Medical Health Encyclopedia

Transient ischemic attack (TIA)

Cholesterol and other fats also collect at this site, forming a mass within the lining of the artery. A clot (thrombus) may form at the site of the plaque, triggered by irregular blood flow in this location, and the thrombus may then block blood vessels in the brain.

Pieces of plaque or clots can also break off and travel through the bloodstream from distant locations, forming an embolus that can block the small arteries, causing TIAs.

About one-third of the people diagnosed with TIA will later have a stroke. And about 80-90% of people who have a stroke caused by atherosclerosis had TIA episodes before their stroke. Approximately one-third of the people who have a TIA will have another TIA, while one-third will have only one TIA. The age of onset varies, but incidence rises dramatically after age 50. TIA is more common among men and black people.

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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. Other risks for TIA include high blood pressure (hypertension), heart disease, migraine headaches, smoking, diabetes mellitus, and increasing age.

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