Evan L. Breedlove

Functionally-Detected Cognitive Impairment in High School Football Players without Clinically-Diagnosed Concussion

Head trauma and concussion in football players have recently received considerable media attention. Postmortem evidence suggests that accrual of damage to the brain may occur with repeated blows to the head, even when the individual blows fail to produce clinical symptoms. There is an urgent need for improved detection and characterization of head trauma to reduce future injury risk and promote development of new therapies. In this study we examined neurological performance and health in the presence of head collision events in high school football players, using longitudinal measures of collision events (the HIT(™) System), neurocognitive testing (ImPACT(™)), and functional magnetic resonance imaging MRI (fMRI). Longitudinal assessment (including baseline) was conducted in 11 young men (ages 15-19 years) participating on the varsity and junior varsity football teams at a single high school. We expected and observed subjects in two previously described categories: (1) no clinically-diagnosed concussion and no changes in neurological behavior, and (2) clinically-diagnosed concussion with changes in neurological behavior. Additionally, we observed players in a previously undiscovered third category, who exhibited no clinically-observed symptoms associated with concussion, but who demonstrated measurable neurocognitive (primarily visual working memory) and neurophysiological (altered activation in the dorsolateral prefrontal cortex [DLPFC]) impairments. This new category was associated with significantly higher numbers of head collision events to the top-front of the head, directly above the DLPFC. The discovery of this new category suggests that more players are suffering neurological injury than are currently being detected using traditional concussion-assessment tools. These individuals are unlikely to undergo clinical evaluation, and thus may continue to participate in football-related activities, even when changes in brain physiology (and potential brain damage) are present, which will increase the risk of future neurological injury.

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.

Alteration of default mode network in high school football athletes due to repetitive subconcussive mild traumatic brain injury: a resting-state functional magnetic resonance imaging study.

Long-term neurological damage as a result of head trauma while playing sports is a major concern for football athletes today. Repetitive concussions have been linked to many neurological disorders. Recently, it has been reported that repetitive subconcussive events can be a significant source of accrued damage. Since football athletes can experience hundreds of subconcussive hits during a single season, it is of utmost importance to understand their effect on brain health in the short and long term. In this study, resting-state functional magnetic resonance imaging (rs-fMRI) was used to study changes in the default mode network (DMN) after repetitive subconcussive mild traumatic brain injury. Twenty-two high school American football athletes, clinically asymptomatic, were scanned using the rs-fMRI for a single season. Baseline scans were acquired before the start of the season, and follow-up scans were obtained during and after the season to track the potential changes in the DMN as a result of experienced trauma. Ten noncollision-sport athletes were scanned over two sessions as controls. Overall, football athletes had significantly different functional connectivity measures than controls for most of the year. The presence of this deviation of football athletes from their healthy peers even before the start of the season suggests a neurological change that has accumulated over the years of playing the sport. Football athletes also demonstrate short-term changes relative to their own baseline at the start of the season. Football athletes exhibited hyperconnectivity in the DMN compared to controls for most of the sessions, which indicates that, despite the absence of symptoms typically associated with concussion, the repetitive trauma accrued produced long-term brain changes compared to their healthy peers.

MR spectroscopic evidence of brain injury in the non-diagnosed collision sport athlete.

With growing evidence of long-term neurological damage in individuals enduring repetitive head trauma, it is critical to detect lower-level damage accumulation for the early diagnosis of injury in at-risk populations. Proton magnetic resonance spectroscopic scans of the dorsolateral prefrontal cortex and primary motor cortex were collected from high school American (gridiron) football athletes, prior to and during their competition seasons. Although no concussions were diagnosed, significant metabolic deviations from baseline and non-collision sport controls were revealed. Overall the findings indicate underlying biochemical changes, consequential to repetitive hits, which have previously gone unnoticed due to a lack of traditional neurological symptoms.

Collegiate women's soccer players suffer greater cumulative head impacts than their high school counterparts

Soccer is the source of the highest concussion rates among female athletes and is associated with neurological deficits at many levels of play. Despite its importance to our understanding of head trauma in female athletes, little is known about the number and magnitude of head impacts experienced by female soccer players. Head impacts experienced by high school and collegiate athletes were quantified using xPatch sensors (X2 Biosystems) affixed behind the right ear of each player. The average peak translational acceleration (PTA) sustained by players at the high school level was significantly lower than that of the collegiate players, but the average peak angular accelerations (PAA) were not significantly different. Given that the collegiate players took many more impacts throughout the season, their mean cumulative exposure to translational (cPTA) and angular accelerations (cPAA) were significantly higher than those of the high school players. Additional research is required to determine whether the differences in cumulative exposure are responsible for the elevated risk of concussion in collegiate soccer players or if there are additional risk factors.

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.]

Sub-concussive hit characteristics predict deviant brain metabolism in football athletes

Magnetic resonance spectroscopy and helmet telemetry were used to monitor the neural metabolic response to repetitive head collisions in 25 high school American football athletes. Specific hit characteristics were determined highly predictive of metabolic alterations, suggesting that sub-concussive blows can produce biochemical changes and potentially lead to neurological problems.

DTI Detection of Longitudinal WM Abnormalities Due to Accumulated Head Impacts

Longitudinal evaluation using diffusion-weighted imaging and collision event monitoring was performed on high school athletes who participate in American football. Observed changes in white matter health were suggestive of injury and found to be correlated with accumulation of head collision events during practices and games.

The Role of Location of Subconcussive Head Impacts in fMRI Brain Activation Change

Monte-Carlo permutation analysis was used to identify sets of head impacts most predictive of functional magnetic resonance imaging (fMRI) changes in football players. The relative distribution of impact location was found to be more predictive of brain activation changes than the number of impacts, suggesting that fMRI changes are related to systematic playing style.

Impact attenuation capabilities of football and lacrosse helmets

Although the National Operating Committee on Standards for Athletic Equipment (NOCSAE) standards are similar for football and lacrosse helmets, it remains unknown how helmets for each sport compare on drop tests. Due to the increased concern over head injury in sport and the rapid growth in lacrosse participation, it is useful to compare the performance of various football and lacrosse helmets. Therefore, the goal of this study was to document the impact attenuation properties of football and lacrosse helmets and to identify the relative performance between helmets for the two sports. Six models of football and six models of lacrosse helmets were tested using a drop tower at three prescribed velocities and six locations on the helmets. A repeated measures ANOVA was conducted to determine the effect of sport on Gadd Severity Index (GSI) scores and linear accelerations. The interaction between location and sport was significant at the low (F2.64,89.71=7.68, P<.001, η2=.025), medium (F2.85,96.85=16.78, P<.001, η2=.085), and high (F2.96,100.69=16.67, P<.001, η2=.093) velocities for GSI scores. When comparing peak acceleration results, we found a significant interaction between location and sport for the medium (F3.40,115.616=5.57, P=.001, ω2=.031) and high (F3.46,117.50=6.42, P<.001, ω2=.047) velocities. Features of football helmet design provide superior protection compared to lacrosse helmets. Further investigation of helmet design features across sports will yield insight into how design features influence helmet performance during laboratory testing.