[Basal ganglia and movement disorders : Part 1: the parkinsonian spectrum-Neuroradiological patterns and diagnostic considerations].

Movement disorders are a frequent yet diagnostically unspecific reason for referral in routine neuroradiological practice. Hypokinetic syndromes with parkinsonism in particular regularly raise the question of an underlying neurodegenerative disorder, while requiring careful differentiation from atypical parkinsonian syndromes and secondary causes. This first part of the review focuses on the neuroradiological assessment of degenerative movement disorders, with an emphasis on the parkinsonian spectrum. It is grounded in the functional anatomy of the basal ganglia and their integration into motor networks. Building on this framework, a practice-oriented diagnostic approach is presented in which clinical phenotypes, temporal evolution, and accompanying symptoms serve as guiding criteria for targeted image interpretation. The article addresses idiopathic Parkinson's disease as well as atypical parkinsonian syndromes, in particular progressive supranuclear palsy, multiple system atrophy, and corticobasal syndrome. Typical and atypical magnetic resonance imaging (MRI) patterns, established morphometric markers, and the diagnostic limitations of visual signs such as the swallow-tail sign are critically discussed. In addition, neuromelanin-sensitive MRI, susceptibility-based techniques, and artificial intelligence (AI)-supported approaches are reviewed, with explicit consideration of their current limitations. The aim of this contribution is to enable a structured and clinically robust neuroradiological assessment of parkinsonism and to use imaging in a targeted manner for differential diagnosis and guidance of further diagnostic work-up.