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What is a stroke?

A stroke or brain attack occurs when a blood clot blocks a blood vessel or artery, or when a blood vessel breaks, interrupting blood flow to an area of the brain. When a brain attack occurs, it kills brain cells in the immediate area. Doctors call this area of dead cells an infarct. These cells usually die within minutes to a few hours after the stroke starts.

When brain cells in the infarct die, they release chemicals that set off a chain reaction called the "ischemic cascade." This chain reaction endangers brain cells in a larger, surrounding area of brain tissue for which the blood supply is compromised but not completely cut off. Without prompt medical treatment this larger area of brain cells, called the penumbra, will also die. Given the rapid pace of the ischemic cascade, the "window of opportunity" for interventional treatment is about six hours. Beyond this window, reestablishment of blood flow and administration of neuroprotective agents may fail to help and can potentially cause further damage.

When brain cells die, control of abilities which were once controlled by the brain are lost. This includes functions such as speech, movement, and memory. The specific abilities lost or affected depend on the severity and location of the stroke. For example, someone who has a small stroke may experience only minor effects such as weakness of an arm or leg. On the other hand, someone who has a larger stroke may be left paralyzed on one side or lose his/her ability to express and process language. Some people recover completely from less serious strokes, while other individuals lose their lives to very severe strokes.

• Cleveland FES Center Clinical Partners
  • Cleveland VA Medical Center
  • MetroHealth Medical Center
  • University Hospitals of Cleveland
  • Cleveland Clinic Foundation
• For More Stroke Information
  • The National Stroke Association
  • American Stroke Association