Interesting, I'd never heard of that. Either way, it does indicate neurological dysfunction, can't really be due to anything else whatever the mechanical process is, but I'd guess you agree with that anyway.
This quote from the thread you linked to is a bit of a gobsmacker:
Quote: Whoa there... Something that causes them to fail to survive under normal conditions should never, ever be described as 'normal' for a species unless that species is already dying out due to severe problems... 'Normal' in that specific scenario, just because it's common, but certainly not natural nor acceptable.
When 3 out of 12 poults have 'F.O.S', and the rest are normal, you don't describe the defective ones that can't function without assistance as 'normal'. :/
(Not to have a go at kuntrygirl there, at all, she was just relaying info she was told, it's just a shocking bit of info she found there...)
Sounds to me like it's a congenital abnormality possibly related to or similar to tetanic torticollar spasm, since that's inherited and everyone said they also found 'F.O.S' was passed on through one family line, specifically the male line.
It sounds like it's roughly the same thing anyway, I've had a hen given to me with T.T.S. and her head would go back like described, but she didn't flip. Naturally I didn't breed her, and the other turkeys hated her and eventually killed her despite my attempts to stop them (some helpful person put the turkey in with her wannabe-killers despite my explicit instructions not to, and the reasons why not being made clear)...
Best wishes.