Also known as a "mini-stroke," a TIA (or transient ischemic attack) occurs when there is a temporary lack of oxygen- or nutrient-rich blood to a part of the brain. The two most common causes of this event are an embolism and thrombosis. Symptoms are similar to those seen with a stroke and can include confusion, dizziness, loss of coordination, and sudden numbness or weakness of the limbs and face (especially on one side of the body). While symptoms of a stroke last for at least 24 hours, TIA symptoms may improve within 30 minutes.
A transient ischemic attack (TIA for short) starts just like a stroke but then resolves, leaving no noticeable symptoms or deficits. This is why a TIA is sometimes called a mini-stroke. The occurrence of a TIA is a warning that the person is at risk for a stroke, which is usually more serious and debilitating. Of the approximately 50,000 Americans who have a TIA each year, about one-third will have an acute stroke sometime in the future.
A TIA is caused by a temporary lack of oxygen- or nutrient-rich blood to a part of the brain. This lack of blood supply occurs because a blood vessel becomes severely narrowed or blocked.
There are several ways in which a blood vessel in the brain may become severely narrowed or blocked. The two most common are an embolism and thrombosis. An embolism occurs when a blood clot or other tissue from another part of the body (such as the heart) moves through the blood into the neck or brain.
Thrombosis occurs when a blood clot (known as a thrombus) forms within a blood vessel of the brain or neck. Unlike an embolism, with thrombosis the blood clot does not break free.
A third way in which a blood vessel can become narrowed or blocked involves stenosis. Stenosis is severe narrowing of an artery in or leading to the brain. It is most often caused by plaque buildup.
Keep in mind that the causes of mini-strokes are the same as those of ischemic strokes (see Stroke Causes). The only difference between the two involves timing. By definition, a stroke produces symptoms that last for at least 24 hours. A mini-stroke causes symptoms that improve after a shorter period of time (usually less than 30 minutes).
(Click Causes of Transient Ischemic Attacks for more information on these specific causes.)