Biomarkers, genetics, and risk factors for concussion

Concussion-Related Biomarker Variations in Retired Rugby Players and Implications for Neurodegenerative Disease Risk: The UK Rugby Health Study

The health and well-being of retired rugby union and league players, particularly regarding the long-term effects of concussions, are of major concern. Concussion has been identified as a major risk factor for neurodegenerative diseases, such as Alzheimer's and Amyotrophic Lateral Sclerosis (ALS), in athletes engaged in contact sports. This study aimed to assess differences in specific biomarkers between UK-based retired rugby players with a history of concussion and a non-contact sports group, focusing on biomarkers associated with Alzheimer's, ALS, and CTE. We randomly selected a sample of male retired rugby or non-contact sport athletes (n = 56). The mean age was 41.84 ± 6.44, and the mean years since retirement from the sport was 7.76 ± 6.69 for participants with a history of substantial concussions (>5 concussions in their career) (n = 30). The mean age was 45.75 ± 11.52, and the mean years since retirement was 6.75 ± 4.64 for the healthy controls (n = 26). Serum biomarkers (t-tau, RBP-4, SAA, Nf-L, and retinol), plasma cytokines, and biomarkers associated with serum-derived exosomes (Aβ42, p-tau181, p-tau217, and p-tau231) were analyzed using validated commercial ELISA assays. The results of the selected biomarkers were compared between the two groups. Biomarkers including t-tau and p-tau181 were significantly elevated in the history of the substantial concussion group compared to the non-contact sports group (t-tau: p < 0.01; p-tau181: p < 0.05). Although between-group differences in p-tau217, p-tau231, SAA, Nf-L, retinol, and Aβ42 were not significantly different, there was a trend for higher levels of Aβ42, p-tau217, and p-tau231 in the concussed group. Interestingly, the serum-derived exosome sizes were significantly larger (p < 0.01), and serum RBP-4 levels were significantly reduced (p < 0.05) in the highly concussed group. These findings indicate that retired athletes with a history of multiple concussions during their careers have altered serum measurements of exosome size, t-tau, p-tau181, and RBP-4. These biomarkers should be explored further for the prediction of future neurodegenerative outcomes, including ALS, in those with a history of concussion.

Apolipoprotein E e4 is associated with worse self-reported neurobehavioral symptoms following uncomplicated mild traumatic brain injury in U.S. military service members

Past research has found a relationship between the apolipoprotein E (APOE) e4 allele and worse neurobehavioral functioning following mild traumatic brain injury (MTBI) in civilian populations. The purpose of this study was to examine this relationship in service members and veterans (SMVs) following MTBI. Participants were 151 SMVs (103 uncomplicated MTBI; 48 Injured Controls [IC]) prospectively enrolled in the DVBIC-TBICoE 15-Year Longitudinal TBI Study. Participants completed a battery of self-reported neurobehavioral symptom measures on average 76.2 months post-injury (SD = 31.8). APOE genotyping was undertaken using non-fasting blood samples. Participants were classified into four subgroups based on injury (MTBI vs. IC) and APOE e4 allele status (e4 present/absent). In the IC group, there were no significant differences across APOE e4 status subgroups for all measures. In the MTBI group, participants with the APOE e4 allele had significantly worse scores on measures of depression, pain, anxiety, grief, positive well-being, social participation, and resilience compared to those without the e4 allele (d = .44 to d = .69). When comparing the number of 'clinically elevated' neurobehavioral measures simultaneously, the MTBI/e4 present subgroup consistently had a higher number of elevated measures compared to the MTBI/e4 absent, IC/e4 present, and IC/e4 absent subgroups. The APOE e4 allele was associated with poorer neurobehavioral outcome in SMVs in the chronic phase of recovery following MTBI. APOE e4 could be incorporated into screening tools to predict SMVs at risk for poor long-term neurobehavioral outcome in an effort to provide early intervention to improve long-term clinical outcome.

The Influence of Family History of Neurodegenerative Disease on Adolescent Concussion Outcomes

Evidence suggests that factors associated with a family history of neurodegenerative disease (fhNDD) may influence outcomes following a concussion. However, the relevance of these findings in adolescent populations has not been fully explored. Therefore, the present study sought to evaluate the relationship between fhNDD and neurological outcomes following an adolescent concussion. Data from a local pediatric concussion clinic were used to compare adolescents with (n = 22) and without (n = 44) an fhNDD. Clinical symptom burden, emotional health, cardio-autonomic function, and cognitive performance were assessed at initial (~2 weeks) and follow-up (~5 weeks) post-injury evaluations. Cardio-autonomic function was assessed at rest and during isometric handgrip contraction (IHGC). Results indicated no significant group differences in emotional health or cognitive performance. Across evaluations, those with an fhNDD exhibited greater somatic symptom severity, alterations in HRV at rest, and early blunted cardio-autonomic reactivity during IHGC compared to those without an fhNDD. These findings suggest that positive fhNDD is negatively associated with clinical symptomology and cardio-autonomic functioning following an adolescent concussion. Further, these findings encourage clinicians to utilize a comprehensive neurological evaluation to monitor concussion recovery. Future studies should look into exploring the role of specific neurodegenerative processes and conditions on concussion outcomes in adolescents.

Apolipoprotein ɛ4 Status and Brain Structure 12 Months after Mild Traumatic Injury: Brain Age Prediction Using Brain Morphometry and Diffusion Tensor Imaging

Background: Apolipoprotein E (APOE) ɛ4 is associated with poor outcome following moderate to severe traumatic brain injury (TBI). There is a lack of studies investigating the influence of APOE ɛ4 on intracranial pathology following mild traumatic brain injury (MTBI). This study explores the association between APOE ɛ4 and MRI measures of brain age prediction, brain morphometry, and diffusion tensor imaging (DTI). Methods: Patients aged 16 to 65 with acute MTBI admitted to the trauma center were included. Multimodal MRI was performed 12 months after injury and associated with APOE ɛ4 status. Corrections for multiple comparisons were done using false discovery rate (FDR). Results: Of included patients, 123 patients had available APOE, volumetric, and DTI data of sufficient quality. There were no differences between APOE ɛ4 carriers (39%) and non-carriers in demographic and clinical data. Age prediction revealed high accuracy both for the DTI-based and the brain morphometry based model. Group comparisons revealed no significant differences in brain-age gap between ɛ4 carriers and non-carriers, and no significant differences in conventional measures of brain morphometry and volumes. Compared to non-carriers, APOE ɛ4 carriers showed lower fractional anisotropy (FA) in the hippocampal part of the cingulum bundle, which did not remain significant after FDR adjustment. Conclusion: APOE ɛ4 carriers might be vulnerable to reduced neuronal integrity in the cingulum. Larger cohort studies are warranted to replicate this finding.

Predicting Risk of Sport-Related Concussion in Collegiate Athletes and Military Cadets: A Machine Learning Approach Using Baseline Data from the CARE Consortium Study

OBJECTIVE

To develop a predictive model for sport-related concussion in collegiate athletes and military service academy cadets using baseline data collecting during the pre-participation examination.

METHODS

Baseline assessments were performed in 15,682 participants from 21 US academic institutions and military service academies participating in the CARE Consortium Study during the 2015-2016 academic year. Participants were monitored for sport-related concussion during the subsequent season. 176 baseline covariates mapped to 957 binary features were used as input into a support vector machine model with the goal of learning to stratify participants according to their risk for sport-related concussion. Performance was evaluated in terms of area under the receiver operating characteristic curve (AUROC) on a held-out test set. Model inputs significantly associated with either increased or decreased risk were identified.

RESULTS

595 participants (3.79%) sustained a concussion during the study period. The predictive model achieved an AUROC of 0.73 (95% confidence interval 0.70-0.76), with variable performance across sports. Features with significant positive and negative associations with subsequent sport-related concussion were identified.

CONCLUSION(S)

This predictive model using only baseline data identified athletes and cadets who would go on to sustain sport-related concussion with comparable accuracy to many existing concussion assessment tools for identifying concussion. Furthermore, this study provides insight into potential concussion risk and protective factors.

Robotic Semi-Automated Transcranial Doppler Assessment of Cerebrovascular Autoregulation in Post-Concussion Syndrome: Methodological Considerations

Post-concussion syndrome (PCS) refers to a constellation of physical, cognitive, and emotional symptoms after traumatic brain injury (TBI). Despite its incidence and impact, the underlying mechanisms of PCS are unclear. We hypothesized that impaired cerebral autoregulation (CA) is a contributor. In this article, we present our protocol for non-invasively assessing CA in patients with TBI and PCS in a real-world clinical setting. A prospective, observational study was integrated into outpatient clinics at a tertiary neurosurgical center. Data points included: demographics, symptom profile (Post-Concussion Symptom Scale [PCSS]) and neuropsychological assessment (Cambridge Neuropsychological Test Automated-Battery [CANTAB]). Cerebrovascular metrics (nMxa co-efficient and the transient hyperaemic-response ratio [THRR]) were collected using transcranial Doppler (TCD), finger plethysmography, and bespoke software (ICM+). Twelve participants were initially recruited but 2 were excluded after unsuccessful insonation of the middle cerebral artery (MCA); 10 participants (5 patients with TBI, 5 healthy controls) were included in the analysis (median age 26.5 years, male to female ratio: 7:3). Median PCSS scores were 6/126 for the TBI patient sub-groups. Median CANTAB percentiles were 78 (healthy controls) and 25 (TBI). nMxa was calculated for 90% of included patients, whereas THRR was calculated for 50%. Median study time was 127.5 min and feedback (n = 6) highlighted the perceived acceptability of the study. This pilot study has demonstrated a reproducible assessment of PCS and CA metrics (non-invasively) in a real-world setting. This protocol is feasible and is acceptable to participants. By scaling this methodology, we hope to test whether CA changes are correlated with symptomatic PCS in patients post-TBI.

Exploring Neuronal Vulnerability to Head Trauma Using a Whole Exome Approach

Brain injuries are associated with oxidative stress and a need to restore neuronal homeostasis. Mutations in ion channel genes, in particular CACNA1A, have been implicated in familial hemiplegic migraine (FHM) and in the development of concussion-related symptoms in response to trivial head trauma. The aim of this study was to explore the potential role of variants in other ion channel genes in the development of such responses. We conducted whole exome sequencing (WES) on16 individuals who developed a range of neurological and concussion-related symptoms following minor or trivial head injuries. All individuals were initially tested and shown to be negative for mutations in known FHM genes. Variants identified from the WES results were filtered to identify rare variants (minor allele frequency [MAF] <0.01) in genes related to neural processes as well as genes highly expressed in the brain using a combination of in silico prediction tools (SIFT, PolyPhen, PredictSNP, Mutation Taster, and Mutation Assessor). Rare (MAF <0.001) or novel heterozygous variants in 7 ion channel genes were identified in 37.5% (6/16) of the cases (CACNA1I, CACNA1C, ATP10A, ATP7B, KCNAB1, KCNJ10, and SLC26A4), rare variants in neurotransmitter genes were found in 2 cases (GABRG1 and GRIK1), and rare variants in 3 ubiquitin-related genes identified in 4 cases (SQSTM1, TRIM2, and HECTD1). In this study, the largest proportion of potentially pathogenic variants in individuals with severe responses to minor head trauma were identified in genes previously implicated in migraine and seizure-related autosomal recessive neurological disorders. Together with results implicating variants in the hemiplegic migraine genes, CACNA1A and ATP1A2, in severe head trauma response, our results support a role for heterozygous deleterious mutations in genes implicated in neurological dysfunction and potentially increasing the risk of poor response to trivial head trauma.

The possible role of hydration in concussions and long-term symptoms of concussion for athletes. A review of the evidence

The purpose of this review is to address what is known, speculated, and hypothesized regarding the issue of hydration and concussions. Based on the question, “What impact does hydration have on the relative risk for suffering concussive injuries along with long-term ramifications that have been associated with concussive (and repeated subconcussive) traumas to the cerebral cortex?,” a search of available literature was performed through June 2019. Deducing from the available literature, we can stipulate that changes in hydration within the cerebral cortex increase the likelihood for disruption of neurofilament proteins, dysregulation of membrane dynamics of the neurons and exacerbate inflammation responses following head trauma. As such, it can be speculated that differences in incidence rates may be attributed to difference in tissue fluid based on athlete demographics, level of whole-body water balance, and degree of tissue dehydration more than selection of sport. Moreover, tissue hydration in combination with other inflammation factors provides the scaffolding for the development of long-term issues (e.g. chronic traumatic encephalopathy) associated with repetitive head trauma in athletes.

Sex-Related Differences in the Effects of Sports-Related Concussion: A Review

Sports-related concussion is a serious health challenge, and females are at higher risk of sustaining a sports-related concussion compared to males. Although there are many studies that investigate outcomes following concussion, females remain an understudied population, despite representing a large proportion of the organized sports community. In this review, we provide a summary of studies that investigate sex-related differences in outcome following sports-related concussion. Moreover, we provide an introduction to the methods used to study sex-related differences after sports-related concussion, including common clinical and cognitive measures, neuroimaging techniques, as well as biomarkers. A literature search inclusive of articles published to March 2020 was performed using PubMed. The studies were reviewed and discussed with regard to the methods used. Findings from these studies remain mixed with regard to the effect of sex on clinical symptoms, concussion-related alterations in brain structure and function, and recovery trajectories. Nonetheless, there is initial evidence to suggest that sex-related differences following concussion are important to consider in efforts to develop objective biomarkers for the diagnosis and prognosis of concussion. Additional studies on this topic are, however, clearly needed to improve our understanding of sex-related differences following concussion, as well as to understand their neurobiological underpinnings. Such studies will help pave the way toward more personalized clinical management and treatment of sports-related concussion.

Baseline vs. cross-sectional MRI of concussion: distinct brain patterns in white matter and cerebral blood flow

Neuroimaging has been used to describe the pathophysiology of sport-related concussion during early injury, with effects that may persist beyond medical clearance to return-to-play (RTP). However, studies are typically cross-sectional, comparing groups of concussed and uninjured athletes. It is important to determine whether these findings are consistent with longitudinal change at the individual level, relative to their own pre-injury baseline. A cohort of N = 123 university-level athletes were scanned with magnetic resonance imaging (MRI). Of this group, N = 12 acquired a concussion and were re-scanned at early symptomatic injury and at RTP. A sub-group of N = 44 uninjured athletes were also re-imaged, providing a normative reference group. Among concussed athletes, abnormalities were identified for white matter fractional anisotropy and mean diffusivity, along with grey matter cerebral blood flow, using both cross-sectional (CS) and longitudinal (LNG) approaches. The spatial patterns of abnormality for CS and LNG were distinct, with median fractional overlap below 0.10 and significant differences in the percentage of abnormal voxels. However, the analysis methods did not differ in the amount of change from symptomatic injury to RTP and in the direction of observed abnormalities. These results highlight the impact of using pre-injury baseline data when evaluating concussion-related brain abnormalities at the individual level.

Elevated Serum Levels of Inflammation-Related Cytokines in Mild Traumatic Brain Injury Are Associated With Cognitive Performance

Mild traumatic brain injury (mTBI) is the most common neurological insult and leads to long-lasting cognitive impairments. The immune system modulates brain functions and plays a key role in cognitive deficits, however, the relationship between TBI-induced changes in inflammation-related cytokine levels and cognitive consequences is unclear. This was investigated in the present study in two cohorts of individuals within 1 week of mTBI (n = 52, n = 43) and 54 matched healthy control subjects. Patients with mTBI were also followed up at 1 and 3 months post-injury. Measures included cognitive assessments and a 9-plex panel of serum cytokines including interleukin (IL)-1β, IL-4, IL-6, IL-8, IL-10, IL-12, chemokine ligand 2 (CCL2), interferon-γ (IFN-γ), and tumor necrosis factor-α (TNF-α). The contribution of cytokine levels to cognitive function was evaluated by multivariate linear regression analysis. The results showed that serum levels of IL-1β, IL-6, and CCL2 were acutely elevated in mTBI patients relative to controls; CCL2 level was remained high over 3 months whereas IL-1β and IL-6 levels were declined by 3 months post-injury. A high level of CCL2 was associated with greater severity of post-concussion symptoms (which survived in the multiple testing correction); elevated IL-1β was associated with worse working memory in acute phase (which failed in correction); and acute high CCL2 level predicted higher information processing speed at 3 months post-injury (which failed in correction). Thus, acute serum cytokine levels are useful for evaluating post-concussion symptoms and predicting cognitive outcome in participants with mTBI.

Mechanisms underlying vulnerabilities after repeat mild traumatic brain injuries

Traumatic brain injury (TBI) has drawn national attention for its high incidence and mechanistic complexity. The majority of TBI cases are "mild" in nature including concussions and mild TBI (mTBI). Concussions are a distinct form of mTBI where diagnosis is difficult, quantification of the incidence is challenging and there is greater risk for subsequent injuries. While concussions occur in the general population, it has become a hallmark injury consistently observed among adolescent and young adult athletes and the risks for repeat TBI (rTBI) is significant. Clinical and experimental evidence shows that the magnitude and duration of deficits is dependent on the number and the interval between injuries. Several studies suggest that metabolic vulnerabilities after injury may contribute to the window for cerebral vulnerability from rTBI. In addition to metabolism, this review addresses how age, sex and hormones also play an important role in the response to repeat concussions. Understanding how these factors collectively contribute to concussion and rTBI recovery is critically important in establishing age/sex appropriate return to play guidelines, injury prevention, therapeutic interventions and mitigation of long-term consequences of rTBI.

Time Trends of Head Injuries Over Multiple Seasons in Professional Male Football (Soccer)

The present study aimed to investigate time trends of head injuries and their injury mechanisms since a rule change as monitoring may help to identify causes of head injuries and may advance head injury prevention efforts. Based on continuously recorded data from the German football magazine “kicker Sportmagazin ^® ” as well as other media sources, a database of head injuries in the 1 ^st German male Bundesliga was generated comprising 11 seasons (2006/07–2016/17). Injury mechanisms were analysed from video recordings. Injury incidence rates (IR) and 95% confidence intervals (95% CI) were calculated. Time trends were analysed via linear regression. Two hundred thirty-eight match head injuries occurred (IR 1.77/1000 match hours, 95% CI 1.56–2.01). There were no significant seasonal changes, expressed as annual average year-on-year change, in IRs over the 11-year period for total head injuries (p=0.693), facial/head fractures (p=0.455), lacerations/abrasions (p=0.162), and head contusions (p=0.106). The annual average year-on-year increase for concussion was 6.4% (p=0.004). Five head injury mechanisms were identified. There were no seasonal changes in injury mechanisms over the study period. The concussion subcategory increased slightly over the seasons, which may either be a result of increasing match dynamics or raised awareness among team physicians and players.

Sports-related Concussion - Genetic Factors

Genetic biomarkers have been evaluated for validity in predicting risk for sports-related concussion as well as prognosticating recovery from this injury. Research results from predominantly small-scale pilot studies thus far are mixed and preliminary findings have not been adequately replicated. Currently, the use of such genetic biomarkers should be considered investigational and not for routine clinical use.

Concussion in adolescent rugby union players: comprehensive acute assessment protocol and development of the SSC concussion passport to monitor long-term health

Introduction

Sports-related concussion (SRC) can be challenging to diagnose, assess and manage. Much of the SRC research is conducted on adults. The assessment of SRC should aim to identify deficits using a detailed multimodal assessment; however, most studies investigating the effects of SRC use diagnostic tools in isolation. It is likely that a combination of diagnostic tests will improve diagnostic accuracy. In this study, we aim to investigate how concussion affects adolescent rugby players and how a variety of diagnostic tools interact with each other as participants recover from their injury. The study will also determine the logistics of recording an individual’s concussion history on a virtual ‘Concussion Passport’ that would remain with the individual throughout their sporting career to allow monitoring of long-term health.

Methods and analysis

All rugby players (n=211) from the Senior Cup Teams of five schools in Dublin, Ireland will be invited to participate in the study. Baseline testing will be performed at the Sports Surgery Clinic, Dublin (SSC) before the rugby season commences. Participants will be followed up over the course of the rugby season. At baseline and at each postconcussion visit, participants will complete the following: Questionnaire, Sports Concussion Assessment Tool 3, Balance Error Scoring System, Computerised Neurocognitive Testing, Vestibulo-ocular assessment, King Devick test, Graded exercise test, Blood tests, Neck strength, FitBit.

Ethics and dissemination

Ethical approval was obtained from the Sports Surgery Clinic Research Ethics Committee (Approval number: SSC 0020). On completion of the study, further papers will be written and published to present the results of the various tests.

Trial registration number

NCT03624634.

Apolipoprotein E ε4 Genotype Is Associated with Elevated Psychiatric Distress in Veterans with a History of Mild to Moderate Traumatic Brain Injury

As few studies have examined the relationship between the apolipoprotein E (APOE) gene and clinical outcomes after military-related traumatic brain injury (TBI), we aimed to determine whether the ε4 allele of the APOE gene influences neuropsychiatric symptoms in veterans with a history of mild-to-moderate TBI. Participants included 133 veterans (TBI = 79; military controls [MC] = 54) who underwent APOE genotyping and were divided into ε4⁺ (TBI = 18; MC = 15) and ε4^- (TBI = 61; MC = 39) groups. All participants underwent evaluation of psychological distress using the Beck Depression Inventory-II, Beck Anxiety Inventory, and PTSD Checklist-Military Version. Two-way analyses of variance were conducted to examine the effect of group (TBI vs. MC) and APOE-ε4 status (ε4⁺ vs. ε4^-) across symptom measures. There was a significant main effect of group across all symptom measures (TBI > MC; all p values <0.001), no main effect of ε4 genotype (p = 0.152-0.222), and a significant interaction of group by ε4 genotype across all measures (p = 0.027-0.047). Specifically, for TBI participants, ε4⁺ veterans demonstrated significantly higher symptom scores across all measures when compared to ε4^- veterans (p = 0.007-0.015). For MC participants, ε4 status had no effect on the severity of psychiatric symptom scores (p = 0.585-0.708). Our results demonstrate that, in our well-characterized sample of veterans with history of neurotrauma, possession of the ε4 allele conveys risk for increased symptomatology (i.e., depression, anxiety, and post-traumatic stress disorder), even well outside of the acute phase of injury. Findings suggest a meaningful relationship between APOE genotype and psychiatric distress post-TBI, and they suggest that there is a brain basis for the complex neuropsychiatric presentation often observed in this vulnerable population. Future longitudinal studies are needed in order to further our understanding of how genetic factors influence response to TBI.

Genetics Influence Neurocognitive Performance at Baseline but Not Concussion History in Collegiate Student-Athletes

OBJECTIVE

This study investigates 4 single-nucleotide polymorphisms [Apolipoprotein E (APOE), APOE promoter, catechol-O-methyl transferase (COMT), and dopamine D2 receptor] that have been implicated in concussion susceptibility and/or cognitive ability in collegiate student-athletes.

DESIGN

Cross-sectional study.

SETTING

Neuroscience laboratory at Elon University.

PARTICIPANTS

Two hundred fifty division I collegiate student-athletes (66 women, 184 men) from various sports.

INTERVENTION

All participants completed Immediate Postconcussion Assessment and Cognitive Testing (ImPACT) testing at baseline concussion testing and had a buccal swab taken for DNA for genotyping.

MAIN OUTCOME MEASURES

Self-reported history of concussions and neurocognitive performance were taken from ImPACT.

RESULTS

Individuals carrying an ε4 allele in their APOE gene had a significantly slower reaction time (P = 0.001). Individuals homozygous for the Val allele of the COMT gene showed significantly worse impulse control scores (P = 0.014). None of the genotypes were able to predict self-reported concussion history in collegiate student-athletes.

CONCLUSIONS

These results indicate that certain genotypes may influence performance on cognitive testing at baseline and that the APOE genotypes may not influence concussion susceptibility as suggested by past studies.

Is Migraine Headache Associated With Concussion in Athletes? A Case-Control Study

OBJECTIVE

The purpose of this study was to investigate the association between migraine headache and concussion in athletes.

DESIGN

Case-control observational study.

SETTING

A university-associated combined sports neurology and orthopedic sports medicine clinic.

PARTICIPANTS

A total of 221 male (n = 140) and female (n = 81) athletes aged 12 to 24 years, including 115 concussion cases (52%) and 106 orthopedic controls (48%), were included in this study.

INTERVENTIONS

Participants completed a one-page questionnaire that recorded their age, sex, reason for visit (concussion vs any other injury), concussion history, and self/immediate family member migraine headache history.

MAIN OUTCOME MEASURES

The odds of having a previous history of migraine headache were compared in the concussion group versus orthopedic controls.

RESULTS

Controlling for between-group differences in age and sex, there was a significant positive association between concussion group status and history of migraine headache [adjusted odds ratio (OR), 1.90; 95% confidence interval (CI), 1.03-3.50. P = 0.039]. However, when including a previous concussion history in the statistical model, this relationship failed to reach significance [adjusted OR, 1.68; 95% CI, 0.89-3.16. P = 0.107].

CONCLUSIONS

These results suggest that there is an association between migraine headache and concussion in athletes, but the cause-effect nature of this relationship cannot be determined. Migraine headache should be considered a modifying factor when caring for concussed athletes.

Neuropsychiatric aspects of concussion

Over the past decade, concussion has become the most widely discussed injury in contact sports. However, concussions also occur in several other settings, such as non-contact sports, elderly individuals, young children, military personnel, and victims of domestic violence. Concussion is frequently undiagnosed as a cause of psychiatric morbidity, especially when the patient has no history of loss of consciousness or direct head trauma. Almost all of the extant literature focuses on traumatic brain injury and assumes that concussion is merely a mild form of traumatic brain injury, which has resulted in a lack of understanding about what concussion is, and how to diagnose, monitor, and treat its varied neuropsychiatric symptoms. In this Review, we address key issues so that the psychiatric clinician can better understand and treat patients with a clinical phenotype that might be the direct result of, or be exacerbated by, concussion. Future research needs to focus on prospective clinical trials in all affected patient populations (ie, those affected by concussion and those affected by various degrees of traumatic brain injury), the identification of reliable biomarkers that can be used to assist with diagnosis and treatment response, and the development of effective treatment interventions. Clearly differentiating concussion from traumatic brain injury is essential to achieve reliable and clinically relevant outcomes.

Relationship between the apolipoprotein E gene and headache following sports-related concussion

INTRODUCTION

Headache is one of the most commonly reported and longest lasting symptoms that concussed athletes report, yet the etiology of headache symptoms following concussion is not entirely clear. The purpose of this study was to determine whether the e4 allele of the apolipoprotein E (APOE) gene influences the presence and severity of postconcussion headache.

METHOD

Participants were composed of 45 concussed athletes and 43 healthy/nonconcussed athletes who were involved in a clinically based sports concussion management program. All athletes completed the Post-Concussion Symptom Scale (PCSS). The "headache" symptom from the PCSS was the primary outcome variable. Buccal samples were collected and analyzed to determine APOE genotype.

RESULTS

A significantly greater proportion of concussed e4+ athletes than e4- athletes endorsed headache. Furthermore, concussed e4+ athletes endorsed more severe headaches than e4- athletes. When examining the healthy/nonconcussed sample (i.e., athletes at baseline), results showed no differences between e4 allele groups with respect to the presence and severity of headache.

CONCLUSIONS

These findings show that when compared to concussed e4- athletes, e4+ athletes are more likely to (a) endorse postconcussion headache and (b) report more severe headache symptoms following concussion. Conversely, it appears that the e4 allele does not influence baseline reports of headache. Thus, results suggest that those with the e4 genotype may be at a higher risk for experiencing headache-related difficulties only after a concussion is sustained.

Sports-related brain injuries: connecting pathology to diagnosis

Brain injuries are becoming increasingly common in athletes and represent an important diagnostic challenge. Early detection and management of brain injuries in sports are of utmost importance in preventing chronic neurological and psychiatric decline. These types of injuries incurred during sports are referred to as mild traumatic brain injuries, which represent a heterogeneous spectrum of disease. The most dramatic manifestation of chronic mild traumatic brain injuries is termed chronic traumatic encephalopathy, which is associated with profound neuropsychiatric deficits. Because chronic traumatic encephalopathy can only be diagnosed by postmortem examination, new diagnostic methodologies are needed for early detection and amelioration of disease burden. This review examines the pathology driving changes in athletes participating in high-impact sports and how this understanding can lead to innovations in neuroimaging and biomarker discovery.

A review of the neuro- and systemic inflammatory responses in post concussion symptoms: Introduction of the "post-inflammatory brain syndrome" PIBS

Post-concussion syndrome is an aggregate of symptoms that commonly present together after head injury. These symptoms, depending on definition, include headaches, dizziness, neuropsychiatric symptoms, and cognitive impairment. However, these symptoms are common, occurring frequently in non-head injured controls, leading some to question the existence of post-concussion syndrome as a unique syndrome. Therefore, some have attempted to explain post-concussion symptoms as post-traumatic stress disorder, as they share many similar symptoms and post-traumatic stress disorder does not require head injury. This explanation falls short as patients with post-concussion syndrome do not necessarily experience many key symptoms of post-traumatic stress disorder. Therefore, other explanations must be sought to explain the prevalence of post-concussion like symptoms in non-head injury patients. Many of the situations in which post-concussion syndrome like symptoms may be experienced such as infection and post-surgery are associated with systemic inflammatory responses, and even neuroinflammation. Post-concussion syndrome itself has a significant neuroinflammatory component. In this review we examine the evidence of neuroinflammation in post-concussion syndrome and the potential role systemic inflammation plays in post-concussion syndrome like symptoms. We conclude that given the overlap between these conditions and the role of inflammation in their etiologies, a new term, post-inflammatory brain syndromes (PIBS), is necessary to describe the common outcomes of many different inflammatory insults. The concept of post-concussion syndrome is in its evolution therefore, the new term post-inflammatory brain syndromes provides a better understanding of etiology of its wide-array of symptoms and the wide array of conditions they can be seen in.

Chronic traumatic encephalopathy: historical origins and current perspective

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease that is most often identified in postmortem autopsies of individuals exposed to repetitive head impacts, such as boxers and football players. The neuropathology of CTE is characterized by the accumulation of hyperphosphorylated tau protein in a pattern that is unique from that of other neurodegenerative diseases, including Alzheimer's disease. The clinical features of CTE are often progressive, leading to dramatic changes in mood, behavior, and cognition, frequently resulting in debilitating dementia. In some cases, motor features, including parkinsonism, can also be present. In this review, the historical origins of CTE are revealed and an overview of the current state of knowledge of CTE is provided, including the neuropathology, clinical features, proposed clinical and pathological diagnostic criteria, potential in vivo biomarkers, known risk factors, and treatment options.

Elucidating the severity of preclinical traumatic brain injury models: a role for functional assessment?

BACKGROUND

Concussion remains a symptom-based diagnosis clinically, yet preclinical studies investigating traumatic brain injury, of which concussion is believed to represent a "mild" form, emphasize histological end points with functional assessments often minimized or ignored all together. Recently, clinical studies have identified the importance of cognitive and neuropsychiatric symptoms, in addition to somatic concerns, following concussion. How these findings may translate to preclinical studies is unclear at present.

OBJECTIVE

To address the contrasting end points used clinically compared with those in preclinical studies and the potential role of functional assessments in a commonly used model of diffuse axonal injury (DAI).

METHODS

Animals were subjected to DAI by the use of the impact-acceleration model. Functional and behavioral assessments were conducted during 1 week following DAI before the completion of the histological assessment at 1 week post-DAI.

RESULTS

We show, despite the suggestion that this model represents concussive injury, no functional impairments as determined by using the common measures of motor, sensorimotor, cognitive, and neuropsychiatric function following injury over the course of 1 week. The lack of functional deficits is in sharp contrast to neuropathological findings indicating neural degeneration, astrocyte reactivity, and microglial activation.

CONCLUSION

Future studies are needed to identify functional assessments, neurophysiologic techniques, and imaging assessments more apt to distinguish differences following so-called "mild" traumatic brain injury in preclinical models and determine whether these models are truly studying concussive or subconcussive injury. These studies are needed not only to understand the mechanism of injury and production of subsequent deficits, but also to rigorously evaluate potential therapeutic agents.