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Concussion Grading Scales Abandoned

Symptom-based, individual approach now guides return to play

Historically, concussions were "graded."  The three most commonly used concussion grading systems were the Cantu,1 Colorado Medical Society (CMS),2 and the American Academy of Neurology (AAN)3 guidelines.4   Neurons in brain firing

The CMS and AAN measured concussion severity and assigned a "grade" to the concussion at the time of injury. Both emphasized loss of consciousness (LOC) and post-traumatic amnesia (PTA) over other post-concussion symptoms.

The Cantu Grading System, developed by MomsTeam concussion expert emeritus, Robert C. Cantu, M.D., placed less weight on LOC as a potential predictor of subsequent impairment and additional weight on the overall persistence of post-concussion symptoms, assigning a grade to the injury only after the athlete is symptom-free.

Here's how the three concussion grading scales compared:

Concussion GradeCantu Grading System (2001 Revision) 1991 Colorado Medical Society Guidelines1997 American Academy of Neurology (AAN) Guidelines
Grade 1 (mild)
  • No (LOC)
  • Either PTA or post-concussion signs and symptoms that clear in less than 30 minutes
  • Transient mental confusion
  • No PTA
  • No LOC
  • No LOC
  • Transient confusion
  • Post-concussion symptoms clear in less than 15 minutes
Grade 2 (moderate)
  • LOC lasting less than 1 minute and PTA or
  • Post-concussion symptoms lasting longer than 30 minutes but less than 24 hours
  • No LOC
  • Confusion with PTA
  • No LOC
  • Post-concussion symptoms last more than 15 minutes
Grade 3 (severe)
  • LOC lasting more than 1 minute or
  • PTA lasting longer than 24 hours or
  • Post-concussion signs or symptoms lasting longer than 7 days
  • Any LOC, however brief
  • Any LOC, either brief (seconds) or prolonged (minutes)

No same-day return to play

Historically, LOC was thought to be a hallmark of a more serious, severe concussion, with athletes who lost consciousness at the time of their concussion receiving a higher "grade" under these grading systems than those that did not, and athletes who were knocked unconscious for longer periods of time receiving higher grades than those who were unconscious for shorter periods of time.  These grades were used to determine how long an athlete should be removed from sports after sustaining a concussion. 

A decade ago, young athletes who suffered what the old grading scales would have considered "mild" or Grade 1 concussions would have been routinely allowed return to sports in as little as 15 minutes (Cantu) to 30-minutes (AAN) after his or her symptoms were thought to have cleared.

Individualized concussion assessment

Extensive research on sport-related concussion since 1999, however, has provided medical professionals with a much better understanding of the symptomatic course and risk of potential long-term complications, even death, from allowing a youth athlete to return before his concussion has been fully evaluated away from the sports sideline.  

Clinicians involved in the assessment and management of sport-related concussions began to notice that athletes who were knocked unconscious for brief periods of time often recovered more quickly than those who did not lose consciousness at all.  Therefore, it seemed inaccurate to diagnose those who did not lose consciousness with a lower grade of concussion.  Furthermore, grades were used to determine the period of time that an athlete was removed from sports.  It did not make sense to keep those who recovered more quickly out of sports for longer periods of time than those who recovered more slowly.  

For this and for several other reasons, the use of these grading systems has been abandoned in favor of a symptom-based, "multi-faceted approach to concussion management that emphasizes the use of objective assessment tools aimed at capturing the spectrum of clinical signs and symptoms, cognitive dysfunction and physical deficits,"10 and a symptom-limited, graduated exercise protocol leading to a return to play.5,6,8

Nowadays, when making decisions to return an athlete back to play after he or she has recovered from a sport-related concusion, doctors consider each case individually, taking all factors into consideration in helping to determine the amount of time an athlete is asked to remain symptom free before returning to contact, although  prolonged LOC and anterograde amnesia are still considered red flags for concussion and factors that may modify concussion management) under recent international consensus statements.5,6,8

The universal trend (including, as of March 2013, the American Academy of Neurology9) has thus been strongly against alllowing athletes to return to the same game or practice no matter how quickly their symptoms appear to clear, and in favor of a conservative and gradual return of an athlete to sports only when symptoms have cleared not only at rest but with exertion and their neurocognitive function and balance have returned to its pre-injury baseline, and any academic accomodations for the concussed athlete have been discontinued. The no same-day-return-to-play rule is now reflected in laws enacted in 48 of the 50 states and the District of Columbia. 

Grading systems had value

"While grading systems have been abandoned in favor of more individualized management," writes Dr. William P. Meehan III, MomsTeam concussion expert and Director of the Sport Concussion Clinic at Children's Hospital Boston in his 2011 book, Kids, Sports, and Concussion,7 "they were extremely beneficial during their time.  When the first grading systems were developed," he notes, "few medical professionals took concussions seriously. Athletes were often sent straight back into play after sustaining a concussion, without another thought."  Thus, Dr. Meehan writes, "these grading systems were instrumental in drawing much need attention to the issue of concussive brain injury in sports.  They allowed many athletes to recover from their injuries, prior to sustaining an additional concussion."


1. Cantu RC. Posttraumatic retrograde and anterograde amnesia, pathophysiology and implications in grading and safe return to play. J Athl Train. 2001;36(1):244-248.

2. Colorado Medical Society. Report of the Sports Medicine Committee: Guidelines for the Management of Concussions in Sport (Revised). Denver, CO: Colorado Medical Society; 1991.

3. American Academy of Neurology. Practice parameter: the management of concussion in sports (summary statement). Report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 1997;48(3):581-585.

4. Halstead, M, Walter, K. "Clinical Report - Sport-Related Concussion in Children and Adolescents"  Pediatrics. 2010;126(3):597-615.

5. McCrory P, Johnston K, Meeuwisse W, et al. Summary and agreement statement of the 2nd International Conference on Concussion in Sport, Prague 2004. Br J Sports Med 2005;39(4):196-2004.

6.  McCrory P, Meeuwisse W, Johnston K. et al. Consensus statement on Concussion in Sport: the 3rd International Conference on Concussion in Sport held in Zurich, November 2008.  Br J Sports Med 2009: 43:i76-i84.

7. Meehan WP. Kids, Sports, and Concussion (Praeger 2011) at 26. 

8. McCrory P, 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. 

9. Giza C, Kutcher J, Ashwal S et al.  Summary of evidence-based guideline update: Evaluation and management of concussion in sports: Report of the Guideline Development Subcommittee of the American Academy of Neurology.  (published online ahead of print, March 18, 2013); DOI:10.1212/WNL.ob013e31828d57dd (accessed March 24, 2013). 

10. Guskiewicz K, et al. Evidence-based approach to revising the SCAT2: introducing the SCAT3.  Br J Sports Med 2013;47:289-293. 

Updated and revised July 12, 2014

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