[Two pediatric cases of moyamoya disease with progressive involvement from unilateral to bilateral].

Moyamoya disease is defined as having bilateral involvement of the internal carotid arteries. Two pediatric cases of moyamoya disease starting with unilateral involvement of the internal carotid artery are reported. In both cases angiographic findings at onset showed unilateral involvement. Hence, they were filed as a "probable" case according to the diagnostic criteria of the Japanese Cooperative Research Committee. The carotid angiograms on the other side showed totally normal findings. Clinical manifestation, EEG findings, angiographic findings, and PET findings in these cases were the same as those of definitive bilateral moyamoya disease. The only exception was the unilaterality of the findings. One to three years later the occlusive lesions became bilateral, and this met the criteria as a "definite" case. We consider that some of the cases of moyamoya disease actually start with unilateral lesion and develop into bilateral. Angiograms in "probable" cases should be carefully followed up to establish the disease entity of this lesion.