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

Abstract

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 Ô 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.

The Influence of Head Impact Threshold for Reporting Data in Contact and Collision Sports: Systematic Review and Original Data Analysis

“…2,11,44,61,100 The issue relating to the effects of subconcussive impacts is controversial as researchers and clinicians are divided on the true effects. 4,40,44,67,74,103 Some research 74 has reported that these impacts have minimal effect on cognitive functions, while others 4,40,67,89,103 have reported these to be detrimental to cerebral and cognitive functions. To date, there is a paucity of evidence to identify the impact acceleration that is adequate to produce a non-structural brain injury associated with the neuronal changes of concussion.…”

“…It has been suggested 100, 103 that brain injuries not only come from concussive events but also from the accrual of subconcussive impacts that can result in pathophysiological changes in the brain. There are numerous studies 2,4,35,40,67,89,103 published that have demonstrated that the accumulation of subconcussive blows can result in neurophysiological changes. However, similar to the literature focused on concussion and mild traumatic brain injury (mTBI), the literature on subconcussive head trauma is limited.…”

“…10g 96 10g Y Y Beckwith et al 8 14 13 14.4g Y Y Y Cobb et al 20 14 23 14.4g Y Daniel et al 27 14.4g 94 14.4g Y Talavage et al 103 14.4g Urban et al 107 14 119 14 Total number of impacts and impacts not included for published studies based on the percentage of impacts removed compared with a10g impact threshold using data analysis of New Zealand senior rugby players.…”

Sports-related brain injuries: connecting pathology to diagnosis

“…In a pediatric series of 21 male high school football players with no prior history of concussion, 134 fMRI revealed alterations in the pattern and amplitude of BOLD signal differences when performing the 2-back and 1-back memory tasks, particularly in the middle and superior temporal gyri in 4 athletes who sustained a concussion during the football season. Interestingly, in 4 other players who did not sustain a concussion, fMRI revealed significantly decreased activation levels in the dorsolateral prefrontal cortex and cerebellum, regions of the brain which are associated with working memory.…”

Dendritic Spine Loss and Chronic White Matter Inflammation in a Mouse Model of Highly Repetitive Head Trauma

“…In a study of high school football players, the number of helmet impacts >20 g recorded in a single season ranged from a low of 226 (average, 4.7 per session) to a high of 1855 (average, 38.6 per session). 1 Most of these impacts do not result in the clinical diagnosis of a concussion; however, it is not known if the cumulative effects of these impacts can result in increased damage to the brain. mTBI has been extensively modeled in mice and rats.…”