To investigate whether polysomnogram (PSG)-proven rapid eye movement sleep behavior disorder (RBD) is associated with the severity of orthostatic hypotension (OH) in patients with multiple system atrophy (MSA).

RBD is a non-motor symptom in patients with α-synucleinopathy, such as Parkinson’s disease (PD) and MSA. In PD patients, RBD is associated with the clinical manifestations of both motor symptoms and other non-motor symptoms, such as OH and cognition correlating with poor prognosis. However, little is known about whether RBD affects the clinical manifestation in MSA.

Thirty MSA patients who underwent PSG, including 16 patients with MSA-P and 14 patients with MSA-C, according to the second consensus statement of the diagnosis of MSA, were retrospectively evaluated in this study. Assessment of OH and cognitive function were evaluated by the change of blood pressure within the first 3 minutes after standing and the Mini-Mental State Examination, respectively. 

Seventy-three percent of overall MSA patients were complicated with PSG-proven RBD. The baseline demographics data regarding gender, age at the onset of MSA and age at the evaluation did not show any difference between these groups. The marked reduction in systolic blood pressure after standing (24.1±14.3 vs 0.8±13.4, p=0.009) and diastolic blood pressure (10.1±13.4 vs -3.3±4.6, p=0.075) were observed in MSA-P patients with RBD. In contrast, RBD did not affect the degree of orthostatic hypotension in MSA-C patients. The cognition was not related to the presence or absence of RBD in both MSA-P and MSA-C patients.

Our study revealed that MSA-P patients complicated with RBD show severe OH,  though not in MSA-C patients, implying that the propagation of abnormal α-synuclein in the lesions associated with OH is different between MSA-P and MSA-C, as well as the difference of primary lesion in each subtype, such as basal ganglia or cerebellum.