I think this is wry neck. I say this because in my own flock I've had this three times. I was able to cure all three with it coming back months later and that particular bird passed. Wry neck itself is NOT a disease but a symptom. There are a few usual causes. One is vitamin defiency. For that you use poultry vitamin B, children's liquid vitamin poly visol without iron, small amount of selenium (large amounts can be toxic) and human vitamin e. I squeezed the vitamins together except the poultry vitamin goes in the water. I mixed with scrambled eggs. For the first few weeks I had to help them eat and drink as they couldn't do it themselves in the beginning. It took a full 4 weeks of treatment to get back to normal. Now if you think the bird has had a brain injury you can add prednisone to the vitamins. For exact doses go online to browneggblueegg.com and in search look up crook neck. He refers to silkies but treatment applies to all. Hope this helps. When my birds got wry neck they would walk backward,do summersaults, couldn't lift their heads, and had small spasms. It takes patience and love but can definitely be cured in most cases.