The X Games star was found dead of an apparent self-inflicted gun wound in February.
BMX biker Dave Mirra was suffering from chronic brain damage before he took his own life in February.
The 41-year-old X Games gold medal winner has been posthumously diagnosed with C.T.E. (chronic traumatic encephalopathy), a brain disease found in a number of football players that is linked to head trauma, according to ESPN.
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The C.T.E. was found by neuropathologists at the University of Toronto and the Canadian Concussion Center. "It's assumed it is related to multiple concussions that happened years before," Dr. Lili-Naz Hazrati told ESPN.
Mirra endured a number of accidents for his sport, including one leading up to the Summer X Games in 2006 that he called the "worst crash ever." "I basically fell 16 feet straight to my head," he told Men's Health magazine.
C.T.E. is a degenerative disease that can lead to dementia, memory loss and depression. His wife, Lauren Mirra, told ESPN she began to "notice changes in his mood" that "started to get worse."
"He wasn't able to be present in any situation or conversation, so it was hard to be in a relationship with him to any degree," she said. "He was lost. I looked straight through him on a few occasions. And I was like, 'Where are you? Where are you? What is wrong?'"
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Mirra, who was also the former host of MTV's The Challenge, was found dead in Greenville, North Carolina, "with an apparent self-inflicted gunshot wound," police said at the time. He is survived by his wife and two children.
Hear Tony Hawk and Carey Hart's touching words remembering Mirra in the video below.