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One Concussion-Free Football Season Can Still Damage Players’ Brains

A new study found that more than two-thirds of subjects experienced a decrease in structural integrity of the brain by the end of the college season

Players who sustained a high number of subconcussive hits suffered more midbrain tissue damage (Hirad et al.)
smithsonian.com

In just one season of college football, 38 players from the University of Rochester’s Division III team sustained a collective 19,128 hits to the head. Two of these encounters resulted in formal concussions, but the majority of hitsranging in intensity from “small dings to hard slams,” according to the New York Times’ Gretchen Reynolds—were not serious enough to warrant clinical diagnosis.

Despite the prevalence of ostensibly less harmful head injuries, a new study published in the journal Science Advances reports that more than two-thirds of the athletes experienced a discernible decrease in the structural integrity of their brain by the end of the season. As co-author Adnan Hirad, a doctoral candidate at the university medical center, tells the Times, the researchers observed a “kind of fraying” of white matter tissue in subjects’ midbrain, a section of the brainstem responsible for controlling motor functions of the eyes and ears.

The team’s findings suggest that football players can sustain traumatic brain injuries even without suffering concussions. Per Science magazine’s Eva Frederick, subconcussive hits incurred repeatedly over time can be just as damaging as the better-known injury, which manifests as a cluster of symptoms including loss of consciousness, headache, dizziness, disorientation and ringing in the ears.

Although it can be difficult to pinpoint the exact location of a brain injury, study co-author Jeffrey Bazarian, also of the University of Rochester Medical Center, says that regardless of where the head is hit, the force of impact is always translated into the midbrain.

In a press release, he adds, “Midbrain imaging might be a way in the future to diagnose injury from a single concussive head hit, as well as from repetitive sub-concussive head hits.”

According to Bradford Mahon, a psychologist at Carnegie Mellon University and scientific director of the University of Rochester’s Program for Translational Brain Mapping, the midbrain serves as a “canary in the coal mine” for brain injuries. If midbrain tissue is damaged, Mahon tells the Times, it’s likely that other brain sections have been affected and potentially harmed.

To measure the impact of repeated head hits, the scientists fitted players’ helmets with specialized accelerometers capable of tracking the frequency and intensity of encounters. As the study notes, 59 percent of injuries were sustained during practice, while 37 percent took place during competition and another 4 percent occurred during scrimmages and various meetings.

Speaking with Science’s Frederick, Hirad explains that the brain, much like the surface of a pond after a rock is thrown, ripples when hit from any angle. Based on data garnered from brain scans conducted pre- and post-season, repeated rotational hits, in which the head twists from side to side or front to back, proved more damaging to the midbrain than linear, or head-on, acceleration. The results, Justin Murphy reports for the Rochester Democrat and Chronicle, showed that subjects who experienced the highest number of hits subsequently suffered more midbrain damage.

Interestingly, the Times’ Reynolds writes, the researchers further found that brain scans of 28 athletes who had been recently diagnosed with a concussion mirrored those of the football players studied, demonstrating a “slight disintegration” in the midbrain’s white matter.

Because the scientists did not re-scan players’ brains following the post-season tests or assess participants’ thinking and motor skills, it remains unclear how the brain injuries affected daily life and whether the white matter eventually returned to normal. Given the fact that pre-season scans of veteran athletes did not show white matter disintegration, Mahon says it is likely injured players experienced at least “some healing.”

Moving forward, Murphy notes that the researchers hope to create a real-time monitoring system capable of assessing players on the field, as well as gather crowdsourced data through their Open Brain Project portal.

“Public perception is that the big hits are the only ones that matter,” Mahon concludes in a statement. “The big hits are definitely bad, but the public is likely missing what’s causing the long-term damage in players’ brains. It’s not just the concussions. It’s everyday hits, too. And the place to look for the effect of such hits, our study suggests, is the midbrain.”

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