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

Machine embroidery of light-emitting textiles with multicolor electroluminescent threads

Advances in electroluminescent threads, suitable for weaving or knitting, have opened doors for the development of light-emitting textiles, driving growth in the market for flexible and wearable displays. Although direct embroidery of these textiles with custom designs and patterns could offer substantial benefits, the rigorous demands of machine embroidery challenge the integrity of these threads. Here, we present embroiderable multicolor electroluminescent threads-in blue, green, and yellow-that are compatible with standard embroidery machines. These threads can be used to stitch decorative designs onto various consumer fabrics without compromising their wear resistance or light-emitting capabilities. Demonstrations include illuminating specific messages or designs on consumer products and delivering emergency alerts on helmet liners for physical hazards. Our research delivers a comprehensive toolkit for integrating light-emitting textiles into trendy, customized crafts tailored to the unique requirements of diverse flexible and wearable displays.

Whole-Blood Metabolomics of a Rat Model of Repetitive Concussion

Mild traumatic brain injury (mTBI) and repetitive mTBI (RmTBI) are silent epidemics, and so far, there is no objective diagnosis. The severity of the injury is solely based on the Glasgow Coma Score (GCS) scale. Most patients suffer from one or more behavioral abnormalities, such as headache, amnesia, cognitive decline, disturbed sleep pattern, anxiety, depression, and vision abnormalities. Additionally, most neuroimaging modalities are insensitive to capture structural and functional alterations in the brain, leading to inefficient patient management. Metabolomics is one of the established omics technologies to identify metabolic alterations, mostly in biofluids. NMR-based metabolomics provides quantitative metabolic information with non-destructive and minimal sample preparation. We employed whole-blood NMR analysis to identify metabolic markers using a high-field NMR spectrometer (800 MHz). Our approach involves chemical-free sample pretreatment and minimal sample preparation to obtain a robust whole-blood metabolic profile from a rat model of concussion. A single head injury was given to the mTBI group, and three head injuries to the RmTBI group. We found significant alterations in blood metabolites in both mTBI and RmTBI groups compared with the control, such as alanine, branched amino acid (BAA), adenosine diphosphate/adenosine try phosphate (ADP/ATP), creatine, glucose, pyruvate, and glycerphosphocholine (GPC). Choline was significantly altered only in the mTBI group and formate in the RmTBI group compared with the control. These metabolites corroborate previous findings in clinical and preclinical cohorts. Comprehensive whole-blood metabolomics can provide a robust metabolic marker for more accurate diagnosis and treatment intervention for a disease population.

Frontoamygdala hyperconnectivity predicts affective dysregulation in adolescent moderate-severe TBI

In survivors of moderate to severe traumatic brain injury (msTBI), affective disruptions often remain underdetected and undertreated, in part due to poor understanding of the underlying neural mechanisms. We hypothesized that limbic circuits are integral to affective dysregulation in msTBI. To test this, we studied 19 adolescents with msTBI 17 months post-injury (TBI: M age 15.6, 5 females) as well as 44 matched healthy controls (HC: M age 16.4, 21 females). We leveraged two previously identified, large-scale resting-state (rsfMRI) networks of the amygdala to determine whether connectivity strength correlated with affective problems in the adolescents with msTBI. We found that distinct amygdala networks differentially predicted externalizing and internalizing behavioral problems in patients with msTBI. Specifically, patients with the highest medial amygdala connectivity were rated by parents as having greater externalizing behavioral problems measured on the BRIEF and CBCL, but not cognitive problems. The most correlated voxels in that network localize to the rostral anterior cingulate (rACC) and posterior cingulate (PCC) cortices, predicting 48% of the variance in externalizing problems. Alternatively, patients with the highest ventrolateral amygdala connectivity were rated by parents as having greater internalizing behavioral problems measured on the CBCL, but not cognitive problems. The most correlated voxels in that network localize to the ventromedial prefrontal cortex (vmPFC), predicting 57% of the variance in internalizing problems. Both findings were independent of potential confounds including ratings of TBI severity, time since injury, lesion burden based on acute imaging, demographic variables, and other non-amygdalar rsfMRI metrics (e.g., rACC to PCC connectivity), as well as macro- and microstructural measures of limbic circuitry (e.g., amygdala volume and uncinate fasciculus fractional anisotropy). Supporting the clinical significance of these findings, patients with msTBI had significantly greater externalizing problem ratings than healthy control participants and all the brain-behavior findings were specific to the msTBI group in that no similar correlations were found in the healthy control participants. Taken together, frontoamygdala pathways may underlie chronic dysregulation of behavior and mood in patients with msTBI. Future work will focus on neuromodulation techniques to directly affect frontoamygdala pathways with the aim to mitigate such dysregulation problems.

Sport culture and communication among middle school athletes, parents, and staff: A qualitative study

Middle school (MS) is an intermediary level of education between elementary and secondary school that typically includes students aged 10-15 years. There is limited research within the MS sport setting, particularly related to sport-related injury prevention. This qualitative study aimed to better understand the sport culture within MS sports and the communication strategies used among invested groups (i.e., athletes, parents, staff inclusive of coaches and school nurses). Semi-structured interviews were conducted with 19 athletes, 20 parents, and 18 staff (e.g., coaches, school nurses) from seven MS in two school districts during the 2018/19 and 2019/20 school years. Topics focused on understanding school- and sport-related factors related to education, safety, and communication. Analysis used a consensual qualitative research tradition, in which the research team discussed individually developed themes and categories from transcribed interviews, with the goal of coming to a consensus and creating a codebook. Throughout the coding process, the research team would reconvene to discuss coding decisions until consensus was reached. This study focuses on the themes of sport culture and communication. Dominant categories identified within sport culture related to participants noting why they were interested in MS sports, and their struggles with their perceived roles and engagement (e.g., helping parents stay engaged, finding coaches, oversight of school nurses). Competitiveness and safety could have conflicting roles and priority. Dominant categories identified within communication centered around limited communication between coaches and parents. Technological assistance (e.g., phone apps, websites) was available, but often varied by school and sport. Concussions were seldom discussed unless during the preseason meeting or when one occurred. Findings highlight that the MS sport settings may struggle with incorporating primary prevention into their cultures and ensuring reliable communication among individuals. Novel and tailored approaches to injury prevention are needed to help ensure buy-in and proper implementation.

Assessment of Somatosensory and Motor Processing Time in Retired Athletes with a History of Repeated Head Trauma

Measurement of the adverse outcomes of repeated head trauma in athletes is often achieved using tests where the comparator is ‘accuracy’. While it is expected that ex-athletes would perform worse than controls, previous studies have shown inconsistent results. Here we have attempted to address these inconsistencies from a different perspective by quantifying not only accuracy, but also motor response times. Age-matched control subjects who have never experienced head trauma (n = 20; 41.8 ± 14.4 years) where compared to two cohorts of retired contact sport athletes with a history of head trauma/concussions; one with self-reported concerns (n = 36; 45.4 ± 12.6 years), and another with no ongoing concerns (n = 19; 43.1 ± 13.5 years). Participants performed cognitive (Cogstate) and somatosensory (Cortical Metrics) testing with accuracy and motor times recorded. Transcranial magnetic stimulation (TMS) investigated corticospinal conduction and excitability. Results showed that there was little difference between groups in accuracy scores. Conversely, motor times in all but one test revealed that ex-athletes with self-reported concerns were significantly slower compared to other groups (p ranges 0.031 to <0.001). TMS latency showed significantly increased time (p = 0.008) in the group with ongoing concerns. These findings suggest that incorporating motor times is more informative than considering accuracy scores alone.

Defining an Approach to Monitoring Brain Health in Individuals Exposed to Repetitive Head Impacts: Lessons Learned from Radiation Safety

Recently, there has been increased concern over the effect of repetitive head impacts (RHIs, both concussive and subconcussive impacts) on long-term brain health. This concern has led researchers and policy makers to consider establishing RHI thresholds in order to mitigate the potential long-term effects of RHI exposure. However, the concept of thresholding relies on twin streams of information: 1) biomedical research relevant to the short and long-term risks of exposure to RHIs, and 2) societal standards for "acceptable risk." In the case of RHI, these streams of information have not been cogently combined to inform sensible policy making. In the current editorial, we discuss how the history of radiation safety provides an instructive example of an approach to ford these two streams to derive actionable clinically relevant policies surrounding RHI exposures.

Progranulin deficiency promotes persistent neuroinflammation and causes regional pathology in the hippocampus following traumatic brain injury

Traumatic brain injury (TBI) can be progressive and can lead to the development of a long-term complication termed chronic traumatic encephalopathy. The mechanisms underlying the progressive changes are still unknown; however, studies have suggested that microglia-mediated neuroinflammation in response to TBI may play a fundamental role. This study aimed to determine whether progranulin (PGRN), a major modulator of microglial activity, plays a role in the progressive damage following TBI. PGRN-deficient and wild-type mice were subjected to controlled cortical impact and were observed neuropathologically after 3 days, 7 days, and 5 months. Compared to sham and wild-type mice, the PGRN-deficient mice showed overall stronger microgliosis and astrocytosis. The astrocytosis involved broader areas than the microgliosis and was more prominent in the basal ganglia, hippocampus, and internal capsule in PGRN-deficient mice. Ongoing neuronal death was uniquely observed in the hippocampal CA3 region of PGRN-deficient mice at 5 months after TBI, accompanying the regional chronic microgliosis and astrocytosis involving the CA3 commissural pathway. In addition, there was M1 microglial polarization in the pericontusional area with activated TLR4/MyD88/NF-κB signaling; however, the hippocampus showed only mild M1 polarization 7 days after TBI. Lastly, Morris water maze tests showed PGRN-deficient mice had poorer spatial learning and memory 5 months after TBI than wild-type or sham mice. The data indicated the PGRN deficiency caused TBI progression by promoting persistent microgliosis with microglial polarization and astrocytosis, as well as regional pathology in the hippocampus. The study suggests that PGRN should be evaluated as a potential therapy for TBI.

Titrating the Translational Relevance of a Low-Level Repetitive Head Impact Model

Recently, there has been increased attention in the scientific community to the phenomenon of sub-concussive impacts, those hits to the head that do not cause the signs and symptoms of a concussion. Some authors suggest that sub-concussive impacts may alter behavior and cognition, if sustained repetitively, but the mechanisms underlying these changes are not well-defined. Here, we adapt our well-established weight drop model of repetitive mild traumatic brain injury (rmTBI) to attempt to produce a model of low-level repetitive head impacts (RHI). The model was modified to eliminate differences in latency to right following impact and gross behavioral changes after a single cluster of hits. Further, we varied our model in terms of repetition of impact over a 4-h span to mimic the repeated sub-concussive impacts that may be experienced by an athlete within a single day of play. To understand the effects of a single cluster of RHIs, as well as the effect of an increased impact frequency within the cluster, we evaluated classical behavioral measures, serum biomarkers, cortical protein quantification, and immunohistochemistry both acutely and sub-acutely following the impacts. In the absence of gross behavioral changes, the impact protocol did generate pathology, in a dose-dependent fashion, in the brain. Evaluation of serum biomarkers revealed limited changes in GFAP and NF-L, which suggests that their diagnostic utility may not emerge until the exposure to low-level head impacts reaches a certain threshold. Robust decreases in both IL-1β and IL-6 were observed in the serum and the cortex, indicating downregulation of inflammatory pathways. These experiments yield initial data on pathology and biomarkers in a mouse model of low-level RHIs, with relevance to sports settings, providing a starting point for further exploration of the potential role of anti-inflammatory processes in low-level RHI outcomes, and how these markers may evolve with repeated exposure.

Self-Reported Lifetime Concussion Among Adults: Comparison of 3 Different Survey Questions

OBJECTIVE

Because of limitations in current national data sets, respondent self-report may be critical to obtaining concussion prevalence estimates. We examined whether self-report of lifetime concussion among adults varies with the provision of a concussion definition and by the content of that definition.

SETTING AND PARTICIPANTS

A convenience sample of 6427 American adults who participated in the 2018 Porter Novelli SpringStyles survey.

DESIGN

Cross-sectional.

MAIN MEASURES

Frequency of self-reported concussion by variation in concussion definition.

RESULTS

A quarter of respondents (28.9%) reported experiencing a concussion in their lifetime. While concussion prevalence varied by demographic characteristics, it did not vary significantly by concussion definition. Variation in concussion definition did not result in differences related to recency of last concussion, mechanism of injury, or respondent activity engaged in during which they sustained their most recent concussion.

CONCLUSION

The current study suggested that in this sample of adults, the percentage reporting a concussion did not significantly vary by whether a concussion definition was provided or by the content of the definition. However, research suggests that prompting about mechanism of injury, listing symptoms individually, and considering only athletic populations may affect estimates and these factors should be included in future question comparisons.

Differential neuropathology and functional outcome after equivalent traumatic brain injury in aged versus young adult mice

The CDC estimate that nearly 3 million Americans sustain a traumatic brain injury (TBI) each year. Even when medical comorbidities are accounted for, age is an independent risk factor for poor outcome after TBI. Nonetheless, few studies have examined the pathophysiology of age-linked biologic outcomes in TBI. We hypothesized that aged mice would demonstrate more severe neuropathology and greater functional deficits as compared to young adult mice after equivalent traumatic brain injuries. Young adult (14-week-old) and aged (80-week-old) C57BL/6 male mice underwent an open-head controlled cortical impact to induce TBI or a sham injury. At 30-days post-injury groups underwent behavioral phenotyping, magnetic resonance imaging, and histologic analyses. Contrary to our hypothesis, young adult TBI mice exhibited more severe neuropathology and greater loss of white matter connectivity as compared to aged mice after TBI. These findings correlated to differential functional outcomes in anxiety response, learning, and memory between young adult and aged mice after TBI. Although the mechanisms underlying this age-effect remain unclear, attenuated signs of secondary brain injury in aged TBI mice point towards different inflammatory and repair processes between age groups. These data suggest that age may need to be an a priori consideration in future clinical trial design.

Neuropsychological Change After a Single Season of Head Impact Exposure in Youth Football

OBJECTIVES

Head impact exposure (HIE) in youth football is a public health concern. The objective of this study was to determine if one season of HIE in youth football was related to cognitive changes.

METHOD

Over 200 participants (ages 9-13) wore instrumented helmets for practices and games to measure the amount of HIE sustained over one season. Pre- and post-season neuropsychological tests were completed. Test score changes were calculated adjusting for practice effects and regression to the mean and used as the dependent variables. Regression models were calculated with HIE variables predicting neuropsychological test score changes.

RESULTS

For the full sample, a small effect was found with season average rotational values predicting changes in list-learning such that HIE was related to negative score change: standardized beta (β) = -.147, t(205) = -2.12, and p = .035. When analyzed by age clusters (9-10, 11-13) and adding participant weight to models, the R2 values increased. Splitting groups by weight (median split), found heavier members of the 9-10 cohort with significantly greater change than lighter members. Additionaly, significantly more participants had clinically meaningful negative changes: X2 = 10.343, p = .001.

CONCLUSION

These findings suggest that in the 9-10 age cluster, the average seasonal level of HIE had inverse, negative relationships with cognitive change over one season that was not found in the older group. The mediation effects of age and weight have not been explored previously and appear to contribute to the effects of HIE on cognition in youth football players.

Concussion-Reporting Behavior in Rugby: A National Survey of Rugby Union Players in the United States

BACKGROUND

Rugby is the fastest growing team sport in the United States for male and female athletes. It is a contact/collision sport with an injury risk profile that includes concussions.

PURPOSE

To examine the prevalence of concussions in male and female rugby players in the United States and to characterize behaviors around reporting concussions that could be a target for prevention and treatment efforts.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

An online survey distributed to active members on the USA Rugby membership list was used to examine self-reported concussions in male and female athletes. Concussion-reporting behaviors and return to play after a concussion were also explored. Statistical analysis was used to compare male with female athletes and report differences, with years of experience as a dependent variable.

RESULTS

The proportion of athletes with a history of at least 1 concussion was 61.9% in all respondents. Of those who reported a concussion, 50.8% reported the concussion during the game or practice in which it occurred, and 57.6% reported at least 1 concussion to a qualified medical provider. Overall, 27.7% of participants who reported ≥1 rugby-related concussion in our survey noted that at least 1 of these concussions was not formally reported. The most commonly cited reasons for not reporting a concussion included not thinking that it was a serious injury, not knowing that it was a concussion at the time, and not wanting to be pulled out of the game or practice. Additionally, 61.0% of athletes did not engage in recommended return-to-play protocols after their most recent rugby-related concussion.

CONCLUSION

US rugby union athletes may not report concussions to medical personnel or follow return-to-play protocols guided by medical advice. This could result from a lack of education on concussion recognition and the risks associated with continued play after a concussion as well as limited access to health care. Further education efforts focusing on the identification of concussions, removal from play, and return-to-play protocols are necessary in the US rugby union population.

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.

The brains of elite soccer players are subject to experience-dependent alterations in white matter connectivity

Soccer is the only major sport with voluntary unprotected head-to-ball contact. It is crucial to determine if head impact through long-term soccer training is manifested in brain structure and connectivity, and whether such alterations are due to sustained training per se. Using diffusion tensor imaging, we documented a comprehensive view of soccer players' brains in a sample of twenty-five right-handed male elite soccer players aged from 18 to 22 years and twenty-five non-athletic controls aged 19-24 years. Importantly, none had recalled a history of concussion. We performed a whole-brain tract-based spatial statistical analysis, and a tract-specific probabilistic tractography method to measure the differences of white matter properties between groups. Whole-brain integrity analysis showed stronger microstructural integrity within the corpus callosum tract in soccer players compared to controls. Further, tract-specific probabilistic tractography revealed that the anterior part of corpus callosum may be the brain structure most relevant to training experience, which may put into perspective prior evidence showing corpus callosum alteration in retired or concussed athletes practicing contact sports. Intriguingly, experience-related alterations showed left hemispheric lateralization of potential early signs of concussion-like effects. In sum, we concluded that the observed gains and losses may be due to a consequence of engagement in protracted soccer training that incurs prognostic hallmarks associated with minor injury-induced neural inflammation.

Assessment of Long-Term Effects of Sports-Related Concussions: Biological Mechanisms and Exosomal Biomarkers

Concussion or mild traumatic brain injury (mTBI) in athletes can cause persistent symptoms, known as post-concussion syndrome (PCS), and repeated injuries may increase the long-term risk for an athlete to develop neurodegenerative diseases such as chronic traumatic encephalopathy (CTE), and Alzheimer's disease (AD). The Center for Disease Control estimates that up to 3.8 million sport-related mTBI are reported each year in the United States. Despite the magnitude of the phenomenon, there is a current lack of comprehensive prognostic indicators and research has shown that available monitoring tools are moderately sensitive to short-term concussion effects but less sensitive to long-term consequences. The overall aim of this review is to discuss novel, quantitative, and objective measurements that can predict long-term outcomes following repeated sports-related mTBIs. The specific objectives were (1) to provide an overview of the current clinical and biomechanical tools available to health practitioners to ensure recovery after mTBIs, (2) to synthesize potential biological mechanisms in animal models underlying the long-term adverse consequences of mTBIs, (3) to discuss the possible link between repeated mTBI and neurodegenerative diseases, and (4) to discuss the current knowledge about fluid biomarkers for mTBIs with a focus on novel exosomal biomarkers. The conclusions from this review are that current post-concussion clinical tests are not sufficiently sensitive to injury and do not accurately quantify post-concussion alterations associated with repeated mTBIs. In the current review, it is proposed that current practices should be amended to include a repeated symptom inventory, a cognitive assessment of executive function and impulse control, an instrumented assessment of balance, vestibulo-ocular assessments, and an improved panel of blood or exosome biomarkers.

Clinically Historical and Prospective Associations Between Learning Disorders and Concussion in Young Adult Athletes

Background. Athletes with specific learning disorder (LD) tend to score lower on neuropsychological tests and are at increased risk of personal injury than their counterparts without such disorders. Using a retrospective historical and prospective design, we examined whether adult athletes with LD, the most prevalent of neurodevelopmental disorders, experience greater chances of past and future concussions than their counterparts without LD. We expected to find that young athletes with LD would show greater risk of past (historical) and future (prospective) cerebral concussions. Methods. Participants (95 men and 53 women aged 18 to 25 years) were recruited from university sports teams and followed during an entire season. Of these, 38 participants had a history of LD and 101 had a history of at least 1 concussion (72 males, 29 females) at the preseason baseline. One-third experienced a new concussion. Data analytic procedures include inferential cross-tabulations. Results. Athletes with LD were twice more likely to have a concussion history at baseline and to have a history of multiple concussions than athletes without LD; 95% CI = [0.86, 4.92] and [0.77, 3.40], respectively. Athletes with LD were twice more likely to incur a new concussion than those without LD; 95% CI = [0.86, 4.92]. Conclusions. Adult athletes with LD experience greater chances of previous and future concussions compared with counterparts without LD. Preventive practices regarding individuals with neurodevelopmental disorders may not only prevent the biopsychosocial consequences of brain trauma for the individual, but also represent a cost-effective public health measure.

An Examination of 4 Questions Assessing Self-reported Concussions Among High School Students Participating in Team Sports

OBJECTIVE

Current prevalence estimates of youth sports-related concussions are inconsistent because of variation in methodology and potentially unreported concussions.

METHODS

In 2013, Connecticut, Ohio, and Utah each added different questions that assessed self-reported concussions to the Youth Risk Behavior Survey. Two questions referenced recognition of a concussion by the student, 1 referenced identification by a doctor, and 1 referenced suspicion by a coach. Chi-square analyses were used to identify whether there was an association between demographic characteristics and the concussion questions among high school students who played on at least 1 sports team.

RESULTS

The percentage of students who reported concussions ranged from 17.6% to 20.1%.

CONCLUSIONS

These estimates are higher than rates of concussions diagnosed in emergency departments or reported by athletic trainers but were similar across the 4 questions. The field would benefit from a better understanding of the impact of question wording and format on estimates of concussion prevalence.

Anti-Phospho-Tau Gene Therapy for Chronic Traumatic Encephalopathy

Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disorder caused by repetitive trauma to the central nervous system (CNS) suffered by soldiers, contact sport athletes, and civilians following accident-related trauma. CTE is a CNS tauopathy, with trauma-induced inflammation leading to accumulation of hyperphosphorylated forms of the microtubule-binding protein Tau (pTau), resulting in neurofibrillary tangles and progressive loss of neurons. At present, there are no therapies to treat CTE. We hypothesized that direct CNS administration of an adeno-associated virus (AAV) vector coding for an anti-pTau antibody would generate sufficient levels of anti-pTau in the CNS to suppress pTau accumulation thus interrupting the pathogenic process. Using a serotype AAVrh.10 gene transfer vector coding for a monoclonal antibody directed against pTau, we demonstrate the feasibility of this strategy in a murine CTE model in which pTau accumulation was elicited by repeated traumatic brain injury (TBI) using a closed cortical impact procedure over 5 days. Direct delivery of AAVrh.10 expression vectors coding for either of the two different anti-pTau antibodies to the hippocampus of these TBI mice significantly reduced pTau levels across the CNS. Using doses that can be safely scaled to humans, the data demonstrate that CNS administration of AAVrh.10anti-pTau is effective, providing a new strategy to interrupt the CTE consequences of TBI.

Murine Model of Controlled Cortical Impact for the Induction of Traumatic Brain Injury

The Centers for Disease Control and Injury Prevention estimate that almost 2 million people sustain a traumatic brain injury (TBI) every year in the United States. In fact, TBI is a contributing factor to over a third of all injury-related mortality. Nonetheless, the cellular and molecular mechanisms underlying the pathophysiology of TBI are poorly understood. Thus, preclinical models of TBI capable of replicating the injury mechanisms pertinent to TBI in human patients are a critical research need. The controlled cortical impact (CCI) model of TBI utilizes a mechanical device to directly impact the exposed cortex. While no model can full recapitulate the disparate injury patterns and heterogeneous nature of TBI in human patients, CCI is capable of inducing a wide range of clinically applicable TBI. Furthermore, CCI is easily standardized allowing investigators to compare results across experiments as well as across investigative groups. The following protocol is a detailed description of applying a severe CCI with a commercially available impacting device in a murine model of TBI.

Biomechanics of Blast TBI With Time-Resolved Consecutive Primary, Secondary, and Tertiary Loads

Blast-induced traumatic brain injury (bTBI) has become a signature casualty of recent military operations. In spite of significant clinical and preclinical TBI research, current understanding of injury mechanisms and short- and long-term outcomes is limited. Mathematical models of bTBI biomechanics may help in better understanding of injury mechanisms and in the development of improved neuroprotective strategies. Until present, bTBI has been analyzed as a single event of a blast pressure wave propagating through the brain. In many bTBI events, the loads on the body and the head are spatially and temporarily distributed, involving the primary intracranial pressure wave, followed by the head rotation and then by head impact on the ground. In such cases, the brain microstructures may experience time/space distributed (consecutive) damage and recovery events. The paper presents a novel multiscale simulation framework that couples the body/brain scale biomechanics with micro-scale mechanobiology to study the effects of micro-damage to neuro-axonal structures. Our results show that the micro-mechanical responses of neuro-axonal structures occur sequentially in time with “damage” and “relaxation” periods in different parts of the brain. A new integrated computational framework is described coupling the brain-scale biomechanics with micro-mechanical damage to axonal and synaptic structures.

Unifying Pathophysiological Explanations for Sports-Related Concussion and Concussion Protocol Management: Literature Review

Objective

There is a plethora of theories about the pathophysiology behind a sport-related concussion. In this review of the literature, the authors evaluated studies on the pathophysiology of sport-related concussion and professional athlete return-to-play guidelines. The goal of this article is to summarize the most common hypotheses for sport-related concussion, evaluate if there are common underlying mechanisms, and determine if correlations are seen between published mechanisms and the most current return-to-play recommendations.

Methods

Two authors selected papers from the past 5 years for literature review involving discussion of sport-related concussion and pathophysiology, pathology, or physiology of concussion using mutually agreed-upon search criteria. After the articles were filtered based on search criteria, pathophysiological explanations for concussion were organized into tables. Following analysis of pathophysiology, concussion protocols and return-to-play guidelines were obtained via a Google search for the major professional sports leagues and synthesized into a summary table.

Results

Out of 1112 initially identified publications, 53 met our criteria for qualitative analysis. The 53 studies revealed 5 primary neuropathological explanations for sport-related concussion, regardless of the many theories talked about in the different papers. These 5 explanations, in order of predominance in the articles analyzed, were (1) tauopathy, (2) white matter changes, (3) neural connectivity alterations, (4) reduction in cerebral perfusion, and (5) gray matter atrophy. Pathology may be sport specific: white matter changes are seen in 47% of football reports, tauopathy is seen in 50% of hockey reports, and soccer reports 50% tauopathy as well as 50% neural connectivity alterations. Analysis of the return-to-play guidelines across professional sports indicated commonalities in concussion management despite individual policies.

Conclusions

Current evidence on pathophysiology for sport-related concussion does not yet support one unifying mechanism, but published hypotheses may potentially be simplified into 5 primary groups. The unification of the complex, likely multifactorial mechanisms for sport-related concussion to a few common explanations, combined with unique findings within individual sports presented in this report, may help filter and link concussion pathophysiology in sport. By doing so, the authors hope that this review will help guide future concussion research, treatment, and management.

New generation of headgear for rugby: impact reduction of linear and rotational forces by a viscoelastic material-based rugby head guard

Objectives

In the aim to develop a usable and wearable head guard for rugby that could reduce impact energy and lessen the likelihood of concussive and subconcussive injury during play, a combination of viscoelastic materials was employed to develop a guard with similar dimensions to those currently used in international rugby.

Methods

The head guard was tested for impact energy reduction following linear acceleration, using drop tests, as required by World Rugby. The head guard was also subjected to pendulum tests, allowing acceleration to be simultaneously measured on two headforms, as well as repeated impacts to mimic ageing and repeated use. Impact following rotational acceleration was determined at two impact locations and at three impact velocities.

Results

The viscoelastic head guard (N-Pro) was shown to reduce linear impacts by up to 75% in comparison to the use of a commercially available rugby head guard and repeated impacts did not impair the attenuation of impact energy. Rotational impact energy was also reduced by an average of 34% across three speeds and two sites of impact test sites, in comparison to tested bare headforms.

Conclusions

This heralds a new generation of soft-shelled headgear that could help reduce two primary risk factors in sports-induced mild traumatic brain injury: linear and rotational impacts to the head.

Genetic Testing by Sports Medicine Physicians in the United States: Attitudes, Experiences, and Knowledge

It remains unknown whether and how sports medicine physicians currently utilize genetic testing in their clinical practice. This study sought to assess knowledge of, experience with, and attitudes towards genetic testing by sports medicine physicians in the United States (US). An email with a survey hyperlink was distributed twice to members of the American Medical Society for Sports Medicine (AMSSM) listserv in September 2016, with approximately a 10% response rate. Questions focused on knowledge of, experience with, and attitudes towards testing for different genes related to sports proficiency, injury risk, and disease risk. Few AMSSM physicians believe that genetic testing to adapt training (12%) or to choose a sport (2%) is ready for clinical adoption. Most respondents self-reported minimal knowledge about, and limited experience with, genetic testing. The main exception was screening for sickle cell trait (SCT) for which most (84%) reported moderate/significant/expert knowledge and over two-thirds had ordered testing. Although most respondents thought it appropriate to counsel and test for health conditions associated with cardiac and connective tissue disorders in the setting of a positive family history, only a minority had been asked to do so. Five or fewer respondents (2%) had been asked to test for performance-associated variants (Angiotensin Converting Enzyme (ACE) II and Alpha-Actinin 3 (ACTN3)), and five or fewer (2%) would recommend changes based on the results. Our study provides a baseline of current US sports medicine physicians’ minimal experiences with, and knowledge of, genetic testing. The findings of our study indicate that sports medicine physicians require further genetics education as it relates to sports and exercise in order to be prepared to competently engage with their patients and to develop sound professional organizational policies.

Pros and Cons of 19 Sport-Related Concussion Educational Resources in Canada: Avenues for Better Care and Prevention

Objective: The goal of this research was to assess the effectiveness of available concussion educational resources in Canada, the means used to disseminate this knowledge and the impact of these educational resources on players' concussion prevention knowledge. Methods: We assessed concussion knowledge before and after exposure to one or more of 19 resources introduced through a national program aimed to increase awareness and knowledge of concussion. The effectiveness of the mode of delivery was measured by changes in concussion knowledge scores (CKS) between pre and pro scores. Measures: Concussion knowledge scores (CKS) were calculated for pre- and post- exposure to concussion educational resources and used as a measure of both, the effectiveness of each resource as well as the effectiveness of the delivery method. The effectiveness of each educational resource was also measured by the respondents' rating of each concussion educational resource. Results: Respondents in post-survey had higher CKS than those in pre-survey. Two out of the 19 newly developed concussion educational resources were effective in improving the resource users' CKS. Linear regression showed that using more resources further increased CKS. Four out of six modes of delivery enhanced respondents' concussion knowledge. Conclusion: Our findings demonstrate that the newly developed Canadian concussion educational resources were effective at improving users' concussion knowledge. Our data demonstrates that using three or more resources further enhanced the users' concussion knowledge. Future research, however, is critical to assess whether concussion prevention knowledge is sufficient to reduce injuries and factors influencing it.

Sport-Related Concussion: Knowledge and Reporting Behaviors Among Collegiate Club-Sport Athletes

CONTEXT: 

Previous literature on sport-related concussion (SRC) knowledge and reporting behaviors has been limited to high school and National Collegiate Athletic Association collegiate athletes; however, knowledge regarding collegiate club-sport athletes is limited.

OBJECTIVE: 

To determine the level of SRC knowledge and reporting behaviors among collegiate club-sport athletes and to investigate differences between athletes in traditional and nontraditional sports.

DESIGN: 

Cross-sectional study.

SETTING: 

Survey.

PATIENTS OR OTHER PARTICIPANTS: 

A total of 410 athletes (247 males, 163 females) involved in traditional (n = 244) or nontraditional (n = 165) collegiate club sports.

MAIN OUTCOME MEASURE(S): 

The survey consisted of demographics, recognition of SRC signs and symptoms, general SRC knowledge, and reasons why athletes would not report SRCs. The independent variable was sport type. Sport-related concussion signs and symptoms and general knowledge were assessed by the frequency of correct answers to SRC signs and symptoms and general knowledge questions. Sport-related concussion-reporting behavior frequencies were evaluated by asking participants to indicate reasons why they did not or would not report an SRC.

RESULTS: 

The SRC signs and symptoms knowledge score was 23.01 ± 3.19 and general SRC knowledge score was 36.49 ± 4.16 (maximal score = 43). No differences were present for SRC signs and symptoms knowledge ( F_1,408 = 1.99, P = .16) or general SRC knowledge ( F_1,408 = 3.28, P = .07) between athletes in traditional and nontraditional collegiate club sports. The most common reason for not reporting an SRC was not recognizing it as a serious injury (n = 165, 40.3%). Chi-square tests demonstrated significant relationships between sport type and 5 reasons for not reporting an SRC.

CONCLUSIONS: 

The participants displayed moderate to high levels of knowledge of SRCs but indicated they had failed to or would fail to report SRCs for a variety of reasons. The lack of sports medicine coverage and disconnect between knowledge and injury recognition may make collegiate club-sport athletes more likely to participate while concussed.

Effect of concussion history on symptom burden and recovery following pediatric sports-related concussion

OBJECTIVE The aim of this study was to examine differences in symptom burden and duration until physician-documented clinical recovery among pediatric patients with sports-related concussion (SRC) with and without a history of concussion. METHODS A retrospective chart review was performed for all pediatric patients (7-19 years old) referred to the Pan Am Concussion Program in Winnipeg, Canada, with an SRC and evaluated < 30 days postinjury between September 1, 2013, and August 1, 2015. RESULTS A total of 322 patients with SRC (64.91% male, mean age 13.96 years) who were evaluated a median of 7 days (interquartile range [IQR] 5-11 days) postinjury were included. Patients without a history of concussion endorsed significantly fewer concussion symptoms at initial assessment (median 5.5 symptoms, IQR 1-10 symptoms) than those with a previous concussion (median 7 symptoms, IQR 2-13.25 symptoms; p = 0.036). The median Post-Concussion Symptom Scale scores were 9 (IQR 1-23) for patients with no concussion history and 13 (IQR 3-33) for those with a history of concussion (p = 0.032). For patients with no previous concussion, the median number of days until physician-documented clinical recovery was 23 (IQR 15-44 days) compared with 25 days (IQR 18-43 days) for those with a history of concussion (p = 0.281). There was no significant difference in the proportion of patients who experienced delayed time until physician-documented clinical recovery (> 1 month postinjury) between the groups (p = 0.584). CONCLUSIONS Although a history of concussion may be associated with increased symptom burden following pediatric SRC, there was no difference in the time until physician-documented clinical recovery. Pediatric patients with SRC who have a history of concussion should be managed on an individualized basis. Future work is needed to examine the short- and long-term effects of multiple concussions in children and adolescents.

Regulatory-accepted drug development tools are needed to accelerate innovative CNS disease treatments

Central Nervous System (CNS) diseases represent one of the most challenging therapeutic areas for successful drug approvals. Developing quantitative biomarkers as Drug Development Tools (DDTs) can catalyze the path to innovative treatments, and improve the chances of drug approvals. Drug development and healthcare management requires sensitive, reliable, validated, and regulatory accepted biomarkers and endpoints. This review highlights the regulatory paths and considerations for developing DDTs required to advance biomarker and endpoint use in clinical development (e.g., consensus CDISC [Clinical Data Interchange Standards Consortium] data standards, precompetitive sharing of anonymized patient-level data, and continual alignment with regulators). Summarized is the current landscape of biomarkers in a range of CNS diseases including Alzheimer disease, Parkinson Disease, Amyotrophic Lateral Sclerosis, Autism Spectrum Disorders, Depression, Huntington's disease, Multiple Sclerosis and Traumatic Brain Injury. Advancing DDTs for these devastating diseases that are both validated and qualified will require an integrated, cross-consortium approach to accelerate the delivery of innovative CNS therapeutics.

Risk of Concussion During Sports Versus Physical Education Among New Mexico Middle and High School Students

OBJECTIVES

To measure the risk of concussion among New Mexico middle and high school students during both sports and physical education.

METHODS

Athletic directors or athletic trainers in 147 schools were asked to report the number of concussions occurring during sports and physical education in the 2013 to 2014 school year. We calculated 1-year cumulative incidence rates.

RESULTS

Of the 147 schools, 99 responded (67%). During the school year, 598 students were removed from athletics because of a concussion, a 1-year cumulative incidence of 3.5 per 100. The concussion rate during sports was 3.0: 3.5 for boys and 2.4 for girls (relative risk [RR] = 1.5; 95% confidence interval [CI] = 1.2, 1.7). An additional 335 students experienced concussions during physical education. Concussion rates during physical education were 60% higher than during sports (RR = 1.6; 95% CI = 1.4, 1.8).

CONCLUSIONS

In our data, the risk of concussion was higher in physical education than in sports. This suggests that concussions should be tracked for a wide range of youth athletic activities, not just for sports. Monitoring cumulative incidence, in addition to other measures, may allow comparisons across schools and regions. More prevention efforts are needed.

Local and global challenges in pediatric traumatic brain injury outcome and rehabilitation assessment

Traumatic brain injury (TBI) is a major public health problem associated with high morbidity and mortality rates in children in both high- and low- and middle-income countries. Predicting outcome after pediatric TBI is challenging given the wide range of injury and non-injury-related factors which may have an impact. Some of these factors are relevant globally (like heterogeneity in patient and injury-related factors and research methodology) and others are more specific to local contexts (like sociodemographic and cultural factors). The assessment of rehabilitation outcomes post-TBI are similarly challenging given the various methodological limitations, disparities in access to rehabilitation, and limited awareness of deficits, which are encountered globally, as well as the lack of services in the local settings. In this article, we discuss these global and local challenges to outcome and rehabilitation assessment following pediatric TBI.

Depression and sports-related concussion: A systematic review

CONTEXT

Head injuries are risk factors for chronic depressive disorders, but this association remains poorly explored with regards to concussion.

OBJECTIVES

The objective of this review was to evaluate the incidence of depressive symptoms and depression after sports-related concussion. We also endeavored to identify the response elements regarding the pathophysiology of these symptoms.

METHODS

A systematic search of PubMed and Embase was conducted focusing on papers published until 1st December, 2016, according to PRISMA criteria The following MESH terms were used: (concussion or traumatic brain injury) and sport and (depression or depressive disorder).

RESULTS

A depressive disorder can appear immediately after a concussion: depressive symptoms seem to be associated with the symptoms of the concussion itself. A depressive disorder can also appear later, and is often linked to the frequency and number of concussions. Furthermore, the existence of a mood disorder prior to a concussion can contribute to the onset of a depressive disorder after a concussion.

LIMITS

There is an overall limit concerning the definition of a depressive disorder. In addition, when these studies had controls, they were often compared to high-level athletes; yet, practicing sport regularly is a protective factor against mood pathologies.

CONCLUSIONS

Depressive symptoms after a concussion seem to be associated with postconcussion symptoms. Repeat concussions can contribute to later-onset major depressive disorders. However, playing sports can protect against major depressive disorders: thus, it is essential to evaluate concussions as accurately as possible.

CDC's efforts to improve traumatic brain injury surveillance

INTRODUCTION

Youth sports concussion has become a prominent public health issue due to growing concern about the risk of long-term health effects.

METHOD

A broad spectrum of stakeholders has convened to propose solutions, including a committee of the National Academy of Sciences (NAS) who systematically examined the issue and, in a 2014 report, made a series of recommendations to better address this public health problem.

RESULTS

Among these recommendations, the NAS committee called for CDC to develop a plan for a comprehensive surveillance system to better quantify the incidence and outcomes of youth sports concussion among children 5 to 21years of age. Since the release of the NAS report, CDC has taken action to address this recommendation and, in the process, develop strategies to improve traumatic brain injury (TBI) surveillance more broadly. The challenges outlined by the NAS committee with respect to producing comprehensive incidence estimates of youth sports concussion are not exclusive to youth sports concussion, but also apply to TBI surveillance overall. In this commentary, we will discuss these challenges, the process CDC has undertaken to address them and describe our plan for improving TBI and youth sports concussion surveillance.

The Ability of an Aftermarket Helmet Add-On Device to Reduce Impact-Force Accelerations During Drop Tests

CONTEXT

  The Guardian Cap provides a soft covering intended to mitigate energy transfer to the head during football contact. Yet how well it attenuates impacts remains unknown.

OBJECTIVE

  To evaluate the changes in the Gadd Severity Index (GSI) and linear acceleration during drop tests on helmeted headforms with or without Guardian Caps.

DESIGN

  Crossover study.

SETTING

  Laboratory.

PATIENTS OR OTHER PARTICIPANTS

  Nine new football helmets sent directly from the manufacturer.

INTERVENTION(S)

  We dropped the helmets at 3 velocities on 6 helmet locations (front, side, right front boss, top, rear right boss, and rear) as prescribed by the National Operating Committee on Standards for Athletic Equipment. Helmets were tested with facemasks in place but no Guardian Cap and then retested with the facemasks in place and the Guardian Cap affixed.

MAIN OUTCOME MEASURE(S)

  The GSI scores and linear accelerations measured in g forces.

RESULTS

  For the GSI, we found a significant interaction among drop location, Guardian Cap presence, and helmet brand at the high velocity (F_10,50 = 3.01, P = .005) but not at the low (F_3.23,16.15 = 0.84, P = .50) or medium (F_10,50 = 1.29, P = .26) velocities. Similarly for linear accelerations, we found a significant interaction among drop location, Guardian Cap presence, and helmet brand at the high velocity (F_10,50 = 3.01, P = .002, ω² = 0.05) but not at the low (F_10,50 = 0.49, P = .89, ω² < 0.01, 1-β = 0.16) or medium (F_5.20,26.01 = 2.43, P = .06, ω² < 0.01, 1-β = 0.68) velocities.

CONCLUSIONS

  The Guardian Cap failed to significantly improve the helmets' ability to mitigate impact forces at most locations. Limited evidence indicates how a reduction in GSI would provide clinically relevant benefits beyond reducing the risk of skull fracture or a similar catastrophic event.

The effect of regadenoson on the integrity of the human blood-brain barrier, a pilot study

Regadenoson is an FDA approved adenosine receptor agonist which increases blood-brain barrier (BBB) permeability in rodents. Regadenoson is used clinically for pharmacologic cardiac stress testing using SPECT or CT imaging agents that do not cross an intact BBB. This study was conducted to determine if standard doses of regadenoson transiently disrupt the human BBB allowing higher concentrations of systemically administered imaging agents to enter the brain. Patients without known intracranial disease undergoing clinically indicated pharmacologic cardiac stress tests were eligible for this study. They received regadenoson (0.4 mg) followed by brain imaging with either ^99mTc-sestamibi for SPECT or visipaque for CT imaging. Pre- and post-regadenoson penetration of imaging agents into brain were quantified [SPECT: radioactive counts, CT: Hounsfield units (HU)] and compared using a matched-pairs t-test. Twelve patients (33% male, median 60 yo) were accrued: 7 SPECT and 5 CT. No significant differences were noted in pre- and post-regadenoson values using mean radionuclide counts (726 vs. 757) or HU (29 vs. 30). While animal studies have demonstrated that regadenoson transiently increases the permeability of the BBB to dextran and temozolomide, we were unable to document changes in the penetration of contrast agents in humans with intact BBB using the FDA approved doses of regadenoson for cardiac evaluation. Further studies are needed exploring alternate regadenoson dosing, schedules, and studies in patients with brain tumors; as transiently disrupting the BBB to improve drug entry into the brain is critical to improving the care of patients with CNS malignancies.

A Retrospective Cross-Sectional and Longitudinal Study of the Effects of Age on CNS Vital Signs Scores in High-School Athletes

INTRODUCTION

Current recommendations for concussion management acknowledge the importance of objective assessments of neuropsychological (NP) ability, and computerized NP assessments have been widely integrated into the concussion management protocols of high schools. The optimal intervals for baseline test administration in high-school athletes are currently uncertain. The ability to accurately detect subtle NP deficits is particularly important for high-school athletes, in which concussions are increasingly recognized for adverse effects to the developing brain.

PURPOSE

The aim of this study was to assess the pattern of change in neurocognitive test performance, as well as changes in different domains of NP functioning over time.

METHODS

Baseline computerized NP assessments were conducted at six high schools over 4 academic years using CNS Vital Signs, a battery consisting of seven well-established NP tests. Data were retrospectively examined for age differences in both cross-sectional (n = 3015) and longitudinal (n = 1221) analyses.

RESULTS

Moderate changes were observed across several NP domains over time (Cohen's d = 0.39-0.61), with the largest improvements observed in executive functioning (mean improvement 5.78, 95% confidence interval [CI] 5.41-6.14, p < 0.001), psychomotor speed (mean improvement 4.59, 95% CI 3.97-5.22, p < 0.001), cognitive flexibility (mean improvement 5.11, 95% CI 4.76-5.45, p < 0.001), and reaction time (mean improvement -12.44 ms, 95% CI -10.10 to -14.78, p < 0.001). Improvements in NP performance were most pronounced between the freshman and senior years.

CONCLUSIONS

There is an appreciable change that occurs each year of high school in one or more domains of an NP battery, with executive functioning indicating the greatest magnitude of change. Females performed better relative to males across all time points though males exhibited more substantial improvement over time.

Auditory biological marker of concussion in children

Concussions carry devastating potential for cognitive, neurologic, and socio-emotional disease, but no objective test reliably identifies a concussion and its severity. A variety of neurological insults compromise sound processing, particularly in complex listening environments that place high demands on brain processing. The frequency-following response captures the high computational demands of sound processing with extreme granularity and reliably reveals individual differences. We hypothesize that concussions disrupt these auditory processes, and that the frequency-following response indicates concussion occurrence and severity. Specifically, we hypothesize that concussions disrupt the processing of the fundamental frequency, a key acoustic cue for identifying and tracking sounds and talkers, and, consequently, understanding speech in noise. Here we show that children who sustained a concussion exhibit a signature neural profile. They have worse representation of the fundamental frequency, and smaller and more sluggish neural responses. Neurophysiological responses to the fundamental frequency partially recover to control levels as concussion symptoms abate, suggesting a gain in biological processing following partial recovery. Neural processing of sound correctly identifies 90% of concussion cases and clears 95% of control cases, suggesting this approach has practical potential as a scalable biological marker for sports-related concussion and other types of mild traumatic brain injuries.

Sports Neurology in Clinical Practice: Case Studies

With regard to persistent posttraumatic headache, there is legitimate concern that duration of symptoms may have an impact on the efficacy of future treatment attempts. Without neuropathologic confirmation, a clinical diagnosis of chronic traumatic encephalopathy cannot be made with a high degree of confidence. Sport-related headaches are challenging in a return-to-play context, because it is often unclear whether an athlete has an exacerbation of a primary headache disorder, has new-onset headache unrelated to trauma, or is in the recovery phase after concussion. Regular physical exercise may prove beneficial to multiple neurologic disease states.

Cumulative Head Impact Exposure Predicts Later-Life Depression, Apathy, Executive Dysfunction, and Cognitive Impairment in Former High School and College Football Players

The term "repetitive head impacts" (RHI) refers to the cumulative exposure to concussive and subconcussive events. Although RHI are believed to increase risk for later-life neurological consequences (including chronic traumatic encephalopathy), quantitative analysis of this relationship has not yet been examined because of the lack of validated tools to quantify lifetime RHI exposure. The objectives of this study were: 1) to develop a metric to quantify cumulative RHI exposure from football, which we term the "cumulative head impact index" (CHII); 2) to use the CHII to examine the association between RHI exposure and long-term clinical outcomes; and 3) to evaluate its predictive properties relative to other exposure metrics (i.e., duration of play, age of first exposure, concussion history). Participants included 93 former high school and collegiate football players who completed objective cognitive and self-reported behavioral/mood tests as part of a larger ongoing longitudinal study. Using established cutoff scores, we transformed continuous outcomes into dichotomous variables (normal vs. impaired). The CHII was computed for each participant and derived from a combination of self-reported athletic history (i.e., number of seasons, position[s], levels played), and impact frequencies reported in helmet accelerometer studies. A bivariate probit, instrumental variable model revealed a threshold dose-response relationship between the CHII and risk for later-life cognitive impairment (p < 0.0001), self-reported executive dysfunction (p < 0.0001), depression (p < 0.0001), apathy (p = 0.0161), and behavioral dysregulation (p < 0.0001). Ultimately, the CHII demonstrated greater predictive validity than other individual exposure metrics.

The Effects of External Jugular Compression Applied during Head Impact Exposure on Longitudinal Changes in Brain Neuroanatomical and Neurophysiological Biomarkers: A Preliminary Investigation

OBJECTIVES

Utilize a prospective in vivo clinical trial to evaluate the potential for mild neck compression applied during head impact exposure to reduce anatomical and physiological biomarkers of brain injury.

METHODS

This project utilized a prospective randomized controlled trial to evaluate effects of mild jugular vein (neck) compression (collar) relative to controls (no collar) during a competitive hockey season (males; 16.3 ± 1.2 years). The collar was designed to mildly compress the jugular vein bilaterally with the goal to increase intracranial blood volume to reduce risk of brain slosh injury during head impact exposure. Helmet sensors were used to collect daily impact data in excess of 20 g (games and practices) and the primary outcome measures, which included changes in white matter (WM) microstructure, were assessed by diffusion tensor imaging (DTI). Specifically, four DTI measures: fractional anisotropy, mean diffusivity (MD), axial diffusivity, and radial diffusivity (RD) were used in the study. These metrics were analyzed using the tract-based Spatial Statistics (TBSS) approach - a voxel-based analysis. In addition, electroencephalography-derived event-related potentials were used to assess changes in brain network activation (BNA) between study groups.

RESULTS

For athletes not wearing the collar, DTI measures corresponding to a disruption of WM microstructure, including MD and RD, increased significantly from pre-season to mid-season (p < 0.05). Athletes wearing the collar did not show a significant change in either MD or RD despite similar accumulated linear accelerations from head impacts (p > 0.05). In addition to these anatomical findings, electrophysiological network analysis of the degree of congruence in the network electrophysiological activation pattern demonstrated concomitant changes in brain network dynamics in the non-collar group only (p < 0.05). Similar to the DTI findings, the increased change in BNA score in the non-collar relative to the collar group was statistically significant (p < 0.01). Changes in DTI outcomes were also directly correlated with altered brain network dynamics (r = 0.76; p < 0.05) as measured by BNA.

CONCLUSION

Group differences in the longitudinal changes in both neuroanatomical and electrophysiological measures, as well as the correlation between the measures, provide initial evidence indicating that mild jugular vein compression may have reduced alterations in the WM response to head impacts during a competitive hockey season. The data indicate sport-related alterations in WM microstructure were ameliorated by application of jugular compression during head impact exposure. These results may lead to a novel line of research inquiry to evaluate the effects of protecting the brain from sports-related head impacts via optimized intracranial fluid dynamics.

Resonance of human brain under head acceleration

Although safety standards have reduced fatal head trauma due to single severe head impacts, mild trauma from repeated head exposures may carry risks of long-term chronic changes in the brain's function and structure. To study the physical sensitivities of the brain to mild head impacts, we developed the first dynamic model of the skull-brain based on in vivo MRI data. We showed that the motion of the brain can be described by a rigid-body with constrained kinematics. We further demonstrated that skull-brain dynamics can be approximated by an under-damped system with a low-frequency resonance at around 15 Hz. Furthermore, from our previous field measurements, we found that head motions in a variety of activities, including contact sports, show a primary frequency of less than 20 Hz. This implies that typical head exposures may drive the brain dangerously close to its mechanical resonance and lead to amplified brain-skull relative motions. Our results suggest a possible cause for mild brain trauma, which could occur due to repetitive low-acceleration head oscillations in a variety of recreational and occupational activities.

RISUS study: Rugby Injury Surveillance in Ulster Schools

OBJECTIVE

To examine injury patterns in adolescent rugby players and determine factors associated with injury risk.

DESIGN

Prospective injury surveillance study.

SETTING

N=28 Grammar Schools in Ulster, Ireland (2014-2015 playing season).

PARTICIPANTS

825 adolescent rugby players, across in 28 school first XV rugby squads; mean age 16.9 years.

MAIN OUTCOME MEASURES

Injuries were classified by body part and diagnosis, and injury incidence using injuries per 1000 match hours of exposure. HRs for injury were calculated through Cox proportional hazard regression after correction for influential covariates.

RESULTS

A total of n=426 injuries were reported across the playing season. Over 50% of injuries occurred in the tackle situation or during collisions (270/426), with few reported during set plays. The 3 most common injury sites were head/face (n=102, 23.9%), clavicle/shoulder (n=65, 15.3%) and the knee (n=56, 13.1%). Sprain (n=133, 31.2%), concussion (n=81, 19%) and muscle injury (n=65, 15.3%) were the most common diagnoses. Injury incidence is calculated at 29.06 injuries per 1000 match hours. There were no catastrophic injuries. A large percentage of injuries (208/424) resulted in absence from play for more than 28 days. Concussion carried the most significant time out from play (n=33; 15.9%), followed by dislocations of the shoulder (n=22; 10.6%), knee sprains (n=19, 9.1%), ankle sprains (n=14, 6.7%), hand/finger/thumb (n=11; 5.3%). 36.8% of participants in the study (304/825) suffered at least one injury during the playing season. Multivariate models found higher risk of injury (adjusted HR (AHR); 95% CI) with: higher age (AHR 1.45; 1.14 to 1.83), heavier weight (AHR 1.32; 1.04 to 1.69), playing representative rugby (AHR 1.42; 1.06 to 1.90) and undertaking regular strength training (AHR 1.65; 1.11 to 2.46). Playing for a lower ranked team (AHR 0.67; 0.49 to 0.90) and wearing a mouthguard (AHR 0.70; 0.54 to 0.92) were associated with lower risk of injury.

CONCLUSIONS

There was a high incidence of severe injuries, with concussion, ankle and knee ligament injuries and upper limb fractures/dislocations causing greatest time loss. Players were compliant with current graduated return-to-play regulations following concussion. Physical stature and levels of competition were important risk factors and there was limited evidence for protective equipment.

Myelin and oligodendrocyte lineage cells in white matter pathology and plasticity after traumatic brain injury

Impact to the head or rapid head acceleration-deceleration can cause traumatic brain injury (TBI) with a characteristic pathology of traumatic axonal injury (TAI) and secondary damage in white matter tracts. Myelin and oligodendrocyte lineage cells have significant roles in the progression of white matter pathology after TBI and in the potential for plasticity and subsequent recovery. The myelination pattern of specific brain regions, such as frontal cortex, may also increase susceptibility to neurodegeneration and psychiatric symptoms after TBI. White matter pathology after TBI depends on the extent and distribution of axon damage, microhemorrhages and/or neuroinflammation. TAI occurs in a pattern of damaged axons dispersed among intact axons in white matter tracts. TAI accompanied by bleeding and/or inflammation produces focal regions of overt tissue destruction, resulting in loss of both axons and myelin. White matter regions with TAI may also exhibit demyelination of intact axons. Demyelinated axons that remain viable have the potential for remyelination and recovery of function. Indeed, animal models of TBI have demonstrated demyelination that is associated with evidence of remyelination, including oligodendrocyte progenitor cell proliferation, generation of new oligodendrocytes, and formation of thinner myelin. Changes in neuronal activity that accompany TBI may also involve myelin remodeling, which modifies conduction efficiency along intact myelinated fibers. Thus, effective remyelination and myelin remodeling may be neurobiological substrates of plasticity in neuronal circuits that require long-distance communication. This perspective integrates findings from multiple contexts to propose a model of myelin and oligodendrocyte lineage cell relevance in white matter injury after TBI. This article is part of the Special Issue entitled 'Oligodendrocytes in Health and Disease'.