Stroke, or an interruption or reduction in blood flow to the brain, is the third leading cause of death in the United States. Each year, approximately 700,000 Americans suffer strokes, and 160,000 of them die from stroke.
According to an estimate from the American Stroke Association, the cost of stroke-related health care and disability in the U.S. will exceed $65.5 billion in 2008.
Stroke claims a very high proportion of U.S. citizens not only in mortality but also in secondary morbidity, or other health problems that can result from a stroke. These include paralysis, pain, and other neurological problems; infection; prolonged disability; and depression.
Following are the causes, symptoms, diagnosis, and treatment of carotid artery disease, a leading cause of stroke.
Causes
The most important risk factor associated with stroke is hypertension, or high blood pressure. Hypertension can be controlled in many cases. By following the doctors’ treatment recommendations and making lifestyle changes to keep one’s blood pressure under control, individuals who have hypertension can help reduce their risk of stroke.
There are two major types of strokes. In a hemorrhagic stroke, bleeding occurs in the brain. In an ischemic stroke, blood flow to the brain is interrupted or reduced; for example, because a clot blocks an artery. Recent research suggests that there may not be a very great difference between an ischemic stroke and a transient ischemic attack (TIA), a condition in which a patient has transient symptoms of stroke. In the traditional definition, strokes are neurological deficits that persist permanently and TIAs are strokes that completely reversed. Some recent studies have found that approximately 30-40% of patients who have had TIAs actually have had strokes.
Blood flow to the brain is supplied through four arteries, two in the front of the neck, known as the carotid arteries, and two in the back of the brain, known as the vertebral arteries. These arteries join at the base of the brain to supply blood flow to the brain. In the neck, each carotid artery bifurcates, or divides, into two smaller arteries, the internal and external carotid arteries. The carotid artery bifurcation is a common place for plaque to build up and cause narrowing of the artery.
From one person to the next, the carotid arteries vary tremendously in the precise way in which they connect, as well as in the way the body compensates if one artery is obstructed. Ischemic strokes and disease of the carotid arteries is perhaps the most well-studied disorder in the history of medicine.
Carotid disease is very highly associated with stroke. Approximately 75% of all ischemic strokes occur in the distribution of the carotid arteries in the neck. In the most common case, a piece of the plaque that develops at the carotid artery bifurcation breaks off and travels to the brain, causing either TIAs or stroke.
Carotid bifurcation disease is usually discovered either because a patient experiences symptoms or because a physician listens over the neck and hears an abnormal sound called a bruit during a routine physical examination. It is important to recognize the symptoms that may herald an oncoming stroke so that medical care can be started as promptly as possible.
Symptoms
In strokes or TIAs caused by carotid artery disease, the symptoms are very clearly defined. They may include all or some of the following.
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Transient weakness or paralysis of the arm or the leg or both that reverses completely over a period of minutes to hours. The longer these symptoms persist, the higher the chance that the individual is actually having a stroke.
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A transient blindness that develops in one eye. Patients most commonly describe this as sense of a window shade lowering in the field of the affected eye.
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An inability to speak, an inability to comprehend words, or an inability to find the proper words.
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Confusion.
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Mechanical inability to speak because of drooping of the face on one side.
It is important to note that the symptoms from carotid disease are most commonly reflected on the other side of the body. For example, a TIA or stroke affecting the left carotid artery, and therefore the left side of the brain, will affect the right arm, the right leg, the right side of the face, or some combination of these.
Diagnosis
Diagnosis is fundamentally based on the ability of the patient or the physician to recognize these symptoms and have the patient evaluated at a hospital by a neurologist, a vascular surgeon, or an emergency room physician.
The most common method of diagnosing carotid artery disease is duplex ultrasound. Duplex ultrasound is a non-invasive method of imaging the arteries to determine whether there is significant plaque. Occasionally other studies may be needed, such as an MR angiogram, a CT angiogram, or a traditional contrast angiogram. When performed by trained ultrasound technicians in an accredited diagnostic vascular ultrasound laboratory such as the one at UCSD, carotid duplex ultrasound is extremely reliable, and in the great majority of cases it is the only study needed for planning surgical treatment.
Treatment
Carotid artery disease may be treated by medical therapy, by surgery, or by a combination depending on the individual patient’s situation.
In recommending treatment for a patient, the physician considers these factors:
Studies show that a surgical procedure called carotid endarterectomy is clearly more effective than medical treatment in patients who meet any of the following conditions:
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The patient is symptomatic and has greater than 70% stenosis
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The patient has no symptoms and has greater than 80% stenosis based on ultrasound or 60% by angiography
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The patient has moderate-grade carotid artery stenosis which is continuing to cause symptoms even with medical management.
In patients who have symptoms and greater than 70% stenosis, the results of a large number of prospective randomized trials show that treatment with a combination of carotid endarterectomy and aspirin results in dramatically lower rates of stroke than treatment with aspirin alone. For this reason, surgical treatment is recommended for symptomatic patients who have a greater than 70% stenosis as well as for symptomatic patients who have greater than 50% stenosis and are continuing to have symptoms despite being on medical therapy.
Studies also show that asymptomatic patients benefit from surgical treatment compared to medical treatment if the operation is performed by a surgeon who has a personal record of very low stroke rates, morbidity rates, and mortality rates for this operation.
Most patients who have asymptomatic carotid stenosis will not go on to have a stroke. However, more than 50% of patients who go on to have a stroke will have proceeded from being asymptomatic one day to having a stroke the next. The challenge is to identify which patients who have asymptomatic stenosis will develop a stroke and which patients will remain asymptomatic. For this reason, we and other vascular surgeons strongly believe that surgical therapy should be considered for an asymptomatic patient if the patient is at good risk and the surgeon’s stroke rates and mortality results are acceptable. When discussing treatment options with a patient, each surgeon should inform the patient of his or her own morbidity and mortality rates for the procedures that are being considered.
The treatment of carotid artery disease has evolved over the years and continues to evolve. In recent years, another procedure, carotid stenting, has emerged as a treatment option for carotid disease. Although early results suggest this procedure can be done safely with acceptable and equivalent stroke rates compared to carotid endarterectomy, the results are very operative dependent and we do not have any long-term data on the durability of carotid stenting as compared to carotid endarterectomy. Clinical trials of carotid stenting are ongoing, however, and it appears to be an acceptable alternative for selected high-risk patients who meet certain criteria.
Surgery for the prevention of stroke has a long record of efficacy in selected patients. Identifying those patients who will benefit from surgery for carotid artery disease can go a long way toward reducing the number of people who suffer morbidity or mortality from stroke. Individual patients can help reduce their risk of stroke by controlling hypertension, recognizing the symptoms of carotid artery disease, and seeking medical care when symptoms occur.