Stiff gait, spasms

Hey- I have a six year old female spayed cat- Ivy who started displaying odd symptoms three weeks ago.
ivy has a history of feline hyperesthesia.
So three weeks ago i gave her Advantage II flea medicine (same ive always used and the correct large cat dose). I dont flea her often bc shes an inside cat so this was the first dose in at least six months. I only gave her some bc i had a routine vet appt the following week and didnt want her to pick anything up.
Two days later she started walking stiff and hunched in rear. Took her to vet, xray and bloodwork normal. Two days later it progressed to her appearing to limp on rear leg- took her to two different vets that day n they thought ligament/muscle issue-given pain med and prednisalone.
Next week on monday progresses again- walking 'peg legged' on all her legs- now appearing to favor a front leg. In the meantime she is only getting up to pee/poop and is obv disgruntled each time she has to move. Sleeps most comfortably on her back with all legs or back legs up in air. Legs appear to tremble or spasm at times.
I took her to Cornell and the were 'baffled' too. Said it would cost $2500-3500 to run trests that 'may not show anything'. They said they heard an irregular heart rate, gallop, that may put her at risk for anesthesia to test.
She now is walking better but still very stiff and spends nearly all her time laying down. Her appetite through this has been ok- ive been making chicken broth, hamburg, baby feed and her reg crunchy food (royal canin GI formula).
Any ideas?

walker2882 said:

Hey- I have a six year old female spayed cat- Ivy who started displaying odd symptoms three weeks ago.
ivy has a history of feline hyperesthesia.
So three weeks ago i gave her Advantage II flea medicine (same ive always used and the correct large cat dose). I dont flea her often bc shes an inside cat so this was the first dose in at least six months. I only gave her some bc i had a routine vet appt the following week and didnt want her to pick anything up.
Two days later she started walking stiff and hunched in rear. Took her to vet, xray and bloodwork normal. Two days later it progressed to her appearing to limp on rear leg- took her to two different vets that day n they thought ligament/muscle issue-given pain med and prednisalone.
Next week on monday progresses again- walking 'peg legged' on all her legs- now appearing to favor a front leg. In the meantime she is only getting up to pee/poop and is obv disgruntled each time she has to move. Sleeps most comfortably on her back with all legs or back legs up in air. Legs appear to tremble or spasm at times.
I took her to Cornell and the were 'baffled' too. Said it would cost $2500-3500 to run trests that 'may not show anything'. They said they heard an irregular heart rate, gallop, that may put her at risk for anesthesia to test.
She now is walking better but still very stiff and spends nearly all her time laying down. Her appetite through this has been ok- ive been making chicken broth, hamburg, baby feed and her reg crunchy food (royal canin GI formula).
Any ideas?

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Wow this is awful and mysterious.  I presume no indication of blood clots?  Was a neurological exam done?  I have to admit i'm clueless and if all these vets are too, then i am very worried for your cat.

I've never heard of that kind of reaction to Advantage II, although there have been reactions to Advantage Multi (neurological reactions to the moxidectin in it).  The only time I've seen these symptoms was in cats or kittens who had the form of calici that goes into the joints rather than becoming a respiratory infection.   We call it "limping kitten syndrome" and the best way to treat it is exactly what she got, pain medication and prednisolone.  Those limping kitten episodes usually pass within a few days, or a week at most.  It does migrate the same way, sometimes first in one front leg, then the other, then the hind legs so they don't want to move.  I had one that I had to keep on an incontinence pad because she would not or could not walk for a day or two.  I've only seen it in one adult, though.  It was sad but he did get over it fairly fast.  In your case, it may be best to just get her a little more anti-inflammatory steroids -- you might want to go with depo-medrol, which lasts a whole month, and just wait and see if her body fights off whatever this inflammatory arthritis is.  It sounds like she is getting over it on her own slowly in any case.  The steroids would just make her feel better faster.   Do let us know how this turns out.

Some kind of auto-immune joint condition is a possibility but I'm not sure it can explain the spasms or the strange sleeping posture. I can think of several possible explanations all of the neurological in nature. I'm sure the vets have considered them and I believe making a diagnosis would require an MRI/brain scan. Probably both expensive and not viable due to the need for anesthesia. The Advantage treatment may not have been the cause even though the chronological proximity seems suspicious. It could have been a trigger, making something bigger take its course on that date (though it would have happened sooner or later), it could have been the cause, or could be totally unrelated. 

You say that she's doing better, which is excellent news. With any luck, her body will fight this off and she will re-gain her good health again. Good luck and keep us updated!

So far so good guys, thank you for your ideas! I was worried about a possible clot but all the vets said this seemed unlikely bc all her paw pads were pink/warm and ive been checking them daily since.
She has been moving around more the last few days- certainly not her normal but definitely increased activity.
Ive just been saying many prayers, giving her lots of love/positivity and homemade meals.
She was/is occasionally sleeping in her litter box which she never did- I always fear the worst so this really had me worried but she has not done this in the last few days so im hoping it was just a comfort thing after traveling to all the vet visits.
This thursday marks week three- but im hopeful. Has anyone heard of feline hyperesthesia progressing? I feel like the advantage could have aggravated nerves enough to cause exacerbation of hyperesthesia but so little is known about hyperesthesia- i may never know.
Say prayers for Ivy [emoji]10084[/emoji]️