The association between Parkinson's disease symptom side-of-onset and performance on the MDS-UPDRS scale part IV: Motor complications

Introduction: Parkinson's disease (PD) is a neurodegenerative condition associated with aging characterized by loss of dopamine-producing neurons in the substantia nigra pars compacta and a reduction in dopamine levels in the striatum. PD is commonly treated using dopamine-replacement medication called levodopa. Levodopa has decreasing efficacy over time. Periods when levodopa is not effective at controlling symptoms of PD are called “OFF-time” or “medication-related motor fluctuations,” (MRMF). One characteristic of PD is unilateral side of symptom onset. Previous studies have found that side of onset was associated with differential motor and cognitive PD-related symptoms. The main study objective was to examine differences in left and right onset PD patients and OFF-time as measured by the Movement Disorders Society Unified Parkinson Disease Rating Scale (MDS-UPDRS) Part IV Sum Score and Part IV item scores. Methods: 64 individuals with mild-moderate PD (age: M(SD) = 68.72 (8.88)), years with PD: M(SD) = 6.61 (5.05); Hoehn and Yahr stage Med (1st, 3rd quartile) = 2.0 (2.0, 3.0) were assessed with the MDS-UPDRS parts I-IV. We conducted two-tailed independent sample t-tests to examine the differences between PD patients with left versus right onset. Results: Right onset PD was significantly associated with more overall MRMF (p = 0.01), more OFF-time (p = 0.04), greater impact of motor fluctuations on daily life (p = 0.02) and more complex (unpredictable) MRMF (p = 0.01). Conclusion: People with right onset PD have more complications with levodopa treatment. Alternative and/or adjuvant treatments to levodopa may be particularly beneficial for those with right onset PD.