Doctor's Notes on What Is a Stroke?
A stroke is an alteration, usually acute, of brain function due to injured or killed brain cells. Symptoms and signs of stroke include weakness in the arm or leg or both (usually on one side of the body), weakness of the muscles of the face, problems speaking, coordination problems, and dizziness and/or loss of consciousness. Some patients may develop vision problems and develop a severe headache. Although some patients may show some improvement in the signs and symptoms, a true stroke has some or all of the signs and symptoms still present after 24 hours. Some individuals may die during a stroke. Signs and symptoms of a stroke constitute a medical emergency and 911 should be called.
Some symptoms and signs described above can occur in individuals but resolve quickly and completely in less than 24 hours; these signs and symptoms are signs of a transient ischemic attack (mini stroke or TIA). TIA’s are signs and symptoms of the patient being at risk for a stroke.
The two main causes of strokes are ischemic or hemorrhagic problems with the brain’s blood vessels. Ischemic strokes (the cause of about 80 – 85% of strokes) are due to blood vessels that are blocked usually due to a clot while with a hemorrhagic stroke, the blood vessels in the brain actually burst or leak blood. That leakage allows blood to spill into the brain tissue causing a buildup of pressure on brain tissue and other brain blood vessels. Hemorrhagic strokes usually are more serious than ischemic strokes; death usually occurs in 30 to 50% of individuals with this stroke type. Both types of strokes produce similar symptoms that signal brain tissue injury and/or death due to lack of oxygen supplied by the blood, but their emergency treatments are different – call 911 as a stroke cause needs to be identified quickly in an emergency center, usually by a CT of the brain.
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.