Carotid Stenosis
Carotid stenosis is the narrowing of the carotid artery, located in the neck, and is caused by the buildup of plaque (fatty deposits). The process of atherosclerosis in the carotid artery causes a hardening of the walls of the arteries and, results in a carotid stenosis that decreases the flow of blood and nutrients to the brain.
The carotid arteries are located on the sides of the neck. They are crucial arteries, and are a means of blood to the anterior part of the brain and, through branches, to the eyes, forehead, and nose. The deposition of plaque along the inner wall of an artery narrows its diameter. This makes the blocked artery less efficient in carrying blood. Plaque formation can develop so severe that an artery is effectively blocked.
Carotid stenosis creates another danger when bits of the plaque dislodge. These portions, which are referred to as blood clots or emboli, can travel upward with the flow of blood towards the brain, and can become stuck, blocking blood flow. This obstruction disrupts the supply of nutrients and oxygen to the brain, and is one of the causes of cerebral vascular accidents, known as stroke. Carotid stenosis is a form of cerebral vascular disease and atherosclerosis.
Stroke is the third leading cause of death in the United States after coronary artery disease and cancer, with approximately 750,000 strokes and more than 150,000 deaths occurring each year in the United States. Approximately 50% of these strokes are considered to be the consequence of carotid stenosis.
Causes and symptoms
The cause of carotid stenosis is the buildup of plaque on the inner wall of the carotid artery. The decreased blood flow to the brain and the obstruction of other arteries following the release of emboli can cause a stroke. Increased risk of carotid stenosis is related to smoking, hypertension, elevated levels of cholesterol, obesity, and a sedentary lifestyle. Some of these factors such as hypertension and cholesterol level may also be related to a person's physiology. Another risk factor is diabetes. Older, less active people are more prone to carotid stenosis.
Occasionally, preceding a major stroke, a person can be temporarily affected by the arterial blockage or discharge of a small embolus. The interrupted flow of blood to the brain, which can be very brief or last a few hours, does not continue longer than 24 hours. Symptoms of this transient event, called a transient ischemic attack (TIA), include weakness, as well as visual and speech difficulties. The exact symptoms of carotid stenosis depend on the region of the brain that is affected. Symptoms can also be absent, with the stenosis discovered only incidentally during a clinical examination.
In the event of a stroke, if the blocked blood flow is not restored, brain cells can die, causing permanent brain damage.
Diagnosis
Though not as accurate as other techniques, a physician can listen to the pulsation of blood through the carotid artery by means of a stethoscope. A weaker pulse, which is a result of stenosis, will be evident in the form of altered sounds (bruits) as the blood flows past the region of disruption.
Sometimes, carotid stenosis is suspected if a person has a transient malfunction of blood flow to the brain, or a TIA. A TIA can last anywhere from a few seconds to several hours. The brief blockage of the artery can cause a temporary loss of vision in one eye, a weak or numb sensation on one side of the body, slurred speech, or inability to speak. A TIA can be a warning to a physician of the potential presence of carotid stenosis.
Three main diagnostic tests assist in the diagnosis of carotid stenosis. The first is known as a duplex sonogram, or a carotid duplex. The procedure involves the use of high frequency sound waves (ultrasound). The ultrasonic waves echo off of the carotid artery to create a two-dimensional image on a screen. If narrowing or obstruction of the carotid artery is present, it is often evident on the image.
Another dominant imaging technique is magnetic resonance imaging (MRI) or magnetic resonance angiography (MRA). Both rely on the use of magnetism. Pulses of magnetic energy can be utilized to image the targeted area of the body, based on the disruption of the flow of the electrons in the magnetic field. This information is then converted to a visual image.
The third technique is known as an angiogram or arteriogram. An angiogram is an examination that utilizes x rays after a small tube (catheter) is placed into the base of the carotid artery. An x-ray dye is then injected. The dye reveals the regions of the arteries that are narrowed or blocked.
Treatment
Carotid stenosis is treated surgically or medically. One of two surgical treatments is normally used. The first approach is known as microsurgical carotid endarterectomy. The second approach is known as endovascular angioplasty and stenting.
Carotid endarterectomy is the surgical exposure of the carotid artery and the removal of the plaque. This re-establishes the continuous flow of blood to the brain. This approach is the technique of choice for most patients. Though, the technique does carry a risk of stroke (stroke can be caused in up to 3% of surgeries).
For patients who are unable to undergo surgery, the angioplasty and stenting approach is used. In this approach a catheter that contains an expandable area at one end is inserted into the carotid artery. The end of the catheter is then expanded. This "balloon" squeezes the plaque against the arterial wall, increasing the useful diameter of the artery. Then, a stent is placed inside the artery. A stent is a tubular array of fibers somewhat similar visually to wire fencing rolled up into a tube. The stent strengthens the carotid artery to prevent its collapse and to keep the plaque firmly against the arterial wall.
Surgery and the related risks may not be acceptable in patients whose arterial blockage is less than 50%. Anticoagulant medications such as aspirin can be used instead to decrease the tendency of blood clots to form. Treatment can also consist of lifestyle changes such as stopping smoking, limiting cholesterol intake, or use of cholesterol-lowering medications.
Prognosis
With prompt medical treatment, including surgery, recovery from carotid stenosis can be complete with no residual effects. However, if treatment is delayed or if a stroke occurs, damage can be permanent.
If carotid stenosis is dealt with quickly by surgery, medicine, or lifestyle changes, prognosis is good. For example, at the Johns Hopkins Medical School, carotid stenosis corrective surgery has a mortality rate of 0.8% (80 in 1,000 people) and a morbidity rate (the person survives, but with some complication) of 1.8% (18 in 1,000 people).
However, undiagnosed stenosis can result in stroke. Depending on the severity of the stroke, prognosis is unpredictable. An estimated 325,000 strokes and 75,000 deaths occur each year in the United States due to carotid stenosis.
Special concerns
However if there are no symptoms related with the presence of carotid stenosis, the difficulty is often a warning sign of possible blockage of the arteries of the heart, or coronary artery disease. Therefore, people diagnosed with carotid stenosis should be carefully monitored for coronary artery disease.
Information from mayoclinic.org
