Carotid Artery Stenosis

The carotid artery is one of the major vessels supplying blood flow to the brain. Because of this, it can be responsible for strokes. When a patient has carotid artery stenosis, or narrowing of this blood vessel, the concern is related to the resulting risk of stroke. Carotid artery stenosis develops like artery disease in other blood vessels. Certain factors including diabetes, high blood pressure, cholesterol, and family history increase the risk of formation of plaques. The carotid artery splits into an internal and external carotid artery. The location of this branch point is typically where the plaque develops. The internal carotid artery is the one that goes to the brain and is associated with causing strokes.

Carotid artery with plaque

These strokes result when parts of the plaque break loose or little clots form that get loose and travel to the brain.

Plaque traveling to brain to cause stroke

The diagnosis is made with imaging studies. The studies typically used are an ultrasound of the neck, CT scan, or MRI. At times these can be obtained because a recent stroke prompted an investigation to look for a cause. An ultrasound is also sometimes ordered to screen for carotid disease in patients who have risk factors that make carotid disease likely based on their history or findings on physical exam.

Once it is found, decisions are made about treatment. This is largely based on what the risk of stroke is and how to best reduce that risk. Generally all patients are started on what is called optimal or best medical therapy. This includes an anti-platelet medication (usually a low dose aspirin), and a statin medication (this is a class of medication that targets cholesterol). Best medical therapy also includes blood pressure control, blood sugar control for diabetics, and attempting to quit tobacco for those using tobacco. Surveillance is also important and repeated ultrasounds are obtained at intervals to see if there are changes in the disease.

The next part of treatment is a procedure to eliminate the narrow are and restore normal blood flow. Not everybody needs this. The decision to proceed with this is based on the risk of stroke and how much that risk can be improved. This risk is determined on two factors. The first is prior strokes or transient ischemic attacks (TIA). A TIA is also referred to as a mini-stroke at times and refers to stroke symptoms that last less than 24 hours. Usually TIA symptoms last less than an hour. The common symptoms of stroke and TIA are sudden vision loss, weakness or numbness on one side of the body, drooping of the face on one side, and inability to speak or understand language. A carotid stenosis with a stroke or TIA on the same side of the brain as the stenosis is called symptomatic. Because of the way we are wired, problems coming from a carotid artery will typically cause symptoms on the opposite side of the body. The exception here is sudden vision loss which is usually on the same side. A symptomatic stenosis is higher risk problem and if the narrowing is more than 50% a procedure is usually recommended. 

The second factor that is looked at for stroke risk is how narrow the stenosis is. In someone who is not having symptoms the carotid can get very narrow before it poses a significant risk that requires a procedure. Typically the discussion about a procedure takes place if the narrowing is above 70% (some places use 80%). Narrowing at this severe level is called critical stenosis. It is important to point out that elevated risk here does not mean very high risk. In someone who is not having symptoms but has critical stenosis the risk of stroke is probably about 1-2% per year on best medical therapy. This risk can be cut in half with a procedure; however, you have to take into account age, other medical conditions, and the risk of the procedure. There are cases where a conservative approach makes sense even in critical stenosis. An important point to keep in mind is that the risk of stroke is never 0. Even with best medical therapy and surgery there is still some remaining risk.

A special case to take note of is the situation where one of the carotid arteries is occluded or completed blocked.

Complete blockage of the carotid

Patient’s often find this very concerning and are surprised when they are told that they do not need a procedure. The brain gets blood flow from several arteries that have connections to each other within the brain. A carotid artery can be completely blocked without compromising blood flow to the brain. As we discussed earlier, the concern with carotid narrowing is the risk of stroke. In the situation where a carotid is entirely plugged, because there is no flow through here to the brain there actually isn’t a risk of stroke other than in very rare circumstances. 

More Information