To elucidate alteration of brain function network in the prodromal stage of α-synucleinopathy, we compared resting-state functional connectivity MRI (rsfcMRI) between patients with RBD and healthy elderly controls (HCs).

In RBD, abnormality of the basal ganglia network (BG) was reported previously, but the number of participants was limited and alteration of network other than BGN was not described.

We recruited 55 patients with polysomnography-confirmed idiopathic RBD (69.6 ± 5.77 years old, 39 males). RsfcMRI scans were acquired with echo-planar imaging for 10 min with eyes open. FSL (FMRIB's Software Library) was used for data analysis. Forty-four resting-state network (RSN) components were extracted from 70 age-matched HCs (68.7 ± 6.27 years old, 38 males), using group Independent Component Analysis, followed by a dual regression analysis. Correlation analysis was performed between functional connectivity (FC) of the RBD group and a clinical score. A threshold was set at P=0.05 corrected across voxels.

We examined BG, cerebellar, sensorimotor (SM) and executive control (EC) RSN. The RBD group showed lower FC in the midbrain (p = 0.05) in the analysis of BG network, in the right motor cortex (p = 0.02) in the analysis of SM network and dorsolateral prefrontal cortex (p = 0.04) in the analysis of EC network. A negative correlation was found between MDS-UPDRS part I score and right frontal pole (p = 0.04) in the analysis of BG network.

We performed rsfcMRI in patients with polysomnography-confirmed RBD in a larger cohort than before. We replicated the previous finding of BGN abnormality in RBD. Here we extend previous knowledge by reporting abnormality in SM and EC RSN. Furthermore, the non-motor symptoms were correlated with FC between BGN and the frontal pole. It is interesting to see how these abnormalities in RBD evolve over time in the J-PPMI cohort.