Classification of the severity of steno-occlusive change in the internal carotid artery circulation
| ICA Stage | Angiographic Description |
|---|---|
| I | Narrowing of carotid bifurcation |
| II | Dilation of ACA and MCA with appearance of ICA moyamoya |
| III | Partial disappearance of ACA and MCA with intensification of moyamoya |
| IV | Advanced stenoocclusive changes in ICA (ACA and MCA are traced very dimly or in a completely different shape) with small amount of ICA moyamoya |
| V | Absence of the ACA and MCA with further reduction of moyamoya |
| VI | Blood supply only from the ECA with almost complete disappearance of ICA moyamoya |
Note.—Classification is according to Mugikura et al (12). ACA indicates anterior cerebral artery; MCA, middle cerebral artery; ICA, internal carotid artery; ECA, external carotid artery.