Well, I've had the same thing here about two weeks ago. A mare with a foal at her side didn't look right when I went out to feed so I haltered her to bring her up to the house where I could see her in the light. She tripped over me the whole way. Got her to the backyard and she was stumbling, crossing her legs over each other and she went down a couple of times. Called the vet, not available so had to use a back-up (a group I'd not used before and won't again - but that's a whole different thread!). The mare never did have a fever, was hydrated, ate, drank, pooped, peed, etc. Her heart rate was between 44 and 54 all the times checked. She had a fort dodge 5 way in May and is up to date on worming.
Vet did CBC, fibrogen (sp?), triglycerides and EPM. All negative. ALL. I treated her as if it was an injury to her spine/head/etc. She got banamine for 4 days, and got 2 treatments of IV DMSO (helps with inflamation if there is any around the spinal cord). It's been two weeks and she's still living in my back yard and if it weren't for the fact that her tail head is so loose it's like it's not attached, I wouldn't know anything had been wrong with her. Personally, in my case, I'm going with the neurological (due to injury), but I will probably never know. And maybe the muscles that make the tail work will recover as it appears other muscles have, but maybe not. Her tail is looser than any mare about to foal I've ever felt. Which means I must keep fly spray on her at all times because the flies have figured out her tail only swishes a little.
It was very scary. To see a horse stumbling around just like they are drunk - falling down, tripping over themselves - it's horrible to watch and it's a very helpless feeling. She's only a 29" mare, but when she's trip, there was nothing I could do to stop her from going down. Believe me, I learned the hard way and have the bruises to prove it.
PS: we also discussed nutrional deficiency, like calcium since she's got a baby at her side, but nothing showed in the tests and after the vet looked at my pasture, hay and went through my feed plan, we didn't think that was it. Guess anything is possible, but nutrition seemed unlikely in this case.
Sorry, one more thought. I never got to discuss this with the vet because it didn't really hit me until after about the 3rd day, but when I would go to give her a treat and she would turn her head to sniff it, her head would shake in quick, short movements as she took the treat. Kind of like a seizure, but just in the head area. She stopped doing that at about day 7 and doesn't shake her head or twitch her ears unusually at all.
I hope you get some answers, but be prepared to never really know. Hopefully he will recover fully and quickly.
