Even subconcussive blows to the head can cause brain damage
The brain scans of high school football and hockey players showed subtle injury -- even if they did not suffer a concussion – after taking routine hits to the head during the normal course of play, according to a University of Rochester Medical Center study.
The research, reported online in the journal Magnetic Resonance Imaging, raises powerful questions about the consequences of the mildest head injury among youths with developing brains, said lead author Jeffrey Bazarian, M.D., M.P.H., associate professor of Emergency Medicine at URMC with a special interest in sports concussions.
The study utilized diffusion tensor imaging (DTI), which is similar to an MRI study but measures the function of the brain rather than looking at its structure.
“Although this was a very small study, if confirmed it could have broad implications for youth sports,” Bazarian said. “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 URMC 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. However, that becomes a problem when searching for very subtle changes, Bazarian said, because so much natural variation exists in every individual’s brain.
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 determine the extent of axonal injury.
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