Objective: To compare progression of motor asymmetry using the MDS-UPDRS-III in Parkinson’s Disease (PD) with and without probable REM Sleep Behavior disorder (pRBD) over 5 years in the Parkinson’s Progression Markers Initiative (PPMI).

Background: Previous research has reported motor asymmetry in idiopathic RBD¹.  Similarly, other research has reported asymmetry in dopamine transporter imaging in PD with RBD (RBD+) than PD without RBD (RBD-), which might be underlying this increased motor asymmetry². On the other hand, there has also been research suggesting RBD+ presents more symmetrically than RBD-, due to more symmetrical nigrostriatal dopaminergic degeneration³. This conflicting evidence highlights the need for additional research to better elucidate how motor asymmetry differs between RBD+ and RBD-, as well as track its progression over time.

Method: 201 participants with PD (129 pRBD-, 72 pRBD+) from the PPMI were included. These participants had UPDRS-III assessment while ON medication at baseline and at 5-year follow-up. Four outcomes of motor asymmetry (bradykinesia asymmetry, rigidity asymmetry, tremor asymmetry, and combined bradykinesia-rigidity asymmetry) were calculated using the absolute value of the following equation: (right – left)/(right + left). Robust 2×2 mixed ANOVAs were used to explore the effect of RBD and time on motor asymmetry outcomes.

Results: Demographic data is reported in Table 1. There was a main effect of time on bradykinesia asymmetry (p < 0.01), rigidity asymmetry (p < 0.01), tremor asymmetry (p < 0.01), and combined bradykinesia-rigidity asymmetry (p < 0.01), indicating that asymmetry decreased over 5 years in all participants. We also found a main effect of RBD on bradykinesia asymmetry (p < 0.05), and combined bradykinesia-rigidity asymmetry (p < 0.01), indicating that pRBD+ had lower asymmetry in these motor outcomes than pRBD- at baseline and follow-up.

Conclusion: Over five years, all PD participants become less asymmetric in their motor symptoms, indicating more bilateral progression. pRBD+ appears to have reduced motor asymmetry, suggesting increased bilateral impairment compared to pRBD- at both time points. Future studies should confirm these differences in progression of motor asymmetry over time using other forms of motor assessment.

Table 1: Demographic Characteristics at Baseline

References: 1. Ehgoetz-Martens, K., Matar, E., Hall, J., Georgiades, M., Gilat, M., Shine, J., & Lewis, S. (2018). Exploring the neural correlates of gait asymmetry in idiopathic REM Sleep Behaviour Disorder. Movement Disorders, 33, S72-S72.
2. Yamada, G., Ueki, Y., Oishi, N., Oguri, T., Fukui, A., Nakayama, M., Sano, Y., Kandori, A., Kan, H., Arai, N., Sakurai, K., Wada, I.,& Matsukawa, N. (2019). Nigrostriatal dopaminergic dysfunction and altered functional connectivity in REM sleep behavior disorder with mild motor impairment. Frontiers in Neurology, 10, 802.
3. Knudsen, K., Fedorova, T. D., Horsager, J., Andersen, K. B., Skjærbæk, C., Berg, D., Schaeffer, E., Brooks, D. J., Pavese, N., Van Den Berge, N., & Borghammer, P. (2021). Asymmetric Dopaminergic Dysfunction in Brain-First versus Body-First Parkinson’s Disease Subtypes. Journal of Parkinson’s disease, 11(4), 1677–1687. https://doi.org/10.3233/JPD-212761

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MDS Abstracts - https://www.mdsabstracts.org/abstract/progression-of-motor-asymmetry-in-the-mds-updrs-iii-in-parkinsons-disease-with-and-without-rem-sleep-behavior-disorder-over-five-years/