What is carotid artery dissection?
The four carotid arteries, two on each side of the neck (an internal and an external carotid), deliver blood from the aorta (the heart’s main artery) to the brain, the eyes, the face and other structures in the head. The carotid arteries can be felt on each side of the lower neck, immediately below the angle of the jaw.
The artery walls are made up of three layers of different types of tissue, each with a specific function. Dissection occurs when a tear in the artery wall allows blood to leak between the layers and separate them. The effect has been described as what happens to a piece of plywood that gets wet.
What causes carotid artery dissection?
Certain medical conditions such as Marfan syndrome – a genetic connective tissue disease –fibromuscular dysplasia or atherosclerosis (the accumulation of fatty plaque in the artery walls) put individuals at risk for developing carotid artery dissection. Carotid artery dissection in these patients is called “spontaneous,” meaning that it occurs without trauma to the head or neck.
Carotid artery dissection also can occur in the general population as a result of blunt trauma injury to the neck, such as a car accident or a fall, or from hyperextension of the neck in sports or exercise. The incidence of carotid artery dissection as a result of blunt injury (mainly high-speed car accidents) ranges from less than 1 percent to 3 percent, according to a recent study.
High blood pressure and smoking increase the risk for both types of carotid artery dissection. Some cases of carotid artery dissection also have been reported after invasive diagnostic procedures.
How does carotid artery dissection develop?
Carotid artery dissection begins as a tear in one layer of the artery wall. Blood leaks through this tear and spreads between the layers of the wall. As the blood collects in the area of the dissection, it forms a clot that limits blood flow through the artery. If the clot is large enough to completely block blood flow, the result can be a stroke. Equally dangerous, pieces of the clot can break off and travel up through the bloodstream to become trapped in the smaller arteries in the brain which can limit the blood flow to a region of the brain and cause a stroke.
Depending on where the dissection occurs in the artery, it may cause the artery to bulge in the area where the blood is pooling. This bulging, blood-filled are is called a pseudoaneurysm. A pseudoaneurysm can cause symptoms of stroke by pressing on surrounding brain structures.
What are the symptoms of carotid artery dissection?
Sometimes a stroke is the first sign of carotid artery dissection and emergency treatment is required. More commonly, symptoms develop over a period of hours or days, even in patients who have traumatic injuries. Symptoms are general rather than specific and include headache, neck and face pain (especially pain around the eyes), vision disturbances such as double vision or a droopy eyelid, a sudden decrease in sense of taste and weakness on one side of the body.
Stroke can develop hours, days or even a week after these symptoms begin. This is the most serious risk of carotid artery dissection.
How is carotid artery dissection diagnosed?
When a patient comes to the doctor’s office or the emergency room with any of the symptoms described above, the doctor may suspect carotid artery dissection. To accurately diagnose this condition, the doctor can choose from several different imaging technologies to see how well blood is flowing through the carotid arteries.
Helical computed tomography angiography (CTA) is becoming the gold standard for use in trauma patients with symptoms of carotid artery dissection. This is a noninvasive type of imaging that uses computed tomography (CT) technology and a contrast material to provide an accurate, three-dimensional picture of the arteries on a computer screen.
Magnetic resonance angiography (MRA) or magnetic resonance imaging (MRI) are additional, very accurate, noninvasive imaging techniques that can be used for diagnosing carotid artery dissection. They use a magnetic field and radio waves to provide pictures of the carotid arteries.
In addition to blood flow, these technologies can show changes in the dimension of the carotid artery, blood in the wall of the artery and changes to structures surrounding the blood vessel. CTA is especially useful because it can create cross-sectional images of the blood vessel that will show separation of the layers of the vessel wall that is characteristic of dissection. These studies can also assess the brain and determine if there has been damage to brain tissue as a result of the dissection.
Doppler ultrasonography (DUS) is gaining popularity as a useful tool in identifying carotid artery dissection. This technology is now widely available in the hospital setting. Doppler ultrasound can detect abnormal blood flow in a dissected artery. DUS has the advantages of being fast, noninvasive and easy to use at the patient’s bedside.
As these new technologies have developed and improved, the use of conventional angiography for diagnosing carotid artery dissection has decreased.
This type of angiography uses a contrast dye and X-ray to image the blood vessels. It is not as accurate as the newer imaging technologies, is invasive and has a 1 percent risk of complications.
How is carotid artery dissection treated?
In some cases, carotid artery dissection is not diagnosed until after a stroke has developed. In those patients, treating stroke to prevent lasting effects is the goal.
When a patient comes into the doctor’s office or the emergency room with symptoms of carotid artery dissection without stroke, preventing stroke is the primary treatment goal. Appropriate treatment for an individual patient depends on whether the patient has an underlying disorder such as Marfan syndrome or has experienced trauma, where and how the injury occurred and where the patient has other injuries or medical conditions.
First-line treatment for carotid artery dissection usually is anti-coagulation or medication to thin the blood and prevent the formation of blood clots. Heparin given intravenously (through the vein) followed by warfarin that is taken orally are the most common therapies used. These medications prevent blood clot formation and thus can help protect against stroke. They usually are prescribed for three to six months, but some patients may require longer treatment.
Anti-platelet drugs such as aspirin, ticlopidine or clopidogrel sometimes are used in combination with or instead of warfarin. These drugs prevent blood clot formation by a different mechanism than the anticoagulants and can be equally effective. There is no scientific evidence yet that one class of drugs is better than the other for preventing clot formation in patients with carotid dissection.
Those patients who are unable to take either anticoagulants or antiplatelet agents, those who are on warfarin but continue to have symptoms such as vision disturbances or weakness, or those who have very low blood flow to the brain due to carotid artery dissection may need a procedure to try and correct the process of dissection. Normally, these are minimally invasive treatments that are performed through the blood vessels. Angioplasty (repairing the dissected section of artery) or placement of a stent (a mesh-like device that holds the artery open) are two endovascular procedures that are used to treat carotid artery dissection. They frequently are used together to provide the longest-lasting treatment. Cleveland Clinic interventional cardiologist, neurointerventionalist, and vascular surgeons perform over 200 endovascular procedures every year on patients with carotid artery disease.
What is the outlook following carotid artery dissection?
For spontaneous carotid artery dissection, the mortality is less than 5 percent. The risk for lasting neurological impairment from the disease is considerably higher. More than half of patients with spontaneous carotid artery dissection develop a stroke, sometimes delayed by hours or days. Even so, an estimated 75 percent of patients with spontaneous carotid artery dissection make a good recovery.
In patients with dissection following trauma (car accident, sports injury, etc.) the stroke rate ranges from 3 to 44 percent, depending on the severity of injury. An estimated 37 to 58 percent of patients with dissection following trauma have lasting neurological problems. They also have a higher mortality rate compared with patients who have spontaneous carotid artery dissection.
Following the first incidence of carotid artery dissection, patients have a 1 percent risk of recurrence per year over the next 10 years. Risk of recurrence is higher in younger patients than older patients, but younger patients also respond better to treatment and have a better outlook. Some patients have reported persistent headache after carotid artery dissection, lasting years after the event.
People who have had carotid artery dissection should see a vascular specialist for a CTA, DUS or other imaging to assess the severity and extension of the dissection. This imaging is normally repeated several months later to have the dissection re-evaluated for either progression, resolution or stability of the injury.
How can I prevent carotid artery dissection?
If you have an underlying disease that increases your risk of carotid artery dissection, it is important that you are under the care of a vascular specialist and follow your doctor’s instructions. For other individuals, following the same steps that reduce your risk of heart disease – healthy eating, weight management, exercise and smoking cessation – can reduce your risk of carotid artery dissection by improving the health of your blood vessels.
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