Concussion: a primer for the physician.

1This is best demonstrated in athletes, a population of patients at greatest risk for repeated head injuries. In fact, concussions are the most common head injury sustained by athletes; 8.9% of all high school sports injuries reported are concussions and account for 19% of all non-fatal injuries in football. 2 The incidence of concussion among American teen athletes has grown from 300,000 incidents annually 10 years ago to upward of three million cases now. The increase is likely due to the increased awareness by the sports community, leading to greater recognition and reporting. It is unclear if changes in rules and protective equipment has changed incidence. Nonetheless, these figures underestimate the frequency of concussions, as those with minor head injuries are often unlikely to seek care. In a survey by the Associated Press in 2009, 3 it was found that at the professional level, nearly one-fifth of 160 NFL players had hidden or downplayed the effects of their concussions. Athletes fear being removed from play and letting teammates down. Coaches, sideline personnel, and athletes themselves often do not recognize their own symptoms as a concussion. According to a McGill University study, 70.4% of athletes surveyed retrospectively reported experiencing the symptoms of a concussion during the past year, but only 23.4% realized that they had sustained a concussion in real time. 4 The study also found that 84.6% of athletes with a concussion had actually experienced more than one concussion. Part of the dilemma in diagnosing concussions is that the definition itself has been evolving. At this time, the most accepted definition of con cussion is a clinical one, introduced in 2001. 5