Researchers at Boston University have found a degenerative disease in brain tissue donated by former NHL enforcer Bob Probert.

The Center for the Study of Traumatic Encephalopathy issued a statement Thursday saying that Probert had chronic traumatic encephalopathy (CTE) when he died last July of heart failure at age 45.

Probert, who lived in Windsor, Ont., played 16 seasons in the NHL for Detroit and Chicago between 1985-2002. His 3,300 penalty minutes make him fifth on the league's career list.

Probert, who struggled with drinking problems during his career, is the second hockey player from the Boston University program to be diagnosed with the disease after death. The other was Reggie Fleming, a 1960s enforcer who played before helmets became mandatory.

Details of Probert's brain tissue analysis won't be made public until they are reviewed by an academic medical journal, the centre said in its statement,  but the Probert family requested that the CTE diagnosis be made public to raise awareness of the danger of brain trauma in sports.

"This is what he wanted," Probert's widow, Dani Probert, told CBC Windsor's Early Shift radio program. "This is why he wanted to donate his brain, and I'm definitely proud of the fact that he's a part of this study, and to get more information."

Dr. Robert Cantu, co-director of the Boston University program, said it's difficult to determine exactly what caused the damage to Probert's brain tissue.

"How much is the hockey and how much is the fighting, we don't really know," Cantu told the New York Times for a story posted on its website Wednesday night. "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."

GMs to further discuss head contact

The Center for the Study of Traumatic Encephalopathy is a collaboration between Boston University Medical School and the Sports Legacy Institute that is attempting to address the "concussion crisis" in sports. The group has been at the forefront of research into head trauma in sports, and has received a $1 million US gift from the NFL, which it has pushed for better treatment of concussions.

The family of former Chicago Bears safety Dave Duerson agreed to donate his brain to the study after he committed suicide last month at age 50.

'The findings are interesting and certainly something we'll add to a much broader body of knowledge.' —Bill Daly, NHL deputy commissioner

"We are only beginning to appreciate the consequences of brain trauma in sports," said Chris Nowinski, one of the founders of the Sports Legacy Institute. "Early evidence indicated that the historical decision not to discourage contact to the head was an enormous mistake, and we hope aggressive change continue to be made to protect athletes, especially at the youth level."

Although the NHL has instituted a new rule making blindside lateral hits to the head illegal, and the league's general managers will discuss later this month whether further contact to the head should be banned, fighting has long been a major part of the pro game.

Nowinski said he'd advise the league to do more to stop hits to the head.

"I would love the NHL to take the tack that they need to protect their assets, they need to protect their best players," the Sports Legacy Institute founder told CBC News. "They need to eliminate hits to the head entirely so that we can watch great players playing great hockey."

There have been no signs that the NHL is interested in changing or eliminating that popular aspect of the sport.

"The findings are interesting and certainly something we'll add to a much broader body of knowledge," NHL deputy commissioner Bill Daly told The Associated Press in an email. "But we're not going to react or make changes based on findings related to one player, especially when it's impossible to identify or isolate one of many variables that may have factored into the conclusions reached, and when there is no real 'control group' to compare his results to.

"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."

Don Fehr, executive director of the NHL Players Association, was pleased that research was being done.

"Today's announcement regarding the CTE diagnosis of former NHLPA member Bob Probert is an important piece of research that the players, along with everyone else interested in the safety and well being of hockey players, should consider seriously, along with other relevant research and data," Fehr said in a statement. "We look forward to reviewing full results of the study once they are made available."

Fleming died in 2009 with dementia, after 30 years of worsening behavioural and cognitive difficulties.

Dani Probert said her husband showed a mental decline in his 40s, and displayed new and growing problems with short-term memory, attention and a short temper. Those are all symptoms consistent with those of other athletes with CTE.

During the last year of Probert's life, Dani Probert said her husband told her he thought he had three or four "significant concussions." But when talking about "getting his bell rung," which the institute says is a concussion by definition, Probert told his wife that his total jumped to "over a dozen."

"In my heart of hearts, I don't believe fighting is what did this to Bob," Dani Probert told the New York Times. "It was hockey — all the checking and hits, things like that."

Nowinski said last month more than 300 athletes, including 100 current and former NFL players, are on the Boston University centre's brain donation registry. There are 65 cases currently being studied. The program's "brain bank" currently has 68 specimens.

30 of 40 brains show CTE signs

Dr. Ann McKee, the co-director of the centre, which it says is the largest brain bank in the world, has analyzed the brains of 40 former athletes and found that more than 30 showed signs of CTE. That includes 13 of 14 former NFL players, college and high school football players, hockey players, pro wrestlers and boxers.

CTE, originally referred to as "dementia pugilistica" because it was thought to only affect boxers, is a progressive brain disease believed to be caused by repetitive trauma to the brain, including concussions or subconcussive blows.

It also is believed that other undetermined factors, such as genetic predisposition, put some people at greater risk of developing the disease.

Keith Primeau, a former hockey all-star who was forced to retire in 2006 because of concussions during a 15-season NHL career, is among those who have decided to donate their brains.

Primeau and Probert were Red Wings teammates for four seasons.

"Hockey continues to make positive steps to protect players from concussion and brain trauma," he said. "I hope the findings from the study of my friend, Bob Probert, will accelerate that momentum throughout all levels of the game."

With files from CBCSports.ca