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Multiple traumas to the brain are the most common type of catastrophic injury and a leading cause of death in athletes. Multiple brain injuries may occur as the long-term disabilities resulting from a single mild traumatic brain injury (MTBI, generally known as concussion) are often overlooked and the most obvious clinical symptoms appear to resolve rapidly. One of the reasons of controversy about concussion is that most previous research has: a) failed to provide the pre-injury status of MBTI subjects which may lead to misdiagnosis following a single brain injury of the persistent or new neurological and behavioral deficits; b) focused primarily on transient deficits after single MTBI, and failed to examine for long-term deficits and multiple MTBI; c) focused primarily on cognitive or behavioral sequelae of MTBI in isolation; and d) failed to predict athletes at risk for traumatic brain injury. It is necessary to examine for both transient and long-term behavioral, sensory-motor, cognitive, and underlying neural mechanisms that are interactively affected by MTBI. A multidisciplinary approach using advanced technologies and assessment tools may dramatically enhance our understanding of this most puzzling neurological disorder facing the sport medicine world today. This is a major objective of this chapter and the whole book at least in part to resolve existing controversies about concussion.

Cerebral concussion is both the most common and most puzzling type of traumatic brain injury (TBI). In this review brief historical data and theories of concussion which have been prominent during the past century are summarized. These are the vascular, reticular, centripetal, pontine cholinergic and convulsive hypotheses. It is concluded that only the convulsive theory is readily compatible with the neurophysiological data and can provide a totally viable explanation for concussion. The chief tenet of the convulsive theory is that since the symptoms of concussion bear a strong resemblance to those of a generalized epileptic seizure, then it is a reasonable assumption that similar pathobiological processes underlie them both. According to the present incarnation of the convulsive theory, the energy imparted to the brain by the sudden mechanical loading of the head may generate turbulent rotatory and other movements of the cerebral hemispheres and so increase the chances of a tissue-deforming collision or impact between the cortex and the boney walls of the skull. In this conception, loss of consciousness is not orchestrated by disruption or interference with the function of the brainstem reticular activating system. Rather, it is due to functional deafferentation of the cortex as a consequence of diffuse mechanically-induced depolarization and synchronized discharge of cortical neurons. A convulsive theory can also explain traumatic amnesia, autonomic disturbances and the miscellaneous collection of symptoms of the post-concussion syndrome more adequately than any of its rivals. In addition, the symptoms of minor concussion (i.e., being stunned, dinged, or dazed) are often strikingly similar to minor epilepsy such as petit mal. The relevance of the convulsive theory to a number of associated problems is also discussed.

Concussions are a frequent occurrence in athletic endeavors, its rate exceeding that occurring in the general population by 50 fold. The biomechanics and pathophysiology of concussion are still not well understood and may lead to potential significant sequelae from single or more commonly multiple concussions. Postconcussive symptoms, the second impact syndrome and the cumulative effects of concussions are all topics of interest in current concussion research in athletes and are leading to a more rational approach in determining policy aimed at returning athletes to their sport after a concussion. This chapter reviews current knowledge on the mechanisms, pathophysiology and sequelae of concussion in athletes.

Sport-related concussion is still considered by many as a hidden epidemic in sports medicine. Despite the fact that this condition is not visible by neuroimaging, current research has allowed clinicians to better understand the condition. This chapter will discuss sport-related concussion in the context of the biomechanics and pathomechanics involved with injury. We will further explore how historical studies of concussion-related biomechanics research have paved the way for more novel, technologically advanced mechanisms by which head injury mechanics can be studied.

The major objective of this chapter is to elaborate on the importance of comprehensive assessment and development of a robust grading system to identify concussion and to predict athletes at risk for brain re-injury due to premature return to sport participation. There is a growing body of knowledge accumulating in the literature and in clinical practice indicating the danger of long-term residual dysfunctions in athletes suffering from even single mild traumatic brain injury. It should be noted that several position statements elaborated by the mutual effort of numerous prominent leaders in this field have been recently proposed. These documents in general, and my contribution to this book, in specific, may assist team physicians, athletic trainers and coaches in providing optimal care for athletes who have sustained a concussion. So, possible long-terms abnormalities should not be overlooked while assessing brain injured athletes at the site of injury and monitoring these athletes during their course of recovery. Overall, to accomplish this goal, the medical professionals shouldhave knowledge of and be involved with epidemiology, pathophysiology, evaluation/and treatment, post game-day evaluation/and treatment, diagnostic imaging, management principles, return-to-play criteria, complications of concussion, and prevention. Most importantly, one must understand that an athlete, while still symptomatic at either rest or exertion should not be allowed to return to competition. No athlete who has experienced loss of consciousness or amnesia should be allowed to go back into the event that same day. The general tenor is “if in doubt, sit them out . Additional factor that need to be considered is the athlete’s total concussion history; including the number and the severity of those prior concussions. Moreover, the temporal proximity of concussions and the severity of the blow causing the concussion need to be assessed. Minor blows causing serious concussions should make a physician more hesitant to return an athlete to competition. The exact mechanisms of both short term_and long lasting abnormalities in the brain’s functional, behavioral, cognitive abilities and many other overseen abnormalities as a result of concussion in athletes still remains to be elucidated. This chapter is complementary to other chapters in this book to fully realize the ongoing controversies and problems with evaluation and treatment of sport-related traumatic brain injuries.

This chapter presents a discussion of the evolution of neuropsychological testing of concussed athletes. The advantages of computerized assessment are presented, with special emphasis on the ImPACT test battery, a widely used instrument in clinical research and practice.

In recent years there has been a dramatic increase in the use of neuropsychological tests to evaluate the effects of concussion in competitive athletes and assist in return to play decisions. In this chapter, we focus on one factor that can limit the sensitivity of neuropsychological tests to concussion--practice effects. The data we present suggests that the HVLT-R, Trails B, Stroop 2, and SDMT are most susceptible to practice effects upon repeated administration. Nonetheless, we show that even for these tests, a majority of control athletes do not show significant practice effects after several administrations when the reliability of the measures and regression to the mean are controlled for. Still, the fact that a significant minority of athletes show practice effects on these tests should serve as a note of caution for interpreting these commonly used clinical neuropsychological tests post-concussion. In contrast to these test indices, the Stroop 1 and Trails A showed little evidence for practice effects even when administered several times. Because the Stroop 1 also showed evidence for sensitivity to concussion, it emerged as perhaps the best test in terms of combined resistance to practice effects and concussion sensitivity. In terms of return to play decisions, because we found that a negligible number of controls displayed evidence for reliable decline from baseline on all six test indices, the data we present in this chapter strongly suggest that when concussed athletes continue to show performance reliably below baseline performance at one-week post-concussion on any of the noted test indices, great caution should be exercised in recommending return to play. Additionally, any athlete who is still reliably below baseline on two of the test indices at one-week post-concussion should not return to play because residual persisting cognitive effects from the concussion are highly likely. Future work can extend this research by using larger samples, better matching on overall cognitive ability.

This chapter provides a review of the limited information that is available regarding the impact of motivation on the neuropsychological assessment of sports-related concussion. We first outline what is known about the impact of motivation on assessment by identifying how the impact that differential motivation on baseline and post-concussion evaluations may obscure the true cognitive deficits of concussion. Next, we provide a review of two studies which provide some direct empirical evidence for differential motivation in baseline and post-concussion testing. This is followed by a review of possible causative factors associated with poor baseline motivation including: personality style, lack of education, and active misrepresentation. Next, the possible methods for identification of athletes with poor motivation on testing are presented. This includes both the use of objective measures of motivation and the identification of testing patterns consistent with poor motivation. Finally, the chapter concludes with the identification that more empirical research on each of the covered topics is necessary.

Imaging modalities such as CT and magnetic resonance imaging (MRI) are powerful tools to detect and assess focal injury such as hemorrhagic lesions and edema and brain swelling in severe injury. However, acute and chronic injury at a cellular level is sometimes difficult to discern from normal features by anatomical imaging. Magnetic resonance spectroscopy (MRS) offers a unique non-invasive approach to assess injury at microscopic levels by quantifying cellular metabolites. Most clinical MRI systems are equipped with this option and MRS is thus a widely available modality. For the brain in particular, MRS has been a powerful research tool and has also been proven to provide additional clinically relevant information for several disease families such as brain tumors, metabolic disorders, and systemic diseases. The most widely-available MRS method, proton (^1H; hydrogen) spectroscopy, is FDA approved for general use and can be ordered by clinicians for patient studies if indicated. The findings obtained with MRS in concussion and more severe head trauma are heterogeneous, reflecting the different time after injury, degree of injury and different physiologic and pathologic response of the brain to injury in individuals. The most important findings are that elevated lactate (and lipids) in apparently normal tissue observed 2–5 days after injury are indicators of severe global hypoxic injury and poor outcome. Also, N-acetylaspartate (NAA), a marker for “healthy” neurons and axons, is generally reduced in traumatic brain injury signaling neuronal and axonal loss/damage. The extent of NAA reduction after injury is an objective and quantitative surrogate marker for the severity of injury and is useful for outcome prediction.

The EEG in humans was first demonstrated by Hans Berger in the 1920s. His initial speculation that EEG could give us insight into physiological and cognitive processes has been validated in a variety of situations ranging from sleep to wakefulness as well as physiological concomitants of a variety of cognitive events. The current chapter will review basic EEG processes and present the background for understanding its usefulness in identification of changes related to motor processes in general and brain trauma, in specific.