Correlation of Concussion Symptom Profile with Head Impact Biomechanics: A Case for Individual-Specific Injury Tolerance.

Concussion is a brain injury induced by biomechanical forces that is broadly defined as a complex pathophysiological process affecting the brain. The intricate link between biomechanical input and concussion injury response is poorly understood. We aimed to test the hypothesis that greater biomechanical forces would result in the presentation of more concussion-related symptoms that would take longer to resolve. The objective of this study was to investigate the relationship between an array of biomechanical parameters measured for concussive impacts and the presentation and resolution of concussion symptoms. A total of 319 collegiate football players from six universities were recruited to participate in this study. Certified athletic trainers and/or team physicians at each site diagnosed and treated concussions sustained by subjects through participation in football. The subjects' helmets were instrumented with accelerometer arrays that measured linear and rotational head accelerations for each impact experienced during games and practices. Correlations between biomechanical measurements associated with concussion symptom presentation and recovery were quantified. A total of 22 subjects collectively sustained 25 concussions, with three subjects sustaining two concussions each. Biomechanical measures associated with injury were not found to be correlated with number of symptoms, Sport Concussion Assessment Tool 3 Symptom Severity Score, or time to symptom resolution. Linear and rotational accelerations associated with injury were not correlated with symptom severity for any of the 22 individual symptoms evaluated. Further, we found no association between impact location and presence of any individual symptom when ignoring severity grade. While concussive impacts did not stand out relative to impacts that did not result in injury, concussive impacts were among the most severe for each individual player. This suggests tolerance to head acceleration might be individual-specific, meaning similar biomechanical inputs can produce different injury presentations between individuals. Future investigations should consider individual-specific analyses of tolerance to head acceleration and injury response.