The force exerted on the brain during traumatic injury is linked to damage years after the initial event, research has revealed.
Findings of the new study have been hailed as having the potential to predict the severity of brain injuries and help influence new approaches going forward, particularly in the field of sport.
TBI has a number of immediate impacts, including physical effects like unconsciousness and bleeding, alongside the ‘hidden’ symptoms of memory loss, mood and personality changes, which may take much longer to develop.
However, the link between the mechanical forces that act on the brain during TBI and the resulting long-term changes is poorly understood.
Now, researchers from Imperial College London have shown a clear link between the forces acting on the brain during TBI and its associated long-term changes.
The study – ‘From biomechanics to pathology: predicting axonal injury from patterns of strain after traumatic brain injury’, which is published in Brain – combined a computational model of brain injury with experimental studies on rat brains.
“The initial damage during a traumatic brain injury takes only milliseconds to occur, but it triggers many changes that result in ongoing effects which can be felt years later,” says Dr Mazdak Ghajari, from the Dyson School of Design Engineering.
“Understanding the link between the two is crucial for predicting who is at risk for long-term damage, and how protection may be better designed to prevent this damage.”
The findings have the potential to make positive impacts in protective equipment, such as in the design of helmets.
Professor David Sharp, from the Department of Brain Sciences, says: “We are also looking at how the type of impacts experienced by American football players affects whether they lose consciousness, and whether new helmet designs might protect soldiers from the effects of blast waves following explosions.
“These types of studies can also help explain whether repeated small impacts, such as heading the ball in football, could lead to similar long-term brain injury.”
Previously, the team had built a human computer model to predict the location of long-term brain damage following TBI, focusing on the ‘white matter’ of the brain, which contains nerve fibres called axons which play a large role in the brain networks that are altered in long-term brain damage.
Now, they have tested this modelling approach to see if it can accurately predict the pattern of white matter damage in rats given mild or moderate TBI.
They simulated the rats’ brains during injury, revealing the location and duration of mechanical forces linked to damage. Using a precise experimental model, this damage was induced in the rat brain and followed up after several weeks, which correlates to years of changes in a human brain.
They found that the effect of shear stresses on the white matter helped to predict the location of long-term damage. Shear stresses push two parts of the same object, in this case the brain, in different directions.
The intensity of the shear at different locations caused by different impacts, for example what angle they come from, predicts where the most severe white matter damage will occur. This could potentially help doctors predict the likely long-term effects in patients who have suffered a TBI.
“Different types of injuries will cause different kinds of shear. With this new model we can now more accurately predict which injuries will cause severe, long-term damage, and potentially avert it,” continues Dr Ghajari.
“For example, motorbike accidents involve a lot of rotational movement, which causes lots of shear. We are studying dozens of bike helmets to see which best protect against excess rotation.”
