One of my cats has always been twitchy, but I started to realize it's specific to her back, and if petted there would act almost like it was ticklish, or hurt, and would make complaining noises even though there appeared to be no reason for it. Now I realize that it *does* feel strange, and possibly painful to her, and spent some time figuring out that scruffing her neck and shoulders like you would a dog and scratching the top of her head is feels good but any touching at all on her entire back, and, I think, her tail, feels bad. The site I linked to does not seem to suggest it's a progressive disorder but others do. I'd never heard of this before tonight.
Curious George: Feline Hyperesthesia Syndrome... I'm wondering if anyone has had any experience with this.