The carotid arteries are a pair of large blood vessels which carry blood from one’s heart to their brain. The arteries run up either side of the neck, eventually entering the brain to supply most of the brain with blood. After they enter the brain, the carotid arteries join with other arteries. 4 out of 5 people simply need one carotid artery because when it joins with other arteries, it can supply both sides of the brain with blood. Interestingly, the way these arteries join can differ between people.
Carotid stenosis is the narrowing of one or both of the carotid arteries. This narrowing occurs over time, due to plaque buildup on the inside of the artery, a process known as atherosclerosis. Although this narrowing can not cause any symptoms, it can increase the risk for stroke, depending on how narrow the artery is or how the plaque behaves.
The plaque typically builds up at a part of the artery that splits (“bifurcates”) into an internal and an external carotid artery. The internal carotid artery (ICA) supplies blood to the brain, while the external carotid artery (ECA) supplies the neck, thyroid gland, face, and scalp. As the plaque enlarges, it begins to narrow the “lumen” of your carotid artery, which is the inside opening where the blood is flowing. This changes how easily the blood flows and can increase the risk of developing a blood clot inside the vessel. Over time, the plaque can become more and more dangerous. If blood clots form and then break away, it can travel up the artery into the brain, where it can block blood flow. When the brain does not get enough blood, it is quickly damaged and can not recover; this is called a stroke.
At times, stroke can occur because not enough blood is getting through a narrowed carotid artery. Nevertheless, this occurs very rarely, as arteries join up and share the workload in the brain very well.
As this is such an important issue, there has been a lot of research to find out more about the relationship between carotid artery disease and stroke risk. It has been found that how narrow the artery is (often reported as a percentage) can help to estimate the risk of stroke over a certain period of time. Stroke risk also depends on whether the carotid stenosis is causing symptoms or not, which will be addressed later.
CAUSES
Carotid stenosis is typically a chronic condition that affects people as they age. Excess cholesterol in the blood begins to change the blood vessel, and the body begins to send inflammatory cells to help. Low density lipoprotein (LDL) cholesterol is heavily involved in this process. After a while, the LDL cholesterol begins to get trapped inside and eventually sticks on the outside of the blood vessel. Over time, this process continues and plaque forms.
There are multiple reasons why atherosclerotic plaque can form in the carotid arteries:
- Genetics
- High cholesterol
- Fatty diet
- Not enough activity
- Smoking cigarettes
Certain patients who have had radiation treatment for head and neck cancers can develop carotid artery stenosis from the radiation effect and not actually from plaque development. There are also certain inflammatory conditions that can cause irregularities in the carotid arteries.
SYMPTOMS
Many patients do not experience symptoms related to carotid stenosis. It is often found by accident. Nevertheless, if the narrowing does become symptomatic, it can cause a transient ischemic attack (TIA) or stroke. A TIA is similar to a stroke, but does not cause permanent damage to the brain and cannot be found on an MRI or a CT scan. Typical signs of TIA or stroke include the following:
- Facial droop
- Difficulty speaking or understanding
- Weakness or numbness of the body on the opposite side
- Sudden loss of vision in the eye on the same side
The side of your body that the symptoms affect is a very important detail. For example, carotid stenosis involving the left carotid artery would produce sudden loss of vision in the left eye, facial droop or weakness and numbness in the right side of the body. The opposite is true when the right carotid artery is affected.
As part of a general medical exam, the primary care provider might listen to the carotid arteries with a stethoscope. This is to check for a bruit, or a “whooshing” sound, which can at times happen when the carotid artery is very narrow. If he or she hears a bruit, the patient will probably be scheduled for a carotid ultrasound.
Carotid stenosis typically does NOT cause:
- Dizziness/vertigo
- Lightheadedness
- Passing out
- Visual problems in both eyes
- Headache
- Weakness that affects the right AND the left side of the body
When doctors are looking into these types of symptoms, they can order a CT or MRI that finds carotid artery stenosis. This is called an incidental finding, which means the carotid stenosis was found by accident and is not responsible for those types of symptoms.
WHEN AND HOW TO SEEK MEDICAL CARE
Carotid artery stenosis is typically found by doctors one of two ways:
In the hospital after stroke-like symptoms
By accident when trying to find a cause for other symptoms
If someone is experiencing any stroke-like symptoms, call 911 immediately for transport to the nearest and most appropriate emergency department.
If carotid stenosis is found by a family doctor, or while in the hospital for another problem, the patient can be referred to a vascular surgeon or neurosurgeon to discuss treatment options.
TESTING AND DIAGNOSIS
Several imaging studies can detect carotid stenosis:
Duplex ultrasonography, or carotid ultrasound, is a simple, non-invasive test that can detect changes in blood flow and estimate how narrow the artery is. It is often the first step in evaluating suspected carotid artery stenosis and also used over time to make sure the narrowing does not worsen, if no surgery is recommended.
Computed tomographic angiography (CTA) is a special type of CT scan that involves an injection of contrast dye. It provides a detailed view of the blood vessels in the head and neck. Similarly, magnetic resonance angiography (MRA) is a special type of MRI that looks at the blood vessels. It can or can not use IV contrast. It can at times provide more information about the plaque inside the artery.
The gold standard test for carotid stenosis is a diagnostic cerebral angiogram and can be performed by a surgeon if further information is needed about the carotid arteries. Because this is a procedure, and not just an imaging study, it does have more risk involved and is reserved for patients who need advanced imaging.
MAGNETIC RESONANCE ANGIOGRAPHY (MRA)
This is a noninvasive study which is conducted in a Magnetic Resonance Imager (MRI). The magnetic images are assembled by a computer to provide an image of the arteries in the head and neck. No contrast material is needed, but certain patients can experience claustrophobia in the imager.
TREATMENT
Treatment for carotid stenosis depends mostly on how narrow the artery is and whether the narrowing is causing symptoms (stroke or TIA). There are three major ways that carotid stenosis can be treated:
MEDICAL MANAGEMENT
Medical management is a way to treat carotid artery stenosis that does not involve surgery or an invasive procedure. It typically involves the following:
- One or more medications to thin the blood
- Controlling blood cholesterol
- Maintaining normal blood pressure with a combination of lifestyle and medications
- Eating a balanced and healthy diet
- Increasing activity level
- Stopping tobacco use
- Maintaining a healthy weight
- Keeping diabetes well-controlled
Many of these treatments address the risk factors for carotid stenosis, which means that the problem is being treated at its root cause. This is not a quick fix, but rather takes time and dedication. A doctor or a neurologist specializing in stroke will see the patient periodically to check labs and discuss lifestyle modifications that can keep the risk of stroke low. Treatment of carotid disease is a team effort, and the patients are the most important team member!
CAROTID ENDARTERECTOMY
Carotid endarterectomy is a surgical procedure to remove the plaque from inside the carotid artery. It is performed by a neurosurgeon or a vascular surgeon. It is often performed under general anesthesia, but can also be performed as an “awake” procedure with sedation and local anesthesia to avoid the risks of deeper anesthesia.
Carotid endarterectomy (or CEA) can be thought of as the “tried and true” surgical treatment for carotid stenosis. It is the only way to remove plaque from the artery. Research shows that if the patient has NOT had a stroke or a TIA, carotid endarterectomy is generally helpful to reduce stroke risk if the narrowing is 70% or greater. If the patient has suffered a stroke or TIA, carotid endarterectomy can be helpful if the stenosis is over 50%.
A carotid endarterectomy surgery is done to lower future risk of stroke. It cannot make the patient’s symptoms better if they have suffered a stroke.
CAROTID ANGIOPLASTY AND STENTING (CAS)
CAS is an endovascular procedure, meaning it is performed from inside the blood vessel. It involves a small catheter, or tube, being placed into the artery in the wrist or leg. It is then guided into the carotid artery in the neck. A balloon is inflated to open the artery, and a flexible metal stent can be placed to keep the artery open.
There is a risk that placing a stent into the artery can break off small pieces of plaque or blood clot and cause a stroke. There are several methods used to “trap” these small pieces and make sure they do not travel to the brain. A distal protection device is like a net placed further downstream to catch these particles. It can be set up before the stent is placed. There are other methods that can temporarily reverse or stop blood flow in the carotid artery, allowing the particles to be filtered outside the body or suctioned out after the stent is placed.
Carotid angioplasty and stenting is a newer method to treat carotid stenosis. In general, it has been found to have similar results as carotid endarterectomy in reducing stroke risk, and a large study found that the risks and benefits are not very different. That study also found that certain types of patients tend to do better with carotid stenting, while others tend to do better with an endarterectomy.
There are many factors to be considered when determining which approach is best for the patient. It is necessary for a neurosurgeon or vascular surgeon to review the patient’s imaging and history to help decide on the best treatment.
If a patient has had a carotid endarterectomy in the past, there is a chance the artery can become narrow again. If this happens, and the narrowing is severe enough, carotid angioplasty and stenting is the preferred method of treatment. It is also safer than endarterectomy when the plaque is too high in the neck to access with a surgery, or if the patient has had radiation treatment to the head and neck in the past.
FOLLOW-UP
Blood thinning medications are used before and after surgery for carotid stenosis to reduce the risk of stroke – both during the surgery, and as the artery heals. Often, the family doctor or neurologist specializing in stroke will keep the patient on blood thinning medications even after surgery to keep stroke risk low.
Duplex ultrasonography is often used to follow patients with carotid stenosis. If medical therapy is chosen as treatment, it is important to make sure the narrowing is not getting worse. If an endarterectomy or stent are performed, it is important to make sure the artery does not become narrow again.
At times, atherosclerotic plaque can build up again over several years until the artery is narrow. In this case, another treatment can be recommended, depending on the severity of the narrowing. Nevertheless, if the artery quickly becomes narrow again within the first six months or so, it is likely due to intimal hyperplasia, or thickening of the inside of the blood vessel. Think of it as the formation of a scar on the inside of the artery. This is a normal healing process that occurs after surgery on a blood vessel; nevertheless, in certain people the scar continues to form. This can be treated with a stent if the narrowing is severe.
LATEST RESEARCH
CREST 2 occurs as an ongoing clinical trial randomizing patients to surgery or medical management of carotid artery stenosis that is asymptomatic (has not caused TIA or stroke). The goal of this study is to further understand when it is best to operate and when it is best to treat with medications, as this is not always an easy decision. If a patient’s carotid stenosis is not severe and they have not had a stroke or TIA, they can be a candidate to enroll in this trial.
