The Association between Motor Laterality and Cognitive Impairment in Parkinson's Disease

BACKGROUND AND PURPOSE: The relationship between the side of motor symptoms and cognitive impairment has rarely been reported in Parkinson’s disease (PD). We aimed to estimate the influence of motor laterality on cognition in PD patients. METHODS: We enrolled 67 patients with PD, and they were divided into two groups according to side of symptom onset or predominant motor symptom presentation (right and left). Right-sided PD (RPD, 40) and left-sided PD (LPD, 27) patients underwent a neuropsychological battery exploring memory, attention/working memory, frontal/executive, visuospatial, and language functions. Student's t-test and Chi-square test have been carried out to compare the clinical and neuropsychological data between two groups. RESULTS: There were no significant differences in any neuropsychological test between the RPD and LPD groups, except for digit forward span test. RPD patients scored lower on the digit forward span test than LPD patients (5.43±9.49 vs. 6.15±1.38, p=0.045). CONCLUSIONS: RPD patients seem to experience more difficulties in attention and working memory than did LPD patients. The laterality of motor symptoms is not a major determinant for cognitive impairment in PD patients but, we should consider differences of cognitive deficits depending on the side of motor symptoms to treat patients with PD.