SIDE OF ONSET OF MOTOR SYMPTOMS INFLUENCES COGNITION IN PARKINSONS-DISEASE

Studies attempting to relate cognitive impairment to asymmetry of moto r symptoms in Parkinson's disease (PD) have found contradictory result s. We examined 88 patients with unilateral onset of idiopathic PD who underwent a comprehensive neuropsychological assessment, including lan guage, visuospatial abilities, abstraction and reasoning, attention an d mental tracking, set shifting, and memory. Patients whose motor sign s began on the left side of the body consistently performed more poorl y on the battery of cognitive measures than did patients with right-si de onset. Significant differences were found on immediate and delayed verbal recall, word retrieval, semantic verbal fluency, visuospatial a nalysis, abstract reasoning, attention span, and mental tracking. Thes e differences could not be attributed to differences in the overall se verity of motor symptoms at the time of cognitive assessment, or the c urrent pattern of motor asymmetry. This finding suggests that damage t o right-hemisphere dopamine systems plays a disproportionately greater role in PD-related cognitive decline than a presumably comparable lef t-hemisphere dopamine depletion.