I'll just chime in here that there's always the possibility that it isn't actually PPMV. For a certainty, feed him or her all that she wants to eat and see if you can bring his or her weight up to the point where the breastbone ("keel", "sternum" or "carina", believe it or not) isn't protuding. That's always the first priority, where and when possible.
Regarding seizures (neck-twisting and other such behaviors), the symptoms merely demonstrate which neurological systems are involved and not which pathogen is the actual cause. Literally, a huge amount of birds with these symptoms are suffering from a chronic infection of things that can be cured with the right medications and therapy.
That being said, sometimes caregivers aren't in a position to acquire or administrate such therapies, or don't have the veterinary talent or resources available and management ends up being the only possibility.
On a deal like this, you'd want to stabilize the bird's weight and see if it gets over the torticollis (neck-twisting) or if it remains a chronic condition. That's going to take a few weeks, at least.
Pidgey
