Stroke is the Chinese medical term for acute cerebrovascular accident, including ischemic stroke (i.e., cerebral infarction) and hemorrhagic stroke (i.e., cerebral hemorrhage), both of which have a variety of causes. The causes of ischemic stroke mainly include: (1) atherosclerosis, the plaque formed by atherosclerosis is the main factor causing the narrowing of cerebral blood vessels, and a huge plaque can directly cause serious narrowing of the artery and then lead to occlusion. The plaque will lead to the destruction of the intima of the blood vessel, and then form platelet aggregation locally to form thrombus, or cause the rupture of the lipid inner core of the plaque, and these thrombi and dislodged plaques are carried away by the blood flow and blocked in the distal vessels, and then embolism is formed. (2) The embolism formed by atrial fibrillation is dislodged, atrial fibrillation refers to the irregular beating of atria, in this case, blood cannot completely flow from atria to ventricles, blood stagnation, leading to the formation of thrombus, thrombus can be dislodged to form embolism with blood flow forward, blocking small vessels, if blocked in the cerebral artery it forms cerebral infarction, this type of cerebral infarction is called cardiogenic embolism. (3) The blood itself can also lead to the formation of thrombus due to various factors such as autoimmunity, forming a stroke. In addition, there are other rare factors and unexplained causes of ischemic stroke. The causes of hemorrhagic stroke include: (1) hypertension combined with small arteriosclerosis, long-term hypertension makes the wall of small arteries less elastic, and blood vessels are prone to rupture and bleeding when blood pressure rises suddenly. (2) Other causes are less common than hypertension, including cerebral arteriovenous malformations, cerebral amyloid angiopathy, anomalous vascular network disease at the base of the brain, cerebral arteritis, hematologic disease, thrombolytic or anticoagulant therapy, etc. In summary, the causes of stroke are complex. The most common cause of ischemic stroke is atherosclerosis, and the most common cause of hemorrhagic stroke is hypertension.