During the game we stopped and rewatched the hit several times - along with the several times that the broadcast replayed it as well.
He never hits his head on anything. And it doesn't really ever look like his head/neck whips enough for whiplash to explain it. One person was saying that the tackler hit him on the chin, and maybe that was it - but I don't know, the chin hit was pretty weak too.
I'd be hesitant to clear him for play without knowing what caused the problem to begin with. But I'm also not one of the conspiracy theorists who believes the only reason he was cleared is because the Chiefs want him to play and he wants to play too.
I also recognize my own bias - as a BYU fan, I always like the BYU guys to do well - so I'll be supporting Brother Reid and Brother Sorenson Sunday.