New research shedding new light on why some athletes lose consciousness following sports-related head injury is already helping to influence new safety protocols in sport.
A new study has analysed videos of head impacts in American football players and used computational models to gauge strain and strain rate on the brain following an injury.
Brain strain measures how much brain deformation occurs after injury, whereas strain rate is how quickly the impact took place.
These models were used to compare injuries of athletes who had lost consciousness to those who remained awake to find out what parts of the brain were responsible for a loss of consciousness event.
They found that athletes who became unconscious experienced injuries involving head impacts at higher speeds.
The brainstem regions of the brain also experienced higher forces, or brain strain, during these impacts, which suggests this region plays a part in losing consciousness after a head injury.
And already the Imperial College London findings are already having an impact on the guidelines around rugby.
Dr Simon Kemp, medical services director of the England National Rugby Union (RFU) and co-author, said: “These computational study findings were a factor that influenced World Rugby (the International Federation) in 2022 to update the Graduated Return to Play Guidelines and specifically the decision to mandate a minimum return of 12 days for all players who had lost consciousness (criteria one cases) and not allow them to return in a minimum of seven days.”
The study reviewed over five years of footage of more than 1,000 National Football League American football games to find 41 videos where neurological events, such as lack of consciousness or severe head injury, were seen.
The videos guided physical reconstructions of the impacts at the University of Ottowa Neurotrauma Impact Science Laboratory, where a male model head fitted with an American football helmet and shoulder pad was used to generate head-to-head collisions. This model was used to capture the movement of the head during impact.
The data from these physical head impacts were then fed into the Imperial College London 3D finite element model of the human head to measure how much strain was put on the brain, and which regions were associated with loss of consciousness.
Dr Karl Zimmerman, lead author of the research from Imperial’s Department of Brain Sciences said: “Our results using computational models of brain injuries match up with what has been seen when looking at real, damaged brains.
“These results provide further evidence of what brain structures are responsible for consciousness, and highlights the use of computational models when looking at outcomes after injuries to the brain.”
“The results help us understand the neurological reasons why some players lose consciousness after head impacts,” said author Professor David Sharp, centre director at the UK DRI Care Research & Technology Centre and associate director of the Imperial Centre for Injury Studies.
“It suggests that a key factor is how much strain is placed on brain regions involved in maintaining arousal.
“Moving forwards, we may be able to predict what type of head impact might produce neurological problems and use this information to reduce this risk.”
Dr Mazdak Ghajari, co-author at the HEAD lab at the Dyson School of Design Engineering, added: “Our engineering computational models provide new predictions of brain deformation during the few milliseconds of head collisions, but linking these predictions with neurological symptoms could only be done by our top neuroscientists and through hours of passionate discussion and adopting common language.”
