In some cases, a concussion can be hard to dia…

In some cases, a concussion can be hard to diagnose because the symptoms unfold slowly over time. That’s often true of subconcussive impacts which result from lower impact jolts to the head than those that cause concussions. This category of injury doesn’t cause noticeable symptoms right away, but can lead to severe degenerative brain diseases over time if it happens repeatedly. 

Take soccer players, who are known for repeatedly heading soccer balls. Using a technique called Diffusion Tensor Imaging, we’re beginning to find out what effect that has on the brain. In 2013, researchers using this technique discovered that athletes who had headed the ball most, about 1,800 times a year, had damaged the structural integrity of their axon bundles. The damage was similar to how a rope will fail when the individual fibers start to fray. 

Those players also performed worse on short-term memory tests, so even though no one suffered full-blown concussions these subconcussive hits added up to measurable damage over time In fact, researchers know that an overload of subconcussive hits is linked to a degenerative brain disease known as Chronic Traumatic Encephalopathy, or CTE. People with CTE suffer from changes in their mood and behavior that begin appearing in their 30s or 40s followed by problems with thinking and memory that can, in some cases, even result in dementia.

From the TED-Ed Lesson What happens when you have a concussion? – Clifford Robbins

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