Patterns of cortical thinning in idiopathic rapid eye movement sleep behavior disorder

Abstract

Rapid eye movement sleep behavior disorder (RBD) is a parasomnia considered as a risk factor for synucleinopathies, such as Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). We investigated gray matter thickness, gray matter density, and white matter integrity in idiopathic RBD (iRBD) patients using corticometry, voxel-based morphometry (VBM), and diffusion tensor imaging (DTI), respectively. Twenty patients with polysomnography-confirmed iRBD (mean age, 64.2 ± 7.0; 20 men) and 42 age- and gender-matched healthy controls (mean age, 63.2 ± 7.3, 28 men) underwent a 3T structural and diffusion MRI examination. Corticometry, VBM, and DTI data were analyzed respectively using both the CIVET pipeline for minctools and the SurfStat toolbox for MATLAB, FSL-VBM, and Tract-Based Spatial Statistics (TBSS) in FSL. For the corticometry and VBM analyses, age and gender were covaried out, whereas only age was used for DTI analyses. Several regions of the brain presented with decreased cortical thickness in iRBD patients compared to the controls, mainly in the frontal cortex (i.e., gyrus rectus, orbitofrontal cortex, superior frontal gyrus, supplementary motor area), the cingulate and paracingulate cortices, the precuneus, and the lingual and fusiform gyri. As regards gray matter density and white matter integrity, no significant differences between groups were found. iRBD patients have structural alterations in gray matter thickness, mainly in the frontal and cingulate cortices, the precuneus, and the fusiform and lingual gyri. Corticometry appears to be more sensitive than traditional VBM for visualizing gray matter alterations in iRBD patients. The pattern of cortical gray matter abnormalities found in iRBD patients shares several similarities with that found in PD and DLB. The study was supported by grants from the Canadian Institutes of Health Research and the Fonds de Recherche du Québec – Santé.