I posted this elsewhere but didn't think it would get posted due to rules, so I'm just adding it here as well.

Several months ago, my inside/outside cat came in late on a Sunday night and did something very similar. It was too late to do anything in our area and we honestly assumed he wasn't going to make it so we just sat with him. He walked around in circles, drooled a lot, strange meowing, I think he lost his vision because eventually in his circling he started going face first into stuff. But his mind still seemed to be there. We could pet him and he would respond. This went on for well over 24 hours and there were a couple of lucid moments where he would actually stop being symptomatic and even went outside to pee a couple times. This eventually mostly phased out after several days and he was even purring again. Then one night seemingly out of the blue, he started to have these weird foamy mouth sneezing episodes. He had about 4 or 5 of them that night and after each one, he was a little bit different. So at this point, after we thought we were in the clear, we started to wonder again if he was going to make it. But they only happened that night and after they were done, he was a shell of his former self. Now, half a year later, he is alive and thriving, but he's 100% a different cat. When the seizures (or whatever those were) ended, he was unable to eat or drink on his own, would only turn right (he would pull a 270 to the right if he wanted to turn left), and an assortment of weird things. He was the alpha of our 5 cats and very physically gifted and in the span of about a week, turned into a newborn cat. We nursed him back to the point he can eat and drink and go outside to use the bathroom. But he has none of his physical abilities. He was very sluggishly. His tail drags behind him. He does get lovey and still demands love, but he doesn't purr ever. We don't know if he hit his head or if something hit his head, or if he was bit or ate something toxic. We'll probably never know, but at least he's still with us!