Researchers probe the complex nature of concussions

Concussion is a major public health problem, but not much is known about the impacts that cause concussion or how to prevent them. A new study suggests that the problem is more complicated than previously thought.

- By Nathan Collins

David Camarillo

It seems simple enough: Taking a hard hit to the head can give you a concussion. But in most cases, the connection is anything but simple, according to a new study led by researchers at Stanford University.  

Combining data recorded from football players with computer simulations of the brain, the researchers found that concussions and other mild traumatic brain injuries seem to arise when an area deep inside the brain shakes more rapidly and intensely than surrounding areas. But they also found that the mechanical complexity of the brain means there is no straightforward relationship between different bumps, spins and blows to the head and the likelihood of injury.

A paper describing the findings was published March 30 in Physical Review Letters. David Camarillo, PhD, assistant professor of bioengineering, is the senior author. Lead authorship is shared by former postdoctoral scholars Mehmet Kurt, now an assistant professor of mechanical engineering at the Stevens Institute of Technology, and Kaveh Laksari, now an assistant professor of biomedical engineering at the University of Arizona.

“Concussion is a silent epidemic that is affecting millions of people,” Kurt said. Yet exactly how concussions come about remains something of a mystery.

“What we were trying to do is understand the biomechanics of the brain during an impact,” Kurt said. Armed with that understanding, engineers could better diagnose, treat and hopefully prevent concussion, he said.

Shaking the brain

In previous studies, Camarillo’s lab outfitted 31 college football players with special mouth guards that recorded how players’ heads moved after an impact, including a few cases in which players suffered concussions.

Laksari and Kurt’s idea was to use that data, along with similar data from NFL players, as inputs to a computer model of the brain. That way, they could try to infer what happened in the brain that led to a concussion. In particular, they could go beyond relatively simple models that focused on just one or two parameters, such as the maximum head acceleration during an impact.

The key difference between impacts that led to concussions and those that did not, the researchers discovered, had to do with how — and more importantly where — the brain shakes. After an average hit, the researchers’ computer model suggests the brain shakes back and forth around 30 times a second in a fairly uniform way; that is, most parts of the brain move in unison.

In injury cases, the brain’s motion is more complex. Instead of the brain moving largely in unison, an area deep in the brain called the corpus callosum, which connects the left and right halves of the brain, shakes more rapidly than the surrounding areas, placing significant strain on those tissues.

Further complications

Concussion simulations that point to the corpus callosum are consistent with empirical observations: Patients with concussions do often have damage in the corpus callosum. However, Laksari and Kurt emphasize that their findings are predictions that need to be tested more extensively in the lab, either with animal brains or human brains that have been donated for scientific study. “Observing this in experiments is going to be very challenging, but that would be an important next step,” Laksari said.

Concussion is a silent epidemic that is affecting millions of people.

Perhaps as important as physical experiments are additional simulations to clarify the relationship between head impacts and the motion of the brain — in particular, what kinds of impacts give rise to the complex motion that appears to be responsible for concussions and other mild traumatic brain injuries. Based on the studies they have done so far, Laksari said, they know only that the relationship is highly complex.

Still, the payoff to uncovering that relationship could be enormous. If scientists better understand how the brain moves after an impact and what movement causes the most damage, Kurt said, “we can design better helmets, we can devise technologies that can do onsite diagnostics, for example in football, and potentially make sideline decisions in real time,” all of which could improve outcomes for those who take a nasty hit to the head.

Camarillo is a member of Stanford Bio-X, the Child Health Research Institute and the Stanford Neurosciences Institute.

Researchers from the University of Pittsburgh and KTH Royal Institute of Technology in Huddinge, Sweden, also contributed to the study.

The study was supported by the Child Health Research Institute, the Lucile Packard Foundation for Children’s Health, Stanford’s Clinical and Translational Science Award and the Thrasher Research Foundation.

Stanford’s Department of Bioengineering, which is jointly managed by the School of Medicine and the School of Engineering, also supported the work.

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