Prefrontal alterations in Parkinson's disease with levodopa-induced dyskinesia during fMRI motor task

Levodopa-induced dyskinesia represents disabling complication of long-term therapy with dopaminergic drugs in treating Parkinson's disease (PD). Recently, our group demonstrated that PD patients with levodopa-induced dyskinesia were characterized by abnormal volumetric changes in the inferior prefrontal gyrus. In this study, the functional relevance of this structural abnormality was explored using functional magnetic resonance imaging. Ten dyskinetic PD patients and 10 nondyskinetic PD patients were studied in the OFF phase with functional magnetic resonance imaging while performing externally and internally triggered visuomotor tasks. Although neither group demonstrated behavioral differences during execution of motor tasks, magnetic resonance imaging analysis detected significant changes in target cortical regions. In particular, PD patients with levodopa-induced dyskinesia showed significant overactivity in the supplementary motor area and underactivity in the right inferior prefrontal gyrus during execution of both tasks when compared with PD patients without levodopa-induced dyskinesia. Moreover, these prefrontal functional alterations were significantly correlated with Abnormal Involuntary Movement Scale scores. This functional magnetic resonance imaging study together with our previous volumetric findings highlights the role of the prefrontal cortex in the neuronal mechanisms of dyskinesia.