transient ischemic attack

Transient Ischemic Attack

Definition

A transient ischemic attack, or TIA, is often described as a mini-stroke. Unlike a stroke, however, the symptoms can disappear within a few minutes. TIAs and strokes are both caused by a disruption of the blood flow to the brain. In TIAs and most strokes, this disruption is caused by a blood clot blocking one of the blood vessels leading to the brain. The blockage produces symptoms such as sudden weakness or numbness on one side of the body, sudden dimming or loss of vision, and difficulty speaking or understanding speech. If the symptoms are caused by a TIA, they last less than 24 hours and do not cause brain damage. Stroke-associated symptoms, on the other hand, do not go away and may cause brain damage or death. TIAs can serve as an early warning sign of stroke and require immediate medical attention.

Description

Strokes are the third leading cause of death in the United States and the leading cause of disability. Approximately 500,000-600,000 people have strokes each year, and more than 160,000 die as a result. About 85% of these strokes are classified as ischemic. In ischemic stroke, a blood vessel leading to the brain becomes blocked and an area of the brain is deprived of oxygenated blood. (The other 15% of strokes are caused by bleeding from a blood vessel that has ruptured.) Without the blood supply, the cells in that area of the brain die. Since brain cells cannot grow back, the functions that are controlled by that brain area may be permanently lost.Approximately 10% of strokes are preceded by one or more TIAs. The estimated annual number of TIAs is about 50,000; an exact count is difficult because TIAs are not always reported. They may be under-reported because they typically last less than an hour, perhaps only for a few minutes. Because they are so brief, TIAs may not seem important. However, an estimated one-third of all TIAs are followed by a stroke within five years. They are considered a medical emergency and prompt medical attention is very important.Risk factors for strokes and TIAs are very similar. The risk of a TIA or stroke is higher among men, African Americans, people over age 65, and people with heart disease or diabetes. Smokers, people with high blood pressure, and people who are overweight also have a greater risk for TIAs and strokes.

Causes and symptoms

A TIA is caused by a temporary blockage of one of the arteries that leads into the brain. Small blood clots, called microemboli, are the immediate cause of the blockage. The blockage forms because of damage or disease within the circulatory system. Blood clots can form in blood vessels because of artery damage, heart disease, and other cardiovascular problems. For example, atherosclerosis is strongly associated with TIAs. Atherosclerosis is the build-up of fatty deposits or plaque at certain areas in the circulatory system. Clotting cells in blood, called platelets, tend to stick to atherosclerotic plaques or other damaged sites within blood vessels. Occasionally, a clot may grow large enough to block a blood vessel, or a piece of a clot may break off and circulate to other areas of the body. If a clot does not dissolve quickly enough, it can lodge in a blood vessel and block it. In TIAs, the microemboli dissolve within a short time.Blood flows into the brain through two main pathways: the carotid arteries and the vertebrobasilar arteries. The carotid arteries are located on the front of the neck; the vertebrobasilar arteries are at the base of the skull at the back of the head. The symptoms produced by a TIA are determined by the arteries affected.If a vertebrobasilar artery is blocked, common symptoms include double vision and dizziness, nausea and vomiting, difficulty speaking, and problems understanding and using spoken words. There may also be a numbness around the mouth and a tingling sensation in the limbs. Blockage of a carotid artery produces complete loss of vision, dimmed or foggy vision, and paralysis or weakness on one side of the body. These symptoms also may be accompanied by language problems and speech difficulty.With either type of blockage, the microemboli dissolve within hours and full function returns.

Diagnosis

The goal of diagnosis is to identify the precise cause of the TIA and to recommend treatment. Initial information that an individual can supply includes a medical history, what drugs are currently being taken and why, and a full description of the symptoms. Blood tests are ordered to screen blood counts—the numbers of specific blood cell types—and to measure sugar and lipid (fats, including cholesterol) levels. Based on this information and a physical examination that includes blood pressure, pulse, and respiration measurements, one or more of the following imaging tests are ordered.A computed tomography scan (CT scan) or a magnetic resonance imaging (MRI) scan is usually the first imaging test. CT or MRI can rule out other problems, such as a tumor or subdural hematoma, which can mimic the symptoms of a TIA. A CT scan also can uncover aneurysms and arteriovenous malformation, both of which are blood vessel abnormalities that can cause bleeding in the brain.Another useful imaging test is carotid ultrasonography, a noninvasive procedure that allows examination of the interior of the carotid artery. This examination can detect carotid stenosis, a condition in which the artery is abnormally narrow because of atherosclerosis. Ultrasonography is very reliable in identifying stenosis, but it does not give enough information to accurately assess the degree of stenosis. Because the treatment used depends on the degree of stenosis, treatment decisions cannot be based on ultrasonography. Another type of ultrasonography, called transcranial doppler ultrasonography, is used to detect stenosis of the blood vessels within the brain and in the vertebrobasilar arteries.If stenosis is identified, a further test called cerebral arteriography may be done. This test is not done if the individual is in poor health, because it may be too risky. Arteriography involves injecting a special dye into the blood vessels that makes them visible on x rays. This procedure also is used to find suspected problems with blood vessels in the brain. Because it is an invasive procedure, complications may arise. Typically, these complications are minor and temporary. In a very small percentage of people with cardiovascular disease, the procedure may cause serious complications, such as stroke.Although TIAs affect the brain, the ultimate cause of the problem may be found in the heart. Heart disease or damage to the heart's blood vessels is assessed by echocardiography. Echocardiography is a type of ultrasonography and is a noninvasive procedure.

Treatment

Treatment is aimed at preventing further TIAs and especially at preventing a stroke. The particular therapy depends on the root cause of the TIA and is not begun until this cause is identified. If at all possible, drug therapy is the preferred method of treating TIAs. Surgical intervention may be required if an individual's situation is not likely to respond to medication or if medication has failed.Aspirin often is chosen for drug therapy. It is sometimes called a blood thinner because it blocks the function of platelets, the sticky cells that trigger blood clotting. Since aspirin can cause gastrointestinal side effects, other drugs may be prescribed. These drugs include dipyridamole or ticlopidine hydrochloride (Ticlid). Dipyridamole, which works by relaxing the smooth muscles of the arteries, is not as effective as aspirin. Ticlopidine hydrochloride is an anti-platelet drug that is slightly more effective than aspirin, especially in women. However, it may cause diarrhea or lowered blood cell counts. Blood tests must, therefore, be done frequently when patients are taking ticlopidine.If carotid arteriography reveals at least a 70% blockage of the carotid artery, surgical treatment usually is recommended. The particular surgical method is called carotid endarterectomy. In endarterectomy, the artery is opened and the material clogging it is removed. Another procedure, called angioplasty, has been suggested for treating carotid stenosis, but it is not widely used. This procedure is performed by threading a thin tube through the blood vessel to the site that is clogged. A balloon or a stent (a slender rod) is then passed through the tube to mechanically widen the narrowed area. This procedure is successfully used in other blood vessels in the body, but there is some worry that using it close to the brain may be too dangerous. Surgical treatment of blockage of the vertebrobasilar arteries is not usually recommended.Treatment of TIAs also focuses on underlying problems. High blood pressure, heart disease, and high levels of blood lipids all require medical intervention. Condition-specific medications often are prescribed and lifestyle changes are strongly encouraged. These changes include giving up smoking or excess alcohol consumption, engaging in physical exercise, and eating sensibly.

Prognosis

One-third of TIAs are followed by stroke in the next five years; in the other two-thirds, the TIAs may either continue or disappear on their own. However, because of the risk of stroke-related disability and death, all TIAs should be treated as emergency medical situations. In 2003, researchers discovered a naturally occurring system in the bodies of those who have TIAs that shields them from some of the brain damage that might occur in a second stroke. The researchers said that the changes in the brain that seem to protect it are similar to those that occur in hibernating animals. They hope by studying the genetics of these changes, they can develop medications that will help protect the bodies of people who have not had TIAs. It still is important to protect against further strokes following a TIA, however.Medical treatment significantly decreases the risk of stroke for people who experience one or more TIAs. Anti-platelet therapy with aspirin or ticlopidine may reduce risk as much as 31%. Carotid endarterectomy also substantially reduces stroke risk. The procedure itself carries some risk, but the complication rate is less than 5%. The risk of complication can be lowered by choosing to have the procedure done in a facility experienced with it and by a surgeon with a low complication rate.

Prevention

Treatment for TIAs is complemented by lifestyle changes. These practices also may prevent TIAs and strokes from ever occurring. Doctors and other health-care providers universally recommend that individuals stop smoking and consume alcohol in moderation. Regular health checkups can detect high blood pressure, heart disease, and other underlying problems. Adhering to treatment for these problems can help minimize TIA and stroke risks. A Danish study seemed to confirm in 2003 that eating more citrus fruit reduces the risk of TIA and stroke. Finally, maintaining a healthy weight and engaging in regular exercise as able are strongly recommended.

Resources

Periodicals

Johnsen, Soren P., et al. "Intake of Fruit and Vegetables and the Risk of Ischemic Stroke in a Cohort of Danish Men and Women." American Journal of Clinical Nutrition July 2003: 57-58."Reserachers Uncover the Brainós Stroke Protection System." Biotech Week October 29, 2003: 3.

Organizations

American Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300. http://www.americanheart.org.National Stroke Association. 9707 E. Easter Lane, Englewood, Co. 80112. (800) 787-6537. http://www.stroke.org.

Key terms

Angioplasty — A medical procedure in which a catheter, or thin tube, is threaded through blood vessels. The catheter is used to place a balloon or stent (a small metal rod) at an area of stenosis and expand it mechanically.Arteriography — A medical test in which an x-ray visible dye is injected into blood vessels. This dye allows the blood vessels to be imaged with x rays.Atherosclerosis — A build-up of fatty tissue called plaque inside arteries that can impede or block blood flow.Carotid artery — One of the major blood vessels leading to the brain; it runs up the front of the neck.Echocardiography — A type of ultrasonography that is used to create an image of the heart and its functioning.Endarterectomy — A surgical procedure in which diseased tissue and atherosclerotic plaque are removed from the inside of an artery.Ischemia — A condition in which blood flow is cut off or restricted from a particular area. The surrounding tissue, starved of oxygen and nutrients, dies.Microemboli — Small blot clots in the bloodstream.Platelets — Tiny cells in the blood that help form blood clots.Stenosis — The narrowing of an opening or passage-way in the body. In arteries, stenosis is caused by a build-up of atherosclerotic plaque, disease, or other disorder.Stroke — A condition in which blood flow to the brain has been blocked, thereby causing brain cells to die from lack of oxygen and nutrients; also called a "brain attack."Ultrasonography — A medical test in which sound waves are directed against internal structures in the body. As sound waves bounce off the internal structure, they create an image on a video screen.Vertebrobasilar arteries — Major blood vessels that lead to the brain. They are located at the base of the skull at the back of the head.

transient ischemic attack

(TIA) a sudden episode of temporary symptoms typically due to diminished blood flow through the brain, usually defined as lasting between 24 and 48 hours. It is sometimes related to impaired blood flow through the vertebrobasilar vessels. The symptoms are warning signals of impending stroke; approximately one in three persons experiencing a TIA will have a stroke syndrome within 5 years.

The symptoms of TIA can range from obvious loss of sensation or motor function to more subtle changes in speech or mental acuity. During the attack the person may feel numbness or weakness or both on one side of the body, slurring of speech or inability to talk, or difficulty in thinking. Disturbance in the vision of one eye and double vision also are typical of TIA. Because these signs are short lived, many persons may be inclined to ignore them unless they are informed of their importance and of the need to consult medical help before a catastrophic stroke occurs. Carotid artery occlusions usually can be corrected by surgery.

tran·sient is·che·mic at·tack (TIA),

a sudden focal loss of neurologic function with complete recovery usually within 24 hours; caused by a brief period of inadequate perfusion in a portion of the territory of the carotid or vertebral basilar arteries.

transient ischemic attack

n. Abbr. TIA A temporary blockage of the blood supply to the brain caused by a blood clot and usually lasting ten minutes or less, during which dizziness, blurring of vision, numbness on one side of the body, and other symptoms of a stroke may occur. Also called ministroke.

transient ischemic attack

Little stroke, ministroke Neurology A focal, abrupt ischemia-induced loss of brain function, caused by ↓ blood flow, especially by microemboli from ASHD plaques and embolic showers, accompanied by disability of < 24 hrs, usually < 1 hr in duration; symptomatic TIAs often precede cerebral infarcts or strokes, more common in older Pts with marked cerebrovascular ASHD, and may affect any cerebral vessel; despite clinical resolution, CT demonstrates residual anatomic lesions in 15% with ischemic neurologic disability and TIAs Etiology ASHD, polycythemia, sickle cell anemia, hyperviscosity syndromes, spasm of small arteries in the brain, blood vessels defects caused by disorders such as fibromuscular dysplasia, vasculitis, polyarteritis, granulomatous angiitis, SLE, syphilis Imaging MRI, carotid artery ultrasonography, MR angiography Risk factors HTN, heart disease, migraines, smoking, DM, ↑ age♂, African-Americans Prevention Low dose–eg, 30 mg aspirin, a level at which inhibition of aggregation due to ↓ production of platelet thromboxane A₂ is still complete, but the production of prostacyclin, which has an antiaggregation effect is unaffected in endothelial cells; prostacyclin production is inhibited by higher doses of aspirin. See Reversible ischemic neurological disability.

tran·si·ent is·che·mic at·tack

(TIA) (tran'sē-ĕnt is-kē'mik ă-tak') A sudden focal loss of neurologic function with complete recovery usually within 24 hours; caused by a brief period of inadequate perfusion in a portion of the territory of the carotid or vertebral basilar arteries.

tran·si·ent is·che·mic at·tack

(TIA) (tran'shĕnt is-kē'mik ă-tak') Sudden focal loss of neurologic function with complete recovery usually within 24 hours; caused by a brief period of inadequate perfusion in a portion of the territory of the carotid or vertebral basilar arteries.

transient ischemic attack

transient ischemic attack

tran′sient ische′mic attack`

transient ischemic attack

transient ischemic attack

transient ischemic attack

Transient Ischemic Attack

Definition

Description

Causes and symptoms

Diagnosis

Treatment

Prognosis

Prevention

Resources

Periodicals

Organizations

Key terms

transient ischemic attack

tran·sient is·che·mic at·tack (TIA),

transient ischemic attack

transient ischemic attack

tran·si·ent is·che·mic at·tack

tran·si·ent is·che·mic at·tack

transient ischemic attack

Synonyms for transient ischemic attack

noun brief episode in which the brain gets insufficient blood supply

Synonyms

Related Words