Causes of Stroke

Blockage of artery

• Clogging of arteries within the brain (e.g. lacunar stroke)
• Hardening of the arteries leading to the brain (e.g. carotid artery occlusion)
• Embolism to the brain from the heart or an artery

Rupture of an artery (i.e. hemorrhage)

• Cerebral hemorrhage (bleeding within the brain substance)
• Subarachnoid hemorrhage (bleeding between the brain and the inside of the skull)

What causes a stroke?
The blockage of an artery in the brain by a clot (thrombosis) is the most common cause of a stroke. The part of the brain that is supplied by the clotted blood vessel is then deprived of blood and oxygen. The cells of that part of the brain die as a result. Typically, a clot forms in a small blood vessel within the brain that has been previously narrowed due to the long-term, damaging effects of high blood pressure (hypertension) or diabetes. The resulting strokes are called lacunar strokes because they look like little lakes. In other situations, usually because of hardening of the arteries (atherosclerosis), a blood clot can obstruct a larger vessel going to the brain, such as the carotid artery in the neck.

Another type of stroke occurs when a blood clot or a piece of atherosclerotic plaque (cholesterol and calcium deposits on the wall of the inside of the heart or artery) breaks loose, travels through open arteries, and lodges in an artery of the brain. When this happens, the flow of oxygen-rich blood to the brain is blocked and a stroke occurs. This type of stroke is referred to as an embolic stroke. For example, a blood clot might originally form in the heart chamber as a result of an irregular heart rhythm, such as occurs in atrial fibrillation. Usually, these clots remain attached to the inner lining of the heart, but occasionally they can break off, travel through the blood stream, form a plug (embolism) in a brain artery, and cause a stroke. An embolism can also originate in a large artery (for example, the carotid artery, a major artery in the neck that supplies blood to the brain) and then travel downstream to clog a small artery within the brain.