Differences in [99mTc]TRODAT-1 SPECT binding to dopamine transporters in patients with multiple system atrophy and Parkinson's disease

Purpose: Multiple system atrophy (MSA), a disorder causing autonomic dysfunction, parkinsonism, and cerebellar dysfunction, is difficult to differentiate from other movement disorders, particularly early in the course of disease. This study evaluated whether [Tc-99m]TRODAT-1 binding to the dopamine transporter differentiates MSA from other movement disorders. Methods: Single-photon emission computed tomographic brain scans were acquired in 25 MSA patients, 48 age-matched controls, and 130 PD patients, 3 h after the injection of 740 MBq (20 mCi) of [Tc-99m]TRODAT-1. Regions of interest (ROIs) were placed manually on subregions of both basal ganglia and distribution volume ratios (DVRs) were calculated. Regional DVRs were compared between study groups in MSA patients. Student's tests were used to compare MSA patients with other study groups. Spearman correlations were used to compare DVRs with NP measures. Results: Based upon various motor scores, MSA and PD patients had comparable motor impairment, and were significantly impaired compared with controls. Mean DVRs in the basal ganglia of MSA patients were significantly less than those of controls, but generally higher (p < 0.05) than in PD patients. In particular, the MSA patients had significantly increased DVRs in the posterior putamen (mean 0.49 +/- 0.30) compared with PD patients (0.74 +/- 0.25). Conclusion: Movement disorder patients could be differentiated from controls, but MSA and PD patients could not be easily differentiated from each other. As a group, MSA patients had significantly higher mean [Tc-99m]TRODAT-1 binding, particularly in the posterior putamen, compared with PD patients and significantly lower binding compared with controls. This may reflect different pathophysiological processes of the two neurodegenerative diseases.