Imagine your brain is a bustling city, humming with activity. Now imagine there’s construction going on, making the city less efficient. That’s what happens in idiopathic rapid eye movement Sleep Behavior Disorder (iRBD) and Parkinson’s disease without RBD (nRBD-PD). In this study, scientists examined how these two conditions affect the brain’s functional network, which is like the city’s infrastructure. They found that both iRBD and nRBD-PD patients had deficits in attention, executive function, and memory. The brain networks in both groups showed decreased efficiency and increased path length, meaning they were less connected and slower. However, there were also some differences. Nodal efficiency was decreased in both conditions, but the specific brain regions affected were not exactly the same. These findings suggest that while iRBD shares some similarities with PD, it also has unique characteristics. By understanding these changes in brain network properties, scientists can gain insights into the progression of these conditions and potentially develop new treatments.

PurposeIdiopathic rapid eye movement Sleep Behavior Disorder (iRBD) is considered as a prodromal and most valuable warning symptom for Parkinson’s disease (PD). Although iRBD and PD without RBD (nRBD-PD) are both α-synucleinopathies, whether they share the same neurodegeneration process is not clear enough. In this study, the pattern and extent of neurodegeneration were investigated and compared between early-stage nRBD-PD and iRBD from the perspective of whole-brain functional network changes.MethodsTwenty-one patients with iRBD, 23 patients with early-stage nRBD-PD, and 22 matched healthy controls (HCs) were enrolled. Functional networks were constructed using resting-state functional MRI (fMRI) data. Network topological properties were analyzed and compared among groups by graph theory approaches. Correlation analyses were performed between network topological properties and cognition in the iRBD and nRBD-PD groups.ResultsBoth patients with iRBD and patients with early-stage nRBD-PD had attention, executive function, and some memory deficits. On global topological organization, iRBD and nRBD-PD groups still presented small-worldness, but both groups exhibited decreased global/local efficiency and increased characteristic path length. On regional topological organization, compared with HC, nRBD-PD presented decreased nodal efficiency, decreased degree centrality, and increased nodal shortest path length, while iRBD presented decreased nodal efficiency and nodal shortest path. For iRBD, brain regions with decreased nodal efficiency were included in the corresponding regions of nRBD-PD. Nodal shortest path changes were significantly different in terms of brain regions and directions between nRBD-PD and iRBD. Attention deficits were correlated with local topological properties of the occipital lobe in both iRBD and nRBD-PD groups.ConclusionBoth global and local efficiency of functional networks declined in nRBD-PD and iRBD groups. The overlaps and differences in local topological properties between nRBD-PD and iRBD indicate that iRBD not only shares functional changes of PD but also presents distinct features.

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