Former pro wrestler Chris Nowinski can pinpoint the moment he realized his days in the ring were over.

"I woke up on the floor of my hotel room after acting out a dream and had fallen off the bed and right through the nightstand," he said from his office outside Boston.

Nowinski, who at 25 was a rising star with World Wrestling Entertainment (WWE), had suffered a concussion in 2003 at a show in Hartford, Conn., and was diagnosed with post-concussion syndrome. He continued to compete for a few months until the incident at the hotel drove home the true dangers of head injuries.

"Concussions don't impair you enough or cause enough pain to stop you from competing," he said. "I was scared because the brain is not something you can fix like a broken leg."

His condition led him to question the education athletes receive about the long-term effects of concussions. His curiosity spurred him, in 2007, to create the Sports Legacy Institute, a non-profit concussion research organization partnered with Boston University.

Former pro wrestler Chris Nowinski in his office at Boston University, where he co-founded the Sports Legacy Institute, a non-profit concussion research organization, in 2007. Steven Senne/Associated Press

"We established SLI first, and the goal was to partner with a top-tier medical school to help conduct the research," he explains. "[BU] had a number of very strong Alzheimer's researchers that we stole."

SLI co-founder Dr. Robert Cantu is the chief of neurosurgery research and director of sports medicine at Emerson Hospital in Waltham, Mass. Cantu says his involvement with Nowinski and SLI stemmed from his belief that head injuries in athletics were not being taken seriously.

"We sensed there was a concussion crisis, and there wasn't adequate awareness, especially in the minds of athletes, parents, coaches," said Cantu.

Nowinski, 32, became aware of this crisis when he read about two athletes who had died and whose brains were found to have sustained substantial trauma throughout their careers.

"I realized this research needed to be done faster," he said. "When I heard about other cases, I reached out to the victims' families and asked them if they would participate."

The families he approached — including that of ex-NFL player Andre Waters, who committed suicide in 2006 — agreed to donate the brains of the deceased athletes to the institute.

Cantu says the research, which now relies on a brain bank with more than 70 donations, proved to be revealing.

"What we've found is evidence of chronic traumatic encephalopathy in all but one [of the] deceased NFL players' brains donated to study," he said. "CTE is a progressive neuro-degenerative disease that is distinct from but shares many features with Alzheimer's, in the sense that an individual in their 40s or 50s progressively develops trouble with memory, especially recent memory, that progresses to dementia."

Deaths of young athletes especially disturbing

Sufferers of CTE also develop difficulty with their emotions, experience depression and exhibit an inability to handle frustrating circumstances. CTE will eventually lead to death.

Recently, Cantu and his team diagnosed CTE in the brain of former NHL tough guy Bob Probert. The Detroit Red Wings alumnus, who struggled with alcohol throughout his career, died last summer. His widow, Dani, donated his brain to CTE research.

"How much is the hockey and how much is the fighting, we don't really know," Cantu told the New York Times. "We haven't definitely established that the skills of hockey as a sport lead to a certain percentage of participants developing CTE. But it can happen to hockey players, and while they're still relatively young."

The institute's researchers have also identified early stages of CTE in the brains of younger athletes, including those of two high school students who died at age 17 and 18, respectively, and a 21-year-old college football player.

Nowinski said he finds these cases the most disturbing.

"These athletes never made any money for playing sports and probably weren't aware this sort of condition was a possibility," he said.

Nowinski cites the case of Owen Thomas as especially troubling. Thomas was co-captain of the University of Pennsylvania football team and hanged himself in September 2010.

"Even in the [Thomas] case, he never had a diagnosed concussion," Nowinski said.

"It tells us that there's a lot we don't understand about even what could be considered 'normal' brain trauma."

According to Nowinski, recent findings like Probert’s diagnosis should not be construed as a criticism of contact sports.

"The diagnosis of CTE in Probert's brain is not necessarily an indictment of hockey, as he received brain trauma during hockey fights as well as outside of sports, including a major car accident," Nowinski said. "Reggie Fleming, the only other NHL player diagnosed with CTE, also was an enforcer, so we need further study before this research can truly inform that ongoing, and important, debate."

Despite all this, significant advances have been made in how head injuries are viewed in sport and the mainstream media.

"I recently read about a children's hospital in Alabama that's seen a three-fold increase in the number of concussions diagnosed in one year, which is extraordinary," Nowinski said. "Those kids used to go back to play too soon and suffered further brain damage.

Magnifications of two sections of an 18-year-old football player's brain show the early onset of chronic traumatic encephalopathy. Boston University

Cantu said that when he first wrote guidelines for judging when a football player who has suffered a concussion should return to the game, in 1986, not too many people were interested in concussion as it related to football.

"In the last year, we've seen it on the front page of Sports Illustrated," he said. "So, you know it's arrived big-time."

Cantu points to NFL commissioner Roger Goodell's efforts to crack down on dangerous head hits as an important step, one that has and will continue to influence amateur leagues to do the same. Cantu also credits athletes who take time to return from concussions, like hockey player Sidney Crosby and baseball player Justin Morneau, as setting an effective precedent for younger players.

"It's a work in progress, and it's not where it should be, but it's better," he says.

Currently, there is no reliable way to determine whether someone is suffering from CTE unless they have died and their brain can be analyzed. Nowinski says he hopes research at SLI will eventually lead to an effective test to detect and, ultimately, treat the condition.

"In the near future, though, I hope we can continue to install minimum standards in youth sports programs that will prevent the long-term effects of brain trauma," he said.

"I think what's being missed is the power that professional leagues have to make the youth game safer, which, in turn, will make the next generation of professional athletes safer."