A transient ischemic attack (TIA) is a disturbance in brain function that typically lasts less than 1 hour and results from a temporary blockage of the brain’s blood supply.
- The cause and symptoms of a TIA are the same as those of an ischemic stroke.
- TIAs differ from ischemic strokes because symptoms usually resolve within 1 hour and no permanent brain damage occurs.
- Symptoms suggest the diagnosis, but brain imaging is also done.
- Other imaging tests and blood tests are done to diagnose the cause of the TIA.
- Controlling high blood pressure, high cholesterol levels, and high blood sugar levels and stopping smoking are recommended.
- Drugs to make blood less likely to clot and sometimes surgery (carotid endarterectomy) or angioplasty plus stenting are used to reduce the risk of stroke after a TIA.
TIAs may be a warning sign of an impending ischemic stroke. People who have had a TIA are much more likely to have a stroke than those who have not had a TIA. The risk of stroke is highest during the first 24 to 48 hours after the TIA. Recognizing a TIA and having the cause identified and treated can help prevent a stroke.
TIAs are most common among middle-aged and older people.
TIAs differ from ischemic strokes because TIAs do not seem to cause permanent brain damage. That is, TIA symptoms resolve completely and quickly, and few or no brain cells died—at least not enough to cause any changes that can be detected by brain imaging or a neurologic examination.
Causes of TIAs and ischemic strokes are mostly the same. Most TIAs occur when a piece of a blood clot (thrombus) or of fatty material (atheroma, or plaque) due to atherosclerosis breaks off from the heart or from the wall of an artery (usually in the neck), travels through the bloodstream (becoming an embolus), and lodges in an artery that supplies the brain.
If the arteries to the brain are already narrowed (as in people with atherosclerosis), other conditions occasionally cause symptoms similar to those of TIAs. These conditions include a very low oxygen level in the blood (as may result from a lung disorder), a severe deficiency of red blood cells (anemia), carbon monoxide poisoning, thickened blood (as in polycythemia), or very low blood pressure (hypotension).
Risk factors for TIAs are also the same as those for ischemic stroke.
Some of these risk factors can be controlled or modified to some extent—for example, by treating the disorder that increases risk.
The major modifiable risk factors for TIAs are
- High cholesterol levels
- High blood pressure
- Insulin resistance (an inadequate response to insulin), which occurs in type 2 diabetes
- Cigarette smoking
- Obesity, particularly if the excess weight is around the abdomen
- Consumption of too much alcohol
- Lack of physical activity
- An unhealthy diet (such as one that is high in saturated fats, trans fats, and calories)
- Depression or other mental stresses
- Heart disorders that increase the risk of blood clots forming in the heart, breaking off, and traveling through the blood vessels as emboli (such as a heart attack or an abnormal heart rhythm called atrial fibrillation)
- Infective endocarditis (infection of the heart's lining and usually of the heart valves)
- Use of cocaine or amphetamines
- Inflammation of blood vessels (vasculitis)
- Clotting disorders that result in excessive clotting
- Use of estrogen therapy, including oral contraceptives
Risk factors that cannot be modified include
- Having had a stroke previously
- Being male
- Being older
- Having relatives who have had a stroke
Symptoms of a TIA develop suddenly. They are identical to those of an ischemic stroke but are temporary and reversible. They usually last 2 to 30 minutes, then resolve completely.
People may have several TIAs in 1 day or only two or three in several years.
Symptoms may include
- Sudden weakness or paralysis on one side of the body (for example, half of the face, one arm or leg, or all of one side)
- Sudden loss of sensation or abnormal sensations on one side of the body
- Sudden difficulty speaking (such as slurred speech)
- Sudden confusion, with difficulty understanding speech
- Sudden dimness, blurring, or loss of vision, particularly in one eye
- Sudden dizziness or loss of balance and coordination
- Rapid resolution of symptoms
- Computed tomography and, when available, magnetic resonance imaging
- Tests to determine the cause
People who have a sudden symptom similar to any symptom of a stroke, even if it quickly resolves, should go immediately to an emergency department. Such a symptom suggests a TIA. However, other disorders, including seizures, brain tumors, migraine headaches, and abnormally low levels of sugar in the blood (hypoglycemia), cause similar symptoms, so further evaluation is needed.
Doctors suspect a TIA if symptoms of a stroke develop, particularly if they resolve in less than 1 hour. Doctors may be unable to tell a stroke from a TIA before symptoms resolve. They evaluate people who have symptoms of a TIA or stroke rapidly. People who have had a TIA are usually admitted in the hospital, at least for a short time, to do tests and to be able to treat them rapidly if a stroke occurs soon after the TIA. Risk of a stroke is highest during the first 24 to 48 hours after a TIA.
Doctors check for risk factors for stroke by asking people questions, reviewing their medical history, and doing blood tests.
Imaging tests, such as computed tomography (CT) or magnetic resonance imaging (MRI), are done to check for evidence of a stroke, bleeding, and brain tumors. A specialized type of MRI, called diffusion-weighted MRI, can show areas of brain tissue that are severely damaged and not functioning. Diffusion-weighted MRI can often help doctors differentiate a TIA from an ischemic stroke. However, diffusion-weighted MRI is not always available.
Tests are done to determine what caused the TIA. Tests may include
- Electrocardiography (ECG), including continuous ECG monitoring, to look for abnormal heart rhythms
- Echocardiography to check the heart for blood clots, pumping or structural abnormalities, and valve disorders
- Other imaging tests
- Blood tests to check for disorders such as anemia and polycythemia and for risk factors such as high cholesterol levels or diabetes
Other imaging tests help determine whether an artery to the brain is blocked, which artery is blocked, and how complete the blockage is. These tests provide images of the arteries that carry blood through the neck to the brain (the internal carotid arteries and the vertebral arteries) and the arteries of the brain (such as the cerebral arteries). They include color Doppler ultrasonography (used to evaluate blood flow through arteries), magnetic resonance angiography, and CT angiography.
Did You Know...
- Control of risk factors for TIAs
- Drugs that make blood less likely to clot
- Sometimes surgery or angioplasty with a stent
Treatment of TIAs is aimed at preventing a stroke. It is the same as treatment after an ischemic stroke.
The first step in preventing a stroke is to control, if possible, the major risk factors for it:
- High blood pressure
- High cholesterol levels
People may be given a drug to make blood less likely to clot (an antiplatelet drug or an anticoagulant).
Taking an antiplatelet drug, such as aspirin, a combination tablet of low-dose aspirin plus dipyridamole, clopidogrel, or clopidogrel plus aspirin, reduces the chance that clots will form and cause TIAs or ischemic strokes. Antiplatelet drugs make platelets less likely to clump and form clots. (Platelets are tiny cell-like particles in the blood that help it clot in response to damaged blood vessels.)
Taking clopidogrel plus aspirin appears to reduce the risk of future strokes more than taking aspirin alone, but only for the first 3 months after a stroke. After that, the combination has no advantage over taking aspirin alone. Also, taking clopidogrel plus aspirin increases the risk of bleeding by a small amount.
If a blood clot from the heart caused the TIA, anticoagulants, such as warfarin, are given to make blood less likely to clot. Dabigatran, apixaban, and rivaroxaban are new anticoagulants that are sometimes used instead of warfarin. These newer anticoagulants are more convenient to use because they, unlike warfarin, do not require regular monitoring with blood tests to measure how long it takes blood to clot. Also, they are not affected by foods and are unlikely to interact with other drugs. But the new anticoagulants have some disadvantages. Dabigatran and apixaban must be taken twice a day. (Warfarin is taken once a day.) Also, people must not miss any doses of the newer drugs for the drugs to be effective, and these drugs are significantly more expensive than warfarin.
The degree of narrowing in the carotid arteries helps doctors estimate the risk of a stroke or subsequent TIAs and thus determine the need for further treatment. If people are thought to be at high risk (for example, if the carotid artery is narrowed at least 70%), an operation to widen the artery (called carotid endarterectomy) may be done to reduce the risk. Carotid endarterectomy usually involves removing fatty deposits (atheromas, or plaques) due to atherosclerosis and clots in the internal carotid artery. However, the operation can trigger a stroke because the operation may dislodge clots or other material that can then travel through the bloodstream and block an artery. However, after the operation, the risk of stroke is lower for several years than it is when drugs are used. The procedure can result in a heart attack because people who have this procedure often have risk factors for coronary artery disease.
If people are not healthy enough to have surgery, angioplasty with stenting (see figure Understanding Percutaneous Coronary Intervention (PCI)) may be done. For this procedure, a catheter with a balloon at its tip is threaded into the narrowed artery. The balloon is then inflated for several seconds to widen the artery. To keep the artery open, doctors insert a tube made of wire mesh (a stent) into the artery.
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