Transient Ischemic Attack

Definition

A TIA is a brief interruption in the blood supply to the brain that leads to temporary neurological deficits (weakness, numbness, tingling).

Description

Each year, over tens of thousands of Americans - most of them in their 60s and 70s - have at least one transient ischemic attack (TIA), a brief "mini-stroke" that temporarily reduces the blood supply to a specific area of the brain for less than 24 hours.

Symptoms are often so fleeting that they are easily dismissed. But TIAs are a serious warning sign for underlying cardiovascular disease that can lead to stroke. Within 5 years of having a TIA, about one-third of patients go on to develop a full-blown stroke, which may cause death or permanently impair vision, speech and movement. And a study published in the Journal Neurology early in 2003 reported that approximately 11 percent of people who are diagnosed with a TIA in the emergency room will have a stroke within the next 90 days.

Clearly, identifying and treating those with TIAs can reduce the risk of stroke and preserve the quality of life of thousands of people each year.

Causes

TIAs are usually caused by atherosclerosis (hardening of the arteries), due to buildup of cholesterol and other materials along the arterial walls. These materials form deposits called plaques, which narrow the artery and lead to the formation of blood clots that can cause complete blockage.

There are two types of clots that can cause complete blockage. There are thrombosis (which form in the arteries leading to the brain); and embolic (which form in the heart or other arteries and travel to the brain).

TIAs may occur when an artery serving the brain becomes so obstructed that an adequate amount of blood cannot pass through, or when a portion of the blockage breaks away from the arterial wall and travels to the brain. The episode resolves when the body restores blood flow by releasing enzymes that reopen the artery.

Those at highest risk are men and women over age 60. The incidence is high among African-American men, people with diabetes (even when it is well controlled) or high blood pressure, and those with a family history of TIA or stroke. Heart disease (including angina, congestive heart failure, rhythm disturbances, and valve disorders) is also a risk factor.

Symptoms

Symptoms - which are similar to those of stroke (and many other conditions) - may include one or more of the following: weakness, tingling, or numbness in the arms and legs on one or both sides of the body; vision and language problems; confusion; vertigo (the sense that either you or the room is spinning); poor balance; lack of coordination or headache.

Onset is sudden, and duration is usually brief. While a few episodes may last up to 24 hours, most pass within a few minutes, and nearly all resolve within an hour.

Of TIAs that persist for more than an hour, about 80 to 90 percent develop into full-blown strokes (which, by definition, last for more than 24 hours), and permanent disability is possible.

The natural history of attacks is variable. Some patients will have a major stroke after only a few TIAs, while others may have frequent attacks for weeks or months without having a stroke. Attacks may occur intermittently over many years, or they may stop spontaneously.

TIAs are extremely important predictors of stroke; don't ignore them! If symptoms appear, CALL 911 to get medical help immediately.

Diagnosis

Diagnosis is based on the medical history and the physical examination, which may be normal. An electrocardiogram (EKG), chest x-ray, head CT (computed tomography) scan and an ultrasound study of the carotid arteries (in the neck) may be performed. An echocardiogram (ultrasound study of the heart) or MRI may also be recommended.

Treatment

Lifestyle changes are standard, whether the blockage is caused by plaque or clots. This includes improved exercise and dietary habits.

A surgical option is often considered if the carotid artery is more than 70 percent narrowed. This procedure is called carotid endarterectomy. This removes plaque from inside the artery. An incision is made in the neck to expose the artery, and the damaged segment is cleaned out and sutured back together to restore normal blood flow. The risk of serious complications is about 5 percent.

Medical treatment may include antiplatelet medications (drugs that discourage plaque formation by preventing platelets from sticking together) and, when necessary, anti-hypertensive (lowering blood pressure) medications. Aspirin is by far the most commonly used antiplatelet drug. A newer drug called ticlopidine is an alternative for patients who are unable to take aspirin because of side effects, but requires close monitoring.

Additional treatments may be considered, depending on the source and location of the blockage. If clotting in the heart is a problem (because of rhythm disturbance, valve disease, or congestive heart failure), the "blood thinner" drug warfarin (Coumadin) is often used.

Prevention

One way to prevent TIAs is to adopt the same strategies that reduce the likelihood of stroke. By far the most effective measure is to keep blood pressure controlled, since high blood pressure promotes atherosclerosis. Even pre-hypertension (above 120/80 but not in the defined range for hypertension) increases risk of TIA and stroke. Recommendations include trying to:

Eliminate smoking. Smokers are two times more likely to have a stroke than nonsmokers.
Drink alcohol only in moderation. Heavy alcohol use also increases stroke risk, perhaps by increasing the viscosity of blood and making it more prone to clotting.
Exercise regularly and maintain a healthy weight on a healthy low-fat diet. These measures will help maintain proper weight and place less strain on the circulatory system. Losing as little as 10 pounds with diet and exercise may lower your blood pressure and improve your cholesterol levels.
Eat plenty of fruits and vegetables, which contain such nutrients as potassium, folic acid and antioxidants that may protect against a TIA or a stroke.
Control blood glucose. This improves general health and reduces diabetes-associated complications.
Limit sodium. Avoiding salty foods and not adding salt to food may reduce your blood pressure.
Control your diabetes if you have it.