Sometimes the clot will move and block vessels that carry blood to the brain. The result is a brain attack. Ischemia caused by a brain attack can be localized or widespread. Widespread or global ischemia affects the entire brain and is caused by a brief but high-volume decrease in the brain s total blood supply. The decrease most often results from cardiac arrest, a sudden drop in blood pressure, or cardiac arrhythmia.
Localized ischemia occurs during an ischemic brain attack.
Blood supply often falls dramatically in a dense core of tissue. This core is surrounded by a less seriously affected area. This area is most likely to respond to the administration of fibrinolytic or clot busting agents. A series of events leading to tissue damage progresses over several hours. Sustaining the health of brain tissue is dependent on time, both in the core and the less seriously affected areas.