Carotid arteriosclerosis, also known as carotid artery disease or carotid artery stenosis, occurs when the large arteries in your neck that supply blood to your brain become narrowed or blocked. This happens when a sticky substance made of fat and cholesterol, called plaque, builds up inside the artery walls. Over time, this buildup can increase the risk of stroke, a medical emergency that can cause lasting damage or even death.
Understanding the Scale of the Problem
Carotid artery disease affects a significant portion of the population, particularly as people age. Research shows that up to 5 percent of the general population has some degree of carotid artery narrowing, with the condition becoming more common in people over 65 years old. Among individuals older than 65, up to 3 percent have this disease.[2][4]
The importance of this condition cannot be overstated when considering its connection to stroke. Carotid artery disease is responsible for up to one-third of all strokes, and it may account for up to 20 percent of ischemic strokes, which occur when blood flow to the brain is blocked.[4][14] Every year, approximately 700,000 strokes occur in the United States alone, making stroke the fifth leading cause of death in the country. According to recent statistics, stroke causes 1 in every 15 deaths.[4][13]
What makes carotid artery disease particularly concerning is that the risk increases with age. As we grow older, the likelihood of developing this condition rises steadily. The disease usually happens over time, meaning that the damage accumulates gradually, often without any warning signs until something serious occurs.[2][10]
What Causes Carotid Artery Disease
The main cause of carotid artery disease is atherosclerosis, a process often called “hardening of the arteries.” This is a diffuse, degenerative condition that affects blood vessels throughout the body. In atherosclerosis, plaque made up of fat, cholesterol, and other substances begins to accumulate on the inner walls of arteries.[3][4]
Under normal circumstances, the carotid arteries are smooth and open, similar to clean pipes that allow fluid to flow freely without obstruction. However, over time, these arteries can build up plaque, which narrows the inside opening where blood flows and makes the artery walls stiff. This plaque buildup typically occurs at a point where the carotid artery splits, or bifurcates, into two branches: the internal carotid artery, which supplies blood to the brain, and the external carotid artery, which supplies the neck, face, and scalp.[2][11]
The process of plaque formation often begins in childhood. Healthy, clear arteries slowly start to change as excess low-density lipoprotein (LDL) cholesterol, often called “bad” cholesterol, begins to accumulate in the blood vessel walls. The body sends inflammatory cells to the area to help, but over time, the LDL cholesterol gets trapped and sticks to the outside of the blood vessel. This ongoing process eventually leads to the formation of plaque that continues to grow.[11][19]
Although the exact trigger for plaque development is not entirely clear, researchers understand that this buildup is a chronic condition that typically affects people as they age. The plaque itself is composed of necrotic cells, lipids, and cholesterol crystals, forming a complex structure that can cause stenosis, embolization, and thrombosis.[3]
In some cases, carotid artery narrowing can result from causes other than typical atherosclerosis. For example, patients who have undergone radiation treatment for head and neck cancers can develop carotid artery stenosis from the effects of radiation rather than from plaque development. Additionally, certain inflammatory conditions can cause irregularities in the carotid arteries.[11]
Who Is at Greater Risk
Several factors can significantly increase your chances of developing carotid artery disease over time. Some of these risk factors are within your control, while others are not. Understanding these factors is important because they often contribute to and compound one another, accelerating the disease process.[2][10]
Age is one of the most important non-modifiable risk factors. As people grow older, their arteries naturally undergo changes, and the risk for both carotid artery disease and stroke increases steadily. The older you are, the more time plaque has had to accumulate in your arteries.[4][7]
Genetics and family history also play a role. If you have close family members who have experienced stroke, heart disease, or vascular problems, your own risk may be higher. Men are somewhat more likely to develop this condition, although the risk for women increases after menopause.[7]
Among the modifiable risk factors, smoking and tobacco use stand out as particularly harmful. Smoking cigarettes makes it significantly more likely that fatty deposits will form in your arteries. Additionally, plaques may grow bigger and faster in people who smoke.[2][10][19]
High blood pressure, or hypertension, is another major risk factor. When blood pressure is elevated, it causes tears and damage in the artery walls. LDL cholesterol can then settle into these damaged areas more easily, accelerating plaque formation.[2][10][19]
High cholesterol levels in the blood directly contribute to plaque buildup. LDL cholesterol is heavily involved in the formation of atherosclerotic plaques, while high-density lipoprotein (HDL) cholesterol, often called “good” cholesterol, helps clear LDL from the arteries. High triglyceride levels, especially when combined with high LDL or low HDL levels, can also lead to atherosclerosis.[4][19]
Diabetes is a significant risk factor because it affects how the body processes cholesterol and damages blood vessels over time. People with diabetes are at increased risk for developing carotid artery disease and experiencing complications.[2][4][10]
Lifestyle factors such as obesity and a sedentary lifestyle also contribute to the development of carotid artery disease. Being overweight raises LDL cholesterol levels and lowers HDL cholesterol levels. Lack of physical activity has a similar effect, reducing the amount of beneficial HDL cholesterol available to clear your arteries. A diet high in saturated fats further increases cholesterol levels and accelerates plaque formation.[2][4][7][19]
Having chronic kidney disease is another factor that can increase risk. Additionally, if you already have heart disease, you are more likely to have carotid artery disease as well, since atherosclerosis often affects multiple parts of the circulatory system simultaneously.[4][5]
Recognizing the Warning Signs
One of the most challenging aspects of carotid artery disease is that in its early stages, it often causes no symptoms at all. Many people have significant narrowing of their carotid arteries without feeling anything unusual. You might not notice any symptoms until the condition becomes serious enough to deprive the brain of blood. This is why the first sign of carotid artery disease for many people is a stroke or a transient ischemic attack (TIA), sometimes called a “mini-stroke.”[1][2][4]
A TIA is a temporary shortage of blood flow to the brain. Unlike a full stroke, a TIA does not cause permanent damage and cannot be detected on MRI or CT scans. However, TIA symptoms are usually a warning sign that a more serious stroke may be coming soon. The symptoms of a TIA typically last only a few minutes to a few hours, but they should always be treated as serious medical emergencies requiring immediate attention.[2][4][10]
The symptoms of both TIA and stroke are similar and depend on which part of the brain is being affected. Sudden numbness or weakness in the face, arm, or leg is common, especially on one side of the body. This can manifest as a drooping of one side of the face, an inability to control movement of a body part, or a loss of feeling on one side.[1][2][4]
Speech difficulties are another major warning sign. You might have sudden trouble speaking clearly, experience slurred speech, have difficulty forming words, or find it hard to understand what others are saying to you. The words may come out garbled or completely inappropriate.[1][4]
Vision problems can occur suddenly. Some people experience loss of vision or severe blurring in one or both eyes. A specific symptom called amaurosis fugax involves transient loss of vision in one eye, which feels like a dark shade coming down over your field of vision. This happens when the eye is temporarily deprived of blood flow.[2][3]
Other symptoms include sudden dizziness, loss of balance, or lack of coordination that makes it difficult to walk. Some people experience a sudden, severe headache with no known cause.[1][4]
An important detail about these symptoms is that they typically affect the opposite side of your body from where the blockage is located. For example, if you have carotid stenosis on the left side of your neck, the symptoms will usually appear on the right side of your body.[11]
In some cases, carotid artery disease is discovered accidentally during a routine physical examination. A doctor might hear an abnormal sound, called a bruit, when listening to your neck with a stethoscope. This swooshing sound is caused by disturbed blood flow through the narrowed carotid artery. The presence of a bruit may prompt your doctor to order imaging tests even if you have no symptoms.[7][8][17]
Steps You Can Take to Prevent the Disease
Prevention of carotid artery disease centers on addressing the risk factors that contribute to plaque buildup and atherosclerosis. Many of these preventive measures involve lifestyle changes that benefit your overall cardiovascular health.[6][16]
Quitting smoking is one of the most important steps you can take. Smoking cessation significantly reduces your risk of developing carotid artery disease and slows the progression of existing plaque. The benefits begin almost immediately after you stop using tobacco products.[6][12][19]
Maintaining a healthy weight through proper diet is crucial. Dietary modifications should include reducing saturated fats and trans fats by eating less red meat, fried foods, and dairy products made with whole milk. Instead, choose healthy oils, fruits, vegetables, whole grains, poultry, fish, and nuts. Reducing salt intake helps control blood pressure. Eating high-fiber foods can lower cholesterol by as much as 10 percent.[6][9][19]
Regular physical activity is essential for prevention. Being sedentary lowers your HDL cholesterol levels, leaving less of the beneficial cholesterol available to clear your arteries. Exercise such as brisk walking, cycling, or other activities for 40 minutes three or four times a week can help lower both cholesterol and blood pressure. Even modest weight loss of about 10 percent of your body weight can significantly improve your cholesterol numbers.[6][19]
Controlling blood pressure and cholesterol through lifestyle changes and, when necessary, medications is vital. You should know your cholesterol levels and blood pressure numbers, and work with your healthcare provider to keep them within healthy ranges.[9][19]
For people with diabetes, maintaining good blood glucose control is important to prevent vascular complications. This involves monitoring blood sugar levels, taking medications as prescribed, and following a diabetes-friendly diet.[9]
Regular health screenings and check-ups can help detect carotid artery disease early, even before symptoms develop. Your doctor may recommend a screening test if you have multiple risk factors or a family history of stroke or vascular disease. Early detection allows for earlier intervention to prevent progression and complications.[4]
How the Disease Changes Normal Body Function
To understand how carotid artery disease affects the body, it helps to know the normal anatomy and function of the carotid arteries. You have two carotid arteries, one on each side of your neck. These are large blood vessels that carry oxygen-rich blood from the heart up through the neck to the brain, face, and head. Interestingly, four out of five people can survive with just one functioning carotid artery because once these arteries reach the brain, they join with other arteries that can share the workload of supplying blood to both sides of the brain. However, the way these arteries connect can differ from person to person.[2][10][11]
When carotid artery disease develops, the pathophysiology follows a predictable pattern. The process typically begins with damage to the inner lining of the artery, called the endothelium. This damage can be caused by high blood pressure, smoking, diabetes, or other factors. Once the endothelium is damaged, LDL cholesterol particles can penetrate the artery wall more easily.[5]
As LDL cholesterol accumulates in the artery wall, the body’s immune system responds by sending white blood cells to the area. These cells try to engulf the cholesterol, but they become overwhelmed and turn into foam cells. Over time, these foam cells, along with cholesterol, calcium, and cellular debris, form a growing plaque. A fibrous cap develops over this lipid-filled core, creating what is known as an atherosclerotic plaque.[5]
As the plaque grows larger, it progressively narrows the lumen, or inside opening, of the carotid artery. This narrowing changes how blood flows through the vessel. The blood has to move faster through the narrowed section, creating turbulence. This is what causes the bruit sound that doctors can sometimes hear with a stethoscope.[8][17]
The stenosis itself can lead to stroke through three main mechanisms. First, if the narrowing becomes severe enough, it may significantly restrict blood flow to the brain. However, this rarely causes stroke by itself because of how well the brain’s arteries can share blood supply. Second, and more commonly, pieces of the plaque can break off from the carotid artery and travel up to the brain as emboli. These emboli can block smaller arteries in the brain, cutting off blood supply to a portion of brain tissue. Third, blood clots can form on the surface of the plaque because the irregular surface promotes clotting. These clots can also break loose and travel to the brain, or they can become wedged in the already narrowed carotid artery.[11][15]
When a stroke occurs, brain tissue is permanently damaged because neurons begin to die within minutes of being deprived of oxygen and nutrients. This is why stroke is called an ischemic stroke when it results from blocked blood flow. The severity of the damage depends on how long the brain tissue goes without blood and which area of the brain is affected.[2][10]
The stenosis is often reported as a percentage, which indicates how much of the artery’s normal opening is blocked by plaque. This percentage helps doctors estimate stroke risk. Generally, the higher the percentage of stenosis, the greater the risk of stroke. Symptomatic patients with greater than 70 percent stenosis have a particularly high risk, while those with 50 to 69 percent stenosis have a more moderate risk. Asymptomatic patients with greater than 60 percent stenosis also have elevated risk, though it is lower than for symptomatic patients.[3][12]
The condition can affect one or both carotid arteries. When both arteries are involved, the risk of complications is higher. Without proper medical care, carotid artery stenosis tends to worsen over time, progressively increasing the risk of stroke and its potentially devastating complications, including disability and death.[2][10]
