Hemiballismus.

Hemiballismus is the most dramatic movement disorder seen in clinical practice. Its emergence points to a structural lesion or metabolic dysfunction in the region of the subthalamic nucleus, its afferent or efferent pathways, or interconnected deep brain nuclei, usually on the side contralateral to the movements. Any focal process may be to blame, but elderly sufferers generally have had vascular events, whereas the etiology is infectious or inflammatory in younger patients. Severe nonketotic hyperglycemia is another important cause of hemiballismus in the elderly. Hemiballismus patients require treatment both for the underlying etiology of the movement and for the movements themselves. There are no large controlled clinical trials to guide anti-ballismus therapy. However, dopamine receptor blocking agents have an established track record in suppressing choreic and ballistic movements, and are first-line agents for acute treatment. Standard neuroleptics such as haloperidol and perphenazine are started at low doses and titrated as tolerated until the movements are controlled. Atypical antipsychotics such as risperidone and clozapine have been used in small series and may have a reduced risk of extrapyramidal side effects. Catecholamine-depleting agents such as reserpine and tetrabenazine may be considered when long-term therapy is required. Other pharmacologic agents have met with varying success. The course of hemiballismus may be complicated by exhaustion, injury, or metabolic disorders, but with good supportive care, acute survival is good, and long-term survival reflects the prognosis of the underlying etiology. In time, the ballistic movements themselves tend to subside allowing withdrawal of drugs in many cases. When movements persist, stereotactic functional neurosurgical procedures may be considered in good surgical candidates.