Hemiballismus
（重定向自Hemiballism）
![Hyperglycemia-induced involuntary movements (in this case, not hemiballismus, but hemichorea (chorea of one side of the body) and bilateral dystonia) in a 62-year-old Japanese woman with type 1 diabetes.](/Images/godic/202501/17/-Hemichorea_and_dystonia.ogv3105.jpg")
Hemiballismus, formerly called ballism, is a very rare movement disorder, caused in most cases by a decrease in activity of the subthalamic nucleus of the basal ganglia, resulting in the appearance of flailing, ballistic, undesired movements of the limbs. It can also appear rarely due to certain metabolic abnormalities. It is a rare movement disorder, being 500 times rarer than Parkinson's disease. Hemiballismus can cause significant disability. Symptoms can decrease during sleep.