Moyamoya (spontaneous occlusion of the arterial ring of Willis) is a non-atherosclerotic progressive stenosis-occlusive arteriopathy that most commonly involves the intracranial segment of the internal carotid artery and the proximal segments of the MCA and ACA arteries, and may also involve the posterior circulation. The spontaneous occlusion of large intracranial vessels is usually accompanied by the presence of plexiform microscopic collateral vessels at the base of the skull. moyamoya is a Japanese term meaning puff of smoke or ambiguity, which not only describes the plexiform collateral circulation but also indicates that the etiology of this syndrome is unclear and still poorly elucidated. The term smoldering disease still refers to those intracranial vascular changes that are primary and truly idiopathic, whereas smoldering syndrome (secondary smoldering disease, smoldering phenomenon, symptomatic smoldering disease, smoldering-like disease, or smoldering disease-like vascular changes) is used to describe those intracranial vascular changes caused by other diseases such as cranial radiation therapy or neurofibrillary disease type I. I. Epidemiology Race is the main factor, with the highest incidence in Asian, especially East Asian, smog patients (Japan, Korea, China, etc.) MMD occurs in children aged 5 to 9 years and adults aged 45 to 49 years. The former is dominated by ischemic manifestations and the latter by hemorrhagic manifestations, but the pathological changes are both decreases in cerebral blood flow. Diagnosis of smog 1. Diagnostic criteria a. Cerebral angiography should show the following: (1) Stenosis or occlusion of the terminal internal carotid artery and/or proximal segments of the anterior and middle cerebral arteries. (2) An abnormal vascular network is visible near the stenosis or occlusion lesion (3) This performance is present bilaterally. b. Conventional cerebral angiography is not required if MRI and MRA can clearly confirm the following manifestations (1) Stenosis or occlusion of the terminal internal carotid artery or (and) proximal segment of the anterior cerebral artery and middle cerebral artery (2) MRA shows an abnormal vascular network in the basal ganglia area, and 2 places are seen in the ipsilateral basal ganglia area on MRI (2) MRA shows an abnormal vascular network in the basal ganglia region, and MRI shows two obvious blood flow voids in the basal ganglia region on the same side. (3) Both of these manifestations are present bilaterally. c. Exclude other causes, because the etiology of this disease is unclear, related cerebrovascular diseases need to be excluded, including the following diseases, but not limited to the following: (1) atherosclerosis (2) autoimmune diseases (3) meningitis (4) brain tumor (5) Down syndrome (6) neurofibromatosis type 1 (7) traumatic brain injury (8) after head radiotherapy. d. For (2) Narrowing or occlusion of the main arterial branches that make up the ring of Willis, associated with thickening of the fibroblasts of the intima, flexion of the internal elastic lamina, and thinning of the mesentery (3) Numerous small arteries (penetrating branches) or anastomosing branches are seen around the ring of Willis (4) Small vessel formation in the soft meninges (4) Small vessels are seen in the soft meninges to form a vascular network. 2. Diagnosis 1. Confirmed cases, meeting all the indices in item a or all the indices in items b and c, but in children, cases meeting items (1) and (2) in item a or (1) and (2) in item b on one side and showing stenosis of the end of the internal carotid artery on the opposite side are also confirmed cases. 2. Suspected cases. (1) and (2) of item a or (1) and (2) of item b and C (unilateral lesion) are met. (Figure 1: CTA shows occlusion of normal vascular structures of the anterior cerebral artery, middle cerebral artery, and posterior cerebral artery disappearing, and abnormal vascular network forming around the lesion) Showing right internal carotid arteriogram: stenosis at the bifurcation of the internal carotid artery, vascular occlusion of the anterior cerebral artery and middle cerebral artery, disappearance of normal vascular pattern, and formation of abnormal vascular network) Showing left internal arteriogram: stenosis at the bifurcation of the internal carotid artery, occlusion of the anterior cerebral artery and (Showing right vertebral arteriogram: stenosis of basilar artery segment, not yet occluded, blurred normal vessels of posterior cerebral artery, formation of peripheral smoke vessels)