Brain white matter changes following repetitive head hits in a single sporting event

By Runa Katayama. This article was initially published in the 7/25/24 edition of our Concussion Update newsletter; please consider subscribing.

In an observational cohort study published by the Journal of Neurotrauma, researchers found that after a single collegiate football game, which involves repetitive head hits (RHHs), changes to glial fibrillary acidic protein (GFAP) correlated with head impact exposure and reduced brain white matter integrity in 30 Division III college football players two days later.

Bazarian et al. identified correlations between GFAP elevations in blood samples and the “number of hits, total linear acceleration, and total rotational acceleration captured by helmet impact sensors” and reduced white matter integrity two days later. Diffusion tensor imaging (DTI) showed a decline in fractional anisotropy (FA) in the fornix and corpus callosum, two key brain regions associated with cognition and information transfer between brain regions. (FA measures the level of water diffusion in the brain as a proxy for white matter integrity.) Researchers theorize that GFAP “may be a biologically relevant indicator of the brain’s acute response to non-concussive head impacts during a single sporting event.” 

The rotational forces from head impacts physically strain and activate astrocytes, a type of brain cell that performs essential metabolic and neuroprotective functions. The strained and activated astrocytes release GFAP and swell, limiting water movement between the axons. This astrocyte activation and swelling contribute to the lowering of FA, indicating a possible relationship between head impact exposure and reductions in white matter integrity.

Focusing on a single Division III National Collegiate Athletic Association football game, the research team took blood samples from 30 football players at the University of Rochester. The researchers took blood samples at three different time points: immediately before the game, immediately after the game, and 45 minutes after the game. They performed DTI and had athletes complete a symptoms checklist 24 hours before the game and 48 hours after the game. Additionally, helmet and body exertion impact sensors were used to monitor the athletes during the game. 

Developing tools to measure neurological responses to RHHs could lead to the creation of effective and personalized strategies at the individual level. Further research is needed to validate the findings with a larger sample size.