REM sleep behaviour disorder (RBD) is associated with psychiatric symptoms, such as anxiety and depression. RBD is characterized by loss of normal skeletal muscle atonia during rapid eye movement (REM) sleep with prominent motor activity and dreaming and is a usual symptom of the early stages of Parkinson's disease (PD). Diffusion MRI connectometry was used to carry out group analysis between age and gender matched PD patients with RBD in with and without depression to characterize possible depression-related white matter microstructural changes in the Parkinson patients with RBD.

DWI images were obtained for 15 PD-RBD with depression and 27 PD-RBD without depression. This dataset was acquired on a 3 Tesla Siemens scanner, producing 64 DWI at b = 1000 s/mm2 and one b0 image. Diffusion MRI data were corrected for subject motion, eddy current distortions, and susceptibility artefacts due to the magnetic field inhomogeneity. Diffusion MRI connectometry was conducted in a total of 27 subjects using percentage measurement.

PD-RBD Patients with depressive symptoms showed decreased anisotropy (FDR < 0.05) in the fornix bilaterally, right cingulum, inferior longitudinal fasciculus bilaterally, right corticospinal tract and Genu of corpus callosum compared to PD-RBD patients without depression.

Since RBD is considered to be an early symptom of PD and also a marker of progression to PD, these results might PD-RBD patients with depression may progress dementing processes and visuospatial dysfunction earlier since fornix, cingulum and ILF have proven to be associated with these cognitive dysfunctions respectively.

The authors have not supplied their declaration of competing interest.