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Young athletes playing contact sports may experience learning and memory deficits as well as brain changes even when jolts to the head don’t trigger a concussion, a study shows. It's unclear whether the damage is long-term, but neurologists say the findings give an "important" new understanding of the brain risks some young players face.
After a single season of football or hockey, players who experienced the most hits to the head or body appeared to have developed problems with memory and cognition, according to the study published online Wednesday in Neurology. Those players were also the ones who showed changes on brain scans designed to look at the “integrity” of a person’s white matter. The white matter sits just under the gray matter and is made up of axons, or nerve fibers, which are the brain’s communication cables.
Even when there is no diagnosis of concussion, hits that jolt the brain can lead to changes in white matter," said Dr. Thomas McAllister, professor and chair of the department of psychiatry at the Indiana University School of Medicine. “And [the changes] are related to the frequency and intensity of hits. And the degree of change is correlated with poorer performance on a measure of cognition.”
McAllister, who was lead researcher at Dartmouth College’s Geisel School of Medicine when the research was performed, and colleagues rounded up 80 concussion-free varsity football and ice hockey players and scanned them at the beginning of the season with a new type of MRI. The players also took a two-and-a- half-hour test of cognition and memory.
For comparison, the researchers ran the same tests on 79 athletes who competed in non-contact sports, such as swimming, track, and crew.
The helmets of the football and hockey players were equipped with sensors that could keep track of how hard players were hit.
At the end of the season, when all the athletes were rescanned and retested, researchers observed brain changes in those who played contact sports. And the size of those changes correlated with the number of jolts to the head experienced by a player.
The researchers also found a subgroup of players who performed worse on tests of memory and cognition. This subgroup also showed bigger changes in the corpus callosum, a bundle of nerve fibers that connect the left and right hemispheres of the brain.
“We may be seeing a group of athletes who are more vulnerable to impacts because of physiological or genetic differences,” McAllister said.
If researchers can figure out who is most vulnerable to long-term damage from jolts to the head, they might be able to advise those at risk to eschew contact sports, he said.
Brain injury experts called the new study “important” and “timely,” but there is some disagreement on how worrisome the findings are.
“I think this is the next big bomb to drop,” said Dr. Robert Cantu, a professor of neurology and neurosurgery at the Boston University School of Medicine and co-director of the Center for the Study of Chronic Traumatic Encephalopathy. “This study shows that you can have brain injury without a recognized concussion. What we don’t know yet is whether the effects are transient or not.”
Dr. Joseph Maroon noted kids playing contact sports weren’t different from those engaging in non-contact sports at the beginning of the season.
“Many of those athletes played before and had head contact,” said Maroon, a professor of neurosurgery at the University of Pittsburgh Medical Center and team neurosurgeon for the Pittsburgh Steelers. “So that means the changes had cleared during the off season.”
That wasn’t as comforting to Dr. Douglas Smith, a professor of neurosurgery and director of the Center for Brain Injury and Repair at the University of Pennsylvania Medical Center.
While the brain may heal, it may still show signs of wear and tear, Smith said.
“If your skin gets scratched and heals with a scar, that’s not a problem,” he explained. “If you get the equivalent scar in the brain that is a problem.”
Still, Smith doesn’t want people to panic.
“You have to look at this in a very calm way,” he explained. “Many people after long careers in contact sports go on to become captains of industry, public speakers who are fast on their feet. But there are some who seem to be prone to a poor outcome after just one or two exposures. “
Right now, no one knows which players are more susceptible to lasting damage.
“The bottom line is that families may need to have a dinner conversation,” Smith said. People have to decide for themselves if they want to put their kids’ brains at risk for a game. That’s a tough decision in our society where a lot of heroes are athletes.”