[Nuclear medicine imaging in patients with Parkinson's syndrome: an update].

Nuclear medicine imaging using positron emission tomography (PET) or single photon emission computed tomography (SPECT) has enabled to study not only the metabolism and blood flow in specific brain areas but also the quantification of the function of distinct molecules. With respect to Parkinson's disease PET and later SPECT allowed the number of dopaminergic neurons to be assessed in vivo. These quantifications are relevant to establishing a clinical diagnosis, assessing the progression of the disease or the survival of transplanted dopaminergic neurons. In addition both techniques have markedly contributed to our understanding of the pathophysiology of this disorder. More recently, molecular imaging has been directed towards understanding the pathophysiology of non-motor symptoms in this disorder.