Moyamoya disease Suzuki grade by stage

Designed by 안덕현

Illustration included in the Moyamoya disease explanation booklet from Severance Hospital (Sinchon, Yongin).

Grade	explanation	Vascular findings	Key Features
Grade I	Early stage (Narrowing of ICA)	Onset of stenosis of the internal carotid artery (ICA)	- Absence of moyamoya vessels at the base of the brain - Early stage of reduced blood flow
Grade II	Initiation of moyamoya	ICA stenosis + small moyamoya vessel formation	- Appearance of circles of Willis (moyamoya vessels) - Dilation of microvessels around the basal ganglia
Grade III	Maximum Moyamoya (Intensification)	ICA almost occluded + abundant moyamoya vessels	- Maximal formation of moyamoya vessels - Reduced flow in major arteries
Grade IV	Minimization	Reduction of moyamoya vessels, dilation of external blood vessels	- Increased superficial collateral circulation (external collaterals) - Development of STA (superficial temporal artery) etc.
Grade V	Reduction	Moyamoya vessels are almost completely gone	- Complete ICA occlusion - Increased dependence on external circulation - Increased risk of decreased cerebral blood flow
Grade VI	Disappearance	Moyamoya vessels and ICA obliteration	- Loss of all basilar circulation - Dependence on external blood vessels - Highest risk of ischemia