Clinical journal of sport medicine : official journal of the Canadian Academy of Sport Medicine
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To assess predictive value of concussion signs and symptoms based on return-to-play timelines. ⋯ When evaluating concussion, symptoms of headache >3 hours, difficulty concentrating >3 hours, retrograde amnesia, or loss of consciousness may indicate a more severe injury or prolonged recovery; great caution should be exercised before returning these athletes to play.