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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]

We evaluated cerebellar subregional metabolic alterations in patients with cerebellar ataxia, a representative disease involving the spinocerebellum. We retrospectively analyzed 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) images in 44 patients with multiple system atrophy of the cerebellar type (MSA-C), 9 patients with spinocerebellar ataxia (SCA) type 2, and 14 patients with SCA type 6 and compared with 15 patients with crossed cerebellar diaschisis (CCD) and 89 normal controls. Cerebellar subregional metabolism was assessed using 13 cerebellar subregions (bilateral anterior lobes [ANT], superior/mid/inferior posterior lobes [SUPP/MIDP/INFP], dentate nucleus [DN], anterior vermis [ANTV], and superior/inferior posterior vermis [SUPV/INFV]) to determine FDG uptake ratios. MSA-C and SCA type 2 showed severely decreased metabolic ratios in all cerebellar subregions compared to normal controls (ANT, 0.58 ± 0.08 and 0.50 ± 0.06 vs. 0.82 ± 0.07, respectively, p < 0.001). SCA type 6 showed lower metabolic ratios in almost all cerebellar subregions (ANT, 0.57 ± 0.06, p < 0.001) except INFV. Anterior-posterior lobe ratio measurements revealed that SCA type 2 (Right, 0.81 ± 0.05 vs. 0.88 ± 0.04, p < 0.001; Left, 0.83 ± 0.05 vs. 0.88 ± 0.04, p = 0.003) and SCA type 6 (Right, 0.72 ± 0.05 vs. 0.88 ± 0.04, p < 0.001; Left, 0.72 ± 0.05 vs. 0.88 ± 0.04, p < 0.001) showed preferential hypometabolism in the anterior lobe compared to normal controls, which was not observed in CCD and MSA-C. Asymmetric indices were higher in CCD and MSA-C than in normal controls (p < 0.001), whereas such differences were not found in SCA types 2 and 6. In summary, quantitative analysis of cerebellar subregional metabolism ratios revealed preferential involvement of the anterior lobe, corresponding to the spinocerebellum, in patients with cerebellar ataxia, whereas patients with CCD and MSA-C exhibited more asymmetric hypometabolism in the posterior lobe. [ABSTRACT FROM AUTHOR]