Even without the sickness I think it's harder to diagnose concussion with Letang than it is usually with players (not that's it's ever easy). Letang is prone to migranes and the symptons are basically the same as to concussion. Here's an article from his rookie year:
Most days, Penguins defenseman Kris Letang feels healthy and happy and normal.
Then there are those days, a handful of times a year, when he has to stop what he is doing, lie down in a dark room and try to sleep through the vision loss in his left eye, intense nausea and a severe headache.
Letang knows when he starts having impaired vision that he is at the onset of a migraine, but it is unnerving each time.
It happened Thursday about an hour before the game at Ottawa.
"He said he felt the symptoms. He knows when they're coming," Penguins trainer Chris Stewart recalled yesterday.
The vision problems and nausea that caused him to be violently ill subsided enough over about 20 minutes for Letang to join the pregame warmup. Despite recurring symptoms, he played 18 minutes, 18 seconds, getting an assist in the third period of a 6-5 shootout win against the Senators.
"It was kind of a big one," said Letang, 20, who has had migraines since he was about 12. "During the game, it came back because the lights were too bright for me."