Changes in personality after mild traumatic brain injury from primary blast vs. blunt forces

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.

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.

The prevalence, predictors, associated symptoms, and outcomes of social disinhibition following moderate-to-severe TBI: A scoping review of quantitative evidence

The present study aimed to map existing quantitative evidence of research related to the nature of social disinhibition following moderate-to-severe traumatic brain injury (TBI), with a specific focus on its prevalence, predictors, associated symptoms and outcomes in studies that met minimal methodological criteria. We conducted a scoping review of the literature following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) extension for Scoping Reviews (PRISMA-ScR). Seventeen peer-reviewed articles including 1440 participants met the inclusion criteria and were included in the qualitative synthesis. Results of the study indicate that social disinhibition is a common and significant consequence of moderate-to-severe TBI with its prevalence estimates ranging from 21% to 32%. Inappropriate sexual behavior appears to be more prevalent in men and younger survivors. Rule-breaking/perseverative errors in fluency tests are significantly associated with social disinhibition. The perceived burden of caregivers of people with TBI is a very common outcome. An interesting finding was an association between higher social disinhibition and higher emotional empathy levels. However, similarly to many potential predictors, this was only found in a single study and therefore requires further investigation. Some common methodological flaws are discussed, such as the use of non-probability sampling, lack of sample size justification or not including a control group. Due to the heterogeneity of measures used to assess social disinhibition in the reviewed articles, conducting a meta-analysis was not possible. In conclusion, social disinhibition is a significant consequence of moderate-to-severe TBI, as it impacts both the TBI survivor and their family/caregivers. The present study extends the scope of the prior overview by offering a clearer picture of social disinhibition after surviving moderate-to-severe TBI, as it focuses on studies with strong methodology and validated measures. It also assesses potential predictors other than executive dysfunction, such as demographics and injury characteristics.

Behavioral and Myelin-Related Abnormalities after Blast-Induced Mild Traumatic Brain Injury in Mice

In civilian and military settings, mild traumatic brain injury (mTBI) is a common consequence of impacts to the head, sudden blows to the body, and exposure to high-energy atmospheric shockwaves from blast. In some cases, mTBI from blast exposure results in long-term emotional and cognitive deficits and an elevated risk for certain neuropsychiatric diseases. Here, we tested the effects of mTBI on various forms of auditory-cued fear learning and other measures of cognition in male C57BL/6J mice after single or repeated blast exposure (blast TBI; bTBI). bTBI produced an abnormality in the temporal organization of cue-induced freezing behavior in a conditioned trace fear test. Spatial working memory, evaluated by the Y-maze task performance, was also deleteriously affected by bTBI. Reverse-transcription quantitative real-time polymerase chain reaction (RT-qPCR) analysis for glial markers indicated an alteration in the expression of myelin-related genes in the hippocampus and corpus callosum 1-8 weeks after bTBI. Immunohistochemical and ultrastructural analyses detected bTBI-related myelin and axonal damage in the hippocampus and corpus callosum. Together, these data suggest a possible link between blast-induced mTBI, myelin/axonal injury, and cognitive dysfunction.

Potential Concussive Event Narratives of Post-9/11 Combat Veterans: Chronic Effects of Neurotrauma Consortium Study

INTRODUCTION

Deployment-related mild traumatic brain injury (mTBI) affects a significant proportion of those who served in Post-9/11 combat operations. The prevalence of head injuries, including those that lead to mTBI, is often reported quantitatively. However, service member (SM) and Veteran firsthand accounts of their potential concussive events (PCEs) and mTBIs can serve as a rich resource for better understanding the nuances and context of these exposures.

MATERIALS AND METHODS

Post-9/11 SMs and Veterans with a history of combat deployment were recruited through the Chronic Effects of Neurotrauma Consortium's observational study of deployment-related mTBI. During a comprehensive assessment, participants completed the Virginia Commonwealth University retrospective Concussion Diagnostic Interview, a specialized validated interview measure which obtains detailed narratives of deployment-incurred blast and non-blast-related PCEs. Qualitative thematic analysis was used to identify and code recurring themes within the narratives.

RESULTS

Among the sample of 106 SMs and Veterans, deployment-related mTBI was highly prevalent (67.0%). Over half (50.9%) of the participants identified a blast as the cause of their worst PCE, frequently with accompanying themes of self-reported acute neurological symptoms, intense physical blast forces, and tertiary head impact. Exposure to blast at close range, such as driving directly over an improvised explosive device, occurred in 24.7% of all blast-related narratives and in 59.3% of narratives where blast was identified as causing the worst PCE. Themes of potentially preventable head impacts experienced during noncombat circumstances were also frequent, accounting for 35% of all non-blast-related head injuries in the sample.

CONCLUSIONS

Prevalence of deployment-related close-range blast exposure, non-blast impact PCEs, and mTBIs among this Post-9/11 combatant sample was substantial, and in many cases potentially preventable. The use of detailed semi-structured interviews may help health care providers and policymakers to better understand the context and circumstances of deployment-related PCEs and mTBIs.

Nonmissile penetrating head injury with a wooden table leg: An illustrative case

Penetrating head injuries are relatively uncommon and require a unique approach. This report highlights a previously unreported mechanism of injury with a table leg and the steps required to evaluate and promptly treat the patient.

Characteristics and Impact of U.S. Military Blast-Related Mild Traumatic Brain Injury: A Systematic Review

As a result of armed conflict, head trauma from exposure to blasts is an increasing critical health issue, particularly among military service members. Whilst numerous studies examined the burden of blast-related brain injuries on service members', few systematic reviews have been published. This work provides a comprehensive summary of the evidence on blast-related mild traumatic brain injury (mTBI) burden in active U.S. military service members and inactive Veterans, describing characteristics and outcomes. Records published up to April 2017 were identified through a search of PubMed, Web of Science, Scopus, Ovid MEDLINE, and Cochrane Library. Records-based and original research reporting on U.S. military service members and Veterans with mild blast TBI were included. Data on subject characteristics, exposure, diagnostic criterion, and outcomes were extracted from included studies using a standardized extraction form and were presented narratively. Of the 2,290 references identified by the search, 106 studies with a total of 37,515 participants met inclusion criteria for blast-related mTBI. All but nine studies were based out of military or Veteran medical facilities. Unsurprisingly, men were over-represented (75–100%). The criteria used to define blast-related mTBI were consistent; however, the methodology used to ascertain whether individuals met those criteria for diagnosis were inconsistent. The diagnosis, most prevalent among the Army, heavily relied on self-reported histories. Commonly reported adverse outcomes included hearing disturbances and headaches. The most frequently associated comorbidities were post-traumatic stress disorder, depression, anxiety, sleep disorders, attention disorders, and cognitive disorders. The primary objective of this review was to provide a summary of descriptive data on blast-related mTBI in a U.S. military population. Low standardization of the methods for reaching diagnosis and problems in the study reporting emphasize the importance to collect high-quality data to fill knowledge gaps pertaining to blast-related mTBI.

Outcomes Associated With Blast Versus Nonblast-Related Traumatic Brain Injury in US Military Service Members and Veterans: A Systematic Review

OBJECTIVES

To systematically review the literature on comparative clinical and functional outcomes following blast-related versus nonblast-related traumatic brain injury (TBI) among US service members and Veterans.

DESIGN

MEDLINE search (January 2001 to June 2016) supplemented with hand search of reference lists and input from peer reviewers.

RESULTS

Thirty-one studies (in 33 articles) reported on health outcomes; only 2 were rated low risk of bias. There was variation in outcomes reported and methods of assessment. Blast and nonblast TBI groups had similar rates of depression, sleep disorders, alcohol misuse, vision loss, vestibular dysfunction, and functional status. Comparative outcomes were inconsistent with regard to posttraumatic stress disorder diagnosis or symptoms, headache, hearing loss, and neurocognitive function. Mortality, burn, limb loss, and quality of life were each reported in few studies, most with small sample sizes. Only 4 studies reported outcomes by blast injury mechanism.

CONCLUSIONS

Most clinical and functional outcomes appeared comparable in military service members and Veterans with TBI, regardless of blast exposure. Inconsistent findings and limited outcomes reporting indicate that more research is needed to determine whether there is a distinct pattern of impairments and comorbidities associated with blast-related TBI.

Single cell molecular alterations reveal target cells and pathways of concussive brain injury

The complex neuropathology of traumatic brain injury (TBI) is difficult to dissect, given the convoluted cytoarchitecture of affected brain regions such as the hippocampus. Hippocampal dysfunction during TBI results in cognitive decline that may escalate to other neurological disorders, the molecular basis of which is hidden in the genomic programs of individual cells. Using the unbiased single cell sequencing method Drop-seq, we report that concussive TBI affects previously undefined cell populations, in addition to classical hippocampal cell types. TBI also impacts cell type-specific genes and pathways and alters gene co-expression across cell types, suggesting hidden pathogenic mechanisms and therapeutic target pathways. Modulating the thyroid hormone pathway as informed by the T4 transporter transthyretin Ttr mitigates TBI-associated genomic and behavioral abnormalities. Thus, single cell genomics provides unique information about how TBI impacts diverse hippocampal cell types, adding new insights into the pathogenic pathways amenable to therapeutics in TBI and related disorders.

Personality Across the Life Span

Trait stability and maturation are fundamental principles of contemporary personality psychology and have been shown to hold across many cultures. However, it has proven difficult to move beyond these general findings to a detailed account of trait development. There are pervasive and unexplained inconsistencies across studies that may be due to ( a) insufficient attention to measurement error, ( b) subtle but age-sensitive differences in alternative measures of the same trait, or ( c) different perspectives reflected in self-reports and observer ratings. Multiscale, multimethod-and ideally multinational-studies are needed. Several hypotheses have been proposed to account for trait stability and change, but supporting evidence is currently weak or indirect; trait development is a fertile if sometimes frustrating field for theory and research. Beyond traits, there are approaches to personality development that are of interest to students of adult development, and these may be fruitfully addressed from a trait perspective.

What is the Relationship of Traumatic Brain Injury to Dementia?

There is a long history linking traumatic brain injury (TBI) with the development of dementia. Despite significant reservations, such as recall bias or concluding causality for TBI, a summary of recent research points to several conclusions on the TBI-dementia relationship. 1) Increasing severity of a single moderate-to-severe TBI increases the risk of subsequent Alzheimer's disease (AD), the most common type of dementia. 2) Repetitive, often subconcussive, mild TBIs increases the risk for chronic traumatic encephalopathy (CTE), a degenerative neuropathology. 3) TBI may be a risk factor for other neurodegenerative disorders that can be associated with dementia. 4) TBI appears to lower the age of onset of TBI-related neurocognitive syndromes, potentially adding "TBI cognitive-behavioral features". The literature further indicates several specific risk factors for TBI-associated dementia: 5) any blast or blunt physical force to the head as long as there is violent head displacement; 6) decreased cognitive and/or neuronal reserve and the related variable of older age at TBI; and 7) the presence of apolipoprotein E ɛ4 alleles, a genetic risk factor for AD. Finally, there are neuropathological features relating TBI with neurocognitive syndromes: 8) acute TBI results in amyloid pathology and other neurodegenerative proteinopathies; 9) CTE shares features with neurodegenerative dementias; and 10) TBI results in white matter tract and neural network disruptions. Although further research is needed, these ten findings suggest that dose-dependent effects of violent head displacement in vulnerable brains predispose to dementia; among several potential mechanisms is the propagation of abnormal proteins along damaged white matter networks.

The many wounds of war: The association of service-related and clinical characteristics with problems with the law in Iraq and Afghanistan veterans

Previous research has demonstrated that veterans with posttraumatic stress disorder (PTSD) are at higher risk for aggression, hostility, and anger, potentially leading to problems with the law or disciplinary action while in the military. There have been calls for increased consideration of the unique aspects of the judicial system in legal matters with veterans involved. The bulk of the research so far has considered the link between PTSD, traumatic brain injury (TBI), and combat exposure, but little is known about the potential role of chronic pain and Military Sexual Trauma (MST) in a veteran's experience of anger, aggression, and discipline while in the military and legal concerns. The present study used retrospective cross-sectional health screening data in a sample of 1250 Iraq and Afghanistan veterans to examine the associations of demographic, service-related, and clinical characteristics with self-reported legal problems. A total of 440 veterans (34.6%) endorsed having experienced some type of problems with the law. Independent logistic regression analyses demonstrated that those who screened positive for PTSD, MST, TBI, and clinical levels of pain were more likely to report legal problems; only the associations with positive PTSD (p=0.001) and MST (p=0.007) screens remained significant in multivariate regression analyses. The findings underscore the need for a thorough psychological evaluation when veterans are involved in the legal system with a special emphasis on factors prevalent to Iraq and Afghanistan veterans.

The Temporal Pattern of Changes in Serum Biomarker Levels Reveals Complex and Dynamically Changing Pathologies after Exposure to a Single Low-Intensity Blast in Mice

Time-dependent changes in blood-based protein biomarkers can help identify the ­pathological processes in blast-induced traumatic brain injury (bTBI), assess injury severity, and monitor disease progression. We obtained blood from control and injured mice (exposed to a single, low-intensity blast) at 2-h, 1-day, 1–week, and 1-month post-injury. We then determined the serum levels of biomarkers related to metabolism (4-HNE, HIF-1α, ceruloplasmin), vascular function (AQP1, AQP4, VEGF, vWF, Flk-1), inflammation (OPN, CINC1, fibrinogen, MIP-1a, OX-44, p38, MMP-8, MCP-1 CCR5, CRP, galectin-1), cell adhesion and the extracellular matrix (integrin α6, TIMP1, TIMP4, Ncad, connexin-43), and axonal (NF-H, Tau), neuronal (NSE, CK-BB) and glial damage (GFAP, S100β, MBP) at various post-injury time points. Our findings indicate that the exposure to a single, low-intensity blast results in metabolic and vascular changes, altered cell adhesion, and axonal and neuronal injury in the mouse model of bTBI. Interestingly, serum levels of several inflammatory and astroglial markers were either unchanged or elevated only during the acute and subacute phases of injury. Conversely, serum levels of the majority of biomarkers related to metabolic and vascular functions, cell adhesion, as well as neuronal and axonal damage remained elevated at the termination of the experiment (1 month), indicating long-term systemic and cerebral alterations due to blast. Our findings show that the exposure to a single, low-intensity blast induces complex pathological processes with distinct temporal profiles. Hence, monitoring serum biomarker levels at various post-injury time points may provide enhanced diagnostics in blast-related neurological and multi-system deficits.

No Significant Acute and Subacute Differences between Blast and Blunt Concussions across Multiple Neurocognitive Measures and Symptoms in Deployed Soldiers

Seventy-one deployed U.S. Army soldiers who presented for concussion care due to either blast or blunt mechanisms within 72 h of injury were assessed using the Military Acute Concussion Evaluation, the Automated Neuropsychological Assessment Metrics (ANAM), traditional neuropsychological tests, and health status questionnaires. Follow-up ANAM testing was performed 10 d after initial testing (±5 d). Twenty-one soldiers were excluded: two for poor effort and 19 who had combined blast/blunt injuries. Of the remaining 50 male participants, 34 had blast injuries and 16 had blunt injuries. There were no statistically significant differences between blast injury and blunt injury participants in demographic, physical, or psychological health factors, concussive symptoms, or automated and traditional neurocognitive testing scores within 72 h post-injury. In addition, follow-up ANAM scores up to 15 d post-injury were not significantly different (available on 21 blast-injured and 13 blunt-injured subjects). Pre-injury baseline ANAM scores were compared where available, and revealed no statistically significant differences between 22 blast injury and eight blunt injury participants. These findings suggest there are no significant differences between mechanisms of injury during both the acute and subacute periods in neurobehavioral concussion sequelae while deployed in a combat environment. The current study supports the use of sports/mechanical concussion models for early concussion management in the deployed setting and exploration of variability in potential long-term outcomes.

Functional neuroimaging of traumatic brain injury: advances and clinical utility

Functional deficits due to traumatic brain injury (TBI) can have significant and enduring consequences upon patients' life quality and expectancy. Although functional neuroimaging is essential for understanding TBI pathophysiology, an insufficient amount of effort has been dedicated to the task of translating functional neuroimaging findings into information with clinical utility. The purpose of this review is to summarize the use of functional neuroimaging techniques - especially functional magnetic resonance imaging, diffusion tensor imaging, positron emission tomography, magnetic resonance spectroscopy, and electroencephalography - for advancing current knowledge of TBI-related brain dysfunction and for improving the rehabilitation of TBI patients. We focus on seven core areas of functional deficits, namely consciousness, motor function, attention, memory, higher cognition, personality, and affect, and, for each of these, we summarize recent findings from neuroimaging studies which have provided substantial insight into brain function changes due to TBI. Recommendations are also provided to aid in setting the direction of future neuroimaging research and for understanding brain function changes after TBI.

Functional status after blast-plus-impact complex concussive traumatic brain injury in evacuated United States military personnel

Fundamental questions remain unanswered about the longitudinal impact of blast-plus-impact complex traumatic brain injuries (TBI) from wars in Iraq and Afghanistan. This prospective, observational study investigated measures of clinical outcome in US military personnel evacuated to Landstuhl Regional Medical Center (LRMC) in Germany after such "blast-plus" concussive TBIs. Glasgow Outcome Scale-Extended assessments completed 6-12 months after injury indicated a moderate overall disability in 41/47 (87%) blast-plus TBI subjects and a substantial but smaller number (11/18, 61%, p=0.018) of demographically similar US military controls without TBI evacuated for other medical reasons. Cognitive function assessed with a neuropsychological test battery was not different between blast-plus TBI subjects and controls; performance of both groups was generally in the normal range. No subject was found to have focal neurological deficits. However, 29/47 (57%) of blast-plus subjects with TBI met all criteria for post-traumatic stress disorder (PTSD) versus 5/18 (28%) of controls (p=0.014). PTSD was highly associated with overall disability; 31/34 patients with PTSD versus 19/31 patients who did not meet full PTSD criteria had moderate to severe disability (p=0.0003). Symptoms of depression were also more severe in the TBI group (p=0.05), and highly correlated with PTSD severity (r=0.86, p<0.0001). Thus, in summary, high rates of PTSD and depression but not cognitive impairment or focal neurological deficits were observed 6-12 months after concussive blast-plus-impact complex TBI. Overall disability was substantially greater than typically reported in civilian non-blast concussive ("mild") patients with TBI, even with polytrauma. The relationship between these clinical outcomes and specific blast-related aspects of brain injuries versus other combat-related factors remains unknown.

Blast-related traumatic brain injury

A bomb blast may cause the full severity range of traumatic brain injury (TBI), from mild concussion to severe, penetrating injury. The pathophysiology of blast-related TBI is distinctive, with injury magnitude dependent on several factors, including blast energy and distance from the blast epicentre. The prevalence of blast-related mild TBI in modern war zones has varied widely, but detection is optimised by battlefield assessment of concussion and follow-up screening of all personnel with potential concussive events. There is substantial overlap between post-concussive syndrome and post-traumatic stress disorder, and blast-related mild TBI seems to increase the risk of post-traumatic stress disorder. Post-concussive syndrome, post-traumatic stress disorder, and chronic pain are a clinical triad in this patient group. Persistent impairment after blast-related mild TBI might be largely attributable to psychological factors, although a causative link between repeated mild TBIs caused by blasts and chronic traumatic encephalopathy has not been established. The application of advanced neuroimaging and the identification of specific molecular biomarkers in serum for diagnosis and prognosis are rapidly advancing, and might help to further categorise these injuries.