^99mTc-TRODAT-1 imaging of multiple system atrophy

Using ^99mTc-TRODAT-1 (^99mTc-[2[[2-[[[3-(4- chlorophenyl)-8-methyl-8-azabicyclo[3,2,1]-oct-2-yl]-methyl](2-mercaptoethyl) amino]ethyl]amino]ethane-thiolato(3-)-N2,N2′,S2,S2]oxo-[1R-(exo-exo)])) brain SPECT imaging, we measured striatal dopamine transporters (DATs) activity in multiple system atrophy (MSA) to investigate the possibility of differentiating it from Parkinson's disease (PD) and to correlate the findings with the parkinsonian (MSA-P) and cerebellar (MSA-C) subtypes of MSA. Methods: Forty-nine patients with probable MSA (30 MSA-P, 19 MSA-C), a disease control group of 36 age- and disease duration-matched patients with probable PD, and a healthy control group of 33 age-matched healthy volunteers participated in a SPECT study. The ratios of specific striatal binding-to-nonspecific occipital binding, including the striatum-to-occipital ratio (S/O), putamen-to-occipital ratio (P/O), caudate nucleus-to-occipital ratio (C/O), and putamen-to-caudate nucleus ratio (P/C), were calculated. The statistical analyses of uptakes among 4 groups used ANOVA followed by Games-Howell's multiple comparisons. The Spearman correlation coefficient between the motor scores of Unified Parkinson's Disease Rating Scale (UPDRS-III) and those binding ratios of the MSA-P and MSA-C groups and the PD group was also performed. Results: The striatal binding was more symmetrically reduced in the MSA-P (asymmetric index, 14.2) and MSA-C (asymmetric index, 8.1) groups, in contrast to the greater asymmetric reduction in the PD group (asymmetric index, 28.6). Overall striatal binding was significantly reduced in the MSA-P (-59.8%), MSA-C (-29.9%), and PD (-58.0%) groups with no overlap between these values and those of the control group. Like the PD group, bilateral P/O, C/O, and S/O ratio values were significantly reduced in the MSA-P and MSA-C groups. Nevertheless, the reduction of bilateral P/O and S/O ratios was more for the MSA-P group than for the MSA-C group. P/C ratios showed that the MSA-P and PD groups had similar patterns of nigral impairment, but the MSA-C group had a different pattern. No correlation between the UPDRS-III scores and ^99mTc-TRODAT-1 bindings was found in both MSA-P and MSA-C groups; in contrast, a significant negative correlation was noted in the PD group. Conclusion: ^99mTc-TRODAT-1 brain SPECT is capable of scientifically differentiating between the MSA-P and MSA-C subtypes, and MSA-P has more symmetric nigrostriatal damage than that in PD. ^99mTc-TRODAT-1 brain SPECT imaging probably could provide important information to differentiate MSA from PD.