Motor laterality asymmetry and nonmotor symptoms in Parkinson's disease

Background: In patients with Parkinson's disease (PD), asymmetric motor signs provide an interesting model to evaluate whether asymmetric nigrostriatal degeneration can affect neuropsychological function and other nonmotor symptoms (NMS). This study was designed to evaluate the predominant laterality of motor symptoms and its relationship with cognition and other NMS in idiopathic PD. Methods: Nationwide, longitudinal, and multicenter study (ELEP Registry) using outpatients with PD. Left PD (LPD) and right PD (RPD) was defined based on the motor signs on the SCOPA‐motor scale. To include the clinical spectrum of asymmetric PD patients, we considered two groups of patients with mild‐moderate and extreme asymmetry. Predominant LPD or RPD with mild‐moderate versus extreme asymmetry were compared using the following scales: cognition, psychosis (Parkinson Psychosis Rating Scale), anxiety/depression, sleep (and autonomic dysfunction at baseline and 1 year later. Nonparametric tests were used for comparison. Results: One hundred forty‐nine PD patients (74 RPD and 75 LPD) with mild‐moderate asymmetry and 90 (47 RPD and 43 LPD) with extreme asymmetry and a mean age of 64.5 (10.4) years were included. Extreme RPD had higher Parkinson Psychosis Rating Scale scores over time (P = 0.005) compared with LPD, but no significant differences were observed between LPD and RPD in terms of other NMS. Conclusions: These findings suggest that damage to left‐hemisphere plays a disproportionately greater role in PD‐related psychosis over time. In contrast, motor laterality does not consistently affect other NMS, suggesting that NMS are related to a more widespread brain disorder. © 2009 Movement Disorder Society