Mechanics of a twisted brain: How side impacts to the head can be as damaging as frontal impacts

Side impacts to the head can be just as dangerous as frontal impacts, new research suggests, which was published this week in the international scientific journal Soft Matter.

A research team from NUI Galway and UCD measured the effects of rotational accelerations (side impacts) of the head, such as those experienced in football headers, boxing hooks and side impacts. They found stretches and stresses in the brain as high as those of linear accelerations (frontal impacts, whiplash).

Large motions can occur in the brain when the human head is accelerated violently by an impact, be it accidental or even voluntary as in a football header. The resulting mixture of pressure, stretch, shear and twist can impair neurons and lead to concussion, brain injury and even permanent damage.

A lot of research has focused on the effects of linear accelerations (frontal impacts) of the brain, such as those happening in frontal collisions, such as car accidents and American football.

Rotational accelerations (side impacts) are in fact as likely to happen in modern life as linear accelerations (frontal impacts). In a frontal collision car accident, the head rotates forward and backwards (whiplash). Similarly, for many football headers, or for uppercuts in combat sports. These sports also involve rotations of the head about the vertical axis or tilting from one side to the other.

Linear accelerations are expected to create large stresses and stretches in the direction of the impact. This research shows that rotational accelerations (side impacts) create pressure and forces of the same magnitude in all directions, which could have grave implications for traumatic brain injury.

The researchers at NUI Galway and UCD measured the twisting properties of brain matter using advanced torsion techniques. They then fed the data into computer simulations of a rotational acceleration of the head, typical of a boxing punch.

Dr Valentina Balbi led the study from NUI Galway (now a Lecturer of Industrial and Applied Mathematics at University of Limerick) with co-authors Professor Michel Destrade, School of Mathematics, Statistics and Applied Mathematics at NUI Galway, and Dr Aisling Ní Annaidh and Dr Antonia Trotta from the School of Mechanical and Materials Engineering, University College Dublin.

Commenting on the findings, Dr Balbi, said: “We found that large shear forces develop in the horizontal plane, as expected. But we also found that a high-pressure level and large vertical forces also develop in the brain, especially in the frontal cortex, as a result of the twisting motion.”

Mark Ganly, CEO of Contego Sports, a company that developed the N-Pro Rugby head guard, which is scientifically proven to provide impact protection, said: “We are keenly aware of the dangers of impacts in the game. This research confirms my intuition that it is crucial to protect Rugby players from side impacts as well as from frontal impacts to the head. In my experience, they are just as likely to lead to concussion or mild traumatic brain injury.”

To read the full study in the journal Soft Matter, visit: https://doi.org/10.1039/c9sm00131j