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A stroke is a sudden event affecting the brain's blood supply. In an ischemic stroke, a blood vessel that supplies the brain becomes blocked. In a hemorrhagic stroke, a blood vessel in the brain bursts.
The tem "brain attack" is sometimes used to describe a stroke because it is similar to how the heart muscle is suddenly deprived of blood during a "heart attack".
The symptoms of a stroke depend on where in the brain the blood vessels have been blocked or have ruptured.
Stroke Warning Signs
Call 911 immediately if you suspect you or someone you know is experiencing any of the symptoms of a stroke. Do not wait. There are now effective therapies for stroke that must be administered at a hospital, but they lose their effectiveness if not given within the first 3 hours after stroke symptoms appear. Every minute counts! (See Stroke Warning Signs)
What Happens During a Stroke?
Brain cells die when they no longer receive oxygen from the blood or when they are damaged by sudden bleeding into the nearby brain tissue. Ischemia describes the loss of oxygen and nutrients for brain cells when there is not enough blood flow. Ischemia of the brain cells lead to their death (infarct).
When blood flow to the brain is interrupted, some brain cells die immediately, while others remain at risk for death. These damaged cells create a region in the brain called the "ischemic penumbra" that can linger in a compromised state for several hours before either recovering or dying. These damaged nerve cells can often be saved with immediate treatment.
Although stroke is most common in older people, it can occur in individuals of any age, including young adults and children. About 1 in 6 Americans will experience a stroke at some point after age 65. Stroke is fatal in about 10-20% of cases and, among survivors, it can cause a host of disabilities, including loss of mobility, impaired speech, and cognitive problems. This makes stroke the 3rd leading cause of death in the U.S. (behind heart disease and cancer) and a major cause of disability.
The long-term outcomes after a stroke vary considerably and depend partly on the type of stroke and the age of the affected person. Although most stroke survivors regain their functional independence, 15-30% will have a permanent physical disability. Some will experience a permanent decline in cognitive function known as post-stroke or vascular dementia.
Unfortunately, many stroke survivors face a danger of recurrent stroke in the future. About 20% of people who experience a first-ever stroke between ages 40 and 69 will have another stroke within five years.
Reference: The National Institute of Neurological Disorder and Stroke.