Cerebrovascular lesions, systemic vascular lesions and hematologic diseases are all related to the occurrence of CVD (cerebrovascular disease). Most of them are brain manifestations of systemic vascular diseases such as atherosclerosis, and only a few of them are cerebrovascular lesions such as aneurysm, vascular malformation or trauma. The etiology can be single or multiple, and the common causes are: 1. Vascular wall lesions ① cerebral atherosclerosis is the most common, and the main type is atherosclerosis, mainly involving large and medium diameter arteries, and hypertensive small arteriosclerosis; ② followed by arteritis, including infectious and non-infectious, the former such as rheumatism, tuberculosis, syphilis, leptospirosis and parasitic arteritis, and the latter such as (3) congenital developmental abnormalities such as intracranial aneurysm, arteriovenous malformation and congenital stenosis; (4) vascular injuries can be seen in direct injuries such as cranial injury, cranial surgery, insertion of catheters, puncture, and vascular lesions caused by drugs, poisons, malignant tumors, etc.; (5) emboli from the heart and large arteries can block cerebral arterial blood circulation. 2, heart disease and hemodynamic changes such as hypertension, hypotension, rapid fluctuations in blood pressure, rheumatic heart disease, cardiomyopathy, arrhythmia and cardiac dysfunction, especially atrial fibrillation is prone to cardiogenic embolism, leading to stroke 3, blood components and blood rheology changes including various abnormalities in coagulation mechanisms and hyperviscosity, such as erythrocytosis, hyperfibrinogenemia, severe anemia, leukemia and Diffuse intravascular coagulation, etc., as well as the application of anticoagulants, taking contraceptives, etc. Metabolic diseases such as diabetes can promote hyperlipidemia and atherosclerosis, etc. 4, other etiologies include emboli such as air, fat, cancer cells and parasites, cerebral vasospasm, trauma, etc., drug allergies, poisoning contribute to blood clotting and vascular changes.