What do you think is wrong with my parents dog?

I think my parents dog is having strokes. He will suddenly convulsively tilt his head to one side and the eye on that side will partially close. His body will also bend that way like a bow. He also has balance issues and starts walking sideways. Then he gets up again and is *fine* 5 seconds later. And I mean totally fine, complete with running and jumping and acting completely normal. This has been going on for a few years with maybe one episode a year, but in the last few days it has been happening 10-20 times a day. The vet did give them Diazepam 2mg and told them to give them half a tablet to stop the 'seizures' it's not really doing anything and I don't think that is the problem. My parents won't follow up or get him actually checked out. Any one have any ideas?