A stroke or “brain attack” occurs when a blood clot blocks an artery (a blood vessel that carries blood from the heart to the body) or a blood vessel (a tube through which the blood moves through the body) breaks, interrupting blood flow to an area of the brain. When either of these things happen, brain cells begin to die and brain damage occurs.When brain cells die during a stroke, abilities controlled by that area of the brain are lost. These abilities include speech, movement and memory. How a stroke patient is affected depends on where the stroke occurs in the brain and how much the brain is damaged.

For example, someone who has a small stroke may experience only minor problems such as weakness of an arm or leg. People who have larger strokes may be paralyzed on one side or lose their ability to speak. Some people recover completely from strokes, but more than 2/3 of survivors will have some type of disability.

Types of Stroke

Ischemic Stroke

In everyday life, blood clotting is beneficial. When you are bleeding from a wound, blood clots work to slow and eventually stop the bleeding. In the case of stroke, however, blood clots are dangerous because they can block arteries and cut off blood flow, a process called ischemia. An ischemic stroke can occur in two ways: embolic and thrombotic strokes

Embolic Stroke

In an embolic stroke, a blood clot forms somewhere in the body (usually the heart) and travels through the bloodstream to your brain. Once in your brain, the clot eventually travels to a blood vessel small enough to block its passage. The clot lodges there, blocking the blood vessel and causing a stroke. The medical word for this type of blood clot is embolus.

Thrombotic Stroke

In the second type of blood-clot stroke, blood flow is impaired because of a blockage to one or more of the arteries supplying blood to the brain. The process leading to this blockage is known as thrombosis. Strokes caused in this way are called thrombotic strokes. That’s because the medical word for a clot that forms on a blood-vessel deposit is thrombus.

Blood-clot strokes can also happen as the result of unhealthy blood vessels clogged with a buildup of fatty deposits and cholesterol. Your body regards these buildups as multiple, tiny and repeated injuries to the blood vessel wall. So your body reacts to these injuries just as it would if you were bleeding from a wound;it responds by forming clots. Two types of thrombosis can cause stroke: large vessel thrombosis and small vessel disease (or lacunar infarction.)

Large Vessel Thrombosis

Thrombotic stroke occurs most often in the large arteries, so large vessel thrombosis is the most common and best understood type of thrombotic stroke. Most large vessel thrombosis is caused by a combination of long-term atherosclerosis followed by rapid blood clot formation. Thrombotic stroke patients are also likely to have coronary artery disease, and heart attack is a frequent cause of death in patients who have suffered this type of brain attack.

Small Vessel Disease/Lacunar Infarction

Small vessel disease, or lacunar infarction, occurs when blood flow is blocked to a very small arterial vessel. The term’s origin is from the Latin word lacuna which means hole, and describes the small cavity remaining after the products of deep infarct have been removed by other cells in the body. Little is known about the causes of small vessel disease, but it is closely linked to hypertension (high blood pressure).

Hemorrhagic Stroke

Strokes caused by the breakage or “blowout” of a blood vessel in the brain are called hemorrhagic strokes. The medical word for this type of breakage is hemorrhage. Hemorrhages can be caused by a number of disorders which affect the blood vessels, including long-standing high blood pressure and cerebral aneurysms. An aneurysm is a weak or thin spot on a blood vessel wall. These weak spots are usually present at birth. Aneurisms develop over a number of years and usually don’t cause detectable problems until they break. There are two types of hemorrhagic stroke subarachnoid and intracerebral.

In an intracerbral hemmorrhage, bleeding occurs from vessels within the brain itself. Hypertension (high blood pressure) is the primary cause of this type of hemorrhage.

In a subarachnoid hemmorrhage(SAH), an aneurism bursts in a large artery on or near the thin, delicate membrane surrounding the brain. Blood spills into the area around the brain which is filled with a protective fluid,causing the brain to be surrounded by blood-contaminated fluid.

Signs

The American Stroke Association wants you to learn the warning signs of stroke:

Sudden numbness or weakness of the face, arm or leg, especially on one side of the body
Sudden confusion, trouble speaking or understanding
Sudden trouble seeing in one or both eyes
Sudden trouble walking, dizziness, loss of balance or coordination
Sudden, severe headache with no known cause

Be prepared for an emergency.

Keep a list of emergency rescue service numbers next to the telephone and in your pocket, wallet or purse.
Find out which area hospitals are primary stroke centers that have 24-hour emergency stroke care.
Know (in advance) which hospital or medical facility is nearest your home or office.

Take action in an emergency.

Not all the warning signs occur in every stroke. Don’t ignore signs of stroke, even if they go away!
Check the time. When did the first warning sign or symptom start? You’ll be asked this important question later.
If you have one or more stroke symptoms that last more than a few minutes, don’t delay! Immediately call the emergency medical service.
If any of the symptoms mentioned above suddenly appear, emergency medical attention should be sought. The sooner treatment is started, the better the eventual outcome will be.. The family doctor and/or neurologist should also be contacted. However, the first priority is ensuring that the ambulance arrives as soon as possible. The affected person should lie flat to promote an optimal blood flow to the brain. If drowsiness, unresponsiveness, or nausea are present, the person should lie on one side to prevent choking on his/her vomit. Although aspirin plays a major role in stroke prevention , once the symptoms of a stroke begin, it is generally recommended that additional aspirin not be taken until the patient receives medical attention. If stroke is of the bleeding type, aspirin could theoretically make matters worse.

Risk factors

Anybody can have a stroke, but certain factors place you at higher risk. Some factors that increase the risk of stroke cannot be changed, while others are linked to lifestyle and are, therefore, under your control.

Risk factors that cannot be changed:

Age — The older a person gets, the greater the risk of stroke.
Sex — Men are more likely to have a stroke than women. But after menopause, a woman’s risk of stroke rises significantly.
Family history - Having a parent, grandparent, or sibling who has had a stroke, puts you at greater risk yourself.
Race — African Americans have a greater risk of stroke than Caucasians. This is related to an increased risk of high blood pressure, obesity, and diabetes in African Americans.
Heart attack - If you have had a heart attack in the past, you are more likely to have a stroke than someone who has not had a heart attack.
A history of migraine headaches — Recent studies indicate that people who experience migraines may be at higher risk for ischemic stroke.
A prior stroke — If you have had a stroke, you are at increased risk for another.
Sickle cell anemia - people with this condition are at risk for stroke at a younger age.
Berry aneurysms — These are small, sac-like areas within the wall of an artery in the brain with which some people are born. They occur most often at the junctures of vessels at the base of the brain. Berry aneurysms may rupture without warning, causing bleeding within the brain.

Risk factors that can be changed with medical treatment:

High blood pressure — High blood pressure has no symptoms, so regular blood pressure checks are important. The condition can be easily and successfully controlled with medication.
High blood cholesterol levels — Studies have shown that lowering cholesterol levels by changing your lifestyle and taking medication can reduce the risk of stroke by as much as 30%. Keeping cholesterol low can reduce the risk of blood clots and plaque buildup within the walls of arteries in the brain.
TIAs, or “mini-strokes” — A surprising number of people ignore the symptoms of TIAs, which are warning signs that a stroke may be about to happen. In fact, 50% of people who have had a TIA suffer a stroke within one year. It is very important to seek medical attention for these symptoms because if you have had a TIA, there are definite steps you can take to help prevent a major stroke. Doctors prescribe blood thinners such as aspirin, warfarin, or other drugs to prevent blood clots if you have had a TIA.
Cardiovascular disease — Certain disorders of the heart and/or blood vessels, such as atherosclerosis (plaque build up in artery walls) and atrial fibrillation (an abnormal heart rhythm), can produce blood clots that may break loose and travel to the brain. These conditions are also treated with blood thinners to reduce risk of stroke.
Diabetes — People with diabetes mellitus are more at risk. It is important to note that Type 2 diabetes (often called adult onset) is highly influenced by certain lifestyle factors, particularly diet and excess weight.
Blood clotting disorders - people who form blood clots more easily, called hypercoagulable conditions, are at greater risk for stroke. Hypercoagulable states are also treated with blood thinners such as warfarin in order to try to prevent stroke and other complications.
Sleep apnea - people with sleep apnea have three to six times the risk of stroke compared to people who do not have this disorder. This condition, defined as cessation of breathing many times throughout the night, is generally treatable by losing weight and/or using a special device called a CPAP machine.

Risk factors that can be changed by lifestyle modifications:

Cigarette smoking — Cigarette smoking has been linked to heart attacks, strokes, artery disease in the legs, and lung cancer. Nicotine raises blood pressure, carbon monoxide reduces the amount of oxygen the blood can carry to the brain, and cigarette smoke makes the blood thicker and more likely to clot. It is never too late to give up smoking!
Smoking and birth control pills — Research has proven that smoking and taking birth control pills significantly increases a woman’s risk for stroke. Together, they can cause blood clots to form. Women who take birth control pills should not smoke!
Drinking large amounts of alcohol — Frequent intoxication can make a person more likely to experience bleeding in the brain. Also, alcohol in large amounts can raise blood pressure.
Obesity — Being overweight increases your risk of having a stroke, along with other health problems.
Lack of exercise –Moderate exercise can help keep blood pressure and cholesterol levels within normal ranges.
Poor diet — A diet high in fat can cause conditions within the body, such as obesity, type 2 diabetes, and high cholesterol, that contribute to a greater risk of stroke.
Stress - Ongoing stress can raise blood pressure. Plus, not dealing well with stress can contribute to unhealthy habits such as smoking and overeating. Finding healthy ways to handle stress is important.

Other factors that may put you at increased risk for stroke include pregnancy, infection or inflammation, gum disease, and high homocysteine levels. Homocysteine is an amino acid that rises in the body if you have low levels of vitamins B6, B12, B9 (folic acid), and betaine.

Medications for Stroke prevention

Certain medications have been shown to reduce the risk of stroke. These drugs, which aim to prevent the formation of dangerous blood clots, fall under two major categories:

Antiplatelet agents — These include aspirin and stronger prescription drugs like ticlopidine and clopidogrel. These drugs help keep tiny blood cells called “platelets” from clumping together in the bloodstream. When a blood vessel is damaged or injured, platelets will migrate to the area to begin a healing process. However, large numbers of platelets can clump together and form a clot that plugs up an artery. Antiplatelet agents help prevent this clumping.
Anticoagulants — These drugs also prevent clots, but are much stronger than antiplatelet agents. Common anticoagulants are warfarin and heparin (generally given at the hospital intravenously - that is through injection into a vein).

Sources: Medicine Net, Stroke