What is a Stroke?A stroke—also called a cerebrovascular accident or "brainattack"—is a medical emergency where part of the brain isdeprived of oxygen. This occurs when an artery that suppliesoxygenated blood to the brain becomes damaged in one of severalways. Within minutes of being deprived of oxygen, brain cellsbegin to die. The longer the brain goes without oxygenated blood,the greater the chances of permanent damage.The death of brain cells allows for the accumulation of toxicchemicals that blood, when flowing properly, usually removes fromthe brain. Without proper treatment, the accumulation can affectnearby cells. Potential damage from a stroke includes paralysis,impaired speech, memory loss, coma, or death.
Prompt treatment improves the chances for survival and decreasesthe risk of brain damage.Approximately 795,000 Americans suffer a stroke each year. Ofthose who have a stroke, about 150,000 die each year, making it thethird leading cause of death in the country. About 75 percent ofstroke victims are over the age of 65.Worldwide, there are 15 million strokes a year. Of those, a third dieand another third are permanently disabled.Despite these daunting statistics, thanks to education, prevention,and medical advances, fewer people are dying from strokes everyyear.
Types of StrokesA stroke is categorized by the nature of the blockage and where itoriginates. Two main categories of strokes are ischemic andhemorrhagic.Ischemic StrokesClots form in arteries and block blood flow in a process calledischemia, and there are two types of ischemic strokes. When a clotoriginates in the brain and blocks blood flow, it is called athrombotic stroke. A clot can also form in another part of the body,such as the arm or heart, and then travel through blood vesselsand get lodged in the brain. This is called an embolic stroke. Thetwo most common ischemic strokes—which account for about 75percent of all strokes—are as follows:
Cerebral Thrombosis: Thrombosis is the medical term for ablood clot. This type of stroke occurs when a blood clot formsinside the brain, blocking the flow of blood through a vessel. It isoften preceded by a smaller kind of stroke known as transientischemic attack (TIA)—also called a "mini stroke."Cerebral Embolism: This category of stroke occurs when a bloodclot breaks free from another part of the body, most often theheart, and travels through the vessel into the brain where it clogsan artery and disrupts the flow of blood.Other categories of ischemic strokes include strokes caused byblood clots formed in the heart (often caused by irregularheartbeat, heart attack,
or abnormalities of the heart valves), those caused by bloodclotting disorders, and those caused by traumatic injury to theblood vessels in the neck.Overall, clots are responsible for about90 percent of all strokes.Hemorrhagic StrokesA stroke can also occur when a blood vessel breaks or bursts,known as a hemorrhage. The two most common types ofhemorrhagic strokes are as follows:Subarachnoid Hemorrhage: Hemorrhage occurs when a bloodvessel breaks inside the brain. This is most likely to occur in anarea of aneurysm, or weakening, in the wall of the vessel.Intracerebral Hemorrhage: This type of hemorrhaging involvessmall vessels deep within the brain tissue.