Positron emission tomography in diagnosis and differential diagnosis of Parkinson's disease

Parkinson's disease (PD) and atypical Parkinsonian syndromes (aPS) belong to the most common neurologic illnesses. Diagnosis and differential diagnosis of these syndromes is primarily based on well-defined clinical criteria, however, may be difficult in early and particular preclinical/premotor stages. Molecular imaging with PET offers here a broad variety of tools supporting the classification of Parkinsonian syndromes including their early and differential diagnosis, assessment of disease progression and evaluation of the efficacy of therapies. The more widely applied PET imaging techniques have focused on the assessment of neurotransmitter systems, here predominantly the pre- and postsynaptic dopaminergic functions, but also others like the serotonergic and cholinergic system. Beyond, refined methods depict distinct patterns of glucose metabolism in the various Parkinsonian syndromes, and focus on further targets such as neuroinflammation, load of amyloid plaques, and cardiac sympathetic denervation. This overview discusses the important PET applications in the field with a main emphasis on their clinical utilization but also highlights scientific applications which may grant further insights in the pathophysiology of PD and aPS.