Can loss of the swallow tail sign help distinguish between Parkinson Disease and the Parkinson-Plus syndromes?

•The swallow tail sign is lost more often in movement disorder groups than controls.•The swallow tail sign is present at similar rate in all movement disorder subgroups.•Lost swallow tail sign distinguishes control from movement disorder patients.•Lost swallow tail sign cannot distinguish between movement disorder subgroups.•No difference in the presence of the swallow tail sign was seen at 1.5 or 3 Tesla.