Carotid Artery Stenosis
Carotid artery stenosis is a narrowing of one or both carotid arteries, the major vessels in the neck that supply blood to the brain. The most common cause is atherosclerotic plaque buildup. Carotid stenosis is an important contributor to stroke risk, although many patients have no symptoms. Imaging—particularly carotid ultrasound, CT angiography, and MR angiography—is used to identify and grade carotid stenosis, and management combines aggressive cardiovascular risk reduction with, in selected patients, procedures such as carotid endarterectomy or stenting.
What is it?
The carotid arteries are two major vessels in the front of the neck—one on each side—that supply most of the blood to the brain. Each carotid artery branches into an internal carotid artery (which supplies the front and middle parts of the brain) and an external carotid artery (which supplies the face and scalp). Carotid artery stenosis is a narrowing of one or both of these arteries, most often at the point where the common carotid splits into the internal and external branches. Narrowing reduces blood flow to the brain and provides a site where plaque can break apart and release small clots or debris that travel into the brain.
The most common cause of carotid stenosis is atherosclerosis—the buildup of cholesterol, inflammatory cells, smooth muscle, and calcium within the artery wall, the same process that causes coronary artery disease and peripheral arterial disease. Less common causes include fibromuscular dysplasia (a non-atherosclerotic vessel wall disease, more common in women and at younger ages), carotid artery dissection (a tear within the artery wall, sometimes associated with trauma or sudden neck movement), inflammatory vasculitis, prior radiation to the neck, and rare congenital or genetic conditions.
The clinical importance of a carotid stenosis depends on its severity, location, plaque characteristics, the patient’s overall vascular and brain health, and whether it has caused symptoms. Carotid stenoses are commonly graded as mild, moderate, severe, or critical based on the percentage narrowing, often measured using methods such as the NASCET criteria. Important plaque features—such as ulceration, hemorrhage within the plaque, and a lipid-rich core—can influence the risk of stroke and may be assessed on advanced imaging.
Many patients with carotid artery stenosis have no symptoms, particularly when narrowing is mild or moderate, and the diagnosis is made on screening tests or imaging done for other reasons. Sometimes a neck bruit—a whooshing sound heard with a stethoscope over the carotid artery—is the first clue. Symptomatic carotid stenosis can present as a transient ischemic attack (TIA), with brief episodes of weakness, numbness, or sensory changes on one side of the body; sudden loss of vision in one eye (amaurosis fugax); difficulty speaking; or other brief neurological symptoms that resolve within minutes to hours. Stroke—sudden, persistent neurological symptoms—can occur when plaque debris or a clot blocks an artery in the brain. The risk of stroke is higher in patients with symptomatic stenosis, more severe narrowing, and higher-risk plaque features.
Carotid ultrasound (duplex ultrasonography) is often the first-line imaging test because it is widely available, accurate for many cases, and does not use radiation or contrast. CT angiography provides detailed three-dimensional images of the carotid arteries and is especially useful for surgical or interventional planning. MR angiography provides similar information and is particularly useful when avoiding iodinated contrast or radiation is preferred; certain MRI techniques can also characterize plaque composition. Invasive catheter-based angiography is reserved for selected patients, often at the time of planned intervention. Brain imaging (MRI or CT) is commonly used to evaluate for prior strokes, particularly in patients with symptoms.
Important to Know
Management of carotid artery stenosis depends on the severity of narrowing, whether it has caused symptoms, and the patient’s overall cardiovascular risk and health. Because carotid stenosis is a marker of widespread atherosclerosis, treatment focuses both on reducing stroke risk and on preventing heart attack and other cardiovascular events.
Aggressive risk factor management is foundational for all patients. This includes statins and other lipid-lowering therapies, antiplatelet medications (such as aspirin or clopidogrel in selected patients), control of blood pressure and diabetes, treatment of atrial fibrillation when present, smoking cessation, regular physical activity, a heart-healthy diet, weight management, treatment of sleep apnea, and limited alcohol. Modern medical therapy has substantially reduced the risk of stroke in patients with asymptomatic carotid stenosis, even at significant degrees of narrowing.
For symptomatic carotid stenosis, the risk of recurrent stroke is significantly higher, and prompt evaluation is essential. Patients with recent TIA or non-disabling stroke and significant ipsilateral carotid stenosis often benefit from revascularization—either carotid endarterectomy (a surgical procedure to remove the plaque) or carotid artery stenting (a catheter-based procedure)—performed within a short time after the event by experienced teams. The choice between these procedures depends on anatomy, age, surgical risk, anatomy, and patient preferences.
For asymptomatic carotid stenosis, decisions are more individualized. Patients with very severe asymptomatic stenosis, high-risk plaque features, or limited collateral circulation may be considered for revascularization in selected centers with low procedural risk, while others may be managed with optimized medical therapy alone. Ongoing follow-up with imaging and clinical evaluation is important to detect progression and to guide management.
Acute stroke requires immediate emergency evaluation. Early treatment—including, in eligible patients, intravenous thrombolysis or endovascular thrombectomy—is essential to maximize recovery.
Care is typically coordinated by primary care clinicians, neurologists (especially vascular neurology specialists), cardiologists, vascular surgeons, neurosurgeons, interventional radiologists, and others. Imaging findings are interpreted alongside symptoms, examination, and other test results.
Patient education is important. Recognizing the warning signs of TIA and stroke—using tools such as the BE-FAST acronym (Balance, Eyes, Face, Arm, Speech, Time)—and seeking immediate emergency care can make a significant difference in outcomes.
Red flag symptoms include sudden weakness or numbness on one side of the body, sudden difficulty speaking or understanding, sudden vision loss or visual changes, sudden severe headache, sudden loss of balance or coordination, sudden confusion, or any other sudden neurological change. These warrant immediate emergency evaluation, as they may indicate a stroke or TIA.