<unk>  is a<unk>  in which certain arteries in the brain are constricted. Blood flow is blocked by constriction and blood clots (thrombosis). A collateral circulation develops around the blocked vessels to compensate for the blockage, but the collateral vessels are small, weak, and prone to bleeding, aneurysm and thrombosis. On conventional angiography, these collateral vessels have the appearance of a "puff of smoke" (described as "もやもや<unk> " in Japanese). When<unk>  is diagnosed by itself, with no underlying correlational conditions, it is diagnosed as<unk> . This is also the case when the arterial constriction and collateral circulation are bilateral.<unk>  syndrome is unilateral arterial constriction, or occurs when one of the several specified conditions is also present. This may also be considered as<unk>  being secondary to the primary condition. Mainly, occlusion of the distal internal carotid artery occurs. On angiography, a "puff of smoke" appearance is seen, and the treatment of choice is surgical bypass.
Moyamoya disease
Vein of Galen aneurysmal malformations
Cerebral amyloid angiopathy
Cerebral arteriovenous malformation
Meningism
Giant cell arteritis
Hypertensive leukoencephalopathy
Chiari malformation