What Is Stroke?
A stroke occurs when a blood vessel carrying blood and oxygen to the brain gets blocked or ruptures, resulting in injury to the brain and stroke symptoms due to absence of blood flow and oxygen. Strokes can happen at any age, but nearly one-third of all strokes happen to people under age 65. Stroke is the fifth leading cause of death in the United States and a major cause of disability in adults. See Stroke Warning Signs for more information about stroke symptoms.
There are two main types of stroke:
An ischemic stroke is caused by blocked arteries, cutting off blood flow to the brain. More than 80% of all strokes are ischemic, but they can occur as a result of a number of causes:
- Heart disease: Blood clots can form in the heart as a result of heart disease such as an irregular heart rhythm, heart failure, or prior heart attack; when the blood clot leaves the heart it can travel to the brain and cause a stroke.
- Atherosclerosis/hardening of the arteries: High blood pressure, high cholesterol, and diabetes can lead to damage to the blood vessels in the neck and brain in the form of atherosclerosis, or hardening of the arteries. This injury to the blood vessels leads to blockage of blood flow to the brain, causing a stroke.
- Blood clotting disorders: Problems that cause formation of excess blood clots can lead to stroke when blood clots form within the brain.
- Inflammation and infection: Both infections and autoimmune disease when the immune system attacks the body can lead to stroke.
Not all strokes are caused by blockages in the arteries. Less than 20 percent occur when a blood vessel ruptures in or near the brain, called a hemorrhagic stroke. There are two kinds of hemorrhagic stroke:
- Subarachnoid hemorrhage: A very serious type of stroke that occurs when a blood vessel on the surface of the brain ruptures and bleeds into the space between the brain and the skull. A ruptured brain aneurysm or arteriovenous malformation (AVM) can be the cause. An aneurysm is a blood-filled pouch that balloons out from an artery wall, and can be inherited. An AVM is a collection of arteries and veins abnormally formed at birth.
- Intracerebral hemorrhage: A blood vessel bleeds into the tissue deep within the brain. High blood pressure or aging blood vessels are the main causes of this type of stroke.
What is a TIA?
A transient ischemic attack (TIA) occurs when a blood clot blocks an artery for a short time. The symptoms of TIA are the same as the stroke symptoms but last only for a few minutes or hours. A TIA is a sign that you are at risk for a major stroke in the next few days or weeks. If you have symptoms of a TIA call 911 immediately.