Traumatic brain injuries

Fluid Biomarkers for Chronic Traumatic Encephalopathy

Chronic traumatic encephalopathy (CTE) is a neuropathological condition that has been described in individuals who have been exposed to repetitive head impacts, including concussions and subconcussive trauma. Currently, there is no fluid or imaging biomarker for diagnosing CTE during life. Based on retrospective clinical data, symptoms of CTE include changes in behavior, cognition, and mood, and may develop after a latency phase following the injuries. However, these symptoms are often nonspecific, making differential diagnosis based solely on clinical symptoms unreliable. Thus, objective biomarkers for CTE pathophysiology would be helpful in understanding the course of the disease as well as in the development of preventive and therapeutic measures. Herein, we review the literature regarding fluid biomarkers for repetitive concussive and subconcussive head trauma, postconcussive syndrome, as well as potential candidate biomarkers for CTE. We also discuss technical challenges with regard to the current fluid biomarkers and potential pathways to advance the most promising biomarker candidates into clinical routine.

Loss of diffuse noxious inhibitory control after traumatic brain injury in rats: A chronic issue

Chronic pain is one of the most challenging and debilitating symptoms to manage after traumatic brain injury (TBI), yet the underlying mechanisms remain elusive. The disruption of normal endogenous pain control mechanisms has been linked to several forms of chronic pain and may play a role in pain after TBI. We hypothesized therefore that dysfunctional descending noradrenergic and serotonergic pain control circuits may contribute to the loss of diffuse noxious inhibitory control (DNIC), a critical endogenous pain control mechanism, weeks to months after TBI. For these studies, the rat lateral fluid percussion model of mild TBI was used along with a DNIC paradigm involving a capsaicin-conditioning stimulus. We observed sustained failure of the DNIC response up to 180-days post injury. We confirmed, that descending α₂ adrenoceptor-mediated noradrenergic signaling was critical for endogenous pain inhibition in uninjured rats. However, augmenting descending noradrenergic signaling using reboxetine, a selective noradrenaline reuptake inhibitor, failed to restore DNIC after TBI. Furthermore, blocking serotonin-mediated descending signaling using selective spinal serotonergic fiber depletion with 5, 7-dihydroxytryptamine was also unsuccessful at restoring endogenous pain modulation after TBI. Unexpectedly, increasing descending serotonergic signaling using the selective serotonin reuptake inhibitor escitalopram and the serotonin-norepinephrine reuptake inhibitor duloxetine restored the DNIC response in TBI rats at both 49- and 180- days post injury. Consistent with these observations, spinal serotonergic fiber depletion with 5, 7-dihydroxytryptamine eliminated the effects of escitalopram. Intact α₂ adrenoceptor signaling, however, was not required for the serotonin-mediated restoration of DNIC after TBI. These results suggest that TBI causes maladaptation of descending nociceptive signaling mechanisms and changes in the function of both adrenergic and serotonergic circuits. Such changes could predispose those with TBI to chronic pain.

VEGFR2 signaling drives meningeal vascular regeneration upon head injury

Upon severe head injury (HI), blood vessels of the meninges and brain parenchyma are inevitably damaged. While limited vascular regeneration of the injured brain has been studied extensively, our understanding of meningeal vascular regeneration following head injury is quite limited. Here, we identify key pathways governing meningeal vascular regeneration following HI. Rapid and complete vascular regeneration in the meninges is predominantly driven by VEGFR2 signaling. Substantial increase of VEGFR2 is observed in both human patients and mouse models of HI, and endothelial cell-specific deletion of Vegfr2 in the latter inhibits meningeal vascular regeneration. We further identify the facilitating, stabilizing and arresting roles of Tie2, PDGFRβ and Dll4 signaling, respectively, in meningeal vascular regeneration. Prolonged inhibition of this angiogenic process following HI compromises immunological and stromal integrity of the injured meninges. These findings establish a molecular framework for meningeal vascular regeneration after HI, and may guide development of wound healing therapeutics.

Severe head injury results in critical damage of blood vessels of the meninges and brain parenchyma. Here, the authors describe key pathways governing meningeal vascular regeneration following head injury, characterizing the differential roles of VEGFR2, Tie2, Dll4 and PDGFRβ signaling.

The effectiveness of early prophylactic hypothermia in adult patients with traumatic brain injury: A systematic review and meta-analysis

OBJECTIVES

Previously published systematic reviews have explored the effects of therapeutic hypothermia on adult patients with traumatic brain injury (TBI). However, none explored the effect of early prophylactic hypothermia (within 6 h from injury to hypothermia induction). Animal studies indicated that early prophylactic hypothermia may reduce secondary injury and improve neurological outcomes. This systematic review aimed to investigate the effects of early prophylactic hypothermia on adult TBI regarding mortality, favourable outcomes, and complications.

DATA SOURCE

We searched electronic databases including Cochrane CENTRAL, PubMed, MEDLINE, CINAHL, EMBASE, Web of Science, OpenGrey, and ClinicalTrials.gov from inception to June 12, 2019. Manual search was conducted for additional information.

REVIEW METHODS

Only randomised controlled trials were included. The Cochrane Collaboration Risk of Bias Tool was used to assess the quality of included studies. We extracted general demographic characteristics, the initiation timing, methods of cooling, duration, target temperature, rewarming rate, mortality, neurological outcomes, and complications.

RESULTS

Six studies with a total of 1207 participants were included. Meta-analyses showed no significant difference in mortality and favourable outcomes (risk ratio = 1.11, 95% confidence interval = 0.90-1.37, P = 0.32; risk ratio = 1.03, 95% confidence interval = 0.91-1.16, P = 0.65, respectively). Similar results were found regarding different durations of hypothermia and different rewarming rates. Various complications were reported in the included studies. No statistical difference was found in three studies, while complications were reported to be significantly higher in the hypothermia group in the other three studies.

CONCLUSIONS

This review does not support the use of early prophylactic hypothermia (within 6 h after injury) as a neurological protection strategy in adult patients with TBI, irrespective of the short term or long term. No significant benefits were found regarding hypothermia with different rewarming rates. Owing to the limited number of studies, more randomised controlled trials with higher quality are required to establish true effects of early hypothermia in adult TBI.

Dynamic neural and glial responses of a head-specific model for traumatic brain injury in Drosophila

Traumatic brain injury (TBI) is the strongest environmental risk factor for the accelerated development of neurodegenerative diseases. There are currently no therapeutics to address this due to lack of insight into mechanisms of injury progression, which are challenging to study in mammalian models. Here, we have developed and extensively characterized a head-specific approach to TBI in Drosophila, a powerful genetic system that shares many conserved genes and pathways with humans. The Drosophila TBI (dTBI) device inflicts mild, moderate, or severe brain trauma by precise compression of the head using a piezoelectric actuator. Head-injured animals display features characteristic of mammalian TBI, including severity-dependent ataxia, life span reduction, and brain degeneration. Severe dTBI is associated with cognitive decline and transient glial dysfunction, and stimulates antioxidant, proteasome, and chaperone activity. Moreover, genetic or environmental augmentation of the stress response protects from severe dTBI-induced brain degeneration and life span deficits. Together, these findings present a tunable, head-specific approach for TBI in Drosophila that recapitulates mammalian injury phenotypes and underscores the ability of the stress response to mitigate TBI-induced brain degeneration.

Extracellular Vesicle Proteins and MicroRNAs as Biomarkers for Traumatic Brain Injury

Traumatic brain injury (TBI) is a heterogeneous condition, associated with diverse etiologies, clinical presentations and degrees of severity, and may result in chronic neurobehavioral sequelae. The field of TBI biomarkers is rapidly evolving to address the many facets of TBI pathology and improve its clinical management. Recent years have witnessed a marked increase in the number of publications and interest in the role of extracellular vesicles (EVs), which include exosomes, cell signaling, immune responses, and as biomarkers in a number of pathologies. Exosomes have a well-defined lipid bilayer with surface markers that reflect the cell of origin and an aqueous core that contains a variety of biological material including proteins (e.g., cytokines and growth factors) and nucleic acids (e.g., microRNAs). The presence of proteins associated with neurodegenerative changes such as amyloid-β, α-synuclein and phosphorylated tau in exosomes suggests a role in the initiation and propagation of neurological diseases. However, mechanisms of cell communication involving exosomes in the brain and their role in TBI pathology are poorly understood. Exosomes are promising TBI biomarkers as they can cross the blood-brain barrier and can be isolated from peripheral fluids, including serum, saliva, sweat, and urine. Exosomal content is protected from enzymatic degradation by exosome membranes and reflects the internal environment of their cell of origin, offering insights into tissue-specific pathological processes. Challenges in the clinical use of exosomal cargo as biomarkers include difficulty in isolating pure exosomes, variable yields of the isolation processes, quantification of vesicles, and lack of specificity of exosomal markers. Moreover, there is no consensus regarding nomenclature and characteristics of EV subtypes. In this review, we discuss current technical limitations and challenges of using exosomes and other EVs as blood-based biomarkers, highlighting their potential as diagnostic and prognostic tools in TBI.

Ferroptosis in Acute Central Nervous System Injuries: The Future Direction?

Acute central nervous system (CNS) injuries, such as stroke, traumatic brain injury (TBI), and spinal cord injury (SCI) present a grave health care challenge worldwide due to high morbidity and mortality, as well as limited clinical therapeutic strategies. Established literature has shown that oxidative stress (OS), inflammation, excitotoxicity, and apoptosis play important roles in the pathophysiological processes of acute CNS injuries. Recently, there have been many studies on the topic of ferroptosis, a form of regulated cell death characterized by the accumulation of iron-dependent lipid peroxidation. Some studies have revealed an emerging connection between acute CNS injuries and ferroptosis. Ferroptosis, induced by the abnormal metabolism of lipids, glutathione (GSH), and iron, can accelerate acute CNS injuries. However, pharmaceutical agents, such as iron chelators, ferrostatin-1 (Fer-1), and liproxstatin-1 (Lip-1), can inhibit ferroptosis and may have neuroprotective effects after acute CNS injuries. However, the specific mechanisms underlying this connection has not yet been clearly elucidated. In this paper, we discuss the general mechanisms of ferroptosis and its role in stroke, TBI, and SCI. We also summarize ferroptosis-related drugs and highlight the potential therapeutic strategies in treating various acute CNS injuries. Additionally, this paper suggests a testable hypothesis that ferroptosis may be a novel direction for further research of acute CNS injuries by providing corresponding evidence.

Reduced Reelin Expression in the Hippocampus after Traumatic Brain Injury

Traumatic brain injury (TBI) is a relatively common occurrence following accidents or violence, and often results in long-term cognitive or motor disability. Despite the high health cost associated with this type of injury, presently there are no effective treatments for many neurological symptoms resulting from TBI. This is due in part to our limited understanding of the mechanisms underlying brain dysfunction after injury. In this study, we used the mouse controlled cortical impact (CCI) model to investigate the effects of TBI, and focused on Reelin, an extracellular protein that critically regulates brain development and modulates synaptic activity in the adult brain. We found that Reelin expression decreases in forebrain regions after TBI, and that the number of Reelin-expressing cells decrease specifically in the hippocampus, an area of the brain that plays an important role in learning and memory. We also conducted in vitro experiments using mouse neuronal cultures and discovered that Reelin protects hippocampal neuronal cells from glutamate-induced neurotoxicity, a well-known secondary effect of TBI. Together our findings suggest that the loss of Reelin expression may contribute to neuronal death in the hippocampus after TBI, and raise the possibility that increasing Reelin levels or signaling activity may promote functional recovery.

Late contributions of repetitive head impacts and TBI to depression symptoms and cognition

OBJECTIVE

To test the hypothesis that repetitive head impacts (RHIs), like those from contact sport play and traumatic brain injury (TBI) have long-term neuropsychiatric and cognitive consequences, we compared middle-age and older adult participants who reported a history of RHI and/or TBI with those without this history on measures of depression and cognition.

METHODS

This cross-sectional study included 13,323 individuals (mean age, 61.95; 72.5% female) from the Brain Health Registry who completed online assessments, including the Ohio State University TBI Identification Method, the Geriatric Depression Scale (GDS-15), and the CogState Brief Battery and Lumos Labs NeuroCognitive Performance Tests. Inverse propensity-weighted linear regressions accounting for age, sex, race/ethnicity, and education tested the effects of RHI and TBI compared to a non-RHI/TBI group.

RESULTS

A total of 725 participants reported RHI exposure (mostly contact sport play and abuse) and 7,277 reported TBI (n = 2,604 with loss of consciousness [LOC]). RHI (β, 1.24; 95% CI, 0.36-2.12), TBI without LOC (β, 0.43; 95% CI, 0.31-0.54), and TBI with LOC (β, 0.75; 95% CI, 0.59-0.91) corresponded to higher GDS-15 scores. While TBI with LOC had the most neuropsychological associations, TBI without LOC had a negative effect on CogState Identification (β, 0.004; 95% CI, 0.001-0.01) and CogState One Back Test (β, 0.004; 95% CI, 0.0002-0.01). RHI predicted worse CogState One Back Test scores (β, 0.02; 95% CI, -0.01 to 0.05). There were RHI × TBI interaction effects on several neuropsychological subtests, and participants who had a history of both RHI and TBI with LOC had the greatest depression symptoms and worse cognition.

CONCLUSIONS

RHI and TBI independently contributed to worse mid- to later-life neuropsychiatric and cognitive functioning.

The role of mitochondrial bioenergetics and oxidative stress in depressive behavior in recurrent concussion model in mice

Traumatic brain injury (TBI) is a public health problem in which even though 80 to 90% of cases are considered mild, usually starts a sequence of neurological disorders that can last a considerable time. Most of the research of this injury has been focused on oxidative stress and functional deficits; however, mechanisms that underlie the development of neuropsychiatric disorders remain little researched. Due to this, the present authors decided to investigate whether recurrent concussion protocols alter depressive-like phenotype behavior, and whether mitochondria play an indispensable role in this behavior or not. The experimental data revealed, for the first time, that the present protocol of recurrent concussions (4, 7, and 10 injuries) in mice did not alter immobility time during tail suspension tests (TSTs), but decreased hippocampal mitochondrial respiration and increased expression of proteins such as nuclear factor erythroid 2-related factor 2 (Nrf2) and superoxide (SOD2). This experimental data suggests that bioenergetic changes elicited by recurrent concussion did not induce depressive-like behavior, but activated the transcription factor of responsive antioxidant elements (ARE) that delay or prevent secondary cascades in this neurological disease.

Extracellular Vesicles as Therapeutics for Brain Injury and Disease

Extracellular vesicles (EVs) are gaining tremendous importance in comprehending central nervous system (CNS) function and treating neurological disorders because of their role in intercellular communication and reparative processes, and suitability as drug delivery vehicles. Since EVs have lipid membranes, they cross the blood-brain barrier easily and communicate with target neurons and glia even deep inside the brain. EVs from various sources have been isolated, characterized, and tailored for promoting beneficial effects in conditions, such as brain injury and disease. Particularly, EVs isolated from mesenchymal stem cells and neural stem cells have shown promise for alleviating brain dysfunction after injury or disease. Such properties of stem cell-derived EVs have great importance for clinical applications, as EV therapy can avoid several concerns typically associated with cell therapy. This minireview confers the competence of EVs for improving brain function by modulating CNS injury and disease.

Alcohol consumption during adolescence alters the hippocampal response to traumatic brain injury

Binge drinking is the consumption of large volumes of alcohol in short periods and exerts its effects on the central nervous system, including the hippocampus. We have previously shown that binge drinking alters mitochondrial dynamics and induces neuroinflammation in the hippocampus of adolescent rats. Mild traumatic brain injury (mTBI), is regularly linked to alcohol consumption and share mechanisms of brain damage. In this context, we hypothesized that adolescent binge drinking could prime the development of brain damage generated by mTBI. We found that alcohol binge drinking induced by the "drinking in the dark" (DID) paradigm increases oxidative damage and astrocyte activation in the hippocampus of adolescent mice. Interestingly, adolescent animals submitted to DID showed decreased levels of mitofusin 2 that controls mitochondrial dynamics. When mTBI was evaluated as a second challenge, hippocampi from animals previously submitted to DID showed a reduction in dendritic spine number and a different spine profile. Mitochondrial performance could be compromised by alterations in mitochondrial fission in DID-mTBI animals. These data suggest that adolescent alcohol consumption can modify the progression of mTBI pathophysiology. We propose that mitochondrial impairment and oxidative damage could act as priming factors, modifying predisposition against mTBI effects.

Mass Spectrometry-Based Assay for Targeting Fifty-Two Proteins of Brain Origin in Cerebrospinal Fluid

Cerebrospinal fluid (CSF) is a circulatory fluid of the central nervous system and it can reflect the biochemical changes occurring in the brain. Although CSF retrieval through lumbar puncture is invasive, it remains the most commonly used fluid in exploring brain pathology as it is less complex and contains a higher concentration of brain-derived proteins than plasma (Reiber, H. Clin. Chim. Acta 2001, 310, 173-186; Macron et al. J. Proteome Res. 2018, 17, 4315-4319). We hypothesize that proteins produced by the brain will have diagnostic significance for brain pathologies. Hence, we expanded the previously in-house-developed 31-protein panel with more proteins classified as brain-specific by the Human Protein Atlas (HPA). Using the HPA, we selected 76 protein coding genes and screened CSF using liquid chromatography-mass spectrometry (LC-MS) and narrowed the protein list to candidates identified endogenously in CSF. Next, we developed a parallel reaction monitoring (PRM) assay for the 21 new proteins and merged it with the 31-protein assay developed earlier. In the process, we evaluated different screening strategies and optimized MS collision energies and ion isolation windows to achieve the highest possible analyte signal resulting in the PRM assay with an average linear dynamic range of 4.3 × 10³. We also assessed the extent of Asn (N)-Gln (Q) deamidation, N-terminal pyro-Glu (E) conversion, and Met (M) oxidation and found that deamidation can be misassigned without high mass accuracy and high-resolution settings. We also assessed how many of these proteins could be reliably measured in 10 individual patient CSF samples. Our approach allows us to measure the relative levels of 52 brain-derived proteins in CSF by a single LC-MS method. This new assay may have important applications in discovering CSF biomarkers for various neurological diseases.

Mesenchymal stem cell therapy for the treatment of traumatic brain injury: progress and prospects

Traumatic brain injury (TBI) is a major cause of injury-related mortality and morbidity in the USA and around the world. The survivors may suffer from cognitive and memory deficits, vision and hearing loss, movement disorders, and different psychological problems. The primary insult causes neuronal damage and activates astrocytes and microglia which evokes immune responses causing further damage to the brain. Clinical trials of drugs to recover the neuronal loss are not very successful. Regenerative approaches for TBI using mesenchymal stem cells (MSCs) seem promising. Results of preclinical research have shown that transplantation of MSCs reduced secondary neurodegeneration and neuroinflammation, promoted neurogenesis and angiogenesis, and improved functional outcome in the experimental animals. The functional improvement is not necessarily related to cell engraftment; rather, immunomodulation by molecular factors secreted by MSCs is responsible for the beneficial effects of this therapy. However, MSC therapy has a few drawbacks including tumor formation, which can be avoided by the use of MSC-derived exosomes. This review has focused on the research works published in the field of regenerative therapy using MSCs after TBI and its future direction.

Inflammatory Cytokines Associate With Neuroimaging After Acute Mild Traumatic Brain Injury

Introduction: Elevated levels of blood-based proinflammatory cytokines are linked to acute moderate to severe traumatic brain injuries (TBIs), yet less is known in acute mild (m)TBI cohorts. The current study examined whether blood-based cytokines can differentiate patients with mTBI, with and without neuroimaging findings (CT and MRI).

Material and Methods: Within 24 h of a mTBI, determined by a Glasgow Coma Scale (GCS) between 13 and 15, participants (n = 250) underwent a computed tomography (CT) and magnetic resonance imaging (MRI) scan and provided a blood sample. Participants were classified into three groups according to imaging findings; (1) CT+, (2) MRI+ (CT–), (3) Controls (CT– MRI–). Plasma levels of circulating cytokines (IL-6, IL-10, TNFα), and vascular endothelial growth factor (VEGF) were measured using an ultra-sensitive immunoassay.

Results: Concentrations of inflammatory cytokines (IL-6, TNFα) and VEGF were elevated in CT+, as well as MRI+ groups (p < 0.001), compared to controls, even after controlling for age, sex and cardiovascular disease (CVD)-related risk factors; hypertension, and hyperlipidemia. Post-concussive symptoms were associated with imaging groupings, but not inflammatory cytokines in this cohort. Levels of VEGF, IL-6, and TNFα differentiated patients with CT+ findings from controls, with the combined biomarker model (VEGF, IL-6, TNFα, and IL-10) showing good discriminatory power (AUC 0.92, 95% CI 0.87–0.97). IL-6 was a fair predictor of MRI+ findings compared to controls (AUC 0.70, 95% CI 0.60–0.78). Finally, the combined biomarker model discriminated patients with MRI+ from CT+ with an AUC of 0.71 (95% CI 0.62–0.80).

Conclusions: When combined, IL-6, TNFα, and VEGF may provide a promising biomarker cytokine panel to differentiate mTBI patients with CT+ imaging vs. controls. Singularly, IL-6 was a fair discriminator between each of the imaging groups. Future research directions may help elucidate mechanisms related to injury severity and potentially, recovery following an mTBI.

Losing the identity of a hockey player: the long-term effects of concussions

AIM

To describe what suffering multiple concussions meant for former semi-professional or professional hockey players who were forced to end their career.

RESULTS

Nine former Swedish hockey players, who once played on national or professional teams were interviewed. The interviews were analyzed with reference to hermeneutic phenomenology to interpret and explain their experiences. The theme of losing one's identity as a hockey player was constructed from five subthemes: being limited in everyday life, returning to the hockey stadium as soon as possible, forming a post career identity, lacking understanding and support, and preventing injuries by respecting other players.

CONCLUSION

The former hockey players struggled with developing their off-the-ice identities and with finding other sources of meaning for their lives.

Traumatic brain injuries induced pituitary dysfunction: a call for algorithms

Traumatic brain injury affects many people each year, resulting in a serious burden of devastating health consequences. Motor-vehicle and work-related accidents, falls, assaults, as well as sport activities are the most common causes of traumatic brain injuries. Consequently, they may lead to permanent or transient pituitary insufficiency that causes adverse changes in body composition, worrisome metabolic function, reduced bone density, and a significant decrease in one's quality of life. The prevalence of post-traumatic hypopituitarism is difficult to determine, and the exact mechanisms lying behind it remain unclear. Several probable hypotheses have been suggested. The diagnosis of pituitary dysfunction is very challenging both due to the common occurrence of brain injuries, the subtle character of clinical manifestations, the variable course of the disease, as well as the lack of proper diagnostic algorithms. Insufficiency of somatotropic axis is the most common abnormality, followed by presence of hypogonadism, hypothyroidism, hypocortisolism, and diabetes insipidus. The purpose of this review is to summarize the current state of knowledge about post-traumatic hypopituitarism. Moreover, based on available data and on our own clinical experience, we suggest an algorithm for the evaluation of post-traumatic hypopituitarism. In addition, well-designed studies are needed to further investigate the pathophysiology, epidemiology, and timing of pituitary dysfunction after a traumatic brain injury with the purpose of establishing appropriate standards of care.

Treatment of Depression After Traumatic Brain Injury: A Systematic Review Focused on Pharmacological and Neuromodulatory Interventions

BACKGROUND

Depression is the most common psychiatric sequela after traumatic brain injury (TBI) and poses a variety of treatment challenges. There is a lack of clinical trials focused on biological interventions used to manage TBI depression.

OBJECTIVE

The aim of this systematic review is to summarize the current evidence of psychotropic and neuromodulatory interventions used to treat TBI depression and to provide directions for future research.

METHODS

Key words were used to describe the following search terms: "traumatic brain injury", "depression", "pharmacological/drug therapy", and "neuromodulation". Studies focused on pharmacotherapy or neuromodulation in TBI depression were identified in 5 databases: Medline (PubMed), EMBASE (Embase.com), the Cochrane Library (Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, Cochrane Methodology Register), PsycINFO (EbscoHost), and Web of Science. Article inclusion/exclusion using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-based systematic protocol of extraction and evaluation was applied. Level of evidence for each study was determined using the American Academy of Neurology criteria.

RESULTS

The initial search provided 1473 citations. Twenty-two studies met inclusion criteria. Sixteen studies explored pharmacological interventions with emphasis on serotonergic agents. Results between studies were conflicting, and interventions did not always outperform placebos, although sertraline provided the highest level of evidence for treatment of TBI depression. Six studies examining neuromodulatory interventions show preliminary evidence of efficacy with a range of interventions and modes of delivery used.

CONCLUSIONS

Additional research including large-sample randomized-controlled trials using pharmacological, neuromodulation, or combination treatment is needed. These studies should incorporate premorbid psychosocial functioning, preinjury psychiatric disease, cognitive deficits, and functional recovery when examining outcomes.

Mechanism of Coup and Contrecoup Injuries Induced by a Knock-Out Punch

Primary Objective: The interaction of cerebrospinal fluid with the brain parenchyma in an impact scenario is studied. Research Design: A computational fluid-structure interaction model is used to simulate the interaction of cerebrospinal fluid with a comprehensive brain model. Methods and Procedures: The method of smoothed particle hydrodynamics is used to simulate the fluid flow, induced by the impact, simultaneously with finite element analysis to solve the large deformations in the brain model. Main Outcomes and Results: Mechanism of injury resulting in concussion is demonstrated. The locations with the highest stress values on the brain parenchyma are shown. Conclusions: Our simulations found that the damage to the brain resulting from the contrecoup injury is more severe than that resulting from the coup injury. Additionally, we show that the contrecoup injury does not always appear on the side opposite from where impact occurs.

Human neural stem cell transplant location-dependent neuroprotection and motor deficit amelioration in rats with penetrating traumatic brain injury

BACKGROUND

Penetrating traumatic brain injury induces chronic inflammation that drives persistent tissue loss long after injury. Absence of endogenous reparative neurogenesis and effective neuroprotective therapies render injury-induced disability an unmet need. Cell replacement via neural stem cell transplantation could potentially rebuild the tissue and alleviate penetrating traumatic brain injury disability. The optimal transplant location remains to be determined.

METHODS

To test if subacute human neural stem cell (hNSC) transplant location influences engraftment, lesion expansion, and motor deficits, rats (n = 10/group) were randomized to the following four groups (uninjured and three injured): group 1 (Gr1), uninjured with cell transplants (sham+hNSCs), 1-week postunilateral penetrating traumatic brain injury, after establishing motor deficit; group 2 (Gr2), treated with vehicle (media, no cells); group 3 (Gr3), hNSCs transplanted into lesion core (intra); and group 4 (Gr4), hNSCs transplanted into tissue surrounding the lesion (peri). All animals were immunosuppressed for 12 weeks and euthanized following motor assessment.

RESULTS

In Gr2, penetrating traumatic brain injury effect manifests as porencephalic cyst, 22.53 ± 2.87 (% of intact hemisphere), with p value of <0.0001 compared with uninjured Gr1. Group 3 lesion volume at 17.44 ± 2.11 did not differ significantly from Gr2 (p = 0.36), while Gr4 value, 9.17 ± 1.53, differed significantly (p = 0.0001). Engraftment and neuronal differentiation were significantly lower in the uninjured Gr1 (p < 0.05), compared with injured groups. However, there were no differences between Gr3 and Gr4. Significant increase in cortical tissue sparing (p = 0.03), including motor cortex (p = 0.005) was observed in Gr4 but not Gr3. Presence of transplant within lesion or in penumbra attenuated motor deficit development (p < 0.05) compared with Gr2.

CONCLUSION

In aggregate, injury milieu supports transplanted cell proliferation and differentiation independent of location. Unexpectedly, cortical sparing is transplant location dependent. Thus, apart from cell replacement and transplant mediated deficit amelioration, transplant location-dependent neuroprotection may be key to delaying onset or preventing development of injury-induced disability.

LEVEL OF EVIDENCE

Preclinical study evaluation of therapeutic intervention, level VI.

Progressive long-term spatial memory loss following repeat concussive and subconcussive brain injury in mice, associated with dorsal hippocampal neuron loss, microglial phenotype shift, and vascular abnormalities

There is considerable concern about the long‐term deleterious effects of repeat head trauma on cognition, but little is known about underlying mechanisms and pathology. To examine this, we delivered four air blasts to the left side of the mouse cranium, a week apart, with an intensity that causes deficits when delivered singly and considered “concussive,” or an intensity that does not yield significant deficits when delivered singly and considered “subconcussive.” Neither repeat concussive nor subconcussive blast produced spatial memory deficits at 4 months, but both yielded deficits at 14 months, and dorsal hippocampal neuron loss. Hierarchical cluster analysis of dorsal hippocampal microglia across the three groups based on morphology and expression of MHCII, CX3CR1, CD68 and IBA1 revealed five distinct phenotypes. Types 1A and 1B microglia were more common in sham mice, linked to better neuron survival and memory, and appeared mildly activated. By contrast, 2B and 2C microglia were more common in repeat concussive and subconcussive mice, linked to poorer neuron survival and memory, and characterized by low expression levels and attenuated processes, suggesting they were de‐activated and dysfunctional. In addition, endothelial cells in repeat concussive mice exhibited reduced CD31 and eNOS expression, which was correlated with the prevalence of type 2B and 2C microglia. Our findings suggest that both repeat concussive and subconcussive head injury engender progressive pathogenic processes, possibly through sustained effects on microglia that over time lead to increased prevalence of dysfunctional microglia, adversely affecting neurons and blood vessels, and thereby driving neurodegeneration and memory decline.

Neuronal Degeneration Impairs Rhythms Between Connected Microcircuits

Synchronization of neural activity across brain regions is critical to processes that include perception, learning, and memory. After traumatic brain injury (TBI), neuronal degeneration is one possible effect and can alter communication between neural circuits. Consequently, synchronization between neurons may change and can contribute to both lasting changes in functional brain networks and cognitive impairment in patients. However, fundamental principles relating exactly how TBI at the cellular scale affects synchronization of mesoscale circuits are not well understood. In this work, we use computational networks of Izhikevich integrate-and-fire neurons to study synchronized, oscillatory activity between clusters of neurons, which also adapt according to spike-timing-dependent plasticity (STDP). We study how the connections within and between these neuronal clusters change as unidirectional connections form between the two neuronal populations. In turn, we examine how neuronal deletion, intended to mimic the temporary or permanent loss of neurons in the mesoscale circuit, affects these dynamics. We determine synchronization of two neuronal circuits requires very modest connectivity between these populations; approximately 10% of neurons projecting from one circuit to another circuit will result in high synchronization. In addition, we find that synchronization level inversely affects the strength of connection between neuronal microcircuits - moderately synchronized microcircuits develop stronger intercluster connections than do highly synchronized circuits. Finally, we find that highly synchronized circuits are largely protected against the effects of neuronal deletion but may display changes in frequency properties across circuits with targeted neuronal loss. Together, our results suggest that strongly and weakly connected regions differ in their inherent resilience to damage and may serve different roles in a larger network.

Modulation of in vitro Brain Endothelium by Mechanical Trauma: Structural and Functional Restoration by Poloxamer 188

Brain injuries caused by an explosive blast or blunt force is typically presumed to associate with mechanical trauma to the brain tissue. Recent findings from our laboratory suggest that shockwaves produced by a blast can generate micron-sized bubbles in the tissue. The collapse of microbubbles (i.e., microcavitation) may induce a mechanical trauma and compromise the integrity of the blood-brain endothelium (BBE). To test our hypothesis, we engineered a BBE model to determine the effect of microbubbles on the structural and functional changes in the BBE. Using monolayers of mouse primary brain microvascular endothelial cells, the permeability coefficient was measured following simulated blast-induced microcavitation. This event down-regulated the expression of tight junction markers, disorganized the cell-cell junction, and increased permeability. Since poloxamers have been shown to rescue damaged cells, the cells were treated with the FDA-approved poloxamer 188 (P188). The results indicate P188 recovered the permeability, restored the tight junctions, and suppressed the expressions of matrix metalloproteinases. The biomimetic interface we developed appears to provide a systematic approach to replicate the structure and function of BBE, determine its alteration in response to traumatic brain injury, and test potential therapeutic treatments to repair the damaged brain endothelium.

Neurofilaments: The C-Reactive Protein of Neurology

Neurofilaments (NFs) are quickly becoming the biomarkers of choice in the field of neurology, suggesting their use as an unspecific screening marker, much like the use of elevated plasma C-reactive protein (CRP) in other fields. With sensitive techniques being readily available, evidence is growing regarding the diagnostic and prognostic value of NFs in many neurological disorders. Here, we review the latest literature on the structure and function of NFs and report the strengths and pitfalls of NFs as markers of neurodegeneration in the context of neurological diseases of the central and peripheral nervous systems.

Approaches to Monitor Circuit Disruption after Traumatic Brain Injury: Frontiers in Preclinical Research

Mild traumatic brain injury (TBI) often results in pathophysiological damage that can manifest as both acute and chronic neurological deficits. In an attempt to repair and reconnect disrupted circuits to compensate for loss of afferent and efferent connections, maladaptive circuitry is created and contributes to neurological deficits, including post-concussive symptoms. The TBI-induced pathology physically and metabolically changes the structure and function of neurons associated with behaviorally relevant circuit function. Complex neurological processing is governed, in part, by circuitry mediated by primary and modulatory neurotransmitter systems, where signaling is disrupted acutely and chronically after injury, and therefore serves as a primary target for treatment. Monitoring of neurotransmitter signaling in experimental models with technology empowered with improved temporal and spatial resolution is capable of recording in vivo extracellular neurotransmitter signaling in behaviorally relevant circuits. Here, we review preclinical evidence in TBI literature that implicates the role of neurotransmitter changes mediating circuit function that contributes to neurological deficits in the post-acute and chronic phases and methods developed for in vivo neurochemical monitoring. Coupling TBI models demonstrating chronic behavioral deficits with in vivo technologies capable of real-time monitoring of neurotransmitters provides an innovative approach to directly quantify and characterize neurotransmitter signaling as a universal consequence of TBI and the direct influence of pharmacological approaches on both behavior and signaling.

Traumatic Brain Injury: A Forensic Approach: A Literature Review

Traumatic brain injury (TBI) is the principal cause of invalidity and death in the population under 45 years of age worldwide. This mini-review aims to systematize the forensic approach in neuropathological studies, highlighting the proper elements to be noted during external, radiological, autoptical, and histological examinations with particular attention paid to immunohistochemistry and molecular biology. In the light of the results of this mini-review, an accurate forensic approach can be considered mandatory in the examination of suspected TBI with medico-legal importance, in order to gather all the possible evidence to corroborate the diagnosis of a lesion that may have caused, or contributed to, death. From this point of view, only the use of an evidence-based protocol can reach a suitable diagnosis, especially in those cases in which there are other neuropathological conditions (ischemia, neurodegeneration, neuro-inflammation, dementia) that may have played a role in death. This is even more relevant when corpses, in an advanced state of decomposition, are studied, where the radiological, macroscopic and histological analyses fail to give meaningful answers. In these cases, immune-histochemical and molecular biology diagnostics are of fundamental importance and a forensic neuropathologist has to know them. Particularly, MiRNAs are promising biomarkers for TBI both for brain damage identification and for medico-legal aspects, even if further investigations are required to validate the first experimental studies. In the same way, the genetic substrate should be examined during any forensic examination, considering its importance in the outcome of TBI.

Brain damage by trauma

Traumatic brain injury (TBI) represents a major clinical and economic challenge for health systems worldwide, and it is considered one of the leading causes of disability in young adults. The recent development of brain-computer interface (BCI) tools to target cognitive and motor impairments has led to the exploration of these techniques as potential therapeutic tools in patients with TBI. However, little evidence has been gathered so far to support applicability and efficacy of BCIs for TBI in a clinical setting. In the present chapter, results from studies using BCI approaches in conscious patients with TBI or in animal models of TBI as well as an overview of future directions in the use of BCIs to treat cognitive symptoms in this patient population will be presented.

Evaluating spatiotemporal microstructural alterations following diffuse traumatic brain injury

BACKGROUND

Diffuse traumatic brain injury (TBI) is known to lead to microstructural changes within both white and grey matter detected in vivo with diffusion tensor imaging (DTI). Numerous studies have shown alterations in fractional anisotropy (FA) and mean diffusivity (MD) within prominent white matter tracts, but few have linked these to changes within the grey matter with confirmation via histological assessment. This is especially important as alterations in the grey matter may be predictive of long-term functional deficits.

METHODS

A total of 33 male Sprague Dawley rats underwent severe closed-head TBI. Eight animals underwent tensor-based morphometry (TBM) and DTI at baseline (pre-TBI), 24 hours (24 h), 7, 14, and 30 days post-TBI. Immunohistochemical analysis for the detection of ionised calcium-binding adaptor molecule 1 (IBA1) to assess microglia number and percentage of activated cells, β-amyloid precursor protein (APP) as a marker of axonal injury, and myelin basic protein (MBP) to investigate myelination was performed at each time-point.

RESULTS

DTI showed significant alterations in FA and RD in numerous white matter tracts including the corpus callosum, internal and external capsule, and optic tract and in the grey-matter in the cortex, thalamus, and hippocampus, with the most significant effects observed at 14 D post-TBI. TBM confirmed volumetric changes within the hippocampus and thalamus. Changes in DTI were in line with significant axonal injury noted at 24 h post-injury via immunohistochemical analysis of APP, with widespread microglial activation seen within prominent white matter tracts and the grey matter, which persisted to 30 D within the hippocampus and thalamus. Microstructural alterations in MBP+ve fibres were also noted within the hippocampus and thalamus, as well as the cortex.

CONCLUSION

This study confirms the widespread effects of diffuse TBI on white matter tracts which could be detected via DTI and extends these findings to key grey matter regions, with a comprehensive investigation of the whole brain. In particular, the hippocampus and thalamus appear to be vulnerable to ongoing pathology post-TBI, with DTI able to detect these alterations supporting the clinical utility in evaluating these regions post-TBI.

The NLRP3 inflammasome: a new player in neurological diseases

Inflammasomes are supramolecular protein complexes implicated in the detection of pathogens or danger-associated molecules and are responsible for mounting the first line of innate immune response to counteract these signals and restore tissue homeostasis. Among different inflammasomes identified so far, NLRP3 is of main interest since mutations in Nlrp3 gene are associated with autoinflammatory diseases such as Muckle–Wells syndrome, neonatal onset multisystem inflammatory disease, and familial cold urticaria/autoinflammatory syndrome. On the other hand, whereas other inflammasomes are mainly detectors of specific molecular motifs, NLRP3 is acting as a general sensor of cellular perturbations including potassium efflux, lysosomal damage, and ROS production. Besides this central role of NLRP3 in inflammation, recent publications show that the NLRP3 inflammasome is also involved in the physiopathology of several neurological disorders including Alzheimer’s disease, Parkinson’s disease, and multiple sclerosis. This review gives an overview of the established functions of the NLRP3 inflammasome in mediating inflammation in macrophages and describes its recently discovered roles in neurological disorders in promoting neuroinflammation, as well as modulating key proteins mediating the disorders. Finally, we discuss the targeting of NLRP3 in neurological diseases and present some examples of NLRP3 inhibitors that could be used in neurological disorder treatments.

The functional roles of IGF-1 variants in the susceptibility and clinical outcomes of mild traumatic brain injury

BACKGROUND

Insulin-like growth factor 1 (IGF-1) is an important pleiotropic hormone that exerts neuroprotective and neuroreparative effects after a brain injury. However, the roles of IGF-1 variants in mild traumatic brain injury (mTBI) are not yet fully understood. This study attempted to elucidate the effects of IGF-1 variants on the risk and neuropsychiatric outcomes of mTBI.

METHODS

Based on 176 recruited mTBI patients and 1517 control subjects from the Taiwan Biobank project, we first compared the genotypic distributions of IGF-1 variants between the two groups. Then, we analyzed associations of IGF-1 variants with neuropsychiatric symptoms after mTBI, including anxiety, depression, dizziness, and sleep disturbances. Functional annotation of IGF-1 variants was also performed through bioinformatics databases.

RESULTS

The minor allele of rs7136446 was over-represented in mTBI patients compared to community-based control subjects. Patients carrying minor alleles of rs7136446 and rs972936 showed more dizziness and multiple neuropsychiatric symptoms after brain injury.

CONCLUSIONS

IGF-1 variants were associated with the risk and neuropsychiatric symptoms of mTBI. The findings highlight the important role of IGF-1 in the susceptibility and clinical outcomes of mTBI.

Traumatic brain injury triggers APP and Tau cleavage by delta-secretase, mediating Alzheimer's disease pathology

Traumatic brain injury (TBI) is associated in some studies with clinical dementia, and neuropathological features, including amyloid plaque deposition and Tau neurofibrillary degeneration commonly identified in Alzheimer's disease (AD). However, the molecular mechanisms linking TBI to AD remain unclear. Here we show that TBI activates transcription factor CCAAT/Enhancer Binding Protein Beta (C/EBPβ), increasing delta-secretase (AEP) expression. Activated AEP cleaves both APP and Tau at APP N585 and Tau N368 sites, respectively, which mediate AD pathogenesis by promoting Aβ production and Tau hyperphosphorylation and inducing neuroinflammation and neurotoxicity. Knockout of AEP or C/EBPβ diminishes TBI-induced AD-like pathology and cognitive impairment in the 3xTg AD mouse model. Remarkably, viral expression of AEP-resistant Tau N368A in the hippocampus of 3xTg mice also ameliorates the pathological and cognitive consequences of TBI. Finally, clinical TBI activates C/EBPβ and escalates AEP expression, leading to APP N585 and Tau N368 proteolytic cleavage in TBI patient brains. Hence, our findings support a potential role for AEP in linking TBI exposure with AD pathogenesis.

Disrupted brain functional hub and causal connectivity in acute mild traumatic brain injury

There have been an increasing number of functional magnetic resonance imaging (fMRI) reports on brain abnormalities in mild traumatic brain injury (mTBI) at different phases. However, the neural bases and cognitive impairment after acute mTBI are unclear. This study aimed to identify brain functional hubs and connectivity abnormalities in acute mTBI patients and their correlations with deficits in cognitive performance. Within seven days after brain injury, mTBI patients (n=55) and age-, sex-, and educational -matched healthy controls (HCs) (n=41) underwent resting-state fMRI scans and cognitive assessments. We derived functional connectivity (FC) strength of the whole-brain network using degree centrality (DC) and performed Granger causality analysis (GCA) to analyze causal connectivity patterns in acute mTBI. Compared with HCs, acute mTBI patients had significantly decreased network centrality in the left middle frontal gyrus (MFG). Additionally, acute mTBI showed decreased inflows from the left MFG to bilateral middle temporal gyrus (MTG), left medial superior frontal gyrus (mSFG), and left anterior cingulate cortex (ACC). Correlation analyses revealed that changes in network centrality and causal connectivity were associated with deficits in cognitive performance in mTBI. Our findings may help to provide a new perspective for understanding the neuropathophysiological mechanism of acute cognitive impairment after mTBI.

DNA repair deficiency and senescence in concussed professional athletes involved in contact sports

Mild traumatic brain injury (mTBI) leads to diverse symptoms including mood disorders, cognitive decline, and behavioral changes. In some individuals, these symptoms become chronic and persist in the long-term and can confer an increased risk of neurodegenerative disease and dementia diagnosis later in life. Despite the severity of its consequences, the pathophysiological mechanism of mTBI remains unknown. In this post-mortem case series, we assessed DNA damage-induced cellular senescence pathways in 38 professional athletes with a history of repeated mTBI and ten controls with no mTBI history. We assessed clinical presentation, neuropathological changes, load of DNA damage, morphological markers of cellular senescence, and expression of genes involved in DNA damage signaling, DNA repair, and cellular senescence including the senescence-associated secretory phenotype (SASP). Twenty-eight brains with past history of repeated mTBI history had DNA damage within ependymal cells, astrocytes, and oligodendrocytes. DNA damage burden was increased in brains with proteinopathy compared to those without. Cases also showed hallmark features of cellular senescence in glial cells including astrocytic swelling, beading of glial cell processes, loss of H3K27Me3 (trimethylation at lysine 27 of histone H3) and lamin B1 expression, and increased expression of cellular senescence and SASP pathways. Neurons showed a spectrum of changes including loss of emerin nuclear membrane expression, loss of Brahma-related gene-1 (BRG1 or SMARCA4) expression, loss of myelin basic protein (MBP) axonal expression, and translocation of intranuclear tau to the cytoplasm. Expression of DNA repair proteins was decreased in mTBI brains. mTBI brains showed substantial evidence of DNA damage and cellular senescence. Decreased expression of DNA repair genes suggests inefficient DNA repair pathways in this cohort, conferring susceptibly to cellular senescence and subsequent brain dysfunction after mTBI. We therefore suggest that brains of contact-sports athletes are characterized by deficient DNA repair and DNA damage-induced cellular senescence and propose that this may affect neurons and be the driver of brain dysfunction in mTBI, predisposing the progression to neurodegenerative diseases. This study provides novel targets for diagnostic and prognostic biomarkers, and represents viable targets for future treatments.

Increased short- and long-term risk of sleep disorders in people with traumatic brain injury

This study aims to evaluate the relationship between traumatic brain injury (TBI) and sleep disorders (SDs). We first initiated a questionnaire-based clinical survey to assess sleep problems in the early stage after a TBI, followed by a population-based cohort study to evaluate the long-term risk of SDs in TBI patients. For short-term clinical survey, mild (m)TBI patients and healthy controls were recruited to evaluate the sleep quality and daytime sleepiness using the Pittsburg Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS) within two weeks after a TBI. For long-term observation, a 5-year nationwide population-based cohort study that utilized a large administrative database was conducted. In the short-term survey, 236 mTBI patients and 223 controls were analyzed. Total scores of the PSQI and ESS were significantly higher in mTBI patients than in the controls. In the long-term cohort study, 6932 TBI cases and 34,660 matched controls were included. TBI cases had a 1.36-fold greater risk of SDs compared to the non-TBI controls during the 5-year follow-up period. Results showed that patients with TBI had a significantly higher risk of SDs than did controls both in the early stage and during a 5-year follow-up period.

Cannabis in the Treatment of Traumatic Brain Injury: A Primer for Clinicians

Our clinical experience at a specialized brain injury clinic suggests that numerous patients with traumatic brain injury (TBI) are using cannabis to alleviate their symptoms. While this patient population often inquires about the evidence of using cannabis post-head injury for the neurosensory, neurocognitive, and neuropsychiatric sequelae, most health professionals have little to no knowledge of this evidence. Given the recent legalization of recreational cannabis in Canada, questions and guidance related to cannabis use following a TBI are likely to become more common. This article reviews the evidence for cannabis use in psychiatric disorders with or without TBI. Overall, we found that the evidence for the use of cannabis among TBI patients is sparse and that patients tend to have little knowledge of the proven benefits and diverse effects of cannabis use. We feel this paper can serve as a stepping stone for future studies that explore the impact of cannabis use in a TBI population and can guide clinicians in advising their patients.

Nanozyme-Based Bandage with Single-Atom Catalysis for Brain Trauma

Neurotrauma is one of the most serious traumatic injuries, which can induce an excess amount of reactive oxygen and nitrogen species (RONS) around the wound, triggering a series of biochemical responses and neuroinflammation. Traditional antioxidant-based bandages can effectively decrease infection via preventing oxidative stress, but its effectiveness is limited to a short period of time due to the rapid loss of electron-donating ability. Herein, we developed a nanozyme-based bandage using single-atom Pt/CeO₂ with a persistent catalytic activity for noninvasive treatment of neurotrauma. Single-atom Pt induced the lattice expansion and preferred distribution on (111) facets of CeO₂, enormously increasing the endogenous catalytic activity. Pt/CeO₂ showed a 2-10 times higher scavenging activity against RONS as well as 3-10 times higher multienzyme activities compared to CeO₂ clusters. The single-atom Pt/CeO₂ retained the long-lasting catalytic activity for up to a month without obvious decay due to enhanced electron donation through the Mars-van Krevelen reaction. In vivo studies disclosed that the nanozyme-based bandage at the single-atom level can significantly improve the wound healing of neurotrauma and reduce neuroinflammation.

Reduced Neuron-Specific Enolase Levels in Chronic Severe Traumatic Brain Injury

Growing evidence suggests that pathophysiological mechanisms leading to neurodegeneration and neuronal loss take place during the chronic phase of a severe traumatic brain injury (TBI). In this study we evaluated a well-established marker of brain injury, the neuron-specific enolase (NSE), in the serum of 51 patients with severe TBI (86% males, mean age 33.8 ± 11.1 years). All patients' samples were available from a previous study and the mean time between TBI and blood sample collection was 23.2 ± 31.5 months (28 patients were evaluated within 12 months of TBI and 23 patients were evaluated ≥12 months after TBI). Patients' NSE levels were compared with those obtained from 30 age and sex-matched healthy controls (87% males, 33.7 ± 11.3 years). We found that NSE levels were significantly lower in patients (median 3.2 ng/mL; 25th, 75th percentile 2.5, 5.1) than in healthy controls (median 4.1 ng/mL; 25th, 75th percentile 3.1, 7.5) (p = 0.026). This finding was mainly driven by data from the chronic patients, that is, those who experienced their TBI at least 12 months before the evaluation. Indeed, these patients had significantly lower NSE levels (median 2.6 ng/mL; 25th, 75th percentile 1.9, 4) than healthy controls (p < 0.01). On the other hand, NSE levels evaluated in patients <12 months from TBI (median 3.9 ng/mL; 25th, 75th percentile 2.8, 5.7) did not significantly differ from controls (p = 0.3). These findings possibly reflect a progressive brain atrophy with reduced baseline NSE release in the chronic phase of a severe TBI.

Magnetic Resonance Imaging as a Biomarker in Rodent Peripheral Nerve Injury Models Reveals an Age-Related Impairment of Nerve Regeneration

Assessment of myelin integrity in peripheral nerve injuries and pathologies has largely been limited to post-mortem analysis owing to the difficulty in obtaining biopsies without affecting nerve function. This is further encumbered  by the small size of the tissue and its location. Therefore, the development of robust, non-invasive methods is highly attractive. In this study, we used magnetic resonance imaging (MRI) techniques, including magnetization transfer ratio (MTR), to longitudinally and non-invasively characterize both the sciatic nerve crush and lysolecithin (LCP) demyelination models of peripheral nerve injury in rodents. Electrophysiological, gene expression and histological assessments complemented the extensive MRI analyses in young and aged animals. In the nerve crush model, MTR analysis indicated a slower recovery in regions distal to the site of injury in aged animals, as well as incomplete recovery at six weeks post-crush when analyzing across the entire nerve surface. Similar regional impairments were also found in the LCP demyelination model. This research underlines the power of MTR for the study of peripheral nerve injury in small tissues such as the sciatic nerve of rodents and contributes new knowledge to the effect of aging on recovery after injury. A particular advantage of the approach is the translational potential to human neuropathies.

Tau Pathology in Chronic Traumatic Encephalopathy and Alzheimer's Disease: Similarities and Differences

Traumatic brain injury (TBI) has been associated with the development of Alzheimer's disease (AD) because these conditions share common pathological hallmarks: amyloid-β and hyperphosphorylated tau accumulation. However, given recent data it is uncertain if a history of TBI leads to the development of AD. Moreover, chronic traumatic encephalopathy (CTE), caused by repetitive mild TBI and characterized by progressive neurodegeneration with hyperphosphorylated tau, has come to be recognized as distinct from AD. Therefore, it is important to elucidate the clinical outcomes and molecular mechanisms underlying tau pathology following TBI. We summarize the histopathological features and clinical course of TBI in CTE, comparing the tau pathology with that in AD. Following brain injury, diffuse axonal injury, and hyperphosphorylated tau aggregates are observed within a shorter period than in AD. Hyperphosphorylated tau deposition usually begins in the perivascular area of the sulci in the cerebral cortex, then spreads unevenly in the cortex in CTE, while AD shows diffuse distribution of hyperphosphorylated tau in the cortical areas. We also highlight the molecular profile of tau and the implications of tau progression throughout the brain in both diseases. Tau contains phosphorylation sites common to both conditions. In particular, phosphorylation at Thr²³¹ triggers a conformational change to the toxic cis form of tau, which is suggested to drive neurodegeneration. Although the mechanism of rapid tau accumulation remains unknown, the structural diversity of tau might result in these different outcomes. Finally, future perspectives on CTE in terms of tau reduction are discussed.

Neurodegenerative disorders and sterile inflammation: lessons from a Drosophila model

Central nervous system (CNS)-related disorders, including neurodegenerative diseases, are common but difficult to treat. As effective medical interventions are limited, those diseases will likely continue adversely affecting people's health. There is evidence that the hyperactivation of innate immunity is a hallmark of most neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and polyglutamine diseases. In mammalian and fly CNS, the presence of noninfectious ligands, including danger-associated molecular patterns, is recognized by (micro)glial cells, inducing the expression of proinflammatory cytokines. Such inflammation may contribute to the onset and progression of neurodegenerative states. Studies using fruit flies have shed light on the types of signals, receptors and cells responsible for inducing the inflammation that leads to neurodegeneration. Researchers are using fly models to assess the mechanisms of sterile inflammation in the brain and its link to progressive neurodegeneration. Given the similarity of its physiological system and biochemical function to those of mammals, especially in activating and regulating innate immune signalling, Drosophila can be a versatile model system for studying the mechanisms and biological significance of sterile inflammatory responses in the pathogenesis of neurodegenerative diseases. Such knowledge would greatly facilitate the quest for a novel effective treatment for neurodegenerative diseases.

Using computerized tomography perfusion to measure cerebral hemodynamics following treatment of traumatic brain injury in rabbits

The present study aimed to investigate the use of computerized tomography (CT) perfusion for evaluating cerebral hemodynamics following traumatic brain injury (TBI) in rabbits. The animals were randomly assigned into four groups (n=10 animals/group): i) Control, ii) TBI, iii) TBI + common decompression and iv) TBI + controlled decompression groups. A TBI model was established in rabbits using epidural balloon inflation. In the groups receiving intervention, animals were provided common decompression or controlled decompression treatments. Conventional CT and CT perfusion scanning were performed, with cerebral hemodynamic indices, including regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV) and mean transit time (MTT) being measured. Blood-brain barrier (BBB) permeability was evaluated using Evans blue staining. Compared with those in the control group, rCBF and rCBV values of the bilateral temporal lobes and basal ganglion in the TBI, TBI + common decompression and TBI + controlled decompression groups were significantly lower, whereas the MTT values were markedly prolonged and Evans blue dye content was greatly increased (P<0.01). Controlled decompression was demonstrated to be more potent than common decompression for preventing TBI-induced decline in rCBF and rCBV values in the bilateral temporal lobes and basal ganglion, as well as reversing TBI-induced extension of MTT in the bilateral temporal lobes (P<0.01 vs. TBI group). However, neither common nor controlled decompression could reduce TBI-induced increase in BBB permeability. In conclusion, these findings indicate that CT perfusion may be used to monitor cerebral hemodynamics following TBI in rabbits. Controlled decompression was deduced to be more potent than common decompression for preventing abnormalities in cerebral hemodynamics after TBI.

Traumatic Brain Injury Induces Tau Aggregation and Spreading

The misfolding and aggregation of tau protein into neurofibrillary tangles is the main underlying hallmark of tauopathies. Most tauopathies have a sporadic origin and can be associated with multiple risk factors. Traumatic brain injury (TBI) has been suggested as a risk factor for tauopathies by triggering disease onset and facilitating its progression. Several studies indicate that TBI seems to be a risk factor to development of Alzheimer disease and chronic traumatic encephalopathy, because there is a relationship of TBI severity and propensity to development of these illnesses. In this study, we evaluated whether moderate to severe TBI can trigger the initial formation of pathological tau that would induce the development of the pathology throughout the brain. To this end, we subjected tau transgenic mice to TBI and assessed tau phosphorylation and aggregation pattern to create a spatial heat map of tau deposition and spreading in the brain. Our results suggest that brain injured tau transgenic mice have an accelerated tau pathology in different brain regions that increases over time compared with sham mice. The appearance of pathological tau occurs in regions distant to the injury area that are connected synaptically, suggesting dissemination of tau aggregates. Overall, this work posits TBI as a risk factor for tauopathies through the induction of tau hyperphosphorylation and aggregation.

Dynamic Thermal Mapping of Localized Therapeutic Hypothermia in the Brain

Although whole body cooling is used widely to provide therapeutic hypothermia for the brain, there are undesirable clinical side effects. Selective brain cooling may allow for rapid and controllable neuroprotection while mitigating these undesirable side effects. We evaluated an innovative cerebrospinal fluid (CSF) cooling platform that utilizes chilled saline pumped through surgically implanted intraventricular catheters to induce hypothermia. Magnetic resonance thermal imaging of the healthy sheep brain (n = 4) at 7.0T provided dynamic temperature measurements from the whole brain. Global brain temperature was 38.5 ± 0.8°C at baseline (body temperature of 39.2 ± 0.4°C), and decreased by 3.1 ± 0.3°C over ∼30 min of cooling (p < 0.0001). Significant cooling was achieved in all defined regions across both the ipsilateral and contralateral hemispheres relative to catheter placement. On cooling cessation, global brain temperature increased by 3.1 ± 0.2°C over ∼20 min (p < 0.0001). Rapid and synchronized temperature fall/rise on cooling onset/offset was observed reproducibly with rates ranging from 0.06-0.21°C/min, where rewarming was faster than cooling (p < 0.0001) signifying the importance of thermoregulation in the brain. Although core regions (including the subcortex, midbrain, olfactory tract, temporal lobe, occipital lobe, and parahippocampal cortex) had slightly warmer (∼0.2°C) baseline temperatures, after cooling, temperatures reached the same level as the non-core regions (35.6 ± 0.2°C), indicating the cooling effectiveness of the CSF-based cooling device. In summary, CSF-based intraventricular cooling reliably reduces temperature in all identified brain regions to levels known to be neuroprotective, while maintaining overall systemic normothermia. Dynamic thermal mapping provides high spatiotemporal temperature measurements that can aid in optimizing selective neuroprotective protocols.

Vision impairment after traumatic brain injury: present knowledge and future directions

Traumatic brain injury (TBI) is a major cause of mortality and morbidity in the USA as well as in the world. As a result of TBI, the visual system is also affected often causing complete or partial visual loss, which in turn affects the quality of life. It may also lead to ocular motor dysfunction, defective accommodation, and impaired visual perception. As a part of the therapeutic strategy, early rehabilitative optometric intervention is important. Orthoptic therapy, medication, stem cell therapy, motor and attention trainings are the available treatment options. Gene therapy is one of the most promising emerging strategies. Use of state-of-the-art nanomedicine approaches to deliver drug(s) and/or gene(s) might enhance the therapeutic efficacy of the present and future modalities. More research is needed in these fields to improve the outcome of this debilitating condition. This review focuses on different visual pathologies caused by TBI, advances in pre-clinical and clinical research, and available treatment options.