Neural substrates of rapid eye movement sleep behavior disorder in Parkinson's disease

• PD patients with RBD had atrophy of the left posterior cingulate and hippocampus.
• No difference in the ascending pathways from PPN to thalamus regarding RBD in PD.
• RBD in PD may involve gray matter change in the major cortical hubs of the DMN.

ObjectivesTo investigate neural substrates of symptomatic rapid eye movement sleep behavior disorder (RBD) in Parkinson's disease (PD) by analyzing brain changes based on both hypothesis-free and hypothesis-driven neuroimaging analyses.MethodsA total of 63 subjects (14 PDRBD−, 24 PDRBD+, and 25 age-matched healthy controls = HC) were enrolled in this study. RBD was defined by RBD screening questionnaire with video-polysomnographic confirmation. All subjects underwent volumetric and diffusion tensor imaging. The whole brain gray- and white-matter changes were analyzed and the central ascending cholinergic pathway involving the pedunculopontine nucleus and thalamus was compared with a region-of-interest analysis and probabilistic tractography.ResultsThe PDRBD+ group showed decreased gray matter volume of the left posterior cingulate and hippocampus compared to the PDRBD− and additional gray matter decrease in the left precuneus, cuneus, medial frontal gyrus, postcentral gyrus and both inferior parietal lobule compared to the HC group (uncorrected p < 0.001, k = 50). There were no significant differences in white matter changes between the PDRBD− and PDRBD+ groups both by fractional anisotropy and mean diffusivities. However, both PD groups showed widespread changes by fractional anisotropy reductions and mean diffusivity increments compared to HC (p < 0.05 corrected). There were no significant differences in tract-based spatial statistics and the normalized tract volumes as well as the diffusion indices of both the thalamus and pedunculopontine nuclei among the study groups.ConclusionsThe appearance of RBD in PD may be related to regional gray matter changes in the left posterior cingulate and hippocampus but not localized to the brainstem.