U. ROCHESTER (US) — Brain scans of high school football and hockey players showed subtle injury after routine hits to the head during normal play.
The research, reported online in the journal Magnetic Resonance Imaging, is preliminary, involving only a small sample of athletes, but raises significant questions about the consequences of the mildest head injury among youths whose brains are still developing, researchers say.
Scientists used a statistical approach to analyze before-and-after images of the players’ brains from diffusion tensor imaging (DTI) and detected the small but noteworthy change in the white matter of the affected teenagers. A DTI scan is similar to an MRI but instead of relaying pictures, it captures and relays quantitative data that must be decoded and interpreted.
“Although this was a very small study, if confirmed it could have broad implications for youth sports,” says Jeffrey Bazarian, associate professor of emergency medicine at the University of Rochester.
“The challenge is to determine whether a critical number of head hits exists above which this type of brain injury appears, and then to get players and coaches to agree to limit play when an athlete approached that number.”
Nine athletes and six people in a control group from Rochester, N.Y., volunteered to take part in the research during the 2006-2007 sports season. Among the nine athletes, only one was diagnosed with a sports-related concussion that season, but six others sustained many sub-concussive blows and showed abnormalities on their post-season DTI scans that were closer to the concussed brain than to the normal brains in the control group.
The imaging changes also strongly correlated with the number of head hits (self-reported in a diary), the symptoms experienced, and independent of cognitive test results, Bazarian says.
The study is unique because it was able to compare brain scans from the same player, pre-season and post-season. Most other studies compare the injured brain of one person to the normal brain of another person from a control group. That becomes problematic when searching for subtle changes, Bazarian says, because so much natural variation exists in each individual’s brain.
Indeed, among athletes there is no easy, objective way to diagnose concussions. High schools, colleges, and professional programs routinely administer pre-season, computer-based cognitive tests. Yet some athletes have become adept at tricking the test, Bazarian says. They intentionally do poorly on the baseline so that a mild concussion will not show up if re-tested later.
The DTI scan provides detailed information of axonal injury at the cellular level, by measuring the motion of water in the brain. Axons, which are like cables woven throughout brain tissue, swell up when injury occurs. As the swelling impacts the movement of water, scientists can measure changes in flow and volume and thus make an educated guess at the extent of axonal injury.
Measurements in the current study showed several changes in the brain of the player with the diagnosed concussion; however an intermediate level of changes also occurred among the players who reported anywhere from 26 to 399 total sub-concussive blows. The fewest changes occurred in the control group, as expected.
A key objective of the study was to determine if this statistical approach worked, and the preliminary results showed that white matter changes among the intermediate group were three times higher than the controls.
Efforts to further understand the significance of study results are already underway. Bazarian and collaborators are working on an NFL-funded study of University of Rochester football players. Ten players agreed to wear helmets with special sensors that objectively detect the number of head hits they sustain, the velocity, and angle. Each player also received a pre-season and 2 post-season DTI scans. The data downloaded from the helmet sensors will be correlated with information from the images.
“Our studies are taking important steps toward personalized medicine for traumatic brain injury,” Bazarian says. “In the future we’d like to be able to have a baseline image of a brain and clearly know the significance of changes that occur later.”
Funding was provided by the National Institutes of Health and the UR Health Sciences Center for Computational Innovation.
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