Growing awareness of the severe and enduring impacts of strong hits to the head, such as concussions, traumatic brain injury (TBI) and neurological disorders, have led researchers to focus on what exactly happens inside a skull during a big hit.
Mehmet Kurt, Ph.D., a mechanical engineer at Stevens Institute of Technology who studies the biomechanics of the brain and the skull at rest and during rapid head movements, has now bioengineered simulations that track how the brain behaves upon impact, reconstructing the inertial stresses and strains that prevail inside a brain that’s just been hit hard from the side.
“The brain not only rings, but it has a distinct pattern of ringing when the head is hit from the side and experiences rotational acceleration,” said Kurt.
The new findings may not only have implications for brain injury assessment, but for sports helmet makers in search of measurements that can simply distinguish ‘concussion’ from ‘no concussion’ to help the industry set safety standards.
For the study, the research team analyzed both simulated and human data of brain movements that have led to concussions.
The team found that side impacts to the head lead to rotational accelerations that cause mechanical vibrations to concentrate in two brain regions: the corpus callosum, the bridge that links the hemispheres, and the periventricular region, white matter lobes at the brain’s root that help speed muscle activation.
The researchers discovered that the skull’s internal geometry and the gelatinous nature of the brain cause these two regions to resonate at certain frequencies and receive more energy in the form of shearing forces, or opposing motions, than the rest of the brain.
More shear strain seems to yield more tissue and cell damage, particularly since shear tends to deform brain tissue more readily than other biological tissues.
“A hit to the head creates non-linear movement in the brain,” said Stevens graduate student Javid Abderezaei. “That means that small increases in amplitude can lead to unexpectedly big deformations in certain structures.”
These non-linear vibrations are not surprising in a complex organ featuring a range of tissue densities. Add in the restraining effects of the tough protective membranes that hold the brain in place from both above and below, and certain regions are bound to come off worse in side hits.
Identifying the parts of the brain that are most vulnerable in side impacts makes them prime targets for further investigation.
The findings, published in the journal Physical Review Applied, have strong implications as more than 300,000 American children and teenagers suffer sports-related concussions every year.
Source: Stevens Institute of Technology