A stroke occurs when the flow of blood to a part of the brain is cut off. This can be due to something (usually a blood clot) blocking the flow of blood to the brain (ischemic stroke). It can also be caused by a burst blood vessel bleeding into the brain (hemorrhagic stroke). About 80% of strokes are ischemic and 20% are hemorrhagic. Without a blood supply, the brain cells in the affected area start to die.
The effects of a stroke depend on which part of the brain is affected and how severe the damage is. A stroke may affect your ability to move, your ability to speak and understand speech, your memory and problem-solving abilities, your emotions, and your senses of touch, hearing, sight, smell, and taste. In some cases, a stroke can be fatal.
It's important to recognize the warning signs of stroke, because quick treatment can reduce the risk of brain injury and death. A stroke usually comes on suddenly, over a few minutes or hours.
The warning signs of stroke include:
- sudden weakness, numbness, or tingling of the face, arm, or leg (often on only one side of the body)
- sudden confusion, trouble speaking, or trouble understanding speech
- sudden vision loss (often in one eye only) or double vision
- sudden trouble walking, dizziness, loss of balance or coordination, or falls
- sudden severe headache (often described as "the worst headache of my life") with no known cause
If you notice these symptoms, call 911 (or your emergency medical number if you do not have 911 service) immediately. Stroke is a medical emergency.