Poor little guy, hopefully he'll regain at least partial use.
I have a horse that, as a yearling, slipped in some mud, rolled, and struck her shoulder. The muscle atrophied, the shoulder was flat as a pancake within a week, and the radial nerve was gone. After three months of daily massaging and flexing she could lift it and use it rather effectively while she grazed and ran. I called around and found that one of the best things I could due for her, to help stimulate the nerve and muscle, was electro-acupuncture. She had two sessions and was very sore afterward, but after a week of recovery she gained more muscle tone and furthered her limited range of motion. The hoof is still a bit funky, grows more like a donkies than a horses due to the other legs adaptations, but a year later and she can run like the dickens, rear up, and act like a total brat without anyone knowing that she's a bit disabled; she'll never be a riding horse, but she is very happy tearing up her pasture.
Perhaps acupuncture, or electro-acupuncture may be able to help your boy as well? I know it's difficult enough finding an avian vet much less a vet who practices acupuncture, but thought it may be worth mentioning. Good luck with your boy, nerves are a difficult thing to heal/regrow but his chances for recovery are higtened by his youth.
Links:
American Academy of Veterinary Acupuncture | To improve animal health care by the advancement of veterinary acupuncture and Traditional Oriental Veterinary Medicine through education, research and leadership ,
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