Nigrosome 1 imaging: technical considerations and clinical applications.

A pathological study by Damier et al demonstrated that nigrosome 1, a dopaminergic neuron-rich region in the substantial nigra, is the most severely affected region in idiopathic Parkinson's disease. Since then, researchers have identified the location of nigrosome 1 in the dorsal aspect of the substantia nigra using susceptibility-weighted imaging in MRI. Although this observation was reconfirmed by various imaging techniques and imaging planes, non-standardized imaging methods may rather limit the generalized use of this imaging finding. The aim of this review is to revisit the anatomical definition of the nigrosome 1 region using high-spatial-resolution susceptibility map-weighted MRI in order to help the readers to determine the presence or absence of an abnormality in the nigrosome 1 region. Thereafter, we discuss the current status of nigrosome 1 imaging at 3 T and show how to improve the imaging quality for better assessment of nigrosome 1. We also illustrate the imaging findings of various patients who presented with parkinsonism, which can help the readers to learn how to use these images in practice. Lastly, we discuss potential future works with nigrosome 1 susceptibility map-weighted MRI.