Sudden onset neuro issues UPDATE #15

Got a new OTTB in a couple of months ago, he has mainly been on turnout with my older gelding. Went to get them today, brought them up from the field, put them in their stalls. He was acting completely normal during this time. Took his halter off and he ate about half his breakfast. I walked down the aisle and within 10 min suddenly heard a flailing horse. Rushed over and it was as if he had lost use of his back legs. Started thrashing about his stall, taking down his water bucket and getting cuts over both eyes. Finally he laid down and stayed there til the vet came. He was in a choke episode by this time. He got to his feet easily, vet cleared the choke but thought he was colicking due to high heart rate and breathing as well as decreased gut sounds on one side. He was unsteady on his feet but not horribly so. Brought him to clinic, he became very unsteady, muscles twitching, nystagmus, trouble chewing. He is there for the night. Several ideas have been tossed around but it is still not clear what is going on. Bloodwork normal, lungs and gut okay. Anybody experience neuro issues with this violent onset? He has tripped a few times in the field over the last couple of months but I attributed that to big horse/wet ground/weak hind end.

Could he be appendix, and it’s hypp?

No, full blooded TB.

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Very strange about the sudden onset, my first thought is whether he did something in the pasture. Though it doesnt sound like you saw any physical signs of injury…
There are a number of things like EPM and EDM that can present with neuro symptoms and are the most common. There is another rare disease, polyneuritis equi, which has an immune system cause beyond my ability to explain. It causes damage to the nerves in the cranial area and the hind end.
Its a complicated story but I imported a horse who was ultimately diagnosed with this; eye issues on one side, trouble chewing and clear hind end ataxia. Though he declined rather quickly, it was about 3 weeks or so, and there was not a sudden event that I’m aware of. But your explanation of symptoms is very similar to what went on with my horse. He was treated at Univ of Florida in Gainesville July of 2020 in case your vets need to reach out to them. They have well respected neuro group.

Thanks, Yea no obvious sign of injury. And he has been pretty calmHe had a decent racing career and was injured but completely healed. About 2 weeks ago he fell in the pasture being goofy and was 3 legged lame on that (rear) leg for several hours. Now I am wondering if that was actually a neuro episode itself. I am wondering about cervical arthritis too. Sorry about your guy; what a nightmare!

THO? Does he have facial nerve paralysis?

THO has been brought up. Not full paralysis but difficulty chewing. No lip or ear droop or anything like that.

Jeepers! When he fell, did he twist his spine…as in fell behind but not all the way down? Maybe pinched something? I’m so sorry.

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that is kind of what happened…back end went first. He did have a little heat and swelling in the bad leg after so I never gave it much thought that anything else was hurt other than that area. He has been grazing and moving around okay and acting like a dweeb since then, not as active, but everything has been moving okay as far as I can tell.

I have seen vets give IV DMSO to help w inflammation in the spinal column due to pressure from high parasitic die off during EPM treatment. I wonder if something like that would help him if he injured something in the fall. Your vets probably already thought of that, but it might be worth asking.

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thanks! Yes they did say they would give DMSO yesterday along with NSAID, steroid, antibiotics. Talked to vet this morning, he is more stable but of course he is on a bunch of drugs. Still has nystagmus which is troubling to me. They are doing x-rays and scoping today. She wants to test for EPM if those tests are negative. I’ve got to figure out where to draw the line…as neuro as he is, even with treatment, I know they only come back so far if it is EPM.

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So sorry about your horse. Forgive me if I missed it but are they looking at West Nile?

Thanks! Yes they are but the blood work takes a week to come back.

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Good luck OP. That sounds terrible. I hope they are able to diagnose and treat soon.

Nothing nearly as violent, but did deal with sudden onset of neuro symptoms. Horse was fine, then suddenly unable to balance on 3 legs for picking out feet, obvious hind end ataxia and when trotting, looked like her whole right hip was falling out from under her. Did minimal dx due to her age, as I was ok with retiring her if she could be paddock sound. The big concern was being able to trim her feet.

A month of Previcoxx and she came I reckon 95% good, and has been back in work for over a year. Still slightly ataxic, and if she’s having a bad day we don’t do anything. I think we got lucky and fully expect the issues may resurface. Fingers crossed for a positive outcome for your boy!

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So horse has been in clinic for a week now. He has facial paralysis on one side. Nystagmus has stopped, he is walking a little better but he developed corneal ulcer from not blinking enough. He also had low fever today for first time.
The two thoughts are that he has THO (paralysis is on side where enlarged hyoid bone is) or EPM. Blood test shows antibodies but not extremely high. Tried to do a spinal tap today and couldn’t extract fluid. They can try tomorrow or I can just begin Marquis treatment. He has been on rebalance for a few days now. Definite test for THO would be MRI or CT scan. I want to bring him home tomorrow, believe he is stable enough but not sure where to focus treatment on.


FWIW, if this were my horse, I would get a second opinion from a neuro doc at one of the teaching hospitals. The fact that your doctor is still so hung up on EPM is baffling to me. The horse has all the symptoms of THO. You could probably get the CT done for around the cost of a round of Marquis.

They’ve probably gone over this with you, but the horse is at risk for continuing to develop corneal ulcers, as well as choking again, and/or developing aspiration pneumonia.


TBH, if you’re going to go the EPM treatment route, I would put him on compounded diclazuril + levamisole, at a dose your vet determines. Diclazurl is the active drug in Protazil, and levamisole is a good immune booster and anti-inflammatory.

This combo has worked a lot better, with fewer relapses, for a lot of horses, over Marquis. The reason is that diclazuril kills rather than inhibits the protozoa. The idea of inhibiting is to allow the body to do its job of killing, but that’s not a given.

Levamisole might also be useful for any THO issue, for the reasons I listed.

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Is he now able to blink? As noted above, treating the ulcer and having them not recur will be a challenge if he’s not blinkng properly. I would also wonder what caused the fever. Also, though my horse in above post had a different diagnosis (ultimately confirmed by necropsy) it is worth noting that his hind end neuro symptoms showed some improvement while on steroids, they got worse again when steroids were reduced/removed.
Dont know if THO can cause hind end neuro issues, so that would be one question for the vets. It sounds like they think something else is causing that problem. Its hard to say where to begin as an outsider, but if you take him home, I would get a very detailed set of instructions for care. And I would be very careful/observant of his neuro issues (both head and hind end) to the point of keeping a log of what you are seeing. Sorry you are going through this…


I appreciate everyone’s input! I did take him home. Temp was normal…weather has been brutally hot here and wondering if he was just not sweating enough? I actually was contemplating euthanizing today but when I got there he was actually having a better day. The hind end ataxia was actually much improved today and he was able to chew better. The eyes are the biggest issue; he still can’t blink and I am having a very hard time treating them. They had talked about stitching them up but they didn’t think they could get him quiet enough for that without full sedation.
I don’t think vet is denying the THO…She did suggest an MRI yesterday along with the spinal tap.I told her from the start he is not a surgical candidate and there was no sign of guttural pouch infection so THO would most likely be caused by stress fracture. I just don’t know what point an MRI or CT scan would be…would I just put him down if they found it?
My own vet will be coming out in a day or so to see him and I can talk to her further about it. I only got one tube of marquis and board is paid for so really not investing that much money. Other than the eye, he seems to be doing okay, all things considered. I just wanted to buy him a little more time.
I’ll have to ask about the diclazuril + levamisole, not sure if it is an option at this clinic as it seems they stick with brand name drugs when possible