A case of moyamoya disease with progressive involvement from unilateral to bilateral

A case of Moyamoya disease in a child starting with unilateral lesion and developing into bilateral involvement is reported. Angiographic findings at onset showed unilateral involvement, hence, it was filed as a "probable" case according to the diagnostic criteria of the Japanese Cooperative Research Committee. The carotid angiograms, on the other side were totally normal. Three years later the occlusive lesion became bilateral, to meet the criteria as a "definite" case. Clinical manifestations, angiograms, electroencephalograms, and positron emission tomograms in this case are presented, and the relation between the probable and definite cases is discussed.