Consensus Statement on Concussion in Sport: The 4th International Conference on Concussion in Sport, Zurich, November 2012

This paper is a revision and update of the recommendations developed following the 1st (Vienna 2001), 2nd (Prague 2004), and 3rd (Zurich 2008) International Consensus Conference on Concussion in Sport and is based on the deliberations at the 4th International Conference on Concussion in Sport held in Zurich, November 2012.^1–3 

The new 2012 Zurich Consensus statement is designed to build on the principles outlined in the previous documents and to develop further conceptual understanding of this problem using a formal consensus-based approach. A detailed description of the consensus process is outlined at the end of this document under the “Background” section. This document is developed for use by physicians and health care professionals who are primarily involved in the care of injured athletes, whether at the recreational, elite, or professional level.

While agreement exists pertaining to principle messages conveyed within this document, the authors acknowledge that the science of concussion is evolving, and therefore, management and RTP decisions remain in the realm of clinical judgment on an individualized basis. Readers are encouraged to copy and distribute freely the Zurich Consensus document, the Pocket Concussion Recognition Tool (CRT), the Sports Concussion Assessment Tool version 3 (SCAT3), and the Child SCAT3 card (Appendix), and none is subject to any restriction, provided it is not altered in any way or converted to a digital format. The authors request that the document and the accompanying tools be distributed in their full and complete format.

This consensus paper is broken into a number of sections:

• A summary of concussion and its management, with updates from the previous meetings;

• Background information about the consensus meeting process;

• A summary of the specific consensus questions discussed at this meeting; and

• The Consensus paper should be read in conjunction with the SCAT3 assessment tool, the Child SCAT3, and the Concussion Recognition Tool (designed for lay use).

The Zurich 2012 document examines sport concussion and management issues raised in the previous Vienna 2001, Prague 2004, and Zurich 2008 documents and applies the consensus questions from Section 3 to these areas.^1–3 

Panel discussion regarding the definition of concussion and its separation from mild traumatic brain injury (mTBI) was held. There was acknowledgement by the Concussion in Sport Group (CISG) that, although the terms mild traumatic brain injury (mTBI) and concussion are often used interchangeably in the sporting context and particularly in the US literature, others use the term to refer to different injury constructs. Concussion is the historical term representing low-velocity injuries that cause brain “shaking,” resulting in clinical symptoms, and which are not necessarily related to a pathologic injury. Concussion is a subset of TBI, and the term concussion will be used in this document. It was also noted that the term commotio cerebri is often used in European and other countries. Minor revisions were made to the definition of concussion and it is defined as follows: Concussion is a brain injury and is defined as a complex pathophysiological process affecting the brain, induced by biomechanical forces. Several common features that incorporate clinical, pathologic, and biomechanical injury constructs that may be utilized in defining the nature of a concussive head injury include:

1. 1.

   Concussion may be caused by a direct blow to the head, face, neck, or elsewhere on the body with an “impulsive” force transmitted to the head.

2. 2.

   Concussion typically results in the rapid onset of short-lived impairment of neurologic function that resolves spontaneously. However, in some cases, symptoms and signs may evolve over a number of minutes to hours.

3. 3.

   Concussion may result in neuropathologic changes, but the acute clinical symptoms largely reflect a functional disturbance rather than a structural injury, and as such, no abnormality is seen on standard structural neuroimaging studies.

4. 4.

   Concussion results in a graded set of clinical symptoms that may or may not involve loss of consciousness. Resolution of the clinical and cognitive symptoms typically follows a sequential course. However, it is important to note that in some cases symptoms may be prolonged.

The majority (80% to 90%) of concussions resolve in a short (7–10 day) period, although the recovery timeframe may be longer in children and adolescents.² 

The diagnosis of acute concussion usually involves the assessment of a range of domains including clinical symptoms, physical signs, cognitive impairment, neurobehavioral features, and sleep disturbance. Furthermore, a detailed concussion history is an important part of the evaluation, both in the injured athlete and when conducting a preparticipation examination. The detailed clinical assessment of concussion is outlined in the SCAT3 and Child SCAT3 forms, which are appendices to this document.

The suspected diagnosis of concussion can include 1 or more of the following clinical domains:

• Symptoms: somatic (eg, headache), cognitive (eg, feeling like in a fog), and/or emotional symptoms (eg, lability);

• Physical signs (eg, loss of consciousness, amnesia);

• Behavioral changes (eg, irritability);

• Cognitive impairment (eg, slowed reaction times); and/or

• Sleep disturbance (eg, insomnia).

If any 1 or more of these components is present, a concussion should be suspected and the appropriate management strategy instituted.

When a player shows any features of a concussion:

• The player should be evaluated by a physician or other licensed health care provider on site using standard emergency management principles, and particular attention should be given to excluding a cervical spine injury.

• The appropriate disposition of the player must be determined by the treating health care provider in a timely manner. If no health care provider is available, the player should be safely removed from practice or play and urgent referral to a physician arranged.

• Once the first-aid issues are addressed, then an assessment of the concussive injury should be made using the SCAT3 or other sideline assessment tools.

• The player should not be left alone after the injury, and serial monitoring for deterioration is essential over the initial few hours after injury.

• A player with a diagnosed concussion should not be allowed to return to play (RTP) on the day of injury.

Sufficient time for assessment and adequate facilities should be provided for the appropriate medical assessment, both on and off the field, for all injured athletes. In some sports, this may require rule change to allow an appropriate off-field medical assessment to occur without affecting the flow of the game or unduly penalizing the injured player's team. The final determination regarding concussion diagnosis and fitness to play is a medical decision based on clinical judgment.

Sideline evaluation of cognitive function is an essential component in the assessment of this injury. Brief neuropsychological test batteries that assess attention and memory function have been shown to be practical and effective. Such tests include the SCAT3, which incorporates the Maddocks questions,^4,5  and the Standardized Assessment of Concussion (SAC).^6–8  It is worth noting that standard orientation questions (eg, time, place, person) have been shown to be unreliable in the sporting situation when compared with memory assessment.^5,9  It is recognized, however, that abbreviated testing paradigms are designed for rapid concussion screening on the sidelines and are not meant to replace comprehensive neuropsychological testing, which should ideally be performed by trained neuropsychologists who are sensitive to subtle deficits that may exist beyond the acute episode; nor should they be used as a standalone tool for the ongoing management of sports concussions.

It should also be recognized that the appearance of symptoms or cognitive deficit might be delayed several hours after a concussive episode and that concussion should be seen as an evolving injury in the acute stage.

An athlete with concussion may be evaluated in the emergency room or doctor's office as a point of first contact after injury or may have been referred from another care provider. In addition to the points outlined above, the key features of this exam should encompass:

• A medical assessment, including a comprehensive history and detailed neurological examination with a thorough assessment of mental status, cognitive functioning, gait, and balance.

• A determination of the clinical status of the patient, including whether there has been improvement or deterioration since the time of injury. This may involve seeking additional information from parents, coaches, teammates, and eyewitnesses to the injury.

• A determination of the need for emergent neuroimaging in order to exclude a more severe brain injury involving a structural abnormality.

In large part, the points above are included in the SCAT3 assessment.

A range of additional investigations may be used to assist in the diagnosis or exclusion of injury. Conventional structural neuroimaging is typically normal in concussive injury. Given that caveat, the following suggestions are made. Brain computed tomography (CT; or where available, magnetic resonance imaging [MRI]) contributes little to concussion evaluation but should be employed whenever suspicion of an intracerebral or structural lesion (eg, skull fracture) exists. Examples of such situations may include prolonged disturbance of conscious state, focal neurological deficit, or worsening symptoms.

Other imaging modalities, such as functional MRI (fMRI) demonstrate activation patterns that correlate with symptom severity and recovery in concussion.^10–14  While not part of routine assessment at the present time, they nevertheless provide additional insight to pathophysiologic mechanisms. Alternative imaging technologies (eg, positron emission tomography, diffusion tensor imaging, magnetic resonance spectroscopy, functional connectivity), while demonstrating some compelling findings, are still at early stages of development and cannot be recommended other than in a research setting.

Published studies, using both sophisticated force-plate technology, as well as those using less sophisticated clinical balance tests (eg, Balance Error Scoring System), have identified acute postural stability deficits lasting approximately 72 hours after sport-related concussion. It appears that postural-stability testing provides a useful tool for objectively assessing the motor domain of neurologic functioning and should be considered a reliable and valid addition to the assessment of athletes suffering from concussion, particularly where symptoms or signs indicate a balance component.^15–21 

The significance of apolipoprotein (Apo) E4, ApoE promotor gene, tau polymerase, and other genetic markers in the management of sports concussion risk or injury outcome is unclear at this time.^22,23  Evidence from human and animal studies in more severe traumatic brain injury demonstrates induction of a variety of genetic and cytokine factors, such as insulin-like growth factor-1 (IGF-1), IGF binding protein-2, fibroblast growth factor, Cu-Zn superoxide dismutase, superoxide dismutase-1 (SOD-1), nerve growth factor, glial fibrillary acidic protein (GFAP), and S-100. How such factors are affected in sporting concussion is not known at this stage.^24–31  In addition, biochemical serum and cerebrospinal fluid biomarkers of brain injury (including S-100, neuron specific enolase [NSE], myelin basic protein [MBP], GFAP, tau, etc) have been proposed as means by which cellular damage may be detected if present.^32–38  There is currently insufficient evidence, however, to justify the routine use of these biomarkers clinically.

Different electrophysiologic recording techniques (eg, evoked response potential, cortical magnetic stimulation, and electroencephalography) have demonstrated reproducible abnormalities in the postconcussive state; however, not all studies reliably differentiated concussed athletes from controls.^39–45  The clinical significance of these changes remains to be established.

The application of neuropsychological (NP) testing in concussion has been shown to be of clinical value and contributes significant information in concussion evaluation.^46–51  Although in most cases, cognitive recovery largely overlaps with the time course of symptom recovery, it has been demonstrated that cognitive recovery may occasionally precede or more commonly follow clinical symptom resolution, suggesting that the assessment of cognitive function should be an important component in the overall assessment of concussion and, in particular, any RTP protocol.^52,53  It must be emphasized, however, that NP assessment should not be the sole basis of management decisions. Rather, it should be seen as an aid to the clinical decision-making process in conjunction with a range of assessments of different clinical domains and investigational results.

It is recommended that all athletes should have a clinical neurological assessment (including assessment of their cognitive function) as part of their overall management. This will normally be done by the treating physician, often in conjunction with computerized NP screening tools.

Formal NP testing is not required for all athletes; however, when this is considered necessary, then it should ideally be performed by a trained neuropsychologist. Although neuropsychologists are in the best position to interpret NP tests by virtue of their background and training, the ultimate RTP decision should remain a medical one in which a multidisciplinary approach, when possible, has been taken. In the absence of NP and other (eg, formal balance assessment) testing, a more conservative RTP approach may be appropriate.

Neuropsychological testing may be used to assist RTP decisions and is typically performed when an athlete is clinically asymptomatic. However, NP assessment may add important information in the early stages after injury.^54,55  There may be particular situations where testing is performed early to assist in determining aspects of management (eg, return to school in a pediatric athlete). This will normally be best determined in consultation with a trained neuropsychologist.^56,57 

Baseline NP testing was considered by the panel and was not felt to be required as a mandatory aspect of every assessment. However, it may be helpful or add useful information to the overall interpretation of these tests. It also provides an additional educative opportunity for the physician to discuss the significance of this injury with the athlete. At present, there is insufficient evidence to recommend the widespread routine use of baseline NP testing.

The cornerstone of concussion management is physical and cognitive rest until the acute symptoms resolve and then a graded program of exertion before medical clearance and RTP. The current published evidence evaluating the effect of rest after a sport-related concussion is sparse. An initial period of rest in the acute symptomatic period after injury (24–48 hours) may be of benefit. Further research to evaluate the long-term outcome of rest and the optimal amount and type of rest is needed. In the absence of evidence-based recommendations, a sensible approach involves the gradual return to school and social activities (before contact sports) in a manner that does not result in a significant exacerbation of symptoms.

Low-level exercise for those who are slow to recover may be of benefit, although the optimal timing after injury for initiation of this treatment is currently unknown.

As described above, the majority of injuries will recover spontaneously over several days. In these situations, it is expected that an athlete will proceed progressively through a stepwise RTP strategy.⁵⁸ 

The RTP protocol after a concussion follows a stepwise process as outlined in Table 1.

With this stepwise progression, the athlete should continue to proceed to the next level if asymptomatic at the current level. Generally, each step should take 24 hours, so that an athlete would take approximately 1 week to proceed through the full rehabilitation protocol once asymptomatic at rest and with provocative exercise. If any postconcussion symptoms occur while in the stepwise program, then the patient should drop back to the previous asymptomatic level and try to progress again after a further 24-hour period of rest has passed.

It was unanimously agreed that no RTP on the day of concussive injury should occur. There are data demonstrating that, at the collegiate and high school level, athletes allowed to RTP on the same day may demonstrate NP deficits postinjury that may not be evident on the sidelines and are more likely to have delayed onset of symptoms.^59–65 

Persistent symptoms (>10 days) are reported in 10%–15% of concussions. In general, symptoms are not specific to concussion, and it is important to consider other conditions. Cases of concussion in sport where clinical recovery falls outside the expected window (ie, 10 days) should be managed in a multidisciplinary manner by health care providers with experience in sports-related concussion.

Psychological approaches may have potential application in this injury, particularly with the modifiers listed below.^66,67  Physicians are also encouraged to evaluate the concussed athlete for affective symptoms such as depression and anxiety, as these symptoms are common in all forms of traumatic brain injury.⁵⁸ 

Pharmacologic therapy in sports concussion may be applied in 2 distinct situations. The first of these situations is the management of specific or prolonged symptoms (eg, sleep disturbance, anxiety). The second situation is where drug therapy is used to modify the underlying pathophysiology of the condition with the aim of shortening the duration of the concussion symptoms.⁶⁸  In broad terms, this approach to management should be considered only by clinicians experienced in concussion management.

An important consideration in RTP is that concussed athletes should not only be symptom free but also should not be taking any pharmacologic agents or medications that may mask or modify the symptoms of concussion. Where antidepressant therapy may be commenced during the management of a concussion, the decision to RTP while still on such medication must be considered carefully by the treating clinician.

Recognizing the importance of a concussion history and appreciating the fact that many athletes will not recognize all the concussions they may have suffered in the past, a detailed concussion history is of value.^69–72  Such a history may pre-identify athletes who fit into a high- risk category and provides an opportunity for the health care provider to educate the athlete in regard to the significance of concussive injury. A structured concussion history should include specific questions as to previous symptoms of a concussion and length of recovery, not just the perceived number of past concussions. It is also worth noting that dependence upon the recall of concussive injuries by teammates or coaches has been demonstrated to be unreliable.⁶⁹  The clinical history should also include information about all previous head, face, and cervical spine injuries, as these may also have clinical relevance. It is worth emphasizing that in the setting of maxillofacial and cervical spine injuries, coexistent concussive injuries may be missed unless specifically assessed. Questions pertaining to disproportionate effect versus symptom-severity matching may alert the clinician to a progressively increasing vulnerability to injury. As part of the clinical history, it is advised that details regarding protective equipment employed at time of injury be sought, both for recent and remote injuries.

There is an additional and often unrecognized benefit of the preparticipation physical examination insofar as the evaluation allows for an educative opportunity with the player concerned as well as consideration of modification of playing behavior if required.

A range of modifying factors may influence the investigation and management of concussion and, in some cases, may predict the potential for prolonged or persistent symptoms. However, in some cases, the evidence for their efficacy is limited. These modifiers would be important to consider in a detailed concussion history and are outlined in Table 2.

The role of female sex as a possible modifier in the management of concussion was discussed at length by the panel. There was not unanimous agreement that the current published research evidence is conclusive enough for this to be included as a modifying factor, although it was accepted that sex may be a risk factor for injury or influence injury severity (or both).^73–75 

In the overall management of moderate to severe traumatic brain injury, duration of loss of consciousness (LOC) is an acknowledged predictor of outcome.⁷⁶  While published findings in concussion describe LOC associated with specific early cognitive deficits, it has not been noted as a measure of injury severity.^77,78  Consensus discussion determined that prolonged (>1-minute duration) LOC would be considered as a factor that may modify management.

There is renewed interest in the role of posttraumatic amnesia and its role as a surrogate measure of injury severity.^64,79,80  Published evidence suggests that the nature, burden, and duration of the clinical postconcussive symptoms may be more important than the presence or duration of amnesia alone.^77,81,82  Further, it must be noted that retrograde amnesia varies with the time of measurement postinjury and hence is poorly reflective of injury severity.^83,84 

A variety of immediate motor phenomena (eg, tonic posturing) or convulsive movements may accompany a concussion. Although dramatic, these clinical features are generally benign and require no specific management beyond the standard treatment of the underlying concussive injury.^85,86 

Mental health issues (such as depression) have been reported as a consequence of all levels of traumatic brain injury, including sports-related concussion. Neuroimaging studies using fMRI suggest that a depressed mood after concussion may reflect an underlying pathophysiological abnormality consistent with a limbic-frontal model of depression.^34,87–97  While such mental health issues may be multifactorial in nature, it is recommended that the treating physician consider these issues in the management of concussed patients.

The evaluation and management recommendations contained herein can be applied to children and adolescents down to the age of 13 years. Below that age, children report concussion symptoms different from adults and would require age-appropriate symptom checklists as a component of assessment. An additional consideration in assessing the child or adolescent athlete with a concussion is that the clinical evaluation by the health care professional may need to include both patient and parent input and possibly teacher and school input when appropriate.^98–104  A child SCAT3 has been developed to assess concussion (see Appendix) for those aged 5–12 years.

The decision to use NP testing is broadly the same as the adult assessment paradigm, although there are some differences. Timing of testing may differ in order to assist planning in school and home management. If cognitive testing is performed, then it must be developmentally sensitive until late teen years due to the ongoing cognitive maturation that occurs during this period which, in turn, makes the utility of comparison to either the person's own baseline performance or to population norms limited.²⁰  In this age group, it is more important to consider the use of trained pediatric neuropsychologists to interpret assessment data, particularly in children with learning disorders or attention-deficit hyperactivity disorder, who may need more sophisticated assessment strategies.^56,57,98 

It was agreed by the panel that no return to sport or activity should occur before the child or adolescent athlete has managed to return to school successfully. In addition, the concept of “cognitive rest” was highlighted, with special reference to a child's need to limit exertion with activities of daily living that may exacerbate symptoms. School attendance and activities may also need to be modified to avoid provocation of symptoms. Children should not be returned to sport until clinically completely symptom free, which may require a longer timeframe than for adults.

Because of the different physiological response and longer recovery after concussion and specific risks (eg, diffuse cerebral swelling) related to head impact during childhood and adolescence, a more conservative RTP approach is recommended. It is appropriate to extend the amount of time of asymptomatic rest or the length of the graded exertion in children and adolescents. It is not appropriate for a child or adolescent athlete with concussion to RTP on the same day as the injury, regardless of the level of athletic performance. Concussion modifiers apply even more to this population than adults and may mandate more cautious RTP advice.

All athletes, regardless of level of participation, should be managed using the same treatment and RTP paradigm. The available resources and expertise in concussion evaluation are of more importance in determining management than a separation between elite and nonelite athlete management. Although formal NP testing may be beyond the resources of many sports or individuals, it is recommended that, in all organized high-risk sports, consideration be given to having this cognitive evaluation, regardless of the age or level of performance.

Clinicians need to be mindful of the potential for long-term problems in the management of all athletes. However, it was agreed that chronic traumatic encephalopathy (CTE) represents a distinct tauopathy with an unknown incidence in athletic populations. It was further agreed that a cause-and-effect relationship has not yet been demonstrated between CTE and concussions or exposure to contact sports.^105–114  At present, the interpretation of causation in the modern CTE case studies should proceed cautiously. It was also recognized that it is important to address the fears of parents and athletes from media pressure related to the possibility of CTE.

There is no good clinical evidence that currently available protective equipment will prevent concussion, although mouthguards have a definite role in preventing dental and orofacial injury. Biomechanical studies have shown a reduction in impact forces to the brain with the use of head gear and helmets, but these findings have not been translated to show a reduction in concussion incidence. For skiing and snowboarding, there are a number of studies to suggest that helmets provide protection against head and facial injury and hence should be recommended for participants in alpine sports.^115–118  In specific sports, such as cycling and motor and equestrian sports, protective helmets may prevent other forms of head injury (eg, skull fracture) that are related to falling on hard surfaces and may be an important injury-prevention issue for those sports.^118–130 

Consideration of rule changes to reduce the head injury incidence or severity may be appropriate where a clear-cut mechanism is implicated in a particular sport. An example of this is in football (soccer), where research studies demonstrated that upper limb-to-head contact in heading contests accounted for approximately 50% of concussions.¹³¹  As noted earlier, rule changes also may be needed in some sports to allow an effective off-field medical assessment to occur without compromising the athlete's welfare, affecting the flow of the game, or unduly penalizing the player's team. It is important to note that rule enforcement may be a critical aspect of modifying injury risk in these settings, and referees play an important role in this regard.

An important consideration in the use of protective equipment is the concept of risk compensation.¹³²  This is where the use of protective equipment results in behavioral change such as the adoption of more dangerous playing techniques, which can result in a paradoxical increase in injury rates. The degree to which this phenomenon occurs is discussed in more detail in the review published in the British Journal of Sports Medicine supplement. This may be a particular concern in child and adolescent athletes, in whom head injury rates are often higher than in adult athletes.^133–135 

The competitive, aggressive nature of sport that makes it fun to play and watch should not be discouraged. However, sporting organizations should be encouraged to address violence that may increase concussion risk.^136,137  Fair play and respect should be supported as key elements of sport.

As the ability to treat or reduce the effects of concussive injury after the event is minimal, education of athletes, colleagues, and the general public is a mainstay of progress in this field. Athletes, referees, administrators, parents, coaches, and health care providers must be educated regarding the detection of concussion, its clinical features, assessment techniques, and principles of safe RTP. Methods to improve education including Web-based resources, educational videos, and international outreach programs are important in delivering the message. In addition, concussion working groups, plus the support and endorsement of enlightened sport groups, such as the Fédération Internationale de Football Association (FIFA), International Olympic Commission (IOC), International Rugby Board (IRB), and International Ice Hockey Federation (IIHF) that initiated this endeavor, have enormous value and must be pursued vigorously. Fair play and respect for opponents are ethical values that should be encouraged in all sports and sporting associations. Similarly, coaches, parents, and managers play an important part in ensuring these values are implemented on the field of play.^58,138–150 

In November 2001, the 1st International Conference on Concussion in Sport was held in Vienna, Austria. This meeting was organized by the IIHF in partnership with FIFA and the Medical Commission of the IOC. As part of the resulting mandate for the future, the need for leadership and future updates were identified. The 2nd International Conference on Concussion in Sport was organized by the same group with the additional involvement of the IRB and was held in Prague, Czech Republic, in November 2004. The original aims of the symposia were to provide recommendations for the improvement of safety and health of athletes who suffer concussive injuries in ice hockey, rugby, and football (soccer), as well as other sports. To this end, a range of experts were invited to both meetings to address specific issues of epidemiology, basic and clinical science, injury grading systems, cognitive assessment, new research methods, protective equipment, management, prevention, and long-term outcome.^1,2 

The 3rd International Conference on Concussion in Sport was held in Zurich, Switzerland, on 29–30 October 2008 and was designed as a formal consensus meeting following the organizational guidelines set forth by the US National Institutes of Health. (Details of the consensus methodology can be obtained at http://consensus.nih.gov/ABOUTCDP.htm.) The basic principles governing the conduct of a consensus development conference are summarized below:

1. A broad-based, nongovernment, nonadvocacy panel was assembled to give balanced, objective, and knowledgeable attention to the topic. Panel members excluded anyone with scientific or commercial conflicts of interest and included researchers in clinical medicine, sports medicine, neuroscience, neuroimaging, athletic training, and sports science.

2. These experts presented data in a public session, followed by inquiry and discussion. The panel then met in an executive session to prepare the consensus statement.

3. A number of specific questions were prepared and posed in advance to define the scope and guide the direction of the conference. The principal task of the panel was to elucidate responses to these questions. These questions are outlined below.

4. A systematic literature review was prepared and circulated in advance for use by the panel in addressing the conference questions.

5. The consensus statement is intended to serve as the scientific record of the conference.

6. The consensus statement will be widely disseminated to achieve maximum impact on both current health care practice and future medical research.

The panel chairperson (W.H.M.) did not identify with any advocacy position. The chairperson was responsible for directing the consensus session and guiding the panel's deliberations. Panelists were drawn from clinical practice, academics, and research in the field of sports-related concussion. They do not represent organizations per se but were selected for their expertise, experience, and understanding of this field.

The 4th International Conference on Concussion in Sport was held in Zurich, Switzerland, on 1–3 November 2012 and followed the same outline as for the 3rd meeting. All speakers, consensus panel members, and abstract authors were required to sign an International Committee of Medical Journal Editors Form for Disclosure of Potential Conflicts of Interest. Detailed information related to each author's affiliations and conflicts of interests will be made publicly available on the Concussion in Sport Group Web site and published with the British Journal of Sports Medicine supplement.

This consensus document reflects the current state of knowledge and will need to be modified according to the development of new knowledge. It provides an overview of issues that may be of importance to health care providers involved in the management of sports-related concussion. It is not intended as a standard of care and should not be interpreted as such. This document is only a guide, and is of a general nature, consistent with the reasonable practice of a health care professional. Individual treatment will depend on the facts and circumstances specific to each individual case.

It is intended that this document will be formally reviewed and updated prior to 1 December 2016.

Note that each question is the subject of a separate systematic review that is published in the British Journal of Sports Medicine (2013:47). As such, all citations and details of each topic will be covered in those reviews.

The consensus panel agreed that concussion is an evolving injury in the acute phase with rapidly changing clinical signs and symptoms, which may reflect the underlying physiologic injury in the brain. Concussion is considered to be among the most complex injuries in sports medicine to diagnose, assess, and manage. The majority of concussions in sport occur without LOC or frank neurologic signs. At present, there is no perfect diagnostic test or marker that clinicians can rely on for an immediate diagnosis of concussion in the sporting environment. Because of this evolving process, it is not possible to rule out concussion when an injury event occurs associated with a transient neurologic symptom. All such cases should be removed from the playing field and assessed for concussion by the treating physician or health care provider as discussed below. It was recognized that a cognitive deficit is not necessary for acute diagnosis, as it either may not be present or not detected on examination.

Concussion is a clinical diagnosis based largely on the observed injury mechanism, signs, and symptoms. The vast majority of sports-related concussions (hereafter referred to as concussion) occur without LOC or frank neurologic signs.^151–154  In milder forms of concussion, the athlete might be slightly confused, without clearly identifiable amnesia. In addition, most concussions cannot be identified or diagnosed by neuroimaging techniques (eg, CT or MRI). Several well-validated NP tests are appropriate for use in the assessment of acute concussion in the competitive sporting environment. These tests provide important data on symptoms and functional impairments that clinicians can incorporate into their diagnostic formulation but should not solely be used to diagnose concussion.

Recognizing and evaluating concussion in the adult athlete on the field is a challenging responsibility for the health care provider. Performing this task is often a rapid assessment in the midst of competition with a time constraint and the athlete eager to play. A standardized objective assessment of injury, which excludes more serious injury, is critical in determining disposition decisions for the athlete. The on-field evaluation of sports-related concussion is often a challenge given the elusiveness and variability of presentation, difficulty in making a timely diagnosis, specificity and sensitivity of sideline assessment tools, and reliance on symptoms. Despite these challenges, the sideline evaluation is based on recognition of injury, assessment of symptoms, cognitive and cranial nerve function, and balance. Serial assessments are often necessary. Concussion is often an evolving injury, and signs and symptoms may be delayed. Therefore, erring on the side of caution (keeping an athlete out of participation when there is any suspicion for injury) is important. A standardized assessment of concussion is useful in the assessment of the athlete with suspected concussion but should not take the place of clinician judgment.

It was agreed that a variety of measures should be employed as part of the assessment of concussion to provide a more complete clinical profile for the concussed athlete. Important clinical information can be ascertained in a streamlined manner through the use of a multimodal instrument such as the SCAT. A baseline assessment is advised wherever possible. However, it is acknowledged that further validity studies need to be performed to answer this specific issue.

A future SCAT test battery (ie, SCAT3) should include an initial assessment of injury severity using the Glasgow Coma Scale, immediately followed by observing and documenting concussion signs. Once this is complete, symptom endorsement and symptom severity, neurocognitive function, and balance function should be assessed in any athlete suspected of sustaining a concussion. It is recommended that these latter steps be conducted after a minimum 15-minute rest period on the sideline to avoid the influence of exertion or fatigue on the athlete's performance. While it is noted that this timeframe is an arbitrary one, nevertheless the expert panel agreed that a period of rest was important before assessment. Future research should consider the efficacy for inclusion of vision tests such as the King-Devick test and clinical reaction time tests.^155,156  Recent studies suggest that these may be useful additions to the sideline assessment of concussion. However, the need for additional equipment may make them impractical for sideline use.

It was further agreed that the SCAT3 would be suitable for adults and youths age 13 and over, while a new tool (Child SCAT3) be developed for younger children.

Sports-related concussions are frequently associated with 1 or more symptoms, impaired balance, or cognitive deficits (or a combination of these). These problems can be measured using symptom scales, balance testing, and neurocognitive testing. All 3 modalities can identify significant changes in the first few days after injury, generally with normalization over 1–3 weeks. The presentation of symptoms and the rate of recovery can be variable, which reinforces the value of assessing all 3 areas as part of a comprehensive sports concussion program.

Neuropsychological assessment has been described by the Concussion in Sport Group as a cornerstone of concussion management. Neuropsychologists are uniquely qualified to interpret NP tests and can play an important role within the context of a multifaceted, multimodal, and multidisciplinary approach to managing sports-related concussion. Concussion management programs that use NP assessment to assist in clinical decision making have been instituted in professional sports, colleges, and high schools. Brief computerized cognitive evaluation tools are the mainstay of these assessments worldwide; given the logistical limitation in accessing trained neuropsychologists, however, it should be noted that these are not substitutes for formal NP assessment. At present, there is insufficient evidence to recommend the widespread routine use of baseline NP testing.

A number of novel technological platforms exist to assess concussion including, but not limited to, iPhone (Apple, Cupertino, CA)/smartphone “apps,” quantitative electroencephalography, robotic sensory motor assessment, telemedicine, eye tracking technology, functional imaging and advanced neuroimaging, and head impact sensors. At this stage, only limited evidence exists for their role in this setting and none have been validated as diagnostic. It will be important to reconsider the role of these technologies once evidence is developed.

The current evidence evaluating the effect of rest and treatment after a sports-related concussion is sparse. An initial period of rest may be of benefit. However, further research to evaluate the long-term outcome of rest and the optimal amount and type of rest is needed. Low-level exercise for those who are slow to recover may be of benefit, although the optimal timing after injury for initiation of this treatment is currently unknown. Multimodal physiotherapy treatment for individuals with clinical evidence of cervical spine or vestibular dysfunction may be of benefit. There is a strong need for high-level studies evaluating the effects of a resting period, pharmacologic interventions, rehabilitative techniques, and exercise for individuals who have sustained a sports-related concussion.

Persistent symptoms (>10 days) are reported in 10%–15% of concussions. This percentage may be higher in certain sports (eg, elite ice hockey) and populations (eg, children). In general, symptoms are not specific to concussion, and it is important to consider and manage coexistent conditions. Investigations may include formal NP testing and conventional neuroimaging to exclude structural injury. Currently, there is insufficient evidence to recommend routine clinical use of advanced neuroimaging techniques or other investigative strategies. Cases of concussion in sport in which clinical recovery falls outside the expected window (ie, 10 days) should be managed in a multidisciplinary manner by health care providers with experience in sports-related concussion. Important components of management after the initial period of physical and cognitive rest include associated therapies such as cognitive, vestibular, physical, and psychological therapy; consideration of assessment of other causes of prolonged symptoms; and consideration of commencement of a graded exercise program at a level that does not exacerbate symptoms.

The literature demonstrates that the number and severity of symptoms and previous concussions are associated with prolonged recovery or increased risk of complications (or both). Brief LOC, duration of posttraumatic amnesia, or impact seizures do not reliably predict outcome after concussion, although a cautious approach should be taken in an athlete with prolonged LOC (ie, >1 minute). Children generally take longer to recover from concussions, and assessment batteries have yet to be validated in the younger age group. Currently, there are insufficient data on the influence of genetics and sex on outcome after concussion. Several modifiers are associated with prolonged recovery or increased risk of complications after concussion and have important implications for management. Children with concussion should be managed conservatively, with the emphasis on return to learn before return to sport. In cases of concussion managed with limited resources (eg, nonelite players), a conservative approach should also be taken such that the athlete does not return to sport until fully recovered.

No new valid evidence was provided to suggest that the use of current standard headgear in rugby or mouthguards in American football can significantly reduce players' risk of concussion. No evidence was provided to suggest an association between neck strength increases and concussion risk reduction. There was evidence to suggest that eliminating body checking from Pee Wee ice hockey (ages 11–12 years) and fair-play rules in ice hockey were effective injury-prevention strategies. Helmets need to be able to protect from impacts resulting in a head change in velocity of up to 10 m/s in professional American football and up to 7 m/s in professional Australian football. It also appears that helmets must be capable of reducing head resultant linear acceleration to below 50g and angular acceleration components to below 1500 rad/s²  to optimize their effectiveness. Given that a multifactorial approach is needed for concussion prevention, well-designed and sport-specific prospective analytical studies of sufficient power are warranted for mouthguards, headgear and helmets, facial protection, and neck strength. Measuring the effect of rule changes should also be addressed with future studies, not only assessing new rule changes or legislation but also alteration to or reinforcement of existing rules.

It was agreed that CTE represents a distinct tauopathy with an unknown incidence in athletic populations. It was further agreed that CTE was not related to concussions alone or simply to exposure to contact sports. At present, there are no published epidemiologic, cohort, or prospective studies relating to modern CTE. Due to the nature of the case reports and pathologic case series that have been published, it is not possible to determine the causality or risk factors with any certainty. As such, the speculation that repeated concussion or subconcussive impacts causes CTE remains unproven. The extent to which age-related changes, psychiatric or mental health illness, alcohol or drug use, or coexisting medical or dementing illnesses contribute to this process is largely unaccounted for in the published literature. At present, the interpretation of causation in the modern CTE case studies should proceed cautiously. It was also recognized that it is important to address the fears of parents and athletes from media pressure related to the possibility of CTE.

The value of knowledge transfer as part of concussion education is increasingly becoming recognized. Target audiences benefit from specific learning strategies. Concussion tools exist, but their effectiveness and impact require further evaluation. The media is valuable in drawing attention to concussion, but efforts need to ensure that the public is aware of the right information. Social media as a concussion education tool is becoming more prominent. Implementation of knowledge-transfer models is one approach organizations can use to assess knowledge gaps; identify, develop, and evaluate education strategies; and use the outcomes to facilitate decision making. Implementing knowledge-transfer strategies requires a defined plan. Identifying the needs, learning styles, and preferred learning strategies of target audiences, coupled with evaluation, should be a piece of the overall concussion education puzzle to have an impact on enhancing knowledge and awareness.

A. Pocket Concussion Recognition Tool

B. Sports Concussion Assessment Tool version 3 (SCAT3)

C. Child SCAT3