The same thing happened to my iguana, but the vet told me to wait for one month. I was told that normally speaking, if it's going to happen, it will be in the first couple of weeks, but it's not uncommon for them to regain their movement after several weeks.
Unfortunately, my iguana wasn't one of the lucky ones. After about 2nd week he lost the use of one of his arms as well, and I found him one day flipped up-side-down in his water bowl. Poor little guy couldn't flip himself back over, and that's when I knew it was time to let him go
I hope you have better luck with your cat.