Did you hatch him or purchase him? Has he always been like this or did it just come on?
Honestly from looking at him I'd almost venture to guess some sort of crop/throat deformity, perhaps he has to get his head back that far for it to comfortably go down? Just a thought.
How is he when he eats...
Definitely not normal, I've never seen anything like that before.
How are his motor skills, is he able to walk about, coordinate, hold his head normally?