Carotid arteries are located on each side of the neck, just below the jaw line. They supply blood to the anterior (front) brain where sensory and motor function as well as speech, vision, personality and thinking reside. Two smaller arteries -- the vertebral arteries -- supply blood to the back of the brain, the cerebellum and brainstem.
What is Carotid Stenosis?
Carotid stenosis, also known as carotid artery disease, is a narrowing of a carotid artery. The narrowing is caused by plaque or fatty deposits along the inner wall of the artery resulting in reduced blood flow to the brain and, in some cases, a complete blockage of the artery. Similar to coronary artery disease, a carotid artery also may develop arteriosclerosis, a chronic disease characterized by abnormal thickening and hardening of the arterial walls with resulting loss of elasticity on the inside of the artery.
Many patients do not show any symptoms and the stenosis is discovered on a routine medical exam as the physician listens with a stethoscope to the blood flowing through the artery.
If there are symptoms, they will depend on which carotid artery is involved. Some patients may experience a transient ischemic attack (TIA). TIA's are usually characterized by blurred vision or a brief loss of vision in one eye, slurred speech, numbness or weakness on one or both sides of the body, paralysis and loss of consciousness resulting from insufficient blood flow to the brain. These symptoms are often a sign of a more serious cerebral accident and must be treated immediately to prevent a major stroke.
Besides the observable symptoms mentioned above, there are four imaging studies that are used to diagnose carotid stenosis. They are:
Carotid ultrasound: A noninvasive test that uses ultrasound to create an image of the artery when narrowing of the carotid arteries due to plaque buildup is suspected. It is often the first test used on a patient being evaluated for surgery to reopen a blocked artery. Duplex scanning is a technique that measures blood flow at many points in the blood vessel at one time.
Carotid arteriogram: Arteriography, also known as angiography, is a blood-flow test. Dyes are injected into the blood vessels and an X-ray is taken to produce a picture of the blood flow through the vessels.
Magnetic imaging angiogram (MRA): MRA uses a magnetic field and radio waves to create detailed computer images of blood vessels and is able to distinguish healthy tissue from diseased tissue.
Computed tomography angiogram (CTA): During a CTA scan, a special dye is injected into a vein in the arm to highlight the blood vessels and makes them easier to see on the scanned images. The CT scanner uses a thin X-ray beam and advanced computer analysis to create highly detailed images.Causes and Risk Factors
Increased risk factors for carotid stenosis are:
- Elevated cholesterol levels
- Age (men under 75 years old and women older than 75)
- Family or personal history of coronary artery disease or carotid artery disease
- High blood pressure
- Inactivity or sedentary lifestyle
One of the primary risks associated with carotid stenosis is increased susceptibility for stroke.
No physician can predict with certainty whether a patient will suffer a stroke due to the narrowing of the carotid arteries. It is thought that arteries that contain jagged or unstable plaques are more likely to dislodge and when they do, restrict blood flow to the brain, causing a stroke. With stroke being the third leading cause of death in the United States and carotid stenosis accounting for approximately 50 percent of those deaths, medical intervention at the first suspicion of a stroke is essential.
If a patient's artery blockage is less than 50 percent, the risk of surgery or stenting may outweigh the benefits. The physician may treat the blockage with anticoagulant medications (such as aspirin) which prevent clots from forming. The physician also may prescribe lifestyle modifications including stopping smoking and reducing dietary cholesterol, as well as the use of cholesterol lowering medications.
With blockages greater than 50 percent, surgery may be the best option. Patients who have had a TIA may also be candidates for surgery. As with any invasive surgery, there are risks and complications that need to be discussed with the physician before agreeing to surgery.
There are two treatment options for carotid stenosis.
The first involves making an incision in the neck and microsurgically removing the plaque within the artery. There is a risk of a stroke during this procedure although that risk is deemed to be very small.
The second is angioplasty and stenting which is a minimally invasive procedure which does not require an incision in the neck. A catheter (tube) is inserted through a small pinhole in an artery in the groin. The artery is expanded with a balloon and a stent (mesh tube) is put in place to hold the artery open and keep the plaque against the arterial wall. The minimally invasive stent procedure is used in a select group of patients who meet clinical criteria.
With both an endarterectomy and stenting, physicians stress that making permanent lifestyle modifications will be beneficial overall.