Hi I have had 3 chickens in the last 6 months die of this disease. I have finally found the answer in a great book called "The joy of keeping chickens". it is a nutritional disease they seem drunken and tip there heads back and shake them from side to side, eventually its leads to paraylisis and death. it is found in chickens fed organic rations, to help them you need to put a vitamin supplement in their water. also only give the chooks fresh rations that are stored in cool dry locations. good luck I am going to try it today and hopefully a chicken that I have which looks like it has the start of it may be saved.