The Physician and Sportsmedicine
Menubar About Us [Advertiser Services] CME Resource Center Personal Health Journal Home

Agreement Statement
Summary and Agreement Statement of the Second International Conference on Concussion in Sport, Prague 2004

Concussion in Sport Group: Paul McCrory, MBBS, PhD (chair); Karen Johnston, MD, PhD; Willem Meeuwisse, MD, PhD; Mark Aubry, MD; Robert Cantu, MD; Jiri Dvorak, MD; Toni Graf-Baumann, MD, PhD; James Kelly, MD; Mark Lovell, PhD; Patrick Schamasch, MD


For CME accreditation information, instructions and learning objectives, click here.

Background: In November 2001, the First International Symposium on Concussion in Sport was held in Vienna, Austria. This meeting was organized by the International Ice Hockey Federation (IIHF) in partnership with the Federation Internationale de Football (FIFA) and the International Olympic Committee (IOC) Medical Commission. As part of the resulting mandate for the future, the need for leadership and updates was identified. To meet that mandate, the Second International Symposium on Concussion in Sport was organized by the same group and 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, football (soccer), as well as other sports. To this end, a range of experts were invited to both meetings in order 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. At the conclusion of the initial conference, a small group of experts was given a mandate by the conference delegates and organizing bodies to draft a document describing the agreement position reached by those in attendance at that meeting. That document was co-published in the British Journal of Sports Medicine, the Clinical Journal of Sport Medicine, and The Physician and Sportsmedicine.1

The wider interest base resulting from the first meeting and document was reflected by the expanded representation. New groups at the second meeting included trauma surgeons, sport psychologists, and others. The Concussion in Sport Group has produced the current document as an update of the original Vienna consensus document and includes a sideline assessment form with a pocket-sized summary card for use by clinicians.

This protocol represents a work in progress and, as with all other recommendations or proposals, it must be updated as new information is added to the current state of the literature and understanding of this injury.

This paper is a revision and update of the Vienna consensus recommendations developed following the First International Symposium on Concussion in Sport.1 The Prague agreement statement is designed to build on the principles outlined in the original Vienna document and to develop further conceptual understanding of this problem. This document is developed for use by doctors, therapists, health professionals, coaches, and other people involved in the care of injured athletes, whether at the recreational, elite, or professional level.

1. Background Issues

Definition of concussion. Over 35 years ago, the Committee on Head Injury Nomenclature of the Congress of Neurological Surgeons proposed a "consensus" definition of concussion.2,3 This definition was recognized as having a number of limitations in accounting for the common symptoms of concussion. In the Vienna document, a revised consensus definition was proposed as follows:

Sports concussion is defined as a complex pathophysiological process affecting the brain, induced by traumatic biomechanical forces. Several common features that incorporate clinical, pathological, and biomechanical injury constructs that may be utilized in defining the nature of a concussive head injury include:

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

2. Concussion typically results in the rapid onset of short-lived impairment of neurological function that resolves spontaneously.

3. Concussion may result in neuropathological changes, but the acute clinical symptoms largely reflect a functional disturbance rather than structural injury.

4. Concussion results in a graded set of clinical syndromes that may or may not involve loss of consciousness (LOC). Resolution of the clinical and cognitive symptoms typically follows a sequential course.

5. Concussion is typically associated with grossly normal structural neuroimaging studies.

No changes were made to the definition by the Prague group beyond noting that, in some cases, postconcussive symptoms may be prolonged or persistent.

Pathophysiological basis of concussion. At this time, there is no existing animal or other experimental model that accurately reflects a sporting concussive injury. It is noted that in experimental models of more severe injury, a complex cascade of biochemical, metabolic, and gene expression changes occur.4 Whether similar metabolic changes occur in sports concussion, however, remains speculative at this time.5

Concussion grading scales. The Vienna recommendation that injury grading scales be abandoned in favor of combined measures of recovery in order to determine injury severity (and/or prognosis) and hence individually guide return-to-play decisions received continued support.

It was also noted that concussion severity could only be determined in retrospect after all concussion symptoms have cleared, the neurological examination is normal, and cognitive function has returned to baseline.6 There is limited published evidence that concussion injury severity correlates with the number and duration of acute concussion signs and symptoms and/or degree of impairment on neuropsychological testing.7-12 The ongoing development of validated injury severity scales continues in the published literature.13

Subtypes of concussion. One of the issues that was speculated upon at the Vienna conference was whether concussion represents a unitary phenomenon with a linear spectrum of injury severity or whether different concussion subtypes exist. These subtypes may represent differences in clinical manifestations (eg, confusion, memory problems, loss of consciousness), anatomical localization (eg, cerebral vs brainstem), biomechanical impact (rotational vs linear force), genetic phenotype (ApoE4 positive vs ApoE4 negative), neuropathological change (structural injury vs no structural injury), or an as yet undefined difference. These factors may operate independently or interact with each other. It is clear that the variations in clinical outcome with the same impact force require a more sophisticated approach to the understanding of this phenomenon than is currently available.14

The significance of loss of consciousness. The traditional approach to severe traumatic brain injury utilizing LOC as the primary measure of injury severity has acknowledged limitations in assessing the severity of sporting concussive injury. Findings in this field describe LOC in association with specific early deficits, but LOC does not necessarily imply severity.13,15 As such, the presence of LOC as a symptom would not necessarily classify the concussion as complex (see below).

The significance of amnesia. There is renewed interest in posttraumatic amnesia and its role as a surrogate measure of injury severity.13,16 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.8,15,17 Further, it must be noted that retrograde amnesia varies with the time of measurement postinjury and hence is poorly reflective of injury severity.18,19

Pediatric concussive injury. The general recommendations outlined in the Vienna document were originally designed for the management of adult sporting concussion. Agreement was reached, however, that identified those recommendations as relevant and useful to management of children as well. In broad terms, it was felt that the recommendations should be applicable to children (defined as 5 to 18 years of age), whereby children should not be returned to playing or training until clinically completely symptom free.

In addition, the concept of "cognitive rest" was introduced, with special reference to a child's need to limit exertion with activities of daily living and to limit scholastic activities while symptomatic. There was also recognition by the group that additional research is needed to better clarify the potential differences between adults and children with regard to recovery from injury and to develop cognitive assessment tools that better evaluate the younger athlete.

Formal cognitive assessment is currently problematic 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

Because of the different physiological response to head trauma during childhood, a conservative return-to-play approach is recommended. It may be appropriate to extend the amount of time of asymptomatic rest and/or the length of the graded exertion in children and adolescents. Future research is needed in this area.

2. A New Classification of Concussion in Sport

Historically, concussions have been classified with a number of different grading systems. In the Vienna statement, this approach was abandoned. One of the key developments by the Prague group is the understanding that concussion may be categorized for management purposes as either simple or complex.

Simple concussion. In simple concussion, an athlete suffers an injury that progressively resolves without complication over 7 to 10 days. In such cases, apart from limiting playing or training while symptomatic, no further intervention is required during the period of recovery, and the athlete typically resumes sport without further problem. Formal neuropsychological screening does not play a role in these circumstances, although mental status screening should be a part of the assessment of all concussed athletes. Simple concussion represents the most common form of this injury and can be appropriately managed by primary care physicians or by certified athletic trainers working under medical supervision.21 The cornerstone of management is rest until all symptoms resolve and then a graded program of exertion before return to sport. All concussions mandate evaluation by a medical doctor.

Complex concussion. Complex concussion encompasses cases where athletes suffer persistent symptoms (including persistent symptom recurrence with exertion), specific sequelae (eg, prolonged LOC [> 1 minute]), or prolonged cognitive impairment following the injury. This group may also include athletes who suffer multiple concussions over time or where repeated concussions occur with progressively less impact force. In this group, there may be additional management considerations beyond simple return-to-play advice. Formal neuropsychological testing and other investigations should be considered in complex concussions. It is envisaged that such athletes would be managed in a multidisciplinary manner by physicians with specific expertise in the management of concussive injury, such as a sport medicine doctor with experience in concussion, sports neurologist, or neurosurgeon.

3. Clinical Issues

Preparticipation physical examination. Recognizing the importance of 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.22-25 Such a history may pre-identify athletes that fit into the "complex" category outlined above and provides an opportunity for the physician 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, 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.22 The clinical history should also include information about all previous head, face, or neck injuries, as these may have clinical relevance to the present injury. It is worth emphasizing that in the setting of maxillofacial injuries and neck injuries, co-existent concussive injuries may be missed unless specifically assessed. Specific questions pertaining to disproportionate impact 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 the time of injury be sought, both for recent and remote injuries. The benefit of this approach allows for modification and optimization of protective behavior and an opportunity for education.

It is specifically recommended that:
• Both a baseline cognitive assessment test (such as the Prague Sport Concussion Assessment Tool [SCAT, figure 1 - PDF] in the absence of computerized neuropsychological testing) and symptom score are performed as part of the preparticipation evaluation.
• Although formal baseline neuropsychological screening may be beyond the resources of many sports or individuals, it is recommended that in organized high-risk sports consideration be given to having cognitive evaluation regardless of the age or level of performance.

Signs and symptoms of acute concussion. The suspected diagnosis of sports concussion made on the sideline is applicable to both medical and nonmedical personnel and can include clinical symptoms, physical signs, cognitive impairment, and/or LOC (table 1).

TABLE 1. Signs and Symptoms of a Suspected Head Injury
If any one of the following symptoms or problems is present, a head injury should be suspected and appropriate management instituted (see figure 1 - PDF).

Cognitive Features
Unaware of game period, opposition, or score of game

Typical Symptoms (see figure 1 - PDF for standard symptom scale)
Headache or pressure in the head
Balance problems or dizziness
Feeling "dinged," "foggy," stunned, or "dazed"
Visual problems (eg, seeing stars or flashing lights, double vision)
Hearing problems (eg, ringing in the ears)
Irritability or emotional changes
Other symptoms, such as a subjective feeling of slowness and fatigue in the setting of an impact, may indicate that a concussion has occurred or has not fully resolved.26

Physical Signs
LOC or impaired conscious state
Poor coordination or balance
Concussive convulsion/impact seizure
Gait unsteadiness/loss of balance
Slow to answer questions or follow directions
Easily distracted, poor concentration
Displaying inappropriate emotions (eg, laughing, crying)
Vacant stare/glassy eyed
Slurred speech
Personality changes
Inappropriate playing behavior (eg, running the wrong direction)
Significantly decreased playing ability
LOC = loss of consciousness

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 Maddocks questions27 and the Standardized Assessment of Concussion (SAC).28 It is worth noting that standard orientation questions (eg, time, place, person) have been shown to be unreliable in the sporting situation when compared to memory assessment.27,29

It is recognized, however, that abbreviated testing paradigms are designed for rapid concussion evaluation on the sidelines and are not meant to replace comprehensive neuropsychological testing, which is sensitive to detect subtle deficits that may exist beyond the acute episode; nor should they be used as a stand-alone tool for the ongoing management of sports concussions. It should also be recognized that the appearance of symptoms may be delayed several hours following a concussive episode.

Convulsive and motor phenomena. A variety of acute motor phenomena (eg, tonic posturing) or convulsive movements may accompany a concussion.30,31 Although dramatic, these clinical features are generally benign and require no specific management beyond the standard treatment for the underlying concussive injury.

Development of the Sport Concussion Assessment Tool (SCAT). The intent was to create a standardized tool that could be used for patient education as well as for physician assessment of sports concussion. The SCAT (see figure 1 - PDF) was developed by combining the following existing tools into a new standardized tool:

1. Guidelines for the Management of Concussion in Sports. Colorado Medical Society,32

2. Management of Concussion Sports Palm Card—American Academy of Neurology & Brain Injury Association33

3. Standardized Assessment of Concussion (SAC)34

4. Sideline Concussion Check—University of Pittsburgh Medical Center, Thinksafe, Sports Medicine New Zealand Inc, and the Brain Injury Association

5. McGill Abbreviated Concussion Evaluation (ACE) (unpublished)

6. National Hockey League Physician Evaluation Form (unpublished)

7. The UK Jockey Club Assessment of Concussion35

8. Maddocks questions.27

The authors gave input through a process of collaboration and iterative review. The SCAT was evaluated for face and content validity on the basis of scientific literature3 and clinical experience of the authors. The memory questions, specifically, were modified from the validated Maddocks questions to make these questions less football specific.27

4. Investigational Issues

Neuropsychological assessment postconcussion. The application of neuropsychological testing in concussion has been shown to be of value and continues to contribute significant information in concussion evaluation.10,11,36,37 It has been demonstrated that cognitive recovery may precede or follow clinical symptom resolution, suggesting that the assessment of cognitive function should be an important component in any return-to-play protocol.12 It must be emphasized, however, that neuropsychological assessment should not be the sole basis of a return-to-play decision but rather be seen as an aid to the clinical decision making. Although neuropsychological screening may be performed or interpreted by other healthcare professionals, the final return-to-play decision should remain a medical one in which a multidisciplinary approach has been taken.

Neuropsychological testing should not be done while the athlete is symptomatic, since it adds nothing to return-to-play decisions, and it may contaminate the testing process by allowing for practice effects to confound the results. In certain cases, however, serial postinjury follow-up is valuable both as a means to encourage athlete compliance as well as for comparison purposes.

Overriding the principles common to all neuropsychological test batteries is the need for and benefit of baseline preinjury testing and serial follow-up. Recent work with computerized platforms, however, suggests that performance variability may be a key measure for acute concussion diagnosis, even in the absence of a baseline test. This strategy is currently the subject of ongoing research. Inherent problems with most neuropsychological tests include the normal ranges, sensitivity, and specificity of tests and practice or learning effect, as well as the observation that players may return to baseline while still symptomatic.36 Computerized testing utilizing infinitely variable test paradigms may overcome some of these concerns. Computerized testing also has the logistical advantage that the tests may be administered by the team physician (or be Web-based) rather than requiring a neuropsychologist for a formal assessment. The strengths and weaknesses of such testing have been recently reviewed.37

It is recommended that neuropsychological testing remain one of the cornerstones of concussion evaluation in complex concussion. It is not currently regarded as important in the evaluation of simple concussion. While this modality contributes significantly to both understanding of the injury and management of the individual, neuropsychological testing should not be the sole basis of management decisions, either for continued time out or return-to-play decisions.

Objective balance assessment. Balance testing, either with computerized platforms or clinical assessment, may offer additional information in concussed athletes and may be utilized as a part of the overall concussion management strategy, particularly where symptoms or signs indicate a balance component.38

Neuroimaging. It was recognized in the Vienna agreement document that conventional structural neuroimaging is usually normal in concussive injury. Given that caveat, the following suggestions are made: Brain computed tomography (CT) (or, where available, magnetic resonance imaging [MRI] brain scan) contributes little to concussion evaluation but should be employed whenever suspicion of an intracerebral structural lesion exists. Examples of such situations may include prolonged disturbance of conscious state, focal neurological deficit, or worsening symptoms.

Newer structural MRI modalities, including gradient-echo, perfusion, and diffusion-weighted imaging, have greater sensitivity for structural abnormalities; however, the lack of published studies, as well as absent preinjury neuroimaging data, limits the usefulness of this approach in clinical management at the present time.

In addition, the predictive value of various MRI abnormalities that may be incidentally discovered is not established at the present time. Promising new functional imaging technologies (eg, positron-emission tomography [PET], single-photon emission CT [SPECT], functional MRI [fMRI]), while demonstrating some compelling findings, are still at early stages of development.39-41

Although neuroimaging may play a part in the assessment of complex sports concussions or more severe brain injury, it is not essential for simple concussive injury.

Genetic testing. Genotyping (genetic screening) has been demonstrated to be of potential benefit in traumatic brain injury. Published studies have demonstrated that apolipoprotein-epsilon4 allele (ApoE4) is a risk factor for adverse outcome following all levels of brain injury.42-48 Similarly, ApoE4 has been shown to be a risk factor for the development of chronic traumatic encephalopathy in boxers.49 The significance of ApoE4 in sports concussion risk or injury outcome is unclear. Other published studies have noted the association of a particular calcium-subunit gene abnormality with brain swelling following minor head trauma.50 Although still in the early stages of understanding, routine genetic screening cannot be recommended at the present time, and, furthermore, physicians are urged to be mindful of the ethical implications of such testing.

Experimental concussion assessment modalities. Different electrophysiological recording techniques, such as evoked response potential (ERP) and electroencephalogram (EEG), have demonstrated reproducible abnormalities in the postconcussive state.51-53 However, not all studies reliably differentiated concussed athletes from controls.54-57 The clinical significance of these changes remains to be established.

In addition, biochemical serum markers of brain injury (including glial protein S-100b, neuron-specific enolase [NSE], myelin basic protein [MBP], and glial fibrillary acid protein [GFAP]) have been proposed as means by which cellular damage may be detected if present.58,59 However, there is currently not sufficient evidence to justify the use of these markers clinically.

5. Concussion Management

Acute injury. When a player shows any symptoms or signs of a concussion:
• The player should not be allowed to return to play in the current game or practice.
• The player should not be left alone, and regular monitoring for deterioration is essential over the initial few hours following injury.
• The player should be medically evaluated following the injury.
• Return to play must follow a medically supervised stepwise process.

A player should never return to play while symptomatic. "When in doubt, sit them out!"

Return-to-play protocol. As described previously, the majority of injuries will be simple concussions, and such injuries recover spontaneously over several days. In these situations, it is expected that an athlete will proceed rapidly through the stepwise return-to-play strategy.60

During this period of recovery in the first few days following an injury, it is important to emphasize to the athlete that physical and cognitive rest is required. Activities that require concentration and attention may exacerbate the symptoms and as a result delay recovery. Return to play following a concussion follows a stepwise process:

1. No activity, complete rest. Once asymptomatic, proceed to step 2.

2. Light aerobic exercise such as walking or stationary cycling; no resistance training.

3. Sport-specific exercise (eg, skating in hockey, running in soccer); progressive addition of resistance training at steps 3 or 4.

4. Noncontact training drills.

5. Full-contact training after medical clearance.

6. Game play.

With this stepwise progression, the athlete should continue to proceed to the next level if asymptomatic at the current level. If any postconcussion symptoms occur, the patient should drop back to the previous asymptomatic level and try to progress again after 24 hours.

In cases of complex concussion, the rehabilitation will be more prolonged and return-to-play advice will be more circumspect. It is envisaged that complex cases should be managed by physicians with a specific expertise in the management of such injuries.

An additional consideration in return to play is that concussed athletes should not only be symptom free but also should not be taking any pharmacological agents or medications that may affect or modify the symptoms of concussion. Where antidepressant therapy may be commenced during the management of a complex concussion, the decision to return to play while still on such medication must be considered carefully by the clinician concerned (see below).

In professional sport, where there are team physicians experienced in concussion management as well as access to immediate (ie, sideline) neurocognitive assessment, return-to-play management is often more rapid; however, one must still follow the same basic principles, namely, full clinical and cognitive recovery before consideration of return to play.

The role of pharmacological therapy. Pharmacological therapy in sports concussion may be applied in two distinct situations. The first of these is the management of specific symptoms (eg, sleep disturbance, anxiety) in complex concussion, and 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 symptomatology.61

In broad terms, this approach to management should be only considered in complex sports concussions and by clinicians experienced in concussion management.

Sports psychology. In addition, sport psychology approaches may have potential application in this injury, particularly in complex concussion.62 Caregivers are also encouraged to evaluate the concussed athlete for affective symptoms such as depression, as these may be common in concussion.60

6. Other Issues

Prevention. There is no clinical evidence that currently available protective equipment will prevent concussion. In certain sports, protective equipment may prevent other forms of head injury, which may be an important issue for those sports.

Consideration of rule changes (eg, no head checking in ice hockey) to reduce the head injury rate may be appropriate where a clear-cut mechanism is implicated in a particular sport. Similarly, rule enforcement is a critical aspect of such approaches, and referees play an important role.

An important consideration in the use of protective equipment is the concept of risk compensation.63 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. This may be a particular concern in child and adolescent athletes, where head injury rates are often higher than in adult athletes.64

Medicolegal considerations. While agreement exists pertaining to principal messages conveyed within this document, the authors acknowledge that the science of concussion is at early stages, and, therefore, management and return-to-play decisions remain largely in the realm of clinical judgment on an individualized basis.

Education. 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 and their healthcare providers must be educated regarding the detection of concussion, its clinical features, assessment techniques, and principles of safe return to play. Methods to improve education, including Web-based resources, educational videos, and international outreach programs such as Think First, are important in delivering the message. In addition, concussion working groups plus the support and endorsement of enlightened sport groups, such as FIFA, IOC, and IIHF, who initiated this endeavor, have enormous value and must be pursued vigorously.

The promotion of 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.

Research methods. A number of research protocols and data evaluating concussion injury assessment, injury susceptibility, and brain function postinjury were presented at both the Vienna and Prague conferences. All of these techniques, while offering great potential for injury assessment, must be considered experimental at this time. Elite and professional teams are well placed to contribute to these efforts through athlete recruitment for studies demonstrating the scientific value of such approaches.

Such research is essential in contributing to the science of concussion and will potentially provide valuable information for such important issues as clinical management, return-to-play guidelines, and long-term outcome. Therefore, research should be continued and encouraged, both by academics and by sporting organizations.

Future Considerations

The issue of sports concussion management is continually evolving, and the usefulness of expert consensus in establishing a standard of care has been demonstrated by the Vienna agreement. The consensus group established at that meeting has provided ongoing leadership in this field based on the initial mandate established at that time.1 We expect that this Prague agreement will be revised and updated at future meetings.

This concussion agreement statement is simultaneously published in April issues of the British Journal of Sports Medicine, the Clinical Journal of Sport Medicine, and Neurology.


  1. Aubry M, Cantu R, Dvorak J, et al: Summary and agreement statement of the First International Symposium on Concussion in Sport, Vienna 2001. Phys Sportsmed 2002;30(2):57-63 [published concurrently in Br J Sports Med 2002;36(1):6-10 and Clin J Sport Med 2002;12(1):6-11]
  2. Congress of Neurological Surgeons, Committee on Head Injury Nomenclature: Glossary of Head Injury. Clin Neurosurg 1966;12:386-394
  3. Johnston KM, McCrory P, Mohtadi NG, et al: Evidence-based review of sport-related concussion: clinical science. Clin J Sport Med 2001;11(3):150-159
  4. Hovda DA, Lee SM, Smith ML, et al: The neurochemical and metabolic cascade following brain injury: moving from animal models to man. J Neurotrauma 1995;12(5):903-906
  5. McIntosh TK, Smith DH, Meaney DF, et al: Neuropathological sequelae of traumatic brain injury: relationship to neurochemical and biomechanical mechanisms. Lab Invest 1996;74(2):315-342
  6. Cantu RC: Concussion severity should not be determined until all post concussion symptoms have abated. Lancet Neurology 2004;3(7):437-438
  7. Hinton-Bayre AD, Geffen G: Severity of sports-related concussion and neuropsychological test performance. Neurology 2002;59(7):1068-1070
  8. McCrory PR, Ariens T, Berkovic SF: The nature and duration of acute concussive symptoms in Australian football. Clin J Sport Med 2000;10(4):235-238
  9. Mrazik M, Ferrara MS, Peterson CL, et al: Injury severity and neuropsychological and balance outcomes of four college athletes. Brain Inj 2000;14(10):921-931
  10. Lovell MR, Collins MW, Iverson GL, et al: Recovery from mild concussion in high school athletes. J Neurosurg 2003;98(2):296-301
  11. Collins MW, Grindel SH, Lovell MR, et al: Relationship between concussion and neuropsychological performance in college football players. JAMA 1999;282(10):964-970
  12. Bleiberg J, Cernich AN, Cameron K, et al: Duration of cognitive impairment after sports concussion. Neurosurgery 2004;54(5):1073-1080
  13. McCrea M, Kelly JP, Randolph C, et al: Immediate neurocognitive effects of concussion. Neurosurgery 2002;50(5):1032-1042
  14. McCrory P, Johnston KM, Mohtadi NG, et al: Evidence-based review of sport-related concussion: basic science. Clin J Sport Med 2001;11(3):160-165
  15. Lovell MR, Iverson GL, Collins MW, et al: Does loss of consciousness predict neuropsychological decrements after concussion? Clin J Sport Med 1999;9(4):193-198
  16. Cantu RC: Posttraumatic retrograde and anterograde amnesia: pathophysiology and implications in grading and safe return to play. J Athl Train 2001;36(3):244-248
  17. Leininger BE, Gramling SE, Farrell AD, et al: Neuropsychological deficits in symptomatic minor head injury patients after concussion and mild concussion. J Neurol Neurosurg Psychiatry 1990;53(4):293-296
  18. Yarnell PR, Lynch S: The 'ding': amnestic state in football trauma. Neurology 1973;23(2):196-197
  19. Yarnell PR, Lynch S: Retrograde memory immediately after concussion. Lancet 1970;1(7652):863-864
  20. McCrory P, Collie A, Anderson V, et al: Can we manage sport related concussion in children the same as in adults? Br J Sports Med 2004;38(5):516-519
  21. Guskiewicz KM, Bruce SL, Cantu RC, et al: Recommendations on management of sport-related concussion: summary of the National Athletic Trainers' Association position statement. Neurosurgery 2004;55(4):891-896
  22. McCrory P: Preparticipation assessment for head injury. Clin J Sport Med 2004;14(3):139-144
  23. Johnston KM, Lassonde M, Ptito A: A contemporary neurosurgical approach to sport-related head injury: the McGill concussion protocol. J Am Coll Surg 2001;192(4):515-524
  24. Delaney JS, Lacroix VJ, Leclerc S, et al: Concussions during the 1997 Canadian Football League season. Clin J Sport Med 2000;10(1):9-14
  25. Delaney JS, Lacroix VJ, Leclerc S, et al: Concussions among university football and soccer players. Clin J Sport Med 2002;12(6):331-338
  26. Iverson GL, Gaetz M, Lovell MR, et al: Relation between subjective fogginess and neuropsychological testing following concussion. J Int Neuropsychol Soc 2004;10(6):904-906
  27. Maddocks DL, Dicker GD, Saling MM: The assessment of orientation following concussion in athletes. Clin J Sport Med 1995;5(1):32-35
  28. McCrea M, Kelly JP, Randolph C, et al: Standardized assessment of concussion (SAC): on-site mental status evaluation of the athlete. J Head Trauma Rehabil 1998;13(2):27-35
  29. McCrea M, Kelly JP, Kluge J, et al: Standardized assessment of concussion in football players. Neurology 1997;48(3):586-588
  30. McCrory P: Video analysis of the acute clinical manifestations of concussion in Australian rules football. Sports Medicine Australia/Australasian College of Sports Physicians Annual Scientific Conference, 1996, Canberra, Sports Medicine Australia, 1996, conference abstract, pp 214-215
  31. McCrory PR, Berkovic SF: Video analysis of acute motor and convulsive manifestations in sport related concussion. Neurology 2000;54(7):1488-1491
  32. Colorado Medical Society Sports Medicine Committee: Guidelines for the management of concussion in sports. Denver, Colorado Medical Society, 1991
  33. Kelly JP, Rosenberg JH: Diagnosis and management of concussion in sports. Neurology 1997;48(3):575-580
  34. McCrea M, Randolph C, Kelly J: The Standardized Assessment of Concussion (SAC): Manual for Administration, Scoring and Interpretation, ed 2. Waukesha, WI, Mike McRea, 2000
  35. Turner M: Concussion and head injuries in horse racing, in The Jockey Club Conference on Head Injury in Sport. London, The Jockey Club of England, 1998, pp 1-2
  36. Grindel SH, Lovell MR, Collins MW: The assessment of sport-related concussion: the evidence behind neuropsychological testing and management. Clin J Sport Med 2001;11(3):134-143
  37. Collie A, Darby D, Maruff P: Computerised cognitive assessment of athletes with sports related head injury. Br J Sports Med 2001;35(5):297-302
  38. Guskiewicz KM: Postural stability assessment following concussion: one piece of the puzzle. Clin J Sport Med 2001;11(3):182-189
  39. Johnston KM, Ptito A, Chankowsky J, et al: New frontiers in diagnostic imaging in concussive head injury. Clin J Sport Med 2001;11(3):166-175
  40. Chen JK, Johnston KM, Frey S, et al: Functional abnormalities in symptomatic concussed athletes: an fMRI study. Neuroimage 2004;22(1):68-82
  41. Jantzen KJ, Anderson B, Steinberg FL, et al: A prospective functional MR imaging study of mild traumatic brain injury in college football players. AJNR Am J Neuroradiol 2004;25(5):738-745
  42. Teasdale GM, Nicoll JA, Murray G, et al: Association of apolipoprotein E polymorphism with outcome after head injury. Lancet 1997;350(9084):1069-1071
  43. Friedman G, Froom P, Sazbon L, et al: Apolipoprotein E-epsilon4 genotype predicts a poor outcome in survivors of traumatic brain injury. Neurology 1999;52(2):244-248
  44. Gross R: APOE epsilon4 allele and chronic traumatic brain injury. JAMA 1997;278(24):2143
  45. Katzman R, Galasko DR, Saitoh T, et al: Apolipoprotein-epsilon4 and head trauma: synergistic or additive risks? Neurology 1996;46(3):889-891
  46. Liberman JN, Stewart WF, Wesnes K, et al: Apolipoprotein E epsilon 4 and short-term recovery from predominantly mild brain injury. Neurology 2002;58(7):1038-1044
  47. Nicoll JA, Roberts GW, Graham DI: Apolipoprotein E epsilon 4 allele is associated with deposition of amyloid beta-protein following head injury. Nat Med 1995;1(2):135-137
  48. Nicoll JA, Roberts GW, Graham DI: Amyloid beta-protein, APOE genotype and head injury. Ann N Y Acad Sci 1996;777:271-275
  49. Jordan BD, Relkin NR, Ravdin LD, et al: Apolipoprotein E epsilon4 associated with chronic traumatic brain injury in boxing. JAMA 1997;278(2):136-140
  50. Kors EE, Terwindt GM, Vermeulen FL, et al: Delayed cerebral edema and fatal coma after minor head trauma: role of the CACNA1A calcium channel subunit gene and relationship with familial hemiplegic migraine. Ann Neurol 2001;49(6):753-760
  51. Dupuis F, Johnston K, Lavoie M, et al: Concussion in athletes produces brain dysfunction as revealed by event related potentials. Neuroreport 2000;11(18):4087-4092
  52. Gaetz M, Goodman D, Weinberg H: Electrophysiological evidence for the cumulative effects of concussion. Brain Inj 2000;14(12):1077-1088
  53. Lavoie ME, Dupuis F, Johnston KM, et al: Visual p300 effects beyond symptoms in concussed college athletes. J Clin Exp Neuropsychol 2004;26(1):55-73
  54. Hinton-Bayre AD, Geffen G, McFarland K: Mild head injury and speed of information processing: a prospective study of professional rugby league players. J Clin Exp Neuropsychol 1997;19(2):275-289
  55. Clark CR, O'Hanlon AP, Wright MJ, et al: Event-related potential measurement of deficits in information processing following moderate to severe closed head injury. Brain Inj 1992;6(6):509-520
  56. Cremona-Meytard SL, Geffen GM: Visuospatial attention deficits following mild head injury in Australian rules football players, in Hendy J, Caine D, Pfaff A, et al (eds): The Life Cycle: Development, Maturation, Senescence. Proceedings of the 16th Annual Brain Impairment Conference. Sydney, Australian Academic Press, 1993, pp 137-147
  57. Cremona-Meteyard SL, Clark CR, Wright MJ, et al: Covert orientation of visual attention after closed head injury. Neuropsychologia 1992;30(2):123-132
  58. Ingebrigtsen T, Romner B, Trumpy JH: Management of minor head injury: the value of early computed tomography and serum protein S-100 measurements. J Clin Neurosci 1997;4(1):29-34
  59. Otto M, Holthusen S, Bahn E, et al: Boxing and running lead to a rise in serum levels of S-100B protein. Int J Sports Med 2000;21(8):551-555
  60. Johnston KM, Bloom GA, Ramsay J, et al: Current concepts in concussion rehabilitation. Curr Sports Med Rep 2004;3(6):316-323
  61. McCrory P: Should we treat concussion pharmacologically? the need for evidence based pharmacological treatment for the concussed athlete. Br J Sports Med 2002;36(1):3-5
  62. Bloom GA, Horton AS, McCrory P, et al: Sport psychology and concussion: new impacts to explore. Br J Sports Med 2004;38(5):519-521
  63. Hagel B, Meeuwisse W: Risk compensation: a "side effect" of sport injury prevention? Clin J Sport Med 2004;14(4):193-196
  64. Orchard J, Wood T, Seward H, et al: Comparison of injuries in elite senior and junior Australian football. J Sci Med Sport 1998;1(2):83-88

Dr McCrory is an associate professor at the Center for Health, Exercise and Sports Medicine and The Brain Research Institute at the University of Melbourne, Australia. Dr Johnston is a neurosurgeon and concussion consultant in the departments of neurosurgery, kinesiology, and physical education at McGill University and director of the concussion program at McGill Sport Medicine Centre in Montreal. Dr Meeuwisse is a professor and medical director at the University of Calgary Sport Medicine Centre and sport injury epidemiologist for the National Hockey League (NHL) in Calgary, Alberta, Canada. Dr Aubry is the chief medical officer of the International Ice Hockey Federation in Zurich. Dr Cantu is the chairman of the department of surgery, chief of Neurosurgery Service, and director of Sports Medicine Service at Emerson Hospital in Concord, Massachusetts, and the medical director of the National Center for Catastrophic Sports Injury Research in Chapel Hill, North Carolina. Dr Dvorak is the chairman of the Federation Internationale de Football (FIFA) Medical Research and Assessment Center (F-MARC) and chairman of the department of neurology at the Schulthess Clinic in Zurich. Dr Graf-Baumann is the director of the Office for Science Management and administration and scientific director of the German Society for Musculo-Skeletal Medicine and Pain Therapy at F-MARC in Teningen, Germany. Dr Kelly is a professor of neurosurgery and rehabilitation medicine at the University of Colorado School of Medicine in Denver. Dr Lovell is the director of the Sports Medicine Concussion Program at the University of Pittsburgh and codirector for the NHL Neuropsychology Program in Pittsburgh. Dr Schamasch is the medical and scientific director of the International Olympic Committee in Lausanne, Switzerland.

Address correspondence to Paul McCrory, MBBS, PhD, PO Box 93, Shoreham, Victoria 3916, Australia; e-mail to [email protected].

Disclosure information: Dr Lovell is a shareholder of ImPACT, a neuropsychological testing program. No other author has any declared conflict of interest or concussion industry-related affiliation. No drug is mentioned in this article for an unlabeled use.

Reprints of this article will not be available.