Matthew B. Panzer
by Matthew B. Panzer, PhD
At the University of Virginia Center for Applied Biomechanics, we are focused on studying how injuries occur during impact events so we can develop technologies needed to mitigate injury in sports, automotive crashes and the military.
We operate under the Ben Franklin axiom that, “an ounce of prevention is worth a pound of cure,” and we apply this premise regarding the brain: Preventing a traumatic brain injury (TBI) is better than treating one. But effective prevention demands that we understand what happens to the brain during an impact that causes TBI — and that isn’t so simple to figure out.
No visible damage with mild TBIs
After a moderate to severe TBI, internal bleeding may be visible on a CT scan. However, with most mild TBIs (like concussions), there is no visible structural damage. That doesn’t mean structural change isn’t happening — it’s just occurring at a microscopic level that we can’t detect with standard diagnostic imaging. Instead, we have to rely on a combination of animal studies, human donor studies and computer modeling to evaluate how rapid head motions might affect neural tissue, the meninges (or membranes that protect the brain) and the skull, and the deformations of these tissues in turn might affect the neurological response to injury.
One of the things we have learned is that rapid rotation of the head induces considerably more brain strain than linear motions. Rapid head rotation induces deformations in the brain that can cause microscopic stretching and shearing of neurons, which can then trigger a whole cascade of neurological and biochemical processes. These processes evolve over time, from the initial seconds after impact to months or even years later.
What happens to the brain when hit
You might imagine that when someone gets hit in the head, the brain crashes into the skull and then ricochets back to the other side, bouncing around in the skull causing damage. But that is a myth — there is simply not enough room in the skull for the brain to do this. Rather, the outer portions of the brain move quickly with the skull within a few milliseconds of the impact, while the inner portions are relatively stationary. This subtle motion differential is what induces neuron strains. The inner parts of the brain will “catch up” with the motion of the outer parts, sometimes even overshooting the outer motion. This back-and-forth motion of brain tissues makes the brain appear to jiggle.