Objective: To investigate structural and functional alterations in patients with idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD) compared with healthy controls.

Methods: Twenty-seven patients with polysomnography-confirmed iRBD and 33 healthy subjects were recruited. All subjects underwent a 3-tesla structural and resting-state functional magnetic resonance imaging (fMRI) examination. Voxel-based morphometry (VBM) analysis was performed to assess grey matter alterations between groups. The amplitude of low-frequency fluctuations (ALFF) was calculated and then compared to measure differences in spontaneous brain activity. Correlations were performed to explore associations between imaging metrics and clinical characteristics in iRBD patients.

Results: Compared with healthy controls, patients with iRBD had decreased grey matter volume in the frontal, temporal, parietal, occipital cortices as well as increased grey matter volume in cerebellum posterior lobe, putamen, and thalamus. Patients with iRBD also exhibited increased ALFF values in the right parahippocampal gyrus. Olfaction correlated with ALFF value changes in occipital cortices.

Conclusions: Patients with iRBD had widespread decreases of grey matter volume. Increases of grey matter volume in cerebellum, putamen, and thalamus may suggest a compensatory effect, while the altered ALFF values in parahippocampal gyrus and occipital cortices may play a role in theunderlying process of neurodegeneration in this disorder.