What is Symptomatic Carotid Artery Stenosis?
Strokes, which are the third leading cause of death in developed countries and the main cause of serious, long-lasting health problems, are typically caused by the blockage of blood flow to the brain (known as ischemic strokes) in roughly 85% of cases. This often happens because clumps or bundles of cells and other material (called emboli) get lodged inside the head. A key concern is the recurrence of strokes in the same area as the initial stroke, which unfortunately can lead to a fatality rate of around 65%.
To diagnose strokes, doctors need to distinguish between blockages due to emboli and those due to a decrease in blood flow (hemodynamics). These issues usually show up as classic stroke or mini-stroke symptoms, including physical weakness or loss of feeling on the opposite side of the body, or temporary blindness in one eye. However, less predictable and unusual symptoms may arise due to insufficient blood supply, such as trembling limbs, vision problems, headaches, fainting, and general tiredness. It’s estimated that about one-third of all strokes are related to issues in the neck arteries. Most often, these kinds of strokes are caused by emboli that form at the fork of the neck artery, but decreased blood flow due to narrowing of the arteries can also be a factor. The likelihood of these problems becomes greater as the narrowing of the neck artery worsens.
A surgical intervention called carotid endarterectomy (CEA), which is a procedure to clear out blockages in the carotid artery and increase blood flow, can help those with significant neck artery narrowing. However, the effectiveness of CEA depends on how narrow the artery is, with better results linked to higher narrowing levels. CEA does carry risks, including a 4-7% chance of causing stroke or death within 30 days of surgery mainly due to handling of the blockage inside the artery. Also, it may be hard to gauge the exact risks around the procedure because strokes and mini-strokes naturally carry a certain risk of repeat or death. Therefore, it’s vital to determine at what degree of narrowing, the benefits obtained from undergoing CEA outweigh its risks versus just managing the condition with medication. Proper medication management, involving the use of cholesterol-lowering drugs, blood pressure control, and diabetes management, should be provided to all patients.
The timing of CEA surgery is still a topic of debate due to differing results. Two significant studies from 1991 suggest that CEA for symptomatic neck artery narrowing carried out within 6 months of stroke symptoms reduces the rate of future strokes. Most benefits were seen when surgery was carried out within two weeks after the stroke incident. This led to proposals that CEA should be done within 14 days, and some even advise doing it within 48 hours. However, a 2012 study reported more complications when surgery was done within two days of the stroke, compared to 3-7 days afterward. Recent guidelines propose that if the initial stroke symptom is a mini-stroke, then surgery within 48 hours can be considered. If the initial symptom was a full stroke, surgery can be considered 3-7 days later. However, exceptions can be made for patients who have mini-strokes that are getting worse, who likely benefit from early intervention.
Another challenging area is the presence of significant narrowing in the neck artery in patients who haven’t shown any stroke symptoms for the past six months (known as asymptomatic patients). Three key studies addressed whether CEA could reduce stroke risk in patients with no symptoms but substantial neck artery narrowing. In general, these studies found that stroke incidence was considerably decreased, yet the studies had some limitations.
Given that neck artery narrowing and heart artery disease (CAD) both stem from atherosclerosis (a disease where plaque builds up inside your arteries), it’s unsurprising that a sizable fraction of patients with severe neck artery narrowing also have CAD. If patients known to have severe, but symptom-free, neck artery narrowing need heart bypass surgery (CABG), the question arises as to whether CEA should be done before, during, or after the CABG. A study showed it’s best to perform CEA either before or during CABG compared to performing it 1-3 months after CABG. The latter approach had a notable increase in risk for stroke around the operation or delayed stroke.
What Causes Symptomatic Carotid Artery Stenosis?
Carotid artery stenosis is a condition where the carotid artery, a major blood vessel in the neck, gets narrower. This is usually a result of a condition called atherosclerosis, where fatty deposits build up in the arteries. Anything that increases a person’s risk of developing atherosclerosis, like smoking, having high cholesterol, being male and growing older, can also potentially lead to carotid artery stenosis. This in turn can result in symptoms like a stroke or a transient ischemic attack (TIA), which is a temporary blockage of blood flow to the brain.
However, in a small number of people, especially young women, carotid artery stenosis may be caused by a condition called fibromuscular dysplasia (FMD). FMD is a condition where some of the medium-sized arteries, like the carotid and renal arteries, develop abnormal growth patterns in the artery’s wall. This typically affects the middle and far sections of the carotid artery, and can sometimes extend into the brain. In some cases, FMD can also cause aneurysms, which are bulges in the wall of an artery. For more information on “Carotid Artery Fibromuscular Dysplasia”, please refer to our related article.
Risk Factors and Frequency for Symptomatic Carotid Artery Stenosis
Internal carotid artery occlusion, when it causes symptoms, happens in about 6 out of every 100,000 people. However, we don’t really know how often it occurs without causing symptoms, as we don’t usually check for it if the patient appears well. Both Black and Hispanic patients tend to have a higher risk of having a stroke than White patients, but they are less likely to have severe narrowing (over 70% closed) of the arteries. This might be why these groups are less likely to require a carotid endarterectomy, a surgical procedure to clear the artery. Native Americans, though, are more likely to have severe narrowing than White patients. Also, men are more likely to have carotid artery disease than women.
- Symptomatic internal carotid artery occlusion occurs in about 6 out of every 100,000 people.
- We don’t know how often it happens without causing symptoms.
- Black and Hispanic patients are more at risk of stroke than White patients.
- However, Black and Hispanic patients tend to have less severe artery narrowing.
- This could be why they’re less likely to need surgery to clear the artery.
- Native Americans are more likely to have severe artery narrowing compared to White patients.
- Men are more likely to suffer from carotid artery disease than women.
Signs and Symptoms of Symptomatic Carotid Artery Stenosis
Carotid artery stenosis, a condition where the carotid arteries narrow, shares risk factors with other blood vessel diseases. These include getting older, being male, having a family history of the disease, smoking, high blood pressure, high cholesterol, lack of physical activity, and a diet high in fat. Patients often show new neurological symptoms such as slurred speech, weaknesses in the face or limbs, or vision problems. One common symptom is the temporary loss of vision in one eye due to small clots blocking the retinal arteries.
When diagnosing this condition, doctors should check blood pressure in both arms and also when standing up or sitting down in older patients. A detailed examination of the nervous system should be carried out, including checking the vision of both eyes. However, hearing a whooshing sound in the neck is not always a definitive sign of significant narrowing. A heart examination could reveal an irregular heartbeat or heart murmurs, which could suggest an irregular heartbeat or a heart valve causing strokes. A detailed skin and limb examination should also be conducted to look for signs of blood clots affecting the skin, or reduced blood flow, such as cold limbs, weak or absent pulses, skin discoloration, and hair loss of the affected limb.
Here are the risk factors and symptoms associated with carotid artery stenosis:
- Increased age
- Male sex
- Family history of the disease
- Smoking
- High blood pressure
- High cholesterol
- Lack of physical activity
- Diet high in fat
- New neurological symptoms (e.g., slurred speech, weaknesses in the face or limbs, or vision problems)
- Temporary loss of vision in one eye
Testing for Symptomatic Carotid Artery Stenosis
When a doctor suspects that a patient may have had a stroke, they will perform a physical exam and use special imaging techniques like a CT scan or an MRI to get a detailed picture of the patient’s brain. They’ll then admit the patient to a special ward in the hospital where their heart function can be constantly monitored. This is because only a third of strokes are caused by issues with the carotid artery, which is the main artery supplying blood to the brain. The other two-thirds are caused by problems elsewhere, such as inside the brain itself or blood clots from the heart.
As part of this process, an EKG, a test that monitors heart activity, will be performed. A cardiac echo, an ultrasound of the heart, may also be done to check for possible sources of blood clots, including a condition known as patent foramen ovale, where there’s a hole in the heart.
If the doctor suspects that the stroke may have been caused by the carotid artery becoming narrow (stenosis), they may order a carotid duplex as a first step. This is a non-invasive, inexpensive test that uses sound waves to create pictures of the blood vessels. The results can show whether there’s a blockage in the carotid artery and how severe it is. However, to confirm the diagnosis and plan for possible surgery, the doctor might need to order further tests. These may include a digital subtraction arteriography, magnetic resonance arteriography (MRA), or computed tomographic (CT) arteriography, all of which use a special dye to make the blood vessels easier to see on scans.
In terms of these dye-enhanced scans, a type of MRA that uses a dye called gadolinium is better at showing severe blockages than another type called time-of-flight angiography. An MRI is the best way to not only measure how blocked the artery is, but also examine the condition of the deposit causing the blockage (known as plaque). Characteristics of the plaque that may increase the risk of a stroke include ulceration and cracking, a lipid (fat) core that’s started to die off, and internal blood clots or inflammation.
Treatment Options for Symptomatic Carotid Artery Stenosis
A comprehensive review found that patients with severe narrowing (70% to 99%) in their carotid artery significantly benefited from a procedure called Carotid Endarterectomy (CEA), which is a treatment that clears blocked carotid arteries. Over a 5-year period, these patients showed a decrease in the occurrence of severe strokes, or death during or after the surgery. For patients with moderate narrowing (50% to 69%), the benefits were less but still significant. Interestingly, this benefit was more pronounced in men, as women had higher rates of complications from the surgery. On the other hand, patients with little to no blockage (0% to 49%) experienced more severe strokes or deaths with CEA, compared to those who received only medication management.
Patients with a very slow blood flow in the carotid artery, also known as “trickle flow”, have a different stroke risk level compared to those with severe narrowing in the artery. In the past, the recommendation for these patients has been to stick to optimized medication treatment, but recent studies suggest that improvements in CEA and carotid stent procedures could justify surgical intervention.
It’s important to note that chronic blockage of the carotid artery accounts for about 6.5% of all strokes that occur due to lack of blood supply to the brain. Now, there aren’t specific guidelines on how frequently patients with this condition should be monitored or what degree of narrowing should trigger concern. However, it’s reasonable to check in with these patients every six months to a year, and perhaps conduct an ultrasound scan of the carotid artery. If new symptoms appear, it may be necessary to get imaging done to see if surgery to restore blood flow (revascularization) is needed.
A procedure called Carotid Artery Stenting (CAS), which involves placing a tiny mesh tube called a stent into the carotid artery to improve blood flow, is usually the best option if the patient has multiple health issues—such as needing a breathing tube, having had radiation in the neck, or a tear in the carotid artery. Despite the fact that CAS carries an increased risk of stroke, technological advancements have made the outcome of CAS pretty much on par with CEA for most patients. However, a procedure like CAS may result in more cases of stroke, although typically these are non-disabling, whereas CEA carries a significantly higher risk of a heart attack occurring during the procedure. An ongoing study is expected to provide more clarity on this topic.
In cases where the carotid artery is completely blocked, medical management is usually advised over surgical procedures to restore blood flow. However, in certain circumstances surgical intervention may be considered, depending on individual cases.
What else can Symptomatic Carotid Artery Stenosis be?
When a doctor is trying to diagnose carotid artery stenosis, which is a narrowing of the carotid arteries, several other medical conditions might also need to be considered because they can cause similar symptoms. These include:
- Carotid artery dissection (a tear in the carotid artery)
- Fibromuscular dysplasia (a condition that causes abnormal cell development in the arteries)
- Valvular heart disease (problems with the valves in the heart)
- Arrhythmias, especially atrial fibrillation, which is a heart rhythm problem
- Mural thrombosis (a blood clot in the wall of a blood vessel)
- Takayasu vasculitis (a disease that causes inflammation of the blood vessels)
- Giant cell arteritis (an inflammation of the blood vessels primarily affecting the elderly)
- Complicated migraine (a severe kind of headache)
What to expect with Symptomatic Carotid Artery Stenosis
The possibility of having a follow-up stroke after a successful carotid endarterectomy (CEA – a surgical procedure that removes plaque buildup from the carotid arteries) varies depending on the patient’s initial condition. For those who experienced a transient ischemic attack (TIA – a mini-stroke that doesn’t cause permanent damage), the chance of a stroke occurring in the same hemisphere of the brain is 1% to 2% per year. On the other hand, for those who have already suffered from a full-blown stroke, the risk increases to 2% to 3% per year.
Possible Complications When Diagnosed with Symptomatic Carotid Artery Stenosis
The primary problem after a blockage in the carotid artery that can cause symptoms like a mini-stroke (TIA), full-blown stroke, or other brain issues, is that the stroke is likely to happen again. Other common risks that come with the surgeries used to treat this condition (CEA or CAS) include the likelihood of having a stroke during or near the time of the surgery, as well as general surgical complications.
For patients who don’t show any symptoms of carotid stenosis, but have a blockage in the carotid artery ranging from 70% to 99%, it was estimated in a study that over a period of 5 years, around 4.7% of them would have an acute ischemic stroke on the same side as the blockage. This simply means that these patients are at risk of having a stroke that occurs when the blood supply to part of the brain is blocked.
Common Issues:
- Recurrent stroke
- Stroke near the time of surgery (CEA or CAS)
- Surgical complications
- Increased risk of acute ischemic stroke for asymptomatic patients with 70%-99% blockage
Preventing Symptomatic Carotid Artery Stenosis
If someone has possibly had a stroke or a mini-stroke (known as a TIA), it’s vital to educate both the patient and their loved ones about the typical symptoms. These can include difficulty speaking (dysarthria), numbness, weakness, a tongue that moves to one side, and confusion. It’s common for these symptoms to happen again, so if any new or recurring symptoms appear, it’s important to seek immediate medical help.
Patients should also learn about the importance of taking their medications as instructed, especially those known as antiplatelet agents. These medicines can help prevent future strokes or TIAs. Additionally, it’s advisable to talk about nutrition. Eating foods that are high in cholesterol and fat can increase the risk of having a stroke, so understanding how to avoid these items can play a part in stroke prevention.
