Junior Seau shot himself in the chest in 2012 with a suicide note asking that his brain be donated to scientific research. As was suspected, they found a build up a tao protein associated with CTE, a degenerative brain disease caused by repeated concussions that eventually progresses to full blown dementia.
The biggest thing in this case is the NFL deliberately concealing information about the long term damage caused by concussions. If that is true then they've got a strong case.
There is alot of progress being made in understanding the longterm effects of concussions and it's alot more serious than has always been assumed. You hit your head, maybe you feel dizzy for an hour and then everything feels normal again. Your brain is still healing for a long time though and it's when you hit it again in that time that even more serious brain damage can happen. But still, patients who show no physical damage to the brain that can be picked up by CT's or MRI's can still have CTE.
People in skiing aren't the type to be put off by the chance of ending up in a wheelchair, or with a permanent limp, but the prospects of living with progressive dementia is something to be taken even more seriously.
"Chronic Traumatic Encephalopathy (CTE) is a progressive degenerative disease of the brain found in athletes (and others) with a history of repetitive brain trauma, including symptomatic concussions as well as asymptomatic subconcussive hits to the head...This trauma triggers progressive degeneration of the brain tissue, including the build-up of an abnormal protein called tau. These changes in the brain can begin months, years, or even decades after the last brain trauma or end of active athletic involvement. The brain degeneration is associated with memory loss, confusion, impaired judgment, impulse control problems, aggression, depression, and, eventually, progressive dementia."