We reported a 12-year-old boy with unilateral
moyamoya disease whose initial and predominant manifestation was hemichorea. Neurological examinations revealed
chorea in his left upper extremity and
muscle hypotonia in his left upper and lower extremities. Cranial MRI showed moyamoya vessels only in the right basal ganglia and
infarction in the white matter of the right frontal lobe. Right carotid angiography revealed
stenosis in the distal part of internal carotid artery, and in the proximal part of anterior and middle cerebral arteries with moyamoya vessels. Left carotid angiography showed normal findings. He was diagnosed as a suspected case of
moyamoya disease (unilateral
moyamoya disease) according to the diagnostic criteria proposed by the Research Committee on
Moyamoya Disease of the Ministry of Health and Welfare of Japan. His
chorea responded to
haloperidol but encephalo-duro-arterio-synangiosis on the right side improved all symptoms.
Chorea occurs in some patients with
moyamoya disease. Hypofunction of the striatal indirect pathway is suggested as the cause of
chorea. In this case an ischemic lesion in the right striatum may have caused hypofunction of the pathway and developed
chorea and
hypotonia.