Specificity of cognitive and behavioral complaints in post-traumatic stress disorder and mild traumatic brain injury

Examining factors associated with self-reported cognitive functioning in elite military settings: considerations of combat experiences and post-traumatic stress symptomology

Exposure to traumatic events is associated with post-traumatic stress symptomology (PTSS) in a variety of populations. PTSS is also associated with self-reported everyday cognitive failures, which are acknowledged attentional lapses experienced in one's naturalistic everyday environment. While a growing literature suggests that PTSS is associated with both traumatic events and attentional functions, little is known regarding similar associations in elite military cohorts, such as Special Operations Forces (SOF) personnel. Herein, we investigate if prior combat experience is associated with everyday cognitive failures, while considering the possible mediating role of PTSS. SOF personnel (N = 119) completed self-report questionnaires assessing prior combat experience, PTSS, and everyday cognitive failures. Direct and indirect associations between these metrics were examined using structural equation modeling. Mediation analyses revealed that the correspondence between combat experiences and everyday cognitive failures is mediated by the severity of subclinical levels of PTSS. Such findings suggest that greater attention to subclinical PTSS is warranted due to its significant association with everyday cognitive failures that may contribute to deleterious mission-related failures in high-demand tactical professionals, such as SOF.

Diet's Impact on Post-Traumatic Brain Injury Depression: Exploring Neurodegeneration, Chronic Blood-Brain Barrier Destruction, and Glutamate Neurotoxicity Mechanisms

Traumatic brain injury (TBI) has a profound impact on cognitive and mental functioning, leading to lifelong impairment and significantly diminishing the quality of life for affected individuals. A healthy blood-brain barrier (BBB) plays a crucial role in guarding the brain against elevated levels of blood glutamate, making its permeability a vital aspect of glutamate regulation within the brain. Studies have shown the efficacy of reducing excess glutamate in the brain as a treatment for post-TBI depression, anxiety, and aggression. The purpose of this article is to evaluate the involvement of dietary glutamate in the development of depression after TBI. We performed a literature search to examine the effects of diets abundant in glutamate, which are common in Asian populations, when compared to diets low in glutamate, which are prevalent in Europe and America. We specifically explored these effects in the context of chronic BBB damage after TBI, which may initiate neurodegeneration and subsequently have an impact on depression through the mechanism of chronic glutamate neurotoxicity. A glutamate-rich diet leads to increased blood glutamate levels when contrasted with a glutamate-poor diet. Within the context of chronic BBB disruption, elevated blood glutamate levels translate to heightened brain glutamate concentrations, thereby intensifying neurodegeneration due to glutamate neurotoxicity.

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.

Altered basal forebrain BOLD signal variability at rest in posttraumatic stress disorder: A potential candidate vulnerability mechanism for neurodegeneration in PTSD

Individuals with posttraumatic stress disorder (PTSD) are at increased risk for the development of various forms of dementia. Nevertheless, the neuropathological link between PTSD and neurodegeneration remains unclear. Degeneration of the human basal forebrain constitutes a pathological hallmark of neurodegenerative diseases, such as Alzheimer's and Parkinson's disease. In this seed-based resting-state (rs-)fMRI study identifying as outcome measure the temporal BOLD signal fluctuation magnitude, a seed-to-voxel analyses assessed temporal correlations between the average BOLD signal within a bilateral whole basal forebrain region-of-interest and each whole-brain voxel among individuals with PTSD (n = 65), its dissociative subtype (PTSD+DS) (n = 38) and healthy controls (n = 46). We found that compared both with the PTSD and healthy controls groups, the PTSD+DS group exhibited increased BOLD signal variability within two nuclei of the seed region, specifically in its extended amygdaloid region: the nucleus accumbens and the sublenticular extended amygdala. This finding is provocative, because it mimics staging models of neurodegenerative diseases reporting allocation of neuropathology in early disease stages circumscribed to the basal forebrain. Here, underlying candidate etiopathogenetic mechanisms are neurovascular uncoupling, decreased connectivity in local- and large-scale neural networks, or disrupted mesolimbic dopaminergic circuitry, acting indirectly upon the basal forebrain cholinergic pathways. These abnormalities may underpin reward-related deficits representing a putative link between persistent traumatic memory in PTSD and anterograde memory deficits in neurodegeneration. Observed alterations of the basal forebrain in the dissociative subtype of PTSD point towards the urgent need for further exploration of this region as a potential candidate vulnerability mechanism for neurodegeneration in PTSD.

Physician Medical Assessment in a Multidisciplinary Concussion Clinic

Concussive brain injury (CBI) is encountered by clinicians in sports medicine, pediatrics, neurosurgery, neurology, physiatry, and primary care. There is no gold standard diagnostic test for CBI, nor is there consensus on what neuromusculoskeletal physical examination tests should be performed on patients who have sustained CBI. This article presents an approach to the history and physical examination of the patient who has sustained a CBI that is based on a review of the literature evidence and the authors' extensive experience with this patient population. Suggested components include an elemental neurological examination that emphasizes the oculomotor/ophthalmologic and vestibular systems, as well as appropriate musculoskeletal assessment of the craniocervical and upper shoulder girdle complex. The use of supplementary tests for CBI, including assessment of exercise tolerance using the Buffalo Concussion Treadmill Test and tests of neurocognitive function, can aid in the differential diagnosis of CBI. The proposed protocol is envisioned for initial and follow-up assessments in the clinic after CBI, as well as for those with more protracted signs or symptoms. If symptoms persist beyond 2 weeks in adults or 4 weeks in adolescents, then referral to a multidisciplinary center that focuses on CBI is recommended.

Characterizing the Risk of Depression Following Mild Traumatic Brain Injury: A Meta-Analysis of the Literature Comparing Chronic mTBI to Non-mTBI Populations

Objective: Mild traumatic brain injury (mTBI) is associated with depressed mood acutely post-injury, but there is little evidence regarding long-term depression. The aim of this study was to determine the odds ratio (OR) of depression chronically following mTBI.

Methods: We searched Medline (PubMed), ProQuest, and Web of Science from date of database creation to January 23, 2019, for eligible studies examining depression at least 6 months post-injury in adult subjects with mTBI of any etiology, including civilians and military. Three authors independently reviewed titles and abstracts for study eligibility. Data were extracted and collated by two investigators. Risk of bias was assessed with the SIGN methodology. Study data were pooled using random-effects meta-analysis. The primary exposure was mTBI, and the primary outcome was depression. Secondary exploratory variables were time of assessment, age at injury, age at assessment, sex, and etiology.

Results: We included 47 cross-sectional studies (n = 25,103 mTBI and 29,982 control), 26 cohort studies (n = 70,119 mTBI, 262,034 control), four prospective observational studies (n = 1,058 mTBI and 733 control), two prospective longitudinal studies (n = 119 mTBI, 81 control), two case-control studies (n = 56 mTBI, 56 control), and one randomized controlled trial (n = 252 mTBI, 3,214 control). mTBI was associated with a 3.29-fold increased risk of depression (OR 3.29, 95% CI 2.68–4.03, I² = 96%). The OR for depression did not change when subjects were assessed at 6–12 months (OR 2.43, 1.45–4.07), years 1–2 (OR 4.12, 2.10–8.07); 2–10 (OR 3.28, 2.42–4.46), or 10+ (OR 3.42, 1.51–7.77). Similar risk of depression was sustained across different age at injury (<25: OR 2.26, 1.82–2.81; 25–35: OR 4.67, 3.06–7.14; >35: OR 2.69, 1.42–5.10) and different age at assessment (<40 years: OR 3.14, 2.48–3.99; >40 years: OR 4.57, 2.54–8.24). Female sex had a non-significant increase in OR (OR 19.97, 2.39–166.93) compared to male (OR 3.0, 2.33–3.86). mTBI etiology had no impact on depression.

Conclusions: Those experiencing mTBI are more than three times more likely to experience depression compared to those without a history of mTBI, and this risk remains decades beyond the mTBI event. Future longitudinal studies are needed to identify and mitigate this risk.

Chronic Cognitive Deficits and Associated Histopathology Following Closed-Head Concussive Injury in Rats

Close-head concussive injury, as one of the most common forms of traumatic brain injury (TBI), has been shown to induce cognitive deficits that are long lasting. A concussive impact model was previously established in our lab that produces clinically relevant signs of concussion and induced acute pathological changes in rats. To evaluate the long-term effects of repeated concussions in this model, we utilized a comprehensive Morris water maze (MWM) paradigm for cognitive assessments at 1 and 6 months following repeated concussive impacts in rats. As such, adult Sprague-Dawley rats received either anesthesia (sham) or repeated concussive impacts (4 consecutive impacts at 1 h interval). At 1 month post-injury, results of the spatial learning task showed that the average latencies to locate the hidden "escape" platform were significantly longer in the injured rats over the last 2 days of the MWM testing compared to sham controls (p < 0.05). In the memory retention task, rats subjected to repeated concussive impacts also spent significantly less time in the platform zone searching for the missing platform during the probe trial (p < 0.05). On the working memory task, the injured rats showed a trend toward worse performance, but this failed to reach statistical significance compared to sham controls (p = 0.07). At 6 months post-injury, no differences were detected between the injured group and sham controls in either the spatial learning or probe trials. However, rats with repeated concussive impacts exhibited significantly worsened working memory performance compared to sham controls (p < 0.05). In addition, histopathological assessments for axonal neurodegeneration using silver stain showed that repeated concussive impacts induced significantly more axonal degeneration in the corpus callosum compared to sham controls (p < 0.05) at 1 month post-injury, whereas such difference was not observed at 6 months post-injury. Overall, the results show that repeated concussive impacts in our model produced significant cognitive deficits in both spatial learning abilities and in working memory abilities in a time-dependent fashion that may be indicative of progressive pathology and warrant further investigation.

Contribution of Perceived Cognitive Functioning to Quality of Life in Service Members and Veterans With Posttraumatic Stress Disorder

Perceived cognitive impairment is a core clinical feature of posttraumatic stress disorder (PTSD) and may be an important determinant of quality of life (QOL) in those who suffer from this disorder. Using a clinical data repository, we evaluated this hypothesis in a cross-sectional sample of U.S. military service members and veterans who served after September 11, 2001, and were seeking mental health treatment at a tertiary outpatient clinic. A consecutive series of 117 patients with a clinical diagnosis of PTSD completed a battery of questionnaires at intake, including the PTSD Checklist (Weathers, Litz, Herman, Huska, & Keane, 1993), a 4-item Cognitive Symptom subscale of the Neurobehavioral Symptom Inventory (Cicerone & Kalmar, 1995), the Depression Anxiety Stress Scale-21 (Lovibond & Lovibond, 1995), and the Quality of Life Enjoyment and Satisfaction Questionnaire (Endicott, Nee, Harrison, & Blumenthal, 1993). Cognitive symptom reporting was very high, even in the subgroup without a history of traumatic brain injury. In a regression analysis, cognitive symptom severity was independently associated with QOL (β = -.204). This relationship was not explained by comorbid traumatic brain injury, but was restricted to patients with comorbid depression (β = -.278 in the subgroup with an elevated Depression Anxiety Stress Scale-21 Depression subscale; n = 91). In conclusion, perceived cognitive impairment was common in this PTSD sample and helped to explain impairments in QOL, especially in patients with comorbid depression.