Each person has two main carotid arteries, one located on each side of the neck. The carotid arteries bring oxygenated nutrient rich blood from the heart to the head and brain. Each carotid artery divides into two main branches called the internal and external carotid arteries. The internal carotid artery is the main branch that supplies blood to the brain. Because it supplies blood to the brain, this is the more important of the two arteries. The external carotid artery supplies blood to the face and scalp.
Carotid artery disease results from build up of blockages on the inside of these arteries. These blockages, called plaques, form from excess buildup of cholesterol and other fats in the wall of the artery. This process is called atherosclerosis. Over time, plaque growth may limit circulation of blood to the brain. In the carotid arteries, plaques have to block the artery by 70 to 80 percent or more to disrupt blood flow and cause problems. Most often, large plaques form at or near the divisions in an artery. Atherosclerosis may affect any artery of the body, such as the arteries to the heart (coronary artery disease) or arteries to the legs (peripheral artery disease).
Carotid plaques may not cause any symptoms. However, the plaque can become irregular and fragile and may even rupture. When this happens, blood clots can form over the broken plaque. If the blood clot is big enough, blood flow to the brain can then be sufficiently impaired so that the individual may experience a stroke. Alternatively, parts of the plaque or blood clot can break off and travel to the brain. This is called an embolism and this may also result in a stroke. When these emboli are small, or when clots dissolve quickly, the event may be quickly reversible and is called a transient ischemic attack (TIA). Emboli can also originate from the heart or aorta and flow through the carotid artery into the smaller blood vessels in the brain.
What are the Symptoms?
Most people with carotid artery disease have no symptoms. A stroke is often the first symptom of the disease. Fortunately, however, many people with carotid artery disease are warned by a TIA. Whether a patient has warning symptoms depends mainly on the plaque surface and if it has become soft or cracked. However, the absence of TIA symptoms in a patient with known carotid artery disease does not mean that the disease should be ignored.
The classic symptoms of carotid artery disease-related stroke or TIA are:
- Weakness or numbness on one side of the face or body or in one arm or leg that comes on abruptly without apparent cause
- Inco-ordination of an one arm or leg;
- Loss of vision, blurred vision or double vision.
- Inability to pronounce words or speak clearly or understand speech.
- Crooked smile or other new facial asymmetry
If any of these symptoms are experienced, the person should seek immediate medical attention because they may be experiencing a stroke. Time is very important because life-saving treatments may be used if the patient is seen promptly. These medicines which are used to break up clots must typically be started within 3 hours of symptom onset.
If these symptoms clear within 60 minutes, and importantly, clear completely leaving no residual effects, they are called a transient ischemic attack or “TIA”. Because the symptoms are temporary, many patients dismiss them as being of little or no importance. However, they should always be considered potentially serious and should be reported promptly to a physician. TIA is an important warning sign, and it is wrong to assume that if the symptoms quickly stop by themselves that the event was of no importance. If these symptoms persist for longer than an hour, they may indicate that a stroke has occurred. The important thing is that you should not wait to see if they will clear by themselves. Some strokes will clear without specific treatment after a short interval of only a day or two. But these symptoms are still important indicators of an underlying serious problem that should be reported to a physician and investigated for cause.
Causes and Risk Factors
Atherosclerosis is by far the most common cause of carotid artery disease, although carotid aneurysm disease and other types of narrowing, such as fibromuscular dysplasia, also can occur less commonly. Plaque formation begins with injury to the inner lining of an artery caused by the physical forces of blood flow and millions of heartbeats over decades of time. Over many years, the plaque deposits grow, as cholesterol and other fatty (lipid) materials are added to the plaque.
The risk factors associated with atherosclerosis include:
Physicians can sometimes diagnose carotid artery disease after performing a careful medical history and physical examination, which includes listening to the person describe symptoms and listening to the person's carotid arteries with a stethoscope. While examining a person's carotid arteries with a stethoscope, physicians listen for a whooshing sound of the turbulent flow of blood. This whooshing sound is called a “bruit”. Bruits are not specific for carotid artery disease and can also be caused by narrowing in other arteries. Similar noises can be heard over the carotid arteries in patients with diseases of the heart valves. So although listening to the carotids can indicate artery disease, physicians use other tests to confirm the diagnosis.
One of the most common tests used to confirm a diagnosis of carotid artery disease is carotid ultrasound. This painless test allows physicians to estimate the approximate extent of any blockage inside the carotid arteries. Ultrasound will detect most serious cases of carotid artery disease, and physicians may not need to use other diagnostic tests.
Magnetic resonance angiography (MRA) is a type of magnetic resonance imaging, or MRI, that uses radio waves and magnetic fields to create highly detailed cross-sectional images of the body's structures. As with ultrasound procedures, this process is noninvasive and painless. However, MRA requires sophisticated equipment that is typically found only in hospitals.
During an MRA, a person lies on a table inside a donut-shaped machine for about 30 minutes while the machine makes images of the person's body. Occasionally, a contrast dye called gadolinium is used to make the arteries more visible.
In some patients, an MRI cannot be performed because they have a pacemaker or defibrillator. In these patients, computed tomography (CT scan) can be used.
Infrequently, an invasive test called an angiogram may need to be performed. This x-ray test involves placing a catheter into the carotid artery and injecting dye. The injected dye moves through the arterial system in the head and neck, and provides accurate pictures of the inside of the carotid arteries. The pictures are called angiograms, and are used to define the extent of carotid artery disease and decide on courses of treatment. This test allows your physician to carefully see the extent of narrowing of the carotid arteries.
Treatment decisions for carotid artery disease typically depend on the extent of atherosclerotic blockage in the carotids and symptoms that might signal unstable plaque increasing the risk of stroke.
Medications used to treat atherosclerosis and carotid artery disease include:
Platelets are tiny cells that circulate in the bloodstream and help clot blood by sticking to artery walls and to one another. Drugs such as aspirin, clopidogrel, and dipyridamole inhibit the clumping of platelets, reducing the formation of blood clots in the arteries, which can help lower the risk of a stroke.
Infrequently, drugs such as heparin and warfarin (Coumadin), may be used to treat carotid artery disease. These drugs also help block the formation of blood clots that may block an artery in the brain and cause a stroke.
Statins lower levels of harmful low-density lipoprotein (LDL) cholesterol by blocking the liver from manufacturing cholesterol. Improved cholesterol levels can reduce the chance that plaque will grow or rupture.
Other Lipid-lowering Agents
These drugs control levels of various other fats in the blood that contribute to atherosclerosis. This group of medications includes bile acid sequestrants, fibrates, and niacin. Controlling the levels of all factors contributing to atherosclerosis is just as important for preventing a stroke as it is for preventing a heart attack.
Catheter Based Procedures and Surgical Procedures
In select cases where a carotid artery is severely narrowed, carotid angioplasty and stenting may be an appropriate treatment. Angioplasty is performed by placing a small balloon catheter at the site of carotid artery narrowing. The balloon is inflated and presses against the plaque buildup on the walls of the carotid artery, stretching and expanding the artery walls. The pressure of the balloon squeezing against the walls of the artery increases the artery's inside diameter.
In most cases, physicians also use devices called stents to prop open blocked arteries. A stent is a tiny, slender metal-mesh tube. Stents fit inside an artery and can be placed over compressed plaque deposits once an angioplasty has widened an artery. The stent is left inside the artery and acts as scaffolding that prevents the artery from collapsing or being closed off by plaque again.
Complications are uncommon but can include TIA and stroke. Devices designed to catch any debris before it can travel to the brain are frequently used during stent placement.
People who have angioplasty and stenting of their carotid artery usually stay overnight in the hospital and recover from the procedure in a few days.
Surgery may be done to physically remove the plaque from the site of artery narrowing. This surgical procedure is called “endarterectomy”. This procedure may be indicated when a person experiences symptoms of carotid artery disease or when a person's carotid arteries are severely narrowed, although the exact indications depend upon the individual patient’s situation. In some cases, patients with severe carotid disease who have not yet experienced symptoms can benefit from endarterectomy because this can reduce their chances of having a stroke.
Typically performed by a vascular surgeon or neurosurgeon, the procedure involves an incision into the neck to open the carotid artery. The physician then physically removes the plaque by pealing it away from the artery. Complications from endarterectomy are uncommon but can include TIA and stroke. After the procedure, the person may spend 1 to 4 days in the hospital and then return to normal activity in a few weeks.
If the carotid artery becomes completely blocked, then neither surgical endarterectomy nor carotid stenting are performed. Under these circumstances, physicians may recommend medications to help prevent progressive plaque buildup in the other carotid artery.
Lifestyle changes can also help people minimize the risk of developing or worsening carotid artery disease and therefore reduce your chances of having a stroke. You should:
- Quit smoking: This is the most important step to prevent carotid artery disease and stroke. Smoking causes blood vessels to constrict, injures blood vessel walls, and speeds up atherosclerosis.
- Lower high blood pressure: High blood pressure weakens the arteries and makes them susceptible to plaque buildup. Consuming a diet rich in fruits, vegetables, and low-fat dairy products and low in red meat and processed foods (known as the DASH diet) lowers blood pressure.
- Reduce high blood cholesterol: The higher a person's blood cholesterol level, the greater the risk for arterial disease. A diet that can help lower cholesterol includes limiting saturated fat intake to 10 percent of daily calories and eating at least 5 servings of fruits and vegetables daily. All patients with carotid artery disease should also be placed on optimal drug therapy to aggressively lower cholesterol levels.
- Maintain a healthy weight: Being overweight increases the risk of developing atherosclerosis. It also increases the risk of developing high blood cholesterol, high blood pressure, and diabetes, each of which increase the chances of having a stroke.
Be physically active every day: Regular physical activity reduces the risk of heart attack and stroke. Physical activity can improve cholesterol levels, help control high blood pressure and diabetes, and help manage weight. It also increases physical fitness and reduces depression and anxiety.
What is a stroke?
A stroke is a brain attack, or a sudden and severe lack of blood to the brain. This lack of blood causes infarction, or damage to brain tissue that results from ischemia, a lack of oxygen caused by insufficient blood flow. When blood flow is blocked long enough, the ability of the brain to control normal functions such as movement, speech, and vision is compromised, depending on the area of the brain that is deprived of blood.