Sports Concussion

Introduction

A high profile athlete, a head injury and we reason about it in the sports pages. But for every professional athlete who experiences a sports concussion, there are many more amateur athletes, both adults and children, who don't make the papers. Still, head injury in sports is an important and timely medical topic, and this review will briefly cover aspects of sports concussion, including epidemiology, biomechanics, sports-related recurrent head injuries, and basic clinical management.

Epidemiology of Sports-Related Brain Injury

The majority of head injury in sports falls into the category of mild traumatic brain injury, also referred to as concussion. A concussion is defined as any biomechanically-induced impairment of neurological function, with or without loss of consciousness (American Academy of Neurology, 1997). Because of its mild nature, many sports concussions go unreported. In fact, a desire of the athlete with brain injury to quickly return to play often results in minimizing or ignoring the symptoms of concussion. The Centers for Disease Control estimate that 30,000 sports-related brain injuries occur annually in the United States, the vast majority of them concussions (Centers for Disease Control and Prevention, 1999). Of all traumatic brain injuries, 1 in 5 is incurred during sports participation.

Perhaps more compelling are the estimated rates of concussion among athletes in particular sports. Concussive head injuries account for a significant proportion of total injuries in contact sports. Collegiate ice hockey (12.2%), football (8%) and soccer (4.8%) all showed a significant percentage of concussions out of total injuries sustained during the 2002-2003 season, as reported by the National Collegiate Athletic Association (NCAA) Injury Surveillance System (McCrea, Guskeiwicz, Marshall et al, 2003). Similar results were reported in a study of athletes from 235 US high schools, where 5.5% of total injuries were mild traumatic brain injuries (Powell and Barber-Foss. 1999). This percentage was highest for football (7.3%), wrestling (4.4%) and soccer (3.9%) in boys' sports. In girls' sports, the percentage of concussions out of total reported sports injuries was highest in soccer (4.3%), Ice hockey was not assessed in the latter study. Among the 10 high school sports analyzed, however, it was estimated that over 60,000 mild head injuries occur annually in varsity high school athletes. This underlines the fact that many sports-related head injuries occur in children and adolescents, whose brain development is ongoing and where the effects of injury may be distinct from those seen in adults.

Most persons are able to recover completely from concussions. While a single mild injury may not result in lasting cognitive or behavioral deficits, an accumulation of injuries over time, or repeated injury with incomplete recovery between concussions, can have lasting effects (Collins, Lovell, Iverson, et al, 2002; DeFord, Wilson, Rice, et al., 2002; Guskiewicz, McCrea, Marshall et al., 2003) Guskiewicz reported that high school and college football players who sustained a concussion were three times more likely to suffer a second concussion the same season. More recently, Zemper showed that a previous concussion is associated with an almost overall 5.86-fold increased relative risk.