When Stroke Mimics a Subthalamic Lesion: An Unusual Presentation of Hemichorea-Hemiballismus.

Hemichorea-hemiballismus (HCHB) is a rare hyperkinetic movement disorder characterized by involuntary, irregular, and forceful flinging movements affecting one side of the body. It most often occurs as an uncommon manifestation of ischemic stroke. Traditionally linked to contralateral subthalamic nucleus lesions, recent reports have shown that infarcts in other regions, such as the striatum, thalamus, cortex, and subcortical white matter, can also produce this presentation. We report a case of acute-onset right-sided hemichorea in an elderly female, secondary to a lacunar infarct in the left centrum semiovale. The patient was initiated on antiplatelet therapy for secondary stroke prevention and tetrabenazine for the symptomatic management of involuntary movements. This case underscores the diverse anatomical substrates and the evolving understanding of the pathophysiological mechanisms underlying HCHB.