Obsessive-compulsive symptoms and motor asymmetries in Parkinson’s disease

Accumulating evidence suggests that basal ganglia dysfunction is related to obsessive-compulsive symptomatology (OCS). However, conflicting findings have been reported regarding the lateralization of this dysfunction. We administered the Leyton Obsessional Inventory to examine the relationship between OCS and lateralization of motor symptoms in 30 patients with idiopathic Parkinson's disease (PD). Severity of left-, but not right-sided motor symptoms was a reliable predictor of overall severity of OCS. Specifically, highly significant correlations were noted between severity of motor symptoms on the left side of the body and higher degree of overconscientiousness, repetition, disturbing thoughts, and obsessions with cleanliness. Only the order/routine Leyton subscale correlated with right-sided motor symptoms. These findings suggest that OCS in PD may reflect relatively greater dopamine deficiency in right basal ganglia.