Transient ischemic attacks

Definition

Transient ischemic attacks or TIAs are brief stroke-like episodes, sometimes called mini-strokes or transient stroke , that occur when a blood clot temporarily blocks an artery and prevents blood from flowing normally in the brain.

Description

A transient ischemic attack (TIA) is not an actual stroke but gives the individual a serious warning of increased risk for stroke. It should be considered an emergency and requires an immediate visit to a physician or an emergency department. Although a TIA cannot predict when a stroke will occur, clinical evidence from thousands of cases shows that strokes usually follow TIAs within one year, and sometimes as soon as 24 to 48 hours. TIAs happen when a blood clot blocks an artery and interrupts blood flow to a specific part of the brain, producing transient stroke-like symptoms such as numbness in the face or limbs, confusion, difficulty speaking, vision problems, dizziness or difficulty maintaining balance and sudden severe headache. The blocked artery is usually between the heart and the brain, often in the carotid artery in the neck, the vertebral arteries or within the brain itself. Although symptoms of stroke and TIA are similar, the difference between a stroke and a TIA is that no permanent damage to the brain usually occurs as a result of TIA. However, TIA is a critical indication that stroke is likely to occur and physicians pay strict attention to TIAs, seeking to prevent stroke, which can lead to permanent disability or death . Immediate diagnosis is needed so that treatment of TIA can be provided as quickly as possible to prevent or reduce blood clot formation and reduce the threat of stroke.

Demographics

Between 200,000 and 500,000 individuals experience TIAs every year in the United States; the majority are over age 65 and it is rare for anyone 45 or younger to have TIA. Among emergency room patients with TIAs, 25% have another adverse event such as heart attack or stroke within 90 days of the original emergency room visit, and 10% of these are strokes that occur with 48 hours after the visit. Risk for TIA parallels risk for stroke. The National Stroke Association reports that two-thirds of stroke victims are over age 65, with risk doubling in each 10 years over age 55. Men are at greater risk than women and African-Americans at greater risk than other racial groups. Stroke is the third leading cause of death after heart disease and cancer . Nearly 700,000 strokes are recorded each year in the United States; most individuals are disabled by the stroke and about 150,000 will die.

Causes and symptoms

The most frequent risk factors for TIA and stroke are high blood pressure (hypertension ), high cholesterol , heart disease, carotid artery disease, diabetes, cigarette smoking and excess alcohol consumption. Diabetes increases risk because of associated circulatory problems . Individuals with high blood pressure are at four to six times greater risk for TIA and stroke. Common to most of these health and lifestyle factors, as well as normal aging, is damage to arteries and the resultant narrowing from buildup of fatty deposits (plaque) on artery walls, making them harder and thicker (atherosclerosis ). In carotid artery disease, plaque builds up in either one or both of the carotid arteries on each side of the neck, narrowing them significantly (between 50 and 70% blockage), a condition called stenosis. Narrowing of arteries increases blood pressure and reduces blood circulation throughout the body, creating a potentially dangerous condition that robs cells and organs of necessary oxygen (ischemia ), which can ultimately result in heart attack or stroke. Blockage of an important artery by accumulated deposits or a blood clot can prevent blood and oxygen from flowing to the heart or the brain. Reduced blood flow to the heart can result in cardiac ischemia and heart attack. Lack of blood flow to the brain can precipitate TIA and ischemic stroke.

Symptoms of TIA appear suddenly and are similar to those of stroke but are transient, usually lasting only minutes. Symptoms are derived from lack of oxygen and blood flow to a part of the brain and are therefore typical of nervous system disorders (neurological deficit). TIA must be considered if the individual experiences numbness or weakness on one side of the face, or in an arm or leg on one side. Loss of ability to speak or think clearly, slurring words, feeling confused or having trouble understanding what another person is saying can be signs of TIA. Vision may be disturbed in one eye or both. Sudden severe headache may be the first symptom or may accompany other symptoms. Dizziness and loss of balance or unsteady walking may also indicate TIA. Symptoms can last up to an hour but more typically will pass within five minutes or so; in some cases, certain symptoms may continue into the next day, diminishing gradually. Because the individual or caretaker can not determine if the symptoms are TIA or stroke, immediate emergency attention is needed to diagnose the condition and to obtain fast, appropriate treatment.

Diagnosis

Emergency evaluation of possible TIA should ideally be conducted within 180 minutes of the first appearance of symptoms. The physician will immediately examine the patient for signs of weakness in the face, arms and legs and note any altered speech or presence of confusion. Vital signs such as blood pressure and heart rate will be monitored and an electrocardiogram (ECG) will be done to evaluate heart function. Family history of stroke may be noted. The individual's recent history of symptoms and current and prior diseases or conditions will be reviewed as quickly as possible while beginning laboratory testing to determine if TIA or pending stroke will require immediate medication to reduce risk of blood clots . Diagnostic laboratory tests will include a complete blood count , platelet count, and coagulation tests (prothrombin time, partial thromboplastin time) to determine likelihood of clotting abnormalities and clot formation. Serum electrolytes (sodium , potassium and chloride) will be done to evaluate presence of vascular or heart abnormalities, and blood glucose will be done to determine blood sugar abnormalities, which can be confused with TIA. Computed tomography (CT) of the head may be done to determine if brain hemorrhage or tumor may be present, which can mimic TIA; prior stroke can also be identified with CT scans . However, magnetic resonance imaging (MRI) may also be performed to examine brain tissue more closely for specific damage; MRI is considered the most accurate imaging technique for identifying TIA.

Treatment

Immediate treatment for TIA will focus on dissolving blood clots or preventing clot formation. Drug therapy with appropriate anticoagulant drugs will typically be given intravenously and may include tissue-type plasminogen activator (tPA) in some individuals for whom it is appropriate. A drug that reduces platelet aggregation, a mechanism involved in clot formation, may be given (antiplatelet therapy) or other types of anticoagulant therapy, including heparin or warfarin, depending on the health status of the individual and presence of any concomitant disease. Individuals are monitored extremely closely while receiving drug therapy for TIA, drawing blood

QUESTIONS TO ASK YOUR DOCTOR

• Have I had a TIA or stroke
• If this is a TIA, what must I do to prevent having a stroke?
• How can I reduce my risk for stroke?
• How many people have you treated for TIA and how many avoided stroke?

frequently to evaluate coagulation processes and conditions of the blood that could lead to hemorrhage.

Because the presence of fatty deposits in the carotid arteries of the neck is the most significant risk factor for ischemic stroke, treatment may involve correcting carotid artery blockage. If carotid artery disease is present and the narrowed artery has resulted in TIA, a carotid endarterectomy (CEA) may be performed to reduce risk of stroke. CEA is a surgical procedure that removes plaque deposits from the carotid arteries in the neck, restoring the flow of blood and oxygen to the brain and preventing risk of stroke. The National Institute of Neurological Disorders and Stroke (NINDS) reports that endarterectomy has proven to be especially protective for people who have already had a stroke or who have had TIAs and are at high risk for stroke.

Nutrition/Dietetic concerns

Lifestyle changes to reduce risk factors for TIA and stroke will necessarily include diet . A vegetarian diet has been shown to be associated with lower blood pressure, which is a risk factor for TIA and stroke. The DASH diet, a way of eating shown to reduce blood pressure, is described in Dietary Approaches to Stop Hypertension. It is recommended by the National Institutes of Health (NIH), the American Heart Association, and most heart doctors and is just as beneficial in preventing heart disease and stroke as it is in reducing blood pressure, because salt, fat and sugar content is far below the national average. The DASH diet consists of fruits, vegetables, low-fat dairy, whole grains, poultry, fish and nuts. Most Americans consume about 37% of calories as fat and 300 to 500 milligrams of dietary cholesterol daily. By contrast, the Lifestyle Heart Trial study conducted by noted heart doctor, Dean Ornish, M.D., put participating adults on a vegetarian diet that reduced their fat intake to 10% of total calories and dietary cholesterol to only 5 milligrams daily. When tested, participants were found to have significantly reduced atheroslclerosis, a significant risk factor for TIA and stroke, with greatly improved blood and oxygen flow throughout their bodies.

Prognosis

TIAs provide warning of possible serious stroke that can have debilitating effects. Giving immediate attention to a TIA can lead to appropriate treatment of risk factors, helping to prevent stroke. Ignoring TIAs will almost certainly lead to stroke and serious consequences.

Prevention

Lifestyle habits directly influence the risk factors and causes of TIA and stroke. Eating a balanced, whole foods diet with sufficient intake of nutrients and fiber is essential, including the avoidance of excess salt and not eating prepared, packaged foods that are high in salt and sugar and low in nutritional value. Regular exercise and maintaining a healthy weight appropriate for the individual's age and activity level are important as well. Smoking and alcohol consumption are known causes of conditions leading to atherosclerosis, heart disease and stroke and should be avoided; programs to stop smoking and using alcohol are available in most communities. Underlying diseases such as diabetes, atherosclerosis, high blood pressure and vascular disease must be managed through regular care of a physician.

Caregiver concerns

When caring for someone known to have conditions that lead to stroke such as heart disease, high blood pressure, obesity , diabetes, or previous stroke, or someone who smokes or consumes excess alcohol, it is necessary to be on the alert for uncharacteristic behavior and movements. Pay particular attention to changes in the face such as one side becoming drawn or drooping, or the presence of confusion or agitation, dizziness or difficulty walking. Ask the individual to move arms and legs and if they have normal feeling in the limbs. Ask the individual to smile and see if the smile is one-sided, and note if speech has changed in any way. Report any changes to the physician or emergency services without delay to ensure immediate diagnosis and treatment of possible TIA, which can help prevent stroke.

KEY TERMS

Atherosclerosis —The buildup of wax-like fatty deposits on the walls of medium and large arteries that later become calcified, narrowing the blood vessels and restricting blood flow.

Endarterectomy —A surgical procedure that removed damaged portions of arteries, including portions with atherosclerotic deposits, to open the vessels and restore unrestricted blood flow.

Ischemia —A type of localized anemia that occurs when blood and oxygen flow is reduced, robbing organ tissues of necessary oxygen.

Neurological deficit —Nervous system or neuromuscular disorders or symptoms.

Stenosis —Narrowing of any tubular-like vessel in the body, such as a cardiac valve (mitral stenosis) or an artery (carotid stenosis).

Vertebral arteries —Arteries that run along the cervical spine through the neck and into the brain stem.

Resources

BOOKS

“Ischemic Stroke” The Merck Manual of Diagnosis and Therapy, Section 16. R.S. Porter, ed. White House Station, NJ: Merck Research Laboratories, 2007.

“TIA.” Merck Manual of Diagnosis and Therapy. Section 16. R.S. Porter, ed. White House Station, NJ: Merck Research Laboratories, 2007.

“Carotid endarterectomy.” Gale Encyclopedia of Surgery. Michigan: Gale/Thomson, 2001.

Balch P A. “Atherosclerosis.” Prescription for Nutritional Healing. Garden City Park, NY: Avery, 1997.

PERIODICALS

Solenski NJ. “Transient Ischemic Attacks: Part I. Diagnosis and Evaluation. American Family Physician 69(4); 2004.

WEBSITES

“Transient Ischemic Attack.” American Heart Association. 2008. Available at www.americanheart.org. Accessed March 11, 2008.

“NINDS Transient Ischemic Attack Information.” National Institute of Neurological Disorders and Stroke (NINDS) March 2008. Available at www.ninds.nih.gov/disorders/tia/tia.htm. Accessed March 11, 2008.

The DASH Diet Action Plan Available at www.dashdiet.org/dash_diet_action_plan.htm. Accessed Feb. 4, 2008.

ORGANIZATIONS

American Heart Association, 7272 Greenville Avenue, Dallas, TX, 75231-4596, 214-373-6300, 800-AHA-8721, [email protected], www.americanheart.org.

National Stroke Association, 9707 East Easter Lane, Suite B, Centennial, CO, 801120-3747, [email protected], www.stroke.org.

L. Lee Culvert