Causes of Transient Ischemic Attacks: Embolism
A blood clot or other tissue in the blood (such as fat) from a part of the body other than the brain can travel through blood vessels and become wedged in a smaller brain artery. This free-roaming clot or tissue is called an embolus (emboli is plural). Emboli often form in the heart. They also commonly form in the neck arteries or within the aorta.
There are several conditions that increase a person's chances for developing an embolus. One of the most common is in people with
atrial fibrillation, sick sinus syndrome or other irregular heart rhythms. These conditions can cause poor blood flow which allows harmful clots to form. Emboli are also more likely to form in people with:
If the body is able to dissolve an embolus, allowing normal blood flow again, then the person will only suffer a
TIA. If the body is not able to dissolve the embolus before brain tissue is damaged, then the person will suffer a
stroke.
Thrombosis as a Cause of a Transient Ischemic Attack
A blood clot can also form in one of the brain arteries (called cerebral arteries) but instead of breaking free remains attached to the artery wall until it grows large enough to block blood flow. This type of clot is known as a thrombus.
Most of the time, a thrombus occurs within an area of the brain damaged by
atherosclerosis. In atherosclerosis (also known as
hardening of the arteries), deposits of
plaque (a mixture of fatty substances, including
cholesterol and other lipids) build up along the inner walls of large and medium-sized arteries, causing thickening, hardening, and loss of elasticity of artery walls and decreased blood flow. This increases the risk that a thrombus will form, causing severe narrowing or complete blockage of the affected blood vessel.
If the body is able to dissolve a thrombus that severely narrows or blocks an artery, allowing normal blood flow again, then the person will only suffer TIA symptoms. If the body is not able to dissolve the clot before brain tissue is damaged, then the person will have a stroke.
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