Differences In Strain Distribution Across Brain Regions In Non-concussive Collegiate Football Head Impacts

Impacts to the head are a known mechanism of concussion, but can also elicit damage in the absence of a diagnosed injury. The deformation, or strain, experienced by the brain may be able to explain such damage but has not been described comprehensively. PURPOSE: To describe the distribution of strain across various brain regions as a result of non-concussive head impacts sustained in football. METHODS: Head acceleration events were collected from collegiate football players over five competitive seasons. Instrumented mouthguards recorded acceleration events above 10 g; true head impacts were identified using machine learning algorithms and video verification. The maximum brain strains were estimated using a deep learning model and projected to specific brain regions. RESULTS: Impacts were obtained from 45 athletes over a total of 1369 player-sessions. For a preliminary dataset of 209 verified impacts, the median and inter-quartile range for the peak linear and angular accelerations were, respectively: 21.07 [14.74 - 26.85] g and 1135.94 [908.47 - 1599.85] rad.s-2. The median 95th percentile of the maximum principal strain value (MPS95) for the whole brain was 6.2 [5.1 - 7.7] %. The MPS95 varied across brain regions (p < 0.001), with the strains in the midbrain, grey matter, white matter, and corpus callosum being significantly higher than in the thalamus, brainstem and cerebellum. CONCLUSION: Maximum strains are not equally distributed throughout the brain upon an impact, suggesting some regions of the brain may be subjected to more damage. Further analysis is needed to verify if such observations are associated with changes that can be measured using imaging techniques or neurocognitive tests.