Scott Parker lies in bed, dreading what might come next. Soon after awakening, his ears ring so loud they seem like the equivalent of a hundred fire alarms. Waves of nausea wash over him until he vomits. His eyes glaze over.

One of the toughest men to ever play in the NHL is knocked out, not from an opponent's punch, but from simply getting out of bed.

Nearly six years since he retired from the NHL as one of its toughest enforcers, Parker is finding everyday life a more fearsome opponent than any he dropped the gloves against. Some days he feels fine. Many days he finds himself paying the price of years of blows to his head. The 6-foot-6, 245-pound Parker — nicknamed "The Sheriff" as a player — frequently is debilitated by seizures. He has to wear sunglasses most of the time because too much light can bring on headaches that leave him incapacitated. When Parker looks down, he cannot "track" objects. Otherwise, he gets dizzy and nauseous.

He is only 35, but Parker's short-term memory resembles someone much older. He is so forgetful that he has to write down routine things such as needing to make a trip to the grocery store. He often takes pictures and videos with his phone to remember how to do things such as use tools in his woodworking and metal shop.

"I can see right away when he's having a bad day," said Francesca, his wife of 15 years. "When he wakes up, he's in a fog. I can talk to him and I can see it's just going right through him. And then he's forgetful. He has words in his head, but what comes out of his mouth is totally different than what he's thinking."

Parker's symptoms closely resemble those of a growing number of former NHL fighters, as well as athletes in other sports, who suffer from repeated head trauma, an issue both doctors and the governing bodies of pro sports are attempting to address.