Clinical features of unilateral moyamoya disease.

Moyamoya disease is characterized by progressive occlusion of the internal carotid artery or its terminal branches, associated with formation of extensive collateral vessels (moyamoya vessels) at the base of the brain. Whether unilateral moyamoya disease, confirmed by typical angiographic evidence of moyamoya disease unilaterally and normal or equivocal findings contralaterally, is an early form of definite (bilateral) moyamoya disease remains controversial. The present study investigated the incidence and clinical features of unilateral moyamoya disease in a series of patients treated for moyamoya disease. Fifty-two patients were diagnosed with definite moyamoya disease and nine patients with unilateral moyamoya disease. Sex, age, signs at onset, neuroimaging findings, treatment, course of the disease, and family history of unilateral moyamoya disease were reviewed. Among the nine patients with unilateral moyamoya disease, there were twice as many females as males, and mean age at onset was 39.0 years. The clinical presentation was ischemic in three patients, bleeding in one, and asymptomatic in five. Two had familial moyamoya disease. Progression to bilateral lesions is known to occur in pediatric patients and patients with stenotic changes of the contralateral internal carotid artery bifurcation. Some unilateral cases are caused by the same genetic defects as definite cases, and others seem to be an unusual form of stenoocclusive process of cerebral arteries. Surgical treatment on the symptomatic side followed by close observation for bilateral involvement is recommended.