Absent swallow tail sign is seen in: (A) Huntington's chorea, (B) Alzheimer's disease, (C) Parkinsonism, (D) Progressive supranuclear palsy
Answer is C. SWALLOW TAIL SIGN: The Swallow tail sign describes the normal axial imaging appearance of nigrosome-1 within the substantia nigra on high resolution T2*/SWI weighted MRI. Absence of the sign (absent swallow tail sign) is repoed to have a diagnostic accuracy of greater than 90% for Parkinson disease. Figure showing normal swallow tail. Figure showing absent swallow tail Figure showing absent swallow tail sign in Parkinsonism.