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

Abstract

Objectives: To 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.

Methods: A 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.

Results: The 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.

Conclusions: The 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.

Keywords: Diffusion tensor imaging; Magnetic resonance imaging; Parkinson's disease; Rapid eye movement sleep behavior disorder.