Gray matter structural alterations in idiopathic rapid eye movement sleep behavior disorder: A voxel-based meta-analysis

Background: Idiopathic rapid eye movement sleep behavior disorder (iRBD) is a robust prodromal marker of alpha-synucleinopathies. Increased neuroimaging studies have explored the morphological abnormalities in iRBD, but yielded inconsistent results.<br /> Methods: We conducted a systematic review and a voxel-wise meta-analysis of whole-brain voxel-based morphometry (VBM) studies using the anisotropic effect size version of seed-based d mapping (AES-SDM) to investigate gray matter volume (GMV) alterations in iRBD.<br /> Results: A total of 11 studies with 12 comparisons that included 341 iRBD patients and 288 healthy controls (HCs) were identified. Patients with iRBD showed decreased GMV in the bilateral superior frontal gyri and gyrus rectus, the right temporal pole, right caudate, and right olfactory cortex, while increased GMV in the bilateral cerebellum and thalamus, and left superior occipital gyrus, relative to HCs. These findings remained largely unchanged in jackknife sensitivity analyses. Conclusion: These abnormalities may represent the structural brain underpinnings of cognitive and sensorimotor dysfunctions in patients with iRBD and could enhance our understanding of the early signs of neurodegeneration in the prodromal stage of a-synucleinopathies.