What is Carotid Bruit?
A carotid bruit is a sound related to the flow of blood in the carotid artery. This sound is often heard with a stethoscope when the blood flow becomes irregular due to narrowing in the area. This could indicate that the artery is partially blocked, which could lead to a stroke. Strokes are a significant cause of illness, death, and loss of physical abilities.
A large percentage of strokes that cut off blood supply (ischemic strokes) are caused by plaque buildup in the carotid artery. Therefore, detecting this condition early on can help reduce the risk of stroke. Because listening for a carotid bruit is a simple and non-invasive procedure, it is frequently used during physical exams, especially for those who are at a higher risk for stroke, like older individuals.
What Causes Carotid Bruit?
Arteries coming from the aortic arch vessels often contain atherosclerotic lesions, which are plaque deposits that narrow the artery. About 80% of these are found where the common carotid arteries split. Doctors listen to the carotid artery during a checkup to determine if it’s narrow, as this might increase the patient’s risk of having a stroke. In cases where the carotid artery is narrowed by 2mm, a sound known as a carotid bruit can be heard 70%-89% of the time.
However, a narrow carotid artery isn’t the only cause of a bruit. Similar sounds can be produced by valvular heart murmurs that reach the neck, cervical venous hums, and inner cranial abnormal connections between arteries and veins.
In some cases, a bruit can be heard in normal or non-narrowed arteries caused by the artery twisting or kinking or by increased blood flow. For instance, in patients with thyrotoxicosis, blood flow to the enlarged thyroid gland can increase up to ten-fold, causing a systolic bruit right on the gland. Similarly, a rare occurrence of having a carotid bruit might occur due to a unique aortic arch structure (bovine-type) and compression of the carotid arteries by a goiter (an enlarged thyroid gland) that’s located behind the breastbone.
Additionally, a bruit can be caused by something pressing on the vessel externally and blocking it, such as carotid body tumors or carotid paraganglioma. The sound can also result from the disruption of blood vessels in a carotid artery dissection. Even inflammation of the carotid vessel due to inflammatory conditions like Takayasu arteritis can lead to carotid bruit.
Non-hardening and non-inflammatory conditions like fibromuscular dysplasia (FMD) can also cause a bruit. FMD most commonly affects the internal carotid arteries and can be found unexpectedly during a checkup. Mostly, cervical FMD doesn’t show any symptoms.
Risk Factors and Frequency for Carotid Bruit
A carotid bruit is a symptom that greatly varies in how often it is found. It can occur anywhere between 24% to 84% of the time. About 5% of people aged 45 to 80, who don’t have serious carotid disease, will have this symptom. Even if a carotid bruit is detected, only around one-third of those people will have significant blockages in their carotid arteries (70% to 90% blockage). Moreover, among patients with large carotid narrowing, only half will have a carotid bruit. This symptom is also found in around 20% of healthy children under 15. In people diagnosed with cervical fibromuscular dysplasia (FMD), a certain type of neck condition, nearly 22% have been found to have carotid bruits, although they usually don’t show any signs of this condition.
Signs and Symptoms of Carotid Bruit
Checking for the risk of strokes involves a thorough interview and a focused physical exam. The best positions for listening for carotid bruits (abnormal sounds made by blood flow), are when the patient is laying down or sitting. If the patient is sitting, the best way to feel and listen to the carotid arteries is from behind the patient. With the patient’s chin pointing straight ahead, the bell of the stethoscope is placed over each carotid artery, covering the skin. The patient is then asked to take a deep breath and hold it without straining for 15 to 30 seconds. The doctor listens during, and a short time after, the patient holds their breath. Holding breath not only gets rid of other distracting sounds but it also makes a carotid bruit more noticeable.
Testing for Carotid Bruit
If a doctor detects a carotid bruit, it might suggest the presence of carotid artery disease. However, a carotid bruit alone can’t diagnose these issues because it isn’t always consistent or accurate enough. When a bruit is found, the next step is to determine if additional tests or referrals are necessary. This decision usually depends on the patient’s vascular risk factors and/or any signs and symptoms indicative of related diseases.
To confirm the diagnosis and get a detailed picture of the condition, imaging studies are often used. These could include a carotid ultrasound, a computed tomography angiography (CTA), or a magnetic resonance angiography (MRA) of the neck. These tests could also provide much-needed information if surgery is needed.
Specialists, such as neurologists and cardiologists, are often involved in this process to ensure comprehensive care.
Treatment Options for Carotid Bruit
Once it’s confirmed that the carotid artery disease is causing the abnormal sound in the carotid artery (bruit), the medical and surgical treatment should start based on how severe the narrowing of the artery is (stenosis), whether the patient has neurological symptoms or not, and the presence of other medical conditions in the patient.
What else can Carotid Bruit be?
When diagnosing certain medical conditions, doctors also need to consider a variety of other potential issues that can have similar symptoms. Here’s a list of them:
- Heart valve problems that cause abnormal sounds, called murmurs
- Inflammation of the carotid artery, major blood vessels in your neck, known as carotid artery vasculitis
- Tumors in the carotid body, a cluster of cells in your neck that helps regulate the amount of oxygen and carbon dioxide in your blood
- Carotid dissection, a tear in the carotid artery that can lead to a stroke
- Narrowing of the carotid artery, also known as carotid stenosis
- Cervical fibromuscular dysplasia, a condition that causes the arteries in your neck to narrow
- A noise that can be heard when blood flows through the veins in your neck, known as a cervical venous hum
- Pressure being put on the carotid artery from the outside, which is called extrinsic compression of the carotid artery
- Medical conditions, like having an overactive thyroid (thyrotoxicosis), that can cause a large amount of blood to go to your heart
- Arteriovenous malformations, abnormal connections between arteries and veins in your brain
Each possibility should be carefully considered so that the most accurate diagnosis can be reached.
What to expect with Carotid Bruit
While carotid bruits, or abnormal sounds of flowing blood are generally seen as signs of widespread atherosclerosis (hardening and narrowing of the arteries), the information does not demonstrate them as strong indicators of potential strokes or other brain-related events. However, listening to carotid bruits can help choose patients who would significantly benefit from a thorough assessment of their heart disease risk and targeted treatments.
Possible Complications When Diagnosed with Carotid Bruit
Every year, 1 to 3 percent of people with no symptoms but who have abnormal sounds (bruits) in their arteries end up experiencing a cerebrovascular accident, also known as a stroke. Globally, stroke is the number two cause of death. In the United States, it’s the third most common reason people die. It’s important to note that issues with the carotid artery (one of the main blood vessels in the neck that supply blood to the brain) plays a role in 15 to 20% of all strokes caused by a lack of blood supply (ischemic strokes).
Preventing Carotid Bruit
It’s important for patients to know that although the sound of a bruit (an abnormal noise heard during a medical exam) is not a sure sign of cerebrovascular disease (a group of conditions that affect the circulation of blood to the brain), it indicates that they may need to make significant changes to their lifestyle and perhaps undergo treatment. Doctors will need to customize these changes and treatments for each patient and emphasize how vital it is for them to stick to the plan.
