Swallow Tail Sign: Revisited
Malte Brammerloh, Evgeniya Kirilina, Anneke Alkemade, Pierre‐Louis Bazin, Caroline Jantzen, Carsten Jäger, Andreas Herrler, Kerrin Pine, Penny Gowland, Markus Morawski, Birte U. Forstmann, Nikolaus Weiskopf
Abstract
The loss of the radiologic swallow tail sign on MRI scans of the substantia nigra is a promising diagnostic marker of Parkinson disease (1), although its anatom-ic underpinning is unclear. An early influential study showed that the hyperintense inner part of the swallow tail sign on T2*-weighted images (STh) corresponds to iron-poor areas in substantia nigra and suggested it to equal nigrosome 1, the dopaminergic region affected earliest and strongest in Parkinson disease (2). This would render the STh a cellularly specific marker (2). However, recent postmortem tissue studies have chal-lenged this interpretation, reporting that nigrosome 1 is hypointense in T2*-weighted images (3,4). We com-bined three-dimensional histology with 7-T in vivo and postmortem MRI to demonstrate that nigrosome 1 and the radiologic STh are partially overlapping but distinct.