| Disease | Injury | Nutrition | Poison |
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Transient ischemic attack (TIA) |
| Definition: |
| A brain disorder caused by temporary disturbance of blood supply to an area of the brain, resulting in a sudden, brief (less than 24 hours, usually less than 1 hour) decrease in brain functions. |
| Alternative Names: |
| Mini stroke; TIA; Little stroke |
| Causes, incidence, and risk factors: |
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The brain requires about 20% of the circulation of blood in the body. A primary blood supply to the brain is through two arteries in the neck (the carotid arteries) that branch off within the brain to multiple arteries that supply specific areas of the brain. The vertebral arteries supply the posterior part of the brain and brainstem. Even a brief interruption to the blood flow can cause a decrease in brain function (neurologic deficit). Symptoms vary with the area of the brain affected and commonly include such problems as changes in vision, speech or comprehension changes, vertigo, decreased movement or sensation in a part of the body, and changes in the level of consciousness. If the blood flow is decreased for longer than a few seconds, brain cells in the area die (infarct), causing permanent damage to that area of the brain or even death. The major causes of loss of blood circulation to areas of the brain are reduced blood flow (ischemia) and bleeding (hemorrhage). Transient ischemic attack (TIA, "little stroke") is a warning that the body's safety mechanisms are overloaded and indicates that a stroke may be pending. About one-third of the people with TIA will later have a stroke. However, about 80 to 90% of people who have a stroke secondary to atherosclerosis had TIA episodes before their stroke. Approximately one-third of the people with TIA will have recurrent TIAs, and one-third will have only a single episode of TIA. The age of onset varies, but incidence rises dramatically after age 50. TIA is more common among men and African-Americans. A TIA is caused by a temporary state of reduced blood flow (ischemia) in a portion of the brain. This is most frequently caused by tiny blood clots (microemboli) that temporarily occlude a portion of the brain. The microemboli are caused by atherosclerotic plaque in the arteries that supply the brain. Atherosclerosis ("hardening of the arteries") is a condition where fatty deposits occur on the inner lining of the arteries. Atherosclerotic plaque is formed when damage occurs to the lining of an artery. Platelets clump around the area of injury as a normal part of the clotting and healing process. Cholesterol and other fats also collect at this site, forming a mass within the lining of the artery. Clots (thrombus) may form at the site of the plaque, triggered by irregular blood flow in this location, and the thrombus may occlude the blood vessels in the brain. Pieces of plaque or clots may break off and travel through the bloodstream from distant locations, forming an embolus that can occlude the small arteries, causing TIAs. Occlusions that last for more than a few minutes more commonly cause stroke. Less common causes of TIA include blood disorders (including polycythemia, sickle cell anemia, and hyperviscosity syndromes where the blood is very thick), spasm of the small arteries in the brain, abnormalities of blood vessels caused by disorders such as fibromuscular dysplasia, inflammation of the arteries (arteritis, polyarteritis, granulomatous angiitis), systemic lupus erythematosus, and syphilis. Hypotension (low blood pressure) may precipitate symptoms in an individual with a pre-existing vascular lesion. Risks for TIA include high blood pressure (hypertension), heart disease, migraineheadaches, smoking, diabetes mellitus, and increasing age. |
| Symptoms: |
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| Signs and tests: |
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A detailed and complete history is vital to the diagnosis, because the specific deficits demonstrated correspond well with the specific lesion or affected area of the brain. For example, involvement of one arm or leg may indicate damage to one brain artery, while loss of vision or difficulty talking may suggest a different location. Physical examination may include neurologic examination, which may be abnormal during an episode but normal after the episode has passed. It may also be used to rule out a stroke in evolution rather than TIA. The eyes may be examined, including a check of the pressures within the eye. Blood pressure may be high. Auscultation with a stethoscope over the carotid or other artery may show a bruit, an abnormal sound caused by irregular blood flow, which may indicate atherosclerotic plaque or a thrombus in the area. Tests for TIA may include tests to determine the cause, extent of blood vessel involvement, and to rule out stroke or other disorder that may cause the symptoms.
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| Treatment: |
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The goal of treatment is to improve the arterial blood supply to the brain and prevent development of stroke. Treatment of recent TIA (within the prior 48 hours) usually requires admission to the hospital for evaluation of the specific cause and determination of long-term treatment. Underlying disorders should be treated appropriately, including such disorders as hypertension, heart disease, diabetes, arteritis, blood disorders, etc. Smoking should be stopped. Treatment of symptoms of blood disorders (such as erythrocytosis, thrombocytosis, or polycythemia vera, which include increase in the number of some of the cellular components of blood) may include phlebotomy, hydration, and treatment of the underlying (causative) blood disorder. Antihypertensive medications may be used to control high blood pressure. Medications to lower cholesterol may be useful in reducing high blood cholesterol levels. Platelet inhibitors and anticoagulant medications (blood thinners) may be used to reduce clotting. Aspirin is the most commonly used medication; others include dipyridamole, clopidogrel, Aggrenox or heparin, coumadin, or other similar medications. Treatment may be continued for an indefinite time period. A reduced amount of sodium (salt) in diet to help control high blood pressure; diet for diabetics; reduced dietary fat, or other dietary changes may be recommended. Surgery (carotid endarterectomy, removal of atherosclerotic plaque from the carotid arteries in the neck) may be appropriate for some people, particularly those with carotid artery stenosis of greater than 70% of the artery and without coexisting terminal disease or dementia. |
| Expectations (prognosis): |
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Each episode of TIA is brief and recovery is complete. It may recur later that same day or at a later time. Some people have only a single episode, some have recurrent episodes, and some will have a stroke. |
| Complications: |
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| Calling your health care provider: |
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Call your health care provider if symptoms indicate TIA. Do not ignore symptoms just because they resolve! They may be a warning of an impending stroke. Go to the emergency room or call the local emergency number (such as 911) if symptoms worsen or new symptoms develop. Emergency symptoms include loss of consciousness, sudden development of partial or complete paralysis or numbness, sudden vision change or loss of vision in one or both eyes, and rapid onset of speech changes. |
| Prevention: |
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Prevention of TIA includes control of risk factors. Hypertension, diabetes, heart disease, and other associated disorders should be treated as appropriate. Smoking should be stopped or minimized. |
Reviewed By: Galit Kleiner-Fisman, MD, Beth-Israel Deaconess Medical Center, Boston, MA. Review provided by VeriMed Healthcare Network.
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