Stroke

What is stroke?

Stroke, also called brain attack, occurs when blood flow to the brain is disrupted. Disruption in blood flow is caused when either a blood clot blocks one of the vital blood vessels in the brain (ischemic stroke), or when a blood vessel in the brain bursts, spilling blood into surrounding tissues (hemorrhagic stroke).

The brain needs a constant supply of oxygen and nutrients in order to function. Even a brief interruption in blood supply can cause problems. Brain cells begin to die after just a few minutes without blood or oxygen. The area of dead cells in tissues is called an infarct. Due to both the physical and chemical changes that occur in the brain with stroke, damage can continue to occur for several days. This is called a stroke-in-evolution.

A loss of brain function occurs with brain cell death. This may include impaired ability with movement, speech, thinking and memory, bowel and bladder, eating, emotional control, and other vital body functions. Recovery from stroke and the specific ability affected depends on the size and location of the stroke. A small stroke may result in problems such as weakness in an arm or leg. Larger strokes may cause paralysis (inability to move part of the body), loss of speech, or even death.

According to the National Stroke Association (NSA), it is important to learn the three R's of stroke:

• Reduce the risk.

• Recognize the symptoms.

• Respond by calling 911 (or your local ambulance service).

Stroke is an emergency and should be treated as such. The greatest chance for recovery from stroke occurs when emergency treatment is started immediately.

Stroke is the fourth leading cause of death, ranking behind diseases of the heart, lungs, and all forms of cancer. According to the NSA, strokes kill more than 137,000 Americans each year.

What are the different types of stroke?

Strokes can be classified into two main categories:

• 87 percent are ischemic strokes. These strokes are caused by blockage of an artery.

• 13 percent are hemorrhagic strokes. These strokes caused by bleeding.

What is an ischemic stroke?

An ischemic stroke occurs when a blood vessel that supplies the brain becomes blocked or "clogged" and impairs blood flow to part of the brain. The brain cells and tissues begin to die within minutes from lack of oxygen and nutrients. The area of tissue death is called an infarct. About 87 percent of strokes fall into this category. Ischemic strokes are further divided into two groups, including the following:

• Thrombotic strokes. These strokes are caused by a blood clot that develops in the blood vessels inside the brain.

• Embolic strokes. These strokes are caused by a blood clot or plaque debris that develops elsewhere in the body and then travels to one of the blood vessels in the brain via the bloodstream.

What is a thrombotic stroke?

Thrombotic strokes are strokes caused by a thrombus (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 (a buildup of fat and lipids inside the walls of blood vessels).

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. TIAs may last from a few minutes to a few days and are often a warning sign that a stroke may occur. Although usually mild and transient, the symptoms caused by a TIA are similar to those caused by a stroke.

Another type of 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 are often found in people who have diabetes or hypertension (high blood pressure).

What is an embolic stroke?

Embolic strokes are usually caused by an embolus (a blood clot that forms elsewhere in the body and travels through the bloodstream to the brain). 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, a type of abnormal heart rhythm in which the upper chambers of the heart do not beat effectively.