Sick 2 year old with convulsions - any info please

[chickenwings]

My DS2 has just been sick and then his whole body jerked like a mini seizure. He is 2 and a half and has done this since he was a baby. He has had a brain scan and the doctors say it is not epilepsy or febrile convulsions but they don't really know why this happens. They think the shakes are benign and that he will grow out of them. This is the first one he has had for about a year so I thought I had seen the end of them but no such luck. Luckily they only seem to come on when he has a virus of some sort when his temperature is going up and down.
Has anyone had similar experiences or know anything more?

I think it would be difficult for them to say that just because his last siezure was not febrile convulsions that he will not have them.
TBH he is rather old for them now.
It sounds like it could be a myoclonic jerk, allthough this really is a guess. This is what happens when your just about to fall asleep and you suddenly jump, excepts that its happening whilst hes awake. It is normal and some people have them more than others.
Is this what it looks like or is it different?
The fact that it only happens whils he is unwell is a little strange...