Meant to add in my earlier post but COTH was being squirrelly with adding an edit. I also went down a rabbit hole looking for physical causes too. Horse did have a previous history of mild Epm that was caught early and treated. I had two different vets do full work ups and help trouble shoot how to deal with this issue. It was almost like my horse had PTSD. You could see him almost manifest the scramble before it happened. Like learned helplessness he would just feel a turn coming and start to prepare to go down. Both vets ruled out any physical issues. So I tried a million different things to make the trailer work. Name it I tried it. Tried different trailers. At my wits end I called Rissa at BR and spoke to her for hours. I decided to do a Hail Mary and try rear facing. Believe me when I say I wrestled with this issue and how to solve it for 4 months. Every professional. Every possibility.
The rear facing trailer was and continues to be a Godsend for my horse. We’ve had it for over 2 years now. That and my trailer camera are the best investments I’ve ever made.
P S. If you’re anywhere near central Florida. LMK. I’d be happy to let you use my trailer to see if it would might be a solution. If you wade through the other possibilities and don’t find a solution, perhaps this might be helpful.
Ahh yes I remember your posts too ThreeWishes! They are part of the reason I believe backwards could be the solution for my horse too.
I also tried shavings vs not (and different types of shavings), different mats, driver vs passenger side, Soft Ride boots, different tow vehicles, different trailers, divider vs not, sway bars + WDH vs not, etc. Nothing made any notable difference. She would scramble any time we made any sort of turn (left or right) at any speed, even under 5 mph. She also had a history of EPM, years before the scrambling, so we retreated and it made no difference. Maybe some day, I’ll be able to afford a balanced ride or EquiTrek but with her being mostly retired anyway it’s not a priority. I do hope you sort your pony out OP and sympathize with how stressful and worrying this can be.
Our stories are like mirror images!!! I too wish the OP and her horse the very best.
Video shows exactly what my gelding started doing as a teenager, scrambling in trailer. Did it on straightaways, not just turning, if it went over any bumpiness. Turned out to be arthritis in the neck. Had a couple corticosteroid injections done between I think four vertebrae, and for the rest of his life he had to be hauled in a wider space. He could manage in the last open slant of a slant load; a box stall was best. Couldn’t balance without being able to spread his legs.
You said the scar went to her ribs behind her left shoulder, but where did it start?
I’d have the neck x-rayed, if it were me, based on my previous experience.
A friend’s horse scrambles like this. She didn’t when I first met her, but she became very unstable and wanted to lean on the center partition if loaded on the passenger side. I don’t haul her any more but she was much more comfortable loaded on the driver’s side. I think she wanted something to lean on. Horse had never been in a trailering accident.
Interestingly, one of mine fell in the trailer coming home from a hunt. Straight road, 25 miles per hour. I heard scrambling in the back and then it stopped. When I got back to the barn 10 minutes later, he was on the passenger side of the trailer, having gone completely under the divider. His halter was hanging empty from the tie. He was a big horse so I’ve never figured out how it happened and how he was unscathed. My guess is that he peed in the trailer and that the floor was slippery/frozen. He was pretty shaken up when he got off, but loaded just fine for the rest of his years (much to my surprise/relief).
Very peculiar and reminds me of an orphan foal that was completely grief stricken after his mom died and no suitable nurse mare or companion was coming. He couldn’t fight or flight his way out of the situation and he would lean and tremble like this on the wall.
The few scramblers I have known have hauled best in a slant or loose in a box. My guess is it is easier to balance on an angle - which tracks with how my own horses much prefer to haul in a (big) slant vs my straight load. Neither of mine scramble, but they load and ride MUCH better in a slant.
Which stinks because on paper my trailer is perfect - 7’4" wide, 7’9" tall, super airy and bright inside, no mangers, etc. Every dang horse loads and travels better when I tie the divider over or we haul in a friend’s slant. I don’t think it’s my trailer specifically as we have the same results with other (large) straight BPs. No issues on big H2Hs when riding backwards.
Anyway, just anecdotally it seems that a properly sized slant or reverse haul may be easier to balance for a lot of horses.
Most ranch horses spend long time in stock trailers every day, jump in and being hauled here and there, backing out, checking cattle and coming back jumping in.
Most are never tied, they stand at a slant front to the left and over the axle/s, is how they prefer to ride when given a choice, like these, that are not tied in.
By the way, one axle stock trailers get around muddy and rough country better, but are harder riding for the horses, they can get sore from trying to balance so much.
Unless you are in very rough country, two axle trailers are better for the horses:
I think sometimes people underestimate how physically demanding it is to remain upright in a moving trailer. If you aren’t already make sure you are taking those turns at a 1st gear speed and go wide and slow. Whatever the speed limit is you want to be going under it, especially on highway ramps or left hand turns.
With many neuro horses I’ve known some of the first symptoms have come about in the trailer - general trailering issues or anxiety, etc.
Most horses will want to ride facing rear, at a slight angle - it’s easiest to balance and less torque on their limbs. With your horse, it could be the turns are placing too much torque and pressure on her bad side. Could be a combination of things, don’t rule out the wither or neck arthritis as nonconsequential; in general I see these things are culminative.
Horses with neck issues really seem to need their neck (free) to balance. I hope you can get to the bottom of it, that was a strange video to watch.
The way the horse stands when you first open up the trailer will tell you what they thought of their ride. A wide legged stance with hind legs under divider, or anxious/nervous, can tell you they had a hard time.
I don’t want to be a complete alarmist, but…
(long story ahead)
I had a horse (well, my screen name, dam of my avatar) who I bred, raised and competed. The very first time I took her for a ‘big-girl ride’ was when she was 6 so I could ride at a 7-day eventing training camp in the interior of BC (IYKYK) several hours trailering and a ferry ride away from home. I had an old 2-horse straight haul that moved over with me from Ontario 10 years before. I was 10 minutes from the ferry terminal and 40 minutes from home when my mare went down 
. I was able to get her up on her own accord, moved the 1/2 wall over, looked her over and she was fine- not a hair out of place, nor did she seem stressed, so I continued on my way. She hauled beautifully all the rest of the way without a peep or anything, and never put a foot wrong in that trailer ever again, with or without a trailering buddy…
A few years later I bought an angle haul (3h), and she trailered well in that too, alone or with 1 or 2 others. Then I downsized and traded the 3 for a 2h angle haul. 1 time I had her in the front stall, and she went down, but only 1 time. Another time I was hauling with a friend in her 2h angle haul and Fanny had to go in front because she (at 16.2hh and 1200# was the smaller (!) horse. We were literally 20 seconds into the home trip - hadn’t even left the show ground- and she went down. We switched stalls and she rode in the back stall uneventfully home the rest of the way.
2 years later a scope showed many melanomas in and around her throat and up by her ears. I had to put her down 3 years later because of those head melanomas. (Edited to add: she had visible falling-down seizures in front of people out in her paddock)
The friend whose trailer she went down in was the 1st person to vocalise what I had been thinking since we found all those melanomas- she must have had them for a very long time and it caused some neurology affecting her balance.
Is there any way you can scope his trachea/esophagus to rule something like melanoma (since he’s not grey) out?
