There are two main types of stroke, depending on the cause of the interruption of the blood supply. If it is caused by a blocked blood vessel, it is called an ischemic stroke; if it is caused by a ruptured blood vessel, it is called a cerebral hemorrhage. Each type of stroke has a different treatment, so it is very important for doctors to quickly determine the type and location of the stroke. Ischemic stroke Ischemic stroke, also called cerebral infarction, is caused by a blockage of a blood vessel that causes localized ischemia in the brain tissue; it also includes thrombotic stroke and embolic stroke. Thrombotic stroke, also known as cerebral thrombosis, is the most common type of stroke. In this type, a blood clot (thrombus) forms in an artery in the brain, blocking blood flow, or sometimes in a blood vessel in the neck (carotid or vertebral artery) that carries blood to the brain. Clots are most likely to form in those arteries that have atherosclerotic damage. Atherosclerosis is the accumulation of fatty plaques in the arterial walls and is most likely to occur in middle-aged and elderly people with high blood pressure, high blood cholesterol, diabetes and a history of smoking and alcohol consumption. It can cause complete blockage of the artery. Unlike cerebral thrombosis, however, clots do not form directly in the cerebral arteries but originate in other parts of the arteries, most commonly in the inner wall or valves of the heart. When a clot (embolus) from another part of the body comes off, the embolus is carried to the brain with the blood flow. As the branches of the arteries become thinner and thinner, once the embolus reaches an area where it cannot pass, it stays there and blocks the blood vessel, and this sudden blockage of the blood vessel is called an embolism. You may have heard the term cerebral infarction, which is associated with both of the above stroke types. An infarction is caused by necrosis (or death of tissue) in an area when a blood clot forms or an embolus blocks a blood vessel. Thrombotic stroke and embolic stroke are the two types of cerebral infarction. There is another type of stroke called lacunar cerebral infarction, which occurs when a relatively small artery deep in the brain is blocked. It causes less damage than the first two types of strokes because it affects a smaller area and most of the injury sites are not very important. Hemorrhagic stroke Hemorrhagic stroke, also called cerebral hemorrhage, is another major type of stroke. It occurs when a blood vessel in or near the brain ruptures and blood flows into the brain or the area around the brain. When this happens, the cells nourished by the ruptured artery do not receive a normal supply of oxygen and nutrients, resulting in loss of function. The flowing blood also causes damage to the surrounding brain tissue by compressing it. In addition, blood flowing from the ruptured artery can quickly form clots that replace normal brain tissue and impair brain function. Brain hemorrhage is most often seen in those with both atherosclerosis and hypertension. Cerebral aneurysms and arteriovenous malformations are the most common causes of brain hemorrhage. There are also two main types of brain hemorrhage, depending on the site of the hemorrhage: subarachnoid hemorrhage and intracerebral hemorrhage. Subarachnoid hemorrhage is bleeding in the space between the brain tissue and the skull. Intracerebral hemorrhage is a hemorrhage caused by a ruptured artery inside the brain parenchyma, with the hemorrhage focus surrounded by brain tissue. Aneurysms and AVMs Cerebral hemorrhage is usually caused by the rupture of an aneurysm or arteriovenous malformation (AVM). An aneurysm is an abnormal swelling of an artery in the brain. In an aneurysm, the wall of the artery is defective, and under the influence of the strong impact of the arterial blood flow, the artery will swell and expand over the years, eventually leading to rupture. An AVM is a cluster of abnormal arteries and veins tangled together to form a hairy mass of blood vessels. It is congenital and may grow in size with age, and may cause other symptoms before it ruptures, including seizures, progressive neurological disease, and severe headaches that are not treated with medication.