A review of the pathology and treatment of TBI and PTSD

Single-Nucleus RNA Sequencing Reveals That Gabra6+ Neurons in Prefrontal Cortex Promote the Progression of PTSD After Shockwave-Induced TBI

Shockwave-induced traumatic brain injury (TBI) results in the onset of post-traumatic stress disorder (PTSD), triggered either by the TBI itself or other stressors. However, the interplay and underlying mechanisms of how these factors synergistically induce PTSD remain inadequately elucidated. Here, mice in the TBI (induced by biological shock tube blast injury) and PTSD (induced by single prolonged stress method) groups both displayed symptoms of PTSD behaviors, with the TBI+PTSD (composite model) group exhibiting more severe manifestations. The result of snRNA-seq demonstrated a noticeable increase in the population of Gabra6+ neurons in the prefrontal cortex region of mice in the TBI+PTSD group. Knocking down cortical Gabra6 mitigated PTSD-related behavioral outcomes. Mechanistically, the Smad3/4 complex activation led to the upregulation of Gabra6 expression in cortical neurons. Interaction of Gabra6 with Homer1 activated downstream cAMP signaling pathways. Homer1KO-Nestin mice show reduced susceptibility to PTSD. Subsequently, the efficacy of monoclonal antibody intervention at the 218 site of Gabra6 in ameliorating PTSD development is verified. This study suggests that TBI and stressors act as independent components in PTSD development, with Gabra6+ neurons pivotal in synergistically facilitating PTSD formation. Strategies geared toward minimizing exposure to singular or combined stressors may effectively diminish the risk of developing PTSD.

Prevalence of posttraumatic stress disorder after stroke: A systematic literature review

BACKGROUND

Posttraumatic stress disorder (PTSD) has shown to be related to worse functional outcome in individuals with stroke. This systematic literature review aimed to 1) provide a comprehensive overview of the evidence of prevalence of PTSD after stroke; 2) explore possible differences in prevalence between pathogenic origin of stroke and location of lesion; and 3) explore possible differences in prevalence between method of assessment of PTSD.

METHODS

A systematic literature search was performed on studies reporting on PTSD post-stroke. Risk of bias was assessed using an adapted version of the Joanna Briggs Institute's critical appraisal tool.

RESULTS

Thirty studies, reporting on 4320 individuals, were included. The weighted median PTSD prevalence overall was 17.5 % (2.9 %-71.4 %), in ischemic stroke 13.8 %, in transient ischemic attack 4.6 %, in intracerebral hemorrhage 6.5 %, and in subarachnoid hemorrhage 37.1 %. The weighted median prevalence based on self-report questionnaires was 17.8 % (3.7 %-71.4 %,) and based on PTSD interviews 4.0 % (2.9 %-32.8 %). At three and ≥ 12 months post-stroke the weighted median prevalence was respectively 24.7 % (0.0 %-37.1 %) and 17.8 % (6.5 %-71.4 %).

CONCLUSION

Results suggest that PTSD is common after stroke, and even more so after subarachnoid hemorrhage. This underlines the importance of awareness of and screening for PTSD post-stroke, even after the first year post-stroke.

The Successful Use of Bilateral 2-Level Ultrasound-Guided Stellate Ganglion Block to Improve Traumatic Brain Injury Symptoms: A Retrospective Analysis of 23 Patients

PURPOSE

The purpose of the study was to determine whether performing ultrasound-guided, bilateral stellate ganglion blocks (SGBs; performed on subsequent days) improved traumatic brain injury (TBI) symptoms.

METHODS

A retrospective chart review was conducted for the time period between August 2022 and February 2023 to identify patients who received bilateral, 2-level (C6 and C4) SGBs for PTSD symptoms but who also had a history of TBI. Neurobehavioral Symptoms Inventory (NSI) scores were collected at baseline, 1 week, and 1 month post-treatment in 14 males and 9 females.

RESULTS

Out of 23 patients, 22 showed improvement in their NSI scores. NSI baseline average score was 42.7; the average score at 1 week post-treatment was 18.8; 1 month post-treatment was 20.1. This represents a 53% improvement in the NSI score between baseline and 1 month.

CONCLUSION

The use of bilateral, 2-level SGBs may be indicated in treating patients with PTSD symptoms with concomitant diagnoses of mild-to-moderate TBI.

Association between the number of individuals injured in a traumatic event and posttraumatic stress disorder among hospitalized trauma patients

Posttraumatic stress disorder (PTSD) often occurs following mass casualty events, yet the connection between the number of individuals injured in an event and PTSD risk in smaller-scale events (i.e., involving one or several injured persons) remains unclear. We conducted a registries-based study cross-referencing three databases across the continuum of care for military trauma patients hospitalized for traumatic injuries. The study population was categorized into three groups based on the number of injured individuals involved (i.e., single injured person, two to four [2-4] injured people, and five or more [≥ 5] injured people), and PTSD prevalence was assessed using long-term disability claim diagnoses. Overall, 4,030 military personnel were included (age at injury: Mdn = 20 years), and 18.3% were subsequently diagnosed with PTSD, with the highest prevalence in events involving ≥ 5 injured individuals (35.8%). Regression analyses adjusted for potential confounders revealed that being injured in an event with 2-4 injured persons, OR = 1.68, 95% CI [1.31, 2.15], or ≥ 5 injured persons, OR = 2.36, 95% CI [1.79, 3.13], was associated with increased odds of developing PTSD compared to being the sole injured person. The findings suggest a direct association between the number of injured individuals in an event and PTSD prevalence among traumatic injury survivors. The results underscore the importance of early diagnosis and interventions to prevent PTSD in individuals injured in multicasualty and mass casualty events.

Low-frequency repetitive transcranial magnetic stimulation for the treatment of post-traumatic stress disorder and its comparison with high-frequency stimulation: a systematic review and meta-analysis

Background

Repetitive transcranial magnetic stimulation (rTMS) showed potentially beneficial effects for the treatment of post-traumatic stress disorder (PTSD). Low-frequency (LF) rTMS decreases neuronal excitability and may have better safety compared to high-frequency (HF) rTMS. However, there lacks meta-analysis specifically focusing on LF rTMS.

Objectives

To specifically explore the efficacy and safety of LF rTMS for treating PTSD.

Methods

Databases including PubMed, EMBASE, MEDLINE, and Web of Science were systematically searched from inception to October 17, 2023. Both randomized controlled trials (RCTs) and open trials of LF rTMS on PTSD were included, and we additionally included RCTs comparing HF rTMS and sham treatment on PTSD. First, we qualitatively summarized parameters of LF rTMS treatment; then, we extracted data from the LF rTMS treatment subgroups of these studies to examine its effect size and potential influencing factors; third, we compared the effect sizes among LF rTMS, HF rTMS and sham treatment through network meta-analysis of RCTs.

Results

In all, 15 studies with a sample size of 542 participants were included. The overall effect size for LF rTMS as a treatment for PTSD was found as Hedges' g = 1.02 (95% CI (0.56, 1.47)). Meta-regression analysis did not reveal any influencing factors. Network meta-analysis showed that compared to sham treatment, only HF rTMS on the right dorsolateral prefrontal cortex (DLPFC) demonstrated a significant advantage in ameliorating PTSD symptoms, while LF rTMS on the right DLPFC showed a trend toward advantage, but the difference was not significant.

Conclusion

The current literature shows LF rTMS has effect in treating PTSD caused by various traumatic events. However, present limited number of RCT studies only showed LF rTMS to have a trend of advantage compared to sham treatment in treating PTSD caused by external traumatic events. In the future, more RCTs are needed to be made to confirm the efficacy of LF rTMS. Additionally, studies are required to elucidate the underlying mechanism in order to further improve its efficacy in different traumatic populations.

PROSPERO registration number

CRD42023470169.

Dizziness Directly Influences Postconcussion Symptoms and Is Predictive of Poorer Mental Health in UK Military Personnel: A Retrospective Analysis

OBJECTIVE

To investigate the contribution of dizziness to postconcussion symptoms, depression, and anxiety symptoms.

SETTING

Mild traumatic brain injury (mTBI) service, Defence Medical Rehabilitation Centre, Stanford Hall.

PARTICIPANTS

Two hundred eighty-three UK military personnel from the Royal Navy, Royal Airforce, Royal Marines, and British Army.

DESIGN

A retrospective analysis of data from the Ministry of Defence medical records database.

MAIN MEASURES

Sixteen-item Rivermead Post Concussion Symptoms Questionnaire, Generalized Anxiety Disorder 7-item scale, Patient Health Questionnaire-9, The Dizziness Handicap Inventory.

RESULTS

Injuries from sports or falls were the most common mechanism of mTBI, accounting for 23%, respectively. Chi-square analysis indicated that individuals with dizziness and postconcussion symptoms (PCS) had greater severity of PCS, depression, and anxiety than those with PCS alone. Mediation analysis showed dizziness directly and independently influenced the severity of PCS, despite the indirect effects of mediating depression and anxiety symptoms.

CONCLUSION

Comorbid dizziness and PCS were predictive of poorer mental health compared with PCS alone. In addition, dizziness directly influenced the severity of PCS irrespective of the indirect effects of mental health symptoms. These observations suggest that treating dizziness with vestibular rehabilitation may improve PCS and mental health.

Non-stem cell-derived exosomes: a novel therapeutics for neurotrauma

Neurotrauma, encompassing traumatic brain injuries (TBI) and spinal cord injuries (SCI) impacts a significant portion of the global population. While spontaneous recovery post-TBI or SCI is possible, recent advancements in cell-based therapies aim to bolster these natural reparative mechanisms. Emerging research indicates that the beneficial outcomes of such therapies might be largely mediated by exosomes secreted from the administered cells. While stem cells have garnered much attention, exosomes derived from non-stem cells, including neurons, Schwann cells, microglia, and vascular endothelial cells, have shown notable therapeutic potential. These exosomes contribute to angiogenesis, neurogenesis, and axon remodeling, and display anti-inflammatory properties, marking them as promising agents for neurorestorative treatments. This review provides an in-depth exploration of the current methodologies, challenges, and future directions regarding the therapeutic role of non-stem cell-derived exosomes in neurotrauma.

Biomaterials in Traumatic Brain Injury: Perspectives and Challenges

Traumatic brain injury (TBI) is a leading cause of mortality and long-term impairment globally. TBI has a dynamic pathology, encompassing a variety of metabolic and molecular events that occur in two phases: primary and secondary. A forceful external blow to the brain initiates the primary phase, followed by a secondary phase that involves the release of calcium ions (Ca2+) and the initiation of a cascade of inflammatory processes, including mitochondrial dysfunction, a rise in oxidative stress, activation of glial cells, and damage to the blood-brain barrier (BBB), resulting in paracellular leakage. Currently, there are no FDA-approved drugs for TBI, but existing approaches rely on delivering micro- and macromolecular treatments, which are constrained by the BBB, poor retention, off-target toxicity, and the complex pathology of TBI. Therefore, there is a demand for innovative and alternative therapeutics with effective delivery tactics for the diagnosis and treatment of TBI. Tissue engineering, which includes the use of biomaterials, is one such alternative approach. Biomaterials, such as hydrogels, including self-assembling peptides and electrospun nanofibers, can be used alone or in combination with neuronal stem cells to induce neurite outgrowth, the differentiation of human neural stem cells, and nerve gap bridging in TBI. This review examines the inclusion of biomaterials as potential treatments for TBI, including their types, synthesis, and mechanisms of action. This review also discusses the challenges faced by the use of biomaterials in TBI, including the development of biodegradable, biocompatible, and mechanically flexible biomaterials and, if combined with stem cells, the survival rate of the transplanted stem cells. A better understanding of the mechanisms and drawbacks of these novel therapeutic approaches will help to guide the design of future TBI therapies.

Navigating the Complexities of Traumatic Encephalopathy Syndrome (TES): Current State and Future Challenges

Chronic traumatic encephalopathy (CTE) is a unique neurodegenerative disease that is associated with repetitive head impacts (RHI) in both civilian and military settings. In 2014, the research criteria for the clinical manifestation of CTE, traumatic encephalopathy syndrome (TES), were proposed to improve the clinical identification and understanding of the complex neuropathological phenomena underlying CTE. This review provides a comprehensive overview of the current understanding of the neuropathological and clinical features of CTE, proposed biomarkers of traumatic brain injury (TBI) in both research and clinical settings, and a range of treatments based on previous preclinical and clinical research studies. Due to the heterogeneity of TBI, there is no universally agreed-upon serum, CSF, or neuroimaging marker for its diagnosis. However, as our understanding of this complex disease continues to evolve, it is likely that there will be more robust, early diagnostic methods and effective clinical treatments. This is especially important given the increasing evidence of a correlation between TBI and neurodegenerative conditions, such as Alzheimer's disease and CTE. As public awareness of these conditions grows, it is imperative to prioritize both basic and clinical research, as well as the implementation of necessary safe and preventative measures.

Cerebral Aneurysm and Interleukin-6: a Key Player in Aneurysm Generation and Rupture or Just One of the Multiple Factors?

Intracranial aneurysm (IA) rupture is a common cause of subarachnoid hemorrhage (SAH) with high mortality and morbidity. Inflammatory interleukins (IL), such as IL-6, play an important role in the occurrence and rupture of IA causing SAH. With this review we aim to elucidate the specific role of IL-6 in aneurysm formation and rupture in preclinical and clinical studies. IL-6 is a novel cytokine in that it has pro-inflammatory and anti-inflammatory signaling pathways. In preclinical and clinical studies of IA formation, elevated and reduced levels of IL-6 are reported. Poor post-rupture prognosis and increased rupture risk, however, are associated with higher levels of IL-6. By better understanding the relationships between IL-6 and IA formation and rupture, IL-6 may serve as a biomarker in high-risk populations. Furthermore, by better understanding the IL-6 signaling mechanisms in IA formation and rupture, IL-6 may optimize surveillance and treatment strategies. This review examines the association between IL-6 and IA, while also suggesting future research directions.

An Understated Comorbidity: The Impact of Homelessness on Traumatic Brain Injury

Traumatic brain injury (TBI), a neurovascular injury caused by external force, is a common diagnosis among veterans and those experiencing homelessness (HL). There is a significant overlap in the veteran and homeless population, possibly accounting for the two to seven times greater incidence of TBI among those experiencing HL than the general population. Despite these statistics, individuals experiencing HL are often underdiagnosed and ineffectively treated for TBI. We introduced a novel model of HL. Over 5 weeks, adult Sprague-Dawley rats were randomly assigned to one of the following conditions: TBI only, HL only, TBI + HL, or control (n = 9 per group). To emulate HL, animals (2 animals per cage) were exposed to soiled beddings for 5 weeks. Subsequently, animals were introduced to TBI by using the moderate controlled cortical impact model, then underwent 4 consecutive days of behavioral testing (beam walk (BW), elevated body swing test (EBST), forelimb akinesia (FA), paw grasp (PG), Rotorod, and elevated T-maze). Nissl staining was performed to determine the peri-impact cell survival and the integrity of corpus callosum area. Motor function was significantly impaired by TBI, regardless of housing (beam walk or BW 85.0%, forelimb akinesia or FA 104.7%, and paw grasp or PG 100% greater deficit compared to control). Deficits were worsened by HL in TBI rats (BW 93.3%, FA 40.5%, and PG 50% greater deficit). Two-way ANOVA revealed BW (F(4, 160) = 31.69, p < 0.0001), FA (F(4, 160) = 13.71, p < 0.0001), PG (F(4, 160) = 3.873, p = 0.005), Rotorod (F(4, 160), p = 1.116), and EBST (F(4, 160) = 6.929, p < 0.0001) showed significant differences between groups. The Rotorod and EBST tests showed TBI-induced functional deficits when analyzed by day, but these deficits were not exacerbated by HL. TBI only and TBI + HL rats exhibited typical cortical impact damage (F(3,95) = 51.75, p < 0.0001) and peri-impact cell loss compared to control group (F(3,238) = 47.34, p < 0.0001). Most notably, TBI + HL rats showed significant alterations in WM area measured via the corpus callosum (F(3, 95) = 3.764, p = 0.0133). Worsened behavioral outcomes displayed by TBI + HL rats compared to TBI alone suggest HL contributes to TBI functional deficits. While an intact white matter, such as the corpus callosum, may lessen the consequent functional deficits associated with TBI by enhancing hemispheric communications, there are likely alternative cellular and molecular pathways mitigating TBI-associated inflammatory or oxidative stress responses. Here, we showed that the environmental condition of the patient, i.e., HL, participates in white matter integrity and behavioral outcomes, suggesting its key role in the disease diagnosis to aptly treat TBI patients.

Identifying the Target Traumatic Brain Injury Population for Hyperbaric Oxygen Therapy

Traumatic brain injury (TBI) results from direct penetrating and indirect non-penetrating forces that alters brain functions, affecting millions of individuals annually. Primary injury following TBI is exacerbated by secondary brain injury; foremost is the deleterious inflammatory response. One therapeutic intervention being increasingly explored for TBI is hyperbaric oxygen therapy (HBOT), which is already approved clinically for treating open wounds. HBOT consists of 100% oxygen administration, usually between 1.5 and 3 atm and has been found to increase brain oxygenation levels after hypoxia in addition to decreasing levels of inflammation, apoptosis, intracranial pressure, and edema, reducing subsequent secondary injury. The following review examines recent preclinical and clinical studies on HBOT in the context of TBI with a focus on contributing mechanisms and clinical potential. Several preclinical studies have identified pathways, such as TLR4/NF-kB, that are affected by HBOT and contribute to its therapeutic effect. Thus far, the mechanisms mediating HBOT treatment have yet to be fully elucidated and are of interest to researchers. Nonetheless, multiple clinical studies presented in this review have examined the safety of HBOT and demonstrated the improved neurological function of TBI patients after HBOT, deeming it a promising avenue for treatment.

Levels of Arachidonic Acid-Derived Oxylipins and Anandamide Are Elevated Among Military APOE ɛ4 Carriers With a History of Mild Traumatic Brain Injury and Post-Traumatic Stress Disorder Symptoms

Currently approved blood biomarkers detect intracranial lesions in adult patients with mild to moderate traumatic brain injury (TBI) acutely post-injury. However, blood biomarkers are still needed to help with a differential diagnosis of mild TBI (mTBI) and post-traumatic stress disorder (PTSD) at chronic post-injury time points. Owing to the association between phospholipid (PL) dysfunction and chronic consequences of TBI, we hypothesized that examining bioactive PL metabolites (oxylipins and ethanolamides) would help identify long-term lipid changes associated with mTBI and PTSD. Lipid extracts of plasma from active-duty soldiers deployed to the Iraq/Afghanistan wars (control = 52, mTBI = 21, PTSD = 34, and TBI + PTSD = 13) were subjected to liquid chromatography/mass spectrometry analysis to examine oxylipins and ethanolamides. Linear regression analyses followed by post hoc comparisons were performed to assess the association of these lipids with diagnostic classifications. Significant differences were found in oxylipins derived from arachidonic acid (AA) between controls and mTBI, PTSD, and mTBI + PTSD groups. Levels of AA-derived oxylipins through the cytochrome P450 pathways and anandamide were significantly elevated among mTBI + PTSD patients who were carriers of the apolipoprotein E E4 allele. These studies demonstrate that AA-derived oxylipins and anandamide may be unique blood biomarkers of PTSD and mTBI + PTSD. Further, these AA metabolites may be indicative of an underlying inflammatory process that warrants further investigation. Future validation studies in larger cohorts are required to determine a potential application of this approach in providing a differential diagnosis of mTBI and PTSD in a clinical setting.

Recent advances in the role of miRNAs in post-traumatic stress disorder and traumatic brain injury

Post-traumatic stress disorder (PTSD) is usually considered a psychiatric disorder upon emotional trauma. However, with the rising number of conflicts and traffic accidents around the world, the incidence of PTSD has skyrocketed along with traumatic brain injury (TBI), a complex neuropathological disease due to external physical force and is also the most common concurrent disease of PTSD. Recently, the overlap between PTSD and TBI is increasingly attracting attention, as it has the potential to stimulate the emergence of novel treatments for both conditions. Of note, treatments exploiting the microRNAs (miRNAs), a well-known class of small non-coding RNAs (ncRNAs), have rapidly gained momentum in many nervous system disorders, given the miRNAs' multitudinous and key regulatory role in various biological processes, including neural development and normal functioning of the nervous system. Currently, a wealth of studies has elucidated the similarities of PTSD and TBI in pathophysiology and symptoms; however, there is a dearth of discussion with respect to miRNAs in both PTSD and TBI. In this review, we summarize the recent available studies of miRNAs in PTSD and TBI and discuss and highlight promising miRNAs therapeutics for both conditions in the future.

Stress and traumatic brain injury: An inherent bi-directional relationship with temporal and synergistic complexities

Traumatic brain injury (TBI) and stress are prevalent worldwide and can both result in life-altering health problems. While stress often occurs in the absence of TBI, TBI inherently involves some element of stress. Furthermore, because there is pathophysiological overlap between stress and TBI, it is likely that stress influences TBI outcomes. However, there are temporal complexities in this relationship (e.g., when the stress occurs) that have been understudied despite their potential importance. This paper begins by introducing TBI and stress and highlighting some of their possible synergistic mechanisms including inflammation, excitotoxicity, oxidative stress, hypothalamic-pituitary-adrenal axis dysregulation, and autonomic nervous system dysfunction. We next describe different temporal scenarios involving TBI and stress and review the available literature on this topic. In doing so we find initial evidence that in some contexts stress is a highly influential factor in TBI pathophysiology and recovery, and vice versa. We also identify important knowledge gaps and suggest future research avenues that will increase our understanding of this inherent bidirectional relationship and could one day result in improved patient care.

Novel, thalidomide-like, non-cereblon binding drug tetrafluorobornylphthalimide mitigates inflammation and brain injury

BACKGROUND

Quelling microglial-induced excessive neuroinflammation is a potential treatment strategy across neurological disorders, including traumatic brain injury (TBI), and can be achieved by thalidomide-like drugs albeit this approved drug class is compromised by potential teratogenicity. Tetrafluorobornylphthalimide (TFBP) and tetrafluoronorbornylphthalimide (TFNBP) were generated to retain the core phthalimide structure of thalidomide immunomodulatory imide drug (IMiD) class. However, the classical glutarimide ring was replaced by a bridged ring structure. TFBP/TFNBP were hence designed to retain beneficial anti-inflammatory properties of IMiDs but, importantly, hinder cereblon binding that underlies the adverse action of thalidomide-like drugs.

METHODS

TFBP/TFNBP were synthesized and evaluated for cereblon binding and anti-inflammatory actions in human and rodent cell cultures. Teratogenic potential was assessed in chicken embryos, and in vivo anti-inflammatory actions in rodents challenged with either lipopolysaccharide (LPS) or controlled cortical impact (CCI) moderate traumatic brain injury (TBI). Molecular modeling was performed to provide insight into drug/cereblon binding interactions.

RESULTS

TFBP/TFNBP reduced markers of inflammation in mouse macrophage-like RAW264.7 cell cultures and in rodents challenged with LPS, lowering proinflammatory cytokines. Binding studies demonstrated minimal interaction with cereblon, with no resulting degradation of teratogenicity-associated transcription factor SALL4 or of teratogenicity in chicken embryo assays. To evaluate the biological relevance of its anti-inflammatory actions, two doses of TFBP were administered to mice at 1 and 24 h post-injury following CCI TBI. Compared to vehicle treatment, TFBP reduced TBI lesion size together with TBI-induction of an activated microglial phenotype, as evaluated by immunohistochemistry 2-weeks post-injury. Behavioral evaluations at 1- and 2-weeks post-injury demonstrated TFBP provided more rapid recovery of TBI-induced motor coordination and balance impairments, versus vehicle treated mice.

CONCLUSION

TFBP and TFNBP represent a new class of thalidomide-like IMiDs that lower proinflammatory cytokine generation but lack binding to cereblon, the main teratogenicity-associated mechanism. This aspect makes TFBP and TFNBP potentially safer than classic IMiDs for clinical use. TFBP provides a strategy to mitigate excessive neuroinflammation associated with moderate severity TBI to, thereby, improve behavioral outcome measures and warrants further investigation in neurological disorders involving a neuroinflammatory component.

Aberrant cortical spine dynamics after concussive injury are reversed by integrated stress response inhibition

Traumatic brain injury (TBI) is a leading cause of long-term neurological disability in the world and the strongest environmental risk factor for the development of dementia. Even mild TBI (resulting from concussive injuries) is associated with a greater than twofold increase in the risk of dementia onset. Little is known about the cellular mechanisms responsible for the progression of long-lasting cognitive deficits. The integrated stress response (ISR), a phylogenetically conserved pathway involved in the cellular response to stress, is activated after TBI, and inhibition of the ISR-even weeks after injury-can reverse behavioral and cognitive deficits. However, the cellular mechanisms by which ISR inhibition restores cognition are unknown. Here, we used longitudinal two-photon imaging in vivo after concussive injury in mice to study dendritic spine dynamics in the parietal cortex, a brain region involved in working memory. Concussive injury profoundly altered spine dynamics measured up to a month after injury. Strikingly, brief pharmacological treatment with the drug-like small-molecule ISR inhibitor ISRIB entirely reversed structural changes measured in the parietal cortex and the associated working memory deficits. Thus, both neural and cognitive consequences of concussive injury are mediated in part by activation of the ISR and can be corrected by its inhibition. These findings suggest that targeting ISR activation could serve as a promising approach to the clinical treatment of chronic cognitive deficits after TBI.

Changes and Influencing Factors of Stress Disorder in Patients with Mild Traumatic Brain Injury Stress Disorder

Traumatic brain injury (TBI) is a brain injury caused by motor vehicle accidents, falls from heights, sports, and combat. Posttraumatic stress disorder (PTSD) is a complex mental disorder caused by physical and psychological trauma, which manifests itself with symptoms such as anxiety, depression, and cognitive dysfunction. How its symptoms arise and what factors influence it are not fully understood nor can it be predicted. In order to better understand the changes after stress disorder in TBI patients and the influencing factors of PTSD, this paper analyzed the changes and influencing factors of stress disorder in patients with mild traumatic brain injury stress disorder. In this paper, the Wechsler Memory Scale and functional magnetic resonance imaging were first used to study the memory impairment and functional changes of corresponding brain regions in patients with TBI stress disorder, and then, the Pittsburgh Sleep Quality Index Scale and the pain Visual Analogue Scale were used to study the influencing factors of PTSD. The results of the study showed that PTSD patients reduced and enhanced regional brain functional activity and impaired memory function in the resting state. Male gender, age under 45 years, no hemiplegia, and good sleep quality were protective factors for PTSD in TBI patients. The need for drug-assisted sleep, severe headache, and moderate headache was the risk factor for PTSD in TBI patients.

Microglia-specific deletion of histone deacetylase 3 promotes inflammation resolution, white matter integrity, and functional recovery in a mouse model of traumatic brain injury

BACKGROUND

Histone deacetylases (HDACs) are believed to exacerbate traumatic brain injury (TBI) based on studies using pan-HDAC inhibitors. However, the HDAC isoform responsible for the detrimental effects and the cell types involved remain unknown, which may hinder the development of specific targeting strategies that boost therapeutic efficacy while minimizing side effects. Microglia are important mediators of post-TBI neuroinflammation and critically impact TBI outcome. HDAC3 was reported to be essential to the inflammatory program of in vitro cultured macrophages, but its role in microglia and in the post-TBI brain has not been investigated in vivo.

METHODS

We generated HDAC3LoxP mice and crossed them with CX3CR1CreER mice, enabling in vivo conditional deletion of HDAC3. Microglia-specific HDAC3 knockout (HDAC3 miKO) was induced in CX3CR1CreER:HDAC3LoxP mice with 5 days of tamoxifen treatment followed by a 30-day development interval. The effects of HDAC3 miKO on microglial phenotype and neuroinflammation were examined 3-5 days after TBI induced by controlled cortical impact. Neurological deficits and the integrity of white matter were assessed for 6 weeks after TBI by neurobehavioral tests, immunohistochemistry, electron microscopy, and electrophysiology.

RESULTS

HDAC3 miKO mice harbored specific deletion of HDAC3 in microglia but not in peripheral monocytes. HDAC3 miKO reduced the number of microglia by 26%, but did not alter the inflammation level in the homeostatic brain. After TBI, proinflammatory microglial responses and brain inflammation were markedly alleviated by HDAC3 miKO, whereas the infiltration of blood immune cells was unchanged, suggesting a primary effect of HDAC3 miKO on modulating microglial phenotype. Importantly, HDAC3 miKO was sufficient to facilitate functional recovery for 6 weeks after TBI. TBI-induced injury to axons and myelin was ameliorated, and signal conduction by white matter fiber tracts was significantly enhanced in HDAC3 miKO mice.

CONCLUSION

Using a novel microglia-specific conditional knockout mouse model, we delineated for the first time the role of microglial HDAC3 after TBI in vivo. HDAC3 miKO not only reduced proinflammatory microglial responses, but also elicited long-lasting improvement of white matter integrity and functional recovery after TBI. Microglial HDAC3 is therefore a promising therapeutic target to improve long-term outcomes after TBI.

The role of IL-6 in TBI and PTSD, a potential therapeutic target?

This literature review focuses on the role of IL-6 in TBI or PTSD-induced neuroinflammation. While TBI and PTSD are widely prevalent, these diagnoses are particularly common amongst veterans. Given the role of IL-6 in neuroprotection acutely, compared to detrimental chronically, targeting this cytokine at specific time points may be beneficial in modulating neuroinflammation. Current treatments for TBI or PTSD are variably affective. By reviewing the role of IL-6 in these two diagnoses, future studies can focus on therapeutics to treat neuroinflammation and ultimately reduce the devastating impacts of neuroinflammation on cognition in PTSD and TBI.

Leveraging Continuous Vital Sign Measurements for Real-Time Assessment of Autonomic Nervous System Dysfunction After Brain Injury: A Narrative Review of Current and Future Applications

Subtle and profound changes in autonomic nervous system (ANS) function affecting sympathetic and parasympathetic homeostasis occur as a result of critical illness. Changes in ANS function are particularly salient in neurocritical illness, when direct structural and functional perturbations to autonomic network pathways occur and may herald impending clinical deterioration or intervenable evolving mechanisms of secondary injury. Sympathetic and parasympathetic balance can be measured quantitatively at the bedside using multiple methods, most readily by extracting data from electrocardiographic or photoplethysmography waveforms. Work from our group and others has demonstrated that data-analytic techniques can identify quantitative physiologic changes that precede clinical detection of meaningful events, and therefore may provide an important window for time-sensitive therapies. Here, we review data-analytic approaches to measuring ANS dysfunction from routine bedside physiologic data streams and integrating this data into multimodal machine learning-based model development to better understand phenotypical expression of pathophysiologic mechanisms and perhaps even serve as early detection signals. Attention will be given to examples from our work in acute traumatic brain injury on detection and monitoring of paroxysmal sympathetic hyperactivity and prediction of neurologic deterioration, and in large hemispheric infarction on prediction of malignant cerebral edema. We also discuss future clinical applications and data-analytic challenges and future directions.