Hemiballism after subthalamotomy in patients with Parkinson's disease: Report of 2 cases

The occurrence of persistent hemiballism after subthalamotomy for Parkinson's disease (PD) has not been described as frequently as mild or transient dyskinesia. We report on 2 patients with advanced PD who developed hemiballism and/or dyskinesia after subthalamotomy. One patient with a small lesion confined to the subthalamic nucleus (STN) developed persistent hemiballism; the other with a larger lesion involving the STN and also the zona incerta presented with a transient dyskinesia in a single limb. We conclude that a precise STN lesion might bear a potential risk of persistent hemiballism.