New reports of brain damage to soccer and rugby players are leading to a re-think of how jiggling the brain during a game could lead to the kind of long-term damage long associated with slam-bang sports like football and boxing. But medical researchers aren't yet ready to call for the end of contact sports.
Some athletes get hit hard many times and don't develop conditions such as chronic traumatic encephelopathy (CTE), the disease diagnosed in Major League Soccer player Patrick Grange, who died in 2012 and a former pro Australian rugby player, Barry Taylor, who died in 2013. Those who do could have some kind of genetic susceptibility to developing these injuries or a pre-disposition that isn't yet well understood.
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Patients with CTE have an abnormal build-up of protein that can block or disable neural pathways controlling things like memory, judgment and fear. CTE can be diagnosed only after death and has been linked to psychological problems such as depression, anxiety and substance abuse.
But researchers still don't know whether athletes should be worried about big hits that cause concussions, or smaller "pre-concussive" collisions that occur as a routine part of the game.
"This area is a rush to judgment over what we know or don't know," said Thomas McAllister, chairman of the department of psychiatry at Indiana University and a leading expert in traumatic brain injuries. "Because there is a lot we don't know."
McAllister explained that scientists have known about the dangers of getting hit on the head since the 1920s when they diagnosed a form of dementia in boxers. They called it neurologica pugilistica. In recent years, the same condition has become known as CTE.
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Last year, McAllister and his colleagues completed a study of NCAA football players over the course of a season, as compared to a similar group of track and field athletes. They tested both groups for cognition and memory, as well as performed sophisticated diffusion tensor imaging of their brains. While they all performed equally on the tests, they found about one in five football players experienced changes to a part of their brain called the corpus collossum, which lies in the middle of the two hemispheres.
McAllister said the degree of change was related to how hard and how much they were hit during the season, something measured with small accelerometers implanted into the helmets.
"All we can say with our data is something changed over the course of season," McAllister said. "We don't know if we studied them five or ten years later, if they would be doing alright. It's possible (the changes) may heal or reverse themselves during the off season, but we don't know."