Levodopa-Resistant Freezing of Gait and Executive Dysfunction in Parkinson's Disease

We examined executive functioning in patients with Parkinson's disease exhibiting, or not, levodopa-resistant freezing of gait (L-FOG). 38 advanced-stage patients with L-FOG were identified in a consecutive series of 400 patients. They were matched with 38 patients without L-FOG. All patients underwent prospective evaluations of cognitive and motor functioning before subthalamic nucleus surgery, and 1 year after. A composite frontal score, a measure of executive functioning, was compared between the two groups. We also examined correlations between the frontal score and the score on the FOG item of the Unified Parkinson Disease Rating Scale II. Results show that after surgery, patients with L-FOG, as a group, were more impaired in executive functioning than control patients. However, individual data analysis showed preserved executive functions in 11 patients with L-FOG. In addition, there was no correlation between L-FOG severity and the degree of executive impairment. Therefore, frontal dysfunction may be one mechanism underlying L-FOG in a number of patients with Parkinson's disease. However, since some patients develop L-FOG despite the preservation of executive functions, lesions or dysfunction of other neuronal structures are likely to be involved.