Mechanics of a Twisted Brain

Valentina Balbi

In a recent study published on Soft Matter we discovered that side impacts to the head can be just as dangerous as frontal impact.

With a team of researchers in NUI Galway and University College Dublin we measured the effects of rotational accelerations of the head, such as those experienced in football headers, boxing hooks, side impacts, etc. We found stretches and stresses in the brain as high as those generated by 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 damage neurons and lead to concussion, brain injury and even permanent damage.

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

Using advanced torsion techniques we were able to measure the twisting properties of brain matter. We then fed the data into computer simulations of a rotational acceleration of the head typical of a boxing punch.

We found that large shear forces develop in the horizontal plane, as expected. However, 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.

Rotational accelerations are in fact as likely to happen in everyday life as linear accelerations. In a frontal collision car accident, the head rotates forward and backward (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. Our research shows that rotational accelerations create pressure and forces of the same magnitude in all directions, which could have grave implications for traumatic brain injury.

This is a joint work with Professor Michel Destrade, Chair of Applied Mathematics at NUI Galway, and Dr Aisling Ní Annaidh and Dr Antonia Trotta from the School of Mechanical and Materials Engineering at UCD. If you would like to know more about this project, please visit this link.

Valentina Balbi, Michel Destrade, Aisling Ní Annaidh and Antonia Trotta
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