Traumatic Brain Injury and Concussion in Sports

The term traumatic brain injury (TBI) was introduced into federal law by the Traumatic Brain Injury Act of 1996.¹ It is quite possible that many physician-readers of THE JOURNAL are being introduced to the term TBI as a medical diagnosis for the first time, since most US medical schools probably have not included lectures on this topic or used this term in their required courses. In fact, it may come as a surprise to some physicians that 1 million new cases of TBI occur in the United States each year, with more than 50,000 deaths and 70,000 to 90,000 persons developing long-term disability, as reported by Thurman and Guerrero.² These data indicate that the incidence of TBI exceeds the annual incidence rates of the more well-established neurological diagnoses of multiple sclerosis,³ Parkinson disease,⁴ and Alzheimer disease⁵ combined. And yet only recently has the attention of the medical community been drawn to TBI, which Goldstein referred to as "a silent epidemic" nearly a decade ago.⁶

Even though the science of TBI is relatively new compared with many other areas of medicine, much is known about its biomechanics and pathophysiology. Severe TBI is often associated with cerebral contusions as well as intracerebral, subdural, and epidural hematomas, which may present as neurosurgical emergencies.⁷ Increased levels of the excitotoxin glutamate have been detected in association with reduced cerebral perfusion pressure in humans after TBI.⁸ Hyperglycolysis occurs as a pathophysiological response to ionic and neurochemical cascades following TBI.⁹ The anatomical common denominator in TBI is the production of diffuse axonal injury¹⁰ and damage to the neuronal cytoskeleton.¹¹ The cholinergic neurons of the brain are apparently more vulnerable to trauma than other neurotransmitter systems,¹² and memory dysfunction is associated with selective hippocampal neural pathology.¹³ Genetic factors also may play a role in TBI, as the apolipoprotein E4 allele appears to be associated with increased severity of chronic neurological deficits in boxers.¹⁴

Moreover, in an effort to offer uniformity to the management of brain swelling and other sequelae of trauma, a joint initiative of the Brain Trauma Foundation, the American Association of Neurological Surgeons, and the Joint Section on Neurotrauma and Critical Care has produced Guidelines for the Management of Severe Head Injury,¹⁵ which have been widely disseminated nationally and internationally.

An estimated 300,000 cases of TBI occur each year in the setting of sports and recreation.¹⁶ In this issue of THE JOURNAL, Powell and Barber-Foss¹⁷ report rates of concussion in high school athletes, finding that football accounts for the highest proportion of mild TBI, or concussion. (The terms concussion and mild TBI are used interchangeably as is consistent with the US medical literature.) These head injury data were gathered by certified athletic trainers who are the front-line health care professionals for most scholastic sports and have the highest likelihood of observing a concussion as it occurs and examining the injured athlete during the immediate effects of the concussion. Since the rates of concussion for sports at high school¹⁷ and collegiate levels¹⁸ of competition are known, it is possible to predict the need for evaluation of athletes engaged in those activities. Observing the "natural occurrence" of concussion in sports provides the opportunity to examine how concussion occurs and describe its neurobehavioral manifestations. The intended result of this approach is a reduction in morbidity¹⁹ and mortality²⁰ associated with concussion through early detection, careful monitoring, and prevention.

Guidelines for the diagnosis and management of concussion in sports,²¹ published by the American Academy of Neurology and supported by the Brain Injury Association, evolved from the basic sciences and consensus of specialists in the clinical neurosciences and sports medicine.²² The Standardized Assessment of Concussion²³ provides physicians and athletic trainers with a rapid and simple sideline evaluation instrument for assessing athletes with concussion. This method helps avoid the premature return of the injured athlete to competition and improves on the previously idiosyncratic fashion of assessing the effects of concussion used by physicians, athletic trainers, and coaches when no medical personnel are available. However, sideline assessment alone is not intended to replace neurological examination by a physician or more detailed and sensitive neuropsychological testing in those with concussion.

The occurrence of severe neurological injury in sports is not a new phenomenon. The National Collegiate Athletic Association (NCAA) was formed earlier this century partially in response to President Theodore Roosevelt's indignation over the 19 college athletes who were killed or paralyzed playing football in 1904.²⁴ His influence helped catalyze the creation of the NCAA as a rule-making body with the mandate of making athletic competition safer at the amateur level. The article by Collins and colleagues²⁵ in this issue of JAMA brings into focus the highly sensitive assessment approach of neuropsychological testing in college football players. Building on earlier reports of the use of selected neuropsychological tests in athletes with concussion,²⁶ the investigators report that this approach is useful for assessing the cognitive deficits caused by concussion. In addition, the authors found that a history of learning disability or multiple concussions can result in poor outcome, and the combination of these 2 factors may be "detrimentally synergistic."²⁵

Concern about the potential for cumulative and long-term effects of repeated concussions led Matser and colleagues²⁷ to perform neuropsychological tests on amateur soccer players and control athletes engaged in track and swimming. Finding results similar to their study of professional soccer players,²⁸ these authors conclude that amateur soccer players perform significantly more poorly than control athletes on tests of cognition involving attention, memory, and planning abilities. However, the study cannot answer whether repeatedly "heading" the soccer ball is injurious to the brain.²⁹ Given the finding reported by Powell and Barber,¹⁷ it seems likely that concussion in amateur soccer typically occurs when players collide with each other or immovable objects such as goalposts and the ground rather than while heading the ball.

Despite increased efforts to educate medical professionals and the public about TBIs, misinformation about concussion continues to appear in medical textbooks³⁰ and publications intended for family members of persons with TBI.³¹ There is a longstanding misconception that an individual must be rendered unconscious to have sustained a brain injury. Literature available prior to 1964 led the Congress of Neurological Surgeons to conclude that TBI can occur without loss of consciousness.³² Concussion should be defined as a trauma-induced alteration in mental status that may or may not involve loss of consciousness.²¹

As the study by Collins et al²⁵ demonstrates, the majority of concussions in sports occur without loss of consciousness. While the effects of concussion usually resolve spontaneously and fully, some individuals have persistent symptoms and cognitive deficits. It is especially important to determine which individuals remain symptomatic following concussion so they can be treated properly and protected from additional concussions that may have long-lasting or catastrophic outcomes.^{21 ,33}

The Traumatic Brain Injury Act of 1996 also called for a "national consensus conference on managing traumatic brain injury and related rehabilitation concerns." This issue of THE JOURNAL carries the consensus statement¹ of the 1998 conference hosted by the National Institutes of Health. A panel of experts was convened to develop the consensus statement following months of reviewing the literature and hearing testimony from investigators addressing specific questions regarding TBI as well as testimony from members of the audience attending the public session. Among the panel's conclusions were that TBI is a major public health problem; mild TBI is significantly underdiagnosed and often neglected by the medical community; rehabilitation services are required to optimize outcome from TBI; and family members, significant others, and persons with TBI should be integrated into the rehabilitation process with funding adequate to meet their acute and long-term needs.

The panel's review of the medical literature found that the highest incidence of TBI is among persons aged 15 to 24 years, with a second peak at 75 years and older. Approximately 50% of TBI in the United States results from motor vehicle, bicycle, or pedestrian-vehicle incidents, with violence as the cause of approximately 20%.¹ An estimated $9 to $10 billion is spent annually on acute care and rehabilitation of persons with TBI.¹ This represents only a small portion of the overall costs associated with caring for someone with permanent neurological disability. There is a huge burden placed on family members who are thrust into the role of long-term care providers³⁴ often without the benefit of financial support from insurance or governmental sources. Perhaps saddest of all is the loss of the person as he or she was prior to the injury.

This issue of THE JOURNAL fosters public and professional discussion of the topic of TBI. Readers will come away with a heightened awareness of the risks of TBI due to participation in sports and recreation and the obligation of health care professionals to prevent and treat this potentially devastating neurological injury. Those who serve as athletic team physicians or as consultants for determining readiness of athletes to return to competition after TBI should develop a better appreciation of the consequences of concussion and more severe forms of TBI. Health care professionals engaged in the acute care and rehabilitation of persons with TBI should be encouraged by the increasing national and international attention this vexing human condition has long deserved.