Movement Disorders: Focus on Parkinson’s Disease and Related Disorders

Abstract

Positron emission tomography (PET) and magnetic resonance imaging (MRI) are imaging techniques providing the foundation for the study of neurochemical, functional, and structural abnormalities associated with the pathology of movement disorders. The availability of several PET radioligands for imaging the monoaminergic systems in Parkinson’s disease (PD) and related disorders has provided the opportunity to apply different tools to support the diagnosis of degenerative parkinsonism and to examine the link between dopaminergic or serotoninergic dysfunction and motor symptoms, cognitive function, behavior, and depression. FDG-PET is at present acknowledged as imaging tool to support the differential diagnosis between PD and atypical parkinsonian disorders, and D2 receptor imaging with PET can also represent a useful imaging tool in this context. MRI techniques have also a major role in the diagnostic workup of patients with parkinsonism. Structural MRI is a cornerstone for the assessment of patients with atypical parkinsonism and to rule out possible secondary causes of parkinsonism. Diffusion-weighted MRI has gained increasing attention because of the possibility to examine the diffusivity of water molecules in relation of neurodegenerative processes at the level of the basal ganglia or other subcortical structures. Functional MRI, although mostly a research tool, can provide valuable information to examine patterns of functional activation and brain connectivity that can be associated to specific motor, cognitive, or behavioral symptoms of different parkinsonian disorders. PET and MRI have so far been used separately or in a complementary fashion, but the recent development of hybrid PET/MR systems possesses a relevant question about the advantages of combined imaging in the area of movement disorders. In this chapter the role of each imaging modality will be summarized with regard to clinical and research applications in PD patients and in patients with related parkinsonian disorders. The chapter will focus on PD and atypical parkinsonian disorders, such as multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD). Potential synergies between the two imaging modalities will be discussed to identify potential advantages of combined or simultaneous PET/MRI and future applications.