Each side of the neck has an artery called the common carotid. Each common carotid splits into two branches -- the internal branch, which brings oxygen-rich blood to the brain, and the external branch, which brings blood to the face.

Blockage of the internal carotid artery can reduce blood supply to the brain, causing a stroke. When the internal carotid arteries become blocked by fat and cholesterol build-up of atherosclerosis (also called plaque) can result.

Over time, the plaque slowly begins to block the flow of blood. The plaque itself may block the artery enough to cause a stroke. In addition, the plaque often causes the blood to flow abnormally, which leads to a blood clot. A clot can stay at the site of narrowing and prevent blood flow to all of the smaller arteries it supplies. This type of clot, which doesn't travel, is called a thrombus. In other cases, the clot can travel and wedge into a smaller vessel. A clot that travels is called an embolism.

If you develop a thrombus in the internal carotid artery or an embolism in a smaller blood vessel, you may experience symptoms such as blurred vision, slurred speech, or weakness (all signs of stroke).

By restoring adequate blood flow to the internal carotid artery, strokes can be prevented. This may be accomplished either by a surgery called endarterectomy or a procedure known as angioplasty with stent placement. Traditionally used for the heart, this latter procedure is now being used on blood vessels to the brain as well. Stent placement is an alternative to surgery that enlarges the blockage in the artery. This new technique must only be performed by an experienced physician.

During the procedure, there are steps the surgeon takes to reduce the risk of stroke from the operation. These include shunting (using a plastic tube to re-route blood flow to the brain), EEG monitoring, or even doing the operation under local anesthetic so the patient can talk to the surgeon. Usually, however, general anesthesia is used, which allows the patient to be unconscious and pain free.

The procedure may be used to treat symptoms of carotid artery blockage, such as:

• Weakness of the arm, leg, or face on one side of the body
• Inability to move the arm, leg, or face on one side of the body (paralysis)
• Numbness, tingling, or noticeable change in the sensation of the arm, leg, or face on one side of the body
• Difficulty swallowing
• Loss of all or part of vision (blindness) in one eye
• Slurred speech or inability to speak
• Dizziness (vertigo)
• Confusion, fainting, or coma
• Stroke with complete recovery (TIA)
• Severe blockage without any symptoms at all

Seek urgent medical attention if you experience these symptoms. The symptoms may be permanent, but even if they occur transiently and then get better by themselves (TIA, or transient ischemic attack), they still might be a sign of a serious problem.

Surgery should also be done for those who have carotid artery blockages which cut off between 75-99% of blood flow through this major artery. Large studies have shown that for people with such severe blockages, even if they have no symptoms at all, the risk of stroke is reduced with surgery.

If the blockage is complete (100%), however, surgery will not be performed because the risk of stroke and significant brain damage from the procedure is too great.

X-ray studies using special dyes (carotid angiogram) can show the degree of blockage of the carotid arteries. Other studies that can visualize blockages in the carotid arteries are ultrasound and magnetic resonance angiography (MRA).

The risks for any anesthesia are:

• Reactions to medications
• Problems breathing

The risks for any surgery are:

• Bleeding
• Infection

Additional risks of carotid surgery include:

• Blood clots
• Brain damage
• Strokes (1-3% in the hands of an experienced surgeon)
• Heart attacks

After surgery, you are usually observed overnight to watch for any signs of bleeding, stroke, or compromised blood flow to the brain. However, there is a recent trend to send the patient home the same day, if the operation is done early and the patient is doing well.

Erratic blood pressure (requiring monitoring in an intensive care unit) is relatively common, tends to improve within 24 hours, and should not be a cause for concern.