The role of molecular imaging in the differential diagnosis of parkinsonism.

This review focuses on the possibilities to use scintigraphic techniques to help differentiate neurodegenerative brain diseases associated with parkinsonian features. In particular, the findings of dopaminergic imaging, FDG PET imaging, and cardiac sympathetic imaging are described. Considerable overlap in individual data on striatal postsynaptic D2/3 binding and presynaptic DAT binding/DOPA uptake exists between different parkinsonian syndromes, which may hamper its role as the sole imaging technique to differentiate PD from other parkinsonian syndromes. The results of recent studies suggested, however, that the combination of pre- and postsynaptic dopaminergic imaging may gain further insight in the pathophysiological mechanisms in patients with parkinsonian features. Also, most of the commonly used DAT tracers bind not only to striatal DATs, but to serotonin transporters in extrastriatal brain areas as well. Preliminary studies suggest that this additional information may be helpful to increase the accuracy to differentiate between patients with parkinsonian features. Finally, both brain [18F]FDG PET and cardiac sympathetic imaging are very promising tools to differentiate different parkinsonian syndromes from each other in routine clinical studies.