Differences in white matter microstructure between Parkinson's disease patients with and without REM sleep behavior disorder.

REM sleep behavior disorder (RBD) is characterized by increased muscle tone and violent limb movements and usually occurs during the early stages of Parkinson disease (PD). PD patients with RBD represent faster motor progression and cognitive dysfunction. We used diffusion imaging to assess which regions are involved in this phenomenon. In the current study, we computed Quantitative Anisotropic (QA), which is based on spin distribution function (SDF) that quantifies the density of diffusing water and is more sensitive to psychological differences between groups and also diffusion MRI connectometry to conduct group analysis between age and gender matched PD patients with and without RBD. The major regions with significantly reduced QA in PD patients with RBD were left and right cingulum and left and left inferior occipital fasciculus.