In an ESPN exclusive, Alyssa Roenigk reveals that Dave Mirra's brain was found to have CTE. The finding is the first for an action sports athlete. Today, Roenigk and Kevin Robinson join Outside The Lines to discuss Dave Mirra's life and legacy. (6:54)

BMX icon Dave Mirra, who died in February, suffered from the type of chronic brain damage that has shown up in the brains of dozens of football players, a University of Toronto neuropathologist has concluded. Multiple neuropathologists confirmed the diagnosis.

Mirra is the first action sports athlete to be diagnosed with chronic traumatic encephalopathy, a neurodegenerative disease that can lead to dementia, memory loss and depression. He died on Feb. 4 from a self-inflicted gunshot wound.

The tau protein deposits found in Mirra's brain were indistinguishable from the kind that have been found in the brains of former football and hockey players with CTE, Dr. Lili-Naz Hazrati, the Toronto neuropathologist, told ESPN The Magazine.

"I couldn't tell the difference," she said. "The trauma itself defines the disease, not how you got the trauma."

The trademark tau protein deposits were found in the frontal and temporal lobes of Mirra's brain.

"It's assumed it is related to multiple concussions that happened years before," she said.

Mirra, who was 41, suffered a fractured skull when a car hit him at age 19, and he dabbled in boxing after his retirement from BMX. But he also endured countless concussions during his BMX career, beginning at a young age.

A legend in freestyle BMX, Mirra was the face of his sport to the mainstream. Until 2013, he owned the record for the most X Games medals in history with 24. He also had a successful video game series and hosted a show on MTV. After retiring from competitive BMX in 2011, Mirra competed in the sports of rallycross and triathlon.

After his death, Mirra's family decided to have his brain studied for CTE. At the request of the Mirra family, Hazrati sent images of her prepared slides, without background information or Mirra's name attached, to additional U.S. and Canadian neuropathologists for their opinions. Each confirmed Hazrati's diagnosis of CTE.

"It validates what we have been thinking about brain injuries in boxers and football players," Hazrati said. "The key is brain injury. Regardless of how you get it, through BMX or hockey, you are at risk for this."

CTE is a progressive disease associated with repeated head trauma. Although long known to occur in boxers, it was not discovered in football players and other athletes until 2002.

Mirra's widow, Lauren, received the diagnosis about her late husband in March. In an exclusive interview with ESPN The Magazine for its June 6 issue, she spoke about Mirra's diagnosis and legacy, and she detailed personality changes in his final year.

"I started to notice changes in his mood. And then it quickly started to get worse," Lauren said. "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. 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?'

"This is the beginning of bringing awareness. It would be amazing if this is something we can detect in life one day. If we can detect it, prevent it, stop it, let's do all of the above."

CTE can be diagnosed only after death, though many researchers are working on tests to diagnose it in the living.

Mirra will be inducted into the National BMX Hall of Fame in Chula Vista, California, on June 11. He will also be honored June 4 during this year's X Games in Austin, Texas, with a new event named for him, the Dave Mirra BMX Park Best Trick competition. The winner will be awarded the Mirra Golden Pedal and prize money.

ESPN owns and produces the X Games, which had no comment on Mirra's diagnosis.