This sounds like seizures
or Feline Hyperesthesia Syndromehttp://www.veterinarypartner.com/Content.plx?P=A&A=1998
I don't like your vet's attitude. I suggest you find another vet. Video tape some episodes to help in diagnosis.
How often is it happening?
I understand your fear, when Tolly's seizures (very similar to what you describe) started I was out of my mind with worry.He's been on phenobarbital for almost 8 years now. No episodes in over 5 years (took time to find the right dose)
His started when he was 3, he would run around frantically chasing an invisible bug, and was unable to stop or interrupt. He would bite himself, bite the floor shake his head.
Each cat presents differently, but you need a vet who is willing to explore all options and keep an open mind, not dismiss your concerns so quickly.
What's your boy's name? Welcome to the forum and please keep us updated.