A stroke is caused by a blocked or bleeding artery in the brain. Most strokes are due to blocked arteries that supply blood to the brain and are called ischemic strokes. Strokes due to bursting of brain blood vessels are called hemorrhagic strokes. Intracerebral hemorrhage is caused by bleeding into the brain itself, while subarachnoid hemorrhage is due to bleeding around the base of the brain. A TIA (transient ischemic attack) is caused by a temporary blockage of blood flow to a blood vessel to the brain lasting less than 24 hours.Another, rarer, form of stroke can occur when a vein (that drains blood out of the brain) is blocked. This is called a venous stroke.
Stroke Facts
Ischemic Stroke (non-hemorrhagic stroke)
Intracerebral Hemorrhage
Subarachnoid Hemorrhage
TIA (Transient Ischemic Attack)
Venous Stroke
Large Artery Stroke
Small Artery Stroke (Lacunar Stroke)
Embolic Stroke
- There are more than 700,000 strokes each year in the U.S.
- 28% of strokes occur in people under age 65
- Over the age of 55, stroke risk doubles every 10 years
- There are more than 4 million stroke survivors alive today in the U.S.
- Stroke is the leading cause of long-term disability in the U.S.
- Stroke is the 3rd largest cause of death in the U.S., ranking behind diseases of the heart and cancer
- Stroke kills more women than breast cancer
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This type of stroke is caused by blockage of a blood vessel (artery) supplying the brain. Brain tissue that no longer receives its blood supply can die within a few hours unless something is done to stop the damage (see Getting Treatment for a Stroke).
Ischemic stroke represents about 80% of all strokes in the U.S. The blockage of arteries can occur in large arteries in the neck or the base of the brain, or in small arteries inside the brain itself. A blood clot can form in the brain or it can form elsewhere and be carried to the brain by an artery. This latter type of stroke is called an embolic stoke.
As many as 20% of victims die in the month after having an ischemic stroke and the majority of survivors have some long term disability.
There are many conditions that increase a person's risk of ischemic stroke. These include high blood pressure, smoking, heart diseases, diabetes, narrowing of arteries supplying the brain, high cholesterol and an unhealthy lifestyle. Treating these conditions can decrease stroke risk (see Preventing a Stroke)
The picture below shows a number of the causes of ischemic stroke. You can click on different parts of the picture to get further information about the specific causes.
Subtypes of Ischemic Stroke
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This type of stroke is caused by the bleeding of a blood vessel within the brain. As a result of the bleeding a blood clot forms in the brain, which puts pressure on the brain and damages it.
Although intracerebral hemorrhage is less common than ischemic stroke, it is more serious, with up to 40% of patients dying in the first month. The most common cause of intracerebral hemorrhage is high blood pressure. Another cause, especially in younger people with intracerebral hemorrhages, is abnormally formed blood vessels in the brain (vascular malformations or aneurysms).
Treatment for intracerebral hemorrhage is limited but may include emergency surgery.
This is a picture of the most common form of intracerebral hemorrhage.
This is a picture of vascular malformation that can also lead to an intracerebral hemorrhage.
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Subarachnoid hemorrhage results from the bleeding of an artery around the base of the brain. It is the least common stroke type, accounting for about 5% of all strokes. The most frequent cause of subarachnoid hemorrhage is bleeding from an aneurysm. An aneurysm is a weakening and ballooning of a short portion of an artery (similar to a bubble on the side of an old hose).
The factors that can increase a person’s risk of this type of stroke include high blood pressure, smoking, and a family history of burst aneurysms.
Treatment for subarachnoid hemorrhage may include emergency surgery.
This is a picture of a bleeding aneurysm that has led to a subarachnoid hemorrhage.
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A TIA is like a temporary ischemic stroke. An artery is temporarily blocked, preventing blood from reaching a part of the brain. This lack of blood flow causes that part of the brain to stop functioning.
The symptoms of a TIA are the same as symptoms of an ischemic stroke. In a TIA, the blood vessel opens up again, before any permanent injury to the brain occurs and the patient recovers completely. Most TIA symptoms last less than 30 minutes.
People who suffer TIAs are at HIGH RISK OF STROKE soon thereafter. A TIA should lead to immediate medical evaluation to determine its cause and a treatment plan to prevent a stroke from following soon after.
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Venous stroke is caused by a blood clot blocking the veins that allow blood to drain out of the brain. (All other strokes are caused by abnormalities of arteries carrying blood to the brain). Venous stroke causes a “back pressure” effect that leads to the stroke. These strokes can be either ischemic or hemorrhagic.
Some causes of venous stroke include severe dehydration, severe infection in the sinuses of the head and medical or genetic conditions that increase a person’s tendency to form blood clots.
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Large Artery Strokes are a form of ischemic strokes. They occur when the blocked artery causing the stroke is one of the larger arteries of the brain. Because these larger arteries supply large portions of brain, these strokes are usually more severe than those due to blockage of small arteries.
The large arteries that can be blocked include:
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Left Internal Carotid Artery or Middle Cerebral Artery: These arteries supply blood to much of the left side of the brain. When these arteries are blocked, symptoms might include right body weakness, trouble communicating and right body numbness.
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Right Internal Carotid Artery or Middle Cerebral Artery. These arteries supply blood to much of the right side of the brain. When these arteries are blocked, symptoms might include left body weakness and left body numbness.
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Left Vertebral Artery, Right Vertebral Artery, or Basilar Artery. These arteries supply blood to much of the base of the brain (the brainstem) and the back of the brain. When these arteries are blocked, symptoms might include weakness or numbness on either side of the body, nausea, vomiting, unsteadiness of walking, severe dizziness (vertigo), or coma.
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Aortic arch atherosclerosis is the buildup of cholesterol and other material on the wall of the aorta (the largest artery in the body that leads out of the heart) that can lead to blood clot formation that can break off and cause stroke in any of the above large arteries.
Some of the major risk factors for this type of stroke include hypertension, diabetes, smoking and high cholesterol levels. Once a large artery stroke has occurred, steps should be taken to help prevent further strokes.
The picture below shows a blood clot in a large artery of the brain (middle cerebral artery) leading to an injured area of brain ("infarct"), the ischemic stroke.
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Small Artery Strokes are also ischemic strokes. They are caused by blockage of one of the small arteries that branch off of the larger arteries. These small arteries penetrate deep into the brain, and can cause any of the symptoms of ischemic stroke. This type of stroke tends to have a better outcome, because the blockage of a smaller artery usually leads to a smaller amount of brain damage.
Some of the major risk factors for this type of stroke include hypertension, diabetes and smoking. Once a small artery stroke has occurred, steps should be taken to help prevent further strokes.
This is a picture of a two small artery strokes.
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Embolic strokes are also ischemic strokes. They are caused by blockage of one of the arteries to the brain by a blood clot that has formed elsewhere (usually in the heart), broken free, and traveled to the brain as an “embolus”. Sometimes the clot can form in the aorta, which is the largest artery in the body. These clots can travel to any artery in the brain, but more often they block the larger arteries, causing more severe strokes. Embolic strokes can cause any of the typical symptoms of ischemic stroke.
Some of the major risk factors for this type of stroke include an irregular heart beat (atrial fibrillation), a heart attack (myocardial infarction), heart failure or a small hole in the heart called a PFO (Patent Foramen Ovale). Once an embolic stroke has occurred, steps should be taken to help prevent further strokes.
Link back to Large Artery Stroke for picture of what an embolic stroke looks like.
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