Discriminating Mild Traumatic Brain Injury and Posttraumatic Stress Disorder Using Latent Neuroimaging and Neuropsychological Profiles in Active-Duty Military Service Members.

OBJECTIVE: Mild traumatic brain injury (mTBI) and posttraumatic stress disorder (PTSD) commonly occur among military Service Members and Veterans and have heterogenous, but also overlapping symptom presentations, which often complicate the diagnoses of underlying impairments and development of effective treatment plans. Thus, we sought to examine whether the combination of whole brain gray matter (GM) and white matter (WM) structural measures with neuropsychological performance can aid in the classification of military personnel with mTBI and PTSD. METHODS: Active-Duty US Service Members ( n = 156; 87.8% male) with a history of mTBI, PTSD, combined mTBI+PTSD, or orthopedic injury completed a neuropsychological battery and T1- and diffusion-weighted structural neuroimaging. Cortical, subcortical, ventricular, and WM volumes and whole brain fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD) were calculated. Latent profile analyses were performed to determine how the GM and WM indicators, together with neuropsychological indicators, classified individuals. RESULTS: For both GM and WM, respectively, a 4-profile model was the best fit. The GM model identified greater ventricular volumes in Service Members with cognitive symptoms, including those with a diagnosis of mTBI, either alone or with PTSD. The WM model identified reduced FA and elevated RD in those with psychological symptoms, including those with PTSD or mTBI and comorbid PTSD. However, contrary to expectation, a global neural signature unique to those with comorbid mTBI and PTSD was not identified. CONCLUSIONS: The findings demonstrate that neuropsychological performance alone is more robust in differentiating Active-Duty Service Members with mTBI and PTSD, whereas global neuroimaging measures do not reliably differentiate between these groups.

Research Letter: Long-Term Outcomes Following Cognitive Rehabilitation for Mild Traumatic Brain Injury: A 5-Year Follow-Up of a Cohort From the SCORE Randomized Clinical Trial.

OBJECTIVE: To examine the functioning of military service members 5 years after completing a randomized controlled trial (RCT) of cognitive rehabilitation for mild traumatic brain injury (mTBI). SETTING: Home-based telephonic interview and internet-based self-ratings. PARTICIPANTS: Sixty-nine of the 126 (55%) active-duty service members who were enrolled in a 4-arm RCT of cognitive rehabilitation 3 to 24 months after mTBI and were successfully contacted by phone 5 years later. Original and 5-year follow-up participants in each of 4 RCT treatment arms included: psychoeducation ( n = 32 original, n = 17 follow-up), computer ( n = 30 original, n = 11 follow-up), therapist-directed ( n = 30 original, n = 23 follow-up), integrated ( n = 34 original, n = 18 follow-up). DESIGN: Inception cohort evaluated 5 years after completion of an RCT of cognitive rehabilitation. MAIN MEASURES: Postconcussion symptoms (Neurobehavioral Symptom Inventory total score), psychological distress (Symptom Checklist-90-revised Global Severity Index score), and functional cognitive/behavioral symptoms (Key Behaviors Change Inventory total average score). RESULTS: Participants' postconcussive symptoms and psychological distress improved at the 5-year follow-up. Functional cognitive/behavioral symptoms were not significantly improved, but therapeutic gains were maintained across time, to 5 years after completing the RCT. CONCLUSION: In this sample of military personnel, postconcussive symptoms and psychological distress significantly improved from posttreatment to 5 years after cognitive rehabilitation, regardless of treatment arm. Functional cognitive/behavioral symptoms significantly improved with treatment while treatment gains were maintained at the 5-year follow-up. Replication of these results with a larger sample and interim data between 18 weeks and 5 years post-treatment is needed.

Latent Neuropsychological Profiles to Discriminate Mild Traumatic Brain Injury and Posttraumatic Stress Disorder in Active-Duty Service Members.

OBJECTIVE: To determine whether cognitive and psychological symptom profiles differentiate clinical diagnostic classifications (eg, history of mild traumatic brain injury [mTBI] and posttraumatic stress disorder [PTSD]) in military personnel. METHODS: US Active-Duty Service Members ( N = 209, 89% male) with a history of mTBI ( n = 56), current PTSD ( n = 23), combined mTBI + PTSD ( n = 70), or orthopedic injury controls ( n = 60) completed a neuropsychological battery assessing cognitive and psychological functioning. Latent profile analysis was performed to determine how neuropsychological outcomes of individuals clustered together. Diagnostic classifications (ie, mTBI, PTSD, mTBI + PTSD, and orthopedic injury controls) within each symptom profile were examined. RESULTS: A 5-profile model had the best fit. The profiles differentiated subgroups with high (34.0%) or normal (21.5%) cognitive and psychological functioning, cognitive symptoms (19.1%), psychological symptoms (15.3%), and combined cognitive and psychological symptoms (10.0%). The symptom profiles differentiated participants as would generally be expected. Participants with PTSD were mainly represented in the psychological symptom subgroup, while orthopedic injury controls were mainly represented in the high-functioning subgroup. Further, approximately 79% of participants with comorbid mTBI and PTSD were represented in a symptomatic group (∼24% = cognitive symptoms, ∼29% = psychological symptoms, and 26% = combined cognitive/psychological symptoms). Our results also showed that approximately 70% of military personnel with a history of mTBI were represented in the high- and normal-functioning groups. CONCLUSIONS: These results demonstrate both overlapping and heterogeneous symptom and performance profiles in military personnel with a history of mTBI, PTSD, and/or mTBI + PTSD. The overlapping profiles may underscore why these diagnoses are often difficult to diagnose and treat, but suggest that advanced statistical models may aid in identifying profiles representing symptom and cognitive performance impairments within patient groups and enable identification of more effective treatment targets.

Patient Attribution of Posttraumatic Symptoms to Brain Injury Versus PTSD in Military-Related Mild TBI.

OBJECTIVE: Persistent cognitive, somatic, and neuropsychiatric symptoms following mild traumatic brain injury (TBI) are influenced by posttraumatic stress disorder (PTSD), particularly in military patients. The authors evaluated the degree to which military service members with a history of mild TBI attributed posttraumatic symptoms to TBI versus PTSD. METHODS: Service members (N=372) with mild TBI were surveyed about the severity of posttraumatic symptoms across four symptom clusters (cognitive, affective, somatosensory, and vestibular) with the Neurobehavioral Symptom Inventory (NSI). Participants rated the degree to which they believed TBI, PTSD, or other conditions contributed to their symptoms. Differences in cognitive, affective, somatosensory, and vestibular symptom severity were evaluated across participants with TBI, PTSD, or combined TBI-PTSD attribution. Logistic regression was used to evaluate the association between symptom profiles and attribution. RESULTS: Participants attributed symptoms mostly to TBI, followed by insufficient sleep, PTSD, chronic pain, depression, and deployment-readjustment stress. PTSD and combined TBI-PTSD attribution were associated with higher total NSI scores (39.5 and 51.6, respectively), compared with TBI attribution only (31.4) (F=29.08, df=3, 358, p<0.01), as well as higher scores in every symptom category. More severe affective symptoms were associated with decreased odds of TBI attribution (odds ratio=0.90, 95% CI=0.83-0.97) and increased odds of PTSD attribution (odds ratio=1.14, 95% CI=1.03-1.26). A PTSD diagnosis was highly associated with PTSD attribution (odds ratio=2.44, 95% CI=1.07-5.58). CONCLUSIONS: The nature and severity of posttraumatic symptoms appear to play a role in patient beliefs about the causes of symptoms, whether from TBI or PTSD.

Self-efficacy predicts response to cognitive rehabilitation in military service members with post-concussive symptoms.

This study examined whether self-efficacy differentiated treatment responders from non-responders in a trial of cognitive rehabilitation (CR) for postconcussive symptoms. 126 service members with mild TBI seen on average 9.5 months since injury completed one of four cognitive rehabilitation treatments for 6 weeks. The four treatment arms were: (1) Psychoeducation control, (2) Self-administered computerized CR, (3) Interdisciplinary CR, and (4) Interdisciplinary CR integrated with CBT. Outcome was assessed across time (baseline, and 6, 12, and 18 weeks post-treatment) for three domains: psychological (Symptom Checklist-90-Revised; SCL-90-R), cognitive (Paced Auditory Serial Addition Test; PASAT), and functional/behavioural (Key Behaviors Change Inventory; KBCI). Mixed model ANOVAs tested for self-efficacy differences across time in treatment responders versus non-responders, as defined by reliable change indices. A significant interaction was found on the SCL-90 such that responders had increasing self-efficacy with respect to psychological symptoms across four time points, whereas non-responders' self-efficacy did not change. Perceived self-efficacy at the beginning of treatment was associated with treatment engagement within the psychological domain for responders only, suggesting a mediating role in treatment outcome. Overall, results suggest that increasing patients' level of self-efficacy may be important for successful treatment of psychological distress in those with remote concussion.

Neuropsychological Performance and Subjective Symptom Reporting in Military Service Members With a History of Multiple Concussions: Comparison With a Single Concussion, Posttraumatic Stress Disorder, and Orthopedic Trauma.

OBJECTIVE: To examine differences in objective neurocognitive performance and subjective cognitive symptoms in individuals with a history of a single concussion, multiple concussions, orthopedic injuries, and posttraumatic stress disorder (PTSD). METHOD: Participants included 116 military service members who sustained a mild traumatic brain injury (mTBI) during combat deployment. Subjects were subdivided into groups based on concussion frequency: a single concussion (n = 42), 2 concussions (n = 21), and 3 or more concussions (n = 53). Eighty-one subjects sustained an orthopedic injury (n = 60) during deployment or were diagnosed with PTSD (n = 21), but had no history of mTBI. Subjects completed a battery of neuropsychological tests and self-report measures of postconcussive symptoms, PTSD symptoms, and psychopathology. RESULTS: No differences were found among the concussion groups on a composite neuropsychological measure. The PTSD group had the highest number of symptom complaints, with the 2-concussion and 3-plus-concussion groups being most similar to the PTSD group. The concussion groups showed a nonsignificant pattern of increasing distress with increasing number of concussions. CONCLUSIONS: The current findings are consistent with meta-analytic results showing no differential effect on neuropsychological functioning due to multiple concussions. Results also support the burden of adversity hypothesis suggesting increasing symptom levels with increasing psychological or physically traumatic exposures.

Relationships Between Subcortical Shape Measures and Subjective Symptom Reporting in US Service Members With Mild Traumatic Brain Injury.

OBJECTIVE: To assess interactions of subcortical structure with subjective symptom reporting associated with mild traumatic brain injury (mTBI), using advanced shape analysis derived from volumetric MRI. PARTICIPANTS: Seventy-six cognitively symptomatic individuals with mTBI and 59 service members sustaining only orthopedic injury. DESIGN: Descriptive cross-sectional study. MAIN MEASURES: Self-report symptom measures included the PTSD Checklist-Military, Neurobehavioral Symptom Inventory, and Symptom Checklist-90-Revised. High-dimensional measures of shape characteristics were generated from volumetric MRI for 7 subcortical structures in addition to standard volume measures. RESULTS: Several significant interactions between group status and symptom measures were observed across the various shape measures. These interactions were revealed in the right thalamus and globus pallidus for each of the shape measures, indicating differences in structure thickness and expansion/contraction for these regions. No relationships with volume were observed. CONCLUSION: Results provide evidence for the sensitivity of shape measures in differentiating symptomatic mTBI individuals from controls, while volumetric measures did not exhibit this same sensitivity. Disruptions to thalamic nuclei identified here highlight the role of the thalamus in the spectrum of symptoms associated with mTBI. Additional work is needed to prospectively, and longitudinally, assess these measures along with cognitive performance and advanced multimodal imaging methods to extend the utility of shape analysis in relation to functional outcomes in this population.

Diffusion Imaging Findings in US Service Members With Mild Traumatic Brain Injury and Posttraumatic Stress Disorder.

OBJECTIVE: Use diffusion tensor imaging to investigate white matter microstructure attributable to mild TBI (mTBI) and/or posttraumatic stress disorder (PTSD). PARTICIPANTS: Twenty-seven individuals with mTBI only, 16 with PTSD only, 42 with mTBI + PTSD, and 43 service members who sustained orthopedic injury. DESIGN: Descriptive cross-sectional study. MAIN MEASURES: Clinical diffusion tensor imaging sequence to assess fractional anisotropy, mean, axial, and radial diffusivity within selected regions of interest. RESULTS: Corrected analyses revealed a pattern of lower white matter integrity in the PTSD group for several scalar metrics. Regions affected included primarily right hemisphere areas of the internal capsule. These differences associated with the PTSD only cohort were observed in relation to all 3 comparison groups, while the mTBI + PTSD group did not exhibit any notable pattern of white matter abnormalities. CONCLUSION: Results suggest that lower resolution scan sequences are sensitive to post-acute abnormalities associated with PTSD, particularly in the right hemisphere. In addition, these findings suggest that ongoing PTSD symptoms are associated with differences in white matter diffusion that are more readily detected in a clinical scan sequence than mTBI abnormalities. Future studies are needed to prospectively assess service members prior to onset of injury to verify this pattern of results.

Cognitive Rehabilitation for Military Service Members With Mild Traumatic Brain Injury: A Randomized Clinical Trial.

OBJECTIVE: To compare cognitive rehabilitation (CR) interventions for mild traumatic brain injury (mTBI) with standard of care management, including psychoeducation and medical care for noncognitive symptoms. SETTING: Military medical center. PARTICIPANTS: A total of 126 service members who received mTBI from 3 to 24 months before baseline evaluation and reported ongoing cognitive difficulties. INTERVENTIONS: Randomized clinical trial with treatment outcomes assessed at baseline, 3-week, 6-week, 12-week, and 18-week follow-ups. Participants were randomly assigned to one of four 6-week treatment arms: (1) psychoeducation, (2) computer-based CR, (3) therapist-directed manualized CR, and (4) integrated therapist-directed CR combined with cognitive-behavioral psychotherapy (CBT). Treatment dosage was constant (10 h/wk) for intervention arms 2 to 4. MEASURES: Paced Auditory Serial Addition Test (PASAT); Symptom Checklist-90 Revised (SCL-90-R); Key Behaviors Change Inventory (KBCI). RESULTS: No differences were noted between treatment arms on demographics, injury-related characteristics, or psychiatric comorbidity apart from education, with participants assigned to the computer arm having less education. Using mixed-model analysis of variance, all 4 treatment groups showed a significant improvement over time on the 3 primary outcome measures. Treatment groups showed equivalent improvement on the PASAT. The therapist-directed CR and integrated CR treatment groups had better KBCI outcomes compared with the psychoeducation group. Improvements on primary outcome measures during treatment were maintained at follow-up with no differences among arms. CONCLUSIONS: Both therapist-directed CR and integrated CR with CBT reduced functional cognitive symptoms in service members after mTBI beyond psychoeducation and medical management alone.

Completion of Multidisciplinary Treatment for Persistent Postconcussive Symptoms Is Associated With Reduced Symptom Burden.

OBJECTIVE: To investigate the pre- to posttreatment changes in both posttraumatic stress disorder (PTSD) and persistent postconcussive symptoms (PPCSs). SETTING AND PARTICIPANTS: We studied 257 active-duty patients with a history of mild traumatic brain injury (mTBI) who completed multidisciplinary outpatient treatment at Brooke Army Medical Center TBI Clinic from 2008 to 2013. This treatment program included cognitive rehabilitation; vestibular interventions; headache management; and integrated behavioral healthcare to address co-occurring psychiatric conditions such as PTSD, depression, and sleep disturbance. DESIGN: A 1-group; preexperimental, pre- to posttreatment study. MAIN MEASURES: The Neurobehavioral Symptom Inventory (NSI) was used to assess PPCSs, and the PTSD Checklist-Military Version (PCL-M) was used to asses PTSD symptoms. RESULTS: Global PPCS resolution (mean NSI: 35.0 pre vs 23.8 post; P < .0001; d = 0.72) and PTSD symptom resolution (mean PCL-M: 43.2 pre vs 37.7 post; P < .0001; d = 0.34) were statistically significant. Compared with those with only mTBI, patients with mTBI and PTSD reported greater global PPCS impairment both pretreatment (mean NSI: 48.7 vs 27.9; P < .0001) and posttreatment (mean NSI: 36.2 vs 17.4; P < .0001). After adjusting for pretreatment NSI scores, patients with comorbid PTSD reported poorer PPCS resolution than those with mTBI alone (mean NSI: 27.9 pre vs 21.7 post; P = .0009). CONCLUSION: We found a reduction in both self-reported PPCSs and PTSD symptoms; however, future studies are needed to identify specific components of care associated with symptom reduction.

Screening for postdeployment conditions: development and cross-validation of an embedded validity scale in the neurobehavioral symptom inventory.

OBJECTIVE: To develop and cross-validate internal validity scales for the Neurobehavioral Symptom Inventory (NSI). PARTICIPANTS: Four existing data sets were used: (1) outpatient clinical traumatic brain injury (TBI)/neurorehabilitation database from a military site (n = 403), (2) National Department of Veterans Affairs TBI evaluation database (n = 48 175), (3) Florida National Guard nonclinical TBI survey database (n = 3098), and (4) a cross-validation outpatient clinical TBI/neurorehabilitation database combined across 2 military medical centers (n = 206). RESEARCH DESIGN: Secondary analysis of existing cohort data to develop (study 1) and cross-validate (study 2) internal validity scales for the NSI. MAIN MEASURES: The NSI, Mild Brain Injury Atypical Symptoms, and Personality Assessment Inventory scores. RESULTS: Study 1: Three NSI validity scales were developed, composed of 5 unusual items (Negative Impression Management [NIM5]), 6 low-frequency items (LOW6), and the combination of 10 nonoverlapping items (Validity-10). Cut scores maximizing sensitivity and specificity on these measures were determined, using a Mild Brain Injury Atypical Symptoms score of 8 or more as the criterion for invalidity. Study 2: The same validity scale cut scores again resulted in the highest classification accuracy and optimal balance between sensitivity and specificity in the cross-validation sample, using a Personality Assessment Inventory Negative Impression Management scale with a T score of 75 or higher as the criterion for invalidity. CONCLUSIONS: The NSI is widely used in the Department of Defense and Veterans Affairs as a symptom-severity assessment following TBI, but is subject to symptom overreporting or exaggeration. This study developed embedded NSI validity scales to facilitate the detection of invalid response styles. The NSI Validity-10 scale appears to hold considerable promise for validity assessment when the NSI is used as a population-screening tool.

Primary progressive aphasia and amyotrophic lateral sclerosis (PPA-ALS): A longitudinal case study.

OBJECTIVE: Approximately 50% of patients with amyotrophic lateral sclerosis (ALS) experience cognitive decline, with frontotemporal dementia (FTD) accounting for up to 15% of these cases. Despite this, there is considerable delay in diagnosis, which affects patient care. METHODS: We report longitudinal results of neuropsychological evaluations in a patient diagnosed with non-fluent/agrammatic primary progressive aphasia (nfvPPA) and amyotrophic lateral sclerosis (ALS). The patient, Ms. X, presented with progressive speech difficulties starting in her late-60's. Initial diagnosis was nfvPPA. After 4-5 years of progressive swallowing difficulties, as well as facial weakness, her diagnosis was modified to PPA-ALS. RESULTS: Ms. X underwent neuropsychological evaluations three times over a period of five years. Results of evaluations were intact and stable over time, except for progressive loss of speech impacting her performance on a sentence repetition task. CONCLUSION: This case study provides valuable insight into the overlap between PPA-ALS from a neuropsychological standpoint. The results reflect preserved cognitive skills in the context of loss of speech and motor abilities. This case study also shows the length of time between onset of symptoms and clear diagnosis, which often requires an immense amount of health literacy and personal advocacy on the part of the patient.

Neuropsychological Evaluation in Traumatic Brain Injury.

Neuropsychological evaluations can be helpful in the aftermath of traumatic brain injury. Cognitive functioning is assessed using standardized assessment tools and by comparing an individual's scores on testing to normative data. These evaluations examine objective cognitive functioning as well as other factors that have been shown to influence performance on cognitive tests (eg, psychiatric conditions, sleep) in an attempt to answer a specific question from referring providers. Referral questions may focus on the extent of impairment, the trajectory of recovery, or ability to return to work, sport, or the other previous activity.

Utility of the Mayo-Portland adaptability inventory-4 for self-reported outcomes in a military sample with traumatic brain injury.

OBJECTIVE: To investigate the psychometric properties of the Mayo-Portland Adaptability Inventory-4 (MPAI-4) obtained by self-report in a large sample of active duty military personnel with traumatic brain injury (TBI). DESIGN: Consecutive cohort who completed the MPAI-4 as a part of a larger battery of clinical outcome measures at the time of intake to an outpatient brain injury clinic. SETTING: Medical center. PARTICIPANTS: Consecutively referred sample of active duty military personnel (N=404) who suffered predominantly mild (n=355), but also moderate (n=37) and severe (n=12), TBI. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: MPAI-4 RESULTS: Initial factor analysis suggested 2 salient dimensions. In subsequent analysis, the ratio of the first and second eigenvalues (6.84:1) and parallel analysis indicated sufficient unidimensionality in 26 retained items. Iterative Rasch analysis resulted in the rescaling of the measure and the removal of 5 additional items for poor fit. The items of the final 21-item Mayo-Portland Adaptability Inventory-military were locally independent, demonstrated monotonically increasing responses, adequately fit the item response model, and permitted the identification of nearly 5 statistically distinct levels of disability in the study population. Slight mistargeting of the population resulted in the global outcome, as measured by the Mayo-Portland Adaptability Inventory-military, tending to be less reflective of very mild levels of disability. CONCLUSIONS: These data collected in a relatively large sample of active duty service members with TBI provide insight into the ability of patients to self-report functional impairment and the distinct effects of military deployment on outcome, providing important guidance for the meaningful measurement of outcome in this population.

Comorbidity and polypharmacy impact neurobehavioral symptoms and symptom validity failure among post-9/11 veterans with mild traumatic brain injury.

Objective: The study aimed to examine the association between post-concussive comorbidity burdens [post-traumatic stress disorder (PTSD), depression, and/or headache] and central nervous system (CNS) polypharmacy (five or more concurrent medications) with reported neurobehavioral symptoms and symptom validity screening among post-9/11 veterans with a history of mild traumatic brain injury (mTBI). Setting: Administrative medical record data from the Department of Veterans Affairs (VA) were used in the study. Participants: Post-9/11 veterans with mTBI and at least 2 years of VA care between 2001 and 2019 who had completed the comprehensive traumatic brain injury evaluation (CTBIE) were included in the study. Design: Retrospective cross-sectional design was used in the study. Main measures: Neurobehavioral Symptom Inventory (NSI), International Classification of Diseases, Ninth Revision, and Clinical Modification diagnosis codes were included in the study. Results: Of the 92,495 veterans with a history of TBI, 90% had diagnoses of at least one identified comorbidity (PTSD, depression, and/or headache) and 28% had evidence of CNS polypharmacy. Neurobehavioral symptom reporting and symptom validity failure was associated with comorbidity burden and polypharmacy after adjusting for sociodemographic characteristics. Veterans with concurrent diagnoses of PTSD, depression, and headache were more than six times more likely [Adjusted odds ratio = 6.55 (99% CI: 5.41, 7.92)]. to fail the embedded symptom validity measure (Validity-10) in the NSI. Conclusion: TBI-related multimorbidity and CNS polypharmacy had the strongest association with neurobehavioral symptom distress, even after accounting for injury and sociodemographic characteristics. Given the regular use of the NSI in clinical and research settings, these findings emphasize the need for comprehensive neuropsychological evaluation for individuals who screen positively for potential symptom overreporting, the importance of multidisciplinary rehabilitation to restore functioning following mTBI, and the conscientious utilization of symptom validity measures in research efforts.

Relationship between mechanism of injury and neurocognitive functioning in OEF/OIF service members with mild traumatic brain injuries.

Military personnel deployed to combat theaters in Iraq and Afghanistan are at risk of sustaining mild traumatic brain injuries (mTBI) from causes such as improvised explosive devices, motor vehicle accidents, and falls. Despite the high incidence of mTBI in deployed personnel, questions remain about the effects of blast-related vs. non-blast-related mTBI on acute and long-term sequelae. This investigation is a retrospective review of service members who presented for evaluation of suspected mTBI and underwent neurocognitive screening evaluation, mTBI diagnosis was made by semistructured clinical interview. Only individuals in whom mechanism of injury could be determined (blast vs. non-blast) were included. Sixty individuals were included in the final sample: 32 with blast mTBI and 28 with non-blast mTBI. There were no differences between the blast-related and non-blast-related mTBI groups on age, time since injury, combat stress symptoms, or headache. Analysis of variance showed no significant between-group differences on any of the neurocognitive performance domains. Although speculation remains that the effects of primary blast exposure are unique, the results of this study are consistent with prior research suggesting that blast-related mTBI does not differ from other mechanisms of injury with respect to cognitive sequelae in the postacute phase.

Comparing resting-state connectivity of working memory networks in U.S. Service members with mild traumatic brain injury and posttraumatic stress disorder.

Mild traumatic brain injury (mTBI) and posttraumatic stress disorder (PTSD) are prevalent among military populations, and both have been associated with working memory (WM) impairments. Previous resting-state functional connectivity (rsFC) research conducted separately in PTSD and mTBI populations suggests that there may be similar and distinct abnormalities in WM-related networks. However, no studies have compared rsFC of WM brain regions in participants with mTBI versus PTSD. We used resting-state fMRI to investigate rsFC of WM networks in U.S. Service Members (n = 127; ages 18-59) with mTBI only (n = 46), PTSD only (n = 24), and an orthopedically injured (OI) control group (n = 57). We conducted voxelwise rsFC analyses with WM brain regions to test for differences in WM network connectivity in mTBI versus PTSD. Results revealed reduced rsFC between ventrolateral prefrontal cortex (vlPFC), lateral premotor cortex, and dorsolateral prefrontal cortex (dlPFC) WM regions and brain regions in the dorsal attention and somatomotor networks in both mTBI and PTSD groups versus controls. When compared to those with mTBI, individuals with PTSD had lower rsFC between both the lateral premotor WM seed region and middle occipital gyrus as well as between the dlPFC WM seed region and paracentral lobule. Interestingly, only vlPFC connectivity was significantly associated with WM performance across the samples. In conclusion, we found primarily overlapping patterns of reduced rsFC in WM brain regions in both mTBI and PTSD groups. Our finding of decreased vlPFC connectivity associated with WM is consistent with previous clinical and neuroimaging studies. Overall, these results provide support for shared neural substrates of WM in individuals with either mTBI or PTSD.

Association between combat stress and post-concussive symptom reporting in OEF/OIF service members with mild traumatic brain injuries.

OBJECTIVE: The relationship between combat stress and post-concussive symptoms in service members with mild traumatic brain injuries (mTBI) is poorly understood. It was hypothesized that the co-occurrence of combat stress would have a significant effect on the severity of post-concussive complaints, specifically on emotional and cognitive symptoms. METHODS: Four hundred and seventy-two combat-deployed service members with mTBI completed self-report inventories of post-traumatic stress and post-concussive symptoms. Two groups were formed based on post-traumatic stress symptoms (High Combat Stress and Low Combat Stress). RESULTS: A 3-8-fold increase in post-concussive symptoms was observed when comparing the High and Low Combat Stress Groups. Elevations in post-concussive symptom reporting were not limited to emotional and/or cognitive symptoms, but rather were inclusive of all measured post-concussive symptoms. CONCLUSIONS: The findings of the present study suggest that non-brain injury-related factors, such as high-levels of combat stress, may impact post-concussive symptom reporting in this population, further confounding the accuracy of the post-concussion syndrome (PCS) diagnosis. Considerable caution should be exercised in making the diagnosis of PCS in concussed service members with co-occurring combat-stress disorders.

Self-reported neurobehavioral symptoms in combat veterans: An examination of NSI with mBIAS symptom validity scales and potential effects of psychological distress.

This study evaluated symptom validity scales from the Neurobehavioral Symptom Inventory (NSI) and mild Brain Injury Atypical Symptom Scale (mBIAS) in a sample of 338 combat veterans. Classification statistics were computed using the Structured Inventory of Malingered Symptomatology (SIMS) as the validity criterion. Symptom distress was assessed with the Patient Health Questionnaire-9 and Posttraumatic Stress Disorder (PTSD) Checklist-5. At SIMS > 14, the NSI total score resulted in the highest area under the curve (AUC; .91), followed by Validity-10 (AUC = .88) and mBIAS (AUC = .67). At SIMS > 23, both NSI total and Validity-10 AUCs decreased to .88; in contrast, mBIAS AUC increased to .75. The NSI total score and Validity-10 were interpreted to reflect symptom magnification, whereas the mBIAS may reflect symptom fabrication. There was a subsample with elevated Patient Health Questionnaire-9 (PHQ-9) and PTSD Checklist-5 scores who were significantly distressed but not deemed invalid on the NSI; however, there appears to be an upper threshold on the NSI total score (>69) beyond which nobody produced an invalid score on the SIMS. A recommended approach is provided for using NSI-related validity measures. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Number of Concussions Does Not Affect Treatment Response to Cognitive Rehabilitation Interventions Following Mild TBI in Military Service Members.

OBJECTIVE: The study objective was to determine whether number of concussions would affect symptom improvement following cognitive rehabilitation (CR) interventions. METHOD: Service members (N = 126) with concussion history completed a 6-week randomized control trial of CR interventions. Participants were stratified based on self-reported lifetime concussion frequency. Outcome measures included the Paced Auditory Serial Addition Test (PASAT), the Global Severity Index (GSI) from the Symptom Checklist-90-Revised, and the Key Behaviors Change Inventory (KBCI). RESULTS: Mixed-model analyses of variance revealed a significant main effect for time on cognitive, psychological, and neurobehavioral functioning. A significant main effect for the number of concussions was observed for GSI and KBCI, but not PASAT. Interactions between the number of concussions and time were not significant for any of the outcome variables. CONCLUSIONS: Over the 6-week interval, improvements were found for all participants across all outcome measures. Number of concussions did not affect improvements over time.