If the case goes to court, the plaintiffs’ lawyers will have to prove two main things: That brain trauma suffered in the NHL specifically caused the problems that former players are experiencing, and that the NHL knew the risks and didn’t do enough to inform and protect the players.

This could be the NHL’s defense: Doctors are still learning about the short- and long-term effects of brain trauma. How could the league conceal the risks for years when it still doesn’t know them definitively now? How could the league have dragged its feet when it has been out front on the issue relative to other pro sports leagues? And if the risks were so obvious, why don’t the players bear responsibility for themselves, especially when they have had influence through their union?

The suit states as fact that “both repeated concussions and sub-concussions cause permanent brain damage.” It cites studies conducted as long ago as the 1920s. But even the most current research, including the landmark work at Boston University on chronic traumatic encephalopathy, is preliminary. BU has done a series of case studies with biased samples; it has not done incidence-of-prevalence studies. BU agrees that the risk factor and rate of progression of CTE have not been established. NHL and NHLPA doctors agree CTE exists, but like others, they say there are many unanswered questions.

“They keep going to the cause-and-effect relationship which hasn’t been supported at this point in time,” said Ruben Echemendia, the NHL’s neuropsychological consultant, in 2011. “It may be in the future, but at this point, it’s not. We don’t know what causes CTE. Nobody knows what causes CTE at this point in time.”

“If you look at all the people who have cognitive problems late in life and have dementia, have Alzheimer's, there's not an epidemic of ex-athletes in that population,” said Jeffrey Kutcher, a leading sports neurologist and an NHLPA consultant, in 2011. “There's a suggestion here and there that some populations of athletes have a higher risk of things like Alzheimer's, but it's not obvious and it's not a dramatic thing. So somewhere in there lies the truth, and to get to that truth, you need to do research – hard, complicated, long research.”

Cotsonika continues, and his article's more than worth your time.