We report three patients with hemichorea who were found to have contralateral atherosclerotic carotid artery stenosis. Their details are compared in the table. All patients had carotid duplex ultrasonography because they exhibited neurologic signs or symptoms suggestive of cerebrovascular ischemia in addition to chorea.Patient A developed right hemichorea; 9 months later she experienced three episodes of right limb weakness and speech disorder lasting 5 minutes, suggestive of transient ischemia. The severity of chorea increased and it mildly affected the left side. Neurologic examination revealed predominantly rightsided chorea and mild orofacial dyskinesia without other neurologic signs. The following blood tests were normal: full blood count, inflammatory markers, coagulation studies, renal, glucose, bone, liver, and thyroid biochemistry, immunoglobulin electrophoresis, anticardiolipin antibodies, and antinuclear antibodies screen (including extractable nuclear antigens). CT of the head was normal. Carotid duplex ultrasonography revealed 90% stenosis in the left internal carotid artery.Patient B developed right hemichorea and 3 months later expressive dysphasia and right facial and hand weakness; this precipitated admission. In addition to chorea, there was right visual inattention and upper motor neuron weakness affecting the right face and hand with normal reflexes and plantar responses. The same blood tests as for patient A were normal; in addition, treponemal serology was consistent with past infection. MRI of the brain showed a left-sided parietal lobe infarct which was limited to the gray matter of the posterior parietal lobe suggestive of watershed infarction. Carotid duplex ultrasonography revealed 90% stenosis in the left internal carotid artery.Patient C presented with right-sided upper limb cortical sensory loss (dysgraphesthesia, astereognosis, and joint position sense loss) and within a month had developed right hemichorea. A blood test panel as described above was normal. In addition, the following investigations were normal or negative: treponemal serology, copper, ceruloplasmin, antistreptolysin titers, rheumatoid factor, and anticytoplasmic nuclear antibodies. CSF examination was performed: cell count, protein, and glucose were within normal limits, herpes simplex virus PCR was negative, and oligoclonal bands were absent. MRI of the brain showed a left-sided parietal lobe infarct which involved the post-central gyrus and the underlying parietal white matter. Carotid duplex ultrasonography revealed 90% stenosis in the left internal carotid artery.All three patients proceeded to carotid endarterectomy with complete resolution of the chorea. Neurologic signs in patient B resolved, but right-sided cortical sensory loss persisted in patient C. DISCUSSION New onset chorea frequently triggers referral to neurology departments. Its several causes include metabolic, vascular, structural, autoimmune, and genetic. 1 Diagnostic workup therefore usually includes a detailed family and drug history, a general...