Phenomenology of rapid eye movement (REM) sleep behavior disorder in Parkinson's disease: A descriptive study using the REM sleep behavior disorder severity scale (RBDSS)

Using the rapid eye movement (REM) sleep behavior disorder severity scale (RBDSS) as a reliable clinical tool we further assessed the phenomenology of REM sleep behavior disorder (RBD) in 56 Parkinson's disease patients with RBD. The scale uses phenomenological categories based on the localization of movements in the distal or proximal extremities and/or involving the trunc and on the presence or absence of vocalizations. Inter-rater reliability has been published previously. In the current study we looked into the distribution of motor and vocal phenomena. We identified a small percentage of patients with only vocalizations (4/56), and 8/56 patients with and 10/56 patients without vocalizations and small nonviolent movements of the distal extremities or facial jerks. Ten patients showed more forceful movements of the proximal extremities, 11 patients with movements involving the proximal extremities had additional vocalizations, 5 patients were recorded with axial involvement, and 12 patients with axial movements and vocalizations. These findings underline the clinical variety of RBD manifestation in Parkinson's disease patients without a certain pattern. However, both extreme variants, the mild one and the violent one, are rare. The RBDSS facilitates the risk estimate for harmful behaviors and may be recommended for comparative studies on RBD and its pharmacotherapy.