Objective: Cardiac (123)I-metaiodobenzylguanidine (MIBG) scintigraphy studies of patients with idiopathic Parkinson's disease (PD) found decreased uptake. Whether this decrease is associated with clinical severity as assessed by the Unified Parkinson's Disease Rating Scale (UPDRS) and the phenotypes of PD has not been determined.
Methods: Cardiac MIBG scintigraphy was performed on 34 patients with PD, 7 with multiple system atrophy (MSA), 4 with dementia with Lewy bodies (DLB), and 11 normal controls (NCs). Early and delayed MIBG heart/mediastinum (H/M) ratios were evaluated. PD severity was assessed by the Hoehn and Yahr (H-Y) stage and UPDRS. Patients were grouped in two phenotypes, tremor and postural instability gait difficulty (PIGD)-dominant groups based on UPDRS components. Associations between MIBG uptake and age at onset, UPDRS, and disease phenotype were analyzed in each group.
Results: The early H/M ratio was significantly lower in patients with PD (1.45+/-0.207) than in the NCs (2.08+/-0.231), and in those with MSA (1.99+/-0.284), but not in those with DLB (1.29+/-0.0435). The delayed H/M ratio for PD (1.33+/-0.276) also was significantly decreased as compared to the ratios for NCs (2.17+/-0.286) and MSA (2.16+/-0.414) but not DLB (1.16+/-0.0949). The early H/M ratio was significantly correlated with both UPDRS score and age at onset, whereas the delayed H/M ratio only was significantly correlated with age at onset. The PIGD-dominant group had significantly higher UPDRS scores and lower H/M ratios than the tremor-dominant group.
Conclusion: Cardiac MIBG scintigraphy can be used to differentiate PD from MSA and NC, and to determine the disease severity and phenotypes of PD.