cat's head is jerking/twitching

My cat's head started to jerk at the end of last week.  We took her to the vet and they did a blood panel and everything came back normal.  They are not sure what the problem is, but they think it could be focal seizures.  They prescribed her an anti-convulsion medicine and it seems to have no effect.  She has been taking it for 3 days now.  She is eating, drinking, and playing normal, but I do not think that she is sleeping very well.

Did you ever find out the cause? Treatment?

We sent her to a neurologist and ran her through a bunch of tests. She got an mri and a spinal tap. Turns out it was just a chronic nasal infection. She is on antibiotics for the rest of her life (every 3 days) she seems to be doing fine now.