Football-induced head injuries have been a public health issue since 1905, when President Theodore Roosevelt threatened to outlaw the sport after 18 college athletes were killed or paralyzed during the playing season. The National Collegiate Athletic Association (NCAA) sprang into being, in part to reduce the danger of the sport. The NCAA safety strictures, however, do not govern high school athletics. According to a Cleveland Clinic study, 47.2% of high school-aged football players suffer at least one concussion. Many of these players are being sent back into the game too soon, and more than one third suffer multiple concussions during their high school years.

The Cleveland Clinic study, by Wayne Langburt, MD, and colleagues, found that most concussions were low grade, most players did not stop play even for brief periods, and players with a history of previous concussion had an increased risk of subsequent head injury. This is particularly worrisome in light of previous work by Michael Collins, PhD. Dr. Collins, now with the University of Pittsburgh Medical Center Sports Medicine Concussion Program, and colleagues showed that players with a history of multiple concussions were at risk for developing the kind of cognitive disorders that interfere with academic performance. Those with concussion plus a preexisting learning disability were especially vulnerable.

THE RULING ON THE FIELD

Dr. Langburt’s study surveyed 450 high school players, 52% of whom completed a three-page questionnaire. The survey did not use the word “concussion.” Instead, players were asked about symptoms corresponding with the guidelines for mild traumatic brain injury proposed by Robert C. Cantu, MD, from the Department of Neurosurgery Service, Emerson Hospital, Concord, Massachusetts. According to Dr. Cantu’s standards, a grade 1 concussion denotes mild injury with no loss of consciousness and post-traumatic amnesia lasting less than 30 minutes. Grade 2 is a moderate injury with loss of consciousness of less than five minutes and post-traumatic amnesia lasting more than 30 minutes. Grade 3 is a severe injury with loss of consciousness lasting more than five minutes and post-traumatic amnesia lasting more than 24 hours. Players were also asked about the presence and duration of symptoms occurring after a head injury, such as headache, dizziness, diplopia, difficulty with speech or concentration, and memory impairment.

Of the 233 players reporting, 110 (47.2%) had at least one concussion, and almost three quarters of those players reported multiple concussions; the majority (88%) were mild in nature. Nearly 10% of the reported concussions were grade 2, and 2.4% were grade 3. “If Dr. Cantu’s guidelines had been rigorously observed, at least 50% of players with concussions would have had to stop play for one week or more,” Dr. Langburt said. Despite this, 68% of the players with concussions did not stop playing at all, and only 12 of 110 (11%) stopped playing for more than one practice or game.

“This study was done to document the number of concussions occurring, and not the neuropsychological effects. Nonetheless, players may be at risk for future neuropsychologic problems. We still do not know if repeated, mild injuries cause damage, particularly if they are separated by long periods of time.” Dr. Langburt is now in private practice at Pediatric Neurology, SC, in Lake Bluff, Illinois.

The study conducted by Dr. Collins and colleagues, lends additional academic weight to these findings. Of 393 college football players, 34% had one previous concussion and 20% had two or more. Quarterbacks and tight ends had the highest rates of prior concussion (68% and 65%, respectively). Players with either multiple concussions or learning disorders had worse neuropsychologic performance than did matched control athletes on standard tests. Those with both a history of concussions and a learning disorder did significantly worse on the Trail-Making Test and on the Symbol Digit Modalities Test.

While players with a history of only one concussion had no long-term cognitive dysfunction, performance on neuropsychologic tests declined as the number of concussions increased. “It is logical to assume that the cognitive domains selectively affected ... are prerequisites for academic success. Thus, academic achievement may become even more difficult for these athletes,” Dr. Collins said.

A QUESTIONABLE CALL?

Dr. Langburt’s use of concussion criteria that do not require loss of consciousness conforms to standards as codified in current American Academy of Neurology (AAN) guidelines. These criteria are also supported by work on the physiology of concussion pioneered by David Hovda, MD, and colleagues at the University of California, Los Angles School of Medicine. Joseph C. Maroon, MD, of the Pittsburgh Steelers Football Organization explained why.

According to Dr. Maroon, a percussive injury to the neuron causes a rapid release of intracellular potassium. Loss of consciousness occurs only when the level of extracellular potassium rises above the physiologic limit of 4 to 5 mmol/L to levels of 20 to 50 mmol/L. However, injury-mediated potassium release triggers the release of glutamate, which can lead to further calcium-mediated neuronal injury even if it does not cause loss of consciousness. Time is required for this potassium efflux, which is why players sometimes do not experience confusion or amnesia until several minutes after an injury.

In an attempt to correct the abnormal ion fluxes, the body amplifies metabolic processes. This stage is powered by a surge in glycolysis beginning about 10 minutes after injury. Decreased cerebral blood flow, lactate accumulation, and intracellular acidosis result. This hypometabolic state persists for up to 10 days, during which protein synthesis and neuronal oxidative capacity drop. “As a consequence, [during this period] cells that are rendered vulnerable but still viable after a concussive injury may die after a second sublethal insult,” Dr. Maroon and colleagues reported. This is thought to be the mechanism behind the rare but sometimes fatal second impact syndrome.

Douglas B. McKeag, MD, senior author of Dr. Collins’ study, believes that baseline neuropsychologic data should be collected on all high school and college football players as part of the preseason physical and that additional testing should follow any possible mild traumatic brain injury. “This can help us return an athlete to play more quickly as well as prevent players from returning too soon,” said Dr. McKeag, who is Director of the Indiana University Center for Sports Medicine in Indianapolis.

Dr. Langburt agreed in principle but said that such an approach is difficult to implement. “Especially at the high school level, we run into the problem of who would pay for this extra half hour of testing and who would do the baseline tests,” he said. Until evidence-based standards can be established, Dr. Langburt advises team physicians, coaches, and trainers to adhere to AAN guidelines on when athletes should return to play.

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