Not necessarily. It sort of depends on cause, but if it is treatable, it’s treatable at home.
If you happen to find it, the first thing I do is take a vitamin E pill and mix the contents with a small amount of food. I’ll also mix in selenium if I have it, because it aids in the absorption of vitamin E. Then, you need to hold their head upright sort of to allow them to eat and drink. Usually after a few days with vitamin E they should do better.
This is why I always add extra vitamin E to my baby silkies diet, at least occasionally.
However, if the condition is cause by injury or neurological, then you might not be able to fix it and the most humane thing then would be to put the chicken down as it will just slowly starve to death or die of thirst.