Objective: To investigate the motor and nonmotor features in isolated rapid eye movement sleep behavior disorder (iRBD) and to find the variables of polysomnography (PSG) correlating with the motor and nonmotor features, and striatal dopaminergic activity.

Background: Few studies have analyzed in detail the motor and nonmotor features together, and the correlation of their features with PSG findings was not reported.

Method: 21 patients with iRBD and 17 healthy controls participated. Participants were thoroughly investigated about motor and non-motor features. Olfactory function was assessed with a 12-item cross-cultural smell identification test (CC-SIT, Sensoics, Inc Haddon Heights, NJ). Motor function was measured with Hoehn and Yahr stage (HY stage), Unified Parkinson’s Disease Rating Scale (UPDRS) part III, finger tapping test (FTT), and gait test. We performed non-motor symptom scale (NMSS) and depression with Patient Health Questionnaire-9 (PHQ-9) and sleep problem with Parkinson’s disease sleep scale (PDSS), Epworth sleepiness scale (ESS), Korean version of Mini-Mental State Exam (K-MMSE) and Clinical Dementia Rating (CDR). Besides, all iRBD patients underwent a standardized, comprehensive neuropsychological test battery. PSG parameters and REM sleep disorder severity scale (RBDSS) were assessed.

Results: The mean values of K-MMSE, CDR, the number of steps in walking test, and CC-SIT were significantly lower, and of PHQ-9, HY stage, UPDRS III, the completion time in walking test, five domains of NMSS score (sleep/fatigue, attention/memory, gastrointestinal, urinary, and miscellaneous), and PDSS were significantly higher in iRBD patients (p < 0.05). There were significant correlations of percentage of tonic REM with pain score of NMSS (r = 0.686, p = 0.002), and percentage of phasic REM with visuospatial function (r = -0.507, p = 0.038). There were no correlations between RBD severity and striatal dopaminergic activities (p > 0.09).

Conclusion: Our results suggests that iRBD is a multisystem neurodegenerative disorder, and gait abnormalities may be a disease characteristic, possibly related to the akinetic-rigid phenotype seen in Parkinson’s disease patients. The correlation between pain and visuospatial dysfunction and RBD severity may be related to its pathogenesis.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-correlations-of-rbd-severity-with-motor-and-nonmotor-features-in-isolated-rbd-patients/