.0007, d = 0.63) and lower executive function scores by the categorical fluency (x̅ = 18.0 vs 21.0, p = 0.0005, d = -0.65) and stop-go tests (x̅ = 30.1 vs 31.1, p = 0.024, d = -0.37). These findings were not observed in controls (n = 44). PSQI predicted NfL (beta = 0.22, p = 0.00002) and tau (beta = 0.14, p = 0.007), but not amyloid β42. Poor sleepers showed higher obstructive sleep apnea (OSA) risk by STOP-BANG scores (x̅ = 3.8 vs 2.7, p = 0.0005), raising the possibility that the PSQI might be partly secondary to OSA.

CONCLUSIONS

Poor sleep is linked to neurodegeneration and select measures of executive function in mTBI patients. This supports implementation of validated sleep measures in longitudinal studies investigating pathobiological mechanisms of TBI related neurodegeneration, which could have therapeutic implications.

Burden of Behavioral Health Comorbidities on Outpatient Health Care Utilization by Active Duty Service Members With a First Documented mTBI

OBJECTIVE

More than 280,000 Active Duty Service Members (ADSMs) sustained a mild traumatic brain injury (mTBI) between 2000 and 2019 (Q3). Previous studies of veterans have shown higher utilization of outpatient health clinics by veterans diagnosed with mTBI. Additionally, veterans with mTBI and comorbid behavioral health (BH) conditions such as post-traumatic stress disorder, depression, and substance use disorders have significantly higher health care utilization than veterans diagnosed with mTBI alone. However, few studies of the relationship between mTBI, health care utilization, and BH conditions in the active duty military population currently exist. We examined the proportion of ADSMs with a BH diagnosis before and after a first documented mTBI and quantified outpatient utilization of the Military Health System in the year before and following injury.

MATERIALS AND METHODS

Retrospective analysis of 4,901,840 outpatient encounters for 39,559 ADSMs with a first documented diagnosis of mTBI recorded in the Department of Defense electronic health record, subsets of who had a BH diagnosis. We examined median outpatient utilization 1 year before and 1 year after mTBI using Wilcoxon signed rank test, and the results are reported with an effect size r. Outpatient utilization is compared by BH subgroups.

RESULTS

Approximately 60% of ADSMs experience a first mTBI with no associated BH condition, but 17% of men and women are newly diagnosed with a BH condition in the year following mTBI. ADSMs with a history of a BH condition before mTBI increased their median outpatient utilization from 23 to 35 visits for men and from 32 to 42 visits for women. In previously healthy ADSMs with a new BH condition following mTBI, men more than tripled median utilization from 7 to 24 outpatient visits, and women doubled utilization from 15 to 32 outpatient visits.

CONCLUSIONS

Behavioral health comorbidities affect approximately one-third of ADSMs following a first mTBI, and approximately 17% of previously healthy active duty men and women will be diagnosed with a new BH condition in the year following a first mTBI. Post-mTBI outpatient health care utilization is highly dependent on the presence or absence of BH condition and is markedly higher is ADSMs with a BH diagnosis in the year after a first documented mTBI.

Coordinating Global Multi-Site Studies of Military-Relevant Traumatic Brain Injury: Opportunities, Challenges, and Harmonization Guidelines

Traumatic brain injury (TBI) is common among military personnel and the civilian population and is often followed by a heterogeneous array of clinical, cognitive, behavioral, mood, and neuroimaging changes. Unlike many neurological disorders that have a characteristic abnormal central neurologic area(s) of abnormality pathognomonic to the disorder, a sufficient head impact may cause focal, multifocal, diffuse or combination of injury to the brain. This inconsistent presentation makes it difficult to establish or validate biological and imaging markers that could help improve diagnostic and prognostic accuracy in this patient population. The purpose of this manuscript is to describe both the challenges and opportunities when conducting military-relevant TBI research and introduce the Enhancing NeuroImaging Genetics through Meta-Analysis (ENIGMA) Military Brain Injury working group. ENIGMA is a worldwide consortium focused on improving replicability and analytical power through data sharing and collaboration. In this paper, we discuss challenges affecting efforts to aggregate data in this patient group. In addition, we highlight how "big data" approaches might be used to understand better the role that each of these variables might play in the imaging and functional phenotypes of TBI in Service member and Veteran populations, and how data may be used to examine important military specific issues such as return to duty, the late effects of combat-related injury, and alteration of the natural aging processes.

Functional recovery after brain injury: Independent predictors of psychosocial outcome one year after TBI

INTRODUCTION

Traumatic Brain Injury (TBI) is the leading cause of death and disability in people aged under 40 in the UK. Many patients suffer residual deficits, which limits their functional recovery. The aim of this study was to determine independent predictors of functional outcome at 1-year post-TBI.

METHODS

Utilising a prospective observational cohort design, 1131 consecutive adult admissions with non-recurrent TBI were recruited from the ED (Emergency Department). Using routine consultant-led follow up clinics, data was collected between August 2011 and July 2015. The Rivermead Head Injury Follow Up Questionnaire (RHFUQ) was used to measure psychosocial function at 1 year.

RESULTS

A multiple linear regression model showed that previous psychiatric history (p < 0.001), lower Glasgow Coma Scale (p < 0.001), a severe CT scan (p = 0.002), aetiology of assault compared to sport (p = 0.011) and falls (p = 0.005), initial unemployment (p < 0.001) and no job at 8-10 weeks (p < 0.001) after TBI had a significant association with a worse RHFUQ score at 1 year. Follow up rate was >90 %.

CONCLUSIONS

This study adds valuable information on the prognostic indicators of TBI recovery and possible targets for intervention. Future development of a validated prognostic model to predict long term functional outcomes after TBI will help improve long-term treatment of the condition.

Estimates of Long-Term Disability Among US Service Members With Traumatic Brain Injuries

BACKGROUND

Traumatic brain injury (TBI) is a significant health issue in the US military. The purpose of this study was to estimate the probability of long-term disability among hospitalized service members (SMs) with TBIs, using the South Carolina Traumatic Brain Injury and Follow-up Registry (SCTBIFR) model developed on civilian hospitalized patients.

METHODS

We identified military patients in military or civilian hospitals or theater level 3 to 5 military treatment facilities (MTFs) whose first TBI occurred between October 1, 2013, and September 30, 2015. TBI-related disability at 1-year post-hospital discharge was estimated using regression coefficients from the SCTBIFR.

RESULTS

Among the identified 4877 SMs, an estimated 65.6% of SMs with severe TBI, 56.2% with penetrating TBI, 31.4% with moderate TBI, and 12.0% with mild TBI are predicted to develop long-term disability. TBI patients identified at theater level 4 and 5 MTFs had an average long-term disability rate of 56.9% and 61.1%, respectively. In total, we estimate that 25.2% of all SMs hospitalized with TBI will develop long-term disability.

CONCLUSION

Applying SCTBIFR long-term probability estimates to US SMs with TBIs provides useful disability estimates to inform providers and health systems on the likelihood that particular subgroups of TBI patients will require continued support and long-term care.

Estimating minimal clinically important differences for two scales in patients with chronic traumatic brain injury

BACKGROUND

This study aimed to establish the minimal clinically important difference (MCID) for the Fugl-Meyer Motor Scale (FMMS) and the Disability Rating Scale (DRS) to evaluate interventions in patients with motor deficits in the chronic phase after traumatic brain injury (TBI).

METHODS

MCIDs were established with a structured expert consultation process, the RAND/UCLA modified Delphi method. This process consisted of a literature review and input from a 10-person, multidisciplinary expert panel. The experts were asked to rate meaningfulness of improvements in hypothetical patients and numeric changes via two rounds of ratings and an in-person meeting.

RESULTS

The estimated MCIDs were six and five points on the FMMS Upper and Lower Extremity Scale, respectively, and one point on the DRS. The experts argued against establishing an MCID for the combined FMMS because the same change was more likely to be meaningful if concentrated in one extremity and because a meaningful improvement in one extremity implies meaningfulness irrespective of the changes in the other.

CONCLUSIONS

This study is the first to establish MCIDs for the FMMS and the DRS in the chronic phase after TBI. The results may be helpful for the design and interpretation of clinical trials of interventions.

Provider Training in the Management of Headache Following Concussion Clinical Recommendation: Promoting a Standardized Means for Efficient Patient Recovery and Timely Return to Duty

Background: Headache is a common symptom reported following concussion/mild traumatic brain injury. The Department of Defense's clinical recommendation (CR) describes guidance for primary care providers for the management of post-traumatic headache (PTH) in Service members.

Objective: The objective of this study is to examine the association between training on the CR with provider clinical practice, patient behaviors, and symptom recovery.

Methods: Participants were healthcare providers and two patient groups (one receiving care as usual [CAU] and another receiving care after provider training on PTH CR [CR+]). Providers were interviewed at three time points: (1) prior to CAU enrollment; (2) after CAU enrollment, but prior to training; and (3) after CR+ follow-up. Data from the second and third provider interview were used to evaluate a potential difference between provider practices pre- and post-training (n = 13). Patients were enrolled within 6 months of concussion. Patient outcomes (including neurobehavioral and headache symptoms) were assessed at three time-points: within 72 h (n = 35), at 1-week (n = 34) and at 1-month post-enrollment (n = 27).

Results: Most follow-up care reported by providers were recommended within 72 h of initial visit post-training vs. >1 week pre-training. Additionally, providers reported a greater number of visits based on patient symptoms after training than before. Post-training, most providers reported referring patients to higher level of care “as needed,” if not “very rarely,” compared to 25% reported referrals prior to training. At 1-week post-enrollment the CR+ patient group reported more frequent medical provider visits compared to the CAU group. This trend was reversed at the 1-month follow-up whereby more CAU reported seeing a medical provider compared to CR+. By 1-week post-enrollment, fewer patients in the CR+ group reported being referred to any other providers or specialists compared to the CAU group. No differences in patient outcomes by provider training was found.

Conclusion: The study results demonstrate the feasibility of training on the Management of Headache Following Concussion CR in order to change provider practices by promoting timely care, and promoting patient compliance as shown through improvement in follow-up visits and more monitoring within the primary care clinic.

Comparison of Clinical Outcomes 1 and 5 Years Post-Injury Following Combat Concussion

OBJECTIVE

To compare 1-year and 5-year clinical outcomes in 2 groups of combat-deployed service members without brain injury to those of 2 groups with combat-related concussion to better understand long-term clinical outcome trajectories.

METHODS

This prospective, observational, longitudinal multicohort study examined 4 combat-deployed groups: controls without head injury with or without blast exposure and patients with combat concussion arising from blast or blunt trauma. One-year and 5-year clinical evaluations included identical batteries for neurobehavioral, psychiatric, and cognitive outcomes. A total of 347 participants completed both time points of evaluation. Cross-sectional and longitudinal comparisons were assessed. Overall group effect was modeled as a 4-category variable with rank regression adjusting for demographic factors using a 2-sided significance threshold of 0.05, with post hoc Tukey p values calculated for the pairwise comparisons.

RESULTS

Significant group differences in both combat concussion groups were identified cross-sectionally at 5-year follow-up compared to controls in neurobehavioral (Neurobehavioral Rating Scale-Revised [NRS]; Cohen d, -1.10 to -1.40, confidence intervals [CIs] [-0.82, -1.32] to [-0.97, -1.83] by group) and psychiatric domains (Clinician-Administered PTSD Scale for DSM-IV [CAPS]; Cohen d, -0.91 to -1.19, CIs [-0.63, -1.19] to [-0.76, -1.62] by group) symptoms with minimal differences in cognitive performance. Both combat concussion groups also showed clinically significant decline from 1- to 5-year evaluation (66%-76% neurobehavioral NRS; 41%-54% psychiatric CAPS by group). Both control groups fared better but a subset also had clinically significant decline (37%-50% neurobehavioral NRS; 9%-25% psychiatric CAPS by group).

CONCLUSIONS

There was an evolution, not resolution, of symptoms from 1- to 5-year evaluation, challenging the assumption that chronic stages of concussive injury are relatively stable. Even some of the combat-deployed controls worsened. The evidence supports new considerations for chronic trajectories of concussion outcome in combat-deployed service members.

Functional and Structural Neuroimaging Correlates of Repetitive Low-Level Blast Exposure in Career Breachers

Combat military and civilian law enforcement personnel may be exposed to repetitive low-intensity blast events during training and operations. Persons who use explosives to gain entry (i.e., breach) into buildings are known as “breachers” or dynamic entry personnel. Breachers operate under the guidance of established safety protocols, but despite these precautions, breachers who are exposed to low-level blast throughout their careers frequently report performance deficits and symptoms to healthcare providers. Although little is known about the etiology linking blast exposure to clinical symptoms in humans, animal studies demonstrate network-level changes in brain function, alterations in brain morphology, vascular and inflammatory changes, hearing loss, and even alterations in gene expression after repeated blast exposure. To explore whether similar effects occur in humans, we collected a comprehensive data battery from 20 experienced breachers exposed to blast throughout their careers and 14 military and law enforcement controls. This battery included neuropsychological assessments, blood biomarkers, and magnetic resonance imaging measures, including cortical thickness, diffusion tensor imaging of white matter, functional connectivity, and perfusion. To better understand the relationship between repetitive low-level blast exposure and behavioral and imaging differences in humans, we analyzed the data using similarity-driven multi-view linear reconstruction (SiMLR). SiMLR is specifically designed for multiple modality statistical integration using dimensionality-reduction techniques for studies with high-dimensional, yet sparse, data (i.e., low number of subjects and many data per subject). We identify significant group effects in these data spanning brain structure, function, and blood biomarkers.

Neurovascular Coupling in Special Operations Forces Combat Soldiers

The purpose of this study was to investigate how concussion history affects neurovascular coupling in Special Operations Forces (SOF) combat Soldiers. We studied 100 SOF combat Soldiers [age = 33.5 ± 4.3 years; height = 180.4 ± 6.0 cm; 55 (55.0%) with self-reported concussion history]. We employed transcranial Doppler (TCD) ultrasound to assess neurovascular coupling (NVC) via changes in posterior cerebral artery (PCA) velocity in response to a reading and a visual search task. Baseline TCD data were collected for 2 min. NVC was quantified by the percent change in overall PCA response curves. We employed linear mixed effect models using a linear spline with one knot to assess group differences in percent change observed in the PCA velocity response curves between SOF combat Soldiers with and without a concussion history. Baseline PCA velocity did not significantly differ (t₉₈ = 1.28, p = 0.20) between those with and without concussion history. Relative PCA velocity response curves did not differ between those with and without a concussion history during the reading task (F_1,98 = 0.80, p = 0.37) or the visual search task (F_1,98 = 0.52, p = 0.47). When assessing only SOF combat Soldiers with a concussion history, differential response to task was significantly greater in those with 3 or more concussions (F_1,4341 = 27.24, p < 0.0001) relative to those with 1-2 concussions. Despite no main effect of concussion history on neurovascular coupling response in SOF combat Soldiers, we observed a dose-response based on lifetime concussion incidence. While long-term neurophysiological effects associated with head impact and blast-related injury are currently unknown, assessing NVC response may provide further insight into cerebrovascular function and overall physiological health.

Mild TBI/Concussion Clinical Tools for Providers Used Within the Department of Defense and Defense Health Agency

BACKGROUND

Military personnel are at greater risk for sustaining mild traumatic brain injury (mTBI), or concussion, whether they are in a combat or garrison setting. Consequently, mTBI is a major health concern for health practitioners to understand, in order to provide timely assessment and treatment to service members (SM) who are suspected to have mTBI.

OBSERVATIONS

Providing early diagnosis and effective management of symptoms can optimize recovery and promote healthy outcomes. Understanding what resources and guidelines are available is important for those evaluating active duty SMs within the Military Health System.

CONCLUSIONS

This article showcases clinical tools for screening, evaluating, and diagnosing concussion used within the US Department of Defense, and provides resources for practitioners to find these clinical tools online.

Response inhibition in Veterans with a history of mild traumatic brain injury: The role of self-reported complaints in objective performance

INTRODUCTION

Although objective deficits in response inhibition (RI) have been detected in civilians with mild traumatic brain injury (mTBI), it remains unclear whether objective RI is worse in military Veterans with mTBI despite the prevalence of self-reported disinhibition. Assessing RI in Veterans is critical due to their unique characteristics, including combat and blast exposure, in addition to the prevalence of psychiatric comorbidity. Therefore, the aims of this study were to (1) examine RI performance in Veterans with mTBI compared to non-mTBI Veterans and (2) compare RI performance in well-defined subgroups of mTBI Veterans with and without self-reported complaints of disinhibition to non-mTBI Veterans.

METHOD

53 mTBI Veterans and 37 non-mTBI Veterans completed a Go/No-Go RI task and measures of self-reported disinhibition (Frontal Systems Behavior Scale) and psychiatric symptoms. ANCOVAs covarying for mood and demographics compared RI performances of the non-mTBI Veterans to (1) the total sample of mTBI Veterans (n= 53) and to (2) mTBI Veterans with elevated (t-score ≥ 60; mTBI-SubjDis; n= 23) and low (t-score < 60; mTBI-NoSubjDis; n= 30) levels of self-reported disinhibition.

RESULTS

There were no significant differences in RI between the mTBI group as a whole and the non-mTBI Veterans group. However, when Veterans with mTBI were divided into groups by clinically-significant concern about their disinhibition, the mTBI-SubjDis group demonstrated significantly worse RI than the mTBI-NoSubjDis and non-mTBI Veteran groups. No significant differences in RI performance were observed between the mTBI-NoSubjDis and non-mTBI Veteran groups.

CONCLUSIONS

Results indicate that mTBI Veterans with elevated levels of self-reported disinhibition show diminished performance on objective measures of RI, independent of mood. Findings highlight the unique contribution of subjective complaints on executive functioning in mTBI, and they underscore the importance of assessing cognitive complaints in order to identify those most at risk for poor-long term outcomes.

Exosomal MicroRNAs in Military Personnel with Mild Traumatic Brain Injury: Preliminary Results from the Chronic Effects of Neurotrauma Consortium Biomarker Discovery Project

Chronic symptoms after mild traumatic brain injury (mTBI) are common among veterans and service members, and represent a significant source of morbidity, with those who sustain multiple mTBIs at greatest risk. Exosomal micro-RNAs (miRNAs), mediators of intercellular communication, may be involved in chronic TBI symptom persistence. Exosomal miRNA (exomiR) was extracted from 153 participants enrolled in the Chronic Effect of Neurotrauma Consortium (CENC) longitudinal study (no TBI, n = 35; ≥ 3 mTBIs (rTBI), n = 45; 1-2 mTBIs, n = 73). Analyses were performed with nCounter^® Human miRNA Expression Panels and Ingenuity Pathway Analysis (IPA) for identification of gene networks associated with TBI. Generalized linear models were used to analyze the predictive value of exomiR dysregulation and remote neurobehavioral symptoms. Compared with controls, there were 17 dysregulated exomiRs in the entire mTBI group and 32 dysregulated exomiRs in the rTBI group. Two miRNAs, hsa-miR-139-5p and hsa-miR-18a-5p, were significantly differentially expressed in the rTBI and 1-2 mTBI groups. IPA analyses showed that these dysregulated exomiRs correlated with pathways of inflammatory regulation, neurological disease, and cell development. Within the rTBI group, exomiRs correlated with gene activity for hub-genes of tumor protein TP53, insulin-like growth factor 1 receptor, and transforming growth factor beta. TBI history and neurobehavioral symptom survey scores negatively and significantly correlated with hsa-miR-103a-3p expression. Participants with remote mTBI have distinct exomiR profiles, which are significantly linked to inflammatory and neuronal repair pathways. These profiles suggest that analysis of exosomal miRNA expression may provide novel insights into the underlying pathobiology of chronic TBI symptom persistence.

Late contributions of repetitive head impacts and TBI to depression symptoms and cognition

OBJECTIVE

To test the hypothesis that repetitive head impacts (RHIs), like those from contact sport play and traumatic brain injury (TBI) have long-term neuropsychiatric and cognitive consequences, we compared middle-age and older adult participants who reported a history of RHI and/or TBI with those without this history on measures of depression and cognition.

METHODS

This cross-sectional study included 13,323 individuals (mean age, 61.95; 72.5% female) from the Brain Health Registry who completed online assessments, including the Ohio State University TBI Identification Method, the Geriatric Depression Scale (GDS-15), and the CogState Brief Battery and Lumos Labs NeuroCognitive Performance Tests. Inverse propensity-weighted linear regressions accounting for age, sex, race/ethnicity, and education tested the effects of RHI and TBI compared to a non-RHI/TBI group.

RESULTS

A total of 725 participants reported RHI exposure (mostly contact sport play and abuse) and 7,277 reported TBI (n = 2,604 with loss of consciousness [LOC]). RHI (β, 1.24; 95% CI, 0.36-2.12), TBI without LOC (β, 0.43; 95% CI, 0.31-0.54), and TBI with LOC (β, 0.75; 95% CI, 0.59-0.91) corresponded to higher GDS-15 scores. While TBI with LOC had the most neuropsychological associations, TBI without LOC had a negative effect on CogState Identification (β, 0.004; 95% CI, 0.001-0.01) and CogState One Back Test (β, 0.004; 95% CI, 0.0002-0.01). RHI predicted worse CogState One Back Test scores (β, 0.02; 95% CI, -0.01 to 0.05). There were RHI × TBI interaction effects on several neuropsychological subtests, and participants who had a history of both RHI and TBI with LOC had the greatest depression symptoms and worse cognition.

CONCLUSIONS

RHI and TBI independently contributed to worse mid- to later-life neuropsychiatric and cognitive functioning.

Interleukin-6 is associated with acute concussion in military combat personnel

BACKGROUND

Concussion is the most common type of TBI, yet reliable objective measures related to these injuries and associated recovery processes remain elusive, especially in military personnel. The purpose of this study was to characterize the relationship between cytokines and recovery from acute brain injury in active duty service members. Inflammatory cytokines (IL-6, IL-10, and TNFα) were measured acutely in blood samples within 8 h following a medically diagnosed concussion and then 24 h later.

METHODS

Participants (n = 94) were categorized into two groups: 1) military personnel who sustained provider-diagnosed concussion, without other major medical diagnosis (n = 45) and 2) healthy control participants in the same deployment environment who did not sustain concussion or other illness or injuries (n = 49). IL-6, IL-10, and TNFα concentrations were measured using an ultrasensitive single-molecule enzyme-linked immunosorbent assay. Differences in cytokine levels between concussed and healthy groups were evaluated at two time points (time point 1 ≤ 8 h after injury; time point 2 = 24 h following time point 1).

RESULTS

At time point 1, IL-6 median (IQR) concentrations were 2.62 (3.62) in the concussed group, which was greater compared to IL-6 in the healthy control group (1.03 (0.90); U = 420.00, z = - 5.12, p < 0.001). Compared to healthy controls, the concussed group did not differ at time point 1 in IL-10 or TNFα concentrations (p's > 0.05). At time point 2, no differences were detected between concussed and healthy controls for IL-6, IL-10, or TNFα (p's > 0.05). The median difference between time points 1 and 2 were compared between the concussed and healthy control groups for IL-6, IL-10, and TNFα. Change in IL-6 across time was greater for the concussed group than healthy control (- 1.54 (3.12); U = 315.00, z = - 5.96, p < 0.001), with no differences between groups in the change of IL-10 or TNFα (p's > 0.05).

CONCLUSION

Reported here is a significant elevation of IL-6 levels in concussed military personnel less than 8 h following injury. Future studies may examine acute and chronic neurological symptomology associated with inflammatory cytokine levels, distinguish individuals at high risk for developing neurological complications, and identify underlying biological pathways to mitigate inflammation and improve outcomes.

Traumatic Brain Injury Following Military Deployment: Evaluation of Diagnosis and Cause of Injury

OBJECTIVE

To evaluate the prevalence of delayed traumatic brain injury (TBI) diagnosis and cause of injury that resulted in a TBI diagnosis after military deployment.

DESIGN

Medical record notes were reviewed in 2016 from a random sample of 1150 US military service members who had their first-time deployment in 2011 and likely sustained a TBI. Location and cause of the injury were extracted from the progress note for analysis.

PARTICIPANTS AND SETTING

Active-duty US military service members who received an International Classification of Diseases, Ninth Revision code for a TBI diagnosis in a military facility.

MAIN OUTCOME MEASURES

Presence of TBI, location of injury, cause of injury, and time of diagnosis with respect to deployment.

RESULTS

The odds of being diagnosed with a deployment-related TBI were 8 times higher during the first 4 weeks upon return from deployment than the subsequent 32 weeks. The likelihood of diagnosing a deployment-sustained TBI during weeks 5 to 32 was 2 times higher than during 33 to 76 weeks following return from deployment. The proportion of deployment-related TBI diagnoses decreased with time following return from deployment but remained above 40% during weeks 33 to 76. Service branch, gender, race, occupation, and time between TBI diagnosis and return from deployment were significant predictors of deployment-related TBIs. Moving motor vehicle, sports, parachute, and being struck by objects were the top causes of injury in garrison (nondeployed setting), whereas blast produced the majority (66%) of all causes of injuries that resulted in a TBI in the deployed setting.

CONCLUSION

The increased incidence rate of a TBI diagnosis following deployment can be attributed to delayed diagnosis of TBI sustained from injuries during deployment. TBIs sustained during deployment can be diagnosed beyond the initial 4 weeks after return from deployment and may continue up to 76 weeks following return from deployment.

A Moderate Blast Exposure Results in Dysregulated Gene Network Activity Related to Cell Death, Survival, Structure, and Metabolism

Blast exposure is common in military personnel during training and combat operations, yet biological mechanisms related to cell survival and function that coordinate recovery remain poorly understood. This study explored how moderate blast exposure influences gene expression; specifically, gene-network changes following moderate blast exposure. On day 1 (baseline) of a 10-day military training program, blood samples were drawn, and health and demographic information collected. Helmets equipped with bilateral sensors worn throughout training measured overpressure in pounds per square inch (psi). On day 7, some participants experienced moderate blast exposure (peak pressure ≥5 psi). On day 10, 3 days post-exposure, blood was collected and compared to baseline with RNA-sequencing to establish gene expression changes. Based on dysregulation data from RNA-sequencing, followed by top gene networks identified with Ingenuity Pathway Analysis, a subset of genes was validated (NanoString). Five gene networks were dysregulated; specifically, two highly significant networks: (1) Cell Death and Survival (score: 42), including 70 genes, with 50 downregulated and (2) Cell Structure, Function, and Metabolism (score: 41), including 69 genes, with 41 downregulated. Genes related to ubiquitination, including neuronal development and repair: UPF1, RNA Helicase and ATPase (UPF1) was upregulated while UPF3 Regulator of Nonsense Transcripts Homolog B (UPF3B) was downregulated. Genes related to inflammation were upregulated, including AKT serine/threonine kinase 1 (AKT1), a gene coordinating cellular recovery following TBIs. Moderate blast exposure induced significant gene expression changes including gene networks involved in (1) cell death and survival and (2) cellular development and function. The present findings may have implications for understanding blast exposure pathology and subsequent recovery efforts.

Sequelae of Blast Events in Iraq and Afghanistan War Veterans using the Salisbury Blast Interview: A CENC Study

Objective: To comprehensively characterize blast exposure across the lifespan and relationship to TBI.Participants: Post-deployment veterans and service members (N = 287).Design: Prospective cohort recruitment.Main Measures: Salisbury Blast Interview (SBI).Results: 94.4% of participants reported at least one blast event, 75% reported a pressure gradient during a blast event. Participants reported an average of 337.7 (SD = 984.0) blast events (range 0-4857), 64.8% occurring during combat. Across participants, 19.7% reported experiencing a traumatic brain injury (TBI) during a blast event. Subjective ratings of blast characteristics (wind, debris, ground shaking, pressure, temperature, sound) were significantly higher when TBI was experienced and significantly lower when behind cover. Pressure had the strongest association with resulting TBI (AUC = 0.751). Pressure rating of 3 had the best sensitivity (.54)/specificity (.87) with TBI. Logistic regression demonstrated pressure, temperature and distance were the best predictors of TBI, and pressure was the best predictor of primary blast TBI.Conclusion: Results demonstrate the ubiquitous nature of blast events and provide insight into blast characteristics most associated with resulting TBI (pressure, temperature, distance). The SBI provides comprehensive characterization of blast events across the lifespan including the environment, protective factors, blast characteristics and estimates of distance and munition.

Traumatic Brain Injuries: Unreported and Untreated in an Army Population

Introduction

In 2008, it was reported that 19.5% of service members previously deployed experienced a mild traumatic brain injury (mTBI). Fifty-seven percent of those did not seek medical care. It was suggested that concerns with seeking care involved confidentiality and career issues. Objective: This study addressed mTBI history, medical treatment history, and stigmas associated with mTBI/concussion.

Materials and Methods

An anonymous questionnaire was developed. Data collection occurred throughout March 2018 in conjunction with Brain Injury Awareness Month activities.

Results

All 5,174 volunteers were Army; 86% male; 87% were between 18 and 34 years old; 89% had &lt;14 years in the military; 35% had a combat deployment; and 10% reported having one or more mTBIs in their military careers. Of the Soldiers who reported a concussion, 52% sought medical care. Of those not seeking care, 64% reported they did not think the injury required care, followed by 18% fearing negative impact on their career. Twenty-eight percent who experienced an mTBI versus 11% who have not reported that there is a stigma associated with an mTBI.

Conclusions

Soldiers sometimes failed to report their suspected concussions and did not seek medical care. Educational efforts may increase reporting of and medical screening for potentially concussive events. Future research to determine the ramifications of unreported and untreated mTBIs/concussions is recommended.