Caudate head hemorrhage caused by asymptomatic occlusion of the middle cerebral artery.

Two nonhypertensive adult patients with asymptomatic occlusion of the middle cerebral artery, in whom caudate head hemorrhage occurred ipsilateral to the occlusive lesion, are described. The mechanism of this hemorrhage is surmised to be identical to that of moyamoya disease: a rupture of the dilated, fragile lenticulostriate artery, which evolved as a collateral channel in response to chronic cerebral ischemia.