It is virtually impossible to describe what ds does. He bares his teeth like this and makes a sort of noise like a cross between a grunt and that noise tennis players make as they hit the ball. At the same time he slightly bobs his head to the side and tenses his hands (if his hand happened to be against your skin, you'd get a nasty pinch). He does it often enough that everytime we've talked about it you only have to wait a short while before he does it again.
We've booked a gp appointment, because hv not available when we are, and we have it on film (by chance) just in case it doesn't happen while we're in the surgery.
Has anyone else ever heard of such a thing? Do you think it is worth worrying about?