Ischemic Stroke

An ischemic stroke occurs when a blood vessel that supplies the brain becomes blocked and impairs blood flow to part of the brain. The brain depends on its arteries to bring fresh blood from the heart and lungs. The blood carries oxygen and nutrients to the brain. If an artery is blocked, the brain cells are unable to make enough energy and eventually stop working. They begin to die within minutes from lack of oxygen and nutrients. The area of tissue death is called an infarct.

The underlying condition for this type of obstruction is the development of fatty deposits lining the vessel walls. This condition is called atherosclerosis. Another cause of stroke is blood clots in the heart, which can occur as a result of irregular heartbeat (such as atrial fibrillation), heart attack, or abnormalities of the heart valves. While these are the most common causes of ischemic stroke, there are many other possible causes. Examples include use of street drugs, traumatic injury to the blood vessels of the neck, or disorders of blood clotting.

Ischemic infarcts can develop in major blood vessels on the surface of the brain (called large-vessel infarcts) or in small blood vessels deep in the brain (called small-vessel infarcts). About 83 percent of strokes fall into the category of ischemic infarcts. Types of ischemic stroke include embolic infarct, thrombotic infarct, and lacunar infarct. Infarct of undetermined cause accounts for approximately 30% of cases of ischemic stroke.

Embolic stroke

Embolic strokes are usually caused by an embolus i.e. a blood clot that forms elsewhere in the body and travels through the bloodstream to the brain. . Once in the brain, the clot eventually travels to a blood vessel small enough to block its passage. The clot lodges there, blocking the blood vessel and causing a stroke.

Embolic strokes often result from heart disease or heart surgery and occur rapidly and without any warning signs. About 15 percent of embolic strokes occur in people with atrial fibrillation.

Thrombotic stroke

Thrombotic strokes are strokes caused by a thrombus i.e. a blood clot that develops in the arteries supplying blood to the brain. This type of stroke is usually seen in older persons, especially those with high-cholesterol levels and atherosclerosis. Blood-clot strokes are a result of unhealthy blood vessels clogged with a buildup of fatty deposits and cholesterol.

Sometimes, symptoms of a thrombotic stroke can occur suddenly and often during sleep or in the early morning. At other times, it may occur gradually over a period of hours or even days. This is called a stroke-in-evolution.

Thrombotic strokes may be preceded by one or more mini-strokes called transient ischemic attacks, or TIAs. In a TIA; arterial blockage in the brain occurs briefly and resolves on its own, without causing tissue death. Approximately 10% of ischemic strokes are preceded by a TIA, and about 40% of patients who experience a TIA will have a stroke.

Lacunar infarct

Another type of ischemic stroke that occurs in the small blood vessels in the brain is called a lacunar infarct. The word lacunar comes from the Latin word meaning "hole" or "cavity." Lacunar infarctions (approx. 20% of cases) usually occur as a result of arterial blockage caused in people who have diabetes or hypertension. This type of stroke has the best prognosis.