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Abstract & Commentary
Synopsis: Initial and follow-up assessments of post-traumatic amnesia are an essential part of the neurologic evaluation of the head-injured athlete.
Source: Cantu RC. Journal of Athletic Training. 2001;36(3):244-248.
In 1986, Cantu proposed what has become the most widely used practical scheme for grading concussion severity in athletes based on duration of unconsciousness or post-traumatic amnesia (PTA).1 In this current article, he proposes an evidence-based modification of the original Cantu guidelines using retrograde and especially anterograde PTA as a criterion to be used for grading of concussion severity.
PTA may be divided into either retrograde or anterograde amnesia. Retrograde amnesia is the partial or complete loss of the ability to recall events that occurred immediately prior to the concussion. Anterograde amnesia is a deficit in the ability to form new memory after the injury. Retrograde amnesia may be assessed on the field by asking questions related to score, mechanism of injury, and names of current and recent opponents. Anterograde amnesia may be assessed by repeating 4 words immediately and 2 minutes later, repeating 5 numbers forward and backward, and repeating months of the year backward. Sophisticated tests of sideline mental status testing are available and useful for assessment of concussion.2
The original Cantu scheme proposed 3 grades of concussion based on duration of unconsciousness or PTA, or both. The grade 1 concussion occurs without loss of consciousness with only a brief period of PTA, which by definition lasts less than 30 minutes. The grade 2 concussion is associated with unconsciousness lasting less than 5 minutes, and/or PTA lasting more than 30 minutes but less than 24 hours. A grade 3 concussion occurs with loss of consciousness longer than 5 minutes, and/or PTA lasting more than 24 hours.
The new, evidence-based modification of the original Cantu scheme also uses a 3-grade classification system for concussion. Grade 1 (mild) concussion includes: no loss of consciousness; and PTA or postconcussion signs or symptoms lasting less than 30 minutes. A grade 2 (moderate) concussion is associated with: loss of consciousness lasting less than 1 minute; and PTA or postconcussion symptoms lasting longer than 30 minutes but less than 24 hours. The grade 3 (severe) concussion includes: loss of consciousness lasting more than 1 minute or PTA lasting longer than 24 hours; and postconcussion signs or symptoms lasting longer than 7 days. For all 3 grades, PTA is retrograde and anterograde.
COMMENT BY DAVID H. PERRIN, PhD, ATC
At least 15 grading systems for concussion exist and use state of consciousness and magnitude of PTA for severity classification. There is not complete agreement among these systems, and Cantu points out that there is also not universal agreement that PTA is a better or more sensitive predictor of outcome after concussion than assessment of unconsciousness.
Cantu’s modified guidelines are based on the fact that unconsciousness lasting longer than 5 minutes is almost never seen in athletic events and that most periods of unconsciousness last from seconds to a minute. Moreover, prospective studies over the past decade report a correlation between duration of postconcussive symptoms, PTA, and results of neuropsychological assessments. Cantu further explains that while not diminishing the importance of unconsciousness, "I find it illogical to grade a concussion that produces postconcussion symptoms lasting months or years without loss of consciousness as less severe than a concussion resulting in brief unconsciousness and resolution of all postconcussion symptoms within a few minutes or hours."
There is not universal agreement among the grading systems for concussion experienced during athletics. However, there is consensus that an athlete who has incurred an initial concussion has a greater chance of sustaining subsequent concussions. Moreover, there is agreement that an athlete should not be returned to play in the presence of PTA and any postconcussion symptoms at rest and with exertion.
This paper is 1 of 19 written by more than 30 international experts on neurological athletic mild head injury for a Journal of Athletic Training special issue on concussion in athletes. Physicians and other sports medicine clinicians involved in the care of athletes will find this issue invaluable for managing cases involving an athlete with concussion.
1. Cantu RC. Physician Sportsmed. 1986;14(10):75-83.
2. McCrea M. Journal of Athletic Training. 2001;36(3):274-279.