This patient has Moyamoya disease, a rare idiopathic disorder characterized by progressive narrowing of the distal internal carotid arteries and their branches. It is typically seen in children, although rarely reported in adults. As the carotid artery is compromised, there is progressive enlargement of the collateral circulation, especially among the lenticulostriate vessels. This results in a characteristic angiographic picture of a blush or "puff of smoke" in the area of the lenticulostriate vessels. Moyamoya disease typically presents with recurrent, progressive cerebral infarctions; in some cases, the fragile collateral vessels can rupture resulting in intracerebral hemorrhage.