Most concussion and return-to-play guidelines issued before 2000 use numeric grading scales and rely on the presence/absence of loss of consciousness (LOC) and post-traumatic amnesia (PTA) to determine the severity of a concussion and return to play (RTP).
None gained universal acceptance or were consistently followed by sports medicine professionals, many of whom ended up not using any grading scale for evaluation or RTP purposes.
Most concussion management guidelines issued since 2000 move away from reliance on LOC and PTA as sole predictors of injury severity. They focus instead on the number and duration of all concussion signs and symptoms, and recognize that severity of injury can only be determined after those signs and symptoms have cleared.
This new approach was best exemplified by the consensus statement issued in 2005 after the 2nd International Conference on Concussion in Sport in Prague. Instead of classifying concussions by grade (Grade 1=mild, Grade 2=moderate, Grade 3=severe), the Prague statement classified concussion as either simple or complex, depending on the type, duration and number of symptoms and how long they took to resolve:
- Simple concussions (the most common form covering 80-90% of all concussions) were those that progressively resolved without complications over seven to ten days,
- A concussion was classified as complex if (a) certain post-concussive symptoms such as convulsions or extended loss of consciousness were present, or (b) symptoms such as cognitive impairment persisted beyond 10 days, (c) the athlete has a history of previous concussions, and/or where repeated concussions occurred with progressively less impact force.
Some experts, even those who participated in the drafting of the Prague statement, did not agree with its approach, concerned that describing any concussion, even one with symptoms that cleared within 10 days, as "simple" as unwise.
Zurich Consensus Statement
Just four years later, a group of concussion experts meeting in Zurich, adopted the minority position of the Prague experts, reaching a new consensus, one which considers concussions in sport as a single entity with a range of "modifying factors" instead of being classified as "simple" or "complex." The new consensus statement issued after the 3rd International Conference on Concussion in Sport (Zurich statement) thus abandoned the classification terminology of the Prague group.
National Athletic Trainers' Association
In a position statement on the
management of sport-related concussion published in the September 2004
issue of The Journal of Athletic Training, the National Athletic
Trainers Association (NATA) refused to endorse any of the three
approaches to concussion management, but recommended that certified
athletic trainers and team physicians, at the very least, "agree on a
philosophy for managing sport-related concussions before the start of
the athletic season," and, after deciding on an approach, "be
consistent in its use regardless of the athlete, sport, or
circumstances surrounding the injury."
American College of Sports Medicine
In its 2006 consensus statement on concussion and the team physician, the American College of Sports Medicine (ACSM), while falling short of an unqualified endorsement of the Prague concussion management approach, appeared to endorse its broad outlines in determining severity retrospectively (e.g. after all post-concussion signs and symptoms had cleared) and use of "progressive aerobic and resistance exercise training tests before full" return-to-play (RTP).
The ACSM consensus statement appears to reject earlier guidelines (Colorado and AAN) that focused heavily on loss of consciousness and retrograde amnesia (RGA) and to endorse the retrospective approach of the Cantu revised and Prague guidelines in viewing an approach to the return-to-play decision that considered "RGA, PTA, as well as the number and duration of additional signs and symptoms" as "more accurate in predicting severity and outcome ¡ [and hence] more useful," and by endorsing an individualized RTP decision, not one "based on a rigid timeline" [like the Colorado, AAN and Cantu Revised Guidelines)