Moyamoya disease (MMD), also known as spontaneous basilar artery ring occlusion, is a disease characterized by slow intimal thickening of the internal carotid artery (ICA) and the anterior cerebral artery (ACA), middle cerebral artery (MCA), and compensatory dilation of the middle cerebral artery (MCA). It is a chronic cerebrovascular disease of unknown etiology, characterized by a slow thickening of the intima of the arteries at the beginning of the ICA and the anterior cerebral artery (ACA) and middle cerebral artery (MCA), a gradual narrowing of the arterial lumen to the point of occlusion, and a compensatory dilation of the underlying perforating arteries.
Once diagnosed with MMD, even asymptomatic MMD should be treated promptly with systematic and scientific surgical treatment, and the majority of patients with MMD improve their symptoms with effective treatment.