[A case of unilateral moyamoya disease presenting with hemichorea].

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.