The neuropsychiatric aspects of boxing

Professional fighters brain health study: rationale and methods

Repetitive head trauma is a risk factor for Alzheimer's disease and is the primary cause of chronic traumatic encephalopathy. However, little is known about the natural history of, and risk factors for, chronic traumatic encephalopathy or about means of early detection and intervention. The Professional Fighters Brain Health Study is a longitudinal study of active professional fighters (boxers and mixed martial artists), retired professional fighters, and controls matched for age and level of education. The main objective of the Professional Fighters Brain Health Study is to determine the relationships between measures of head trauma exposure and other potential modifiers and changes in brain imaging and neurological and behavioral function over time. The study is designed to extend over 5 years, and we anticipate enrollment of more than 400 boxers and mixed martial artists. Participants will undergo annual evaluations that include 3-tesla magnetic resonance imaging scanning, computerized cognitive assessments, speech analysis, surveys of mood and impulsivity, and blood sampling for genotyping and exploratory biomarker studies. Statistical models will be developed and validated to predict early and progressive changes in brain structure and function. A composite fight exposure index, developed as a summary measure of cumulative traumatic exposure, shows promise as a predictor of brain volumes and cognitive function.

What boxing tells us about repetitive head trauma and the brain

Boxing and other combat sports may serve as a human model to study the effects of repetitive head trauma on brain structure and function. The initial description of what is now known as chronic traumatic encephalopathy (CTE) was reported in boxers in 1928. In the ensuing years, studies examining boxers have described the clinical features of CTE, its relationship to degree of exposure to fighting, and an array of radiologic findings. The field has been hampered by issues related to study design, lack of longitudinal follow-up, and absence of agreed-upon clinical criteria for CTE. A recently launched prospective cohort study of professional fighters, the Professional Fighters Brain Health Study, attempts to overcome some of the problems in studying fighters. Here, we review the cross-sectional results from the first year of the project.

Absence of chronic traumatic encephalopathy in retired football players with multiple concussions and neurological symptomatology

Background: Chronic traumatic encephalopathy (CTE) is the term coined for the neurodegenerative disease often suspected in athletes with histories of repeated concussion and progressive dementia. Histologically, CTE is defined as a tauopathy with a distribution of tau-positive neurofibrillary tangles (NFTs) that is distinct from other tauopathies, and usually shows an absence of beta-amyloid deposits, in contrast to Alzheimer's disease (AD). Although the connection between repeated concussions and CTE-type neurodegeneration has been recently proposed, this causal relationship has not yet been firmly established. Also, the prevalence of CTE among athletes with multiple concussions is unknown.

Methods: We performed a consecutive case series brain autopsy study on six retired professional football players from the Canadian Football League (CFL) with histories of multiple concussions and significant neurological decline.

Results: All participants had progressive neurocognitive decline prior to death; however, only 3 cases had post-mortem neuropathological findings consistent with CTE. The other 3 participants had pathological diagnoses of AD, amyotrophic lateral sclerosis (ALS), and Parkinson's disease (PD). Moreover, the CTE cases showed co-morbid pathology of cancer, vascular disease, and AD.

Discussion: Our case studies highlight that not all athletes with history of repeated concussions and neurological symptomology present neuropathological changes of CTE. These preliminary findings support the need for further research into the link between concussion and CTE as well as the need to expand the research to other possible causes of taupathy in athletes. They point to a critical need for prospective studies with good sampling methods to allow us to understand the relationship between multiple concussions and the development of CTE.

Biomarkers of mild traumatic brain injury in cerebrospinal fluid and blood

Mild traumatic brain injury (TBI), which is defined as a head trauma resulting in a brief loss of consciousness and/or alteration of mental state, is usually benign, but occasionally causes persistent and sometimes progressive symptoms. Whether a threshold for the amount of brain injury and/or individual vulnerability might contribute to the development of these long-term consequences is unknown. Furthermore, reliable diagnostic methods that can establish whether a blow to the head has affected the brain (and in what way) are lacking. In this Review, we discuss potential biomarkers of injury to different structures and cell types in the CNS that can be detected in body fluids. We present arguments in support of the need for further development and validation of such biomarkers, and for their use in assessing patients with head trauma in whom the brain might have been affected. Specifically, we focus on the need for such biomarkers in the management of sports-related concussion, the most common cause of mild TBI in young individuals, to prevent long-term neurological sequelae due to concussive or subconcussive blows to the head.

The clinical spectrum of sport-related traumatic brain injury

Acute and chronic sports-related traumatic brain injuries (TBIs) are a substantial public health concern. Various types of acute TBI can occur in sport, but detection and management of cerebral concussion is of greatest importance as mismanagement of this syndrome can lead to persistent or chronic postconcussion syndrome (CPCS) or diffuse cerebral swelling. Chronic TBI encompasses a spectrum of disorders that are associated with long-term consequences of brain injury, including chronic traumatic encephalopathy (CTE), dementia pugilistica, post-traumatic parkinsonism, post-traumatic dementia and CPCS. CTE is the prototype of chronic TBI, but can only be definitively diagnosed at autopsy as no reliable biomarkers of this disorder are available. Whether CTE shares neuropathological features with CPCS is unknown. Evidence suggests that participation in contact-collision sports may increase the risk of neurodegenerative disorders such as Alzheimer disease, but the data are conflicting. In this Review, the spectrum of acute and chronic sport-related TBI is discussed, highlighting how examination of athletes involved in high-impact sports has advanced our understanding of pathology of brain injury and enabled improvements in detection and diagnosis of sport-related TBI.

The neuropathology and neurobiology of traumatic brain injury

The acute and long-term consequences of traumatic brain injury (TBI) have received increased attention in recent years. In this Review, we discuss the neuropathology and neural mechanisms associated with TBI, drawing on findings from sports-induced TBI in athletes, in whom acute TBI damages axons and elicits both regenerative and degenerative tissue responses in the brain and in whom repeated concussions may initiate a long-term neurodegenerative process called dementia pugilistica or chronic traumatic encephalopathy (CTE). We also consider how the neuropathology and neurobiology of CTE in many ways resembles other neurodegenerative illnesses such as Alzheimer's disease, particularly with respect to mismetabolism and aggregation of tau, β-amyloid, and TDP-43. Finally, we explore how translational research in animal models of acceleration/deceleration types of injury relevant for concussion together with clinical studies employing imaging and biochemical markers may further elucidate the neurobiology of TBI and CTE.

A Model of Current Best Practice for Managing Concussion in University Athletes: The University of Toronto Approach

Along with the ever growing awareness among the scientific community and the general public that concussion is a serious health care issue at all levels of sport, with potentially devastating long term health effects, the number of concussion surveillance clinical monitoring programs has significantly increased internationally over the past 10–15 years. An effective concussion program (a “best practice” model) is clinically prudent and evidence-based, one that is an interdisciplinary model involving health professionals who manage, educate, and provide psychosocial support to athletes. The integration of neuropsychological assessment is a component of many present day programs, and therefore, the neuropsychologist is an integral member of the concussion management team. The University of Toronto Concussion Program, operational since 1999, integrates best practices and current evidence into a working model of concussion management for university athletes. The model uses an interdisciplinary approach to monitor and assess athletes with concussions, as well as to educate its athletes, coaches, and administrators. A research component is also integral to the program.

Review: Contact sport-related chronic traumatic encephalopathy in the elderly: clinical expression and structural substrates

Professional boxers and other contact sport athletes are exposed to repetitive brain trauma that may affect motor functions, cognitive performance, emotional regulation and social awareness. The term of chronic traumatic encephalopathy (CTE) was recently introduced to regroup a wide spectrum of symptoms such as cerebellar, pyramidal and extrapyramidal syndromes, impairments in orientation, memory, language, attention, information processing and frontal executive functions, as well as personality changes and behavioural and psychiatric symptoms. Magnetic resonance imaging usually reveals hippocampal and vermis atrophy, a cavum septum pellucidum, signs of diffuse axonal injury, pituitary gland atrophy, dilated perivascular spaces and periventricular white matter disease. Given the partial overlapping of the clinical expression, epidemiology and pathogenesis of CTE and Alzheimer's disease (AD), as well as the close association between traumatic brain injuries (TBIs) and neurofibrillary tangle formation, a mixed pathology promoted by pathogenetic cascades resulting in either CTE or AD has been postulated. Molecular studies suggested that TBIs increase the neurotoxicity of the TAR DNA-binding protein 43 (TDP-43) that is a key pathological marker of ubiquitin-positive forms of frontotemporal dementia (FTLD-TDP) associated or not with motor neurone disease/amyotrophic lateral sclerosis (ALS). Similar patterns of immunoreactivity for TDP-43 in CTE, FTLD-TDP and ALS as well as epidemiological correlations support the presence of common pathogenetic mechanisms. The present review provides a critical update of the evolution of the concept of CTE with reference to its neuropathological definition together with an in-depth discussion of the differential diagnosis between this entity, AD and frontotemporal dementia.

F-18 FDG PET imaging of chronic traumatic brain injury in boxers: a statistical parametric analysis

PURPOSE

The participation in concussive susceptible sports such as boxing may cause chronic traumatic brain injury. The objective of this study was to determine whether there are unique patterns of reduced brain glucose metabolism in professional and amateur boxers.

METHOD

We compared the fluorine-18 fluorodeoxyglucose (F-18 FDG) PET brain scans of boxers (group) (N=19) with those of controls (group) (N=7) using both statistical parametric mapping and region of interest analysis.

RESULTS

Boxers showed decreased F-18 FDG uptake by 8-15% in the following brain areas: posterior cingulate cortex, parieto-occipito, frontal lobes (Broca's area) bilaterally, and the cerebellum (P<0.005) as compared with controls.

CONCLUSION

Our results suggest that F-18 FDG PET scans of boxers suspected of chronic traumatic brain injury show unique patterns of hypometabolism, and that these patterns may reflect the mechanisms of repeated traumatic brain injury unique to boxers.

Pathophysiology of sports-related concussion: an update on basic science and translational research

CONTEXT

Concussions that occur during participation in athletic events affect millions of individuals each year. Although our understanding of the pathophysiology of concussion has grown considerably in recent years, much remains to be elucidated. This article reviews basic science and relevant translational clinical research regarding several aspects of concussion.

EVIDENCE ACQUISITION

A literature search was conducted using PubMed from 1966 to 2010, with an emphasis on work published within the past 10 years. Additional articles were identified from the bibliography of recent reviews.

RESULTS

Basic science and clinical data both indicate that there is a period of increased vulnerability to repeated injury following a concussion and that its duration is variable. Growing evidence indicates that postinjury activity is likely to affect recovery from brain injury. Data suggest that long-term sequelae may result from prior concussion-particularly, repeated injuries. The unique aspects of cerebral development may account for differences in the effects of concussion in children and adolescents when compared with adults.

CONCLUSIONS

The available pathophysiologic data from basic science and clinical studies have increased the evidence base for concussion management strategies-the approaches to which may differ between young athletes and adults.

Brain injury in boxing

Clinical decision making for injured boxers follows the same therapeutic principles as the treatment plan for other injured athletes. Just as surgical techniques have improved, so has the scientific basis for implementing therapeutic exercises progressed to return the athletes to their former level of competition.

Neuroimaging findings and brain-behavioral correlates in a former boxer with chronic traumatic brain injury

Chronic traumatic brain injury (CTBI) is associated with contact sports such as boxing. CTBI results from repetitive blows to the head rather than from a single impact. CTBI individuals present with motor symptoms (incoordination, spasticity, parkinsonism), cognitive impairment (executive dysfunction, memory deficits) and neuropsychiatric symptoms (irritability, affective disturbances). The structural and functional neuroimaging findings and clinical presentation of a CTBI case are described. We propose hypotheses about the pathophysiology of the observed neuroimaging findings and their relationship to the neuropsychiatric symptoms of the patients.

Long-term neurologic outcomes after traumatic brain injury

OBJECTIVE

To determine the relations between traumatic brain injury (TBI) and several neurologic outcomes 6 months or more after TBI.

PARTICIPANTS

Not applicable.

DESIGN

Systematic review of the published, peer-reviewed literature.

PRIMARY MEASURES

Not applicable.

RESULTS

We identified 75 studies that examined the relations between TBI and neurologic outcomes. Unprovoked seizures are causally related to penetrating TBI as well as to moderate and severe TBI. There was only limited evidence of an association between seizures and mild TBI. Dementia of the Alzheimer's type (DAT) was associated with moderate and severe TBI, but not with mild TBI unless there was loss of consciousness (LOC); the evidence for the latter was limited. Parkinsonism was associated with moderate and severe TBI, but there was only modest evidence of a link with mild TBI without LOC. Dementia pugilistica was associated with professional boxing. There was insufficient evidence to support an association between TBI and both multiple sclerosis and amyotrophic lateral sclerosis. TBI appeared to produce a host of postconcussive symptoms (eg, memory problems, dizziness, and irritability). Moderate and severe TBI were associated with endocrine problems such as hypopituitarism and growth hormone deficiency and possibly with diabetes insipidus. There was only limited evidence of an association between mild TBI and the development of ocular/visual motor deterioration.

CONCLUSION

TBI is strongly associated with several neurologic disorders 6 months or more after injury. Clinicians caring for TBI patients should monitor them closely for the development of these disorders. While some of these disorders can be treated after they arise (eg, seizures), a greater public health benefit would be achieved by preventing them before they develop. Research efforts to develop therapies aimed at secondary prevention are currently underway.

Neuropsychological consequences of boxing and recommendations to improve safety: a National Academy of Neuropsychology education paper

Boxing has held appeal for many athletes and audiences for centuries, and injuries have been part of boxing since its inception. Although permanent and irreversible neurologic dysfunction does not occur in the majority of participants, an association has been reported between the number of bouts fought and the development of neurologic, psychiatric, or histopathological signs and symptoms of encephalopathy in boxers. The purpose of this paper is to (i) provide clinical neuropsychologists, other health-care professionals, and the general public with information about the potential neuropsychological consequences of boxing, and (ii) provide recommendations to improve safety standards for those who participate in the sport.

Dementia Pugilistica with clinical features of Alzheimer's disease

A 61-year-old ex-boxer presented with a three-year history of progressive memory decline. During a seven-year follow-up period, there was a continuous cognitive decline, very similar to that usually observed in Alzheimer's disease. Parkinsonian, pyramidal or cerebellar signs were conspicuously absent. Neuropathological examination revealed the typical features of dementia pugilistica: cavum septi pellucidi with multiple fenestrations, numerous neurofibrillary tangles in the cerebral isocortex and hippocampus (and rare senile plaques). Immunohistochemistry disclosed a high number of tau protein deposits and scarce beta-amyloid staining. This case shows that dementia pugilistica may present with clinical features practically undistinguishable from Alzheimer's disease.

Subdural hematomas in boxing: the spectrum of consequences

✓Boxing is a violent sport in which every participant accepts the risk of brain damage or death. This sport has been linked to acute neurological injury and chronic brain damage. The most common life-threatening injury encountered by its participants is subdural hematoma (SDH), and the most feared consequence of chronic insult to the nervous system is dementia pugilistica, or punch drunkenness. Although advances in imaging and neuropsychological testing have improved our ability to diagnose these injuries, the unprecedented sensitivity and wide availability of these modalities have increased the detection of mild cognitive impairment and small, asymptomatic imaging abnormalities. The question has thus been raised as to where on the spectrum of these injuries an athlete should be permanently banned from the sport.

In this report the authors describe six boxers who were evaluated for SDH sustained during participation in the sport, and who experienced remarkably different outcomes. Their presentations, clinical courses, and boxing careers are detailed. The athletes ranged in age from 24 to 55 years at the time of injury. Two were female and four were male; half of them were amateurs and half were professionals. Treatments ranged from observation only to decompressive craniectomy. Two of the athletes were allowed to participate in the sport after their injury (one following a lengthy legal battle), with no known sequelae. One boxer died within 48 hours of her injury and at least two suffered permanent neurological deficits. In a third, dementia pugilistica was diagnosed 40 years later, and the man died while institutionalized.

Injury risk in professional boxing

OBJECTIVE

Although a popular endeavor, boxing has fallen under increased scrutiny because of its association with traumatic brain injury. However, few studies have investigated the overall epidemiology of boxing injuries from representative samples, and no study has ever documented the incidence of injuries in female boxers. This study is a review of professional boxing data from the state of Nevada from September 2001 through March 2003.

MATERIALS AND METHODS

Medical and outcome data for all professional boxing matches occurring in Nevada between September 2001 and March 2003 (n = 524 matches) were analyzed on the basis of a pair-matched, case-control design. Cases were boxers who received an injury during the boxing matches. Boxers who were not injured served as control subjects. Both conditional and unconditional logistic regression models were used to assess risk factors for injury.

RESULTS

The overall incidence rate of injury was 17.1 per 100 boxer-matches, or 3.4 per 100 boxer-rounds. Facial laceration accounted for 51% of all injuries, followed by hand injury (17%), eye injury (14%), and nose injury (5%). Male boxers were significantly more likely than female boxers to receive injuries (3.6 versus 1.2 per 100 boxer-rounds, P = 0.01). Male boxing matches also ended in knockouts and technical knockouts more often than did female matches (P < 0.001). The risk of injury for those who lost the matches was nearly twice the risk for the winners. Those who lost by knockout had double the risk of injury compared with those who lost by other means. Neither age nor weight was significantly associated with the risk of injury.

CONCLUSIONS

The injury rate in professional boxing matches is high, particularly among male boxers. Superficial facial lacerations are the most common injury reported. Male boxers have a higher rate of knockout and technical knockouts than female boxers. Further research is necessary to determine the outcomes of injury, particularly the long-term neurologic outcome differences between sexes.

Central nervous system injuries in sport and recreation: a systematic review

Many sports have been associated with a variety of neurological injuries affecting the central nervous system (CNS), with some injuries specific to that sport. A systematic review of sport-specific CNS injuries has not been attempted previously, and could assist in the understanding of morbidity and mortality associated with particular sporting activities, either professional or amateur. A systematic review of the literature was performed using PubMed (1965-2003) examining all known sports and a range of possible CNS injuries attributable to that sport. Numerous sporting activities (45) have associated CNS injuries as reported within the literature. The sports most commonly associated with CNS injuries are: football, boxing, hockey, use of a trampoline, and various winter activities. A number of sporting activities are associated with unique CNS injuries or injury-related diseases such as heat stroke in auto racing, vertebral artery dissection in the martial arts, and dementia pugilistica in boxing. Neurological injuries of the CNS due to sport comprise a wide collection of maladies that are important for the neurologist, neurosurgeon, orthopaedic surgeon, physiatrist, sports medicine doctor, athletic trainer and general physician to recognise.

The risk of chronic traumatic brain injury in professional boxing: change in exposure variables over the past century

OBJECTIVES

To determine if boxing exposure has changed over time and hence if current professional boxers are at the same risk of developing chronic traumatic brain injury (CTBI) as historical controls.

DESIGN

Literature review of published studies and analysis of data of active professional boxers.

SUBJECTS

Professional boxers in the United Kingdom and Australia.

MAIN OUTCOME MEASURES

Boxing history and participation in sparring and professional bouts.

RESULTS

Since the 1930s, the average duration of a professional boxer's career has dropped from 19 years to five years, and the mean number of career bouts has reduced from 336 to 13. This is despite no significant decline in participation rates from 1931 until 2002.

CONCLUSIONS

The incidence of boxing related CTBI will diminish in the current era of professional boxing because of the reduction in exposure to repetitive head trauma and increasing medical monitoring of boxers, with preparticipation medical and neuroimaging assessments resulting in the detection of early and potentially pre-symptomatic cases of CTBI.

Chronic Traumatic Encephalopathy in a National Football League Player

OBJECTIVE

We present the results of the autopsy of a retired professional football player that revealed neuropathological changes consistent with long-term repetitive concussive brain injury. This case draws attention to the need for further studies in the cohort of retired National Football League players to elucidate the neuropathological sequelae of repeated mild traumatic brain injury in professional football.

METHODS

The patient's premortem medical history included symptoms of cognitive impairment, a mood disorder, and parkinsonian symptoms. There was no family history of Alzheimer's disease or any other head trauma outside football. A complete autopsy with a comprehensive neuropathological examination was performed on the retired National Football League player approximately 12 years after retirement. He died suddenly as a result of coronary atherosclerotic disease. Studies included determination of apolipoprotein E genotype.

RESULTS

Autopsy confirmed the presence of coronary atherosclerotic disease with dilated cardiomyopathy. The brain demonstrated no cortical atrophy, cortical contusion, hemorrhage, or infarcts. The substantia nigra revealed mild pallor with mild dropout of pigmented neurons. There was mild neuronal dropout in the frontal, parietal, and temporal neocortex. Chronic traumatic encephalopathy was evident with many diffuse amyloid plaques as well as sparse neurofibrillary tangles and tau-positive neuritic threads in neocortical areas. There were no neurofibrillary tangles or neuropil threads in the hippocampus or entorhinal cortex. Lewy bodies were absent. The apolipoprotein E genotype was E3/E3.

CONCLUSION

This case highlights potential long-term neurodegenerative outcomes in retired professional National Football League players subjected to repeated mild traumatic brain injury. The prevalence and pathoetiological mechanisms of these possible adverse long-term outcomes and their relation to duration of years of playing football have not been sufficiently studied. We recommend comprehensive clinical and forensic approaches to understand and further elucidate this emergent professional sport hazard.

Sports-related and gender differences on neuropsychological measures of frontal lobe functioning

OBJECTIVE

To determine similarities and differences in the performance of female and male athletes on neuropsychological measures of frontal lobe functioning.

DESIGN

A cross-sectional study of male and female college-aged athletes involved in one of the following sports: hockey, basketball, softball, lacrosse, soccer, swimming, and track.

SETTING

Division III college.

PARTICIPANTS

A total of 262 athletes (male, n=157; female, n=105) participated in the study.

MAIN OUTCOME MEASURES

Controlled Oral Word Association (letters F, A, S), Cognitive Assessment System (Planned Codes, Planned Connections, Number Detection), and WAIS-R-NI Vocabulary were administered to all athletes.

RESULTS

MANCOVA was performed with gender and sport as fixed factors. Female athletes displayed faster and more accurate performance on perceptual-motor tasks (P<0.01) and on one condition of a verbal fluency task (P<0.01) compared with male athletes. Male hockey athletes showed superior perceptual-motor speed and accuracy (P<0.01) compared with male athletes in the track/swimming group. Evaluators were naive to athletes' gender and sport.

CONCLUSION

Gender- and sport-specific performances on perceptual-motor and verbal fluency tasks were found. Adding cognitive components to base functions eliminates gender- and sports-related distinctions, suggesting that existing differences are related to basic, fundamental skills, which are inherent and practiced within the respective sport. Understanding the differences and similarities across sports and gender on various neurocognitive measures is relevant for determining group differences in studies examining the consequences of mild traumatic brain injury among athletes.

Assessment of cognitive recovery following sports related head trauma in boxers

OBJECTIVE

To prospectively examine recovery of cognitive function within one month following subconcussive sports related head trauma.

DESIGN

A prospective study of New York State licensed professional boxers who underwent testing of cognitive functioning before and after (within days, one week, and one month) a professional bout.

SETTING

Male professional athletes recruited from the New York State Athletic Commission and local boxing gyms.

PARTICIPANTS

Twenty-six licensed professional boxers were enrolled in the protocol. Data is presented on the 18 participants who completed testing on at least three of the four time points.

INTERVENTIONS

Serial neuropsychological assessment before and after the athletes engaged in competition.

MAIN OUTCOME MEASURES

Neuropsychological measures of cognitive functioning, including new learning and memory, information processing speed, and mental flexibility.

RESULTS

A series of repeated measures MANOVAS revealed significant within subject differences across testing on complex information processing and verbal fluency. Post hoc analyses indicated significant differences between time 1 (baseline) and time 4 (one month post), with scores one month following the bout indicating significantly improved performance. Memory scores did not change significantly across testing; however, prior boxing exposure measured by total number of professional bouts was associated with poorer memory performance.

CONCLUSIONS

Cognitive testing one month following participation in a professional boxing bout yielded scores suggestive of recovery to a level above the baseline. We conclude that baseline assessment taken during periods of intense training are likely confounded by other pre-bout conditions (i.e., sparring, rapid weight loss, pre-bout anxiety) and do not represent true baseline abilities. Instability of performance associated with mild head injury may complicate the interpretation of post-injury assessments. Practice effects may also confound the interpretation of serial assessments, leading to underestimation of the effects of sports related head trauma. Poorer cognitive performance was evident during the presumed recovery period in boxers with greater exposure to the sport (>12 professional bouts). This finding is consistent with reports of a cumulative effect of repetitive head trauma and the subsequent development of chronic traumatic brain injury. These data have implications for assessing recovery of function following head injury in players of other contact sports as well as determination of return-to-play following an injury.

Central nervous system trauma management of concussions in athletes

The care of athletes with concussions is challenging because each patient has different symptoms. An athlete should never be returned to play until completely asymptomatic. Classification systems for concussions are not based on scientific evidence and represent some practitioners' best guess at what is safe for young athletes. Many experienced team physicians believe they can allow an athlete to play safely if there are no symptoms at rest and no symptoms with increasing intensity of exercise. Abbreviated neuropsychological testing and balance tests show promise for use in the field to increase the sensitivity of our neurological evaluation on injured athletes. Any neuropsychological or balance evaluation is more helpful if baseline data is collected on athletes before they are injured.

Repeated mild brain injuries result in cognitive impairment in B6C3F1 mice

Experimental investigations of single mild brain injury (SMI) show relatively little resultant cognitive impairment. However, repeated mild brain injuries (RMI), as those sustained by athletes (e.g., football, hockey, and soccer players) may have cumulative effects on cognitive performance and neuropathology. Numerous clinical studies show persistent, latent, and long-term consequences of RMI, unlike the episodic nature of SMI. The nature of repeated traumatic brain injury (TBI) introduces confounding factors in invasive and even semiinvasive animal models of brain injury (e.g., scar formation). Thus, the present study characterizes SMI and RMI in a noninvasive mouse weight drop model and the cumulative effects of RMI on cognitive performance. Investigation of drop masses and drop distances revealed masses of 50, 100, and 150 g dropped from 40 cm resulted in 0% mortality, no skull fracture, and no difference in acute neurological assessment following sham injury, SMI, or RMI. Cumulative effects of RMI were examined following four mild brain injuries 24 h apart induced by 50-, 100-, or 150-g masses dropped from 40 cm through histological measures, mean arterial pressure, and measures of complex/spatial learning. RMI produced no overt cell death within the cortex or hippocampus, no evidence of blood-brain barrier compromise, and no significant change in mean arterial pressure. Following testing in the Morris water maze (MWM) on days 7-11 after initial injury, mice in the RMI 100-g and RMI 150-g groups had significantly longer MWM goal latencies compared to sham, SMI 150-g, and RMI 50-groups. Additionally, the evident cognitive deficit manifested in the absence of observed cell death. This is the first study to show complex/spatial learning deficits following RMI, similar to the visual/spatial perception and planning deficits observed in clinical studies.

The cumulative effect of repetitive concussion in sports

The increased popularity of contact sports worldwide exposes a large number of participants to both acute and chronic traumatic brain injury. Chronic traumatic brain injury (CTBI) represents the cumulative, long-term neurological consequences of repetitive concussive and subconcussive blows to the brain. Although this condition has been described primarily in boxing, it may be anticipated in other contact sports such as soccer, football, ice hockey, and the martial arts. Since treatment options in CTBI are relatively limited, the prevention of CTBI is of paramount importance. Minimizing the frequency and severity of acute brain injury in sport will be instrumental in accomplishing this goal. The prevention of CTBI will need to be sport specific and will undoubtedly rely on limiting the exposure of high-risk athletes, utilizing of protective equipment, enforcing strict rule adherence, training and supervising athletes, and increasing medical surveillance.

Head injury in athletes

HEAD INJURIES INCURRED during athletic endeavors have been recorded since games were first held. During the last century, our level of understanding of the types of cerebral insults, their causes, and their treatment has advanced significantly. Because of the extreme popularity of sports in the United States and worldwide, the implications of athletic head injury are enormous. This is especially true considering the current realization that mild traumatic brain injury (MTBI) or concussion represents a major health consideration with more long-ranging effects than previously thought. When considering athletic injuries, people who engage in organized sports, as well as the large number of people who engage in recreational activities, should be considered. There are 200 million international soccer players, a group increasingly recognized to be at risk for MTBI. The participation in contact sports of a large number of the population, especially youth, requires a careful and detailed analysis of injury trends and recommended treatment. There are numerous characteristics of this patient population that make management difficult, especially their implicit request to once again be subjected to potential MTBI by participating in contact sports. Recent research has better defined the epidemiological issues related to sports injuries involving the central nervous system and has also led to classification and management paradigms that help guide decisions regarding athletes' return to play. We currently have methods at our disposal that greatly assist us in managing this group of patients, including improved recognition of the clinical syndromes of MTBI, new testing such as neuropsychological assessment, radiographic evaluations, and a greater appreciation of the pathophysiology of concussive brain injury. The potential for long-term consequences of repetitive MTBI has been recognized, and we no longer consider the "dinged" states of athletic concussions to have the benign connotations they had in the past. We review the historical developments in the recognition and care of athletes with head injuries, the current theory of the pathophysiology and biomechanics of these insults, and the recommended management strategy, including return-to-play criteria.

Concussions in athletes produce brain dysfunction as revealed by event-related potentials

We have used event-related potentials (ERP) to assess cerebral activity following mild traumatic brain injuries in 20 college athletes practising contact sports. Concussion victims showed a striking decrease in P300 amplitude, an effect presumed to reflect alterations in attentional-cognitive processes. Moreover, the degree of impairment was strongly related to the severity of post-concussion symptoms. Our data suggest that concussions cause objectively measurable changes in the electrophysiological markers of brain activity and hence in the functions of the structures from which they originate. ERPs may thus constitute a reliable method to accurately monitor the clinical course and recovery of head injuries in athletes.

Diagnosis and differential diagnosis of Parkinson's disease and parkinsonism

In the clinic setting, most cases represent either Parkinson's disease (PD) or one of the other neurodegenerative disorders that make up the parkinsonism-plus syndromes. The major parkinsonism-plus syndromes include progressive supranuclear palsy, multiple system atrophy, corticobasal degeneration, as well as parkinsonism occurring in the context of Alzheimer's disease or one of the other primary dementing disorders. There are a variety of other conditions, however, that occasionally come into the differential diagnosis. These fall into the categories of secondary parkinsonism (due to drugs, toxins, structural lesions, etc.), another tremor syndrome such as essential tremor, or a hereditary disorder with parkinsonism. This broad differential diagnosis is reviewed.

Lower cognitive performance of older football players possessing apolipoprotein E epsilon4

OBJECTIVE

To determine whether the cognitive status of professional football players varies as a function of age and apolipoprotein E (APOE) genotype.

METHODS

Fifty-three active players underwent APOE and neuropsychological assessments. Players were grouped according to age (proxy indicator of high/low exposure to contact) and the presence/absence of at least one copy of the epsilon4 allele. Outcome measures were overall cognitive performance and scores in cognitive domains.

RESULTS

As a group, older players possessing APOE epsilon4 exhibited significantly lower cognitive test scores than did all other players studied, including non-epsilon4-possessing players and younger epsilon4-carriers. Measures of general cognitive functioning, information-processing speed and accuracy, and attention were related to poorer performance among the epsilon4-carrying players. In an analysis of variance model, the interaction between APOE genotype and age was significant (P = 0.004). As determined using linear regression, age accounted for 34% of the variance in the memory index among APOE epsilon4-possessing players but did not contribute significantly to variance among the non-epsilon4-possessing players. Older APOE epsilon4-carriers were significantly overrepresented among players whose scores indicated possible cognitive impairment, with the criterion of performing two or more standard deviations below the general normal values in a summary index of general cognitive functioning.

CONCLUSION

Older professional football players who possessed the APOE epsilon4 allele scored lower on cognitive tests than did players without this allele or less experienced players of any genotype. The cognitive status of professional athletes with repeated exposure to head trauma may therefore be influenced by age, inherited factors such as APOE genotype, and cumulative exposure to contact.

A unifying hypothesis of Alzheimer's disease. III. Risk factors

Normal ageing and Alzheimer's disease (AD) have many features in common and, in many respects, both conditions only differ by quantitative criteria. A variety of genetic, medical and environmental factors modulate the ageing-related processes leading the brain into the devastation of AD. In accordance with the concept that AD is a metabolic disease, these risk factors deteriorate the homeostasis of the Ca(2+)-energy-redox triangle and disrupt the cerebral reserve capacity under metabolic stress. The major genetic risk factors (APP and presenilin mutations, Down's syndrome, apolipoprotein E4) are associated with a compromise of the homeostatic triangle. The pathophysiological processes leading to this vulnerability remain elusive at present, while mitochondrial mutations can be plausibly integrated into the metabolic scenario. The metabolic leitmotif is particularly evident with medical risk factors which are associated with an impaired cerebral perfusion, such as cerebrovascular diseases including stroke, cardiovascular diseases, hypo- and hypertension. Traumatic brain injury represents another example due to the persistent metabolic stress following the acute event. Thyroid diseases have detrimental sequela for cerebral metabolism as well. Furthermore, major depression and presumably chronic stress endanger susceptible brain areas mediated by a host of hormonal imbalances, particularly the HPA-axis dysregulation. Sociocultural and lifestyle factors like education, physical activity, diet and smoking may also modulate the individual risk affecting both reserve capacity and vulnerability. The pathophysiological relevance of trace metals, including aluminum and iron, is highly controversial; at any rate, they may adversely affect cellular defences, antioxidant competence in particular. The relative contribution of these factors, however, is as individual as the pattern of the factors. In familial AD, the genetic factors clearly drive the sequence of events. A strong interaction of fat metabolism and apoE polymorphism is suggested by intercultural epidemiological findings. In cultures, less plagued by the 'blessings' of the 'cafeteria diet-sedentary' Western lifestyle, apoE4 appears to be not a risk factor for AD. This intriguing evidence suggests that, analogous to cardiovascular diseases, apoE4 requires a hyperlipidaemic lifestyle to manifest as AD risk factor. Overall, the etiology of AD is a key paradigm for a gene-environment interaction. Copyright 2000 John Wiley & Sons, Ltd.

Acute traumatic brain injury in amateur boxing

Via neuropsychological testing, this research team found post-match cognitive impairment in amateur boxers despite the fighters' use of headgear.

BACKGROUND

Acute traumatic brain injury (ATBI) represents the neurologic consequence of concussive and subconcussive blows to the head. Evidence suggests that ATBI may be associated with boxing and collision sports such as American football and soccer, thus potentially exposing millions of athletes annually.

OBJECTIVE

The objectives of this study were to determine whether significant ATBI occurs in boxers who compete and, if present, the nature of the cognitive impairment. A secondary objective was to determine if headgear could reduce the risk for ATBI in amateur boxing.

DESIGN

In this inception cohort study, 38 amateur boxers underwent neuropsychological examination before and shortly after a boxing match and were compared with a control group of 28 amateur boxers who were tested before and after a comparable physical test. The main outcome measures were neuropsychological tests (memory, mental and fine-motor speed, planning, and attention) proven to be sensitive to cognitive changes incurred in contact and collision sports.

RESULTS

The boxers who competed exhibited an ATBI pattern of impaired performance in planning, attention, and memory capacity when compared with controls. They had significantly different findings in the Categorization Task Test (P = 0.047); Digit Symbol Test (P = 0.02); Logical Memory: Short Term Memory and Long Term Memory subtests (both tests, P < 0.001); and Visual Reproduction: Short Term Memory subtest (P < 0.001) and Long Term Memory subtest (P < 0.03).

CONCLUSION

Participation in amateur boxing matches may diminish neurocognitive functioning despite the use of headgear. The neurocognitive impairment resembles cognitive symptoms due to concussions. Guidelines are needed to reduce the risk for repeated ATBI.

Selected legal issues in movement disorders

This article explores the long-standing question of whether trauma causes Parkinson's disease, and discusses the impact of informed consent and confidentiality in issues of genetic testing for Huntington's disease. Neurologists are appropriately concerned about the legal aspects of genetic testing, and this article attempts to address that subject from a medical-legal perspective.

Genetic susceptibility to brain injury in sports: a role for genetic testing in athletes?

Technological advances in molecular biology during the next millennium may cause an explosion of genetic information about athletes' predisposition to illness and injury. Recent discoveries about a possible genetic predisposition to brain injury in boxers may be the tip of the iceberg, with far-reaching implications for members of the sports medicine community.