Transient hemiballism caused by a small lesion of the subthalamic nucleus.

ABSTRACT

Hemiballism is most commonly caused by ischemic stroke and most cases have a favorable prognosis. Lesions directly involving the subthalamic nucleus (STN) are the cause of a minority of cases but are usually associated with poor prognosis. We report two patients with a small STN lesion who presented with transient hemiballism. A small lesion confined to and only focally affecting the STN may cause hemiballism yet may have excellent outcome. Precise evaluation of the affected region with MRI is useful in predicting the prognosis.