Subconcussive Blows Research Articles

Subconcussive Blows

Subconcussive Blows

CSF AND PLASMA BIOMARKERS FOR MILD TRAUMATIC BRAIN INJURY

Mild traumatic brain injury, defined as a head trauma resulting in brief loss of consciousness and/or alteration of mental state, is most often benign but may cause persisting and sometimes progressive symptoms. It is unknown if there is a certain threshold for the amount of brain injury and/or individual vulnerability that may lead to such long-term consequences. Further, there is a lack of established diagnostic methods that can tell whether a blow to the head indeed affected the brain and in what way. CSF and plasma samples have been collected on boxers and concussed versus non-concussed elite ice hockey players and examined using established and novel techniques for neuronal and astroglial injury markers, such as tau, neurofilament light, VILIP1, S-100B, and neuron-specific enolase. CSF and plasma biomarkers change in a dynamic manner following concussion. The magnitude of biomarker changes correlate with symptom duration. Some individuals have prolonged biomarker elevations. Biomarkers for axonal injury (tau and neurofilament light) appear to be more sensitive than biomarkers for astroglial injury. These data will be discussed in relation to the existing literature on more severe brain injuries and in relation to the biomarker literature on neurodegenerative diseases. There is a need to develop these biomarkers further and to implement them in clinical practice in cases of head trauma where the brain might have been impacted. Specifically, there is a need to implement them in the management of sports-related concussion, the most common cause of mild traumatic brain injury in the young, with the goal to prevent long-term neurological sequelae due to concussive or subconcussive blows to the head.

Detecting Neurocognitive and Neurophysiological Changes as a Result of Subconcussive Blows Among High School Football Athletes

Recent work suggests that repetitive subconcussive head impacts may contribute to long-term neurodegeneration; however, the risk thresholds for subconcussive injury are unknown. It was hypothesized that the number and severity of head impacts could quantify the risk of developing abnormal neurophysiology. Twenty-one high school boys (ages 14 to 18) participating in varsity and junior varsity football were evaluated over the course of 1 football season (13 games) using a combination of the ImPACT, functional magnetic resonance imaging (fMRI), and head impact telemetry. The number and severity of head impacts throughout the football season were subsequently compared with the fraction of players flagged by either the ImPACT or fMRI before, during, and after the competition season. Twelve of 22 (54.5%) in-season tests of asymptomatic participants had a minimum of 1 composite ImPACT score flagged. For the fMRI analysis, 16 (72.7%) of the 22 in-sea son sessions were considered flagged. Seven assessments were flagged by both the ImPACT and fMRI. Larger numbers of hits appeared to correspond with a larger fraction of players being flagged by at least fMRI or the ImPACT. A substantial number of clinically asymptomatic athletes exhibit significant neurophysi ological changes in-season. Furthermore, the number of head impacts is a risk factor for the development of neurophysiological changes. [Athletic Training & Sports Health Care. 2014;6(x):xxxxxx.] [Query #2: Reduce to 150 words.]

Neuroimaging in repetitive brain trauma.

Sports-related concussions are one of the major causes of mild traumatic brain injury. Although most patients recover completely within days to weeks, those who experience repetitive brain trauma (RBT) may be at risk for developing a condition known as chronic traumatic encephalopathy (CTE). While this condition is most commonly observed in athletes who experience repetitive concussive and/or subconcussive blows to the head, such as boxers, football players, or hockey players, CTE may also affect soldiers on active duty. Currently, the only means by which to diagnose CTE is by the presence of phosphorylated tau aggregations post-mortem. Non-invasive neuroimaging, however, may allow early diagnosis as well as improve our understanding of the underlying pathophysiology of RBT. The purpose of this article is to review advanced neuroimaging methods used to investigate RBT, including diffusion tensor imaging, magnetic resonance spectroscopy, functional magnetic resonance imaging, susceptibility weighted imaging, and positron emission tomography. While there is a considerable literature using these methods in brain injury in general, the focus of this review is on RBT and those subject populations currently known to be susceptible to RBT, namely athletes and soldiers. Further, while direct detection of CTE in vivo has not yet been achieved, all of the methods described in this review provide insight into RBT and will likely lead to a better characterization (diagnosis), in vivo, of CTE than measures of self-report.

Cerebral concussion: a historical perspective.

No topic in sports has gathered more attention and publicity than the diagnosis, management, and long-term effects of cerebral concussion. The relevant history of concussion starts in 1905 when President Theodore Roosevelt drew attention to the football 'death harvest'. Soon after, rules started to change to reduce the amount and severity of head injuries in football. Up until 1980, the primary focus regarding concussions was to diagnose a potentially fatal intracranial hemorrhage. While aware of long-term consequences of concussions, the perception at the time was that virtually all concussions would 'clear' with time and rest. Concussion management guidelines gave way to objective neuropsychological testing in the early 1990s with the development of the ImPACT™ (Immediate Post-Concussion Assessment and Cognitive Testing) neurocognitive test. Led by organized football, in 1994 the National Football League (NFL) formed the Mild Traumatic Brain Injury Committee which began to investigate the cause of concussions, evaluate equipment (particularly helmets), and recommend methods for prevention. In 2005, the first case of chronic traumatic encephalopathy was described in a deceased football player, raising concerns about the long-term consequences of head injuries and concussions. Major advancements in contact sports and the military are underway to reduce the incidence of concussions and subconcussive blows to the head.

Chronic Traumatic Encephalopathy: Where Are We and Where Are We Going?

Chronic traumatic encephalopathy (CTE, previously called punch drunk and dementia pugilistica) has a rich history in the medical literature in association with boxing, but has only recently been recognized with other contact sports, such as football and ice hockey, as well as with military blast injuries. CTE is thought to be a neurodegenerative disease associated with repeated concussive and subconcussive blows to the head. There is characteristic gross and microscopic pathology found in the brain, including frontal and temporal atrophy, axonal degeneration, and hyperphosphorylated tau and TAR DNA-binding protein 43 pathology. Clinically, there are characteristic progressive deficits in cognition (memory, executive dysfunction), behavior (explosivity, aggression), mood (depression, suicidality), and motor function (parkinsonism), which correlate with the anatomic distribution of brain pathology. While CTE shares clinical and neuropathological traits with other neurodegenerative diseases, the clinical syndrome and the neuropathology as a whole are distinct from other neurodegenerative diseases. Here we review the CTE literature to date. We also draw on the literature from mild traumatic brain injury and other neurodegenerative dementias, particularly when these studies provide guidance for future CTE research. We conclude by suggesting seven essential areas for future CTE research.

Sport and Nonsport Etiologies of Mild Traumatic Brain Injury: Similarities and Differences

Mild traumatic brain injury (mTBI) has recently gained appreciation as a significant public health problem, which has highlighted just how little is known about its proximal and long-term effects. A major challenge in the study of mTBI is the heterogeneity of the condition. Research on mTBI has historically separated sport and nonsport etiologies, and the extent to which research from one of these samples translates to the other is unclear. This review examines the literature on mTBI, with a focus on comparing sport and nonsport etiologies with regard to the latest research on biomechanics, pathophysiology, neurocognitive effects, and neuroimaging. Issues of particular relevance to sports injuries, such as exercise, repetitive injuries, subconcussive blows, and chronic injury effects, are also reviewed.

The effect of multiple sub-concussive blows on brain structural and functional integrity: combined virtual reality and neuroimaging study

ObjectiveTo determine the differential sensitivity of subjects, with and without prior history of concussion, towards multiple sub-concussive impacts. We hypothesised that previous concussions may increase the athletes' vulnerability to repetitive...

Evidence of Cognitive Dysfunction after Soccer Playing with Ball Heading Using a Novel Tablet-Based Approach

Does frequent head-to-ball contact cause cognitive dysfunctions and brain injury to soccer players? An iPad-based experiment was designed to examine the impact of ball-heading among high school female soccer players. We examined both direct, stimulus-driven, or reflexive point responses (Pro-Point) as well as indirect, goal-driven, or voluntary point responses (Anti-Point), thought to require cognitive functions in the frontal lobe. The results show that soccer players were significantly slower than controls in the Anti-Point task but displayed no difference in Pro-Point latencies, indicating a disruption specific to voluntary responses. These findings suggest that even subconcussive blows in soccer can result in cognitive function changes that are consistent with mild traumatic brain injury of the frontal lobes. There is great clinical and practical potential of a tablet-based application for quick detection and monitoring of cognitive dysfunction.

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.

Dementia Pugilistica with Clinical Features of Frontotemporal Dementia and Parkinsonism: Case Report

Dementia pugilistica (DP) or chronic traumatic encephalopathy (CTE) is a neurodegenerative disease or dementia that may affect amateur or professional boxers as well as athletes in other sports who suffer concussions. The condition is thought to affect around 15% to 20% of professional boxers and caused by repeated concussive or subconcussive blows. CTE was in the past referred to as dementia pugilistica, which reflected the prevailing notion that this condition was restricted to boxers. Recent research, however, has demonstrated neuropathological evidence of CTE in retired American football players, a professional wrestler, a professional hockey player and a soccer player, as well as in nonathletes. It is probable that many individuals are susceptible to CTE, including those who experience falls, motor vehicle accidents, assaults, epileptic seizures, or military combat, and that repeated mild closed head trauma of diverse origin is capable of instigating the neurodegenerative cascade leading to CTE. We report a 62year old man suspicious of dementia pugilistica with clinical features of frontotemporal dementia and parkinsonism.

Chronic Traumatic Encephalopathy

Sports-related concussion has gained increased prominence, in part due to media coverage of several well-known athletes who have died from consequences of chronic traumatic encephalopathy (CTE). CTE was first described by Martland in 1928 as a syndrome seen in boxers who had experienced significant head trauma from repeated blows. The classic symptoms of impaired cognition, mood, behavior, and motor skills also have been reported in professional football players, and in 2005, the histopathological findings of CTE were first reported in a former National Football League (NFL) player. These finding were similar to Alzheimer's disease in some ways but differed in critical areas such as a predominance of tau protein deposition over amyloid. The pathophysiology is still unknown but involves a history of repeated concussive and subconcussive blows and then a lag period before CTE symptoms become evident. The involvement of excitotoxic amino acids and abnormal microglial activation remain speculative. Early identification and prevention of this disease by reducing repeated blows to the head has become a critical focus of current research.

Epidemiology of neurodegeneration in American-style professional football players

The purpose of this article is to review the history of head injuries in relation to American-style football play, summarize recent research that has linked football head injuries to neurodegeneration, and provide a discussion of the next steps for refining the examination of neurodegeneration in football players. For most of the history of football, the focus of media reports and scientific studies on football-related head injuries was on the acute or short-term effects of serious, traumatic head injuries. Beginning about 10 years ago, a growing concern developed among neurologists and researchers about the long-term effects that playing professional football has on the neurologic health of the players. Autopsy-based studies identified a pathologically distinct neurodegenerative disorder, chronic traumatic encephalopathy, among athletes who were known to have experienced concussive and subconcussive blows to the head during their playing careers. Football players have been well represented in these autopsy findings. A mortality study of a large cohort of retired professional football players found a significantly increased risk of death from neurodegeneration. Further analysis found that non-line players were at higher risk than line players, possibly because of an increased risk of concussion. Although the results of the studies reviewed do not establish a cause effect relationship between football-related head injury and neurodegenerative disorders, a growing body of research supports the hypothesis that professional football players are at an increased risk of neurodegeneration. Significant progress has been made in the last few years on detecting and defining the pathology of neurodegenerative diseases. However, less progress has been made on other factors related to the progression of those diseases in football players. This review identifies three areas for further research: (a) quantification of exposure - a consensus is needed on the use of clinically practical measurements of blows to the head among football players; (b) genetic susceptibility factors - a more rigorous set of unbiased epidemiological and clinical studies is needed before any causal relationships can be drawn between suspected genetic factors, head injury, and neurodegeneration; and (c) earlier detection and prevention of neurodegenerative diseases.

Closing the Floodgates: The Battle Over Workers’ Compensation Rights in California

1In other words, more than 30% of all living retired NFL players are suing the NFL for injuries related to concussions and head trauma. The lawsuits allege that the NFL failed to take reasonable steps to protect players from the risks 2 —including neurocognitive decline, permanent mental disability, and death—created by concussive and sub-concussive head injuries suffered while playing in NFL games. The plaintiffs also allege that the NFL not only breached its duty to prevent harm to its players, but also “orchestrated a campaign of disinformation designed to convince [p]layers . . . that concussive and sub-concussive blows posed no real danger.” 3

Biomechanical correlates of symptomatic and asymptomatic neurophysiological impairment in high school football

Concussion is a growing public health issue in the United States, and chronic traumatic encephalopathy (CTE) is the chief long-term concern linked to repeated concussions. Recently, attention has shifted toward subconcussive blows and the role they may play in the development of CTE. We recruited a cohort of high school football players for two seasons of observation. Acceleration sensors were placed in the helmets, and all contact activity was monitored. Pre-season computer-based neuropsychological tests and functional magnetic resonance imaging (fMRI) tests were also obtained in order to assess cognitive and neurophysiological health. In-season follow-up scans were then obtained both from individuals who had sustained a clinically-diagnosed concussion and those who had not. These changes were then related through stepwise regression to history of blows recorded throughout the football season up to the date of the scan. In addition to those subjects who had sustained a concussion, a substantial portion of our cohort who did not sustain concussions showed significant neurophysiological changes. Stepwise regression indicated significant relationships between the number of blows sustained by a subject and the ensuing neurophysiological change. Our findings reinforce the hypothesis that the effects of repetitive blows to the head are cumulative and that repeated exposure to subconcussive blows is connected to pathologically altered neurophysiology.

Mild Traumatic Brain Injury: Lessons Learned from Clinical, Sports, and Combat Concussions

Over the past forty years, a tremendous amount of information has been gained on the mechanisms and consequences of mild traumatic brain injuries. Using sports as a laboratory to study this phenomenon, a natural recovery curve emerged, along with standards for managing concussions and returning athletes back to play. Although advances have been made in this area, investigation into recovery and return to play continues. With the increase in combat-related traumatic brain injuries in the military setting, lessons learned from sports concussion research are being applied by the Department of Defense to the assessment of blast concussions and return to duty decision making. Concussion management and treatment for military personnel can be complicated by additional combat related stressors not present in the civilian environment. Cognitive behavioral therapy is one of the interventions that has been successful in treating symptoms of postconcussion syndrome. While we are beginning to have an understanding of the impact of multiple concussions and subconcussive blows in the sports world, much is still unknown about the impact of multiple blast injuries.

Subject-specific changes in brain white matter on diffusion tensor imaging after sports-related concussion

Background and Purpose Current approaches to diffusion tensor imaging (DTI) analysis do not permit identification of individual-level changes in DTI indices. We investigated the ability of wild bootstrapping analysis to detect subject-specific changes in brain white matter (WM) before and after sports-related concussion. Materials and Methods A prospective cohort study was performed in nine high school athletes engaged in hockey or football and six controls. Subjects underwent DTI pre- and postseason within a 3-month interval. One athlete was diagnosed with concussion (scanned within 72 h), and eight suffered between 26 and 399 subconcussive head blows. Fractional anisotropy (FA) and mean diffusivity (MD) were measured in each WM voxel. Bootstrap samples were generated, and a permuted t test was used to compare voxel-wise FA/MD changes in each subject pre- vs. postseason. Results The percentage of WM voxels with significant ( p<.05) pre–post FA changes was highest for the concussion subject (3.2%), intermediary for those with subconcussive head blows (mean 1.05%±.15%) and lowest for controls (mean 0.28%±.01%). Similarly, the percentage of WM voxels with significant MD changes was highest for the concussion subject (3.44%), intermediary for those with subconcussive head blows (mean 1.48%±.17%) and lowest for controls (mean 0.48%±.05%). Significantly changed FA and MD voxels colocalized in the concussion subject to the right corona radiata and right inferior longitudinal fasciculus. Conclusions Wild bootstrap analysis detected significantly changed WM in a single concussed athlete. Athletes with multiple subconcussive head blows had significant changes in a percentage of their WM that was over three times higher than controls. Efforts to understand the significance of these WM changes and their relationship to head impact forces appear warranted.

Stuck at the bench: Potential natural neuroprotective compounds for concussion

Background:While numerous laboratory studies have searched for neuroprotective treatment approaches to traumatic brain injury, no therapies have successfully translated from the bench to the bedside. Concussion is a unique form of brain injury, in that the current mainstay of treatment focuses on both physical and cognitive rest. Treatments for concussion are lacking. The concept of neuro-prophylactic compounds or supplements is also an intriguing one, especially as we are learning more about the relationship of numerous sub-concussive blows and/or repetitive concussive impacts and the development of chronic neurodegenerative disease. The use of dietary supplements and herbal remedies has become more common place.Methods:A literature search was conducted with the objective of identifying and reviewing the pre-clinical and clinical studies investigating the neuroprotective properties of a few of the more widely known compounds and supplements.Results:There are an abundance of pre-clinical studies demonstrating the neuroprotective properties of a variety of these compounds and we review some of those here. While there are an increasing number of well-designed studies investigating the therapeutic potential of these nutraceutical preparations, the clinical evidence is still fairly thin.Conclusion:There are encouraging results from laboratory studies demonstrating the multi-mechanistic neuroprotective properties of many naturally occurring compounds. Similarly, there are some intriguing clinical observational studies that potentially suggest both acute and chronic neuroprotective effects. Thus, there is a need for future trials exploring the potential therapeutic benefits of these compounds in the treatment of traumatic brain injury, particularly concussion.

Concussions And Heading Exposure Cause Cognitive Impairments In Soccer Players

The effect of cumulative heading in soccer (Association Football) on cognitive functioning remains an issue of debate. Several studies suggest that heading might cause sub-concussive blows to the head and that repeated heading could eventually lead to cognitive impairment. However, the interpretation of the data remains limited because of methodological issues (e.g., lack of appropriate control group and poor control for previous head injuries). PURPOSE: To determine the relative contribution of sport-related concussions and heading on the cognitive functioning of university soccer athletes. METHODS: We measured cognitive functioning in three groups of athletes using standardized neuropsychological tests and by means of event-related potentials elicited by a 3 stimulus oddball paradigm. The participants in the study were soccer players without a history of concussion (n = 18), soccer players who sustained one or more concussions (n = 22), and athletes from a non contact sport (volleyball, tennis, and badminton) who never sustained a concussion (n = 22). Group comparisons were investigated with a series of ANOVA's. RESULTS: No group differences were found for any of the neuropsychological tests used (p >0.05). Compared to the non contact sport athletes, the concussed soccer players had a significantly lower amplitude for the P3b component of their ERP waveform (F 2,58 = 3,278; p < 0.05). The results for the concussed and non concussed soccer athletes were not significantly different (p >0.05). CONCLUSIONS: Reductions in the P3b amplitude for the soccer players compared to the non contact sport athletes reflects subtitle deficits in the attentional processes related to updating information in working memory. These results also suggest that heading exposure alone affects cognitive processing in soccer athletes.

Comparison of Preseason, Midseason, and Postseason Neurocognitive Scores in Uninjured Collegiate Football Players

Background College football players sustain an average of 3 subconcussive blows to the head per game. Concussions correlate with decreases in standardized neurocognitive test scores. It is not known whether repetitive, subconcussive microtrauma associated with participation in a full season of collision sport affects neurocognitive test scores. Hypothesis No difference exists between preseason, midseason, and postseason Standardized Assessment of Concussion (SAC) and Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) scores when collegiate football players sustain subconcussive microtrauma from forceful, repetitive contact activity. Study Design Case series; Level of evidence, 4. Methods Fifty-eight members of a Division III collegiate football team who had no known concussion during the season voluntarily completed the SAC and ImPACT instruments preseason, midseason, and postseason. A repeated measures analysis of variance was used to compare the scores at the 3 time intervals (P < .05). Results No statistically significant decreases were found in overall SAC or ImPACT scores or in any of the domains or composites of the tests (P < .05) when preseason, midseason, and postseason scores were evaluated. Conclusions ImPACT and SAC neurocognitive test scores are not significantly altered by a season of repetitive contact in collegiate football athletes who have not sustained a concussion. Clinical Relevance A diminution in SAC or ImPACT scores in concert with clinical symptoms and findings should be interpreted as evidence of a postconcussive event.