In the article on concussion in sports in this issue of American Family Physician,¹ Harmon highlights many important issues related to the evaluation and treatment of concussion (mild traumatic brain injury; MTBI) in young athletes. This injury, which is common in athletes involved in contact and collision sports, has received increasing attention in recent years. Media reports about prominent professional athletes who have sustained concussions have highlighted the relative paucity of scientific data on this topic and have stimulated research. Still, a number of controversial issues remain.

First, accurate information regarding the incidence of concussion is elusive because of variations in the definition of injury, and intentional and unintentional underreporting by athletes. Second, many concussion severity scales have been proposed. Concussion grading schemes are based on the presence and duration of signs and symptoms, unlike common grading schemes for musculoskeletal injuries which have a known pathophysiologic correlate.¹ Unfortunately, these signs and symptoms do not have a known pathophysiologic correlate. Thus, grading systems are based on an experienced author's arbitrary grouping of signs and symptoms, and their duration. Presenting signs and symptoms do not predictably correlate with concussion severity and duration. An athlete who loses consciousness for a few seconds may be asymptomatic in a few minutes, while another who sustains no loss of consciousness may be symptomatic for days.

Third, one of the biggest clinical challenges is how to advise athletes about return to play. There is general agreement that the athlete should be symptom-free before returning to a high contact or collision activity. However, the clinician should be aware that, in order to continue to play, athletes will tend to minimize or deny symptoms. It can be difficult to evaluate subjective symptoms. In our experience, if the athlete is still symptomatic from the concussion but is denying symptoms, the mental status examination will reveal cognitive problems (e.g., impaired memory, concentration or information processing) that the athlete will not be able to hide.

If an athlete who sustains a mild concussion is not able to return to play in the same day, we propose a “functional” approach in determining when an athlete should return to play. This approach differs somewhat from the mandatory rest recommended by published guidelines but differs little in practicality. When the symptoms of concussion resolve (one to two days on average in our experience),² we allow noncontact activity (running, biking, lifting) for two days. If there is no return of symptoms, the athlete is cleared to play. Thus, in the typical scenario, an athlete with an uncomplicated concussion is cleared for full activity five to six days after the injury.

Recommendations for patients with recurrent concussion are problematic. Published guidelines exist based on the authors' experiences. We agree that recurrent injury (e.g., a second concussion in a season, or a third or fourth concussion in a career) mandates a longer period of asymptomatic rest (usually one to two weeks), but data are lacking to substantiate this intuition.

An important development in the evaluation of concussion is the use of neuropsychologic testing. This testing is a sensitive tool for the cognitive and neurophysiologic dysfunction that occurs in mild traumatic brain injury. In the past few years, experts have been using modified tests in sports medicine.³ These tests take as little as 10 to 20 minutes. They are becoming important tools in the evaluation and management of concussion. The tests can provide important objective information about subtle cognitive deficits that may occur as a result of repeated concussion. Although research about the role of neuropsychologic tests is ongoing, we are starting to use this modality more often, especially in athletes who have a history of repeated concussion or in those who may have symptoms suggestive of chronic postconcussive syndrome.

Finally, the clinical entity known as second impact syndrome is somewhat controversial. The typical clinical scenario has been described by Cantu⁴ and others. In a recent review, McCrory⁵ raises questions about the existence of second-impact syndrome as it has been defined by Cantu and others. Cantu describes second-impact syndrome as “a syndrome of severe brain swelling occurring after minor head trauma in individuals who have symptoms from a prior head injury.”⁴ In our own review of published cases, we note that autopsy results in some subjects identified a cerebral contusion or “clinically insignificant” hematoma that apparently correlates with the “initial” impact. Thus, in some cases, the first impact might be more than a concussion. These rare but tragic cases have provided the impetus for many of the published return-to-play guidelines.

It is interesting to note that most cases of second-impact syndrome involve adolescent athletes. In addition, malignant cerebral edema secondary to head trauma has been described in the pediatric literature. Because no second-impact syndrome has been reported in the National Football League and National Hockey League, might there be a vulnerability in the young brain that diminishes with age? Many controversial issues remain in the diagnosis and treatment of concussions. Because this is an area of public interest and research, many of the clinical questions are being addressed in current studies.