Stroke

Stroke:Occurs when the blood supply to part of the brain is suddenly interrupted, usually by a clot, or when a blood vessel in the brain bursts, spilling blood into the spaces surrounding brain cells. Strokes caused by blood-supply interruption—ischemic strokes—comprise 80 percent of cases.

A stroke—also referred to as a brain attack or apoplexy—occurs when a part of the brain is injured by a disturbance to its blood supply.
There are two types of stroke. An ischemic stroke, or cerebral infarction, occurs when the flow of blood through an artery supplying part of the brain is suddenly interrupted, usually by a clot. A hemorrhagic stroke, or cerebral or subarachnoid hemorrhage, occurs when a blood vessel in the brain bursts, spilling blood into the substance of the brain or into the spaces surrounding the brain.
The term "brain attack" is becoming increasingly common to describe this condition—and it makes sense. A person suffering a loss of blood flow to the heart is said to be having a heart attack, so a person with a loss of blood flow to the brain or sudden bleeding in the brain is having a "brain attack." Deprived of oxygen, nerve cells (neurons) in the affected area of the brain can't function and die within minutes. And when nerve cells can't function, the part of the body controlled by these cells can't function either. Although the healing process can help some patients improve after a stroke, some devastating effects of stroke are often permanent; dead brain cells aren't replaced.
Strokes affect different people in different ways, depending on the type of stroke, the area of the brain affected and the extent of the brain injury. Brain injury from a stroke can affect speech and language, motor activity, cognitive ability, behavior, memory and emotions. Paralysis or weakness on one side of the body is common. Stroke is the leading cause of serious adult disability.
Each year, about 46,000 more women than men have a stroke. Of every five deaths from stroke, three occur in women and two in men. This is because the average life expectancy for women is greater than for men, and the highest rates for stroke are in the oldest age groups.
Stroke is often deadly: the condition kills nearly 157,000 Americans each year, accounting for one in 15 deaths. Stroke ranks third after heart disease and cancer as a major cause of death in the United States.
The most important risk factors for stroke are hypertension, heart disease, diabetes and cigarette smoking. Other factors that increase your risk of having a stroke include heavy alcohol consumption, high cholesterol levels, illicit drug use and genetic or congenital conditions (particularly vascular abnormalities).
Atrial fibrillation, a heart rhythm disturbance that causes the small chambers of the heart to beat irregularly allowing blood clots to form, is another risk factor. It is particularly common in elderly people; it increases markedly in people after age 65, and it affects about 10 percent of those 80 and older. It may also occur in younger women, particularly in association with hyperthyroidism or Graves' disease. However, you can have a stroke at any age. More than a quarter of stroke victims are under 65.
Stroke seems to run in some families, particularly those in which family members have had heart attacks before age 50. These families have a tendency for premature atherosclerosis, or "hardening of the arteries," and may share a genetic predisposition for high blood pressure, elevated cholesterol or diabetes, all of which are risk factors for stroke. Of course, shared lifestyle habits of poor diet, lack of exercise and tendency to smoke or drink may also be a factor in a family history of stroke.
African Americans are more likely to have strokes than Caucasians, but after age 55 the risk of death from stroke is the same for Caucasians as for African Americans. Researchers note that African Americans have higher rates of stroke risk factors, including high blood pressure, cigarette smoking, diabetes and sickle cell anemia. It is not clear whether the increased risk of stroke in minority populations is related to increased prevalence of these risk factors, or to other factors. Hispanic Americans and Native Americans also have an increased risk of stroke, which may also relate to their higher rates of stroke risk factors, including diabetes and hypertension.
Some risk factors for stroke apply only to women, including pregnancy, childbirth and menopause. These risk factors are tied to hormonal fluctuations, changes in blood volume, tendency to form blood clots, and other physical changes that affect a woman in different stages of life.
Pregnancy increases the risk of stroke as much as three to 13 times, causing strokes in approximately eight in 100,000 women. However, since the risk of stroke in women of childbearing age is very small to begin with, a moderate increase in risk during pregnancy is still a relatively small risk. Nonetheless, 25 percent of those strokes end in death.
Having already had a stroke puts you at higher risk for another one. Recurrent stroke is frequent: about 14 percent of people who recover from a first stroke will have another one within a year. The risk of severe disability or death from stroke increases with each stroke recurrence, and the risk of recurrence is greatest soon after a stroke. According to the National Institutes of Health, about three percent of stroke patients will have another stroke within 30 days of their first one, and one-third of recurrent strokes take place within two years of the first stroke. The underlying cause of the stroke influences the risk of recurrence, however.
An additional risk factor applies only to people subject to hemorrhagic stroke. A person with an abnormality of the brain blood vessels, such as an aneurysm or arteriovenous malformation (AVM), is at increased risk for hemorrhagic stroke. Aneurysms are weakened blood vessels that balloon out on the blood vessel wall, while AVMs are a tangle of defective blood vessels and capillaries in the brain. Both have areas of thin walls and are more likely to rupture.
Types of StrokeStroke is actually a collective term for many different subtypes of brain injuries:
Ischemic strokes are caused by blood clots. There are two types of ischemic stroke:
Embolic stroke means a blood clot forms somewhere in the body (either in the heart or in one of the arteries in the chest or neck that supply the brain) and travels through the bloodstream to your brain.
Thrombotic stroke means the blood flow ceases because of a blockage of one or more of the arteries supplying blood to the brain or within the brain itself.
Hemorrhagic stroke results when a blood vessel bursts in the brain. Two types of hemorrhagic stroke include:
Intracerebral hemorrhage occurs when vessels bleed within the brain itself
Subarachnoid hemorrhage is usually caused by the rupture of an aneurysm or a malformation of blood vessels on or near the thin, delicate membrane surrounding the brain.
Clotting is a necessary function; it stops bleeding and allows repair of damaged areas of arteries or veins. However, when arteries are damaged by atherosclerosis ("hardening of the arteries"), the lining of the artery is injured and cholesterol components seep into the wall of the blood vessel.
This sets up an inflammatory response within the vessel wall and ultimately forms a plaque. Plaque rupture attracts blood-clotting factors that can interfere with blood flow to the brain. A thrombotic stroke or cerebral thrombosis is caused by thrombosis, the formation of a blood clot on top of an atherosclerotic plaque, which grows large enough to block blood flow. Atherosclerotic plaques can start to develop in young adulthood but may take several decades to produce stroke symptoms. Atherosclerosis progression is accelerated by conditions such as hypertension, diabetes, smoking and hypercholesterolemia.
A clot can also form in another part of the body, such as the heart, and travel through blood vessels and become wedged in a brain artery. This free-roaming clot is called an embolus. A stroke caused by an embolus is called an embolic stroke or a cerebral embolism.
A Transient ischemic attack (TIA), sometimes called a ministroke, starts just like a stroke, lasts several minutes and may leave no lasting damage. Recent evidence suggests that many patients with TIA actually do have small strokes: as many as one-third of those whose symptoms last less than an hour. But you can't ignore it—you have no way of telling if the episode will be a TIA or a full-blown stroke. And even if it is just a TIA, take heed: It can be a warning that you are at risk for a more serious stroke.
About one-third of the 50,000 Americans who have a TIA will have an acute stroke sometime in the future. In one study, 10 percent of those who had a TIA had a stroke within just 90 days, and half of those occurred within only 48 hours. Thus, the occurrence of a TIA should be taken very seriously, and you should seek medical attention immediately to prevent a disabling stroke.
Hemorrhagic stroke accounts for about 12 to 20 percent of all strokes and is more frequent among the young and people with high blood pressure. One common cause is a bleeding aneurysm (weak or thin spot on an artery wall). Over time, these weak spots stretch or balloon out under high pressure. The thin walls of these ballooning aneurysms can rupture and spill blood into the space surrounding brain cells.
Hemorrhage also can occur when arterial walls break open. Plaque-encrusted artery walls eventually lose their elasticity and become brittle, thin and prone to cracking. High blood pressure increases the risk that a brittle wall will give.
When an artery in the brain bursts, blood spews into the surrounding tissue. Brain neurons generally don't come into direct contact with blood; the contact upsets the blood supply and the delicate chemical balance neurons require to function. For people with hemorrhagic strokes, treatment is aimed at alleviating pressure on the brain and minimizing damage.
As the terms "brain attack" and "stroke" suggest, strokes strike suddenly. Symptoms include numbness or weakness of the face, arm or leg, especially on one side of the body; confusion; difficulty speaking or understanding speech; trouble seeing out of one or both eyes; dizziness, or loss of balance or coordination; or sudden, uncharacteristic, severe headache, which is most characteristic of bleeding. Since the symptoms appear suddenly and there is usually more than one, you can often distinguish stroke from other causes of dizziness or headache.
Brain cells die when they no longer receive oxygen and nutrients from the blood, but they also are damaged by sudden bleeding into or around the brain. When blood flow to the brain is interrupted, some brain cells die immediately, while others remain at risk for dying. That's why immediate treatment is critical.
If you experience the sudden onset of the worst headache in your life or a sudden onset of neurological symptoms, call 911 and get to a hospital immediately. Do not waste precious time by calling your health care professional and do not call a family member. These actions have been shown to cause unnecessary delays in treatment. The best action is to call 911. The most effective therapies must be administered fast—typically within three hours of when the stroke started.
Although some health care professionals suggest taking aspirin at the onset of a heart attack, it may not be the best home remedy for a stroke. This recommendation hinges on the type of stroke you suffer. Aspirin is helpful for plugged artery types of strokes, but if you take aspirin for a leaking artery type of stroke, it can make the situation worse. Don't take aspirin in a stroke situation without advice of a health care professional.