When he was on the baseball field, Ryan Freel was unafraid to fling his body, and his head, into plays -- diving after balls and crashing into outfield walls.
That fearlessness earned the undersized Freel a spot in the big leagues, as well as a raft of concussions.
Now, nearly a year after his death, Freel has the distinction of being the first Major League Baseball player to be diagnosed with chronic traumatic encephalopathy (CTE), according to researchers at the Boston University School of Medicine.
"The real important issue is that he hit his head multiple times -- small hits, big hits, in baseball and outside of baseball," said Robert Stern, co-founder of the Center for the Study of Traumatic Encephalopathy at BU.
"When it comes to the development of CTE, our current sense is that it requires repetitive brain trauma and not just a couple of big concussions."
Freel committed suicide last December at the age of 36.
Testing of his brain tissue after death -- the only way to definitively diagnose CTE -- found that he had Stage 2 CTE, which is associated with erratic behavior and memory loss. Stage 4, the worst possible expression of the disease, is associated with full-blown dementia, aggression and paranoia.
The brain tissue of people found to have CTE displays an abnormal build-up of tau -- a protein that, when it spills out of cells, can choke off, or disable, neural pathways controlling things like memory, judgment and fear.
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