Second Impact Syndrome or Cerebral Swelling after Sporting Head Injury

Association of Alzheimer's disease polygenic risk score with concussion severity and recovery metrics

Identification of genetic alleles associated with both Alzheimer's disease (AD) and concussion severity/recovery could help explain the association between concussion and elevated dementia risk. However, there has been little investigation into whether AD risk genes associate with concussion severity/recovery, and the limited findings are mixed. We used AD polygenic risk scores (PRS) and APOE genotypes to investigate any such associations in the NCAA-DoD Grand Alliance CARE Consortium (CARE) dataset. We assessed six outcomes in 931 total participants. The outcomes were two concussion recovery measures (number of days to asymptomatic status, number of days to return to play (RTP)) and four concussion severity measures (scores on SAC and BESS, SCAT symptom severity, and total number of symptoms). We calculated PRS using a published score [1] and performed multiple linear regression (MLR) to assess the relationship of PRS with the outcomes. We also used t-tests and chi-square tests to examine outcomes by APOE genotype, and MLR to analyze outcomes in European and African genetic ancestry subgroups. Higher PRS was associated with longer injury to RTP in the normal RTP (<24 days) subgroup ( p = 0.024), and one standard deviation increase in PRS resulted in a 9.89 hour increase to the RTP interval. There were no other consistently significant effects, suggesting that high AD genetic risk is not strongly associated with more severe concussions or poor recovery in young adults. Future studies should attempt to replicate these findings in larger samples with longer follow-up using PRS calculated from diverse populations.

Acute Fluid Biomarkers for Diagnosis and Prognosis in Children with Mild Traumatic Brain Injury: A Systematic Review

BACKGROUND AND OBJECTIVE

Fluid biomarkers have the potential to improve the accuracy of diagnosis and prognosis in children with mild traumatic brain injury. Our primary objective was to assess the diagnostic and prognostic utility of acute blood and fluid biomarkers in children with mild traumatic brain injury.

METHODS

We performed a systematic review of the published literature in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology. Fluid biomarker studies assessing pediatric mild traumatic brain injury diagnosis or prognosis were included if blood or fluids were sampled within 24 h of injury.

RESULTS

Thirty-two studies involving 4743 patients were included comprising 25 diagnostic studies and ten prognostic studies with three studies assessing both diagnosis and prognosis. Sixteen of the 25 diagnostic studies reported the area under the receiver operating characteristic curve (AUC) for predicting abnormal computed tomography scans of the head; S100 calcium binding protein B (S100B, N = 6 studies, AUC range 0.67-1.00), glial fibrillary acidic protein (N = 5, AUC range 0.41-0.85), ubiquitin C-terminal hydrolase (N = 3, AUC 0.59 and 0.83), neuron specific enolase (N = 1, AUC 0.99), total tau (N = 1, AUC 0.65), and interleukin-6 (N = 1, AUC 0.61). In four of the ten prognostic studies, increased acute serum S100B levels, tumor necrosis factor-α, or interleukin-8 were associated with post-concussive symptoms or fatigue from 3 to 12 months post-injury.

CONCLUSIONS

The largest amount of evidence supported the potential use of S100B, glial fibrillary acidic protein, and UCH-L1, but there was mixed accuracy for diagnosis and prognostication for all biomarkers in pediatric mTBI.

Investigation of concussion knowledge and attitudes of Chinese amateur adolescent soccer athletes

Concussions are a common traumatic brain injury in soccer games but are often ignored by coaches and athletes. The purpose of our study is to assess the concussion knowledge and attitudes among amateur adolescent soccer athletes in China. Data was collected from questionnaire surveying (Rosenbaum Concussion Knowledge and Attitudes Survey (Student Version)) and semi-structured interviews completed by 69 amateur adolescent soccer athletes who participated in the U17 and U15 male groups of the 2022 China Youth Soccer League. The study followed a mixed methodology cross sectional study design. The concussion knowledge index (0-25) and concussion attitude index (15-75) scores were derived from the questionnaire and descriptive statistics were used for data analysis. The mean score of concussion knowledge is 16.8 ± 2.4 (range 10-22), and the mean score of concussion attitude is 61.3 ± 8.8 (range 45-77). Thematic analysis was used to categorize the participant's responses of the semi-structured interview and the results were compared with their survey answers of questionnaire. Interestingly, the interviews revealed the inconsistencies between the questionnaire responses and intended behaviors, and multiple factors (injury severity, the importance of the game and substitution rules) influencing concussion-reporting behaviors were identified. In addition, athletes hope to acquire concussion knowledge through formal education. Our study lay the foundation for educational interventions to potentially improve concussion-reporting behaviors among amateur adolescent soccer athletes.

Continuum of care and longitudinal recovery in a 17-year-old athlete with second impact syndrome

Second impact syndrome (SIS) is an uncommon, but devastating sports-related structural brain injury that results from a second head injury before complete recovery from an initial concussion. The pathophysiology of second impact syndrome is poorly understood, but is hypothesized to involve loss of autoregulation, diffuse cerebral edema, with progression to rapid brain herniation syndromes. Here, we present a case of second impact syndrome in an adolescent high school football player who experienced acute brain herniation and coma. Following stabilization, the patient underwent comprehensive, multidisciplinary rehabilitation in order to achieve significant recovery. A narrative detailing the patient's recovery from one-year post-injury is reviewed.

Blood Biomarkers for Return to Play after Concussion in Professional Rugby Players

We prospectively evaluated a panel of seven blood biomarkers (S100 calcium-binding protein B [S100B], neuron specific enolase [NSE], spectrin breakdown products [SBDP], ubiquitin C-terminal hydrolase L1 [UCHL1], glial fibrillary acidic protein [GFAP], neurofilament light chain [NFL], and tubulin-associated unit [Tau]) for sport-related concussion (SRC) in a large multi-centric cohort of 496 professional rugby players from 14 French elite teams. Players were sampled twice during the season (beginning and end) away from any sport practice. From these two baseline samples, we evaluated the intra-individual variability to establish the effect of rugby on blood biomarkers over a season. Only S100B and GFAP remained stable over the course of a season. During the period of the study, a total of 45 SRC cases was reported for 42 players. In 45 SRCs, the head injury assessment (HIA) process was performed and blood collection was realized 36 h after the concussion (HIA-3 stage). For each biomarker, raw concentrations measured 36 h after SRC were not significantly different between players with a non-resolutive SRC (n = 28) and those with a resolutive SRC (n = 17; p between 0.06 and 0.92). In a second step, blood concentrations measured 36 h after SRC were expressed according to the basal concentrations as an individual percentage change (PCH36[%]), calculated as follows: PCH36 = 100 × (([Biomarker]36h - [Biomarker]basal)/[Biomarker]basal). S100B and NFL concentrations expressed as PCH36[%] were significantly different between non-resolutive and resolutive SRCs (p = 0.006 and 0.01 respectively), with a positive delta found in non-resolutive SRCs. Among the two biomarkers, it is important to note that only the S100B protein was stable during the season. In the context of our study, during HIA-3 assessment, S100B seems to perform better than NSE, SBDP, UCHL1, GFAP, NFL, and Tau as biomarker for SRC. From a clinical standpoint, the S100B modification over baseline may be valuable, at 36 h after concussion to distinguish non-resolutive SRC from resolutive SRC.

Use of Traditional Mongolian Medicine in Children with Concussion

(1) Background: There is no specific treatment for concussion in modern medicine, and existing treatment is only limited to resting and restoring cognition. For centuries, Mongolians have used traditional Mongolian medicine (TMM) methods to treat a variety of diseases such as Baria zasal. In this study, we aimed to explore the treatment parents and guardians seek when their children have suffered a concussion. (2) Methods: In this study, we used an online questionnaire. The study participants (n = 400) were randomly selected parents and guardians. The definition of bariachi is an advanced practitioner of baria zasal, which covers most of the massage therapy techniques mentioned in this study. (3) Results: In total, 72% of the parents and guardians went to a bariachi when their children suffered a concussion, while only 10.3% chose western medical hospitals. When asked what they did after the initial treatment was not effective, 47.8% of the participants responded that they went to the bariachi. Based on the days of treatment result, 11.8% reported on the beneficial effects of the treatment appearing in one day, and 60.3% in 1−3 days, which shows that the participants suffered a healing effect of the baria zasal shortly after application to their children. In the regression analysis, visiting a Bariachi was independent of age, gender, or even religion. (4) Conclusions: Although Western medicine is highly developed in Mongolia, the baria zasal of TMM has not lost its appeal in treating concussion. This suggests that baria zasal could be a unique method of concussion treatment even today. This also suggests that the techniques of Baria zasal should be further studied, and as in modern medicine.

What is a Repetitive Concussion in Sports?

OBJECTIVES Athletes are in a unique situation where they experience repeated concussions while participating in competitions. Although repeated exposure to a concussion has a high risk of negatively affecting athletes' performance and health after retirement, awareness of it is very low in athletes and sports associations. Therefore, the purpose of this review is to provide the basic information about the concussion problem that occurs repeatedly in sports and to establish the plan for the concussion reduction strategy.METHODS To provide the basic information related to a concussion problem in sports, the narrative review was applied.RESULTS The definition, symptoms and symptoms of a sports-related concussion, second impact syndrome, long-term sequelae from the concussion, the preventive effect of the helmet, and the guideline for the safe return to sports after concussion were discussed.CONCLUSIONS This study has reviewed the lack of awareness of concussions that occur repeatedly in the sports field and the problems related to the safety and health of the athletes. In order to reduce a concussion incidence and surrounding issues, the concussion reduction strategy has been proposed, and persistent interest is required from athletes, coaches, parents, and related sports organizations in relation to concussions.

A Scoping Review: Mapping the Evidence for Undergraduate Concussion Education and Proposing the Content for Medical Student Concussion Teaching

INTRODUCTION

Concussion is a common yet complex condition, with each new case requiring assessment by a medical doctor. Recent research has shown that doctors working in the UK have significant knowledge deficits regarding concussion diagnosis and management.

AIM

The aim of this scoping review was to map out the evidence about how undergraduate medical students are being educated about concussion.

METHOD

This scoping review involved seven research papers identified by searching five online databases in October 2020. Search terms relevant to concussion included: brain injuries, post-concussion syndrome, brain concussion and concussion, combined with search criteria for undergraduate education: medical students, undergraduate medical education, or curriculum.

RESULTS

All seven papers were published in North America, with five papers recruiting medical students from single institutions (n = 590) and two papers surveying universities. Canadian medical schools have shown an upward trend in the quantity of teaching about concussion-specific teaching: from 0.57 to 2.65 h between 2012 and 2018. Lectures were the commonest mode of delivery of teaching, followed by problem-based learning and clinical rotations. The studies reach a common conclusion that medical students are not being adequately prepared for diagnosing and managing concussion, with insufficient undergraduate teaching, particularly exposure during clinical rotations, cited as the cause.

CONCLUSIONS

Concussion: education of medical students is inadequate in North America. Medical schools should help address this by providing lectures and clinical presentations on concussion to learn from, particularly via problem-based learning. There is a paucity of evidence about concussion education in other geographical areas.

A Scoping Review of Concussion Guidelines in Amateur Sports in the United Kingdom

Objectives To investigate which United Kingdom (UK) amateur sporting organisations have published sports-related concussion (SRC) guidelines, their accessibility and the extent to which they follow the Berlin statement recommendations. This article is targeted at those involved with designing and implementing SRC guidelines in amateur sport. Design Scoping Review. Data Sources The SRC guidelines of 15 sporting organisations were accessed through public materials available from the official organisation website. Eligibility Criteria: To be included in this review, sports must enjoy broad participation by UK amateur athletes with a high risk of athletes sustaining an SRC. Results: 15 sporting organisations were included in this review with two, British Cycling and British Eventing, found not to have published SRC guidelines. There was found to be a large discrepancy between the extent to which the sport-specific guides followed the Berlin statement recommendations. Conclusions: The large discrepancy between the contents of the SRC guidelines may be putting the health of athletes at risk. We recommend the UK government publish standardised concussion guidelines based on the latest scientific research that must be used by all UK amateur sport groups.

Relating strain fields with microtubule changes in porcine cortical sulci following drop impact

The biomechanical response of brain tissue to strain and the immediate neural outcomes are of fundamental importance in understanding mild traumatic brain injury (mTBI). The sensitivity of neural tissue to dynamic strain events and the resulting strain-induced changes are considered to be a primary factor in injury. Rodent models have been used extensively to investigate impact-induced injury. However, the lissencephalic structure is inconsistent with the human brain, which is gyrencephalic (convoluted structure), and differs considerably in strain field localization effects. Porcine brains have a similar structure to the human brain, containing a similar ratio of white-grey matter and gyrification in the cortex. In this study, coronal brain slabs were extracted from female pig brains within 2hrs of sacrifice. Slabs were implanted with neutral density radiopaque markers, sealed inside an elastomeric encasement, and dropped from 0.9 m onto a steel anvil. Particle tracking revealed elevated tensile strains in the sulcus. One hour after impact, decreased microtubule associated protein 2 (MAP2) was found exclusively within the sulcus with no increase in cell death. These results suggest that elevated tensile strain in the sulcus may result in compromised cytoskeleton, possibly indicating a vulnerability to pathological outcomes under the right circumstances. The results demonstrated that the observed changes were unrelated to shear strain loading of the tissues but were more sensitive to tensile load.

Trends in match concussion incidence and return-to-play time in male professional Rugby Union: A 16-season prospective cohort study

AIM

To describe trends in the incidence of match concussions and time to return-to-play in professional rugby union.

METHODS

Match concussion incidence (injuries per 1000 player-match-hours) and time to return-to-play (mean and median days absence) were recorded in 3006 male professional rugby union players over 16 seasons (2002/03 - 2018/19).

RESULTS

From 2002/03 to 2009/10, incidence of concussions was stable at 4.3/1000 player-match-hours. From 2009/10 to 2018/19, there was an increase in concussion incidence, with the highest incidence in 2016/17 at 20.9/1000 player-match-hours (95% CI: 17.9-24.3). Annual prevalence of concussion also increased, suggesting more players were concussed rather than the same players sustaining more concussions. Before the introduction of standardized graduated return-to-play (GRTP) guidelines in 2011, 27% of players returned to play in <6 days. After the introduction of the GRTP, this decreased to 7%, with no players returning in <6 days after 2014/15. Between 2002/03 and 2018/19, incidence of all other injuries remained stable.

CONCLUSIONS

From 2009/10 onwards, the incidence of diagnosed concussions increased. Since the introduction of the GRTP, there has been a dramatic reduction in the number of players returning in <6 days.

Continued play following adolescent sport-related concussion: Prospective data from the North Texas Concussion Registry (ConTex)

Our study aims were to identify the frequency of continued play following sport-related concussion (SRC), defined as continuing athletic activity on the same day following a suspected SRC, characteristics associated with continued play, and whether continued play was associated with worse outcomes. A prospective study of participants ages 13-18 years diagnosed with SRC at a pediatric sports medicine clinic over a 4-year period was conducted. A comparison was performed between athletes who reported continued play following SRC (PLAY) and those who did not (NO PLAY). Of 441 participants, 231 (52.4%) were in the PLAY group. The PLAY group recalled less severe balance problems from the day of injury (p = 0.02), but reported greater symptoms of trouble falling asleep, concentrating, and remembering at their initial clinic visit (p < 0.05). There was no difference in recovery time between groups. Greater symptom severity score at the initial clinic visit and longer time to presentation were associated with prolonged recovery in both groups (p < 0.01). In conclusion, more than half of the athletes in this sample continued to play on the same day following SRC. Our results indicate the need for a heightened focus on education and additional efforts to reduce continued play following SRC in adolescents.

The Nocebo Effect and Pediatric Concussion

While placebo effects are well recognized within clinical medicine, "nocebo effects" have received much less attention. Nocebo effects are problems caused by negative expectations derived from information or treatment provided during a clinical interaction. In this review, we examine how nocebo effects may arise following pediatric concussion and how they may worsen symptoms or prolong recovery. We offer several suggestions to prevent, lessen, or eliminate such effects. We provide recommendations for clinicians in the following areas: terminology selection, explicit and implicit messaging to patients, evidence-based recommendations, and awareness of potential biases during clinical interactions. Clinicians should consider the empirically grounded suggestions when approaching the care of pediatric patients with concussion.

A Biomarker for Concussion: The Good, the Bad, and the Unknown

BACKGROUND

Traumatic brain injury (TBI) is a significant cause of morbidity, mortality, and disability in the US, with >2.8 million patients presenting to the emergency department (ED) annually. However, the diagnosis of TBI is challenging and presents a number of difficulties, particularly at the mildest end of the spectrum: concussion. A number of groups have researched biomarkers to aid in the evaluation of TBI, and most recently in 2018 the Food and Drug Administration approved a new blood-based immunoassay biomarker using ubiquitin carboxyl hydrolase L1 and glial fibrillary acidic protein to aid in head computed tomography (CT) triage.

CONTENT

This review clarifies the practical challenges in assessing and implementing a new blood biomarker. It then examines the clinical context and need, as well as the evidence used to validate this new immunoassay.

SUMMARY

Concussion is a multifaceted diagnosis with a need for biomarkers to assist in diagnostic and prognostic assessment. Recent articles in the lay press have revealed misunderstanding about the function of this new test, expressing hopes that this biomarker serves patients at the mildest end of the spectrum and is useful for athletes and children. None of these assumptions are correct, as this biomarker has been evaluated in patients only at the moderate end of the spectrum and has been validated only in adults presenting to the ED who have already been triaged to receive head CT, not in athletes or children. The next steps for this assay should consider clinical work flow and clarifying its intended use, including integration with existing triage methods, and validating the assay for a broader population.

An Examination of Perceived Pressure From Stakeholders on Concussion Reporting Intentions and Behavior in Ice Hockey Athletes

OBJECTIVE

We aimed to assess whether perceived pressure predicts concussion reporting intentions and behavior in youth, high school, and collegiate ice hockey athletes, and, secondarily, whether perceived pressure from stakeholders differed between sex or level of play.

SETTING

Online survey.

PARTICIPANTS

One hundred fifty-two ice hockey athletes (males: n = 96, 63.2%; females: n = 55, 36.2%; missing: n = 1, 0.7%; age = 14.04 ± 3.6 years).

DESIGN

Cross-sectional.

MAIN MEASURES

Respondents answered a survey that elicited information about demography, perceived pressure from 6 stakeholders, and concussion reporting intentions and behavior. For the first aim, we used a generalized linear model to determine whether perceived pressure from any stakeholder predicted intention (symptom reporting, concussion reporting, and intention beliefs) or behavior ("all concussions," "not obvious concussions"; α < .05) while controlling for level of play. To determine whether pressure from any stakeholder predicted symptom reporting behavior, we used logistic regression while controlling for level of play. For the second aim, to examine sex differences in perceived pressure from each stakeholder, we employed Mann-Whitney tests and to examine level of play differences, we used Kruskal-Wallis tests.

RESULTS

Controlling for level of play, a 1-point increase in perceived pressure from parents and athletic administrators decreased concussion reporting intentions by 0.92 (P = .004) and 1.09 (P = .005) points, respectively. Perceived pressure from a sports medicine professional decreased intention beliefs by 0.17 (P = .029) points. Perceived pressure from stakeholders did not predict symptom reporting (P = .440) or "not obvious concussion" reporting (P = .655) behavior. We observed no difference in perceived pressure across stakeholders (all P values >.05); however, collegiate ice hockey respondents perceived greater pressure from coaches than youth or high school athletes (P < .001). We noted no other differences in perceived pressure across levels of play (all P values >.05).

CONCLUSIONS

Concussion reporting intentions were negatively influenced by perceived pressure from parents, athletic administrators, and sports medicine professionals, but these findings did not translate to reporting behavior.

Epidemiology of American Football Injuries at Universities in the United Kingdom

Background:

College-level American football injury data are routinely collected; however, data relating to American football injuries at universities in the United Kingdom have never been reported.

Purpose:

To describe the epidemiology of UK university American football injuries.

Study Design:

Descriptive epidemiology study.

Methods:

An online survey tool was used to collect the injury data of 410 players from 56 UK university teams who participated in the 2014-2015 British Universities and College Sports American football season. Survey data were collected from January to February 2016 and were analyzed to determine the incidence and patterns of injury.

Results:

Overall, 710 injuries and 204 concussions were self-reported among the 410 participants, of which 334 (81.5%) were injured and 131 (32.0%) experienced concussion symptoms. The rate of injury per 100 athlete-seasons was greater in defensive players (195.3) than offensive players (155.1). The most common injuries were knee and ankle ligament injuries. Most injuries were classified as severe (time loss of >4 weeks).

Conclusion:

UK university American football injuries differ markedly from those reported for US colleges. UK university players appear to have less playing experience, greater concussion risks, more severe injuries, and a greater proportion of injuries in defensive players versus offensive players.

Psychologists' Role in Concussion Assessments for Children and Adolescents in Pediatric Practice

An estimated 1.1 to 1.9 million children and adolescents in the United States are treated for a sports- or recreationally-related concussion each year. The importance of formalized assessment and measurement of concussion symptoms has been widely recognized as a component of best-practice treatment. The present paper reviews a sample of the most commonly used measures of concussion symptomology and explores psychologists' role in their application in a pediatric practice. In addition, other issues such as accessibility and the appropriateness of application with child and adolescent patients are discussed. Literature is reviewed from journals pertaining to pediatric and adolescent medicine, sports medicine, neuropsychology, and testing and measurement.

Second Impact Syndrome. Myth or reality?

INTRODUCTION

Second impact syndrome (SIS) is a devastating condition occurring in sport-induced mild brain injury. SIS is drastically defined by anamnestic, clinical and radiological criteria, which is unusual in the field of cranial traumatology. The purpose of this study was to provide a literature review of this syndrome.

MATERIAL AND METHODS

We conducted a literature review of all published studies on PubMed. The keywords were "second impact syndrome and catastrophic head injury", "second impact syndrome and sport", "repeat concussion and catastrophic brain injury", "catastrophic head injury and concussion", "catastrophic head injury", "concussion and second impact syndrome", "concussion and repetitive head injury".

RESULTS

Eighty-two full-text articles were assessed for eligibility. Finally, 41 studies were included in qualitative synthesis and 21 were included in quantitative synthesis.

DISCUSSION

The number of cases reported in the literature was extremely small compared to the population at risk, i.e., the number of athletes exposed to repeated concussions. SIS was similar to talk and die syndrome, with which it shares certain characteristics. If we consider SIS according to "talk and deteriorate tables", it opens up interesting perspectives because they are specific in children and adolescents. Taking into account the scarcity of this syndrome, one may question whether athlete-intrinsic features may be involved in at least some cases of SIS. On a pathophysiological level, many explanations remained unsatisfactory because they were unable to explain all the clinical phenomena and observed lesions. Triggering the trigeminocardiac reflex is a crucial element in explaining the sequence of clinical events. Its association with a state of neurogenic inflammation provides an almost complete explanation for this particular condition. Finally, on a practical level, a concussion occurring during the playing of a sport must be considered as any other injury before allowing a return to play.

Electrophysiological Markers of Visuospatial Attention Recovery after Mild Traumatic Brain Injury

Objective: Attentional problems are amongst the most commonly reported complaints following mild traumatic brain injury (mTBI), including difficulties orienting and disengaging attention, sustaining it over time, and dividing attentional resources across multiple simultaneous demands. The objective of this study was to track, using a single novel electrophysiological task, various components associated with the deployment of visuospatial selective attention. Methods: A paradigm was designed to evoke earlier visual evoked potentials (VEPs), as well as attention-related and visuocognitive ERPs. Data from 36 individuals with mTBI (19 subacute, 17 chronic) and 22 uninjured controls are presented. Postconcussion symptoms (PCS), anxiety (BAI), depression (BDI-II) and visual attention (TEA Map Search, DKEFS Trail Making Test) were also assessed. Results: Earlier VEPs (P1, N1), as well as processes related to visuospatial orientation (N2pc) and encoding in visual short-term memory (SPCN), appear comparable in mTBI and control participants. However, there appears to be a disruption in the spatiotemporal dynamics of attention (N2pc-Ptc, P2) in subacute mTBI, which recovers within six months. This is also reflected in altered neuropsychological performance (information processing speed, attentional shifting). Furthermore, orientation of attention (P3a) and working memory processes (P3b) are also affected and remain as such in the chronic post-mTBI period, in co-occurrence with persisting postconcussion symptomatology. Conclusions: This study adds original findings indicating that such a sensitive and rigorous ERP task implemented at diagnostic and follow-up levels could allow for the identification of subtle but complex brain activation and connectivity deficits that can occur following mTBI.

Sports Medicine Update: Concussion

A systematic approach is required for patients with a suspected concussion. Although standardized tools can aid in assessment, the diagnosis of concussion remains a clinical one. At the time of diagnosis, patients should be given both verbal and written review of the common symptoms of concussion, expected course of recovery, as well as strategies to manage symptoms. Most patients benefit from a brief period of rest, followed by a gradual reintroduction of activities, and a graduated return-to-sport protocol. Patients with prolonged recovery from a concussion may benefit from exercise, vestibular, and cognitive rehabilitation programs.

A Mouse Model of Repetitive Blast Traumatic Brain Injury Reveals Post-Trauma Seizures and Increased Neuronal Excitability

Repetitive blast traumatic brain injury (TBI) affects numerous soldiers on the battlefield. Mild TBI has been shown to have long-lasting effects with repeated injury. We have investigated effects on neuronal excitability after repetitive, mild TBI in a mouse model of blast-induced brain injury. We exposed mice to mild blast trauma of an average peak overpressure of 14.6 psi, repeated across three consecutive days. While a single exposure did not reveal trauma as indicated by the glial fibrillary acidic protein indicator, three repetitive blasts did show significant increases. As well, mice had an increased indicator of inflammation (Iba-1) and increased tau, tau phosphorylation, and altered cytokine levels in the spleen. Video-electroencephalographic monitoring 48 h after the final blast exposure demonstrated seizures in 50% (12/24) of the mice, most of which were non-convulsive seizures. Long-term monitoring revealed that spontaneous seizures developed in at least 46% (6/13) of the mice. Patch clamp recording of dentate gyrus hippocampus neurons 48 h post-blast TBI demonstrated a shortened latency to the first spike and hyperpolarization of action potential threshold. We also found that evoked excitatory postsynaptic current amplitudes were significantly increased. These findings indicate that mild, repetitive blast exposures cause increases in neuronal excitability and seizures and eventual epilepsy development in some animals. The non-convulsive nature of the seizures suggests that subclinical seizures may occur in individuals experiencing even mild blast events, if repeated.

Concussion: A Global Perspective

Concussion, also referred to as mild traumatic brain injury (MTBI), is a common pediatric condition. This article reviews global perspectives on the epidemiology, treatment, and prognosis of concussion in children. A Pubmed search was conducted using Clinical Queries with the key terms "concussion" and "mild traumatic brain injury," and the search was limited to "children." The search strategy included meta-analyses, randomized controlled trials, clinical trials, and reviews. The majority of publications were from Canada and the United States. Prevalence estimates vary widely according to case definition and studied population. Due to under-reporting and to the widely varying definitions of concussion, it is difficult to estimate how common the condition is. Common causes of concussions include sports injuries, motor vehicle collisions, bicycle accidents, falls, and assaults. Diagnosis is mainly clinical. Because concussion results from a disturbance in brain function rather than structural injury, neuroimaging studies, such as computed tomography and magnetic resonance imaging, are not routinely recommended. Treatment generally involves physical and cognitive rest, with a gradual return to activities, whereas prolonged rest may actually worsen outcomes. Helmets when bicycling, skiing, snowboarding, motor biking, placing age limits on certain types of contact sports, and encouragement of fair play are recommended to decrease the impact of head injuries but they do not prevent concussions. Overall outcomes are generally favorable. The symptoms and signs of concussion usually resolve within 10 days; most patients recover in 48-72 hours. Global perspectives on management and prognosis are lacking. Concussions or MTBIs are common childhood injuries and the prognosis is good but information is predominantly from Canada and the USA. Research in other countries in particular low and middle income countries is vital to have a global perspective on MTBI.

Predictors of Collegiate Student-Athletes' Concussion-Related Knowledge and Behaviors

OBJECTIVE

This study aimed to explore student-athletes' concussion-related knowledge and attitudes toward reporting symptoms, demographic predictors of knowledge and attitudes, and determine whether responses to the survey changed following an online educational intervention.

METHODS

A total of 108 Division I student-athletes enrolled at a large southern university completed a survey evaluating knowledge regarding concussion-related terminology, symptoms and recovery trajectories, as well as attitudes toward reporting symptoms following a possible concussion. Student-athletes completed the questionnaire both 24-48 h before and one week after reviewing the educational presentation.

RESULTS

At baseline, participants correctly identified 72% of concussion symptoms included in the questionnaire, as well as correctly identified 75% of items related to the typical recovery trajectory post-concussion. A total of 54% of baseline attitudes toward reporting symptoms matched clinical best practices. Multiple analysis of variance (MANOVA) revealed that male sex and non-Caucasian race were associated with worse baseline knowledge of concussion symptoms. Concussion knowledge was not associated with attitudes toward reporting symptoms. Paired samples t-tests indicated that knowledge of concussion-related terminology improved modestly following the educational presentation.

CONCLUSIONS

Some subsets of collegiate student-athletes show relatively lower knowledge about symptoms of concussion than others. As a result, these groups may benefit from increased educational efforts to ensure they recognize when a concussion may have occurred. Additionally, as knowledge and attitudes were unrelated and the intervention had a modest effect on knowledge but not attitudes, future work should explore interventions that are designed to directly alter attitudes.

The use of an intensive physical exertion test as a final return to play measure in concussed athletes: a prospective cohort

OBJECTIVES

To examine the utility of a novel physical exertion test developed by the Chicago Blackhawks medical staff as a final return to play (RTP) clearance test in youth and young adult athletes, and to determine the relationship between participant and test variables on RTP within asymptomatic athletes diagnosed with concussion.

METHODS

Once asymptomatic and following completion of all RTP steps, concussed athletes underwent the Gapski-Goodman Test (GGT) or modified GGT (mGGT) at partnered Complete Concussion Management Inc. (CCMI) clinics as part of RTP decision-making. Prospective data was collected electronically by trained CCMI clinicians utilizing the CCMI Concussion Database System. A review was conducted to examine data collected between January 2016 and February 2017. Participant and test variables were analyzed to determine relationships with pass/fail rate of the GGT/mGGT.

RESULTS

A total of 759 athletes performed the GGT/mGGT in the study period. Although all asymptomatic, 14.6% of concussed athletes failed the GGT/mGGT while attempting to achieve RTP clearance. Statistically significant relationships were found between failure of the test and symptom severity score on initial presentation and self-reported history of pre-morbid anxiety. When taken together, sex, age, and pre-morbid anxiety significantly predicted the length of time between injury and RTP clearance.

CONCLUSION

The GGT may identify individuals who are not ready to RTP despite a self-reported asymptomatic status and completion of all RTP steps. These results illustrate that RTP clearance decisions based on self-reported asymptomatic status at rest may be inadequate. Instead, monitored, intensive, sport-specific, physical exertion testing should be utilized to inform clinical RTP decisions.

Fatal Second Impact Syndrome in Rowan Stringer, A 17-Year-Old Rugby Player

Second impact syndrome (SIS) is associated with malignant brain swelling and usually occurs in young athletes with one or more prior, recent concussions. SIS is rare and some dispute its existence. We report a case of SIS in Rowan Stringer, age 17, a rugby player who sustained a fatal brain injury despite prompt medical therapy including decompression surgery. The cause of the massive brain swelling was initially unknown. An inquest revealed Rowan’s text messages to friends describing symptoms from two prior, recent rugby brain injuries, likely concussions, within 5 days of the fatal blow and confirming the diagnosis of SIS.

Primary care management of concussion in Canada

Concussion has emerged as an important public health issue affecting thousands of Canadians annually. Health care providers including paediatricians, family and emergency medicine physicians, nurses, and nurse practitioners are commonly tasked with the responsibility of providing primary care to patients with acute concussion and those with persistent post-concussion symptoms. In July 2017, Parachute, in collaboration with the Public Health Agency of Canada and Sport Canada released the Canadian Guideline on Concussion in Sport that outlines a standardized and evidence-based approach to the recognition, diagnosis, and management of youth and adults with suspected concussion. In this report, we provide a brief overview of the important roles of primary care providers in the medical assessment, management, and prevention of concussion as outlined in this national best practice guideline.

Clinical features and early detection of sport-related concussion

Aim

Athletes who suffer sport‐related concussions but continue playing have a high probability of experiencing more severe symptoms with any subsequent concussion. This study used data from the authors’ clinical department to retrospectively investigate the clinical characteristics of sport‐related concussion and factors associated with delays in examinations.

Methods

The study included 38 patients with sport‐related concussions who were treated at the authors’ hospital. The sports during which the injuries occurred, occasions of injury, factors affecting the time from injury until examination at hospital, and prognoses were evaluated retrospectively.

Results

Sport‐related concussions most frequently occurred in rugby and judo, where tackling, throwing, and other types of physical contact can result in impacts to the head region at high angular or linear velocity with acceleration. Some subjects showed consciousness disturbance and/or clear subjective symptoms immediately after the injury and were therefore examined at the hospital rapidly. However, other subjects who suffered amnesia or less obvious symptoms continued to play after the injury and had delayed examinations. In addition, there was a tendency for examinations to be delayed when an on‐site physician was present.

Conclusions

In contact sports where injury‐resulting events occur, such as impacts to the head at high angular or linear velocity with acceleration, athletes should be immediately withdrawn from play and evaluated for concussion, even if there are no obvious head injuries or symptoms. The immediate ascertainment of symptoms after physical contact would improve the rapid detection of sport‐related concussion.

Comparison of branded rugby headguards on their effectiveness in reducing impact on the head

Aim

To compare the available brands of rugby headguards and evaluate their impact attenuation properties at various locations on the cranium, with regard to concussion prevention.

Methods

Seven different branded headguards were fitted onto a rigid headform and drop-tested in three different positions. An accelerometer measured the linear acceleration the headform experienced on impact with the ground. Each test involved dropping the headform from a height that generated 103.8 g on average when bare, which is the closest acceleration to the upper limit of the concussion threshold of 100 g. A mean peak acceleration for each drop position was calculated and compared with the bare baseline measurement.

Results

Each headguard demonstrated a significant decrease in the mean peak acceleration from the baseline value (all p≤0.01). Overall the Canterbury Ventilator was the most effective headguard, decreasing the impact force on average by 47%. The least effective was the XBlades Elite headguard, averaging a force reduction of 27%. In five of the seven headguards, the right side of the headwear was the most effective at reducing impact force.

Conclusion

Overall, the results indicate that it would be beneficial to wear a headguard during rugby in order to reduce the impact forces involved in head collisions. There was also a clear difference in performance between the tested brands, establishing the Canterbury headguard as the most effective. However, only one model of headguard from each brand was tested, so further research evaluating all other models should be considered.

Availability of Concussion Information in Spanish for Parents of Youth Athletes

All but one U.S. state has passed legislation requiring that concussion information be provided to parents of youth participants in school-sponsored sport. Such information should be accessible and easily understood if it is to be used by parents to make informed decisions regarding their children's health and safety. Accessing and understanding information about concussion may be challenging for parents who lack fluency in English. The current study sought to describe the extent and nature of Spanish-language concussion information available on the websites of U.S. public high school athletic associations. We also examined information provided by leading youth sports and health organizations as well as the top U.S. children's hospitals. We sought to quantify the proportion of these websites with Spanish-language translation of concussion education materials and describe the readability, accessibility, and completeness of these translations. Only one quarter of the websites examined contained any concussion information in Spanish, and none of these websites offered a mirrored Spanish-language translation. Spanish information was also difficult to access, with the search process requiring English-language ability. Finally, the readability of the concussion information in both English and Spanish was higher than recommended guidelines. Our findings suggest that non-English-speaking parents may be inadequately informed about concussion because translation of concussion educational materials is absent, incomplete, or hard to access. This raises questions about whether they are able to provide informed consent for their children's participation in contact sport and suggests the need for improved translation of such informational materials.

Concussion

Concussions are a common injury for which patients often present first to primary care physicians. They can affect the day-to-day function of patients in school and work, as well as in sports and recreational activities. Recognizing common physical signs and symptoms after injury facilitates timely diagnosis and treatment, permitting initiation of an active management approach to recovery while preventing secondary injury. For persons with persistent symptoms, active rehabilitation may be utilized, with the goal of returning patients to full function.

Knowledge, Attitudes and Concussion Information Sources Among First Nations in Ontario

OBJECTIVE

Hockey is a popular sport played by many First Nation youth. Concussion frequently goes unrecognized and unreported in youth hockey. Unintentional injuries among Indigenous youth occur at rates three to four times the national Canadian average. The study sought to examine knowledge, attitudes and sources of concussion information among First Nations people attending a provincial hockey tournament.

METHODS

A cross-sectional survey was undertaken. The survey by Mzazik et al. were modified to use in this study. Participants included youth (6-18 years) hockey players (n=75), parents (n=248) and coaches (n=68). The main outcome measure was total knowledge index (TKI) which consisted of the sum of correct responses to 15 multiple choice questions. Additional data gathered included demographics, concussion history, attitudes toward concussion and sources of information. Descriptive statistics included proportion comparisons. Variables were tested using χ 2 and analysis of variance.

RESULTS

Overall TKI scores (out of a total of 15) were low; players (5.9±2.8), parents (7.5±2.6) and coaches (7.9±2.6). Participants with higher knowledge scores reported more appreciation of the seriousness of concussion. Sources of information about concussion differed by study group, suggesting the need for multiple knowledge translation strategies to reach youth, parents and coaches.

CONCLUSIONS

Future initiatives are urgently needed to improve education and prevention of concussion in First Nations youth hockey. Collaborating and engaging with communities can help to ensure an Indigenous lens for culturally safe interventions.

Hyperthermia and Mild Traumatic Brain Injury: Effects on Inflammation and the Cerebral Vasculature

Mild traumatic brain injury (mTBI) or concussion represents the majority of brain trauma in the United States. The pathophysiology of mTBI is complex and may include both focal and diffuse injury patterns. In addition to altered circuit dysfunction and traumatic axonal injury (TAI), chronic neuroinflammation has also been implicated in the pathophysiology of mTBI. Recently, our laboratory has reported the detrimental effects of mild hyperthermic mTBI in terms of worsening histopathological and behavioral outcomes. To clarify the role of temperature-sensitive neuroinflammatory processes on these consequences, we evaluated the effects of elevated brain temperature (39°C) on altered microglia/macrophage phenotype patterns after mTBI, changes in leukocyte recruitment, and TAI. Sprague-Dawley male rats underwent mild parasagittal fluid-percussion injury under normothermic (37°C) or hyperthermic (39°C) conditions. Cortical and hippocampal regions were analyzed using several cellular and molecular outcome measures. At 24 h, the ratio of iNOS-positive (M1 type phenotype) to arginase-positive (M2 type phenotype) cells after hyperthermic mTBI showed an increase compared with normothermia by flow cytometry. Inflammatory response gene arrays also demonstrated a significant increase in several classes of pro-inflammatory genes with hyperthermia treatment over normothermia. The injury-induced expression of chemokine ligand 2 (Ccl2) and alpha-2-macroglobulin were also increased with hyperthermic mTBI. With western blot analysis, an increase in CD18 and intercellular cell adhesion molecule-1 (ICAM-1) with hyperthermia and a significant increase in Iba1 reactive microglia are reported in the cerebral cortex. Together, these results demonstrate significant differences in the cellular and molecular consequences of raised brain temperature at the time of mTBI. The observed polarization toward a M1-phenotype with mild hyperthermia would be expected to augment chronic inflammatory cascades, sustained functional deficits, and increased vulnerability to secondary insults. Mild elevations in brain temperature may contribute to the more severe and longer lasting consequences of mTBI or concussion reported in some patients.

An update on diagnostic and prognostic biomarkers for traumatic brain injury

INTRODUCTION

Traumatic brain injury (TBI) is a major worldwide neurological disorder of epidemic proportions. To date, there are still no FDA-approved therapies to treat any forms of TBI. Encouragingly, there are emerging data showing that biofluid-based TBI biomarker tests have the potential to diagnose the presence of TBI of different severities including concussion, and to predict outcome. Areas covered: The authors provide an update on the current knowledge of TBI biomarkers, including protein biomarkers for neuronal cell body injury (UCH-L1, NSE), astroglial injury (GFAP, S100B), neuronal cell death (αII-spectrin breakdown products), axonal injury (NF proteins), white matter injury (MBP), post-injury neurodegeneration (total Tau and phospho-Tau), post-injury autoimmune response (brain antigen-targeting autoantibodies), and other emerging non-protein biomarkers. The authors discuss biomarker evidence in TBI diagnosis, outcome prognosis and possible identification of post-TBI neurodegernative diseases (e.g. chronic traumatic encephalopathy and Alzheimer's disease), and as theranostic tools in pre-clinical and clinical settings. Expert commentary: A spectrum of biomarkers is now at or near the stage of formal clinical validation of their diagnostic and prognostic utilities in the management of TBI of varied severities including concussions. TBI biomarkers could serve as a theranostic tool in facilitating drug development and treatment monitoring.

Comparison of baseline ImPACT performance in amateur motocross riders to football and basketball athletes

PRIMARY OBJECTIVE

The American Motorcyclist Association requires professional riders to undergo baseline computerized neurocognitive testing (CNT) using the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) test for concussion management. It is recommended this practice be expanded to the amateur level, but limited research has explored whether baseline testing is necessary for youth when normative data is available. This study evaluates the utility of baseline testing for amateur riders by comparing their performance to those of traditional youth sports comprising normative datasets.

DESIGN/METHODS

An cross-sectional study comparing amateur motocross (N = 100) riders matched by age and sex to football (N = 100) and basketball (N = 100) athletes performance on baseline ImPACT testing.

RESULTS

ANCOVAs revealed a significant medium effect of group on measures of visual motor speed (F = 11.25, p < 0.001) and reaction time (F = 13.61, p < 0.001). Post hoc analyses revealed that motocross riders were significantly slower compared to football and basketball athletes. There were no significant differences (p > .05) between sport on measures of memory or symptoms.

CONCLUSIONS

Youth motocross riders performed significantly slower on speed measures compared to football and basketball athletes, providing preliminary support for the expansion of baseline ImPACT testing to the amateur level.

Do Neurocognitive SCAT3 Baseline Test Scores Differ Between Footballers (Soccer) Living With and Without Disability? A Cross-Sectional Study

OBJECTIVE

To determine if baseline Sport Concussion Assessment Tool, third Edition (SCAT3) scores differ between athletes with and without disability.

DESIGN

Cross-sectional comparison of preseason baseline SCAT3 scores for a range of England international footballers.

SETTING

Team doctors and physiotherapists supporting England football teams recorded players' SCAT 3 baseline tests from August 1, 2013 to July 31, 2014.

PARTICIPANTS

A convenience sample of 249 England footballers, of whom 185 were players without disability (male: 119; female: 66) and 64 were players with disability (male learning disability: 17; male cerebral palsy: 28; male blind: 10; female deaf: 9).

ASSESSMENT AND OUTCOME MEASURES

Between-group comparisons of median SCAT3 total and section scores were made using nonparametric Mann-Whitney-Wilcoxon ranked-sum test.

MAIN RESULTS

All footballers with disability scored higher symptom severity scores compared with male players without disability. Male footballers with learning disability demonstrated no significant difference in the total number of symptoms, but recorded significantly lower scores on immediate memory and delayed recall compared with male players without disability. Male blind footballers' scored significantly higher for total concentration and delayed recall, and male footballers with cerebral palsy scored significantly higher on balance testing and immediate memory, when compared with male players without disability. Female footballers with deafness scored significantly higher for total concentration and balance testing than female footballers without disability.

CONCLUSIONS

This study suggests that significant differences exist between SCAT3 baseline section scores for footballers with and without disability. Concussion consensus guidelines should recognize these differences and produce guidelines that are specific for the growing number of athletes living with disability.

Comparison of knowledge, perception and attitudes of concussion in previously concussed versus non-concussed youth soccer players

OBJECTIVES

To examine if history of concussion is correlated with a difference in knowledge, attitude, and perception of concussive injuries in youth soccer players.

METHODS

A convenience sample of youth soccer athletes aged 14 to 18 years completed a survey assessing prior history of concussive injury, knowledge of concussive injury, self-reporting attitudes, and perception of the injury. The survey consists of 16 knowledge questions (eleven on a scale of 1-2, and five on a scale of 1-4) and 12 attitude questions (seven on a scale of 1-4, and five on a scale of 1-5). The primary outcomes are the total scores calculated by summing the standardized raw scores for all knowledge questions and attitude questions, respectively. Linear regression was used to estimate the mean difference in the primary outcomes between previously concussed and non-concussed athletes (calculated as previously concussed - non-concussed).

RESULTS

Surveys were obtained from 90 athletes, with 32 (36%) previously sustaining at least one concussion. Thirty-one out of these 32 concussions were diagnosed by a medical provider. On average, the mean total raw scores of all knowledge questions are 34.6 (82.2% of 42 possible points) and 33.7 (80.2% of 42 total points) for previously concussed and non-concussed athletes, respectively, and the mean total raw scores of all attitude questions are 38.7 (72.9% of 53 possible points) and 39.6 (74.7% of 53 possible points), respectively. Mean differences estimated from univariate linear regression in the standardized total scores of knowledge questions and attitude questions are 1.56(95% confidence interval: -1.52-4.65) and -1.23 (%95 confidence interval: -4.64-2.19), respectively. Adjusting for age and years of playing soccer gave similar results.

CONCLUSION

Although we did not find significant differences between previously concussed and non-concussed athletes in either the knowledge or the attitude questions as measured by their total scores, this study showed a high level of awareness of concussion in youth soccer players, while still highlighting a need for education. Limited distinctions were made among subgroups of players, suggesting directions of future research in investigating the role that outside factors may have on knowledge and perception of concussion.

Concussion

Concussion has been recognized as a clinical entity for more than 1000 years. Throughout the 20th century it was studied extensively in boxers, but it did not pique the interest of the general population because it is the accepted goal of the boxer to inflict such an injury on their opponent. In 2002, however, the possibility that repetitive concussions could result in chronic brain damage and a progressive neurologic disorder was raised by a postmortem evaluation of a retired player in the most popular sports institution in the United States, the National Football League. Since that time concussion has been a frequent topic of conversation in homes, schools, and on television and has become a major focus of sports programs in communities and schools at all levels. Now all 50 states, the District of Columbia, and the National Collegiate Athletic Association have enacted laws and rules to protect the athlete.

Sports-related Concussion in Children and Adolescents

Concussions are becoming increasingly important to manage properly as sports participation continues to rise. Repeated injuries occurring before the brain has had a chance to recover from an initial insult are particularly dangerous and must be prevented. Although much national media attention has been devoted to concussions in professional sports, it is important to appreciate that athletes in any age group, children and adolescents in particular, are at risk of sports-related concussion. It is crucial to remove an athlete from play any time concussion is suspected. Once removed from play, recovery then begins with a period of cognitive and physical rest, followed by a gradual return to cognitive and athletic activities as symptoms resolve. Children and adolescents pose a unique challenge to the clinician managing their recovery, as the physical and cognitive rest periods required often involve time away from school and sports, which can be academically detrimental and socially isolating. Recently developed sideline assessment tools have greatly aided the urgent sideline assessment of an athlete suspected of having a concussion. In this article, a brief review of current guidelines is presented in tandem with the authors' preferred treatment of concussion.

Legal Aspects of Concussion: The Ever-Evolving Standard of Care

Today, when an athlete is catastrophically injured while playing a sport, litigation often follows. The likelihood of litigation is even greater in the event of a head injury, especially when the athlete can allege that a prior concussion somehow contributed to the current injury. Whether the potential defendants in these lawsuits, such as schools, coaches, athletic trainers, and other health care professionals, actually face legal liability depends on whether they are deemed to have conformed to the standard of care. The standard of care is a legal term, defined as acting as a reasonable professional in that position or industry would have under the circumstances based on then-existing knowledge. In this article, we examine the standard of care with regard to concussion management and treatment in the context of some of the most notable lawsuits in recent years.

Coaches’ Implementation of the USA Football “Heads Up Football” Educational Program

An integral part of the Heads Up Football (HUF) educational program is the Player Safety Coach (PSC), who is responsible for teaching other coaches within a youth football league about safer blocking/tackling and injury prevention. This study examines the association between youth football coaches’ interactions with the PSC (i.e., attending the PSC clinic at the beginning of the season and seeing the PSC on-field during practices) and their subsequent implementation of the HUF educational program. Data were collected via online questionnaire completed by 1,316 youth football coaches from HUF leagues. Data were analyzed with frequencies and logistic regression. Nearly half of coaches (44.8%) did not attend the PSC clinic; 25.9% reported not seeing their league’s PSC on the field on a regular basis. The lack of PSC on-site presence was significantly associated with worse implementation for “concussion recognition and response,” “heat preparedness and hydration,” and “sudden cardiac event preparedness.” PSC clinic attendance was not associated with implementation. Opportunities exist for improvement in the HUF educational program as there appears to be inconsistent implementation. Further research is warranted to understand how to optimize the role of the PSC in the youth sports context.

What Definition Is Used to Describe Second Impact Syndrome in Sports? A Systematic and Critical Review

Concern about what has been termed, "second impact syndrome" (SIS) is a major factor determining return-to-play decisions after concussion. However, definitions of SIS vary. We used Scopus to conduct a systematic review and categorize the definitions used to describe SIS. Of the 91 sources identified, 79 (87%) clearly specified that SIS involved either cerebral edema or death after a concussion when a prior concussion had not resolved. Twelve articles (13%) could be interpreted as merely the events of two consecutive concussions. Among the articles that listed mortality rates, nearly all (33/35, 94%) said the rate of death was "high" (e.g., 50% to 100%). Our review found that most articles define SIS as a syndrome requiring catastrophic brain injury after consecutive concussive episodes. Given that it is unclear how common it is to have a second concussion while not fully recovered from a first concussion, the actual mortality rate of SIS is unknown.