The stages of basal Moyamoya vessels
| Stages | Angiographic Findings |
|---|---|
| I | No Moyamoya vessels were seen |
| II | Moyamoya vessels were localized in the area around the ICA bifurcation, and each vessel was fine and had little contrast |
| III | Moyamoya vessels had intermediate extension and thickness |
| IV | Moyamoya vessels extended a great deal, and each one was thick and strongly opacified |
Note:—ICA indicates internal carotid artery.