Unfortunately, my cat has been showing the same symptoms for the last two weeks. He's only about 10 months old.
We have two indoor cats of the same age (came from the same litter). The cats have never been outside from birth. They have all their shots, etc. and are very well maintained.
One has always been a bit clumsy -- missing jumps, sometimes misstepping, etc.. Two weeks ago he started walking slowly. He'd go 2-3 steps and then stop. He wouldn't jump onto things.
The next day he was declined through the day. By the end of the day he could hardly walk. He fell when he walked. He walked with his rear elevated and his front legs trembled. He sat for extended periods of time in his litter.
We took him on an emergency trip to the vet the next day. The vet has actually been terrific and has done several examinations, rounds of testing, calling the local university vet school, etc..
The blood work came back with everything within normal range. The only thing near the edge of a normal range was his white blood cell count, which was on the high side of normal. The vet suspects this is a result of trauma.
Like the original poster said, the x-rays came back negative. There were no signs of breaks or anything abnormal.
There are no signs of FIP and no real chance that he could have been poisoned (plus he's never vomited the entire time we've had him). He's never been outside so it'd be hard to contract anything related to a flea or tick.
For the first few days, the cat was on a pain killer and we had him isolated. He actually improved drastically on his own and returned to about 85% of his ability to walk and run on a flat surface. He still couldn't really jump and was slow on the stairs, but he was much improved though his front legs still had tremors. We felt that he could have had a happy life if he just plateaued at this state.
Yesterday he took a turn for the worse. He was again walking slowly and started to look as if he was in pain. He spent most of the day in his bed. He didn't want his back touched. By the end of the evening, he was walking weirdly and was falling again.
We called the vet again first thing this morning. Our cat is still a medical mystery. We're being referred to the neurology department at the local university.
If anyone has had a similar experience and actually found a positive resolution, please let me know. It's tearing us up to watch him in this state.
Thanks in advance!