Hemiballism occurs following damage to the subthalamic nucleus. Ballisic movements are involuntary, sudden, jerking movements which occur contralateral to the side of the lesion. The ballisic movements primarily affect the proximal limb musculature whilst the distal muscles may display more choreiform-like movements

Symptoms may decrease whilst the patient is asleep.

Antidopaminergic agents (e.g. Haloperidol) are the mainstay of treatment