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Hemiballismus (hemiballism) refers to a dramatic neurologic syndrome of wild, high amplitude, flinging, incessant movements that occur on one side of the body (Video). (1,2) It is classically due to infarction or hemorrhage in the region of the contralateral subthalamic nucleus (STN). Case series with modern neuroimaging have shown that only a minority of cases have lesions of the STN. Nonketotic hyperglycemia is also a common etiology. (3,4)

The movements of hemiballismus resemble those of chorea but are more pronounced. The clinical distinction between severe hemichorea and hemiballismus becomes arbitrary. Like chorea, hemiballistic movements are involuntary and purposeless, but they are much more rapid and forceful and involve the proximal portions of the extremities. When fully developed, there are continuous, violent, swinging, flinging, rolling, throwing, and flailing movements of the involved extremities. The movements are ceaseless during the waking state and disappear only with deep sleep. They are usually unilateral and involve one entire half of the body. Rarely, they are bilateral (biballismus or paraballismus) or involve a single extremity (monoballismus). The movements may spare the face and trunk. Hemiballismus is difficult to treat, incredibly disabling, and sometimes fatal because of exhaustion and inanition.

When hemiballismus results from a lesion of the contralateral STN, the damage to the STN removes its normal facilitation of the inhibitory effects of GPi/SNr. Without STN input, GPi/SNr inhibition of the motor thalamus decreases, causing increased thalamocortical activity and hyperkinesis.

Video legend. Hemiballismus. The movements were unremitting and medically intractable but resolved after pallidotomy, see Suarez et al (5)

Video courtesy of Stephen G. Reich, MD, Department of Neurology, University of Maryland.


1. Hawley, JS and Weiner, WJ. Hemiballismus: current concepts and review. Parkinsonism Relat Disord. 2012; 18:125-129.

2. Rocha Cabrero F, De Jesus O. Hemiballismus. 2021 Aug 30. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2022 Jan–.

3. Kataja Knight A, Magnusson P, Sjöholm Å. Hemiballismus in hyperglycemia. Clin Case Rep. 2021;9:e04343.

4. Ticona J, Zaccone V, Zaman U, et al. Hemichorea-Hemiballismus as an Unusual Presentation of Hyperosmolar Hyperglycemic Syndrome. Am J Med Case Rep. 2020;8:159-161.

5. Suarez JI, Metman LV, Reich SG, Dougherty PM, et al. Pallidotomy for hemiballismus: efficacy and characteristics of neuronal activity. Ann Neurol 1997;42:807-11).