Worried about my kitty's sudden twitching

My cat (about 9 years old) has been acting funny since yesterday. She's about a 90% indoor cat though she sometimes ventures outside to play in the front yard, doesn't usually go very far.

It started with her sitting on the edge of my desk swishing her tail really hard, to the point that it was whacking the wall. I noticed she had this concentrated, irritated kind of look on her face, and she kept jerking her head back like there was something back there that was bothering her. Finally she jumped down and left, but I noticed later in the day that she was still acting a little weird, backing up suddenly and bolting away.

Today it's been worse. Off and on her back has been rippling and twitching all over. When it happens she'll jerk her head back and lick at the spot roughly like it's bothering her, or she'll start aggressively grooming some other part of her body. Sometimes she'll start scratching behind her ear with her hind paw. When the twitching is getting really bad she'll stretch all the way out on her side and squirm like she's uncomfortable. Her tail is twitching and swishing a lot, too. Sometimes she flattens her ears back like she's angry and looks irritated, though her temperament isn't any different. She's still sweet and receptive to affection, and she's not being aggressive, although she lightly nips at me if I touch her on her lower back because it seems to make the twitching worse. I've also noticed her backing up and nearly tripping over herself like she's trying to get away from something. 

I don't think she has any symptoms of illness. She's not isolating herself or hiding. She's been sleeping a lot but that's typical for her. She's eating and drinking. No vomiting or diarrhea or any weirdness like that. I did try to brush her a bit and see if maybe she had something embedded in her fur that was bothering her, but I didn't find anything. I'm not sure about fleas. I don't have a flea comb so I can't check her for fleas right now, and her fur's really thick so I can't look under her coat myself. I did give her a good brushing when she was calm and it didn't seem to make any difference. 

Has anyone ever seen something like this? What can I do? Should I take her to the vet right away or wait and see if it gets better? 

Hi

Have you used any flea products on your cat?

Quiet said:

 
Hi

Have you used any flea products on your cat?

Click to expand...

Nope.

Is she long hair or short hair. If you haven't used any flea products on her have you used any sort of bug killer anywhere in or out of the house such as ant killer or raid or anything? The twitching can sometimes be a reaction to the pesticide pyrethrin or permathin or a pyrethrin based product.

It can also mean severe itching which is what I would suspect it is. That can be caused by fleas, or mites, or allergy. But I think with this acute an onset it is probably fleas or mites.

I would take her to the vet in the morning if I were you.

If you can't do that try putting a white towel under where she sleeps and see if you find anything that looks like pepper on the towel in the morning.

Don't use any store bought flea products such as hartz and don't use any flea collars. Over the counter flea products can kill your cat. If you go through your vet they should be able to get you something that will work.  

The more I think about it the more I think you should take her to the vet. It could be a sort of toxicity to something .

Some of the symptoms sound like FHS, though it usually doesn't come on suddenly.
There are several videos on line; her is one (described as 'mild'). Ritz has FHS which is, I believe, caused in her case by an adverse reaction to vaccinations.
It could also be microscopic mites or bites.
I agree: I believe any change in behavior is a possible vet visit or call to the vet. Do let us know what the vet says.