Backstrom claimed he had a migraine after the Bourque hit. I don't think I trust his medical judgment any more than I do the Russian team doctors'.
Apparently hits can actually trigger migraines in players who are predisposed to them. I remember that being discussed after the Bourque hit on Backstrom and also in an interview with the Penguins' Kris Letang, another player who has occasional migranes (and a concussion last year).
The similarity between migrane and concussion symptoms can make it difficult to diagnose concussions in players like Backstrom and Letang. The player just assumes that he has a migraine triggered by the hit and tries, as usual, to play through it.