I’m adding this video link so that others may benefit from viewing it.
Vestibular Syndrome in cats effects their ability to code/encode signals to and from the brain. This could also result from cancer, infection, or brain disease or whatever else it might be.
We noticed Precious (shown in video) making a circuling motion a few days after she began falling down.
Here are a few links on Vestibular Syndrome and other syndromes:
Another Vestibular Disease information page from Canada West Veterinary Specialists & Critical Care Hospital
Description of Feline Nonsuppurative Meningoencephalomyetitis (“Staggering Disease”)
Toxoplasmosis in Cats from Cornell University
Another site on Toxoplasmosis from Cat-World
Precious's Weblog 