Concussion is a form of mild traumatic brain injury that involves an alteration in mental status that is associated with confusion and amnesia.1 Contrary to previous definitions of concussion, which stipulated the loss of consciousness, transient loss of consciousness may or may not be present.1 In 2010, the CDC estimated that traumatic brain injury, either as a primary or secondary diagnosis, accounted for 2.5 million Emergency Department visits, hospitalizations, and deaths in the United States.2 These numbers, however, underestimate the true incidence of traumatic brain injuries, as a result of the large number of unreported cases. Traumatic brain injury is subdivided into mild, moderate, and severe cases, with the term “concussion” generally used interchangeably with “mild traumatic brain injury.” Criteria describing mild traumatic brain injury include: 1) Normal structural imaging, 2) Loss of consciousness < 30 minutes, 3) Alteration of Consciousness/Mental State for “a moment” to 24 hours, 4) Post-traumatic amnesia for 0-1 day, 5) Glasgow Coma Scale score of 13-15, and 6) Abbreviated Injury Severity Scale 1-2.2 The vast majority of cases seen in Emergency Departments in the United States qualify as mild, resulting in ED discharge for 87% of presenting patients.3 Common causes of non-fatal traumatic brain injury in the United States include falls; motor vehicle-related injuries; and head trauma from or against an object, including sports injuries. 3
Concussions and Youth Sports – A Brief Background
Sports injuries represent a major cause of traumatic brain injuries, of which the vast majority are mild concussions. A 2006 study by Langlois et al. extrapolated the incidence of sports-related traumatic brain injuries. Using CDC data, which reported the incidence of sports-related traumatic brain injuries involving loss of consciousness as 300,000, together with findings from other studies reporting that loss of consciousness occurs in between 8% and 19.2% of such injuries, the authors estimated an incidence of 1.6 to 3.8 million sports-related concussions each year in the United States.4 This estimate accounts for both reported and unreported cases of traumatic brain injury. Contact sports carry the greatest risk, with particularly high incidences in American football, ice hockey, soccer, boxing, and rugby.5
The groups most likely to visit the ED or undergo hospitalization related to traumatic brain injury in the United States are children aged 0-4, adolescents aged 15-19, and adults aged 75 and over.3 Children and young adults are at risk for sports-related head injuries as a result of the heavy involvement in both organized and unorganized sports and recreational activities in this age group. Indeed, participation in high school athletics has been on the rise over the years. According to a 2012 epidemiological study by Marar et al, the 2009-10 school year saw over half of all students participate in sports, accounting for over 3.1 million girls and 4.2 million boys.6 It is estimated that more than 25% of head injuries and concussions in children result from sports or athletic activities; sports are second only to motor vehicle accidents as the leading cause of concussions amongst individuals aged 15-24 years.5,6 Concussion is a major concern in youth athletics, not simply due to the fact that the vast majority of athletes are < 19 years old, but also because young athletes are more susceptible to concussions than their older counterparts.7 Numerous theories attempt to explain this increased susceptibility among younger athletes, most of which hypothesize the continuing neurocognitive development throughout adolescence, in addition to an increased head to neck mass ratio following the adolescent growth spurt and relatively weaker neck musculature versus adults.6,7 Furthermore, it has been suggested that age plays a role in recovery from concussions, with younger athletes experiencing a longer recovery period.7
Potential Long-Term Risks of Sports-Related Head Injury
While athletes typically return to their baseline cognitive and motor performance within weeks of a concussion, certain sports in which repeated head injury may occur expose the athlete to the risk of long-term neurological damage. The pathogenesis of traumatic brain injury and it’s sequelae are not completely understood, but the most probable cellular mechanism is thought to be diffuse axonal injury due to shearing forces.8 Axonal injury from trauma-induced shearing “disconnects or impairs cortical circuitry, thalamic circuitry, or both, contributing to cognitive impairment and dementia.” 8 Interestingly, the neuropathological changes differ between single-incident traumatic brain injury and the multi-incident traumatic brain injury that can frequently be seen in collision sports. Following a single traumatic incident, Aβ amyloid deposition can occur within hours of the injury. In individuals who have undergone chronic head trauma, however, Aβ amyloid plaques are not generally evident in more than half of cases, whereas tau positive neurofibrillary tangles can be seen prominently throughout the neocortex. 8,9 Gross neuropathological changes can include “atrophy of the cerebral hemispheres, medial temporal lobe, thalamus, mammillary bodies, and brainstem, with ventricular dilatation and a fenestrated cavum septum pellucidum.”9
The term Chronic Traumatic Encephalopathy, or CTE, is used to describe the aforementioned progressive neurological degeneration and pathological changes that occur as the result of a clear environmental etiology, specifically repeated traumatic head injury. CTE is thought to distinct from other tauopathies by “the preferential involvement of the superficial cortical layers, irregular, patchy distribution in the frontal and temporal cortices, propensity for sulcal depths, prominent perivascular, periventricular and subpial distribution, and marked accumulation of tau-immunoreactive astrocytes.”9 CTE shares identical neuropathalogical changes with dementia pugilistica, a well-described condition of progressive neurological decline seen in boxers. In dementia pugilistica, however, there is a clear correlation between neuropathology and number of rounds boxed or knockouts suffered, whereas in CTE, no correlation between concussion history and neuropathology is seen.8 While this may be explained to slightly different mechanisms of injury in boxing versus other contact sports such as football, it is almost certainly confounded by poorer recordkeeping of injury in certain sports in which return-to-play is encouraged.
It is currently unclear whether the age at which an athlete suffers repeated head injuries impacts the future risk of CTE. Further studies are necessary to ascertain if the increased risk of head injury seen in youth athletics, as described above, correlates with an increased incidence and/or severity of long-term neurological complications.
In addition to the potential development of CTE, young athletes are potentially more susceptible to second-impact syndrome, which is a rare but very serious and potentially catastrophic syndrome that has been described when an athlete experiences a second incident of head trauma before having completely recovered from the first. The pathophysiology of second-impact syndrome is thought to involve the loss of autoregulation of cerebral blood flow leading to vascular engorgement, increased intracranial pressure, and possible brain herniation and death.6,7,10 Though second-impact syndrome is an extremely rare complication and, according to a 2007 New England Journal of Medicine paper, is highly disputed and largely unfounded, it is still important to consider any and all possible risks to the health of young athletes when making management decisions.10
Sports-Related Head Injury in the Media
Recent high-profile media stories have thrust the topic of sports-related head injury, both in youth and professional athletics, into the national conversation. A number of professional sports leagues and organizations, such as the National Football League (NFL) and National Collegiate Athletic Association (NCAA), have come under fire in recent years with regards to concussions and subsequent long-term neurological damage, such as CTE, among former athletes. In 2007, New York Times columnist Alan Schwarz published an article on the suicide of 44-year-old former NFL safety Andre Waters. In the article, Schwarz relays the expert opinion of neuropathologist Dr. Bennet Omalu from the University of Pittsburgh, who claimed that “Waters’ brain tissue had degenerated into that of an 85-year-old man with similar characteristics as those of early stage Alzheimer’s victims,” and that he believed that repeated concussions sustained during Waters’ NFL career was to blame for his brain damage, depression, and ultimate suicide.11 At the time, the NFL declined comment on the specific case, while stating that they planned to begin a study of retired players later that year to examine any possible connection between concussions and depression.
In 2011, a group of former players filed a lawsuit against the NFL, asserting that the league should have reasonably known since its inception that the sport could lead to brain damage amongst players, and that the NFL knowingly deceived players and withheld safety information in an effort to increase profits and “sensationalize” the hard-hitting aspect of the sport.12 As of June 1, 2013, the litigation included more than 4,800 former players plus their spouses. On April 15, 2015, the United States District Court for the Eastern District of Pennsylvania entered a final order approving a settlement reached between the NFL and retired players, which included monetary awards for post-mortem neurological diagnoses including ALS, Alzheimer’s, Parkinson’s, dementia, and Chronic Traumatic Encephalopathy.13
In addition to the high-profile NFL and subsequent NCAA litigations, a number of sports-related injuries at the high school level were portrayed in the national news and directly led to legislation to protect young athletes. In 2006, then 13-year-old Zackery Lystedt suffered a head injury during a junior high school football game. After the play, in which his head struck the ground during a tackle, he laid on the ground clutching his helmet with his hands. Following a brief halftime break, Zackery was allowed to return to the game and participated in a number of other contact plays. He subsequently collapsed on the field and was airlifted to a local hospital for emergency surgery due to life-threatening cerebral edema. His recovery since that day has been long and difficult, and he first was able to stand under his own power three years after his injury.14 In May 2009, Washington state passed the “Lystedt Law,” named in Zackery’s honor, which requires that any young athlete showing signs of concussion be examined and cleared on the sideline by a health professional prior to being allowed back into the game. At the time, this law was the first of its kind on the state level. In less than 5 years, however, all 50 states and the District of Columbia passed similar legislation.15
Indeed, awareness of the health risks posed by concussions has dramatically increased in recent years as a result of a number of high profile cases. This heightened awareness has led directly to increased state legislation and public education campaigns, such as the CDC’s HEADS UP program, with the aim of both preventing concussions, as well as ensuring appropriate concussion management and return-to-play guidelines in the event of concussions in young athletes.3
Sideline Evaluation of the Young Athlete with Suspected Concussion
On March 18, 2013, the American Academy of Neurology released updated guidelines on the evaluation of suspected concussion and return-to-play guidelines in athletes. The updated guidelines, published in Neurology, replaced the existing guidelines and concussion grading system from 1997. Among other things, the 2013 guidelines established that there is no set timeline for safe return-to-play and that concussion severity and return-to-play should be assessed individually for each athlete.
Athletes who are suspected to have sustained a concussion should be assessed on the sideline by a medical professional according to standardized diagnostic tool such as the Post-Concussion Symptom Scale (sensitivity 64-89%), Graded Symptom Checklist (sensitivity 64-89%), or Standardized Assessment of Concussion (sensitivity 80-94%).16 A combination of tests is likely to improve diagnostic accuracy, though it has not been determined which combination of tests is superior.
Of the tests available, the Standardized Assessment of Concussion (SAC) is one of the earliest, best studied, and has a fairly high sensitivity range, and thus is a sensible first-line tool for screening. The SAC is best interpreted when compared to a pre-season baseline score for each individual player.16 A 2001 study of standardized mental status testing on the sideline following sports-related concussion found a decline in SAC score at the time of injury versus the pre-injury baseline to be 95% sensitive and 76% specific in “accurately classifying injured and uninjured subjects on the sideline.”17 The test, which assesses four neurocognitive domains (orientation, immediate memory, concentration, and delayed recall) takes approximately 6 minutes to complete and is suitable for administration on the sideline.16 Applications for smart phones and tablets have made it easier to implement standardized concussion assessment tools on the sideline, and are available for free or for a nominal fee. Other standardized sideline assessment tools, such as the Sideline Concussion Assessment Tool (SCAT3) or Concussion Assessment & Response: Sport Version (CARE) are widely used but have not been evaluated in prospective trials to the same extent as SAC. The SAC checklist can be seen below in Figure 1.
Figure 1 – Standardized Assessment of Concussion (SAC)17
In 2010, a study by Grubenhoff et al investigated the reliability of the SAC in an emergency room population of 348 children aged 6-18 years of age who presented with either blunt head injury (cases) or minor extremity injury (controls). The study found that the tool reliably assessed minor traumatic brain injury symptoms for all students 6 years and older, though it did not necessarily reflect the severity of injury.18
It is important to note that while standardized assessment checklists such as the SAC are useful tools in identifying possible concussion and have been found to increase the accuracy of concussion assessment on the sideline, they should not be used as a replacement for a comprehensive medical examination, but rather as part of a complete evaluation of the athlete.17 A complete review of symptoms and physical exam should be performed to assess the presence and severity of symptoms. Other serious injuries such as cervical spinal injury should also be assessed. Furthermore, if a high index of suspicion for concussion still exists following a negative concussion screen with one of the standardized assessment tools, it is still prudent to remove the athlete from the game for further monitoring.
In November 2012, the 4th International Conference on Concussion and Sport was held in Zurich, Switzerland. According to a consensus statement released from this conference, concussion should be suspected in any athlete exhibiting signs or symptoms in any of the following domains:19
- Somatic (e.g. headache)
- Cognitive (e.g. feeling “foggy”)
- Emotional (e.g. lability)
- Physical Signs (e.g. loss of consciousness, amnesia)
- Behavioral changes (e.g. irritability)
- Cognitive impairment (e.g. slowed reaction times)
- Sleep disturbance (e.g. insomnia)
According to the consensus statement, “if any one or more of these components is present, a concussion should be suspected and the appropriate management strategy instituted.”19
Return-to-Play in the Young Athlete with Concussion
According to the 2013 American Academy of Neurology guidelines, all athletes with suspected concussion should be immediately removed from the game or practice and prohibited from returning to play until a Licensed Health Care Professional has determined that the concussion has resolved and the athlete is asymptomatic off of medication.16 The American Academy of Neurology also recommends that athletes of high school age or younger are managed more conservatively than older athletes with respect to return-to-play decisions.16 These recommendations are both Level B, which in the AAN classification of recommendations, requires at least one Class I study or two consistent Class II studies and is “probably effective for the given condition in the specified population.”20
To guide return-to-play decision making, a graded return-to-play protocol should be conservatively followed. Firstly, an athlete diagnosed with a concussion, regardless of level of severity, should not be allowed to return to play or practice on the same day under any circumstances.19 Secondly, the athlete’s response to a multi-stage rehabilitation program should be assessed over the next week or more. A graded return-to-play protocol has been suggested in the consensus statement from the 4th International Conference on Concussion in Sport in Zurich in 2012, and this rehabilitation strategy received a Level C recommendation from the American Academy of Neurology in the 2013 evidence-based guideline update.16,19 The suggested protocol from the 2012 Zurich conference can be seen below in Figure 2.19
Figure 2 – Graded Return-to-Play Protocol
The protocol consists of six stages of rehabilitation, each with increasing intensity, sport-specificity, and contact. The athlete should proceed to the next stage if asymptomatic at the current stage for 24 hours.19 In the event that post-concussion symptoms occur at a certain level, the athlete should revert to the previous stage for 24 hours of asymptomatic rehabilitation prior to attempting to progress again.19 Post-concussion symptoms can include headache, dizziness, and concentration problems.10
Retirement-from-play should be considered in athletes who have experienced multiple concussions. Multiple concussions are not uncommon among young athletes, as athletes who have experienced concussion are at a slightly increased risk of subsequent concussions during the same playing season versus athletes who have not been concussed, particularly in the first 10 days following the first concussion.10,16 The American Academy of Neurology suggests that Licensed Health Care Professionals should consider retirement-from-play for young athletes with multiple concussions and who display persistent neurological impairments, using formal assessment tools to guide decision making.16 In a Level B recommendation, the AAN suggests that these athletes and their parents receive counseling from Licensed Health Care Professionals regarding the potential long-term risks of multiple concussions, such as Chronic Traumatic Encephalopathy.
Indications for Hospital Assessment and Imaging
Although hospital assessment and neuroimaging is not necessary to diagnose sports-related concussions, the American Academy of Neurology recommends that neuroimaging should be considered to rule out more serious traumatic brain injury, such as intracranial hemorrhage, for athletes exhibiting certain signs and symptoms (Level C recommendation).16 These symptoms include “loss of consciousness, posttraumatic amnesia, persistently altered mental status (Glasgow Coma Scale < 15), focal neurological deficit, evidence of skull fracture on examination, or signs of clinical deterioration.”16 Various criteria exist for guiding the clinical decision to obtain CT imaging following concussion, such as the New Orleans Criteria for patients with a Glasgow Coma Scale of 15, and the Canadian CT Head Rules for patients with a Glasgow Coma Scale of 13-15, though the latter only applies to patients 16 years and older.10 Given the more conservative management strategy recommended by the American Academy of Neurology for young athletes, there should be a low threshold for referral to a hospital setting, and any of the above mentioned symptoms should be considered worrisome and should prompt referral to the Emergency Department.
Recent media coverage, legislation, and high-profile litigations increased awareness of sports-related concussions. Sports-related concussions and the management thereof are particularly important in young athletes due to the increased vulnerability and high percentage of athletic participation seen in this age group. Furthermore, though unproven, there is concern for potential age-related long-term effects of concussion in young athletes. Young athletes suspected of suffering a concussion should be immediately removed from the game and evaluated by a Licensed Health Care Professional using a standardized assessment tool in conjunction with a complete medical examination. Great care should be taken to assess potential signs and symptoms of a more traumatic brain injury, and a low threshold should exist for referral to a hospital setting for further evaluation and management. Return-to-play should not occur on the same day and should be achieved only once the athlete is asymptomatic following a graded return-to-play protocol, which should take a minimum of approximately one week to complete.
Numerous resources are available for healthcare professionals, coaches, parents, and young athletes on the American Academy of Neurology’s website (https://www.aan.com/concussion) or the CDC’s HEADS UP campaign (http://www.cdc.gov/headsup/index.html).
- Practice parameter: the management of concussion in sports (summary statement). Report of the Quality Standards Subcommittee. Neurology 1997; 48:581.
- Brasure M, Lamberty GJ, Sayer NA, Nelson NW, MacDonald R, Ouellette J, Tacklind J, Grove M, Rutks IR, Butler ME, Kane RL, Wilt TJ. Multidisciplinary Postacute Rehabilitation for Moderate to Severe Traumatic Brain Injury in Adults. (Prepared by the Minnesota Evidence-based Practice Center under Contract No. 290-2007-10064-I.) AHRQ Publication No. 12-EHC101-EF. Rockville, MD: Agency for Healthcare Research and Quality; June 2012.effectivehealthcare.ahrq.gov/reports/final.cfm.
- Centers for Disease Control and Prevention. (2014). Report to Congress on Traumatic Brain Injury in the United States: Epidemiology and Rehabilitation. National Center for Injury Prevention and Control; Division of Unintentional Injury Prevention. Atlanta, GA.
- Langlois JA, Rutland-Brown W, Wald MM. The epidemiology and impact of traumatic brain injury: a brief overview. J Head Trauma Rehabil 2006; 21:375–378.
- Browne GJ, Lam LT. Concussive head injury in children and adolescents related to sports and other leisure physical activities. Br J Sports Med 2006; 40:163–168.
- Marar M, McIlvain NM, Fields SK, Comstock RD. Epidemiology of concussions among United States high school athletes in 20 sports. Am J Sports Med 2012; 40(4):747-755.
- Buzzini SR, Guskiewicz KM. Sports-related concussion in the young athlete. Curr Opin Pediatr 2006; 18(4):376-382.
- DeKosky ST, Ikonomovic MD, Gandy S. Traumatic Brain Injury – Football, Warfare, and Long-Term Effects. N Engl J Med 2010; 363:1293-1296.
- McKee AC, Cantu RC, Nowinski CJ, et al. Chronic traumatic encephalopathy in athletes: progressive tauopathy following repetitive head injury. J Neuropathol Exp Neurol 2009; 68(7):709-735.
- Ropper AH, Gorson KC. Concussion. N Engl J Med 2007; 356:166-172.
- Schwarz, Alan. “Expert ties ex-player’s suicide to brain damage.” The New York Times. [New York]. Published: January 18, 2007. Internet. Accessed July 8, 2015.
- Master Administrative Class Action Complaint for Medical Monitoring In Re: National Football League Players’ Concussion Injury Litigation. Gerald Allen, Joseph Kowalewski, David Little, Shawn Wooden, and Ron Fellows, on behalf of themselves and others similarly stated v. National Football League and NFL Properties, LLC. Case 2:12-cv-03224-AB. United States District Court for the Eastern District of Pennsylvania. (2012).
- Class Action Settlement Agreement as of June 25, 2014. In Re: National Football League Players’ Concussion Injury Litigation. Kevin Turner and Shawn Wooden, on behalf of themselves and others similarly situated v. National Football League and NFL Properties, LLC, successor-in-interest to NFL Properties, Inc. Case 2:12-md-02323-AB. United States District Court for the Eastern District of Pennsylvania. (2014).
- Centers for Disease Control and Prevention. The Lystedt Law: A Concussion Survivor’s Story. Internet. http://www.cdc.gov/headsup/pdfs/stories/031210-zack-story.pdf. Accessed July 9, 2015.
- Centers for Disease Control and Prevention. Implementing return to play: learning from the experiences of early implements. Internet. http://www.cdc.gov/headsup/pdfs/policy/rtp_implementation-a.pdf. Accessed July 9, 2015.
- Giza CC, Kutcher JS, Ashwal S, et al. Summary of evidence-based guideline update: evaluation and management of concussion in sports. Neurology 2013; 80(24):2250-2257.
- McCrea M. Standardized mental status testing on the sideline after sports-related concussion. J Athl Train 2001; 36(3):274-279.
- Grubenhoff JA, Kirkwood M, Gao D, et al. Evaluation of the standardized assessment of concussion in a pediatric emergency department. Pediatrics 2010;126(4):688-95.
- McCrory P, Meeuwisse WH, Aubry M, et al. Consensus statement on concussion in sport: the 4th international conference on concussion in sport held in Zurich, November 2012. Br J Sports Med 2013; 47:250-258.
- American Academy of Neurology. Editor’s note to author’s and readers: levels of evidence coming to Neurology. Internet. http://www.neurology.org/site/misc/NeurologyFiller.pdf. Accessed July 10, 2015.