TIAs may last from a few minutes to a few days and are often a warning sign that a stroke may occur. Although usually mild and transient, the symptoms caused by a TIA are similar to those caused by a stroke. Another type of stroke that occurs in the small blood vessels in the brain is called a lacunar infarct. Embolic strokes often result from heart disease or heart surgery and occur rapidly and without any warning signs. About 15 percent of embolic strokes occur in people with atrial fibrillation, a type of abnormal heart rhythm in which the upper chambers of the heart do not beat effectively.
Hemorrhagic strokes occur when a blood vessel that supplies the brain ruptures and bleeds.
When an artery bleeds into the brain, brain cells and tissues do not receive oxygen and nutrients. In addition, pressure builds up in surrounding tissues and irritation and swelling occur. About 20 percent of strokes are caused by hemorrhage. There are usually no warning signs and bleeding can be severe enough to cause coma or death. An aneurysm is a weakened, ballooned area on an artery wall and has a risk for rupturing.