Repeat traumatic brain injury in the developing brain

A Novel Experimental Approach for the Measurement of Vibration-Induced Changes in the Rheological Properties of Ex Vivo Ovine Brain Tissue

Increased incidence of traumatic brain injury (TBI) imposes a growing need to understand the pathology of brain trauma. A correlation between the incidence of multiple brain traumas and rates of behavioural and cognitive deficiencies has been identified amongst people that experienced multiple TBI events. Mechanically, repetitive TBIs may affect brain tissue in a similar way to cyclic loading. Hence, the potential susceptibility of brain tissue to mechanical fatigue is of interest. Although temporal changes in ovine brain tissue viscoelasticity and biological fatigue of other tissues such as tendons and arteries have been investigated, no methodology currently exists to cyclically load ex vivo brain tissue. A novel rheology-based approach found a consistent, initial stiffening response of the brain tissue before a notable softening when subjected to a subsequential cyclic rotational shear. History dependence of the mechanical properties of brain tissue indicates susceptibility to mechanical fatigue. Results from this investigation increase understanding of the fatigue properties of brain tissue and could be used to strengthen therapy and prevention of TBI, or computational models of repetitive head injuries.

Multiple Head Rotations Result in Persistent Gait Alterations in Piglets

Multiple/repeated mild traumatic brain injury (mTBI) in young children can cause long-term gait impairments and affect the developmental course of motor control. Using our swine model for mTBI in young children, our aim was to (i) establish a reference range (RR) for each parameter to validate injury and track recovery, and (ii) evaluate changes in gait patterns following a single and multiple (5×) sagittal rapid non-impact head rotation (RNR). Gait patterns were studied in four groups of 4-week-old Yorkshire swine: healthy (n = 18), anesthesia-only sham (n = 8), single RNR injury (n = 12) and multiple RNR injury (n = 11). Results were evaluated pre-injury and at 1, 4, and 7 days post-injury. RR reliability was validated using additional healthy animals (n = 6). Repeated mTBI produced significant increases in gait time, cycle time, and stance time, as well as decreases in gait velocity and cadence, on Day One post-injury compared to pre-injury, and these remained significantly altered at Day Four and Day Seven post-injury. The gait metrics of the repeated TBI group also significantly fell outside the healthy RR on Day One, with some recovery by Day Four, while many remained altered at Day Seven. Only a bilateral decrease in hind stride length was observed at Day Four in our single RNR group compared to pre-injury. In sum, repeated and single sagittal TBI can significantly impair motor performance, and gait metrics can serve as reliable, objective, quantitative functional assessments in a juvenile porcine RNR TBI model.

Piecewise Multivariate Linearity Between Kinematic Features and Cumulative Strain Damage Measure (CSDM) Across Different Types of Head Impacts

In a previous study, we found that the relationship between brain strain and kinematic features cannot be described by a generalized linear model across different types of head impacts. In this study, we investigate if such a linear relationship exists when partitioning head impacts using a data-driven approach. We applied the K-means clustering method to partition 3161 impacts from various sources including simulation, college football, mixed martial arts, and car crashes. We found piecewise multivariate linearity between the cumulative strain damage (CSDM; assessed at the threshold of 0.15) and head kinematic features. Compared with the linear regression models without partition and the partition according to the types of head impacts, K-means-based data-driven partition showed significantly higher CSDM regression accuracy, which suggested the presence of piecewise multivariate linearity across types of head impacts. Additionally, we compared the piecewise linearity with the partitions based on individual features used in clustering. We found that the partition with maximum angular acceleration magnitude at 4706 rad/s² led to the highest piecewise linearity. This study may contribute to an improved method for the rapid prediction of CSDM in the future.

Effectiveness of telehealth interventions among traumatic brain injury survivors: A systematic review and meta-analysis

INTRODUCTION

Traumatic brain injury (TBI) represents a major cause of death and disability worldwide. Brain damage is associated with physical and psychological difficulties among TBI survivors. Diverse face-to-face and telehealth programs exist to help survivors cope with these burdens. However, the effectiveness of telehealth interventions among TBI survivors remains inconclusive.

METHODS

A systematic review and meta-analysis of randomized control trials were conducted. Relevant full-text articles were retrieved from seven databases, from database inception to January 2022, including Academic Search Complete, CINAHL, EMBASE, Cochrane, MEDLINE, PubMed, and Web of Science. Bias was assessed with the revised Cochrane risk-of-bias tool for randomized trials. A meta-analysis was performed using a random-effects model to calculate the pooled effect size of telehealth interventions for TBI survivors. STATA 16.0 was used for statistical analysis.

RESULTS

In total, 17 studies (N = 3158) applying telehealth interventions among TBI survivors were included in the analysis. Telehealth interventions decreased neurobehavioural symptom (standardized mean difference: -0.13; 95% confidence interval [CI]: -0.36 to 0.10), reduce depression (standardized mean difference: -0.32; 95% CI: -0.79 to 0.14), and increase symptom management self-efficacy (standardized mean difference: 0.22; 95% CI: 0.02-0.42).

DISCUSSION

Telehealth interventions are promising avenues for healthcare delivery due to advances in technology and information. Telehealth programs may represent windows of opportunity, combining traditional treatment with rehabilitation to increase symptom management self-efficacy among TBI patients during recovery. Future telehealth programs can focus on developing the contents of telehealth modules based on evidence from this study.

Recovery From Repeat Mild Traumatic Brain Injury in Adolescent Rats Is Dependent on Pre-injury Activity State

Adolescents and young adults have the highest incidence of mild traumatic brain injury (mTBI); sport-related activities are a major contributor. Roughly a third of these patients diagnosed with mTBI are estimated to have received a subsequent repeat mTBI (rTBI). Previously, animal studies have only modeled mTBI in sedentary animals. This study utilizes physical activity as a dependent variable prior to rTBI in adolescent rats by allowing voluntary exercise in males, establishing the rat athlete (rathlete). Rats were given access to locked or functional running wheels for 10 d prior to sham or rTBI injury. Following rTBI, rathletes were allowed voluntary access to running wheels beginning on different days post-injury: no run (rTBI+no run), immediate run (rTBI+Immed), or 3 day delay (rTBI+3dd). Rats were tested for motor and cognitive-behavioral (anxiety, social, memory) and mechanosensory (allodynia) dysfunction using a novel rat standardized concussion assessment tool on post-injury days 1,3,5,7, and 10. Protein expression of brain derived neurotrophic factor (BDNF) and proliferator-activated gamma coactivator 1-alpha (PGC1α) was measured in the parietal cortex, hippocampus, and gastrocnemius muscle. Sedentary shams displayed lower anxiety-like behaviors compared to rathlete shams on all testing days. BDNF and PGC1α levels increased in the parietal cortex and hippocampus with voluntary exercise. In rTBI rathletes, the rTBI+Immed group showed impaired social behavior, memory impairment in novel object recognition, and increased immobility compared to rathlete shams. All rats showed greater neuropathic mechanosensory sensitivity than previously published uninjured adults, with rTBI+3dd showing greatest sensitivity. These results demonstrate that voluntary exercise changes baseline functioning of the brain, and that among rTBI rathletes, delayed return to activity improved cognitive recovery.

What is the risk of recurrent concussion in children and adolescents aged 5-18 years? A systematic review and meta-analysis

OBJECTIVE

We aimed to examine the risk of concussion in children with a previous history of concussion.

DESIGN

Systematic review and meta-analysis. The primary outcome was number of children with and without a previous lifetime history of concussion who sustained a diagnosed concussion within each study period. Risk of bias was assessed using the Newcastle-Ottawa Scale. A random effects model was used to estimate a pooled risk ratio (RR) with corresponding 95% CIs; results were summarised in forest plots.

DATA SOURCES

Four electronic databases (MEDLINE, Embase, CINAHL, SPORTDiscus) and selected reference lists were searched (PROSPERO registration No CRD42019135462).

ELIGIBILITY CRITERIA

Original English language peer-reviewed publications that compared concussion risk in children aged 5-18 years with and without a previous concussion history in which risk estimates were reported or able to be calculated.

RESULTS

Of 732 identified studies, 7 studies representing 23 411 children (risk of bias range, 7-9; maximum possible score=9) were included for meta-analysis. Pooled risk of sustaining a concussion was more than three times greater in children with a previous concussion compared with those with no previous concussion (RR=3.64; 95% CI: 2.68 to 4.96; p<0.0001; I ²=90.55%). Unreported sex-stratified data precluded direct comparison of concussion risk in male versus female athletes.

CONCLUSION

Previously concussed children have four times the risk of sustaining a concussion compared with those with no previous concussion history. This should be a consideration for clinicians in return to sport decision-making. Future studies examining subsequent recurrent concussion in youth sports must consider sex differences.

Influence of Sociodemographic, Premorbid, and Injury-Related Factors on Post-Concussion Symptoms after Traumatic Brain Injury

BACKGROUND

Post-concussion symptoms (PCS) are often reported as consequences of mild and moderate traumatic brain injury (TBI), but these symptoms are not well documented in severe TBI. There is a lack of agreement as to which factors and covariates affect the occurrence, frequency, and intensity of PCS among TBI severity groups. The present study therefore aims to examine the association between sociodemographic, premorbid, and injury-related factors and PCS.

METHODS

A total of 1391 individuals (65% male) from the CENTER-TBI study were included in the analyses. The occurrence, frequency (number of PCS), and intensity (severity) of PCS were assessed using the Rivermead Post-concussion Symptoms Questionnaire (RPQ) at six months after TBI. To examine the association between selected factors (age, sex, living situation, employment status, educational background, injury and TBI severity, and premorbid problems) and PCS, a zero-inflated negative binomial model (ZINB) for occurrence and frequency of PCS and a standard negative binomial regression (NB) for intensity were applied.

RESULTS

Of the total sample, 72% of individuals after TBI reported suffering from some form of PCS, with fatigue being the most frequent among all TBI severity groups, followed by forgetfulness, and poor concentration. Different factors contributed to the probability of occurrence, frequency, and intensity of PCS. While the occurrence of PCS seemed to be independent of the age and sex of the individuals, both the frequency and intensity of PCS are associated with them. Both injury and TBI severity influence the occurrence and frequency of PCS, but are associated less with its intensity (except "acute" symptoms such as nausea, vomiting, and headaches). Analyses focusing on the mTBI subgroup only yielded results comparable to those of the total sample.

DISCUSSION

In line with previous studies, the results support a multifactorial etiology of PCS and show the importance of differentiating between their occurrence, frequency, and intensity to better provide appropriate treatment for individual subgroups with different symptoms (e.g., multiple PCS or more intense PCS). Although PCS often occur in mild to moderate TBI, individuals after severe TBI also suffer from PCS or post-concussion-like symptoms that require appropriate treatment. The chosen statistical approaches (i.e., ZINB and NB models) permit an ameliorated differentiation between outcomes (occurrence, frequency, and intensity of PCS) and should be used more widely in TBI research.

Examining the Effects of Anabolic-Androgenic Steroids on Repetitive Mild Traumatic Brain Injury (RmTBI) Outcomes in Adolescent Rats

Background: Repetitive mild traumatic brain injury (RmTBI) is increasingly common in adolescents. Anabolic–androgenic steroid (AAS) consumption among younger professional athletes is a significant risk factor for impaired neurodevelopment. Given the increased rates and overlapping symptomology of RmTBI and AAS use, we sought to investigate the behavioural and neuropathological outcomes associated with the AAS Metandienone (Met) and RmTBI on rats. Methods: Rats received either Met or placebo and were then administered RmTBIs or sham injuries, followed by a behavioural test battery. Post-mortem MRI was conducted to examine markers of brain integrity and qRT-PCR assessed mRNA expression of markers for neurodevelopment, neuroinflammation, stress responses, and repair processes. Results: Although AAS and RmTBI did not produce cumulative deficits, AAS use was associated with detrimental outcomes including changes to depression, aggression, and memory; prefrontal cortex (PFC) atrophy and amygdala (AMYG) enlargement; damaged white matter integrity in the corpus callosum; and altered mRNA expression in the PFC and AMYG. RmTBI affected general activity and contributed to PFC atrophy. Conclusions: Findings corroborate previous results indicating that RmTBI negatively impacts neurodevelopment but also demonstrates that AAS results in significant neuropathological insult to the developing brain.

(-)-Phenserine tartrate (PhenT) as a treatment for traumatic brain injury

Aim

Traumatic brain injury (TBI) is one of the most common causes of morbidity and mortality of both young adults and the elderly, and is a key contributing factor in about 30% of all injury‐associated deaths occurring within the United States of America. Albeit substantial impact has been made to improve our comprehension of the mechanisms that underpin the primary and secondary injury stages initiated by a TBI incident, this knowledge has yet to successfully translate into the development of an effective TBI pharmacological treatment. Developing consent suggests that a TBI can concomitantly trigger multiple TBI‐linked cascades that then progress in parallel and, if correct, the multifactorial nature of TBI would make the discovery of a single effective mechanism‐targeted drug unlikely.

Discussion

We review recent data indicating that the small molecular weight drug (−)‐phenserine tartrate (PhenT), originally developed for Alzheimer's disease (AD), effectively inhibits a broad range of mechanisms pertinent to mild (m) and moderate (mod)TBI, which in combination underpin the ensuing cognitive and motor impairments. In cellular and animal models at clinically translatable doses, PhenT mitigated mTBI‐ and modTBI‐induced programmed neuronal cell death (PNCD), oxidative stress, glutamate excitotoxicity, neuroinflammation, and effectively reversed injury‐induced gene pathways leading to chronic neurodegeneration. In addition to proving efficacious in well‐characterized animal TBI models, significantly mitigating cognitive and motor impairments, the drug also has demonstrated neuroprotective actions against ischemic stroke and the organophosphorus nerve agent and chemical weapon, soman.

Conclusion

In the light of its tolerability in AD clinical trials, PhenT is an agent that can be fast‐tracked for evaluation in not only civilian TBI, but also as a potentially protective agent in battlefield conditions where TBI and chemical weapon exposure are increasingly jointly occurring.

(-)-Phenserine and the prevention of pre-programmed cell death and neuroinflammation in mild traumatic brain injury and Alzheimer's disease challenged mice

Mild traumatic brain injury (mTBI) is a risk factor for neurodegenerative disorders, such as Alzheimer's disease (AD) and Parkinson's disease (PD). TBI-derived neuropathologies are promoted by inflammatory processes: chronic microgliosis and release of pro-inflammatory cytokines that further promote neuronal dysfunction and loss. Herein, we evaluated the effect on pre-programmed cell death/neuroinflammation/synaptic integrity and function of (-)-Phenserine tartrate (Phen), an agent originally developed for AD. This was studied at two clinically translatable doses (2.5 and 5.0 mg/kg, BID), in a weight drop (concussive) mTBI model in wild type (WT) and AD APP/PSEN1 transgenic mice. Phen mitigated mTBI-induced cognitive impairment, assessed by Novel Object Recognition and Y-maze behavioral paradigms, in WT mice. Phen fully abated mTBI-induced neurodegeneration, evaluated by counting Fluoro-Jade C-positive (FJC+) cells, in hippocampus and cortex of WT mice. In APP/PSEN1 mice, degenerating cell counts were consistently greater across all experimental groups vs. WT mice. mTBI elevated FJC+ cell counts vs. the APP/PSEN1 control (sham) group, and Phen similarly mitigated this. Anti-inflammatory effects on microglial activation (IBA1-immunoreactivity (IR)) and the pro-inflammatory cytokine TNF-α were evaluated. mTBI increased IBA1-IR and TNF-α/IBA1 colocalization vs. sham, both in WT and APP/PSEN1 mice. Phen decreased IBA1-IR throughout hippocampi and cortices of WT mice, and in cortices of AD mice. Phen, likewise, reduced levels of IBA1/TNF-α-IR colocalization volume across all areas in WT animals, with a similar trend in APP/PSEN1 mice. Actions on astrocyte activation by mTBI were followed by evaluating GFAP, and were similarly mitigated by Phen. Synaptic density was evaluated by quantifying PSD-95+ dendritic spines and Synaptophysin (Syn)-IR. Both were significantly reduced in mTBI vs. sham in both WT and APP/PSEN1 mice. Phen fully reversed the PSD-95+ spine loss in WT and Syn-IR decrease in both WT and APP/PSEN1 mice. To associate immunohistochemical changes in synaptic markers with function, hippocampal long term potentiation (LTP) was induced in WT mice. LTP was impaired by mTBI, and this impairment was mitigated by Phen. In synopsis, clinically translatable doses of Phen ameliorated mTBI-mediated pre-programmed cell death/neuroinflammation/synaptic dysfunction in WT mice, consistent with fully mitigating mTBI-induced cognitive impairments. Phen additionally demonstrated positive actions in the more pathologic brain microenvironment of AD mice, further supporting consideration of its repurposing as a treatment for mTBI.

Greater neurodegeneration and behavioral deficits after single closed head traumatic brain injury in adolescent versus adult male mice

Traumatic brain injury (TBI) is a major public health concern affecting 2.8 million people per year in the United States, of whom about 1 million are children under 19 years old. Animal models of TBI have been developed and used in multiple ages of animals, but direct comparisons of adult and adolescent populations are rare. The current studies were undertaken to directly compare outcomes between adult and adolescent male mice, using a closed head, single-impact model of TBI. Six-week-old adolescent and 9-week-old adult male mice were subjected to mild-moderate TBI. Histological measures for neurodegeneration, gliosis, and microglial neuroinflammation, and behavioral tests of locomotion and memory were performed. Adolescent TBI mice have increased mortality (Χ²  = 20.72, p < 0.001) compared to adults. There is also evidence of hippocampal neurodegeneration in adolescents that is not present in adults. Hippocampal neurodegeneration correlates with histologic activation of microglia, but not with increased astrogliosis. Adults and adolescents have similar locomotion deficits after TBI that recover by 16 days postinjury. Adolescents have memory deficits as evidenced by impaired novel object recognition between 3-4 and 4-16 days postinjury (F_1,26  = 5.23, p = 0.031) while adults do not. In conclusion, adults and adolescents within a close age range (6-9 weeks) respond to TBI differently. Adolescents are more severely affected by mortality, neurodegeneration, and inflammation in the hippocampus compared to adults. Adolescents, but not adults, have worse memory performance after TBI that lasts at least 16 days postinjury.

Experimental Designs for Repeated Mild Traumatic Brain Injury: Challenges and Considerations

Mild traumatic brain injury (mild TBI) is a growing public concern, as evidence mounts that even brain injuries classified as "mild" can result in persistent neurological dysfunction. Multiple brain injuries heighten the likelihood of worsened or more prolonged symptomatology and may trigger long-term neurodegeneration. Animal models provide a logical platform to identify key parameters, such as loading forces, duration between injuries, and number of injuries, which contribute to additive or synergistic damage after repeated mild TBI. Despite the tremendous increase in research productivity in the field of repeated mild TBI, relatively few studies have been designed in such a way as to provide experimental-based insights into the dependence of cellular and functional outcomes on the prescribed parameters of mild TBI. In this review, we summarize how standard models of TBI have been adapted to produce mild TBI and highlight commonly observed aspects of neuropathology replicated in rodent models of mild TBI. The complexity of designing studies of repeated TBI is discussed, including challenges of incorporating appropriate control groups, informative experimental design, and relevant outcome measures. We then feature studies that provide a well-controlled, within-study design varying either the number of injuries or the interinjury interval. Harnessing the power of experimental models of TBI to elucidate which injury parameters are critical contributors to acute and chronic damage after repeated injury can further efforts at prevention and provide improved models for testing mechanisms and therapeutic interventions.

Psychometric Evaluation of Anxiety, Depression, and Sleep Quality after a Mild Traumatic Brain Injury: A Longitudinal Study

Introduction. Over 1 million mild traumatic brain injury (mTBI) cases are reported annually worldwide and may result in cognitive, physical, and emotional deterioration; depression; anxiety; and sleep problems. However, studies on long-term mTBI effects are limited. This study included 440 patients, and regular follow-ups of psychological assessments were performed for 2 years. Four questionnaires, including the Pittsburgh sleep quality index (PSQI), Epworth sleepiness scale (ESS), Beck's anxiety inventory (BAI), and Beck's depression inventory (BDI), were used to evaluate sleep problems, daytime sleepiness, anxiety, and depression, respectively. Results show that BAI and BDI scores considerably improved at the 6th-week, 1st-year, and 2nd-year follow-ups compared to baseline, yet these remained significantly different. In addition, anxiety and depression were prominent symptoms in a select subgroup of patients with poor initial evaluations, which improved over the 2 years. However, the ESS and PSQI scores fluctuated only mildly over the same time span. In conclusion, the mTBI patients showed a gradual improvement of anxiety and depression over the 2 years following injury. While anxiety and depression levels for mTBI patients in general did not return to premorbid status, improvements were observed. Sleep disorders persisted and were consistent with initial levels of distress.

Pharmacokinetics and efficacy of PT302, a sustained-release Exenatide formulation, in a murine model of mild traumatic brain injury

Traumatic brain injury (TBI) is a neurodegenerative disorder for which no effective pharmacological treatment is available. Glucagon-like peptide 1 (GLP-1) analogues such as Exenatide have previously demonstrated neurotrophic and neuroprotective effects in cellular and animal models of TBI. However, chronic or repeated administration was needed for efficacy. In this study, the pharmacokinetics and efficacy of PT302, a clinically available sustained-release Exenatide formulation (SR-Exenatide) were evaluated in a concussive mild (m)TBI mouse model. A single subcutaneous (s.c.) injection of PT302 (0.6, 0.12, and 0.024 mg/kg) was administered and plasma Exenatide concentrations were time-dependently measured over 3 weeks. An initial rapid regulated release of Exenatide in plasma was followed by a secondary phase of sustained-release in a dose-dependent manner. Short- and longer-term (7 and 30 day) cognitive impairments (visual and spatial deficits) induced by weight drop mTBI were mitigated by a single post-injury treatment with Exenatide delivered by s.c. injection of PT302 in clinically translatable doses. Immunohistochemical evaluation of neuronal cell death and inflammatory markers, likewise, cross-validated the neurotrophic and neuroprotective effects of SR-Exenatide in this mouse mTBI model. Exenatide central nervous system concentrations were 1.5% to 2.0% of concomitant plasma levels under steady-state conditions. These data demonstrate a positive beneficial action of PT302 in mTBI. This convenient single, sustained-release dosing regimen also has application for other neurological disorders, such as Alzheimer's disease, Parkinson's disease, multiple system atrophy and multiple sclerosis where prior preclinical studies, likewise, have demonstrated positive Exenatide actions.

Mapping the Changes of Glutamate Using Glutamate Chemical Exchange Saturation Transfer (GluCEST) Technique in a Traumatic Brain Injury Model: A Longitudinal Pilot Study

Glutamate excitoxicity plays a crucial role in the pathophysiology of traumatic brain injury (TBI) through the initiation of secondary injuries. Glutamate chemical exchange saturation transfer (GluCEST) MRI is a newly developed technique to noninvasively image glutamate in vivo with high sensitivity and spatial resolution. The aim of the present study was to use a rat model of TBI to map changes in brain glutamate distribution and explore the capability of GluCEST imaging for detecting secondary injuries. Sequential GluCEST imaging scans were performed in adult male Sprague-Dawley rats before TBI and at 1, 3, 7, and 14 days after TBI. GluCEST% increased and peaked on day 1 after TBI in the core lesion of injured cortex and peaked on day 3 in the ipsilateral hippocampus, as compared to baseline and controls. GluCEST% gradually declined to baseline by day 14 after TBI. A negative correlation between the GluCEST% of the ipsilateral hippocampus on day 3 and the time in the correct quadrant was observed in injured rats. Immunolabeling for glial fibrillary acidic protein showed significant astrocyte activation in the ipsilateral hippocampus of TBI rats. IL-6 and TNF-α in the core lesion peaked on day 1 postinjury, while those in the ipsilateral hippocampus peaked on day 3. These subsequently gradually declined to sham levels by day 14. It was concluded that GluCEST imaging has potential to be a novel neuroimaging approach for predicting cognitive outcome and to better understand neuroinflammation following TBI.

Neuronal Enriched Extracellular Vesicle Proteins as Biomarkers for Traumatic Brain Injury

Traumatic brain injury (TBI) is a major cause of injury-related death throughout the world and lacks effective treatment. Surviving TBI patients often develop neuropsychiatric symptoms, and the molecular mechanisms underlying the neuronal damage and recovery following TBI are not well understood. Extracellular vesicles (EVs) are membranous nanoparticles that are divided into exosomes (originating in the endosomal/multi-vesicular body [MVB] system) and microvesicles (larger EVs produced through budding of the plasma membrane). Both types of EVs are generated by all cells and are secreted into the extracellular environment, and participate in cell-to-cell communication and protein and RNA delivery. EVs enriched for neuronal origin can be harvested from peripheral blood samples and their contents quantitatively examined as a window to follow potential changes occurring in brain. Recent studies suggest that the levels of exosomal proteins and microRNAs (miRNAs) may represent novel biomarkers to support the clinical diagnosis and potential response to treatment for neurological disorders. In this review, we focus on the biogenesis of EVs, their molecular composition, and recent advances in research of their contents as potential diagnostic tools for TBI.

A Description and Evaluation of the Concussion Education Application HEADS UP Rocket Blades

BACKGROUND

Concussions are responsible for numerous emergency department visits and hospitalizations among children annually. However, there remains a great deal of confusion about how to prevent and manage concussions in youth. To teach children aged 6 to 8 years about concussion safety, the Centers for Disease Control and Prevention (CDC) created a mobile gaming application called HEADS UP Rocket Blades. This report introduces the game and presents findings on its evaluation.

METHODS

The aim of the game is to teach children what a concussion is, its commons signs and symptoms, how to prevent one, and what to do if one occurs. An early version of the game went through two rounds of usability testing with children and parents to obtain initial impressions and make improvements.

RESULTS

The first round of usability testing focused on the mechanics of the game. Based on feedback from this session, CDC and the developers simplified the messaging and adjusted the game's level of difficulty. The second round focused on the gaming experience. The children indicated that they enjoyed playing, and nearly all were able to relay at least one learning objective.

CONCLUSIONS

Parents and children rated Rocket Blades as a good learning tool and indicated that they would download it for personal use.

Repeated mild blast exposure in young adult rats results in dynamic and persistent microstructural changes in the brain

A history of mild traumatic brain injury (mTBI), particularly repeated mTBI (rmTBI), has been identified as a risk factor for late-onset neurodegenerative conditions. The mild and transient nature of early symptoms often impedes diagnosis in young adults who are disproportionately affected by mTBIs. A proportion of the affected population will incur long-term behavioral and cognitive consequences but the underlying pathomechanism is currently unknown. Diffusion tensor imaging (DTI) provides sensitive and quantitative assessment of TBI-induced structural changes, including white matter injury, and may be used to predict long-term outcome. We used DTI in an animal model of blast rmTBI (rmbTBI) to quantify blast-induced structural changes at 7 and 90 days post-injury, and their evolution between the two time points. Young adult male rats (~P65 at injury) were exposed to repeated mild blast overpressure, or anesthetized as shams, and their fixed brains were imaged using high-field (7 T) MRI. We found that whole brain volumes similarly increased in injured and sham rats from 7 to 90 days. However, we detected localized volume increases in blast-exposed animals 7 days post-injury, mainly ipsilateral to incident blast waves. Affected regions included gray matter of the frontal association, cingulate, and motor cortex, thalamus, substantia nigra, and raphe nuclei (median and dorsal), as well as white matter of the internal capsule and cerebral peduncle. Conversely, we measured volume reductions in these and other regions, including the hippocampus and cerebellum, at 90 days post-injury. DTI also detected both transient and persistent microstructural changes following injury, with some changes showing distinct ipsilateral versus contralateral side differences relative to blast impact. Early changes in fractional anisotropy (FA) were subtle, becoming more prominent at 90 days in the cerebral and inferior cerebellar peduncles, and cerebellar white matter. Widespread increases in radial diffusivity (RD) and axial diffusivity (primary eigenvalue or E1) at 7 days post-injury largely subsided by 90 days, although RD was more sensitive than E1 at detecting white matter changes. E1 effects in gray and white matter, which paralleled increases in apparent diffusion, were likely more indicative of dysregulated water homeostasis than pathologic structural changes. Importantly, we found evidence for a different developmental trajectory following rmbTBI, as indicated by significant injury x age interactions on volume. Our findings demonstrate that rmbTBI initiates dynamic pathobiological processes that may negatively alter the course of late-stage neurodevelopment and adversely affect long-term cognitive and behavioral outcomes.

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Young adult rats exposed to mild blast show lasting microstructural brain changes.

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The evolution of mTBI pathology was reflected by temporal changes in DTI measures.

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Regional volume changes captured significant injury × age interactions.

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DTI measures differentially captured injury effects in white and gray matter.

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Significant interaction effects suggest an altered developmental trajectory.

Metabolic and Structural Imaging at 7 Tesla After Repetitive Mild Traumatic Brain Injury in Immature Rats

Mild traumatic brain injury (mTBI) in children is a common and serious public health problem. Traditional neuroimaging findings in children who sustain mTBI are often normal, putting them at risk for repeated mTBI (rmTBI). There is a need for more sensitive imaging techniques capable of detecting subtle neurophysiological alterations after injury. We examined neurochemical and white matter changes using diffusion tensor imaging of the whole brain and proton magnetic resonance spectroscopy of the hippocampi at 7 Tesla in 18-day-old male rats at 7 days after mTBI and rmTBI. Traumatic axonal injury was assessed by beta-amyloid precursor protein accumulation using immunohistochemistry. A significant decrease in fractional anisotropy and increase in axial and radial diffusivity were observed in several brain regions, especially in white matter regions, after a single mTBI versus sham and more prominently after rmTBI. In addition, we observed accumulation of beta-amyloid precursor protein in the external capsule after mTBI and rmTBI. mTBI and rmTBI reduced the N-acetylaspartate/creatine ratio (NAA/Cr) and increased the myoinositol/creatine ratio (Ins/Cr) versus sham. rmTBI exacerbated the reduction in NAA/Cr versus mTBI. The choline/creatine (Cho/Cr) and (lipid/Macro Molecule 1)/creatine (Lip/Cr) ratios were also decreased after rmTBI versus sham. Diffusion tensor imaging findings along with the decrease in Cho and Lip after rmTBI may reflect damage to axonal membrane. NAA and Ins are altered at 7 days after mTBI and rmTBI likely reflecting neuro-axonal damage and glial response, respectively. These findings may be relevant to understanding the extent of disability following mTBI and rmTBI in the immature brain and may identify possible therapeutic targets.

Large animal models of traumatic brain injury

Purpose/Aim: Animal models of traumatic brain injury (TBI) provide powerful tools to study TBI in a controlled, rigorous and cost-efficient manner. The mostly used animals in TBI studies so far are rodents. However, compared with rodents, large animals (e.g. swine, rabbit, sheep, ferret, etc.) show great advantages in modeling TBI due to the similarity of their brains to human brain. The aim of our review was to summarize the development and progress of common large animal TBI models in past 30 years.

MATERIALS AND METHODS

Mixed published articles and books associated with large animal models of TBI were researched and summarized.

RESULTS

We majorly sumed up current common large animal models of TBI, including discussion on the available research methodologies in previous studies, several potential therapies in large animal trials of TBI as well as advantages and disadvantages of these models.

CONCLUSIONS

Large animal models of TBI play crucial role in determining the underlying mechanisms and screening putative therapeutic targets of TBI.

Repositioning drugs for traumatic brain injury - N-acetyl cysteine and Phenserine

Traumatic brain injury (TBI) is one of the most common causes of morbidity and mortality of both young adults of less than 45 years of age and the elderly, and contributes to about 30% of all injury deaths in the United States of America. Whereas there has been a significant improvement in our understanding of the mechanism that underpin the primary and secondary stages of damage associated with a TBI incident, to date however, this knowledge has not translated into the development of effective new pharmacological TBI treatment strategies. Prior experimental and clinical studies of drugs working via a single mechanism only may have failed to address the full range of pathologies that lead to the neuronal loss and cognitive impairment evident in TBI and other disorders. The present review focuses on two drugs with the potential to benefit multiple pathways considered important in TBI. Notably, both agents have already been developed into human studies for other conditions, and thus have the potential to be rapidly repositioned as TBI therapies. The first is N-acetyl cysteine (NAC) that is currently used in over the counter medications for its anti-inflammatory properties. The second is (-)-phenserine ((-)-Phen) that was originally developed as an experimental Alzheimer's disease (AD) drug. We briefly review background information about TBI and subsequently review literature suggesting that NAC and (-)-Phen may be useful therapeutic approaches for TBI, for which there are no currently approved drugs.

Talking with young children about concussions: an exploratory study

BACKGROUND

Concussion education for children early in their participation in organized sport may help shape lasting attitudes about concussion safety. However, existing programming and research focus on older ages.

METHODS

Qualitative interviews about concussions were conducted with twenty children between the ages of six and eight. Structural, descriptive and pattern coding were used to organize the transcribed interviews and identify emergent themes.

RESULTS

Eighteen of the participants indicated that they had heard of the word concussion, with 12 describing the injury as related to the brain or head. The most frequently described mechanisms of injury were impacts to the head or falls, and symptoms tended to be somatic, such as generalized pain. The most frequently endorsed strategy to avoid sustaining a concussion was to 'follow the rules.' Multiple participants referenced parents as an informal source of information about concussions.

CONCLUSIONS

While most participants demonstrated some awareness about concussions, there were clear knowledge gaps that can be addressed with developmentally appropriate concussion education programming. Consistent with their developmental stage, interventions targeted at children in this age range may be most successful if they use basic logic, concrete ideas, provide rules to be followed and engage parents in dissemination.

Impaired Cognitive Performance in Youth Athletes Exposed to Repetitive Head Impacts

Worldwide, more than 22 million children and adolescents are exposed to repetitive head impacts (RHI) in soccer. Evidence indicates cumulative effects on brain structure, but it is not known whether exposure to RHI affects cognitive improvement in adolescents. The aim of the study was to determine whether exposure to RHI while heading the ball in soccer affects improvement in cognitive performance in adolescents over time. The study group consisted of a convenience sample of 16 male soccer players (mean age 15.7 ± 0.7 years). A comparison cohort of 14 male non-contact sports athletes (mean age 14.9 ± 1.1 years) was recruited from competitive athletic clubs and group-matched in age. Using the ProPoint and AntiPoint tasks, sensorimotor and cognitive functions were measured over both immediate (pre- vs. post-training) as well as across multiple time points within a play season. The number and type of head impacts that occurred during the training were counted. The main outcome measure was the change in response time (RT) in the ProPoint and AntiPoint tasks. The immediate (pre- vs. post-training) and longer-term (across a play season) change in RT was analyzed, and the effect of the number and type of head impacts was tested. Thirty athletes with and without exposure to RHI demonstrated a decrease in RT in both tasks immediately after training. Over the play season, both groups showed improvement in sensorimotor function. While the control group also improved in cognitive performance, the soccer players did not, however. Further, the more long headers performed, the slower the improvement in RT over the season. Youth athletes experience an immediate cognitive improvement after training most likely because of physical exercise. Results of this study also suggest an association between exposure to specific RHI (long headers) and lack of improvement in cognitive performance in youth athletes over time.

Community-Level Inequalities in Concussion Education of Youth Football Coaches

INTRODUCTION

USA Football has made the Heads Up Football (HUF) concussion education program available for coaches of youth football players. Existing evidence about the effectiveness of the HUF coach education program is equivocal. For HUF and other programs, there is growing concern that even effective interventions can increase inequalities if there is different uptake or impact by SES or other demographic factors. Understanding how adoption is patterned along these lines is important for understanding equity issues in youth football. This study tested the hypothesis that there will be lower adoption of HUF among coaches of youth football players in lower-SES communities.

METHODS

The authors conducted a cross-sectional study of the association between community-level characteristics and number of USA Football youth league coaches who have completed HUF. Data were collected in 2014 and analyzed in 2015-2016.

RESULTS

Implementation of the HUF program was patterned by community-level socioeconomic characteristics. Leagues located in communities with a higher percentage of families with children aged <18 years living below the poverty line and a smaller percentage of non-Hispanic white residents tended to have leagues with smaller percentages of HUF-certified coaches.

CONCLUSIONS

As interventions are developed that reduce the risks of youth football, it is important to consider not just the effectiveness of these interventions, but also whether they reduce or exacerbate health inequities. These results suggest that relying on voluntary adoption of coach education may result in inequitable implementation. Further study is required to identify and remedy organizational and contextual barriers to implementation of coach education in youth sport.

Unintentional injuries after TBI: Potential risk factors, impacts, and prevention

BACKGROUND

The top three causes of fatal unintentional injuries are falls, motor vehicle crashes, and being struck against or struck by objects or persons. These etiologies also happen to be the leading causes of TBI, a serious public health problem, in the US. Reduced cognitive functioning, poor decision making, increased risk taking, disinhibition, diminished safety skills and substance use, place individuals with TBI at an increased risk for subsequent unintentional injuries. The caregiving, psychological, social and financial burden of initial injuries is enormous. Unintentional injuries post-TBI add to that burden significantly. Many unintentional injuries can be prevented with simple education and environment and lifestyle changes. Injury prevention requires collaboration among many.

OBJECTIVE

This literature review will share information regarding potential triggers or causes of unintentional injuries after TBI to identify potential issues. The many impacts of these injuries will be reviewed. Best practices in prevention will be presented.

CONCLUSION

Ultimately, education, discussion, and awareness across multiple stakeholders can aid in preventing unintentional injuries after TBI.

Neuroinflammation in animal models of traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of mortality and morbidity worldwide. Neuroinflammation is prominent in the short and long-term consequences of neuronal injuries that occur after TBI. Neuroinflammation involves the activation of glia, including microglia and astrocytes, to release inflammatory mediators within the brain, and the subsequent recruitment of peripheral immune cells. Various animal models of TBI have been developed that have proved valuable to elucidate the pathophysiology of the disorder and to assess the safety and efficacy of novel therapies prior to clinical trials. These models provide an excellent platform to delineate key injury mechanisms that associate with types of injury (concussion, contusion, and penetration injuries) that occur clinically for the investigation of mild, moderate, and severe forms of TBI. Additionally, TBI modeling in genetically engineered mice, in particular, has aided the identification of key molecules and pathways for putative injury mechanisms, as targets for development of novel therapies for human TBI. This Review details the evidence showing that neuroinflammation, characterized by the activation of microglia and astrocytes and elevated production of inflammatory mediators, is a critical process occurring in various TBI animal models, provides a broad overview of commonly used animal models of TBI, and overviews representative techniques to quantify markers of the brain inflammatory process. A better understanding of neuroinflammation could open therapeutic avenues for abrogation of secondary cell death and behavioral symptoms that may mediate the progression of TBI.

Pomalidomide mitigates neuronal loss, neuroinflammation, and behavioral impairments induced by traumatic brain injury in rat

BACKGROUND

Traumatic brain injury (TBI) is a global health concern that typically causes emotional disturbances and cognitive dysfunction. Secondary pathologies following TBI may be associated with chronic neurodegenerative disorders and an enhanced likelihood of developing dementia-like disease in later life. There are currently no approved drugs for mitigating the acute or chronic effects of TBI.

METHODS

The effects of the drug pomalidomide (Pom), an FDA-approved immunomodulatory agent, were evaluated in a rat model of moderate to severe TBI induced by controlled cortical impact. Post-TBI intravenous administration of Pom (0.5 mg/kg at 5 or 7 h and 0.1 mg/kg at 5 h) was evaluated on functional and histological measures that included motor function, fine more coordination, somatosensory function, lesion volume, cortical neurodegeneration, neuronal apoptosis, and the induction of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6).

RESULTS

Pom 0.5 mg/kg administration at 5 h, but not at 7 h post-TBI, significantly mitigated the TBI-induced injury volume and functional impairments, neurodegeneration, neuronal apoptosis, and cytokine mRNA and protein induction. To evaluate underlying mechanisms, the actions of Pom on neuronal survival, microglial activation, and the induction of TNF-α were assessed in mixed cortical cultures following a glutamate challenge. Pom dose-dependently ameliorated glutamate-mediated cytotoxic effects on cell viability and reduced microglial cell activation, significantly attenuating the induction of TNF-α.

CONCLUSIONS

Post-injury treatment with a single Pom dose within 5 h significantly reduced functional impairments in a well-characterized animal model of TBI. Pom decreased the injury lesion volume, augmented neuronal survival, and provided anti-inflammatory properties. These findings strongly support the further evaluation and optimization of Pom for potential use in clinical TBI.

Repetitive Traumatic Brain Injury in Patients From Kashan, Iran

Background

Traumatic brain injury (TBI) is a worldwide problem, especially in countries with high incidence of road traffic accidents such as Iran. Patients with a single occurrence of TBI have been shown to be at increased risk to sustain future TBI.

Objectives

The aim of this study was to present the incidence and characteristics of repeated TBI (RTBI) in Iranian patients.

Patients and Methods

During one year, all admitted TBI patients with prior TBI history were enrolled into the study. In each patient, data such as age, gender, past medical history, injury cause, anatomic site of injury, TBI severity, clinical findings and CT scan findings were collected.

Results

RTBI comprised 2.5% of TBI cases (41 of 1629). The incidence of RTBI per 100,000 individuals per years was 9.7. The main cause of RTBI was road traffic accident (68.3%); 9.7 % of cases had preexisting seizure/epilepsy disorder; 36.6% of patients with RTBI had pervious ICU admission due to severe TBI. Ten patients had Glasgow coma scale (GCS) ≤ 13 (24.4%). Seizure was seen in seven patients (17.1%). Thirty-nine percent of patients with RTBI had associated injuries. Eleven patients had abnormal CT scan findings (26.9%).

Conclusions

Considering the high incidence of trauma in developing countries, RTBI may also be more common compared with that of developed countries. This mandates a newer approach to preventive strategies, particularly in those with a previous experience of head injury.

Objectifying eye movements during rapid number naming: Methodology for assessment of normative data for the King-Devick test

OBJECTIVE

Concussion is a major public health problem and considerable efforts are focused on sideline-based diagnostic testing to guide return-to-play decision-making and clinical care. The King-Devick (K-D) test, a sensitive sideline performance measure for concussion detection, reveals slowed reading times in acutely concussed subjects, as compared to healthy controls; however, the normal behavior of eye movements during the task and deficits underlying the slowing have not been defined.

METHODS

Twelve healthy control subjects underwent quantitative eye tracking during digitized K-D testing.

RESULTS

The total K-D reading time was 51.24 (±9.7) seconds. A total of 145 saccades (±15) per subject were generated, with average peak velocity 299.5°/s and average amplitude 8.2°. The average inter-saccadic interval was 248.4 ms. Task-specific horizontal and oblique saccades per subject numbered, respectively, 102 (±10) and 17 (±4). Subjects with the fewest saccades tended to blink more, resulting in a larger amount of missing data; whereas, subjects with the most saccades tended to make extra saccades during line transitions.

CONCLUSIONS

Establishment of normal and objective ocular motor behavior during the K-D test is a critical first step towards defining the range of deficits underlying abnormal testing in concussion. Further, it sets the groundwork for exploration of K-D correlations with cognitive dysfunction and saccadic paradigms that may reflect specific neuroanatomic deficits in the concussed brain.

Repetitive Mild Traumatic Brain Injury in the Developing Brain: Effects on Long-Term Functional Outcome and Neuropathology

Although accumulating evidence suggests that repetitive mild TBI (rmTBI) may cause long-term cognitive dysfunction in adults, whether rmTBI causes similar deficits in the immature brain is unknown. Here we used an experimental model of rmTBI in the immature brain to answer this question. Post-natal day (PND) 18 rats were subjected to either one, two, or three mild TBIs (mTBI) or an equivalent number of sham insults 24 h apart. After one or two mTBIs or sham insults, histology was evaluated at 7 days. After three mTBIs or sham insults, motor (d1-5), cognitive (d11-92), and histological (d21-92) outcome was evaluated. At 7 days, silver degeneration staining revealed axonal argyrophilia in the external capsule and corpus callosum after a single mTBI, with a second impact increasing axonal injury. Iba-1 immunohistochemistry showed amoeboid shaped microglia within the amygdalae bilaterally after mTBI. After three mTBI, there were no differences in beam balance, Morris water maze, and elevated plus maze performance versus sham. The rmTBI rats, however, showed impairment in novel object recognition and fear conditioning. Axonal silver staining was observed only in the external capsule on d21. Iba-1 staining did not reveal activated microglia on d21 or d92. In conclusion, mTBI results in traumatic axonal injury and microglial activation in the immature brain with repeated impact exacerbating axonal injury. The rmTBI in the immature brain leads to long-term associative learning deficit in adulthood. Defining the mechanisms damage from rmTBI in the developing brain could be vital for identification of therapies for children.

The association between traumatic brain injury and suicide: are kids at risk?

Traumatic brain injury (TBI) in late adolescence and adulthood is associated with a higher risk of suicide; however, it is unknown whether this association is also present in people who sustained a TBI during childhood. The purpose of the present study was to determine whether experiencing a TBI during childhood is a risk factor for suicide later in life and to examine whether the risk of suicide differs by sex or injury severity. A cohort of 135,703 children aged 0-17 years was identified from the Quebec population-based physician reimbursement database in 1987, and follow-up was conducted until 2008. Of the children in this cohort, 21,047 had sustained a TBI. Using a survival analysis with time-dependent indicators of TBI, we found a higher risk of suicide for people who sustained a TBI during childhood (hazard ratio (HR) = 1.49, 95% confidence interval (CI): 1.04, 2.14), adolescence (HR = 1.57, 95% CI: 1.09, 2.26), and adulthood (HR = 2.53, 95% CI: 1.79, 3.59). When compared with less severe injuries, such as concussions and cranial fractures, more severe injuries, such as intracranial hemorrhages, were associated with a higher risk of suicide (HR = 2.18 vs. 2.77, respectively). Repeated injuries were associated with higher risks of suicide in all age groups.

Liraglutide is neurotrophic and neuroprotective in neuronal cultures and mitigates mild traumatic brain injury in mice

Traumatic brain injury (TBI), a brain dysfunction for which there is no present effective treatment, is often caused by a concussive impact to the head and affects an estimated 1.7 million Americans annually. Our laboratory previously demonstrated that exendin-4, a long-lasting glucagon-like peptide 1 receptor (GLP-1R) agonist, has neuroprotective effects in cellular and animal models of TBI. Here, we demonstrate neurotrophic and neuroprotective effects of a different GLP-1R agonist, liraglutide, in neuronal cultures and a mouse model of mild TBI (mTBI). Liraglutide promoted dose-dependent proliferation in SH-SY5Y cells and in a GLP-1R over-expressing cell line at reduced concentrations. Pre-treatment with liraglutide rescued neuronal cells from oxidative stress- and glutamate excitotoxicity-induced cell death. Liraglutide produced neurotrophic and neuroprotective effects similar to those of exendin-4 in vitro. The cAMP/PKA/pCREB pathway appears to play an important role in this neuroprotective activity of liraglutide. Furthermore, our findings in cell culture were well-translated in a weight drop mTBI mouse model. Post-treatment with a clinically relevant dose of liraglutide for 7 days in mice ameliorated memory impairments caused by mTBI when evaluated 7 and 30 days post trauma. These data cross-validate former studies of exendin-4 and suggest that liraglutide holds therapeutic potential for the treatment of mTBI. Exendin-4, a long-lasting glucagon-like peptide 1 receptor (GLP-1R) agonist, has neuroprotective effects in cellular and animal models of traumatic brain injury (TBI). Here, we demonstrate neurotrophic and neuroprotective effects of a different GLP-1R agonist, liraglutide, in neuronal cultures and a mouse model of mild TBI (mTBI). Liraglutide promoted dose-dependent proliferation in SH-SY5Y cells and in a GLP-1R over-expressing cell line at reduced concentrations. Pretreatment with liraglutide rescued neuronal cells from oxidative stress- and glutamate excitotoxicity-induced cell death. Liraglutide produced neurotrophic and neuroprotective effects similar to those of exendin-4 in vitro, likely involving the cAMP/PKA/pCREB pathway. Our findings in cell culture were well-translated in a weight-drop mTBI mouse model. Post-treatment with a clinically relevant dose of liraglutide for 7 days in mice ameliorated memory impairments caused by mTBI.

The persistent influence of pediatric concussion on attention and cognitive control during flanker performance

This study investigated the influence of concussion history on children's neurocognitive processing. Thirty-two children ages 8-10 years (16 with a concussion history, 16 controls) completed compatible and incompatible conditions of a flanker task while behavioral and neuroelectric data were collected. Relative to controls, children with a concussion history exhibited alterations in the sequential congruency effect, committed more omission errors, and exhibited decreased post-error accuracy. Children with a concussion history exhibited longer N2 latency across task conditions, increased N2 amplitude during the incompatible condition of the task, and decreased P3b amplitude across task conditions. Children with a history of concussion also exhibited decreased ERN and Pe amplitudes, with group difference increasing for the incompatible condition of the task. The current results indicate that pediatric concussion may lead to subtle, but pervasive deficits in attention and cognitive control. These results serve to inform a poorly understood but significant public health concern.

Expert consensus document: Mind the gaps—advancing research into short-term and long-term neuropsychological outcomes of youth sports-related concussions

Sports-related concussions and repetitive subconcussive exposure are increasingly recognized as potential dangers to paediatric populations, but much remains unknown about the short-term and long-term consequences of these events, including potential cognitive impairment and risk of later-life dementia. This Expert Consensus Document is the result of a 1-day meeting convened by Safe Kids Worldwide, the Alzheimer's Drug Discovery Foundation, and the Andrews Institute for Orthopaedics and Sports Medicine. The goal is to highlight knowledge gaps and areas of critically needed research in the areas of concussion science, dementia, genetics, diagnostic and prognostic biomarkers, neuroimaging, sports injury surveillance, and information sharing. For each of these areas, we propose clear and achievable paths to improve the understanding, treatment and prevention of youth sports-related concussions.

Cerebrolysin Asian Pacific trial in acute brain injury and neurorecovery: design and methods

Traumatic brain injury (TBI) is one of the leading causes of injury-related death. In the United States alone, an estimated 1.7 million people sustain a TBI each year, and approximately 5.3 million people live with a TBI-related disability. The direct medical costs and indirect costs such as lost productivity of TBIs totaled an estimated $76.5 billion in the U.S. in the year 2000. Improving the limited treatment options for this condition remains challenging. However, recent reports from interdisciplinary working groups (consisting primarily of neurologists, neurosurgeons, neuropsychologists, and biostatisticians) have stated that to improve TBI treatment, important methodological lessons from the past must be taken into account in future clinical research. An evaluation of the neuroprotection intervention studies conducted over the last 30 years has indicated that a limited understanding of the underlying biological concepts and methodological design flaws are the major reasons for the failure of pharmacological agents to demonstrate efficacy. Cerebrolysin is a parenterally-administered neuro-peptide preparation that acts in a manner similar to endogenous neurotrophic factors. Cerebrolysin has a favorable adverse effect profile, and several meta-analyses have suggested that Cerebrolysin is beneficial as a dementia treatment. CAPTAIN is a randomized, double-blind, placebo-controlled, multi-center, multinational trial of the effects of Cerebrolysin on neuroprotection and neurorecovery after TBI using a multidimensional ensemble of outcome scales. The CAPTAIN trial will be the first TBI trial with a 'true' multidimensional approach based on full outcome scales, while avoiding prior weaknesses, such as loss of information through "dichotomization," or unrealistic assumptions such as "normal distribution."

An introduction to sports concussions

PURPOSE OF REVIEW

Concussions are a major public health issue, and particularly so in the setting of sports. Millions of athletes of all ages may face the risks of concussion and repeat concussion. This article introduces the terminology, epidemiology, and underlying pathophysiology associated with concussion, focused on sports-related injuries.

RECENT FINDINGS

Concussion is a clinical syndrome of symptoms and signs occurring after biomechanical force is imparted to the brain. Because of the subjective nature of symptom reporting, definitions of concussion differ slightly in different guidelines. Concussion nomenclature also includes mild traumatic brain injury, postconcussion symptoms, postconcussion syndrome, chronic neurocognitive impairment, subconcussive injury, and chronic traumatic encephalopathy. Between 1.6 and 3.8 million sports-related concussions are estimated in the United States annually, particularly in youth athletes. Rates of concussion are higher in sports such as football, rugby, ice hockey, and wrestling in males, and soccer and basketball in females. The underlying pathophysiology of concussion centers on membrane leakage, ionic flux, indiscriminate glutamate release, and energy crisis. These initial events then trigger ongoing metabolic impairment, vulnerability to second injury, altered neural activation, and axonal dysfunction. While the linkage between acute neurobiology and chronic deficits remains to be elucidated, activation of cell death pathways, ongoing inflammation, persistent metabolic problems, and accumulation of abnormal or toxic proteins have all been implicated.

SUMMARY

Concussion is a biomechanically induced syndrome of neural dysfunction. Millions of concussions occur annually, many of them related to sports. Biologically, a complex sequence of events occurs from initial ionic flux, glutamate release, and axonal damage, resulting in vulnerability to second injury and possibly to longer-term neurodegeneration.

Trends and outcome predictors after traumatic brain injury surgery: a nationwide population-based study in Taiwan

OBJECT

The authors sought to analyze trends in hospital resource utilization and mortality rates in a population of patients who had received traumatic brain injury (TBI) surgery.

METHODS

This nationwide population-based cohort study retrospectively analyzed 18,286 patients who had received surgical treatment for TBI between 1998 and 2010. The multiple linear regression model and Cox proportional hazards model were used for multivariate assessment of outcome predictors.

RESULTS

The prevalence rate of surgical treatment for patients with TBI gradually but significantly (p < 0.001) increased by 47.6% from 5.0 per 100,000 persons in 1998 to 7.4 per 100,000 persons in 2010. Age, sex, Deyo-Charlson comorbidity index score, hospital volume, and surgeon volume were significantly associated with TBI surgery outcomes (p < 0.05). Over the 12-year period analyzed, the estimated mean hospital treatment cost increased 19.06%, whereas the in-hospital mortality rate decreased 10.9%. The estimated mean time of overall survival after TBI surgery (± SD) was 83.0 ± 4.2 months, and the overall in-hospital and 1-, 3-, and 5-year survival rates were 74.5%, 67.3%, 61.1%, and 57.8%, respectively.

CONCLUSIONS

These data reveal an increased prevalence of TBI, especially in older patients, and an increased hospital treatment cost but a decreased in-hospital mortality rate. Health care providers and patients should recognize that attributes of the patient and of the hospital may affect hospital resource utilization and the mortality rate. These results are relevant not only to other countries with similar population sizes but also to countries with larger populations.

A normative study of the sport concussion assessment tool (SCAT2) in children and adolescents

Recent clinical practice parameters encourage systematic use of concussion surveillance/management tools that evaluate participating athletes at baseline and after concussion. Office-based tools (Sports Concussion Assessment Tool; SCAT2) require accurate baseline assessment to maximize utility but no normative data exist for children on the SCAT2, limiting identification of "normal" or "impaired" score ranges. The purpose of this study was to develop child and adolescent baseline norms for the SCAT2 to provide reference values for different age groups. A community-based approach was implemented to compile baseline performance data on the SCAT2 in 761 children aged 9 to 18 to create age- and sex-graded norms. Findings indicate a significant age effect on SCAT2 performance such that older adolescents and teenagers produced higher (better) total scores than younger children (ages 9 to 11) driven by age differences on individual components measuring cognition (SAC), postural stability (BESS), and symptom report. Females endorsed greater numbers of symptoms at baseline than males. Normative data tables are presented. Findings support the SCAT2 as a useful clinical tool for assessing baseline functioning in teenagers, but suggest clinical utility may be limited in children under age 11. Follow-up studies after incident concussion are needed to confirm this assumption.

Adolescent TBI-induced hypopituitarism causes sexual dysfunction in adult male rats

Adolescents are at greatest risk for traumatic brain injury (TBI) and repeat TBI (RTBI). TBI-induced hypopituitarism has been documented in both adults and juveniles and despite the necessity of pituitary function for normal physical and brain development, it is still unrecognized and untreated in adolescents following TBI. TBI induced hormonal dysfunction during a critical developmental window has the potential to cause long-term cognitive and behavioral deficits and the topic currently remains unaddressed. The purpose of this study was to determine if four mild TBIs delivered to adolescent male rats disrupts testosterone production and adult behavioral outcomes. Plasma testosterone was quantified from 72 hrs preinjury to 3 months postinjury and pubertal onset, reproductive organ growth, erectile function and reproductive behaviors were assessed at 1 and 2 months postinjury. RTBI resulted in both acute and chronic decreases in testosterone production and delayed onset of puberty. Significant deficits were observed in reproductive organ growth, erectile function and reproductive behaviors in adult rats at both 1 and 2 months postinjury. These data suggest adolescent RTBI-induced hypopituitarism underlies abnormal behavioral changes observed during adulthood. The impact of undiagnosed hypopituitarism following RTBI in adolescence has significance not only for growth and puberty, but also for brain development and neurobehavioral function as adults.

ω-3 fatty acid supplementation as a potential therapeutic aid for the recovery from mild traumatic brain injury/concussion

Sports-related concussions or mild traumatic brain injuries (mTBIs) are becoming increasingly recognized as a major public health concern; however, no effective therapy for these injuries is currently available. ω-3 (n-3) fatty acids, such as docosahexaenoic acid (DHA), have important structural and functional roles in the brain, with established clinical benefits for supporting brain development and cognitive function throughout life. Consistent with these critical roles of DHA in the brain, accumulating evidence suggests that DHA may act as a promising recovery aid, or possibly as a prophylactic nutritional measure, for mTBI. Preclinical investigations demonstrate that dietary consumption of DHA provided either before or after mTBI improves functional outcomes, such as spatial learning and memory. Mechanistic investigations suggest that DHA influences multiple aspects of the pathologic molecular signaling cascade that occurs after mTBI. This review examines the evidence of interactions between DHA and concussion and discusses potential mechanisms by which DHA helps the brain to recover from injury. Additional clinical research in humans is needed to confirm the promising results reported in the preclinical literature.

Animal models of sports-related head injury: bridging the gap between pre-clinical research and clinical reality

Sports-related head impact and injury has become a very highly contentious public health and medico-legal issue. Near-daily news accounts describe the travails of concussed athletes as they struggle with depression, sleep disorders, mood swings, and cognitive problems. Some of these individuals have developed chronic traumatic encephalopathy, a progressive and debilitating neurodegenerative disorder. Animal models have always been an integral part of the study of traumatic brain injury in humans but, historically, they have concentrated on acute, severe brain injuries. This review will describe a small number of new and emerging animal models of sports-related head injury that have the potential to increase our understanding of how multiple mild head impacts, starting in adolescence, can have serious psychiatric, cognitive and histopathological outcomes much later in life. Sports-related head injury (SRHI) has emerged as a significant public health issue as athletes can develop psychiatric and neurodegenerative disorders later in life. Animal models have always been an integral part of the study of human TBI but few existing methods are valid for studying SRHI. In this review, we propose criteria for effective animal models of SRHI. Movement of the head upon impact is judged to be of primary importance in leading to concussion and persistent CNS dysfunction.

Preconditioning provides neuroprotection in models of CNS disease: paradigms and clinical significance

Preconditioning is a phenomenon in which brief episodes of a sublethal insult induce robust protection against subsequent lethal injuries. Preconditioning has been observed in multiple organisms and can occur in the brain as well as other tissues. Extensive animal studies suggest that the brain can be preconditioned to resist acute injuries, such as ischemic stroke, neonatal hypoxia/ischemia, surgical brain injury, trauma, and agents that are used in models of neurodegenerative diseases, such as Parkinson's disease and Alzheimer's disease. Effective preconditioning stimuli are numerous and diverse, ranging from transient ischemia, hypoxia, hyperbaric oxygen, hypothermia and hyperthermia, to exposure to neurotoxins and pharmacological agents. The phenomenon of "cross-tolerance," in which a sublethal stress protects against a different type of injury, suggests that different preconditioning stimuli may confer protection against a wide range of injuries. Research conducted over the past few decades indicates that brain preconditioning is complex, involving multiple effectors such as metabolic inhibition, activation of extra- and intracellular defense mechanisms, a shift in the neuronal excitatory/inhibitory balance, and reduction in inflammatory sequelae. An improved understanding of brain preconditioning should help us identify innovative therapeutic strategies that prevent or at least reduce neuronal damage in susceptible patients. In this review, we focus on the experimental evidence of preconditioning in the brain and systematically survey the models used to develop paradigms for neuroprotection, and then discuss the clinical potential of brain preconditioning.

The effects of repeat traumatic brain injury on the pituitary in adolescent rats

Adolescents are one of the highest groups at risk for sustaining both traumatic brain injury (TBI) and repeat TBI (RTBI). Consequences of endocrine dysfunction following TBI have been routinely explored in adults, but studies in adolescents are limited, and show an incidence rate of endocrine dysfunction in 16-61% in patients, 1-5 years after injury. Similar to in adults, the most commonly affected axis is growth hormone (GH) and insulin-like growth hormone 1 (IGF-1). Despite TBI being the primary cause of morbidity and mortality among the pediatric population, there are currently no experimental studies specifically addressing the occurrence of pituitary dysfunction in adolescents. The present study investigated whether a sham, single injury or four repeat injuries (24 h interval) delivered to adolescent rats resulted in disruption of the GH/IGF-1 axis. Circulating levels of basal GH and IGF-1 were measured at baseline, 24 h, 72 h, 1 week, and 1 month after injury, and vascular permeability of the pituitary gland was quantified via Evans Blue dye extravasation. Changes in weight and length of animals were measured as a potential consequence of GH and IGF-1 disruption. The results from the current study demonstrate that RTBI results in significant acute and chronic decreases in circulation of GH and IGF-1, reduction in weight gain and growth, and an increase in Evans Blue dye extravasation in the pituitary compared with sham and single injury animals. RTBI causes significant disruption of the GH/IGF-1 axis that may ultimately affect normal cognitive and physical development during adolescence.