Epidemiology of traumatic brain injury

Annexin-A1 tripeptide enhances functional recovery and mitigates brain damage in traumatic brain injury by inhibiting neuroinflammation and preventing ANXA1 nuclear translocation in mice

This study explores the role and mechanism of Annexin-A1 Tripeptide (ANXA1sp) in mitigating neuronal damage and promoting functional recovery in a mouse model of traumatic brain injury (TBI). Our goal is to identify ANXA1sp as a potential therapeutic drug candidate for TBI treatment. Adult male C57BL/6J mice were subjected to controlled cortical impact (CCI) to simulate TBI, supplemented by an in vitro model of glutamate-induced TBI in HT22 cells.  We assessed neurological deficits using the Modified Neurological Severity Score (mNSS), tested sensorimotor functions with beam balance and rotarod tests, and evaluated cognitive performance via the Morris water maze. Neuronal damage was quantified using Nissl and TUNEL staining, while microglial activation and inflammatory responses were measured through immunostaining, quantitative PCR (qPCR), Western blotting, and ELISA. Additionally, we evaluated cell viability in response to glutamate toxicity using the Cell Counting Kit-8 (CCK-8) assay and lactate dehydrogenase (LDH) release. Intraperitoneal administration of ANXA1sp significantly enhanced neurological outcomes, markedly reducing sensorimotor and cognitive impairments caused by TBI. This treatment resulted in a significant reduction in lesion volume and decreased neuronal cell death in the ipsilateral cortex. Moreover, ANXA1sp effectively diminished microglial activation around the brain lesion and decreased the levels of pro-inflammatory markers such as IL-6, IL-1β, TNF-α, and TGF-β in the cortex, indicating a significant reduction in neuroinflammation post-TBI. ANXA1sp also offered protection against neuronal cell death induced by glutamate toxicity, primarily by inhibiting the nuclear translocation of ANXA1, highlighting its potential as a neuroprotective strategy in TBI management. Administration of ANXA1sp significantly reduced neuroinflammation and neuronal cell death, primarily by blocking the nuclear translocation of ANXA1. This treatment substantially reduced brain damage and improved neurological functional recovery after TBI. Consequently, ANXA1sp stands out as a promising neuroprotective agent for TBI therapy.

Ten Priorities for Research Addressing the Intersections of Brain Injury, Mental Health and Addictions: A Stakeholder-Driven Priority-Setting Study

OBJECTIVES

The purpose of this study was to engage key stakeholders in a health research priority-setting process to identify, prioritize and produce a community-driven list of research questions addressing intersectional issues on mental health and addictions (MHA) in acquired brain injury (ABI).

METHODS

A multiphasic health research priority-setting process was co-designed and executed with community-based stakeholders, including researchers, health professionals, clinicians, service providers, representatives from brain injury associations, policy makers and people with lived experience of ABI and MHA, including patients and their family members. Stakeholders' ideas led to the generation of research questions, which were prioritized at a 1-day workshop.

RESULTS

Fifty-nine stakeholders participated in the priority-setting activity during the workshop, which resulted in a rank-ordered list of the top 10 questions for research addressing the intersections of ABI and MHA. Questions identified touched on several pressing issues (e.g., opioid crisis, homelessness), encompassed multiple subtypes of ABI (e.g., hypoxic-ischaemic, mild traumatic), and involved different domains (e.g., identification, intervention) of health research.

CONCLUSIONS

This community-driven health research priority-setting study identified and prioritized research questions addressing the intersections of ABI and MHA. Researchers and funding agencies should use this list to inform their agendas and address stakeholders' most urgent needs, fostering meaningful improvements to clinical services.

PATIENT OR PUBLIC CONTRIBUTION

An 11-person working group comprised of people with lived experience, service providers, researchers, healthcare professionals and other key stakeholders collaboratively developed and informed the scope, design, methodology and interpretation of this study. Over 50 community-based stakeholders contributed to the research priority-setting activity. One co-author is a person with lived experience.

Mitigating Traumatic Brain Injury: A Narrative Review of Supplementation and Dietary Protocols

Traumatic brain injuries (TBIs) constitute a significant public health issue and a major source of disability and death in the United States and worldwide. TBIs are strongly associated with high morbidity and mortality rates, resulting in a host of negative health outcomes and long-term complications and placing a heavy financial burden on healthcare systems. One promising avenue for the prevention and treatment of brain injuries is the design of TBI-specific supplementation and dietary protocols centred around nutraceuticals and biochemical compounds whose mechanisms of action have been shown to interfere with, and potentially alleviate, some of the neurophysiological processes triggered by TBI. For example, evidence suggests that creatine monohydrate and omega-3 fatty acids (DHA and EPA) help decrease inflammation, reduce neural damage and maintain adequate energy supply to the brain following injury. Similarly, melatonin supplementation may improve some of the sleep disturbances often experienced post-TBI. The scope of this narrative review is to summarise the available literature on the neuroprotective effects of selected nutrients in the context of TBI-related outcomes and provide an evidence-based overview of supplementation and dietary protocols that may be considered in individuals affected by-or at high risk for-concussion and more severe head traumas. Prophylactic and/or therapeutic compounds under investigation include creatine monohydrate, omega-3 fatty acids, BCAAs, riboflavin, choline, magnesium, berry anthocyanins, Boswellia serrata, enzogenol, N-Acetylcysteine and melatonin. Results from this analysis are also placed in the context of assessing and addressing important health-related and physiological parameters in the peri-impact period such as premorbid nutrient and metabolic health status, blood glucose regulation and thermoregulation following injury, caffeine consumption and sleep behaviours. As clinical evidence in this research field is rapidly emerging, a comprehensive approach including appropriate nutritional interventions has the potential to mitigate some of the physical, neurological, and emotional damage inflicted by TBIs, promote timely and effective recovery, and inform policymakers in the development of prevention strategies.

Daidzin Improves Neurobehavioral Outcome in Rat Model of Traumatic Brain Injury

Traumatic brain injury (TBI) is associated with the etiology of multiple neurological disorders, including neurodegeneration, leading to various cognitive deficits. Daidzin (obtained from kudzu root and soybean leaves) is known for its neuroprotective effects through multiple mechanisms. This study aimed to investigate the pharmacological effects of Daidzin on sensory, and biochemical parameters, cognitive functions, anxiety, and depressive-like behaviors in the TBI rat model. Rats were divided into four groups (Control, TBI, TBI + Ibuprofen (30mg/kg), and TBI + Daidzin (5mg/kg)). Rats were subjected to TBI by dropping a 200g rod from a height of 26cm, resulting in an impact force of 0.51J on the exposed crania. Ibuprofen (30mg/kg) was used as a positive control reference/standard drug and Daidzin (5mg/kg) as the test drug. Neurological severity score (NSS) assessment was done to determine the intactness of sensory and motor responses. Brain tissue edema and acetylcholine levels were determined in the cortex and hippocampus. Cognitive functions such as hippocampus-dependent memory, novel object recognition, exploration, depressive and anxiety-like behaviors were measured. Treatment with Daidzin improved NSS, reduced hippocampal and cortical edema, and improved levels of acetylcholine in TBI-induced rats. Furthermore, Daidzin treatment improved hippocampus-dependent memory, exploration behavior, and novel object recognition while reducing depressive and anxiety-like behavior. Our study revealed that Daidzin has a therapeutic potential comparable to Ibuprofen and can offer neuroprotection and enhanced cognitive and behavioral outcomes in rats after TBI.

Traumatic brain injury incidence and mortality: a large population-based study

BACKGROUND

Traumatic brain injury (TBI) is a severe condition that represents a major global public health concern.

OBJECTIVES

Provide a comprehensive epidemiological outlook encompassing TBI incidence, healthcare provision and mortality.

METHODS

Population-based study in Veneto (4.9 million inhabitants), Italy, from 2012 to 2021. Hospital discharge and mortality records were used to assess incidence and mortality. Kaplan-Meier survival estimator and Cox regression models were fitted to investigate determinants of mortality.

RESULTS

Between 2012 and 2021, there were 37,487 incident TBI cases, corresponding to an age-standardized rate of 77.30/100,000 people (95% CI 76.52-78.09), higher among males, with an exponential growth after age 70. Leading causes were domestic (33.1%) and traffic accidents (17.7%), the first predominating among the elderly and children, while the latter in males 15-24 and older people. After rates stably declined between 2012 and 2019, the study captured a sharp decrease especially for traffic and occupational accidents in males, due to COVID-19 lockdown in 2020. Overall, 48.9% TBI patients were hospitalized in a specialized trauma center, with 2.6% requiring a transfer after accessing a spoke hospital. Over a 3.7 years median follow-up, 16,145 deaths were recorded, with higher mortality for those undergoing neurosurgical interventions, regardless of their access point. Risks of death increased with age, male gender, and comorbidities.

DISCUSSION

TBI incidence is characterized by distinct patterns, affecting particularly older individuals and males. Minimal hospital transfers with comparable survival irrespective of access point suggests an effective patient management within the network. The study underscores the critical need for acute-phase support and prolonged care strategies for older TBI patients.

Sleep fragmentation after traumatic brain injury impairs behavior and conveys long-lasting impacts on neuroinflammation

Traumatic brain injury (TBI) causes a prolonged inflammatory response in the central nervous system (CNS) driven by microglia. Microglial reactivity is exacerbated by stress, which often provokes sleep disturbances. We have previously shown that sleep fragmentation (SF) stress after experimental TBI increases microglial reactivity and impairs hippocampal function 30 days post-injury (DPI). The neuroimmune response is highly dynamic the first few weeks after TBI, which is also when injury induced sleep-wake deficits are detected. Therefore, we hypothesized that even a few weeks of TBI SF stress would synergize with injury induced sleep-wake deficits to promote neuroinflammation and impair outcome. Here, we investigated the effects of environmental SF in a lateral fluid percussion model of mouse TBI. Half of the mice were undisturbed, and half were exposed to 5 h of SF around the onset of the light cycle, daily, for 14 days. All mice were then undisturbed 15-30 DPI, providing a period for SF stress recovery (SF-R). Mice exposed to SF stress slept more than those in control housing 7-14 DPI and engaged in more total daily sleep bouts during the dark period. However, SF stress did not exacerbate post-TBI sleep deficits. Testing in the Morris water maze revealed sex dependent differences in spatial reference memory 9-14 DPI with males performing worse than females. Post-TBI SF stress suppressed neurogenesis-related gene expression and increased inflammatory signaling in the cortex at 14 DPI. No differences in sleep behavior were detected between groups during the SF stress recovery period 15-30 DPI. Microscopy revealed cortical and hippocampal IBA1 and CD68 percent-area increased in TBI SF-R mice 30 DPI. Additionally, neuroinflammatory gene expression was increased, and synaptogenesis-related gene expression was suppressed in TBI-SF mice 30 DPI. Finally, IPA canonical pathway analysis showed post-TBI SF impaired and delayed activation of synapse-related pathways between 14 and 30 DPI. These data show that transient SF stress after TBI impairs recovery and conveys long-lasting impacts on neuroimmune function independent of continuous sleep deficits. Together, these finding support that even limited exposure to post-TBI SF stress can have lasting impacts on cognitive recovery and regulation of the immune response to trauma.

Platelet-to-lymphocyte ratio as a prognostic predictive marker on adults with traumatic brain injury: Systematic review

Background

The platelet-to-lymphocyte ratio (PLR) has emerged as a prognostic predictive marker in various diseases, but its role in traumatic brain injury (TBI) has not been fully elucidated. This study aims to evaluate the role of PLR as a prognostic predictive marker in adults with TBI.

Methods

This systematic review was conducted according to the Preferred Reporting Items in the Systematic Review and Meta-analysis Guidelines 2020. A comprehensive search was performed using PubMed, Google Scholar, Scopus, Crossref, OpenAlex, Semantic Scholar, Library of Congress, and Jisc Library Hub Discover database to identify relevant studies published up to February 2023. Both prospective and retrospective observational studies written in English or Indonesian were included in the study. No restrictions were placed on the year and country of publication and duration of follow-up. Study quality was evaluated using the Newcastle-Ottawa Scale (NOS), and the risk of bias was estimated using the Cochrane Risk of Bias Assessment Tool for Nonrandomized Research (Ro-BANS) tool. A narrative synthesis was also conducted to summarize the findings.

Results

We retrieved 1644 references using the search strategy, and 1623 references were excluded based on screening the title and abstract. The full text was retrieved for 20 articles and subjected to the eligibility criteria, of which 16 were excluded from the study. Four papers with a total of 1.467 sample sizes were included in the review. The median of NOS for study quality was 8-9, with the risk of selection bias using the Ro-BANS tool being low in all studies except for the blinding outcome assessments, which are all unclear. The study finding suggests that the PLR has the potential as an independent prognostic predictive marker in adult patients with TBI. In three studies, a high level of admission PLR may independently predict an increasing mortality risk in 30 days and adverse outcomes measured by the Glasgow outcome scale in 6 months following TBI. However, one study shows that PLR may have limited value as a predictor of mortality or favorable neurological outcomes compared to other hematological parameters. Further studies were needed to establish the clinical utility of PLR and fill the present gaps.

Conclusion

This systematic review provides evidence supporting the utilization of PLR as a prognostic predictive marker in adult patients with TBI. The PLR can mainly be utilized, especially in rural practice, as PLR is a simple, low-cost, and routinely performed hematological examination.

Effect of PCC on outcomes of severe traumatic brain injury patients on preinjury anticoagulation

INTRODUCTION

This study aims to evaluate effect of 4-factor PCC on outcomes of severe TBI patients on preinjury anticoagulants undergoing craniotomy/craniectomy.

METHODS

In this analysis of 2018-2020 ACS-TQIP, patients with isolated blunt severe TBI (Head-AIS≥3, nonhead-AIS<2) using preinjury anticoagulants who underwent craniotomy/craniectomy were identified and stratified into PCC and No-PCC groups. Outcomes were time to surgery and mortality. Multivariable binary logistic and linear regression analyses were performed.

RESULTS

1598 patients were identified (PCC-107[7 %], No-PCC-1491[93 %]). Mean age was 74(11) years, 65 % were male, median head AIS was 4. Median time to PCC administration was 109 ​min. On univariable analysis, PCC group had shorter time to surgery (PCC-341, No-PCC-620 ​min, p ​= ​0.002), but higher mortality (PCC35 %, No-PCC21 %,p ​= ​0.001). On regression analysis, PCC was independently associated with shorter time to surgery (β ​= ​-1934,95 %CI ​= ​-3339to-26), but not mortality (aOR ​= ​0.70,95 %CI ​= ​0.14-3.62).

CONCLUSION

PCC may be a safe adjunct for urgent reversal of coagulopathy in TBI patients using preinjury anticoagulants.

The Cumulative Incidence of Post-Traumatic Epilepsy After Mild Traumatic Brain Injury: A Systematic Review and Individual Participant Data Meta-Analysis Protocol

A precise understanding of the latency to post-traumatic epilepsy (PTE) following a traumatic brain injury (TBI) is necessary for optimal patient care. This precision is currently lacking despite a surprising number of available data sources that could address this pressing need. Following guidance from the Cochrane Collaboration and Joanna Briggs Institute, we conduct a systematic review to address the research questions: What is the cumulative incidence of PTE following mild TBI (mTBI; concussion), and what is the distribution of the latency to onset? We designed a comprehensive search of medical databases and gray literature sources. Citations will be screened on both abstract and full-text levels, independently and in duplicate. Studies will be evaluated for risk of bias independently and in duplicate using published instruments specific to incidence/prevalence studies. Data will be abstracted independently and in duplicate using piloted extraction forms. Disagreements will be resolved by consensus or third-party adjudication. Evidence synthesis will involve pairwise and individual participant data meta-analysis with heterogeneity explored via a set of predetermined subgroups. The robustness of the findings will be subjected to sensitivity analyses based on the risk of bias, outlier studies, and mTBI definitional criteria. The overall certainty in the estimates will be reported using GRADE (Grading of Recommendations, Assessment, Development, and Evaluations). This protocol presents an innovative and impactful approach to build on the growing body of knowledge surrounding post-mTBI PTE. Through a precise understanding of the latency period, this study can contribute to early detection, tailored interventions, and improved outcomes, leading to a substantial impact on patient care and quality of life.

Diversity trends in traumatic brain injury clinical trials in the United States

BACKGROUND

This study aims to understand the demographic representation of patients in Traumatic Brain Injury (TBI) clinical trials by evaluating the proportions of patients from various demographic categories amongst completed TBI clinical trials in the United States.

METHODS

ClinicalTrials.gov was queried for active TBI clinical trials. One hundred and eight completed trials in the United States were selected based on inclusion criteria, and information regarding intervention, setting, age, sex, race, and ethnicity was extracted. 2002-2006 TBI incidence data was obtained from the CDC. Chi-squared testing was applied to analyze the relationship between distributions of race and sex in the collected clinical trials and the national TBI data, and logistic regression was conducted to identify variables that may predict reporting of race or ethnicity.

RESULTS

About 53.7% of selected clinical trials reported racial data and 34.3% reported ethnicity data. Logistic regression identified that clinical trials in defined phases were more likely to report racial data (p = 0.047 [1.015, 9.603]).

CONCLUSION

Current TBI trials do not consistently report race or ethnicity data. Future efforts to ensure equitable representation in clinical trials may involve reform of recruitment processes and accountability measures implemented within the grant application process to ensure proper racial and ethnicity data reporting.

Traumatic Brain Injury: A Comprehensive Review of Biomechanics and Molecular Pathophysiology

Traumatic brain injury (TBI) is a critical public health concern with profound consequences for affected individuals. This comprehensive literature review delves into TBI intricacies, encompassing primary injury biomechanics and the molecular pathophysiology of the secondary injury cascade. Primary TBI involves a complex interplay of forces, including impact loading, blast overpressure, and impulsive loading, leading to diverse injury patterns. These forces can be categorized into inertial (e.g., rotational acceleration causing focal and diffuse injuries) and contact forces (primarily causing focal injuries like skull fractures). Understanding their interactions is crucial for effective injury management. The secondary injury cascade in TBI comprises multifaceted molecular and cellular responses, including altered ion concentrations, dysfunctional neurotransmitter networks, oxidative stress, and cellular energy disturbances. These disruptions impair synaptic function, neurotransmission, and neuroplasticity, resulting in cognitive and behavioral deficits. Moreover, neuroinflammatory responses play a pivotal role in exacerbating damage. As we endeavor to bridge the knowledge gap between biomechanics and molecular pathophysiology, further research is imperative to unravel the nuanced interplay between mechanical forces and their consequences at the molecular and cellular levels, ultimately guiding the development of targeted therapeutic strategies to mitigate the debilitating effects of TBI. In this study, we aim to provide a concise review of the bridge between biomechanical processes causing primary injury and the ensuing molecular pathophysiology of secondary injury, while detailing the subsequent clinical course for this patient population. This knowledge is crucial for advancing our understanding of TBI and developing effective interventions to improve outcomes for those affected.

Establishing a 3-Tesla Magnetic Resonance Imaging Method for Assessing Diffuse Axonal Brain Injury in Rats

Traumatic brain injury (TBI) significantly contributes to death and disability worldwide. However, treatment options remain limited. Here, we focus on a specific pathology of TBI, diffuse axonal brain injury (DABI), which describes the process of the tearing of nerve fibers in the brain after blunt injury. Most protocols to study DABI do not incorporate a specific model for that type of pathology, limiting their ability to identify mechanisms and comorbidities of DABI. In this study, we developed a magnetic resonance imaging (MRI) protocol for DABI in a rat model using a 3-T clinical scanner. We compared the neuroimaging outcomes with histologic and neurologic assessments. In a sample size of 10 rats in the sham group and 10 rats in the DABI group, we established neurological severity scores before the intervention and at 48 h following DABI induction. After the neurological evaluation after DABI, all rats underwent MRI scans and were subsequently euthanized for histological evaluation. As expected, the neurological assessment showed a high sensitivity for DABI lesions indicated using the β-APP marker. Surprisingly, however, we found that the MRI method had greater sensitivity in assessing DABI lesions compared to histological methods. Out of the five MRI parameters with pathological changes in the DABI model, we found significant changes compared to sham rats in three parameters, and, as shown using comparative tests with other models, MRI was the most sensitive parameter, being even more sensitive than histology. We anticipate that this DABI protocol will have a significant impact on future TBI and DABI studies, advancing research on treatments specifically targeted towards improving patient quality of life and long-term outcomes.

Cytokine Release by Microglia Exposed to Neurologic Injury Is Amplified by Lipopolysaccharide

INTRODUCTION

Traumatic brain injury (TBI) is a leading cause of death and morbidity in the trauma population. Microglia drive the secondary neuroinflammatory response after TBI. We sought to determine if the microglial response to neurologic injury was exacerbated by a second stimulus after exposure to neurologic injury.

METHODS

Sprague-Dawley rats (age 2-3 wk) were divided into injured and noninjured groups. Injured rats underwent a controlled cortical impact injury; noninjured rats remained naïve to any injury and served as the control group. Primary rat microglia were isolated and applied to in vitro cultures. After incubation for 24 h, the microglia were stimulated with lipopolysaccharide (LPS) or norepinephrine. Twenty-four hours after stimulation, cell culture supernatant was collected. Tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) production were measured by standard enzyme-linked immunosorbent assays. GraphPad Prism was used for statistical analysis.

RESULTS

When compared to noninjured microglia, LPS induced a significantly greater production of TNF-α in microglia isolated from the injured ipsilateral (versus noninjured = 938.8 ± 155.1, P < 0.0001) and injured contralateral hemispheres (versus noninjured = 426.6 ± 155.1, P < 0.0001). When compared to microglia from noninjured cerebral tissue, IL-6 production was significantly greater after LPS stimulation in the injured ipsilateral hemisphere (mean difference versus noninjured = 9540 ± 3016, P = 0.0101) and the contralateral hemisphere (16,700 ± 3016, P < 0.0001). Norepinephrine did not have a significant effect on IL-6 or TNF-α production.

CONCLUSIONS

LPS stimulation may amplify the release of proinflammatory cytokines from postinjury microglia. These data suggest that post-TBI complications, like sepsis, may propagate neuroinflammation by augmenting the proinflammatory response of microglia.

Mild Traumatic Brain Injury-Induced Augmented Postsurgical Pain Is Driven by Central Serotonergic Pain-Facilitatory Signaling

BACKGROUND

Individuals recovering from mild traumatic brain injury (mTBI) have increased rates of acute and chronic pain. However, the mechanism through which mTBI triggers heightened pain responses and the link between mTBI and postsurgical pain remain elusive. Recent data suggest that dysregulated serotonergic pain-modulating circuits could be involved. We hypothesized that mTBI triggers dysfunction in descending serotonergic pain modulation, which exacerbates acute pain and delays pain-related recovery after surgery.

METHODS

Using mouse models of mTBI and hindpaw incision for postsurgical pain in C57BL/6J mice, mechanical withdrawal thresholds were assessed throughout the postsurgical period. To determine whether mTBI leads to persistent alteration of endogenous opioid tone, mu-opioid receptors (MORs) were blocked with naloxone. Finally, the role of descending serotonergic signaling on postsurgical allodynia in animals with mTBI was examined using ondansetron (5-HT 3 receptor antagonist) or a serotonin-specific neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT), to ablate descending serotonergic fibers. The treatment effects on withdrawal thresholds were normalized to baseline (percentage of maximum possible effect, MPE%), and analyzed using paired t -test or 2-way repeated-measures ANOVA with post hoc multiple comparisons.

RESULTS

Post-mTBI mice demonstrated transient allodynia in hindpaws contralateral to mTBI, while no nociceptive changes were observed in sham-mTBI animals (mean difference, MD, MPE%, post-mTBI day 3: -60.9; 95% CI, -88.7 to -35.0; P < .001). After hindpaw incision, animals without mTBI exhibited transient allodynia, while mice with prior mTBI demonstrated prolonged postsurgical allodynia (MD-MPE% postsurgical day 14: -65.0; 95% CI, -125.4 to -4.5; P = .04). Blockade of MORs using naloxone transiently reinstated allodynia in mTBI animals but not in sham-mTBI mice (MD-MPE% post-naloxone: -69.9; 95% CI, -94.8 to -45.1; P < .001). Intrathecal administration of ondansetron reversed the allodynia observed post-mTBI and postincision in mTBI mice (compared to vehicle-treated mTBI mice, MD-MPE% post-mTBI day 3: 82.7; 95% CI, 58.5-106.9; P < .001; postsurgical day 17: 62.5; 95% CI, 38.3-86.7; P < .001). Both the acute allodynia after TBI and the period of prolonged allodynia after incision in mTBI mice were blocked by pretreatment with 5,7-DHT (compared to sham-mTBI mice, MD-MPE% post-mTBI day 3: 0.5; 95% CI, -18.5 to 19.5; P = .99; postsurgical day 14: -14.6; 95% CI, -16.7 to 45.9; P = .48). Similar behavioral patterns were observed in hindpaw ipsilateral to mTBI.

CONCLUSIONS

Collectively, our results show that descending serotoninergic pain-facilitating signaling is responsible for nociceptive sensitization after mTBI and that central endogenous opioid tone opposes serotonin's effects. Understanding brain injury-related changes in endogenous pain modulation may lead to improved pain control for those with TBI undergoing surgery.

Prevalence of fatigue and cognitive impairment after traumatic brain injury

BACKGROUND

Following traumatic brain injury (TBI) some patients develop lingering comorbid symptoms of fatigue and cognitive impairment. The mild cognitive impairment self-reported by patients is often not detected with neurocognitive tests making it difficult to determine how common and severe these symptoms are in individuals with a history of TBI. This study was conducted to determine the relative prevalence of fatigue and cognitive impairment in individuals with a history of TBI.

METHODS

The Fatigue and Altered Cognition Scale (FACs) digital questionnaire was used to assess self-reported fatigue and cognitive impairment. Adults aged 18-70 were digitally recruited for the online anonymous study. Eligible participants provided online consent, demographic data, information about lifetime TBI history, and completed the 20 item FACs questionnaire.

RESULTS

A total of 519 qualifying participants completed the online digital study which included 204 participants with a history of TBI of varied cause and severity and 315 with no history of TBI. FACs Total Score was significantly higher in the TBI group (57.7 ± 22.2) compared to non-TBI (39.5 ± 23.9; p<0.0001) indicating more fatigue and cognitive impairment. When stratified by TBI severity, FACs score was significantly higher for all severity including mild (53.9 ± 21.9, p<0.0001), moderate (54.8 ± 24.4, p<0.0001), and severe (59.7 ± 20.9, p<0.0001) TBI. Correlation analysis indicated that more severe TBI was associated with greater symptom severity (p<0.0001, r = 0.3165). Ancillary analysis also suggested that FACs scores may be elevated in participants with prior COVID-19 infection but no history of TBI.

CONCLUSIONS

Adults with a history of even mild TBI report significantly greater fatigue and cognitive impairment than those with no history of TBI, and symptoms are more profound with greater TBI severity.

Context is key: glucocorticoid receptor and corticosteroid therapeutics in outcomes after traumatic brain injury

Traumatic brain injury (TBI) is a global health burden, and survivors suffer functional and psychiatric consequences that can persist long after injury. TBI induces a physiological stress response by activating the hypothalamic-pituitary-adrenal (HPA) axis, but the effects of injury on the stress response become more complex in the long term. Clinical and experimental evidence suggests long lasting dysfunction of the stress response after TBI. Additionally, pre- and post-injury stress both have negative impacts on outcome following TBI. This bidirectional relationship between stress and injury impedes recovery and exacerbates TBI-induced psychiatric and cognitive dysfunction. Previous clinical and experimental studies have explored the use of synthetic glucocorticoids as a therapeutic for stress-related TBI outcomes, but these have yielded mixed results. Furthermore, long-term steroid treatment is associated with multiple negative side effects. There is a pressing need for alternative approaches that improve stress functionality after TBI. Glucocorticoid receptor (GR) has been identified as a fundamental link between stress and immune responses, and preclinical evidence suggests GR plays an important role in microglia-mediated outcomes after TBI and other neuroinflammatory conditions. In this review, we will summarize GR-mediated stress dysfunction after TBI, highlighting the role of microglia. We will discuss recent studies which target microglial GR in the context of stress and injury, and we suggest that cell-specific GR interventions may be a promising strategy for long-term TBI pathophysiology.

The Effect of Dexamethasone on Neuroinflammation and Cerebral Edema in Rats With Traumatic Brain Injury Combined With Seawater Drowning

OBJECTIVE

To investigate the effect and mechanism of dexamethasone (DX) on axonal injury after traumatic brain injury (TBI) combined with seawater drowning (SWD) in rats.

METHODS

To gain an in-depth understanding of TBI + SWD in rats, we established the compound injury model of rats by the Marmarou method and intratracheal pumping of seawater to simulate the pathological conditions. Rats in the DX group received intraperitoneal injections of DX (1 mg/kg) immediately after injury, and rats in the sham group and TBI + SWD group received intraperitoneal injections of the same amount of normal saline.

RESULTS

Hematoxylin-eosin (HE) showed that DX improved matrix looseness, cell swelling, and nuclear condensation 168 hours after injury. Immunohistochemistry (IHC) staining showed that the protein expression of AQP4 was decreased in the DX group compared with the TBI + SWD group from 12 hours to 168 hours after injury. DX decreased the modified neurological severity score (mNSS) significantly at 24 hours and 168 hours after injury (P < 0.05). At 72 h and 168 h after injury, DX significantly lowered the expressions of IL-8 and TNF-α (P < 0.05).

CONCLUSION

DX may play a neuroprotective role by reducing cerebral edema and inflammatory response after TBI + SWD injury in rats.

A Perspective on Hormonal Contraception Usage in Central Nervous System Injury

Naturally occurring life stages in women are associated with changes in the milieu of endogenous ovarian hormones. Women of childbearing age may be exposed to exogenous ovarian hormone(s) because of their use of varying combinations of estrogen and progesterone hormones-containing oral contraceptives (OC; also known as "the pill"). If women have central nervous system (CNS) injury such as spinal cord injury (SCI) and traumatic brain injury (TBI) during their childbearing age, they are likely to retain their reproductive capabilities and may use OC. Many deleterious side effects of long-term OC use have been reported, such as aberrant blood clotting and endothelial dysfunction that consequently increase the risk of myocardial infarction, venous thromboembolism, and ischemic brain injury. Although controversial, studies have suggested that OC use is associated with neuropsychiatric ramifications, including uncontrollable mood swings and poorer cognitive performance. Our understanding about how the combination of endogenous hormones and OC-conferred exogenous hormones affect outcomes after CNS injuries remains limited. Therefore, understanding the impact of OC use on CNS injury outcomes needs further investigation to reveal underlying mechanisms, promote reporting in clinical or epidemiological studies, and raise awareness of possible compounded consequences. The goal of the current review is to discuss the impacts of CNS injury on endogenous ovarian hormones and vice-versa, as well as the putative consequences of exogenous ovarian hormones (OC) on the CNS to identify potential gaps in our knowledge to consider for future laboratory, epidemiological, and clinical studies.

Effect of low fibrinogen level on in-hospital mortality and 6-month functional outcome of TBI patients, a single center experience

In patients affected by traumatic brain injury (TBI), hypofibrinogenemia within the initial hours of trauma can be expected due to vascular and inflammatory changes. In this study, we aimed to evaluate the effect of hypofibrinogenemia on the in-hospital mortality and 6-month functional outcomes of TBI patients, admitted to Rajaee Hospital, a referral trauma center in Shiraz, Iran. This study included all TBI patients admitted to our center who had no prior history of coagulopathy or any systemic disease, were alive on arrival, and had not received any blood product before admission. On admission, hospitalization, imaging, and 6-month follow-up information of included patients were extracted from the TBI registry database. The baseline characteristics of patients with fibrinogen levels of less than 150 mg/dL were compared with the cases with higher levels. To assess the effect of low fibrinogen levels on in-hospital mortality, a uni- and multivariate was conducted between those who died in hospital and survivors. Based on the 6-month GOSE score of patients, those with GOSE < 4 (unfavorable outcome) were compared with those with a favorable outcome. A total of 3049 patients (84.3% male, 15.7% female), with a mean age of 39.25 ± 18.87, met the eligibility criteria of this study. 494 patients had fibrinogen levels < 150 mg/dl, who were mostly younger and had lower average GCS scores in comparison to cases with higher fibrinogen levels. By comparison of the patients who died during hospitalization and survivors, it was shown that fibrinogen < 150 mg/dl is among the prognostic factors for in-hospital mortality (OR:1.75, CI: 1.32:2.34, P-value < 0.001), while the comparison between patients with the favorable and unfavorable functional outcome at 6-month follow-up, was not in favor of prognostic effect of low fibrinogen level (OR: 0.80, CI: 0.58: 1.11, P-value: 0.19). Hypofibrinogenemia is associated with in-hospital mortality of TBI patients, along with known factors such as higher age and lower initial GCS score. However, it is not among the prognostic factors of midterm functional outcome.

Sex-Biased Expression and Response of microRNAs in Neurological Diseases and Neurotrauma

Neurological diseases and neurotrauma manifest significant sex differences in prevalence, progression, outcome, and therapeutic responses. Genetic predisposition, sex hormones, inflammation, and environmental exposures are among many physiological and pathological factors that impact the sex disparity in neurological diseases. MicroRNAs (miRNAs) are a powerful class of gene expression regulator that are extensively involved in mediating biological pathways. Emerging evidence demonstrates that miRNAs play a crucial role in the sex dimorphism observed in various human diseases, including neurological diseases. Understanding the sex differences in miRNA expression and response is believed to have important implications for assessing the risk of neurological disease, defining therapeutic intervention strategies, and advancing both basic research and clinical investigations. However, there is limited research exploring the extent to which miRNAs contribute to the sex disparities observed in various neurological diseases. Here, we review the current state of knowledge related to the sexual dimorphism in miRNAs in neurological diseases and neurotrauma research. We also discuss how sex chromosomes may contribute to the miRNA sexual dimorphism phenomenon. We attempt to emphasize the significance of sexual dimorphism in miRNA biology in human diseases and to advocate a gender/sex-balanced science.

The effect of processing speed on verbal and visual memory of adults with a chronic acquired brain injury

OBJECTIVE

Memory problems are among the most frequently reported cognitive complaints by individuals with an acquired brain injury (ABI). Processing speed and working memory deficits are often the result of ABI. These cognitive deficits significantly impact the acquisition and retention of information necessary for memory formation. This study investigated the influence of processing speed and working memory on immediate and delayed recall for verbal and visual memory, as well as overall memory recall in adults living with a chronic ABI.

METHODS

Sixty-three participants living with a chronic ABI, who were at least one-year post-injury, were cognitively assessed with the CNS-Vital Signs (CNS-VS) computerized cognitive battery and Wechsler Test of Adult Reading.

RESULTS

The CNS-VS Processing Speed significantly predicted delayed recall for verbal memory and overall memory performance. The CNS-VS Working Memory was not a significant predictor of memory recall.

CONCLUSIONS

Processing speed deficits negatively impact memory in individuals with a chronic ABI. These findings suggest the memory recall of adults with a chronic ABI is associated with poor processing speed and poor acquisition of information. Therefore, cognitive rehabilitation that improves processing speed should be the focus for individuals with ABI to improve memory performance as well as impaired processing speed.

Work-related and non-work-related mild traumatic brain injury: Associations with mental health and substance use challenges in a Canadian population-level survey

BACKGROUND

Mild traumatic brain injury (mTBI) can profoundly impact overall health, employment, and family life. Incidence of mTBI in the workplace represents an important subgroup with poorer outcomes. Mental health (MH) and substance use (SU) challenges are a primary correlate of TBI, but are rarely assessed among individuals with a work-related (wr)-mTBI, particularly at a population-level.

OBJECTIVE

This study aimed to assess the association between lifetime wr-mTBI and non-wr-mTBI and the experience of MH and SU challenges.

METHODS

The 2019 Centre for Addiction and Mental Health (CAMH) Monitor is a cross-sectional telephone survey of adults aged≥18 years in Ontario, Canada, employing a stratified (six regions) two-stage (telephone number, respondent) list-assisted random digit dialing probability selection procedure (N = 1792). Adjusting for sociodemographic variables, binary logistic regression was conducted to assess the association between lifetime wr-mTBI and non-wr-mTBI (relative to no TBI) and four outcomes: hazardous use of alcohol and of cannabis, psychological distress, and fair/poor mental health.

RESULTS

Adjusting for sociodemographic variables, non-wr-mTBI demonstrated increased odds of hazardous alcohol (AOR = 2.12, 95% CI = 1.41, 3.19) and cannabis use (AOR = 1.61, 95% CI = 1.05, 2.45), psychological distress (AOR = 1.68, 95% CI = 1.14, 2.49), and fair/poor mental health (AOR = 1.70, 95% CI = 1.11, 2.59). Lifetime wr-mTBI demonstrated increased odds of reporting psychological distress (AOR = 3.40, 95% CI = 1.93, 5.97) and fair/poor mental health (AOR = 2.16, 95% CI = 1.12, 4.19) only.

CONCLUSIONS

Non-wr-mTBI was associated with both MH and SU, whereas wr-mTBI was associated with MH only. MH outcomes were more strongly associated with wr-mTBI than non-wr-mTBI. Physicians, employers, and insurers need to consider the potential association between wr-mTBI and MH, and provide care accordingly.

Amantadine for functional improvement in patients with traumatic brain injury: A systematic review with meta-analysis and trial sequential analysis

Introduction

TBIs contribute in over one-third of injury-related deaths with mortality rates as high as 50% in trauma centers serving the most severe TBI. The effect of TBI on mortality is about 10% across all ages. Amantadine hydrochloride is one of the most commonly prescribed medications for patients undergoing inpatient neurorehabilitation who have disorders of consciousness.6 It is a dopamine (DA) receptor agonist and a N-Methyl-D-aspartate (NMDA) receptor antagonist via dopamine release and dopamine reuptake inhibition. The current study will synthesize the current available evidence and show the effect of Amantadine in functional improvement after TBI.

Research question

Does Amantadine have an effect on functional improvement of TBI patients?

Material and methods

This systematic review included all randomized placebo-controlled trials that compare the use of Amantadine versus placebo for functional improvement of patients after TBI. Outcome measures included DRS, GCS and/or GOS scores.

Results

Three studies with a total of 281 patients were included in the quantitative analyses. GRADE assessments show that there was a high certainty of evidence for functional improvement in terms of DRS scores.

Discussion and conclusion

Evidence of this review show that the use of Amantadine may have a beneficial effect on functional outcome in moderate to severe traumatic brain injuries among adult patients. Given the still-limited body of knowledge, more relevant studies must be made exploring the impact of Amantadine therapies on promoting functional recovery within the brain injury rehabilitation care continuum, with the goals of achieving larger sample sizes and establishing the early- or later-treatment beneficial effects.

Fecal microbiota transplantation unveils sex-specific differences in a controlled cortical impact injury mouse model

Introduction

Contusion type of traumatic brain injury (TBI) is a major cause of locomotor disability and mortality worldwide. While post-TBI deleterious consequences are influenced by gender and gut dysbiosis, the sex-specific importance of commensal gut microbiota is underexplored after TBI. In this study, we investigated the impact of controlled cortical impact (CCI) injury on gut microbiota signature in a sex-specific manner in mice.

Methods

We depleted the gut microflora of male and female C57BL/6 mice using antibiotic treatment. Thereafter, male mice were colonized by the gut microbiota of female mice and vice versa, employing the fecal microbiota transplantation (FMT) method. CCI surgery was executed using a stereotaxic impactor (Impact One™). For the 16S rRNA gene amplicon study, fecal boli of mice were collected at 3 days post-CCI (dpi).

Results and discussion

CCI-operated male and female mice exhibited a significant alteration in the genera of Akkermansia, Alistipes, Bacteroides, Clostridium, Lactobacillus, Prevotella, and Ruminococcus. At the species level, less abundance of Lactobacillus helveticus and Lactobacillus hamsteri was observed in female mice, implicating the importance of sex-specific bacteriotherapy in CCI-induced neurological deficits. FMT from female donor mice to male mice displayed an increase in genera of Alistipes, Lactobacillus, and Ruminococcus and species of Bacteroides acidifaciens and Ruminococcus gnavus. Female FMT-recipient mice from male donors showed an upsurge in the genus Lactobacillus and species of Lactobacillus helveticus, Lactobacillus hamsteri, and Prevotella copri. These results suggest that the post-CCI neurological complications may be influenced by the differential gut microbiota perturbation in male and female mice.

Evaluating GCS and FOUR Score in Predicting Mortality of Traumatic Brain Injury Patients (TBI): A Prospective Study in a Tertiary Hospital of South Malabar

Objective

This study evaluated the full outline of Unresponsiveness (FOUR) score and Glasgow Coma Scale (GCS) to predict traumatic brain injury (TBI) outcomes.

Methods

Among 107 patients, FOUR and GCS grading systems analyzed emergency department patients within 24 hours. FOUR and GCS were assessed simultaneously. Patients were followed for 15 days/discharge/death to evaluate the results. Modified Rankin scores measured in-hospital mortality, morbidity, and stay.

Results

65.42% of patients were 25-65. 10% were under 25, and 25% were over 65. Patients were 81% male. Road traffic accidents (RTAs) (90%), falls (7.48%), and assaults (1.47%) caused TBI. 19.62% died. 85.7% of 21 non-survivors had GCS <5 and FOUR <4. GCS mortality sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 85.71%, 93.02%, 75, and 96.4 (P < 0.0001). FOUR score mortality sensitivity, specificity, PPV, and NPV were 85.71%, 96.51%, 85.7, and 96.5 (P < 0.0001). GCS and FOUR AUCs matched (P = 0.52). The unadjusted model reduced in-hospital mortality by 14% for every one point increase in GCS. Every 1-point FOUR score increase reduced in-hospital mortality by 40% in the unadjusted model. GCS and FOUR scored 0.9 Spearman.

Conclusion

The FOUR score was comparable in the prediction of mortality in these patients.

Impaired cortical neuronal homeostasis and cognition after diffuse traumatic brain injury are dependent on microglia and type I interferon responses

Neuropsychiatric complications including depression and cognitive decline develop in the years after traumatic brain injury (TBI), negatively affecting quality of life. Microglial and type 1 interferon (IFN-I) responses are associated with the transition from acute to chronic neuroinflammation after diffuse TBI in mice. Thus, the purpose of this study was to determine if impaired neuronal homeostasis and increased IFN-I responses intersected after TBI to cause cognitive impairment. Here, the RNA profile of neurons and microglia after TBI (single nucleus RNA-sequencing) with or without microglia depletion (CSF1R antagonist) was assessed 7 dpi. There was a TBI-dependent suppression of cortical neuronal homeostasis with reductions in CREB signaling, synaptogenesis, and synaptic migration and increases in RhoGDI and PTEN signaling (Ingenuity Pathway Analysis). Microglial depletion reversed 50% of TBI-induced gene changes in cortical neurons depending on subtype. Moreover, the microglial RNA signature 7 dpi was associated with increased stimulator of interferon genes (STING) activation and IFN-I responses. Therefore, we sought to reduce IFN-I signaling after TBI using STING knockout mice and a STING antagonist, chloroquine (CQ). TBI-associated cognitive deficits in novel object location and recognition (NOL/NOR) tasks at 7 and 30 dpi were STING dependent. In addition, TBI-induced STING expression, microglial morphological restructuring, inflammatory (Tnf, Cd68, Ccl2) and IFN-related (Irf3, Irf7, Ifi27) gene expression in the cortex were attenuated in STINGKO mice. CQ also reversed TBI-induced cognitive deficits and reduced TBI-induced inflammatory (Tnf, Cd68, Ccl2) and IFN (Irf7, Sting) cortical gene expression. Collectively, reducing IFN-I signaling after TBI with STING-dependent interventions attenuated the prolonged microglial activation and cognitive impairment.

Prediction of skull fractures in blunt force head traumas using finite element head models

Traumatic head injuries remain a leading cause of death and disability worldwide. Although skull fractures are one of the most common head injuries, the fundamental mechanics of cranial bone and its impact tolerance are still uncertain. In the present study, a strain-rate-dependent material model for cranial bone has been proposed and implemented in subject-specific Finite Element (FE) head models in order to predict skull fractures in five real-world fall accidents. The subject-specific head models were developed following an established image-registration-based personalization pipeline. Head impact boundary conditions were derived from accident reconstructions using personalized human body models. The simulated fracture lines were compared to those visible in post-mortem CT scans of each subject. In result, the FE models did predict the actual occurrence and extent of skull fractures in all cases. In at least four out of five cases, predicted fracture patterns were comparable to ones from CT scans and autopsy reports. The tensile material model, which was tuned to represent rate-dependent tensile data of cortical skull bone from literature, was able to capture observed linear fractures in blunt indentation loading of a skullcap specimen. The FE model showed to be sensitive to modeling parameters, in particular to the constitutive parameters of the cortical tables. Nevertheless, this study provides a currently lacking strain-rate dependent material model of cranial bone that has the capacity to accurately predict linear fracture patterns. For the first time, a procedure to reconstruct occurrences of skull fractures using computational engineering techniques, capturing the all-in-all fracture initiation, propagation and final pattern, is presented.

Biomaterials and Cell Therapy Combination in Central Nervous System Treatments

Current pharmacological and surgical therapies for the central nervous system (CNS) show a limited capacity to reduce the damage progression; that together with the intrinsic limited capability of the CNS to regenerate greatly reduces the hopes of recovery. Among all the therapies proposed, the tissue engineering strategies supplemented with therapeutic stem cells remain the most promising. Neural tissue engineering strategies are based on the development of devices presenting optimal physical, chemical, and mechanical properties which, once inserted in the injured site, can support therapeutic cells, limiting the effect of a hostile environment and supporting regenerative processes. Thus, this review focuses on the employment of hydrogel and nanofibrous scaffolds supplemented with stem cells as promising therapeutic tools for the central and peripheral nervous systems in preclinical and clinical applications.

Identification of clinically relevant patient endotypes in traumatic brain injury using latent class analysis

Traumatic brain injury (TBI) is a complex condition where heterogeneity impedes the advancement of care. Understanding the diverse presentations of TBI is crucial for personalized medicine. Our study aimed to identify clinically relevant patient endotypes in TBI using latent class analysis based on comorbidity data. We used the Medical Information Mart for Intensive Care III database, which includes 2,629 adult TBI patients. We identified five stable endotypes characterized by specific comorbidity profiles: Heart Failure and Arrhythmia, Healthy, Renal Failure with Hypertension, Alcohol Abuse, and Hypertension. Each endotype had distinct clinical characteristics and outcomes: The Heart Failure and Arrhythmia endotype had lower survival rates than the Renal Failure with Hypertension despite featuring fewer comorbidities overall. Patients in the Hypertension endotype had higher rates of neurosurgical intervention but shorter stays in contrast to the Alcohol Abuse endotype which had lower rates of neurosurgical intervention but significantly longer hospital stays. Both endotypes had high overall survival rates comparable to the Healthy endotype. Logistic regression models showed that endotypes improved the predictability of survival compared to individual comorbidities alone. This study validates clinical endotypes as an approach to addressing heterogeneity in TBI and demonstrates the potential of this methodology in other complex conditions.

Is lifetime traumatic brain injury a risk factor for mild cognitive impairment in veterans compared to non-veterans?

Background: Traumatic brain injury (TBI) is prevalent in veterans and may occur at any stages of their life (before, during, or after military service). This is of particular concern, as previous evidence in the general population has identified TBI as a strong risk factor for mild cognitive impairment (MCI), a known precursor of dementia.Objectives: This study aimed to investigate whether exposure to at least one TBI across the lifetime was a risk factor for MCI in ageing UK veterans compared to non-veterans.Method: This cross-sectional study comprised of data from PROTECT, a cohort study comprising UK veterans and non-veterans aged ≥ 50 years at baseline. Veteran and TBI status were self-reported using the Military Service History Questionnaire (MSHQ) and the Brain Injury Screening Questionnaire (BISQ), respectively. MCI was the outcome of interest, and was defined as subjective cognitive impairment and objective cognitive impairment.Results: The sample population comprised of veterans (n = 701) and non-veterans (n = 12,389). TBI was a significant risk factor for MCI in the overall sample (OR = 1.21, 95% CI 1.11-1.31) compared to individuals without TBI. The prevalence of TBI was significantly higher in veterans compared to non-veterans (69.9% vs 59.5%, p < .001). There was no significant difference in the risk of MCI between veterans with TBI and non-veterans with TBI (OR = 1.19, 95% CI 0.98-1.45).Conclusion: TBI remains an important risk factor for MCI, irrespective of veteran status. The clinical implications indicate the need for early intervention for MCI prevention after TBI.

Computed Tomography Overuse in Pediatric Minor Head Trauma: Insights from a Single-Center Experience

BACKGROUND

Minor head trauma is a common reason for emergency department visits in children, but many of these cases are not clinically significant. Despite established criteria for selecting patients who require computed tomography (CT), concerns about overuse of CT persist. This study aimed to determine the frequency of clinically important traumatic brain injury by retrospectively evaluating cranial CT scans in children categorized as very low risk for such injuries based on PECARN prediction rules.

MATERIALS AND METHODS

Cranial CT scans of 941 minor head trauma cases were assessed for the presence, type, and number of calvarial bone fractures. Concomitant bleeding and treatment approaches were also recorded.

RESULTS

Among 881 patients (93.6%), cranial CT scans did not reveal any lesions apart from soft tissue edema. None of the cases had clinically important traumatic brain injury or required neurosurgical intervention.

DISCUSSION AND CONCLUSION

The study demonstrated that 93.6% of cranial CT scans for pediatric minor head trauma were negative, indicating a concerningly high rate of CT overuse. Although prediction rules exist, their application in clinical practice is not always optimal. Given the principle of "first, do no harm," proper patient selection is crucial to avoid unnecessary exposure to ionizing radiation.

Utility of Early Magnetic Resonance Imaging to Enhance Outcome Prediction in Critically Ill Children with Severe Traumatic Brain Injury

BACKGROUND

Many children with severe traumatic brain injury (TBI) receive magnetic resonance imaging (MRI) during hospitalization. There are insufficient data on how different patterns of injury on early MRI inform outcomes.

METHODS

Children (3-17 years) admitted in 2010-2021 for severe TBI (Glasgow Coma Scale [GCS] score < 9) were identified using our site's trauma registry. We used multivariable modeling to determine whether the hemorrhagic diffuse axonal injury (DAI) grade and the number of regions with restricted diffusion (subcortical white matter, corpus callosum, deep gray matter, and brainstem) on MRI obtained within 7 days of injury were independently associated with time to follow commands and with Functional Independence Measure for Children (WeeFIM) scores at the time of discharge from inpatient rehabilitation. We controlled for the clinical variables age, preadmission cardiopulmonary resuscitation, pupil reactivity, motor GCS score, and fever (> 38 °C) in the first 12 h.

RESULTS

Of 260 patients, 136 (52%) underwent MRI within 7 days of injury at a median of 3 days (interquartile range [IQR] 2-4). Patients with early MRI were a median age of 11 years (IQR 7-14), 8 (6%) patients received cardiopulmonary resuscitation, 19 (14%) patients had bilateral unreactive pupils, the median motor GCS score was 1 (IQR 1-4), and 82 (60%) patients had fever. Grade 3 DAI was present in 46 (34%) patients, and restricted diffusion was noted in the corpus callosum in 75 (55%) patients, deep gray matter in 29 (21%) patients, subcortical white matter in 23 (17%) patients, and the brainstem in 20 (15%) patients. After controlling for clinical variables, an increased number of regions with restricted diffusion, but not hemorrhagic DAI grade, was independently associated with longer time to follow commands (hazard ratio 0.68, 95% confidence interval 0.53-0.89) and worse WeeFIM scores (estimate β - 4.67, 95% confidence interval - 8.33 to - 1.01).

CONCLUSIONS

Regional restricted diffusion on early MRI is independently associated with short-term outcomes in children with severe TBI. Multicenter cohort studies are needed to validate these findings and elucidate the association of early MRI features with long-term outcomes in children with severe TBI.

Identification of brain areas in mice with peak neural activity across the acute and persistent phases of post-traumatic headache

BACKGROUND

Post-traumatic headache is very common after a mild traumatic brain injury. Post-traumatic headache may persist for months to years after an injury in a substantial proportion of people. The pathophysiology underlying post-traumatic headache remains unknown but is likely distinct from other headache disorders. Identification of brain areas activated in acute and persistent phases of post-traumatic headache can provide insights into the underlying circuits mediating headache pain. We used an animal model of mild traumatic brain injury-induced post-traumatic headache and c-fos immunohistochemistry to identify brain regions with peak activity levels across the acute and persistent phases of post-traumatic headache.

METHODS

Male and female C57BL/6 J mice were briefly anesthetized and subjected to a sham procedure or a weight drop closed-head mild traumatic brain injury . Cutaneous allodynia was assessed in the periorbital and hindpaw regions using von Frey filaments. Immunohistochemical c-fos based neural activity mapping was then performed on sections from whole brain across the development of post-traumatic headache (i.e. peak of the acute phase at 2 days post- mild traumatic brain injury), start of the persistent phase (i.e. >14 days post-mild traumatic brain injury) or after provocation with stress (bright light). Brain areas with consistent and peak levels of c-fos expression across mild traumatic brain injury induced post-traumatic headache were identified and included for further analysis.

RESULTS

Following mild traumatic brain injury, periorbital and hindpaw allodynia was observed in both male and female mice. This allodynia was transient and subsided within the first 14 days post-mild traumatic brain injury and is representative of acute post-traumatic headache. After this acute post-traumatic headache phase, exposure of mild traumatic brain injury mice to a bright light stress reinstated periorbital and hindpaw allodynia for several hours - indicative of the development of persistent post-traumatic headache. Acute post-traumatic headache was coincident with an increase in neuronal c-fos labeling in the spinal nucleus of the trigeminal caudalis, primary somatosensory cortex, and the nucleus accumbens. Neuronal activation returned to baseline levels by the persistent post-traumatic headache phase in the spinal nucleus of the trigeminal caudalis and primary somatosensory cortex but remained elevated in the nucleus accumbens. In the persistent post-traumatic headache phase, coincident with allodynia observed following bright light stress, we observed bright light stress-induced c-fos neural activation in the spinal nucleus of the trigeminal caudalis, primary somatosensory cortex, and nucleus accumbens.

CONCLUSION

Examination of mild traumatic brain injury-induced changes in peak c-fos expression revealed brain regions with significantly increased neural activity across the acute and persistent phases of post-traumatic headache. Our findings suggest mild traumatic brain injury-induced post-traumatic headache produces neural activation along pain relevant pathways at time-points matching post-traumatic headache-like pain behaviors. These observations suggest that the spinal nucleus of the trigeminal caudalis, primary somatosensory cortex, and nucleus accumbens may contribute to both the induction and maintenance of post-traumatic headache.

Development and Validation of an XGBoost-Algorithm-Powered Survival Model for Predicting In-Hospital Mortality Based on 545,388 Isolated Severe Traumatic Brain Injury Patients from the TQIP Database

BACKGROUND

Traumatic brain injury (TBI) represents a significant global health issue; the traditional tools such as the Glasgow Coma Scale (GCS) and Abbreviated Injury Scale (AIS) which have been used for injury severity grading, struggle to capture outcomes after TBI.

AIM AND METHODS

This paper aims to implement extreme gradient boosting (XGBoost), a powerful machine learning algorithm that combines the predictions of multiple weak models to create a strong predictive model with high accuracy and efficiency, in order to develop and validate a predictive model for in-hospital mortality in patients with isolated severe traumatic brain injury and to identify the most influential predictors. In total, 545,388 patients from the 2013-2021 American College of Surgeons Trauma Quality Improvement Program (TQIP) database were included in the current study, with 80% of the patients used for model training and 20% of the patients for the final model test. The primary outcome of the study was in-hospital mortality. Predictors were patients' demographics, admission status, as well as comorbidities, and clinical characteristics. Penalized Cox regression models were used to investigate the associations between the survival outcomes and the predictors and select the best predictors. An extreme gradient boosting (XGBoost)-powered Cox regression model was then used to predict the survival outcome. The performance of the models was evaluated using the Harrell's concordance index (C-index). The time-dependent area under the receiver operating characteristic curve (AUC) was used to evaluate the dynamic cumulative performance of the models. The importance of the predictors in the final prediction model was evaluated using the Shapley additive explanations (SHAP) value.

RESULTS

On average, the final XGBoost-powered Cox regression model performed at an acceptable level for patients with a length of stay up to 250 days (mean time-dependent AUC = 0.713) in the test dataset. However, for patients with a length of stay between 20 and 213 days, the performance of the model was relatively poor (time-dependent AUC < 0.7). When limited to patients with a length of stay ≤20 days, which accounts for 95.4% of all the patients, the model achieved an excellent performance (mean time-dependent AUC = 0.813). When further limited to patients with a length of stay ≤5 days, which accounts for two-thirds of all the patients, the model achieved an outstanding performance (mean time-dependent AUC = 0.917).

CONCLUSION

The XGBoost-powered Cox regression model can achieve an outstanding predictive ability for in-hospital mortality during the first 5 days, primarily based on the severity of the injury, the GCS on admission, and the patient's age. These variables continue to demonstrate an excellent predictive ability up to 20 days after admission, a period of care that accounts for over 95% of severe TBI patients. Past 20 days of care, other factors appear to be the primary drivers of in-hospital mortality, indicating a potential window of opportunity for improving outcomes.

Spatiotemporal profile of atrophy in the first year following moderate-severe traumatic brain injury

Traumatic brain injury (TBI) triggers progressive neurodegeneration resulting in brain atrophy that continues months-to-years following injury. However, a comprehensive characterization of the spatial and temporal evolution of TBI-related brain atrophy remains incomplete. Utilizing a sensitive and unbiased morphometry analysis pipeline optimized for detecting longitudinal changes, we analyzed a sample consisting of 37 individuals with moderate-severe TBI who had primarily high-velocity and high-impact injury mechanisms. They were scanned up to three times during the first year after injury (3 months, 6 months, and 12 months post-injury) and compared with 33 demographically matched controls who were scanned once. Individuals with TBI already showed cortical thinning in frontal and temporal regions and reduced volume in the bilateral thalami at 3 months post-injury. Longitudinally, only a subset of cortical regions in the parietal and occipital lobes showed continued atrophy from 3 to 12 months post-injury. Additionally, cortical white matter volume and nearly all deep gray matter structures exhibited progressive atrophy over this period. Finally, we found that disproportionate atrophy of cortex along sulci relative to gyri, an emerging morphometric marker of chronic TBI, was present as early as 3 month post-injury. In parallel, neurocognitive functioning largely recovered during this period despite this pervasive atrophy. Our findings demonstrate msTBI results in characteristic progressive neurodegeneration patterns that are divergent across regions and scale with the severity of injury. Future clinical research using atrophy during the first year of TBI as a biomarker of neurodegeneration should consider the spatiotemporal profile of atrophy described in this study.

Sex differences in college students' knowledge of concussion and concussion education sources

Aim

To understand sex differences and sources of concussion education for college students. The literature for college students primarily focuses on sports concussions and general knowledge. Understanding how non-students-athletes learn is critical to developing interventions to improve concussion knowledge.

Participants

A random sample of 208 students from four-year institutions.

Methods

A 22-question online survey explored postsecondary students' current knowledge and education regarding concussions.

Results

Findings indicated that sex differences emerged with concussion knowledge and sources of concussion knowledge (e.g., leaflets, pamphlets, parents, and television). The top choices for where they wanted to learn about concussions were health educators, health centers, and campus peer educators.

Conclusion

This study provides an initial evaluation and implications for future research on providing concussion education.

Effects of a Subanesthetic Ketamine Infusion on Inflammatory and Behavioral Outcomes after Closed Head Injury in Rats

Traumatic brain injury (TBI) affects millions of people annually, and most cases are classified as mild TBI (mTBI). Ketamine is a potent trauma analgesic and anesthetic with anti-inflammatory properties. However, ketamine's effects on post-mTBI outcomes are not well characterized. For the current study, we used the Closed-Head Impact Model of Engineered Rotational Acceleration (CHIMERA), which replicates the biomechanics of a closed-head impact with resulting free head movement. Adult male Sprague-Dawley rats sustained a single-session, repeated-impacts CHIMERA injury. An hour after the injury, rats received an intravenous ketamine infusion (0, 10, or 20 mg/kg, 2 h period), during which locomotor activity was monitored. Catheter blood samples were collected at 1, 3, 5, and 24 h after the CHIMERA injury for plasma cytokine assays. Behavioral assays were conducted on post-injury days (PID) 1 to 4 and included rotarod, locomotor activity, acoustic startle reflex (ASR), and pre-pulse inhibition (PPI). Brain tissue samples were collected at PID 4 and processed for GFAP (astrocytes), Iba-1 (microglia), and silver staining (axonal injury). Ketamine dose-dependently altered locomotor activity during the infusion and reduced KC/GRO, TNF-α, and IL-1β levels after the infusion. CHIMERA produced a delayed deficit in rotarod performance (PID 3) and significant axonal damage in the optic tract (PID 4), without significant changes in other behavioral or histological measures. Notably, subanesthetic doses of intravenous ketamine infusion after mTBI did not produce adverse effects on behavioral outcomes in PID 1-4 or neuroinflammation on PID 4. A further study is warranted to thoroughly investigate beneficial effects of IV ketamine on mTBI given multi-modal properties of ketamine in traumatic injury and stress.

Physical Health and Well-being: Updates and the Way Ahead

INTRODUCTION

The Women in Combat Summit 2021 "Forging the Future: How Women Enhance the Fighting Force" took place during February 9-11, 2021, via a virtual conference platform. The third and final day of the Summit regarded the physical health and well-being of military women and included the topics of urogenital health, nutrition and iron-deficiency anemia, unintended pregnancy and contraception, and traumatic brain injury.

MATERIALS AND METHODS

After presentations on the topics earlier, interested conference attendees were invited to participate in focus groups to discuss and review policy recommendations for physical health and well-being in military women. Discussions centered around the topics discussed during the presentations, and suggestions for future Women in Combat Summits were noted. Specifics of the methods of the Summit are presented elsewhere in this supplement.

RESULTS

We formulated research and policy recommendations for urogenital health, nutrition and iron-deficiency anemia, contraception and unintended pregnancy, and traumatic brain injury.

CONCLUSIONS

In order to continue to develop the future health of military women, health care providers, researchers, and policymakers should consider the recommendations made in this supplement as they continue to build on the state of the science and forge the future.

Integrated Care Pathways for Black Persons With Traumatic Brain Injury: A Critical Transdisciplinary Scoping Review of the Clinical Care Journey

Objectives: This novel critical transdisciplinary scoping review examined the literature on integrated care pathways that consider Black people living with traumatic brain injury (TBI). The objectives were to (a) summarize the extent, nature, and range of literature on care pathways that consider Black populations, (b) summarize how Blackness, race, and racism are conceptualized in the literature, (c) determine how Black people come to access care pathways, and (d) identify how care pathways in research consider the mechanism of injury and implications for human occupation. Methods: Six databases were searched systematically identifying 178 articles after removing duplicates. In total, 43 articles on integrated care within the context of Black persons with TBI were included. Narrative synthesis was conducted to analyze the data and was presented as descriptive statistics and as a narrative to tell a story. Findings: All studies were based in the United States where 81% reported racial and ethnic disparities across the care continuum primarily using race as a biological construct. Sex, gender, and race are used as demographic variables where statistical data were stratified in only 9% of studies. Black patients are primarily denied access to care, experience lower rates of protocol treatments, poor quality of care, and lack access to rehabilitation. Racial health disparities are disconnected from racism and are displayed as symptoms of a problem that remains unnamed. Conclusion: The findings illustrate how racism becomes institutionalized in research on TBI care pathways, demonstrating the need to incorporate the voices of Black people, transcend disciplinary boundaries, and adopt an anti-racist lens to research.

Prediction of In-Hospital Outcomes in Patients with Traumatic Brain Injury Using Computed Tomographic Scoring Systems: A Comparison Between Marshall, Rotterdam, and Neuroimaging Radiological Interpretation Systems

OBJECTIVE

This study aimed to compare the prognostic value of Marshall, Rotterdam, and Neuroimaging Radiological Interpretation Systems (NIRIS) in predicting the in-hospital outcomes of patients with traumatic brain injury.

METHODS

We identified 250 patients with traumatic brain injury in a retrospective single-center cohort from 2019 to 2020. Computed tomography (CT) scans were reviewed by two radiologists and scored according to three CT scoring systems. One-month outcomes were evaluated, including hospitalization, intensive care unit admission, neurosurgical procedure, and mortality. Logistic regression analysis was performed to identify scoring systems and outcome relationships. The best cutoff value was calculated using the receiver operating characteristic curve model.

RESULTS

Eighteen patients (7.2%) died in the 1-month follow-up. The mean age and Glasgow Coma Scale of survivors differed significantly from nonsurvivors. Subarachnoid hemorrhage and compressed/absent cisterns were dead patients' most frequent CT findings. All three scoring systems had good discrimination power in mortality prediction (area under the receiver operating characteristic curve of the Marshall, Rotterdam, and NIRIS was 0.78, 0.86, and 0.84, respectively). Regarding outcome, three systems directly correlated with unfavorable outcome prediction.

CONCLUSIONS

The Marshall, Rotterdam, and NIRIS are good predictive models for mortality and outcome prediction, with slight superiority of the Rotterdam in mortality prediction and the Marshall in intensive care unit admission and neurosurgical procedures.

Mild traumatic brain injury as a pathological process

Traumatic brain injury (TBI) is defined as dysfunction or other evidence of brain pathology caused by external physical force. More than 69 million new cases of TBI are registered worldwide each year, 80% of them - mild TBI. Based on the physical mechanism of induced trauma, we can separate its pathophysiology into primary and secondary injuries. Many literature sources have confirmed that mechanically induced brain injury initiates ionic, metabolic, inflammatory, and neurovascular changes in the CNS, which can lead to acute, subacute, and chronic neurological consequences. Despite the global nature of the disease, its high heterogeneity, lack of a unified classification system, rapid fluctuation of epidemiological trends, and variability of long-term consequences significantly complicate research and the development of new therapeutic strategies. In this review paper, we systematize current knowledge of biomechanical and molecular mechanisms of mild TBI and provide general information on the classification and epidemiology of this complex disorder.

A Swine Model of Changes in the Neuronal Electromagnetic Field After Traumatic Brain Injury: A Pilot Study

Background Traumatic brain injury (TBI) is a global cause of disability and mortality. Treatment depends on mitigation of secondary injury resulting in axonal injury, necrosis, brain dysfunction, and disruption of electrical and chemical signaling in neural circuits. To better understand TBI, translational models are required to study physiology, diagnostics, and treatments in homologous species, such as swine. Electromagnetic fields (EMFs) from altered neural circuits can be measured and historically have been reliant on expensive shielding and supercooling in magnetoencephalography. Using proprietary induction sensors, it has been found that a non-invasive, non-contact approach with an engineered Mu-metal and copper mesh-shielded helmet effectively measures EMFs. This has not yet been investigated in swine models. We wished to evaluate the efficacy of this technology to assess TBI-dependent EMF changes in swine to describe the efficacy of these sensors and this model using a gravity-dependent controlled cortical impact (CCI). Methods A Yucatan miniswine was evaluated using non-contact, non-invasive proprietary induction sensors with an engineered dual-layer Mu-metal and interlaced copper mesh helmet with sensors within EMF channels connected to a helmet. Swine EMF recordings were obtained prior to induced gravity-dependent CCI followed by post-TBI measurements. Behavioral changes and changes in EMF measurements were assessed. EMF measurements were evaluated with an artificial intelligence (AI) model. Results Differences between room "noise" EMF measurements and pre-TBI swine electromagnetic field measurements were identified. Morphological characteristics between pre-injury and post-injury measurements were noted. AI modeling differentiated pre-injury and post-injury patterns in the swine EMF. Frequently identified frequencies seen post-injury were peaks at 2.5 Hz and 6.5 Hz and a valley at 11 Hz. The AI model identified less changes in the slope and thus decreased variation of EMF measurements post-TBI between 4.5 Hz and 7 Hz. Conclusions For the first time, it was identified that cortical function in a swine can be appropriately measured using novel induction sensors and shielding isolated to a helmet and EMF channels. The swine model can be appropriately differentiated from the external noise signal with identifiably different pre-injury and post-injury EMFs. Patterns can be recognized within the post-injury EMF due to altered neural circuits that can be measured using these sensors continuously, non-invasively, and in real time.

Cranial Bone Changes Induced by Mild Traumatic Brain Injuries: A Neglected Player in Concussion Outcomes?

Mild traumatic brain injuries (TBIs), particularly when repetitive in nature, are increasingly recognized to have a range of significant negative implications for brain health. Much of the ongoing research in the field is focused on the neurological consequences of these injuries and the relationship between TBIs and long-term neurodegenerative conditions such as chronic traumatic encephalopathy and Alzheimer's disease. However, our understanding of the complex relationship between applied mechanical force at impact, brain pathophysiology, and neurological function remains incomplete. Past research has shown that mild TBIs, even below the threshold that results in cranial fracture, induce changes in cranial bone structure and morphology. These structural and physiological changes likely have implications for the transmission of mechanical force into the underlying brain parenchyma. Here, we review this evidence in the context of the current understanding of bone mechanosensitivity and the consequences of TBIs or concussions. We postulate that heterogeneity of the calvarium, including differing bone thickness attributable to past impacts, age, or individual variability, may be a modulator of outcomes after subsequent TBIs. We advocate for greater consideration of cranial responses to TBI in both experimental and computer modeling of impact biomechanics, and raise the hypothesis that calvarial bone thickness represents a novel biomarker of brain injury vulnerability post-TBI.

The Central Fluid Percussion Brain Injury in a Gyrencephalic Pig Brain: Scalable Diffuse Injury and Tissue Viability for Glial Cell Immunolabeling following Long-Term Refrigerated Storage

Traumatic brain injury (TBI) affects millions of people annually; however, our knowledge of the diffuse pathologies associated with TBI is limited. As diffuse pathologies, including axonal injury and neuroinflammatory changes, are difficult to visualize in the clinical population, animal models are used. In the current study, we used the central fluid percussion injury (CFPI) model in a micro pig to study the potential scalability of these diffuse pathologies in a gyrencephalic brain of a species with inflammatory systems very similar to humans. We found that both axonal injury and microglia activation within the thalamus and corpus callosum are positively correlated with the weight-normalized pressure pulse, while subtle changes in blood gas and mean arterial blood pressure are not. We also found that the majority of tissue generated up to 10 years previously is viable for immunofluorescent labeling after long-term refrigeration storage. This study indicates that a micro pig CFPI model could allow for specific investigations of various degrees of diffuse pathological burdens following TBI.

Physical activity and perceived barriers in individuals with moderate-to-severe traumatic brain injury

INTRODUCTION

Regular physical activity (PA), especially aerobic exercise, may benefit cognitive function in middle-aged and older adults, but promoting regular PA in individuals with traumatic brain injury (TBI) remains a challenge.

OBJECTIVE

To characterize PA and perceived barriers to PA in younger (<45 years) and middle age and older (≥45 years) individuals ≥1 year after moderate-to-severe TBI.

DESIGN

Multicenter survey study.

SETTING

Community.

PARTICIPANTS

Persons who met the following criteria were included in the study: (1) 18 years and older; (2) English speaking; (3) History of moderate-to-severe TBI; (4) Followed in a TBI Model Systems Center for at least 1 year; and (5) Able to complete the survey independently.

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURE(S)

PA level measured by Rapid Assessment of Physical Activity questionnaire (RAPA) and self-reported barriers to PA.

RESULTS

A total of 472 participants completed the survey (response rate of 21%). More individuals in the younger group (<45 years old) met Centers for Disease Control and Prevention (CDC) recommended aerobic PA guidelines compared to the middle-aged and older group (≥ 45 years old) (62% vs 36%, p < .001). Lack of motivation, lack of time, and fatigue were the most reported barriers. Perceived barriers to PA varied by age and PA level: the middle-aged and older individuals (≥ 45 years old) were more likely to report no barriers and inactive individuals (RAPA ≤5) more likely to report lack of motivation and money, pain, and lack of resources.

CONCLUSION

Participants ≥45 years of age were less likely to meet the CDC PA guidelines than younger individuals after moderate-to-severe TBI. Because perceived barriers to PA varied between age groups and PA levels, individualized approaches may be needed to promote PA in this population.

Colony-Stimulating Factor-1 Receptor Inhibition Transiently Attenuated the Peripheral Immune Response to Experimental Traumatic Brain Injury

To investigate microglial mechanisms in central and peripheral inflammation after experimental traumatic brain injury (TBI), we inhibited the colony-stimulating factor-1 receptor (CSF-1R) with PLX5622 (PLX). We hypothesized that microglia depletion would attenuate central inflammation acutely with no effect on peripheral inflammation. After randomization, male mice (n = 105) were fed PLX or control diets (21 days) and then received midline fluid percussion injury or sham injury. Brain and blood were collected at 1, 3, or 7 days post-injury (DPI). Immune cell populations were quantified in the brain and blood by flow cytometry. Cytokines (interleukin [IL]-6, IL-1β, tumor necrosis factor-α, interferon-γ, IL-17A, and IL-10) were quantified in the blood using a multi-plex enzyme-linked immunosorbent assay. Data were analyzed using Bayesian multi-variate, multi-level models. PLX depleted microglia at all time points and reduced neutrophils in the brain at 7 DPI. PLX also depleted CD115+ monocytes, reduced myeloid cells, neutrophils, and Ly6Clow monocytes in blood, and elevated IL-6. TBI induced a central and peripheral immune response. TBI elevated leukocytes, microglia, and macrophages in the brain and elevated peripheral myeloid cells, neutrophils, Ly6Cint monocytes, and IL-1β in the blood. TBI lowered peripheral CD115+ and Ly6Clow monocytes in the blood. TBI PLX mice had fewer leukocytes and microglia in the brain at 1 DPI, with elevated neutrophils at 7 DPI compared to TBI mice on a control diet. TBI PLX mice also had fewer peripheral myeloid cells, CD115+, and Ly6Clow monocytes in the blood at 3 DPI, but elevated Ly6Chigh, Ly6Cint, and CD115+ monocyte populations at 7 DPI, compared to TBI mice on a control diet. TBI PLX mice had elevated proinflammatory cytokines and lower anti-inflammatory cytokines in the blood at 7 DPI compared to TBI mice on a control diet. CSF-1R inhibition reduced the immune response to TBI at 1 and 3 DPI, but elevated peripheral inflammation at 7 DPI.

N-acetylcysteine treatment mitigates loss of cortical parvalbumin-positive interneuron and perineuronal net integrity resulting from persistent oxidative stress in a rat TBI model

Traumatic brain injury (TBI) increases cerebral reactive oxygen species production, which leads to continuing secondary neuronal injury after the initial insult. Cortical parvalbumin-positive interneurons (PVIs; neurons responsible for maintaining cortical inhibitory tone) are particularly vulnerable to oxidative stress and are thus disproportionately affected by TBI. Systemic N-acetylcysteine (NAC) treatment may restore cerebral glutathione equilibrium, thus preventing post-traumatic cortical PVI loss. We therefore tested whether weeks-long post-traumatic NAC treatment mitigates cortical oxidative stress, and whether such treatment preserves PVI counts and related markers of PVI integrity and prevents pathologic electroencephalographic (EEG) changes, 3 and 6 weeks after fluid percussion injury in rats. We find that moderate TBI results in persistent oxidative stress for at least 6 weeks after injury and leads to the loss of PVIs and the perineuronal net (PNN) that surrounds them as well as of per-cell parvalbumin expression. Prolonged post-TBI NAC treatment normalizes the cortical redox state, mitigates PVI and PNN loss, and - in surviving PVIs - increases per-cell parvalbumin expression. NAC treatment also preserves normal spectral EEG measures after TBI. We cautiously conclude that weeks-long NAC treatment after TBI may be a practical and well-tolerated treatment strategy to preserve cortical inhibitory tone post-TBI.

Determining the value of early measurement of interleukin-10 in predicting the absence of brain lesions in CT scans of patients with mild traumatic brain injury

Blood-based biomarkers were recently proposed as predictors of traumatic brain injury (TBI) outcomes. This would be a critical step forward since the majority of TBI events are mild and structural brain damage in this group may be missed by current brain imaging methods. We sought to determine the performance of early measurement of interleukin-10 (IL-10) to distinguish computed tomography (CT)-positive from negative patients with mild TBI. We designed a single-center prospective observational study, which enrolled consecutive patients classed with mild TBI according to Glasgow Coma Scale [GCS] scores and appearance of at least one clinical symptom. Serum IL-10 levels were measured <3 h post hospital admission. The performance of IL-10 levels in correctly classifying patients was evaluated. IL-10 levels were significantly higher in the group with positive CT scans (p < 0.001). With sensitivity set at 100%, the specificity of IL-10 was only 38.1%. However, the specificities of IL-10 for prediction of negative and positive cases increased to 59% and 49%, respectively, when both parameters were assessed within 90 min of admission. For mild TBI patients between 36 and 66 years, classification performance increased significantly at the 100% sensitivity level with a specificity of 93%. Our results suggest that IL-10 may be an easily accessible clinically useful diagnostic biomarker that can distinguish between mild TBI patients with and without structural brain damage with higher effectiveness when lower times of blood sampling are employed and patients are between 36 and 66 years of age.

Understanding microglial responses in large animal models of traumatic brain injury: an underutilized resource for preclinical and translational research

Traumatic brain injury (TBI) often results in prolonged or permanent brain dysfunction with over 2.8 million affected annually in the U.S., including over 56,000 deaths, with over 5 million total survivors exhibiting chronic deficits. Mild TBI (also known as concussion) accounts for over 75% of all TBIs every year. Mild TBI is a heterogeneous disorder, and long-term outcomes are dependent on the type and severity of the initial physical event and compounded by secondary pathophysiological consequences, such as reactive astrocytosis, edema, hypoxia, excitotoxicity, and neuroinflammation. Neuroinflammation has gained increasing attention for its role in secondary injury as inflammatory pathways can have both detrimental and beneficial roles. For example, microglia-resident immune cells of the central nervous system (CNS)-influence cell death pathways and may contribute to progressive neurodegeneration but also aid in debris clearance and neuroplasticity. In this review, we will discuss the acute and chronic role of microglia after mild TBI, including critical protective responses, deleterious effects, and how these processes vary over time. These descriptions are contextualized based on interspecies variation, sex differences, and prospects for therapy. We also highlight recent work from our lab that was the first to describe microglial responses out to chronic timepoints after diffuse mild TBI in a clinically relevant large animal model. The scaled head rotational acceleration of our large animal model, paired with the gyrencephalic architecture and appropriate white:gray matter ratio, allows us to produce pathology with the same anatomical patterns and distribution of human TBI, and serves as an exemplary model to examine complex neuroimmune response post-TBI. An improved understanding of microglial influences in TBI could aid in the development of targeted therapeutics to accentuate positive effects while attenuating detrimental post-injury responses over time.