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The severity of parkinsonism and response to levodopa vary in patients with multiple system atrophy (MSA) because of the heterogeneity of nigrostriatal neuropathology. To investigate the difference in clinical features between MSA patients with predominantly pre-synaptic nigrostriatal dysfunction and those with trans-synaptic nigrostriatal dysfunction. We retrospectively analyzed clinical data of 61 patients with MSA who underwent both [18F]FP-CIT-PET and [18F]FDG-PET within 3 months of clinical evaluation, and who had ≤3 years of disease duration. Tracer uptake of the striatum on [18F]FP-CIT-PET and glucose metabolism of the striatum on [18F]FDG-PET were analyzed using eight striatal subregional volumes-of-interest templates. The patients were classified into two subgroups according to the predominant pre-synaptic tracer uptake loss of the posterior putamen on [18F]FP-CIT-PET (MSA-SNpc, n = 21) and trans-synaptic dopaminergic dysfunction reflected by both [18F]FP-CIT-PET and [18F]FDG-PET (MSA-STR, n = 40). Parkinsonian features were significantly more severe in the MSA-STR group than in the MSA-SNpc group (P =.005) and cerebellar ataxia was significantly more severe in the MSA-SNpc group (P =.036). The cerebellar type of MSA was significantly more common in the MSA-SNpc group (P =.001). There was no difference in age at onset, disease duration at the time of study, or Mini-Mental Status Examination scores between the groups. Patients with MSA showed distinct clinical features depending on whether the pattern of nigrostriatal dysfunction was predominantly pre-synaptic or trans-synaptic. • Brain [18F]FP-CIT- and [18F]FDG-PET is useful to understanding the features of MSA. • Parkinsonism is more severe in MSA with trans-synaptic nigrostriatal dysfunction. • Cerebellar ataxia is more severe in MSA with presynaptic nigrostriatal dysfunction. • MSA shows distinct features depending on the pattern of nigrostriatal dysfunction. [ABSTRACT FROM AUTHOR]

Drug-induced parkinsonism (DIP) is the common cause of parkinsonism. It is difficult to make a differentiation between DIP and Parkinson's disease (PD) because there are no notable differences in the clinical characteristics between the two entities. In this study, we examined the relationship between the characteristics of [F] fluorinated- N-3-fluoropropyl-2-β-carboxymethoxy-3-β-(4-iodophenyl)nortropane (FP-CIT) positron emission tomography (PET) images and clinical features in DIP patients. We retrospectively studied 76 patients with DIP who underwent [F] FP-CIT PET. We also enrolled 16 healthy controls who underwent it. We compared the clinical characteristics between the DIP patients with normal [F] FP-CIT PET scans and those with abnormal ones. Symmetric parkinsonism was more frequent in the patients with normal [F] FP-CIT PET scans as compared with those with abnormal ones. Interval from drug intake to onset of parkinsonism was longer in the patients with abnormal [F] FP-CIT PET scans as compared with those with normal ones. A semi-quantitative analysis showed that specific to non-specific binding ratios in the putamen was lower in the patients with abnormal [F] FP-CIT PET scans as compared with those with normal ones and the age-matched control group. Our results suggest that symmetric parkinsonism was more prevalent, and the duration of drug exposure before the onset of parkinsonism was shorter in the patients with normal [F] FP-CIT PET scans as compared with those with abnormal ones. [ABSTRACT FROM AUTHOR]