I hopefully have good news for you -- at least our case of this type of injury is turning out well.
Two years ago we had an 8 yr old reining horse get run into at a show. He was hit on the point of his shoulder by another horse on a fast gallop. It knocked him down and from his reaction, we thought his neck or spine was broken. When he finally stood, he was non weight bearing on the front left. X-rasy showed no fractures, and severe radial nerve damage was diagnosed.
After 48 hours in ICU on heavy doses of DMSO and other anti-inflammatories, we were told to put him down. He was still very swollen from shoulder to wither, and still lethargic due to severe pain and totally non weight bearing, choosing to lay down 95% of the time. But, like most people with special horses (he was our daughter's show horse) we decided to look for alternatives. Long story short, poeple at the show came to our aid (he could not travel the 13 hour trip home) and he was taken to a nearby barn. He remained laying down 80% of the time and was totally non weight bearing for the next 60 days. They kept a support boot on his non-injured front leg to try to prevent founder, but I believe what saved him was his willingness to stay quiet and LAY DOWN the better part of the time, as well of course, as impeccible care (deep bedding, plenty of attention, good feed & water, etc).
After 30 days they began leading him around a little on 3 legs for mental well being and circulation, and at 60 days he began resting weight on the toe of the injured shoulder. By 90 days he was stable enough to transport home, and stand on the leg while we carefully had his feet trimmed (they were VERY long). After a total of 120 days he was hobbling around OK on all fours, and we turned him out on 120 acres pasture with a few buddies - his shoulder muscles were totally atrophied, yet he was apparantly sound to walk on the leg and could shuffle around the pasture in total happiness. There was no muscle tone around the joint at the point of the shoulder, so it looked like it would pop out from under the skin when he put weight on that foot. But all we wanted was for him to be retired in peace and tranquility, so in our mind it was the end of the story.
BUT - it has been two years - TWO long years - and the vacancy in front of the scapula is now totally filled in. The shoulder looked pretty much unchanged for around 20 months, but in the past 4 months rapid changes are evident. This horse runs and bucks and plays and when we made a longe line video to show all his friends and supporters, you could not tell he'd sustained an injury. If his progress continues, which we assume will be the case, we will bring him in and try riding him, with the goal of getting him fit to show again.
Important Keys to our success story:
Immediate anti-inlfammatories and pain meds
Support of the non-injured leg
This horse being a naturally good patient that LAID DOWN 80% of the time
TURN OUT time with no expectation
We had lots of folks wanting to give this horse a bunch of different treatments, and they are all greatly appreciated, but bottom line is I don't believe anything can make a nerve grow back faster. I am now of the opinion that if it grows back, it grows back. Nothing can hurry it along. I also have a new found appreciation for the common old-timer's advice of "turn 'em out and forget em", as hard as that is to do sometimes when you WANT so badly to help one recover.
This horse was a fat, fit show horse and was fed a premium diet while in immediate recovery, but then was a pasture horse with minimal care for 16 months following - he stayed of adequate weight, but did lose about 150 pounds of "show bloom". His feet were trimmed and he was vaccinated etc, but he got no extra care. Just time, rest, and room to move around with his pasture buddies.