Figure 1

Cerebrovascular disease is the third leading cause of death in the United States. Approximately 750,000 people suffer a stroke annually costing an estimated $45 billion in treatment and lost productivity. Carotid occlusive disease is responsible for 25% of these strokes. Large population-based studies indicate that the prevalence of carotid stenosis is approximately 0.5% after age 60 and increases to 10% in persons >80 years of age. The majority of cases are asymptomatic. Surgical carotid endarterectomy is currently the accepted standard of treatment for revascularization of extracranial carotid occlusive disease. This has been validated by multiple, randomized, controlled trials which have demonstrated its efficacy over best medical therapy. However, in the past several years carotid artery stenting has emerged as a potential therapeutic alternative to carotid endarterectomy for the treatment of atherosclerotic carotid artery disease. The future status of this endovascular approach will be determined by randomized trials directly comparing carotid artery stenting to endarterectomy as well as by the potential for further innovation and improvement in endovascular devices, techniques, and safety.

Hardening of the arteries, or atherosclerosis, occurs when an artery becomes narrow and the flow of blood is blocked. This can occur in various parts of the body such as the heart and legs. Arteries that supply blood to the head and neck are known as carotid and vertebral arteries. When these arteries become blocked, the condition is referred to as extracranial or brachiocephalic atherosclerosis. When a severe case of atherosclerosis is involved which results in a significant amount of blockage, blood flow to part of the brain can be obstructed, and a stroke can result.
There are certain risk factors associated with atherosclerosis of all types, including extracranial atherosclerosis. These include diabetes, high blood pressure, high cholesterol, and smoking. In addition, people of different ethnic backgrounds are more likely to get one type of atherosclerosis versus another.

Atherosclerosis of the carotid arteries is estimated to occur in the general population at a rate of 7% in women and 9% in men.1 When atherosclerosis occurs in the carotid arteries, blood clots and plaque—the material that causes the blockage—may separate and be carried into the head. Here, the blocking agents can obstruct the vessels that supply blood to the brain. Typical symptoms that result from a blockage of the carotid arteries include:

• Weakness or numbness on one side of the body,
• Inability to speak or understand speech, and
• Visual difficulties

If the blockage produced by the plaque or blood clot is small and breaks up quickly, a transient ischemic attack (TIA) may occur. TIAs are commonly referred to as ministrokes. However, if a larger vessel is blocked, or the blockage doesn’t dissipate quickly, a stroke can occur. Up to 25% of strokes are believed to be caused by carotid arterial blockages.2 People who have had a previous history of carotid arterial disease are more likely to develop an additional course of extracranial carotid artery disease.

When a blockage happens in the vertebral arteries, symptoms occur due to decreased blood flow to part of the brain, but are not due to pieces of clot or plaque. The symptoms of a blockage of vertebral arteries include

• Dizziness
• Nausea
• Difficulty with balance or coordination
• Blurry or double vision
• Changes in hearing

Treatment
When symptoms are present, a physician will want to assess for blockages and to treat extracranial atherosclerosis if it is found. If the narrowing of the artery is not severe, medication may be recommend. However, if the narrowing is especially problematic, surgery is usually recommended. A procedure called an endarterectomy is conducted to remove the plaque and allow the blood to flow more freely. This procedure is becoming increasingly more common, and has been referred to as “the standard” treatment for this disease. Endarterectomy is especially recommended for patients who have significant blockage.

Some patients, however, may not be suitable candidates for an endarterectomy due to poor health or a previous history of radiation therapy to the neck. Others may have already undergone endarterectomy but may have recurrent carotid blockages.2 People with blockages in the carotid artery have the option of undergoing a procedure in which the artery is opened with a small tube that inflates called a balloon catheter. This is similar to angioplasty, which is done on the heart. A stent, or supportive tube, is then placed in the artery to help keep it open. This procedure has especially been found to be effective in preventing strokes for patients with severe blockage.

Endovascular treatment (angioplasty and stenting) of carotid occlusive disease may offer the following advantages over endarterectomy:

• General anesthesia is usually not required, thus allowing the patient’s clinical status during the procedure to be monitored.
• Increased patient comfort and significant cost savings due to shorter recuperation period.
• No cervical incision is made, thus eliminating the risk of cranial nerve palsies, wound infections or neck hematomas.
• Procedures can be done simultaneously on carotid, vertebral and coronary arteries.
• Morbidity and mortality may be reduced in patients considered to be at higher risk for surgery (who have significant co-morbidities, contralateral carotid occlusion, post-endarterectomy restenosis, radiation-induced stenosis, prior radical neck dissection).
• Provides an option for treatment of carotid stenosis in patients who are not suitable candidates for CEA (i.e., patients with surgically inaccessible lesions).

For patients with blockages in the other major arteries that serve the brain, including the innominate, subclavian, and vertebral arteries, angioplasty and stent-supported angioplasty are usually the preferenced form of treatment.