The carotid arteries are two blood vessels that run up along the sides of your neck into your brain. Together with the two vertebral arteries at the back of the neck, the carotids allow a way for the brain to receive the blood it needs for oxygen.
What is Carotid Stenosis?
Like any other arteries, the carotids can be damaged. High blood pressure, high cholesterol, and smoking are a few ways to increase to risk of plaque buildup in the carotids and other blood vessels. When a plaque builds up in a vessel of the heart, it can cause a heart attack. When a plaque builds up in a blood vessel either in or traveling to the brain, it can cause a stroke.
Carotid stenosis is a term used to mean a narrowed carotid artery. When a plaque narrows the carotid artery, it can cause a stroke in two ways. The most common way is for part of the plaque to break off, form an embolus, and travel through the blood vessels until it lodges tight and blocks off blood flow to part of the brain. The tissue then dies due to lack of oxygen (ischemia).
Carotid stenosis can also decrease the flow of blood to the brain, so that if blood pressure drops, the part of the brain depending on that artery does not receive enough blood. This scenario is less common than embolization, because the brain is built to supply tissue from more than one artery at a time as a kind of precaution against ischemic damage.
Because carotid stenosis is such a risk factor for stroke, it cannot just be ignored. However, there’s some controversy about how carotid stenosis is best treated. There are three main ways to treat carotid stenosis: medical treatment, surgical treatment (carotid endarterectomy), and minimally invasive vascular stenting.
Up to a point, medical treatment of carotid stenosis is universally thought to be the best option. For example, if the carotid artery is less than 50% narrowed, there is generally no need for invasive therapy.
Instead, treatment focuses on ensuring that the plaque does not get larger. Risk factors like smoking, hypertension, and high cholesterol need to be addressed. As always, diet and exercise remain critically important.
In addition, the doctor will usually prescribe some form of blood thinner to prevent a clot from forming and blocking off the artery or embolizing to the brain. Depending on the severity of the case, this may range from something as simple as aspirin to something as potent as Coumadin.
Many experts agree that the best medical therapy has continued to improve over time, making it an even stronger option compared to more invasive procedures.
Carotid endarterectomy (CEA) is a surgical procedure in which the carotid is opened up and the plaque cleaned out. Carotid endarterectomy has been well-studied, and data shows that it clearly improves outcomes overall under select conditions. The carotid must be significantly blocked (usually more than 60%) but not completely blocked. The surgeon must be skilled, with a very small mortality rate associated with the surgery. Finally, the patient must be otherwise healthy enough to recover well from a surgical procedure.
Possible side effects of CEA include a 3 to 6% risk of stroke or death. At least in the month after the procedure, the risk of heart attack seems larger in patients who undergo a CEA than stenting. Because certain cranial nerves receive their blood supply from this vessel, they may be damaged during the surgery. Opening the carotid could also lead to hyperperfusion injury when the brain cannot regulate the new increase in blood flow, which may result in headache, seizures, and neurological deficits.
Carotid artery stenting (CAS) involves a thin catheter being threaded through the blood vessels, usually starting from the femoral artery in the thigh, up into the carotid artery. This is done under fluoroscopic guidance so the specialist can see what they’re doing. Once the catheter is in position, a stent is placed into the artery to help open it up and keep it open. In general, recovery time from CAS is quicker than that of CEA.
Many people like the idea of carotid stenting because it seems less invasive than carotid endarterectomy. However, stenting has not been around as long as CEA, and it has risks as well. Early studies seemed to show the risks of stenting were significantly greater than CEA in general. However, these studies have been criticized for comparing relatively inexperienced physicians doing stents to more experienced doctors doing CEA.
A recent study has shown that while stenting may be as effective as CEA in opening arteries, the risk of stroke associated with the procedure is higher than in CEA, at least in the first month after the procedure.
How to Choose?
The first step is to decide if any treatment beyond medicine is required at all. A major factor in decision-making is whether the stenosis has already caused a stroke or not. If not, and if the stenosis is less than about 80%, many doctors prefer just medical management. If a stroke has occurred, it may be an indication that more aggressive treatment is needed. If the stroke is too large, however, there may not be enough brain left to justify the risks of the procedure.
Since its introduction in the late 1990s, carotid stenting has slowly been gaining popularity. Medicare now covers the procedure under select conditions. In the end, the best treatment will depend on unique characteristics of the patient, doctors, and even insurance.
Some research has shown that factors like the length of the stenosis and shape of the plaque and blood vessel can impact the chance that CAS will lead to stroke. The elderly generally do more poorly with a stent than a younger person, though a very healthy elderly person might do well.
Insurance also plays a factor. Medicare will generally cover CAS for symptomatic patients with a high risk for CEA who have at least 70% stenosis. Other types of stenosis (about 90% of cases) need to be cared for in another fashion.
Ultimately, the decision-making about how to manage carotid stenosis is as unique as the person with the stenosis. The research is often unclear, and because there is money to be made involved with each option, it may be challenging to get an unbiased opinion. Do not be afraid to ask more than one physician for their thoughts.
Brott TG, Hobson RW 2nd, Howard G, Roubin GS, Clark WM, Brooks W, Mackey A,Hill MD, Leimgruber PP, Sheffet AJ, Howard VJ, Moore WS, Voeks JH, Hopkins LN, Cutlip DE, Cohen DJ, Popma JJ, Ferguson RD, Cohen SN, Blackshear JL, Silver FL, Mohr JP, Lal BK, Meschia JF; CREST Investigators. Stenting versus endarterectomy for treatment of carotid-artery stenosis. N Engl J Med. 2010 Jul 1;363(1):11-23. Epub 26 May 2010.
Ropper AH, Samuels MA. Adams and Victor's Principles of Neurology, 9th ed: The McGraw-Hill Companies, Inc., 2009. McCabe MP, O'Connor EJ.
Sharon Swain, Claire Turner, Pippa Tyrrell, Anthony Rudd on behalf of the Guideline Development Group, Diagnosis and initial management of acute stroke and transient ischaemic attack: summary of NICE guidance, BMJ 2008;337:a786, July 24, 2008