There are two major types of stroke: hemorrhagic (bleeding) and ischemic (lack of blood due to a clot). Ischemic strokes are more common.

There are 4 main causes of ischemic stroke:

• Atherothrobotic: due to hardening of the arteries in the neck, or less often of the vessel within the brain. When the neck arteries are narrowed substantially, treatment is often surgical; in milder cases Aspirin and risk factor reduction is the treatment.
• Embolic: Due to clots formed elsewhere in the body (usually in the heart, that then travel to the brain. The causes may include atrial fibrillation (an abnormal heart rhythm), diseases of the heart valves, heart attacks or heart failure, or congenital problems with the heart such as patent foramen ovale. This type of stroke is usually treated with warfarin.
• Lacunar: Due to occlusion of tiny blood vessels within the brain, usually from high blood pressure or diabetes. Aspirin and risk factor reduction, especially careful control of high blood pressure and diabetes is the treatment.
• “Other”: Due to abnormal clotting of the blood from a variety of causes or spasm of vessels (unusual). This type of stroke is more common in young patients (< age 45 and no risk factors) types of stroke.

There are two main types of hemorrhagic stroke. The chance of death from these types of stroke is greater than with ischemic strokes:

• Intracerebral hemorrhage: usually due to very high blood pressure causing rupture of small vessels, less often from blood vessel abnormalities. Treatment is to control high blood pressure. Although a blood clot forms, surgery is usually not indicated unless the bleeding is in a part of the brain called the cerebellum.
• Subarachnoid hemorrhage: usually due to a burst aneurysm in the brain or brain vascular malformations. This condition is very dangerous and emergency care and often brain surgery is required.