Neuropsychological outcomes of U.S. Veterans with report of remote blast-related concussion and current psychopathology

Disentangling effects of remote mild traumatic brain injury characteristics and posttraumatic stress on processing speed and executive function in veterans

Mild traumatic brain injury (mTBI) and posttraumatic stress are prevalent in military service members and share objective and subjective cognitive symptoms, complicating recovery. We investigated the effects of remote mTBI characteristics and current posttraumatic stress symptoms on neuropsychological performance in 152 veterans with a history of remote mTBI and current cognitive concerns. Participants completed clinical neuropsychological evaluations within a Veterans Affairs Level-II TBI/Polytrauma outpatient clinic (i.e. tertiary trauma care center for US military veterans outside of a research or teaching hospital setting). Archival data analysis of mTBI injury characteristics, clinical diagnoses, scores on the Posttraumatic Stress Disorder Checklist-Military Version (PCL-M) and performance on tests of processing speed, attention and executive function was conducted. Hierarchical linear regression demonstrated that elevated PCL-M scores were associated with slower performance on trail making test (TMT) Parts A and B (p < .016). PCL-M symptoms moderated the effect of alteration of consciousness (AOC) on TMT performance, with endorsement of AOC associated with better performance, but only when PCL-M scores were high (p < .005). Follow-up mediation analyses demonstrated that PCL-M score fully mediated the relationship between AOC and TMT-A performance and partially mediated the relationship between AOC and TMT-B performance. Post-hoc analyses meant to separate the impact of processing speed on TMT-B were all non-significant. Remote mTBI characteristics, specifically AOC, were not associated with decrements in cognitive performance. Posttraumatic symptoms were associated with worse processing speed, suggesting that psychological distress and psychopathology are contributing factors in understanding and treating persistent cognitive distress following remote mTBI.

Disentangling subjective symptom complaints and objective cognitive performance in veterans: Impact of posttraumatic stress disorder and lifetime traumatic brain injury burden

Self-reported histories of mild traumatic brain injury (mTBI) and posttraumatic stress disorder (PTSD) symptoms are prevalent among post-9/11 veterans. Both are associated with subjective and often overlapping symptom complaints, but variably with objective neuropsychological test performances. These outcomes are seldom explored in relation to lifetime mTBI burden. This cross-sectional study examined associations of PTSD and lifetime mTBI with subjective (persistent symptoms after concussion and cognitive complaints) and objective (performances across five cognitive domains) measures among 46 veterans. Within this sample, 20 veterans had Clinician-Administered PTSD Scale for DSM-5 (CAPS-5) confirmed PTSD (PTSD+), whereas 26 demographically-similar participants did not meet criteria (PTSD-). The Boston Assessment of Traumatic Brain Injury-Lifetime (BAT-L) yielded total mTBI scores ranging from 0 to 8. Regressions showed PTSD was associated with increased subjective symptoms/cognitive complaints, along with reduced verbal fluency, visuospatial memory, and processing speed performances. Lifetime mTBI burden was associated with subjective symptoms, but not with objective cognitive test performance, after controlling for PTSD. No significant interactions were observed. Exploratory correlations suggested that all PTSD symptom clusters were generally associated with the subjective and objective measures. However, fewer significant associations emerged within the PTSD+/- groups separately, with each group yielding somewhat different patterns of relationships. PTSD and increasing mTBI burden are consistently associated with negative subjective symptoms, including cognitive complaints. Each condition likely explains some degree of unique variance in symptom reporting. PTSD is associated with poorer objective cognition on some tasks, including processing speed, executive functioning, and learning/memory. Implications are explored.

Inefficient Attentional Control Explains Verbal-Memory Deficits Among Military Veterans With Posttraumatic Reexperiencing Symptoms

Among individuals with posttraumatic stress disorder (PTSD), verbal learning and memory are areas of weakness compared with other cognitive domains (e.g., visuospatial memory). In this study, previously deployed military veterans completed clinical assessments of word memory and vocabulary (n = 243) and a laboratory task measuring encoding, free recall, repetition priming, and recognition of words (n = 147). Impaired verbal memory was selectively related to reexperiencing symptoms of PTSD but was not associated with other symptom groupings or blast-induced traumatic brain injury. Implicit priming of response times following word repetition was also unrelated to clinical symptoms. Instead, slowed response times during encoding explained associations between reexperiencing and memory performance. These findings are consistent with alterations in attentional control explaining PTSD-related verbal-memory deficits. Such findings have implications for understanding trauma-focused psychotherapy and recovery, which may depend on efficient attentional processing of words to alter posttraumatic reexperiencing symptoms.

Customizing TMS Applications in Traumatic Brain Injury Using Neuroimaging

Optimizing transcranial magnetic stimulation (TMS) treatments in traumatic brain injury (TBI) and co-occurring conditions may benefit from neuroimaging-based customization.

PARTICIPANTS

Our total sample (N = 97) included 58 individuals with TBI (49 mild, 8 moderate, and 1 severe in a state of disordered consciousness), of which 24 had co-occurring conditions (depression in 14 and alcohol use disorder in 10). Of those without TBI, 6 individuals had alcohol use disorder and 33 were healthy controls. Of our total sample, 54 were veterans and 43 were civilians.

DESIGN

Proof-of-concept study incorporating data from 5 analyses/studies that used multimodal approaches to integrate neuroimaging with TMS.

MAIN MEASURES

Multimodal neuroimaging methods including structural magnetic resonance imaging (MRI), MRI-guided TMS navigation, functional MRI, diffusion MRI, and TMS-induced electric fields. Outcomes included symptom scales, neuropsychological tests, and physiological measures.

RESULTS

It is feasible to use multimodal neuroimaging data to customize TMS targets and understand brain-based changes in targeted networks among people with TBI.

CONCLUSIONS

TBI is an anatomically heterogeneous disorder. Preliminary evidence from the 5 studies suggests that using multimodal neuroimaging approaches to customize TMS treatment is feasible. To test whether this will lead to increased clinical efficacy, studies that integrate neuroimaging and TMS targeting data with outcomes are needed.

Effect of blast-related mTBI on the working memory system: a resting state fMRI study

Reduced working memory is frequently reported by Veterans with a history of blast-related mild traumatic brain injury (mTBI), but can be difficult to quantify on neuropsychological measures. This study aimed to improve our understanding of the impact of blast-related mTBI on the working memory system by using resting state functional magnetic resonance imaging (fMRI) to explore differences in functional connectivity between OEF/OIF/OND Veterans with and without a history of mTBI. Participants were twenty-four Veterans with a history of blast-related mTBI and 17 Veterans who were deployed but had no lifetime history of TBI. Working memory ability was evaluated with the Auditory Consonants Trigrams (ACT) task. Resting state fMRI was used to evaluate intrinsic functional connectivity from frontal seed regions that are known components of the working memory network. No significant group differences were found on the ACT, but the imaging analyses revealed widespread hyper-connectivity from the frontal seed regions in the Veterans with a history of mTBI relative to the deployed control group. Further, within the mTBI group, but not the control group, better performance on the ACT was associated with increased functional connectivity to multiple brain regions, including cerebellar components of the working memory network. These results were present after controlling for age, PTSD symptoms, and estimated premorbid IQ, and suggest that long-term alterations in the functional connectivity of the working memory network following blast-related mTBI may reflect a compensatory change that contributes to intact performance on an objective measure of working memory.

Influence of blast exposure on cognitive functioning in combat veterans

OBJECTIVE

We evaluated the contribution of blast-pressure severity to cognitive functioning beyond posttraumatic stress disorder (PTSD) severity and traumatic brain injury (TBI).

METHOD

Post-9/11 veterans (N = 254, 86.22% male) completed the Wechsler Adult Intelligence Scale (WAIS-IV) and Trail Making Test (TMT). The Clinician-Administered PTSD Scale (CAPS-5), Mid-Atlantic MIRECC Assessment of TBI, and the Salisbury Blast Interview evaluated PTSD diagnosis/severity, deployment TBI history/severity, and blast-exposure history/severity, respectively.

RESULTS

Veterans with mild deployment TBI had overall significantly lower T scores on the WAIS-IV Verbal Comprehension Index (d = .13), Working Memory Index (d = .30), and Processing Speed Index (d = .25); the Trail Making Test A (TMT-A; d = .50); and the Trail Making Test B (TMT-B; d = .37). Mild deployment TBI was significantly associated with TMT-A (ΔR² = .05, p < .001) and TMT-B (ΔR² = .03, p = .001) performance. Blast-pressure severity moderated the association between mild deployment TBI and TMT-A (ΔR² = .02, p = .039, B = -2.01).

CONCLUSION

Blast-pressure severity exacerbated the effects of mild TBI on a simple attention task, such that participants with TBI had gradual decrements in attention as blast severity increased. Veterans who incur a TBI and are exposed to blasts during deployment may experience persisting difficulties with cognitive functioning as a result of alterations in basic attention abilities. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Impact of Pre-Existing Migraine and Other Co-Morbid or Co-Occurring Conditions on Presentation and Clinical Course Following Deployment-Related Concussion

OBJECTIVE

To describe the clinical presentation and early clinical course of a sample of deployed U.S. military service members following concussion, underscoring the impact of pre-existing migraine and other co-occurring conditions. It is important to obtain a comprehensive clinical history to identify evidence of underlying migraine and other health conditions which may contribute to an individual's presenting symptoms influencing early management and outcomes following concussion. Early outcome measures assessed include headache treatment response and fitness for return to duty.

BACKGROUND

Acute concussion is reported to result in an array of somatic, cognitive, and behavioral symptoms. It is well established that these symptoms are not specific for concussion and may result from exacerbation of pre-existing or underlying medical conditions and factors. Although most symptoms attributable to concussion resolve within days to weeks, there is evidence that persistent symptoms beyond that specific recovery time may be attributable to factors other than concussion. Military populations are at risk for a number of recognized co-morbid and co-occurring conditions, as well as special situational and psychosocial factors which may influence symptoms and clinical course following concussion. In addition, combat-related concussion frequently occurs in the setting of a blast or military vehicle accidents thus causing concurrent injuries where musculoskeletal injuries may contribute to the clinical presentation. The resultant acute stress reaction, secondary to the traumatic experience associated with concussion, may also cause or aggravate underlying psychological co-morbidities that may influence presenting symptoms. Prior studies identified co-morbidities associated with chronic post-concussive syndrome, which we find are also present during the early phase following deployment-related concussion, thereby influencing presentation and impacting recovery. This retrospective chart review was intended to demonstrate the presence and potential impact of co-morbid and co-occurring conditions contributing to symptoms following concussion, especially migraine due to its high prevalence among post-traumatic headaches.

METHODS

Retrospective chart review was performed by the treating neurologist of 40 service members following concussion in the deployed environment. Clinical symptoms and co-morbid and co-occurring conditions including evidence of pre-existing migraine identified during comprehensive neurologic evaluations were collected. Both pre-deployment/pre-traumatic and post-traumatic headache features supporting migraine and early instituted headache management and treatment response are described. Rates of return to duty in this sample were also tabulated.

RESULTS

Headaches were the most frequently reported acute symptom following concussion in this deployed service member population (38/40 patients [98%]), followed by insomnia, tinnitus, impaired concentration, nausea, dizziness, anxiety, impaired balance, depression, and hearing loss. Co-occurring acute injuries, acute stress reaction, and recent onset medication overuse were the most frequent co-occurring conditions identified by the treating neurologist as potentially contributing to the service member's presentation. Chronic co-morbidities identified included chronic headache, anxiety/depression, insomnia, and post-traumatic stress disorder. Service members with 3 or more identified co-morbidities or co-occurring conditions were more likely to require evacuation from theater. Pre-deployment headaches were reported by 25/40 [63%] service members, with 5/40 [12.5%] reporting known prior personal history of migraine. Of those reporting pre-deployment headaches, 21/25 [84%] described migraine features and/or triggers, though most [(15/25) 60%] reported as infrequent. Daily post-traumatic headaches were frequent (26/38 [68%]) and associated with typical migraine features and/or triggers. Of those treated with triptans (16/40 patient [42%]), most (12/16 patient [75%]) showed positive treatment response.

CONCLUSIONS

Concussion in the deployed settings does not occur in isolation, with co-morbid and co-occurring conditions being common. Presence of multiple co-morbidities appears to influence clinical course and overall recovery. Post-traumatic headaches are often phenotypically fully consistent with migraine, and appear related to pre-existing migraine if supported by detailed pre-deployment headache history suggesting same. Careful and comprehensive history taking and evaluation is invaluable in identifying associated conditions including migraine, potentially helping clinicians with more accurate symptom attribution, diagnoses, and improved clinical management following acute concussion.

Blast concussion and posttraumatic stress as predictors of postcombat neuropsychological functioning in OEF/OIF/OND veterans

OBJECTIVES

Many combat veterans exhibit cognitive limitations of uncertain origin. In this study, we examined factors that predict cognitive functioning by considering effects of blast-related concussion (BRC), non-blast-related concussion (NBRC), and posttraumatic stress disorder (PTSD) symptoms. Analyses specifically tested whether (a) BRC and NBRC were distinct in their prediction of cognitive performance; (b) a dose-response relationship existed between recurrent concussion (BRC and NBRC) and cognitive impairment; and (c) PTSD symptoms mediated the relationship between BRC and cognitive performance.

METHOD

Two hundred eighty veterans with combat zone deployment histories completed semistructured clinical interviews to define BRC and NBRC histories, current and past mental health disorders, and dimensional ratings of PTSD symptomatology. Participants were also administered a number of neuropsychological measures to appraise cognitive functioning.

RESULTS

A structural equation model (SEM) suggested that BRC and NBRC were not distinct in their prediction of cognitive performance, and there was no evidence that recurrent concussion (blast or nonblast) was directly associated with cognitive performance. BRC was significantly associated with PTSD symptoms (r = .24), PTSD symptoms were significantly associated with cognitive performance in the SEM (r = -.27), and PTSD symptoms significantly mediated the link between BRC and cognitive performance (p = .03).

CONCLUSIONS

These results suggest that concussion history fails to directly contribute to cognitive performance, regardless of mechanism (blast or nonblast) and recurrence. BRC is nonetheless unique in its contribution to PTSD and PTSD-related cognitive deficits. Results support interventions specific to PTSD management in the interest of promoting neuropsychological functioning among war veterans. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Traumatic Brain Injury and Posttraumatic Stress Disorder: Comorbid Consequences of War

Scientific literature is reviewed supporting a “consequence of war syndrome (CWS)” in Operation Enduring Freedom/Operation Iraqi Freedom/Operation New Dawn soldiers. CWS constituents include chronic pain and insomnia, other physical complaints, posttraumatic stress disorder (PTSD), anxiety, depression, and neuropsychological deficits. The foundation of CWS lies with the chronic stressors inherent to deployment and the cascade of biological events mediated and maintained by hypothalamic-pituitary-adrenal (HPA) axis dysregulation. Such dysregulation is modified by the individual’s specific experiences at war, difficulty reintegrating to post-deployment life, and the onset or exacerbation of the chronic and comorbid physical, emotional, and cognitive disorders. The circuit network between the prefrontal cortex (PFC), amygdala, and hippocampus is particularly sensitive to the consequences of war. The review’s specific conclusions are as follows: HPA axis dysregulation contributes to the chronic insomnia and hyperarousal seen in soldiers. There is considerable symptom overlap between PTSD and blast-related head injury, and it is difficult to determine the relative contributions of the two disorders to abnormal imaging studies. In some cases, traumatic brain injury (TBI) may directly precipitate PTSD symptoms. While not intuitive, the relationship between TBI and postconcussion syndrome appears indirect and mediated through PTSD. Blast-related or conventional head injury may have little long-term impact on neuropsychological functioning; contrarily, PTSD particularly accounts for current cognitive deficits. The psychological experience of CWS includes a “war-within” where soldiers continue to battle an internalized enemy. Successful treatment of CWS entails transdisciplinary care that addresses each of the constituent disorders.

The impact of PTSD and mTBI on the relationship between subjective and objective cognitive deficits in combat-exposed veterans

OBJECTIVE

Cognitive complaints, such as attentional or memory concerns, are commonly reported by veterans diagnosed with posttraumatic stress disorder (PTSD) or a history of mild traumatic brain injury (mTBI). The degree to which those complaints actually map onto measurable cognitive deficits is unclear and is likely complicated by the severity of trauma-related sequelae. In the present study we sought to characterize the degree to which PTSD symptoms and mTBI accounted for the relationship of subjective cognitive complaints to objective cognitive performance, with the goal of facilitating the accurate assessment of trauma-exposed veterans complaining of cognitive decline.

METHOD

A sample of 203 U.S. military veterans previously deployed to Iraq and/or Afghanistan were assessed for PTSD severity, history of blast and impact mTBI, objective cognitive function, and subjective cognitive complaints. Separate mediation analyses were conducted to explore the degree that PTSD severity, blast mTBI severity, and impact mTBI severity influenced the association between subjective cognitive complaints and objective cognitive performance. Models reflecting significant mediation were followed by post hoc moderated mediation analyses.

RESULTS

Subjective cognitive complaints and objective cognitive performance were significantly associated (β = -6.49, SE = 2.85, p = .03), but this relationship was mediated by PTSD severity (β= -2.95, SE = 2.86, p = .30). PTSD mediation was not moderated by either blast or impact mTBI.

CONCLUSION

The present results delineate the prominent impact of PTSD symptoms, relative to blast and impact mTBI, on cognition following combat. These findings highlight the importance of assessing for trauma-related psychopathology in those seeking neuropsychological assessment or rehabilitative care for cognitive complaints. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Impact of PTSD on post-concussive symptoms, neuropsychological functioning, and pain in post-9/11 veterans with mild traumatic brain injury

Prior work suggested that post-traumatic stress disorder (PTSD) worsens post-concussive symptoms (PCS), neuropsychological functioning, and pain-related outcomes in post-9/11 veterans. However, the impact of PTSD in the context of mild traumatic brain injury (mTBI) is not entirely clear. We evaluated possible differences among veterans with deployment-related mTBI with and without PTSD, and a comparison group. We hypothesized that veterans with comorbid mTBI and PTSD would report more PCS, perform worse on neuropsychological tasks, and report greater pain intensity and maladaptive pain coping relative to those without PTSD. Ninety (15 female, 75 male) post-9/11 veterans completed measures of psychiatric functioning, PCS, deployment-related mTBI, pain intensity, pain coping, and a brief neuropsychological evaluation. Veterans with comorbid mTBI and PTSD reported significantly higher PCS across domains, and greater pain intensity and maladaptive coping. They also performed more poorly on measures of recall, but not on measures of attention, encoding, or executive functioning. Findings suggest that PTSD results in greater PCS in the context of mTBI, and is associated with greater pain catastrophizing, worse recall, greater pain intensity, and greater illness-focused coping than in mTBI alone. PCS symptoms, recall, and pain coping may be of clinical importance for post-9/11 veterans with the "polytrauma triad."

Blast-induced "PTSD": Evidence from an animal model

A striking observation among veterans returning from the recent conflicts in Iraq and Afghanistan has been the co-occurrence of blast-related mild traumatic brain injury (mTBI) and post-traumatic stress disorder (PTSD). PTSD and mTBI might coexist due to additive effects of independent psychological and physical traumas experienced in a war zone. Alternatively blast injury might induce PTSD-related traits or damage brain structures that mediate responses to psychological stressors, increasing the likelihood that PTSD will develop following a subsequent psychological stressor. Rats exposed to repetitive low-level blasts consisting of three 74.5 kPa exposures delivered once daily for three consecutive days develop a variety of anxiety and PTSD-related behavioral traits that are present for at least 9 months after blast exposure. A single predator scent challenge delivered 8 months after the last blast exposure induces additional anxiety-related changes that are still present 45 days later. Because the blast injuries occur under general anesthesia, it appears that blast exposure in the absence of a psychological stressor can induce chronic PTSD-related traits. The reaction to a predator scent challenge delivered many months after blast exposure suggests that blast exposure in addition sensitizes the brain to react abnormally to subsequent psychological stressors. The development of PTSD-related behavioral traits in the absence of a psychological stressor suggests the existence of blast-induced "PTSD". Findings that PTSD-related behavioral traits can be reversed by BCI-838, a group II metabotropic glutamate receptor antagonist offers insight into pathogenesis and possible treatment options for blast-related brain injury. This article is part of the Special Issue entitled "Novel Treatments for Traumatic Brain Injury".

Effects of Mild Blast Traumatic Brain Injury on Cognitive- and Addiction-Related Behaviors

Traumatic brain injury (TBI) commonly results in cognitive and psychiatric problems. Cognitive impairments occur in approximately 30% of patients suffering from mild TBI (mTBI), and correlational evidence from clinical studies indicates that substance abuse may be increased following mTBI. However, understanding the lasting cognitive and psychiatric problems stemming from mTBI is difficult in clinical settings where pre-injury assessment may not be possible or accurate. Therefore, we used a previously characterized blast model of mTBI (bTBI) to examine cognitive- and addiction-related outcomes. We previously demonstrated that this model leads to bilateral damage of the medial prefrontal cortex (mPFC), a region critical for cognitive function and addiction. Rats were exposed to bTBI and tested in operant learning tasks several weeks after injury. bTBI rats made more errors during acquisition of a cue discrimination task compared to sham treated rats. Surprisingly, we observed no differences between groups in set shifting and delayed matching to sample, tasks known to require the mPFC. Separate rats performed cocaine self-administration. No group differences were found in intake or extinction, and only subtle differences were observed in drug-primed reinstatement 3-4 months after injury. These findings indicate that bTBI impairs acquisition of a visual discrimination task and that bTBI does not significantly increase the ability of cocaine exposure to trigger drug seeking.

Retrospective and Prospective Memory Among OEF/OIF/OND Veterans With a Self-Reported History of Blast-Related mTBI

OBJECTIVES

To evaluate prospective and retrospective memory abilities in Operation Enduring Freedom (OEF), Operation Iraqi Freedom (OIF), and Operation New Dawn (OND) Veterans with and without a self-reported history of blast-related mild traumatic brain injury (mTBI).

METHODS

Sixty-one OEF/OIF/OND Veterans, including Veterans with a self-reported history of blast-related mTBI (mTBI group; n=42) and Veterans without a self-reported history of TBI (control group; n=19) completed the Memory for Intentions Test, a measure of prospective memory (PM), and two measures of retrospective memory (RM), the California Verbal Learning Test-II and the Brief Visuospatial Memory Test-Revised.

RESULTS

Veterans in the mTBI group exhibited significantly lower PM performance than the control group, but the groups did not differ in their performance on RM measures. Further analysis revealed that Veterans in the mTBI group with current PTSD (mTBI/PTSD+) demonstrated significantly lower performance on the PM measure than Veterans in the control group. PM performance by Veterans in the mTBI group without current PTSD (mTBI/PTSD-) was intermediate between the mTBI/PTSD+ and control groups, and results for the mTBI/PTSD- group were not significantly different from either of the other two groups.

CONCLUSIONS

Results suggest that PM performance may be a sensitive marker of cognitive dysfunction among OEF/OIF/OND Veterans with a history of self-reported blast-related mTBI and comorbid PTSD. Reduced PM may account, in part, for complaints of cognitive difficulties in this Veteran cohort, even years post-injury. (JINS, 2018, 24, 324-334).

Symptoms of Posttraumatic Stress Rather Than Mild Traumatic Brain Injury Best Account for Altered Emotional Responses in Military Veterans

Emotional dysfunction is evident in posttraumatic stress disorder (PTSD), yet it is unclear what aspects of the disorder most directly relate to aberrant emotional responding. Also, the frequent co-occurrence of blast-related mild traumatic brain injuries (mTBIs) among recently deployed U.S. military personnel complicates efforts to understand the basis for emotional disruption. We studied a cross-sectional sample (enriched for PTSD and mTBI) of 123 U.S. veterans of wars in Iraq and Afghanistan. We measured subjective affective evaluations and peripheral psychophysiological responses to images with pleasant, neutral, unpleasant, and combat-related aversive content. When compared with other postdeployment participants, those who had combat-related PTSD rated pleasant image content as less positive (ηp2 = .04) and less arousing (ηp2 = .06), and exhibited heightened physiological responsivity to combat image content (ηp2 = .07). Symptoms of PTSD were associated with elevated skin conductance responses (β = .28), reduced heart rate deceleration (β = .44 to .47), and increased corrugator facial muscle electromyography (β = .47). No effects for blast-related mTBI were observed across any affective modulation measures. These findings point to a greater impact of PTSD symptomatology than blast-related mTBI on emotional functioning and highlight the utility of dimensional assessments of psychopathology for understanding the effects of combat-stress conditions on adjustment to civilian life.

White matter abnormalities are associated with overall cognitive status in blast-related mTBI

Blast-related mild traumatic brain injury (mTBI) is a common injury of the Iraq and Afghanistan Wars. Research has suggested that blast-related mTBI is associated with chronic white matter abnormalities, which in turn are associated with impairment in neurocognitive function. However, findings are inconsistent as to which domains of cognition are affected by TBI-related white matter disruption. Recent evidence that white matter abnormalities associated with blast-related mTBI are spatially variable raises the possibility that the associated cognitive impairment is also heterogeneous. Thus, the goals of this study were to examine (1) whether mTBI-related white matter abnormalities are associated with overall cognitive status and (2) whether white matter abnormalities provide a mechanism by which mTBI influences cognition. Ninety-six Operation Enduring Freedom/Operation Iraqi Freedom (OEF/OEF) veterans were assigned to one of three groups: no-TBI, mTBI without loss of consciousness (LOC) (mTBI-LOC), and mTBI with LOC (mTBI + LOC). Participants were given a battery of neuropsychological tests that were selected for their sensitivity to mTBI. Results showed that number of white matter abnormalities was associated with the odds of having clinically significant cognitive impairment. A mediation analysis revealed that mTBI + LOC was indirectly associated with cognitive impairment through its effect on white matter integrity. These results suggest that cognitive difficulties in blast-related mTBI can be linked to injury-induced neural changes when taking into account the variability of injury as well as the heterogeneity in cognitive deficits across individuals.

Self-Reported Sleep Disturbance Mediates the Relationship Between PTSD and Cognitive Outcome in Blast-Exposed OEF/OIF Veterans

OBJECTIVES

To examine the contribution of sleep disturbance to cognitive performance following blast exposure.

DESIGN

Correlational research evaluating self-reported sleep disturbance as a mediator of the association between the primary blast-related comorbidities of mild traumatic brain injury (mTBI) and posttraumatic stress disorder and cognitive outcome.

PARTICIPANTS

One hundred sixty Operation Enduring Freedom/Operation Iraqi Freedom Veterans with a history of blast exposure assigned to 1 of 3 groups (no TBI, mTBI without loss of consciousness, and mTBI with loss of consciousness).

MAIN OUTCOME MEASURES

Neuropsychological measures and self-report of sleep disturbance.

RESULTS

Increased posttraumatic stress disorder symptomatology was associated with worse performance in multiple cognitive domains. This association was mediated in part by self-reported sleep disturbance. Traumatic brain injury with loss of consciousness was associated with lower manual dexterity, but this association was not mediated by sleep disturbance.

CONCLUSIONS

Our results highlight the importance of sleep disturbance as a factor contributing to cognitive outcome in individuals with posttraumatic stress disorder symptoms. They point to the importance of considering sleep problems in the diagnosis and treatment of cognitive deficits in veterans with blast exposure.

Enduring deficits in memory and neuronal pathology after blast-induced traumatic brain injury

Few preclinical studies have assessed the long-term neuropathology and behavioral deficits after sustaining blast-induced neurotrauma (BINT). Previous studies have shown extensive astrogliosis and cell death at acute stages (<7 days) but the temporal response at a chronic stage has yet to be ascertained. Here, we used behavioral assays, immmunohistochemistry and neurochemistry in limbic areas such as the amygdala (Amy), Hippocampus (Hipp), nucleus accumbens (Nac), and prefrontal cortex (PFC), to determine the long-term effects of a single blast exposure. Behavioral results identified elevated avoidance behavior and decreased short-term memory at either one or three months after a single blast event. At three months after BINT, markers for neurodegeneration (FJB) and microglia activation (Iba-1) increased while index of mature neurons (NeuN) significantly decreased in all brain regions examined. Gliosis (GFAP) increased in all regions except the Nac but only PFC was positive for apoptosis (caspase-3). At three months, tau was selectively elevated in the PFC and Hipp whereas α-synuclein transiently increased in the Hipp at one month after blast exposure. The composite neurochemical measure, myo-inositol+glycine/creatine, was consistently increased in each brain region three months following blast. Overall, a single blast event resulted in enduring long-term effects on behavior and neuropathological sequelae.

The Effects of Aging, Malingering, and Traumatic Brain Injury on Computerized Trail-Making Test Performance

The trail making test (TMT) is widely used to assess speed of processing and executive function. However, normative data sets gathered at different sites show significant inconsistencies. Here, we describe a computerized version of the TMT (C-TMT) that increases the precision and replicability of the TMT by permitting a segment-by-segment analysis of performance and separate analyses of dwell-time, move-time, and error time. Experiment 1 examined 165 subjects of various ages and found that completion times on both the C-TMT-A (where subjects connect successively numbered circles) and the C-TMT-B (where subjects connect circles containing alternating letters and numbers) were strongly influenced by age. Experiment 2 examined 50 subjects who underwent three test sessions. The results of the first test session were well fit by the normative data gathered in Experiment 1. Sessions 2 and 3 demonstrated significant learning effects, particularly on the C-TMT-B, and showed good test-retest reliability. Experiment 3 examined performance in subjects instructed to feign symptoms of traumatic brain injury: 44% of subjects produced abnormal completion times on the C-TMT-A, and 18% on the C-TMT-B. Malingering subjects could be distinguished from abnormally slow controls based on (1) disproportionate increases in dwell-time on the C-TMT-A, and (2) greater deficits on the C-TMT-A than on the C-TMT-B. Experiment 4 examined the performance of 28 patients with traumatic brain injury: C-TMT-B completion times were slowed, and TBI patients showed reduced movement velocities on both tests. The C-TMT improves the reliability and sensitivity of the trail making test of processing speed and executive function.

Comparing the Neuropsychological Test Performance of Operation Enduring Freedom/Operation Iraqi Freedom (OEF/OIF) Veterans with and without Blast Exposure, Mild Traumatic Brain Injury, and Posttraumatic Stress Symptoms

To compare neuropsychological test performance of Veterans with and without mild traumatic brain injury (MTBI), blast exposure, and posttraumatic stress disorder (PTSD) symptoms. We compared the neuropsychological test performance of 49 Operation Enduring Freedom/Operation Iraqi Freedom (OEF/OIF) Veterans diagnosed with MTBI resulting from combat blast-exposure to that of 20 blast-exposed OEF/OIF Veterans without history of MTBI, 23 OEF/OIF Veterans with no blast exposure or MTBI history, and 40 matched civilian controls. Comparison of neuropsychological test performance across all four participant groups showed a complex pattern of mixed significant and mostly nonsignificant results, with omnibus tests significant for measures of attention, spatial abilities, and executive function. The most consistent pattern was the absence of significant differences between blast-exposed Veterans with MTBI history and blast-exposed Veterans without MTBI history. When blast-exposed Veteran groups with and without MTBI history were aggregated and compared to non-blast-exposed Veterans, there were significant differences for some measures of learning and memory, spatial abilities, and executive function. However, covariation for severity of PTSD symptoms eliminated all significant omnibus neuropsychological differences between Veteran groups. Our results suggest that, although some mild neurocognitive effects were associated with blast exposure, these neurocognitive effects might be better explained by PTSD symptom severity rather than blast exposure or MTBI history alone.

Factors associated with inconsistency in self-reported mild traumatic brain injury over time among military personnel in Iraq

BACKGROUND

Estimates of the prevalence of mild traumatic brain injury (mTBI) among military personnel and combat veterans rely almost exclusively on retrospective self-reports; however, reliability of these reports has received little attention.

AIMS

To examine the consistency of reporting of mTBI over time and identify factors associated with inconsistent reporting.

METHOD

A longitudinal cohort of 948 US National Guard Soldiers deployed to Iraq completed self-report questionnaire screening for mTBI and psychological symptoms while in-theatre 1 month before returning home (time 1, T1) and 1 year later (time 2, T2).

RESULTS

Most respondents (n = 811, 85.5%) were consistent in their reporting of mTBI across time. Among those who were inconsistent in their reports (n = 137, 14.5%), the majority denied mTBI at T1 and affirmed mTBI at T2 (n = 123, 89.8%). Respondents rarely endorsed mTBI in-theatre and later denied mTBI (n = 14, 10.2% of those with inconsistent reports). Post-deployment post-traumatic stress symptoms and non-specific physical complaints were significantly associated with inconsistent report of mTBI.

CONCLUSIONS

Military service members' self-reports of mTBI are generally consistent over time; however, inconsistency in retrospective self-reporting of mTBI status is associated with current post-traumatic stress symptoms and non-specific physical health complaints.

Effects of low-level blast exposure on the nervous system: is there really a controversy?

High-pressure blast waves can cause extensive CNS injury in human beings. However, in combat settings, such as Iraq and Afghanistan, lower level exposures associated with mild traumatic brain injury (mTBI) or subclinical exposure have been much more common. Yet controversy exists concerning what traits can be attributed to low-level blast, in large part due to the difficulty of distinguishing blast-related mTBI from post-traumatic stress disorder (PTSD). We describe how TBI is defined in human beings and the problems posed in using current definitions to recognize blast-related mTBI. We next consider the problem of applying definitions of human mTBI to animal models, in particular that TBI severity in human beings is defined in relation to alteration of consciousness at the time of injury, which typically cannot be assessed in animals. However, based on outcome assessments, a condition of "low-level" blast exposure can be defined in animals that likely approximates human mTBI or subclinical exposure. We review blast injury modeling in animals noting that inconsistencies in experimental approach have contributed to uncertainty over the effects of low-level blast. Yet, animal studies show that low-level blast pressure waves are transmitted to the brain. In brain, low-level blast exposures cause behavioral, biochemical, pathological, and physiological effects on the nervous system including the induction of PTSD-related behavioral traits in the absence of a psychological stressor. We review the relationship of blast exposure to chronic neurodegenerative diseases noting the paradoxical lowering of Abeta by blast, which along with other observations suggest that blast-related TBI is pathophysiologically distinct from non-blast TBI. Human neuroimaging studies show that blast-related mTBI is associated with a variety of chronic effects that are unlikely to be explained by co-morbid PTSD. We conclude that abundant evidence supports low-level blast as having long-term effects on the nervous system.

Occupational needs and intervention strategies for military personnel with mild traumatic brain injury and persistent post-concussion symptoms: a review

Mild traumatic brain injury (mTBI), also known as concussion, has been labeled the "signature injury" of the wars in Iraq and Afghanistan. A subset of military personnel with mTBI experience ongoing symptoms well beyond the normal recovery window. While much research has been dedicated to understanding the etiology and severity of the symptoms, very little has assessed how long-term symptoms impact participation in daily life. A scoping study of the occupational science and occupational therapy literature was conducted to ascertain the current state of research on the impact of mTBI on participation in daily life activities, as well as occupational therapy interventions for mTBI. Although the emphasis in this article is on military personnel with mTBI, studies on civilians with mTBI were included in the review as research with military populations is extremely limited. Based on the literature reviewed, the author suggests a role for occupational science research and occupational therapy practice in meeting the occupational needs of military service members with persistent symptoms after mTBI.

Factors Associated with Mild Traumatic Brain Injury in Veterans and Military Personnel: A Systematic Review

A history of mild traumatic brain injury (mTBI) is common among military members who served in Operations Enduring Freedom, Iraqi Freedom, and New Dawn (OEF/OIF/OND). We completed a systematic review to describe the cognitive, mental health, physical health, functional, social, and cost consequences of mTBI in Veteran and military personnel. Of 2668 reviewed abstracts, the 31 included studies provided very low strength evidence for the questions of interest. Cognitive, physical, and mental health symptoms were commonly reported by Veterans/military members with a history of mTBI. On average, these symptoms were not significantly more common in those with a history of mTBI than in those without, although a lack of significant mean differences does not preclude the possibility that some individuals could experience substantial effects related to mTBI history. Evidence of potential risk or protective factors moderating mTBI outcomes was unclear. Although the overall strength of evidence is very low due to methodological limitations of included studies, our findings are consistent with civilian studies. Appropriate re-integration services are needed to address common comorbid conditions, such as treatment for post-traumatic stress disorder, substance use disorders, headaches, and other difficulties that Veterans and members of the military may experience after deployment regardless of mTBI history. (JINS, 2014, 20, 1-13).

Traumatic brain injury: guidance in a forensic context from outcome, dose-response, and response bias research

Traumatic brain injury (TBI) occurs at a high incidence, involving millions of individuals in the U.S. alone. Related to this, there are large numbers of litigants and claimants who are referred annually for forensic evaluation. In formulating opinions regarding claimed injuries, the present review advises experts to rely on two sets of information: TBI outcome and neuropsychological dose-response studies of non-litigants and non-claimants, and response bias literature that has demonstrated the relatively high risk of invalid responding among examinees referred within a secondary gain context, which in turn has resulted in the development of specific assessment methods. Regarding prospective methods for detecting possible response bias, both symptom validity tests, for measuring over-reporting of symptoms on inventories and questionnaires, and performance validity tests, for measuring insufficient effort on ability tests, are considered essential.

Effects and outcomes in civilian and military traumatic brain injury: similarities, differences, and forensic implications

Traumatic brain injury (TBI) is a prominent public health problem in both civilian and military settings. This article discusses similarities and differences in the assessment and treatment of TBI and the attendant forensic implications. Acute care and management of moderate/severe TBI tend to be similar across environments, as is the recognition of disability status in affected individuals. By contrast, an increased focus on mild TBI in recent years has resulted in a reliance on self-report and screening measures to validate the occurrence of events leading to injury. This has complicated assessment, treatment and subsequent medicolegal proceedings. The neuropsychological literature has provided significant guidance on these difficult issues, although the complexity of disability adjudication for active duty members of the military and veterans continues to pose challenges for clinicians in evaluative and treatment contexts.

Neuropsychological effects of self-reported deployment-related mild TBI and current PTSD in OIF/OEF veterans

Current combat veterans are exposed to many incidents that may result in mild traumatic brain injury (mTBI) and/or posttraumatic stress disorder (PTSD). While there is literature on the neuropsychological consequences of PTSD only (PTSD-o) and mTBI alone (mTBI-o), less has been done to explore their combined (mTBI+PTSD) effect. The goal of this study was to determine whether Operation Iraqi Freedom (OIF) and Operation Enduring Freedom (OEF) veterans with mTBI+PTSD have poorer cognitive and psychological outcomes than veterans with PTSD-o, mTBI-o, or combat exposure-only. The final sample included 20 OIF/OEF veterans with histories of self-reported deployment mTBI (mTBI-o), 19 with current PTSD (PTSD-o), 21 with PTSD and self-reported mTBI (mTBI+PTSD), and 21 combat controls (CC) (no PTSD and no reported mTBI). Groups were formed using structured interviews for mTBI and PTSD. All participants underwent comprehensive neuropsychological testing, including neurocognitive and psychiatric feigning tests. Results of cognitive tests revealed significant differences in performance in the mTBI+PTSD and PTSD-o groups relative to mTBI-o and CC. Consistent with previous PTSD literature, significant differences were found on executive (switching) tasks, verbal fluency, and verbal memory. Effect sizes tended to be large in both groups with PTSD. Thus, PTSD seems to be an important variable affecting neuropsychological profiles in the post-deployment time period. Consistent with literature on civilian mTBI, the current study did not find evidence that combat-related mTBI in and of itself contributes to objective cognitive impairment in the late stage of injury.