Neuroimaging in Atypical Parkinsonian Disorders

Atypical parkinsonian disorders are a heterogeneous group of neurodegenerative diseases that include progressive supranuclear palsy, multiple system atrophy, and corticobasal degeneration. In early disease stages, symptoms often overlap, and it may be difficult to distinguish these entities and to differentiate them from idiopathic Parkinson disease solely by clinical examination. Conventional MR imaging as well as advanced MR imaging techniques and PET/SPECT imaging are helpful tools to enhance the accuracy of clinical diagnosis in these disorders. The aim of this review was (1) to present and discuss the relevance of advanced MR imaging techniques (voxel-based morphometry, iron-sensitive MR imaging, DTI, spectroscopy) and to present the radiotracer imaging techniques and (2) to define the different types of atypical parkinsonian disorders, summarize the most important radiologic findings of conventional MR imaging for each atypical parkinsonian disorder, show the usefulness of advanced MR imaging techniques in clinical practice, and present the radiotracer imaging findings. Conventional MR imaging can contribute to differentiating atypical parkinsonian disorders from each other and from Parkinson disease, showing specific patterns of atrophy combined with classic patterns of T2 signal intensity change in the basal ganglia, pons, and middle and superior cerebellar peduncles. Advanced MR imaging sequences and radiotracer imaging may be most helpful in the early diagnosis of atypical parkinsonian disorders.

Learning Objective: To recognize the conventional MR findings for each atypical parkinsonian disorder and to know the advanced MR imaging techniques and radiotracers that are useful in the differentiation of atypical parkinsonism in clinical practice.