A stroke, or cerebrovascular accident (CVA), occurs when blood supply to part of the brain is disrupted, causing brain cells to die. When blood flow to the brain is impaired, oxygen and glucose cannot be delivered to the brain.

Blockage of an artery
The blockage of an artery in the brain by a clot (thrombosis) is the most common cause of a stroke. The part of the brain that is supplied by the clotted blood vessel is then deprived of blood and oxygen. As a result of the deprived blood and oxygen, the cells of that part of the brain die.

Embolic stroke
Another type of stroke may occur when a blood clot or a piece of atherosclerotic plaque (cholesterol and calcium deposits on the wall of the inside of the heart or artery) breaks loose, travels through open arteries, and lodges in an artery of the brain. When this happens, the flow of oxygen-rich blood to the brain is blocked and a stroke occurs.

Cerebral hemorrhage
A cerebral hemorrhage occurs when a blood vessel in the brain ruptures and bleeds into the surrounding brain tissue. A cerebral hemorrhage (bleeding in the brain) can cause a stroke by depriving blood and oxygen to parts of the brain.

Subarachnoid hemorrhage
In a subarachnoid hemorrhage, blood accumulates in the space beneath the arachnoid membrane that lines the brain. The blood originates from an abnormal blood vessel that leaks or ruptures.
Vasculitis
Another rare cause of stroke is vasculitis, a condition in which the blood vessels become inflamed.

Migraine headache
There appears to be a very slight increased occurrence of stroke in people with migraine headache. The mechanism for migraine or vascular headaches includes narrowing of the brain blood vessels. Some migraine headache episodes can even mimic stroke with loss of function of one side of the body or vision or speech problems.

When brain cells are deprived of oxygen, they cease to perform their usual tasks. The symptoms that follow a stroke depend on the area of the brain that has been affected and the amount of brain tissue damage. Small strokes may not cause any symptoms, but can still damage brain tissue. These strokes that do not cause symptoms are referred to as silent strokes. According to The U.S. National Institute of Neurological Disorders and Stroke (NINDS), these are the five major signs of stroke:

1.    Sudden numbness or weakness of the face, arm or leg, especially on one side of the body. The loss of voluntary movement and/or sensation may be complete or partial. There may also be an associated tingling sensation in the affected area.

2.    Sudden confusion or trouble speaking or understanding. Sometimes weakness in the muscles of the face can cause drooling.

3.    Sudden trouble seeing in one or both eyes

4.    Sudden trouble walking, dizziness, loss of balance or coordination

5.    Sudden, severe headache with no known cause

A stroke is a medical emergency. Anyone suspected of having a stroke should be taken to a medical facility immediately for evaluation and treatment. Initially, the doctor takes a medical history from the patient if he/she is alert or others familiar with the patient if they are available, and performs a physical examination. If a person has been seeing a particular doctor, it would be ideal for that doctor to participate in the assessment. Previous knowledge of the patient can improve the accuracy of the evaluation.

Computerized tomography: In order to help determine the cause of a suspected stroke, a special x-ray test called a CT scan of the brain is often performed. A CT scan is used to look for bleeding or masses within the brain

MRI scan: Magnetic resonance imaging (MRI) uses magnetic waves rather than x-rays to image the brain. The MRI images are much more detailed than those from CT, but this is not a first line test in stroke. While a CT scan may be completed within a few minutes, an MRI may take more than an hour to complete. An MRI may be performed later in the course of patient care if finer details are required for further medical decision making.

Computerized tomography with angiography: Using dye that is injected into a vein in the arm, images of the blood vessels in the brain can give information regarding aneurysms or arteriovenous malformations. As well, other abnormalities of brain blood flow may be evaluated.

Conventional angiogram: An angiogram is another test that is sometimes used to view the blood vessels. A long catheter tube is inserted into an artery (usually in the groin area) and dye is injected while x-rays are simultaneously taken. While an angiogram delivers some of the most detailed images of the blood vessel anatomy, it is also an invasive procedure and is used only when absolutely necessary.

Carotid Doppler ultrasound: A carotid Doppler ultrasound is a non-invasive (without injections or placing tubes) method that uses sound waves to screen for narrowings and decreased blood flow in the carotid artery (the major artery in the neck that supplies blood to the brain).

Heart tests: Certain tests to evaluate heart function are often performed in stroke patients to search for the source of an embolism.

Blood tests: Blood tests such as a sedimentation rate and C-reactive protein are done to look for signs of inflammation that can suggest inflamed arteries. Certain blood proteins that can increase the chance of stroke by thickening the blood are measured. These tests are performed to identify treatable causes of a stroke or to help prevent further injury.

Tissue plasminogen activator (TPA)
There is opportunity to use alteplase (TPA) as a clot-buster drug to dissolve the blood clot that is causing the stroke. There is a narrow window of opportunity to use this drug. The earlier that it is given, the better the result and the less potential for the complication of bleeding into the brain. Present American Heart Association guidelines recommend that if used, TPA must be given within three hours after the onset of symptoms. Normally, TPA is injected into a vein in he arm. The time frame for use can be extended to six hours if it is dripped directly into the blood vessel that is blocked. This is usually performed by an interventional radiologist, and not all hospitals have access to this technology. For posterior circulation strokes that involve the vertebrobasilar system, the time frame for treatment with TPA may be extended even further to 18 hours

Heparin and aspirin
Drugs to thin the blood (anticoagulation; for example, heparin) are also sometimes used in treating stroke patients in the hopes of improving the patient's recovery. It is unclear, however, whether the use of anticoagulation improves the outcome from the current stroke or simply helps to prevent subsequent strokes. In certain patients, aspirin given after the onset of a stroke does have a small, but measurable effect on recovery. The treating doctor will determine the medications to be used based upon a patient's specific needs.

Managing other Medical Problems
Blood pressure and cholesterol control are key to prevention of future stroke events. In transient ischemic attacks, the patient may be discharged with medications even if the blood pressure and cholesterol levels are acceptable. In an acute stroke, blood pressure will be tightly controlled to prevent further damage. In patients with diabetes, the blood sugar (glucose) level is often elevated after a stroke. Controlling the glucose level in these patients may minimize the size of a stroke. Finally, oxygen may administered to stroke patients when necessary.

Rehabilitation
When a patient is no longer acutely ill after a stroke, the healthcare staff focuses on maximizing the patient's functional abilities. The rehabilitation process can include some or all of the following:
1.    Speech therapy to relearn talking and swallowing;
2.    Occupational therapy to regain dexterity in the arms and hands;

3.    Physical therapy to improve strength and walking; and
4.    Family education to orient them in caring for their loved one at home and the challenges they will face.

If any of the symptoms mentioned above suddenly appear, emergency medical attention should be sought. 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 be placed in the rescue position on their side to prevent choking should vomiting occur.
• 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.

Depending on how long the brain suffers a lack of blood flow, a stroke can sometimes cause temporary or permanent disabilities. Stroke complications differ depending what part of the brain was affected and may include:

• Paralysis or loss of muscle movement: Sometimes, a lack of blood flow to the brain can cause a person to become paralyzed on one side of the body, or lose control of certain muscles, such as those on one side of the face. With physical therapy, you may see improvement in muscle movement or paralysis.

• Difficulty talking or swallowing: A stroke may cause a person to have less control over the way the muscles in the mouth move, making it difficult to talk, swallow or eat. A person may also have difficulty speaking because a stroke has caused aphasia, a condition in which a person has difficulty expressing thoughts through language. Therapy with a speech and language pathologist may improve this disability.

• Memory loss or troubles with understanding: It's common that people who suffer strokes have some memory loss. Others may develop difficulty understanding concepts. This complication may improve with rehabilitation therapies.
• Pain: Some people who have a stroke may have pain, numbness, or other strange sensations in parts of their body affected by stroke. For example, if a stroke causes you to lose feeling in your left arm, you may have an uncomfortable tingling sensation in that arm. You may also be sensitive to temperature changes, especially extreme cold. This is called central stroke pain or central pain syndrome (CPS). This complication may improve with time, but because the pain is caused by a problem in the brain instead of a physical injury, there are few medications to treat CPS.

Methods of prevention of Stroke mentioned in various sources includes those listed below. This prevention information is gathered from various sources, and may be inaccurate or incomplete. None of these methods guarantee prevention of Stroke.

• Lifestyle changes

o    Healthy diet
o    Control blood pressure
o    Control diabetes
o    Control stress
o    Control cholesterol
o    Regular exercise
o    Physical activity
o    Quit smoking
o    Seek treatment for a TIA

• Antiplatelet agents

o    Aspirin therapy

• Anticoagulants

o    Warfarin

• Preventive surgery

o    Carotid endarterectomy - removal of arterial deposits in the neck.