Objective: This study is to investigate the correlations between the abnormalities in the distribution of striatal dopamine transporter (DAT) and the expression of Parkinson’s disease (PD) related metabolic covariance pattern (termed PDRP) in the same REM sleep behavior disorder (IRBD) patients with comparison to PD using a dual tracer imaging design.

Background: Dopaminergic dysfunction and abnormal metabolic network expression have been observed in patients with idiopathic IRBD [1,2]. But the relationship between the two measures remains unclear.

Methods: Age-matched 37 polysomnogram-confirmed IRBD patients, 86 PD patients (mild, H&Y stage 1, 23 patients; moderate, H&Y2-3, 48 patients; advanced, H&Y4-5, 15 patients) and 15 control subjects performed concurrent PET scans with 11C-CFT to quantify striatal DAT binding and 18F-FDG to quantify PDRP expression. The correlations between the two measures were analyzed using the Spearman’s rho coefficients.

Results: IRBD patients were divided into two subgroups: with relatively normal (IRBDRN) or abnormal (IRBD-AB) DAT binding. Relative to the controls, significantly decreased DAT binding was present in all patient groups except for IRBD-RN. Significant increase in PDRP expression was present in all patient groups. There’re trends of decrease in DAT binding in the striatum and increase in PDRP expression from IRBD-RN to advanced PD. Significant but weak correlations were observed between PDRP expression and DAT binding in all sub-regions of the striatum in PD. Stronger correlations were observed in the putamen in IRBD-AB. No significant correlation was found in IRBD or IRBD-RN subgroup.

Conclusions: IRBD patients present an intermediate state in striatal DAT distribution and PDRP activity between PD and normal controls. The modest correlations between dopaminergic dysfunction and abnormal PDRP expression in both IRBD and PD suggest differences in network activity can’t be explained solely by nigrostriatal dopaminergic denervation.

References: [1] Iranzo A, Lomeña F, Stockner H, et al. Decreased striatal dopamine transporter uptake and substantia nigra hyperechogenicity as risk markers of synucleinopathy in patients with idiopathic rapid-eye-movement sleep behaviour disorder: A prospective study. Lancet Neurol. 2010;9:1070–7. [2] Holtbernd F, Gagnon J-F, Postuma RB, et al. Abnormal metabolic network activity in REM sleep behavior disorder. Neurology. 2014;82:620–7.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/dopaminergic-dysfunction-and-abnormal-metabolic-network-activity-in-rem-sleep-behavior-disorder/