Hemiballismus.

Hemiballism is a relatively rare hyperkinetic movement disorder characterized by involuntary, violent, coarse and wide-amplitude movements involving ipsilateral arm and leg. Although classically related to lesions in the subthalamic nucleus, in clinical-radiological series of hemiballism most patients had lesions outside this nucleus, involving mainly other basal ganglia structures. It has been suggested that abnormal neuronal firing patterns in the internal segment of the globus pallidus may be related to the pathogenesis of hemiballism. Stroke is the most common cause, but in recent years an increasing number of patients with hemiballism associated with nonketotic hyperglycemia or with complications of human immunodeficiency virus (HIV) infection have been reported. Contrarily to what was stated in older literature, hemiballism has, in general, a relatively good prognosis. Depending on the underlying causes, many patients may experience spontaneous improvements or remissions. Treatment should be directed to the cause of hemiballism. Symptomatic treatment includes the use of drugs, particularly blockers of striatal D2 dopamine receptors and tetrabenazine. Surgical treatment, especially pallidotomy, is a therapeutic option for the minority of patients with severe persistent disabling hemiballism.