Table III.

Angiographic ICA staging system modified by Mugikura et al (36).

ICA stage	Angiographic findings
I	Mild to moderate stenosis around carotid bifurcation with absent or slightly developed ICA moyamoya: Almost the entire ACA and MCA branches are opacified in antegrade fashion
II	Severe stenosis around carotid bifurcation or occlusion of either of proximal ACA or MCA with well-developed ICA moyamoya: The ACA and/or MCA branches are clearly defective, but at least several of the ACA or MCA branches remain opacified in antegrade fashion
III	Occlusion of the proximal ACA and/or MCA with well-developed ICA moyamoya: Only a few of the ACA and/or MCA branches are faintly opacified in antegrade fashion through the meshwork of ICA moyamoya
IV	Complete occlusion of the proximal ACA and MCA with absent or small amount of ICA moyamoya: No opacification of either ACA or MCA branches in antegrade fashion

ACA, anterior cerebral artery; MCA, middle cerebral artery; ICA, internal carotid artery.