In outpatient clinics or wards, patients or family members are confused about sudden cerebrovascular diseases and often ask “Why do I have cerebral infarction? Only by understanding these can we prevent the onset and recurrence of cerebrovascular disease in a more targeted manner. In general, many systemic vascular lesions, local cerebrovascular lesions and hematologic lesions can lead to cerebrovascular disease, and the common causes are: 1. Vascular wall lesions: hypertensive atherosclerosis and vascular damage due to atherosclerosis are the most common; infectious or non-infectious vasculitis; vascular wall lesions caused by rheumatism, tuberculosis, parasites, connective tissue diseases (such as lupus erythematosus, polyarteritis nodosa), etc. Vascular developmental abnormalities, such as aneurysms, arteriovenous malformations, etc.; vascular wall injuries caused by cranial trauma, surgery, catheters, punctures, etc. 2, cardiac and hemodynamic changes: such as hypertension, hypotension, various cardiac disorders resulting in cardiac dysfunction, etc. (especially atrial fibrillation is likely to cause cerebral embolism). 3, blood composition changes and blood rheology abnormalities: various causes of increased blood viscosity, abnormal coagulation mechanism, etc. 4, other: extravascular factors such as cervical spondylosis, tumors and other compression caused by insufficient blood supply to the brain, various emboli formed outside the cranium (air,, fat, cancer cells, parasites, etc.). There are some patients with cerebrovascular disease whose etiology is unknown. Cerebrovascular disease is basically caused by the above four etiologies, and all patients can determine their own etiology according to their medical history and onset. In addition, epidemiological surveys have found that many factors are closely related to the development of cerebrovascular disease, which we will discuss with you in the next section.