Consensus statement on concussion in sport: the 6th International Conference on Concussion in Sport-Amsterdam, October 2022.

For over two decades, the Concussion in Sport Group has held meetings and developed five international statements on concussion in sport. This 6th statement summarises the processes and outcomes of the 6th International Conference on Concussion in Sport held in Amsterdam on 27-30 October 2022 and should be read in conjunction with the (1) methodology paper that outlines the consensus process in detail and (2) 10 systematic reviews that informed the conference outcomes. Over 3½ years, author groups conducted systematic reviews of predetermined priority topics relevant to concussion in sport. The format of the conference, expert panel meetings and workshops to revise or develop new clinical assessment tools, as described in the methodology paper, evolved from previous consensus meetings with several new components. Apart from this consensus statement, the conference process yielded revised tools including the Concussion Recognition Tool-6 (CRT6) and Sport Concussion Assessment Tool-6 (SCAT6, Child SCAT6), as well as a new tool, the Sport Concussion Office Assessment Tool-6 (SCOAT6, Child SCOAT6). This consensus process also integrated new features including a focus on the para athlete, the athlete's perspective, concussion-specific medical ethics and matters related to both athlete retirement and the potential long-term effects of SRC, including neurodegenerative disease. This statement summarises evidence-informed principles of concussion prevention, assessment and management, and emphasises those areas requiring more research.

Prospective longitudinal investigation shows correlation of event-related potential to mild traumatic brain injury in adolescents.

STUDY DESIGN: Prospective longitudinal cohort study. BACKGROUND: Adolescent athletes may be more susceptible to the long-term effects of mild traumatic brain injury (mTBI). A diagnostic and prognostic neuromarker may optimize management and return-to-activity decision-making in athletes who experience mTBI. OBJECTIVE: Measure an event-related potential (ERP) component captured with electroencephalography (EEG), called processing negativity (PN), at baseline and post-injury in adolescents who suffered mTBI and determine their longitudinal response relative to healthy controls. METHODS: Thirty adolescents had EEG recorded during an auditory oddball task at a pre-mTBI baseline session and subsequent post-mTBI sessions. Longitudinal EEG data from patients and healthy controls (n= 77) were obtained from up to four sessions in total and processed using Brain Network Analysis algorithms. RESULTS: The average PN amplitude in healthy controls significantly decreased over sessions 2 and 3; however, it remained steady in the mTBI group's 2nd (post-mTBI) session and decreased only in sessions 3 and 4. Pre- to post-mTBI amplitude changes correlated with the time interval between sessions. CONCLUSION: These results demonstrate that PN amplitude changes may be associated with mTBI exposure and subsequent recovery in adolescent athletes. Further study of PN may lead to it becoming a neuromarker for mTBI prognosis and return-to-activity decision-making in adolescents.

Effect of Routine Sport Participation on Short-Term Clinical Neurological Outcomes: A Comparison of Non-Contact, Contact, and Collision Sport Athletes.

OBJECTIVES: To compare pre-season to post-season changes on a battery of clinical neurological outcome measures between non-contact, contact, and collision sport athletes over multiple seasons of play. METHODS: 244 high school and collegiate athletes participating in multiple non-contact, contact, and collision sports completed standardized annual pre-season and post-season assessments over 1-4 years. Pre/post-season changes in 10 outcome measures assessing concussion symptoms, neurocognitive performance, and balance were compared between the groups using linear mixed models. RESULTS: Small, but statistically significant overall pre/post-season change differences were present between the groups for Axon computerized neurocognitive test processing speed, attention, and working memory speed scores (Axon-PS, Axon-Att, Axon-WMS), as well as Balance Error Scoring System (BESS) total score. Small seasonal declines not exceeding reliable-change thresholds were observed in the collision sport group relative to the contact and non-contact groups for Axon-PS and Axon-Att scores. The collision and contact sport groups demonstrated less pre-/post-season improvement than the non-contact sport group for Axon-WMA and BESS, with less BESS improvement also observed in the collision sport group relative to the contact sport group. Overall, longitudinal performance on all 10 outcome measures remained stable in all 3 groups over 4 years. CONCLUSION: Our findings do not necessarily support the notion that participation in sports associated with exposure to repetitive head impacts has clinically meaningful cumulative effects over the course of a season, nor over four consecutive seasons in high school and collegiate athletes.

Comparing the Acute Presentation of Sport-Related Concussion in the Pediatric and Adult Populations.

Despite growing research on concussion, there is minimal evidence comparing the acute presentation of concussion between pediatric and adult patients. This cross-sectional study compares injury characteristics, symptoms, and neurologic examination in sport-related concussion based on age. Patients presenting to an outpatient sports neurology clinic for initial assessment of concussion within 7 days of injury were divided into 2 groups, 18 and older (n = 28) and 17 and younger (n = 107). There were no significant differences between pediatric and adult patients in any score of the Sport Concussion Assessment Tool-3rd Edition symptom scale, neurologic examination category, pertinent elements of past medical history, or characteristics of the concussion. The pediatric group had higher average hours of sleep (8.1 ± 0.3 vs 7.1 ± 0.58; P = .03) and were less likely to wake refreshed (36.3% vs 65%; P = .02). The initial presentation of concussion within 7 days of injury will likely not differ by age, specifically 18 and older versus 17 and younger.

The Concussion Recognition Tool 5th Edition (CRT5): Background and rationale.

The Concussion Recognition Tool 5 (CRT5) is the most recent revision of the Pocket Sport Concussion Assessment Tool 2 that was initially introduced by the Concussion in Sport Group in 2005. The CRT5 is designed to assist non-medically trained individuals to recognise the signs and symptoms of possible sport-related concussion and provides guidance for removing an athlete from play/sport and to seek medical attention. This paper presents the development of the CRT5 and highlights the differences between the CRT5 and prior versions of the instrument.

The Child Sport Concussion Assessment Tool 5th Edition (Child SCAT5): Background and rationale.

This article presents the Child Sport Concussion Assessment Tool 5th Edition (Child SCAT5). The Sport Concussion Assessment Tool was introduced in 2004, following the 2nd International Conference on Concussion in Sport in Prague, Czech Republic. Following the 4th International Consensus Conference, held in Zurich, Switzerland, in 2012, the SCAT 3rd edition (Child SCAT3) was developed for children aged between 5 and12 years. Research to date was reviewed and synthesised for the 5th International Consensus Conference on Concussion in Sport in Berlin, Germany, leading to the current revision of the test, the Child SCAT5. This article describes the development of the Child SCAT5.

The Sport Concussion Assessment Tool 5th Edition (SCAT5): Background and rationale.

This paper presents the Sport Concussion Assessment Tool 5th Edition (SCAT5), which is the most recent revision of a sport concussion evaluation tool for use by healthcare professionals in the acute evaluation of suspected concussion. The revision of the SCAT3 (first published in 2013) culminated in the SCAT5. The revision was based on a systematic review and synthesis of current research, public input and expert panel review as part of the 5th International Consensus Conference on Concussion in Sport held in Berlin in 2016. The SCAT5 is intended for use in those who are 13 years of age or older. The Child SCAT5 is a tool for those aged 5-12 years, which is discussed elsewhere.

What are the critical elements of sideline screening that can be used to establish the diagnosis of concussion? A systematic review.

BACKGROUND: Sideline detection is the first and most significant step in recognising a potential concussion and removing an athlete from harm. This systematic review aims to evaluate the critical elements aiding sideline recognition of potential concussions including screening tools, technologies and integrated assessment protocols. DATA SOURCES: Bibliographic databases, grey literature repositories and relevant websites were searched from 1 January 2000 to 30 September 2016. A total of 3562 articles were identified. STUDY SELECTION: Original research studies evaluating a sideline tool, technology or protocol for sports-related concussion were eligible, of which 27 studies were included. DATA EXTRACTION: A standardised form was used to record information. The QUADAS-2 and Newcastle-Ottawa tools were used to rate risk of bias. Strength of evidence was assessed using the Grades of Recommendation, Assessment, Development and Evaluation Working Group system. DATA SYNTHESIS: Studies assessing symptoms, the King-Devick test and multimodal assessments reported high sensitivity and specificity. Evaluations of balance and cognitive tests described lower sensitivity but higher specificity. However, these studies were at high risk of bias and the overall strength of evidence examining sideline screening tools was very low. A strong body of evidence demonstrated that head impact sensors did not provide useful sideline concussion information. Low-strength evidence suggested a multimodal, multitime-based concussion evaluation process incorporating video review was important in the recognition of significant head impact events and delayed onset concussion. CONCLUSION: In the absence of definitive evidence confirming the diagnostic accuracy of sideline screening tests, consensus-derived multimodal assessment tools, such as the Sports Concussion Assessment Tool, are recommended. Sideline video review may improve recognition and removal from play of athletes who have sustained significant head impact events. Current evidence does not support the use of impact sensor systems for real-time concussion identification.

Effect of Concussion on Performance of National Football League Players.

PURPOSE: Lingering neurologic injury after concussion may expose athletes to increased risk if return to play is premature. The authors explored whether on-field performance after concussion is a marker of lingering neurologic injury. DESIGN: Retrospective cohort study on 1882 skill-position players who played in the National Football League (NFL) during 2007-2010. METHODS: Players with concussion based on the weekly injury report were compared with players with other head and neck injuries (controls) on measures of on-field performance using Football Outsiders' calculation of defense-adjusted yards above replacement (DYAR), a measure of a player's contribution controlling for game context. Changes in performance, relative to a player's baseline level of performance, were estimated before and after injury using fixed-effects models. RESULTS: The study included 140 concussed players and 57 controls. Players with concussion performed no better or worse than their baseline on return to play. However, a decline in DYAR relative to their prior performance was noted 2 wk and 1 wk before appearing on the injury report. Concussed players performed slightly better than controls in situations where they returned to play the same week as appearing on the injury report. CONCLUSIONS: On return, concussed NFL players performed at their baseline level of performance, suggesting that players have recovered from concussion. Decline in performance noted 2 wk and 1 wk before appearing on the injury report may suggest that concussion diagnosis was delayed or that concussion can be a multihit phenomenon. Athletic performance may be a novel tool for assessing concussion injury and recovery.

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.

A Clinical Approach to the Diagnosis of Traumatic Encephalopathy Syndrome: A Review.

IMPORTANCE: Chronic traumatic encephalopathy (CTE) refers to pathologic changes that have been found in some individuals with a history of repetitive traumatic impact to the head (hereinafter referred to as head trauma). These changes cannot be assessed during the clinical evaluation of a living patient. OBSERVATIONS: The neuropathologic features, taxonomy, history, role of biomarkers in diagnosis, and existing criteria of CTE are reviewed. Previous criteria have been proposed to approach the living patient; however, a unified, specific approach is needed for the practicing clinician. We propose a new diagnostic construct for the clinical syndrome associated with repetitive exposure to head trauma: traumatic encephalopathy syndrome. This clinical paradigm will provide the framework for a diagnosis of probable, possible, and unlikely traumatic encephalopathy syndrome, with included discussion regarding the minimum exposure, nature of the clinical course, and additional clinical features needed for diagnosis. CONCLUSIONS AND RELEVANCE: While prospective longitudinal studies are ongoing to further elucidate the association of exposure to head trauma, clinical features, and the development of pathologic changes, a corresponding clinical construct for diagnosis is necessary.

Summary of the 2015 University of Michigan Sport Concussion Summit.

Discussions surrounding concussion have made their way into the public sphere over the previous decade with media attention and coverage of the injury fueling public debate. These conversations have devolved into discussions on banning contact and collision sports and raised legal questions surrounding injury management. Questions raised about concussion eclipse what science can answer, but the University of Michigan Injury Center (MI, USA) hosted a Concussion Summit in September 2015 as a means to condense, solidify and disseminate what is currently known on the topic. Areas for discussion included concussion incidence and prevention, diagnosis and management, legislation and education, legal and social aspects and future directions. A summary of those presentations are included within.

The Acute Management of Sport Concussion in Pediatric Athletes.

During the past two decades the focus on sport concussion has increased significantly. Young athletes represent the most vulnerable population to sustain a sport concussion yet receive the least amount of attention. Specifically, young athletes who sustain a sport concussion can go unrecognized and continue to participate in sport putting them at an increased risk for a more significant injury. The purpose of this review is to provide a clinical framework for the evaluation and management of sport concussion. In addition, this review provides considerations for health care professionals in regard to clinical measures and follow-up strategies during the acute phase following concussion in young concussed athletes following injury.

Developing guidelines for return to play: consensus and evidence-based approaches.

BACKGROUND: Sports-related concussions are commonplace at all levels of play and across all age groups. The dynamic, evolving nature of this injury coupled with a lack of objective biomarkers creates a challenging management issue for the sports medicine team. Athletes who return to play following a concussion are known to be at higher risk for an additional brain injury, which necessitates a careful, informed return to play (RTP) process. AIM: The goal of this paper is to outline historical attempts at developing RTP guidelines and trace their evolution over time, culminating in a discussion of the process and outcomes of the most recent consensus statements/guidelines published by the international Concussion In Sport Group (CISG), the American Academy of Neurology (AAN), the National Athletic Trainers' Association, and the 2013 Team Physician Consensus Statement Update. METHOD: An evaluation of the pros and cons of these guidelines is presented along with suggestions for future directions. In addition, the Institute of Medicine recently conducted a comprehensive report outlining the current state of evidence regarding youth concussions, which provides specific recommendations for future research. CONCLUSIONS: The different methodologies utilized in the development of consensus statements have distinct advantages and disadvantages, and both approaches add value to the everyday management of sports concussions. Importantly, the overall approach for management of sports concussion is remarkably similar using either consensus-based or formal evidence-based methods, which adds confidence to the current guidelines and allows practitioners to focus on accepted standards of clinical care. Moving forward, careful study designs need to be utilized to avoid bias in selection of research subjects, collection of data, and interpretation of results. Although useful, clinicians must venture beyond consensus statements to examine reviews of the literature that are published in much greater frequency than consensus statements.

Analyzing the effect of state legislation on health care utilization for children with concussion.

IMPORTANCE: In 2009, Washington State enacted legislation outlining the medical care of children and adolescents with concussion (ie, the Lystedt Law), with all other states and Washington, DC passing legislation by January 2014. OBJECTIVE: To evaluate the effect of concussion laws on health care utilization rates from January 1, 2006, through June 30, 2012, in states with and without legislation. DESIGN, SETTING, AND PARTICIPANTS: For commercially insured children aged 12 to 18 years from all 50 states and DC from January 1, 2006, through June 30, 2009, we examined the following: (1) prelegislation trends in concussion-related health care utilization from January 1, 2006, through June 30, 2009, (2) postlegislation trends in states without concussion legislation, and (3) the effect of state concussion laws on trends in states with concussion legislation in effect by means of negative binomial multivariable estimation with state and time fixed effects. EXPOSURES: Concussion diagnosis. MAIN OUTCOMES AND MEASURES: Emergency department and related health care utilization rates for concussion. RESULTS: Between academic school years 2008-2009 and 2011-2012, states with legislation experienced a 92% increase in concussion-related health care utilization, while states without legislation had a 75% overall increase in concussion-related health care utilization during the same period. In the multivariable fixed-effects models, controlling for differences across states, rates of treated concussion in states without legislation were 7% higher in the 2009-2010 school year, 20% higher in the 2010-2011 school year, and 34% higher in the 2011-2012 school year compared with the prelegislation trends (2005-2009) (all P < .01). During the same period, states with concussion laws demonstrated a 10% higher concussion-related health care utilization rate compared with states without laws (P < .01). CONCLUSIONS AND RELEVANCE: Increased health care utilization rates among children with concussion in the United States are both directly and indirectly related to concussion legislation. A portion of the increased rates (60%) in states without legislation is attributable to an ongoing upward trend demonstrated before enactment of the first state law in 2009. The remaining 40% increase in these states is thought to have resulted from elevated awareness brought about by heightened local and national media attention. Concussion legislation has had a seemingly positive effect on health care utilization, but the overall increase can also be attributed to increased injury awareness.

An introduction to sports concussions.

PURPOSE OF REVIEW: Concussions are a major public health issue, and particularly so in the setting of sports. Millions of athletes of all ages may face the risks of concussion and repeat concussion. This article introduces the terminology, epidemiology, and underlying pathophysiology associated with concussion, focused on sports-related injuries. RECENT FINDINGS: Concussion is a clinical syndrome of symptoms and signs occurring after biomechanical force is imparted to the brain. Because of the subjective nature of symptom reporting, definitions of concussion differ slightly in different guidelines. Concussion nomenclature also includes mild traumatic brain injury, postconcussion symptoms, postconcussion syndrome, chronic neurocognitive impairment, subconcussive injury, and chronic traumatic encephalopathy. Between 1.6 and 3.8 million sports-related concussions are estimated in the United States annually, particularly in youth athletes. Rates of concussion are higher in sports such as football, rugby, ice hockey, and wrestling in males, and soccer and basketball in females. The underlying pathophysiology of concussion centers on membrane leakage, ionic flux, indiscriminate glutamate release, and energy crisis. These initial events then trigger ongoing metabolic impairment, vulnerability to second injury, altered neural activation, and axonal dysfunction. While the linkage between acute neurobiology and chronic deficits remains to be elucidated, activation of cell death pathways, ongoing inflammation, persistent metabolic problems, and accumulation of abnormal or toxic proteins have all been implicated. SUMMARY: Concussion is a biomechanically induced syndrome of neural dysfunction. Millions of concussions occur annually, many of them related to sports. Biologically, a complex sequence of events occurs from initial ionic flux, glutamate release, and axonal damage, resulting in vulnerability to second injury and possibly to longer-term neurodegeneration.