Special needs chicken is a term that reminds me of my beautiful Milka.
I was around 12 years old. My hand-raised, chocolate-colored hen had woken up paralyzed and couldn't stand up.
I insisted to take her to the vet, which was super crazy at the time ("who goes to the vet for a chicken?"). Actually, I was the only one with a bird in a waiting room full of cats and dogs, and people looked at me weirdly, lol.
The vet didn't know what she had because he wasn't even a bird specialist, so he said that he would take her to the city to perform some tests on her. The chicken got blood tests, X-rays (he thought she could've broken her hips), etc.
The vet went back after a weekend with the news that she had had Mareks. He explained to us that she would never recover and the best solution was to cull her, which I immediately refused to do. (He said it wasn't contagious, maybe it stops being contagious? and this was just an aftereffect of the infection? IDK. No other birds were infected, maybe it wasn't even Mareks in the end).
Anyway, he tried to explain to me that she would NEVER EVER get back on her feet and all of what that implied. I promised to take care of her to the last of her days, and I did so.
She didn't last long after that, only a few weeks, and perhaps I was being cruel unintentionally, but I gave it all for that hen, and I like to think that she was... fine? even with her limitations, I did everything I could for her adaptation.
I took her out to the sun every day, I placed her nearby her friends when they were dust bathing (she could dust bathe although with more limited movements). She was a cuddly chicken, so I cuddled with her; I fed her by hand, I found a more appropriate waterer for her condition...
I remember I gave her a lot of nutritive foods to help her "gather strength" (maybe I was waiting for a miracle?) and her favorite treats to make her happy. I remember being so frustrated because soon she didn't even look sick at all, she just couldn't stand up.
After failing to improvise a wheelchair for her, somehow I taught her how to slither...? And man, poor hen, but she really had a will to live and she quickly learned to go places that way, of course, she was slow and covered only short distances, but at least she could reach her special waterer, her feeder, and her nearest favorite spots on her own, and she managed to live a few more weeks with her flock.
She died peacefully in her sleep.