Carotid Artery: Structure, Collateral Circulation, Clinical Importance, Related Diseases, Causes, Symptoms and Treatment

They are arteries that supply the head and neck with oxygenated blood. They divide in the neck to form the external and internal carotid arteries.

Structure of the carotid artery

The common carotid arteries are present on the left and right sides of the body. These arteries originate from different arteries, but follow symmetrical courses.

The right common carotid arises in the neck from the brachiocephalic trunk; the left from the aortic arch in the thorax. These divide into the external and internal carotid arteries at the upper border of the thyroid cartilage, around the level of the fourth cervical vertebra.

The left common carotid artery can be thought of as having two parts: a thoracic (chest) and a cervical (neck) part. The right common carotid originates from or near the neck, thus containing only a small thoracic portion.

There are studies in the bioengineering literature that have investigated the characterization of the geometric structure of the common carotid artery from both a qualitative and mathematical (quantitative) point of view.

The mean diameters of the common carotids in adult males and females are 6.5 mm and 6.1 mm respectively.

On the chest

Only the left common carotid artery has a substantial presence in the chest. It originates directly from the aortic arch and travels up through the superior mediastinum to the level of the left sternoclavicular joint.

During the thoracic part of its course, the left common carotid artery is related to the following structures:

In the front it is separated from the manubrium of the sternum by the sternohyoid and sternothyroid muscles, the anterior portions of the left pleura and lung, the left brachiocephalic vein, and the remnants of the thymus.

At the back is the trachea, esophagus, left recurrent laryngeal nerve, and thoracic duct.

On its right side below is the brachiocephalic trunk, and above, the trachea, the inferior thyroid veins, and the remains of the thymus; to its left side are the left vagus and phrenic nerves, the left pleura, and the lung. The left subclavian artery is posterior and slightly lateral to it.

In the neck

The cervical portions of the common carotids resemble each other so much that one description applies to both.

Each vessel passes obliquely upward, from behind the sternoclavicular joint to the level of the upper border of the thyroid cartilage, where it divides.

In the lower part of the neck the two common carotid arteries are separated from each other by a very narrow interval that contains the trachea; but at the top, the thyroid gland, larynx, and pharynx separate the two arteries.

The common carotid artery is contained in a sheath known as the carotid sheath, which is derived from the deep cervical fascia and also encloses the internal jugular vein and the vagus nerve, the vein that lies lateral to the artery and the nerve between the artery and the vein, in a plane posterior to both.

When opening the sheath, each of these three structures has a separate fibrous covering. At approximately the level of the fourth cervical vertebra, the common carotid artery divides (“bifurcates” in the literature) into an internal carotid artery (AIC) and an external carotid artery (ACE).

While both branches travel upward, the internal carotid takes a deeper (more internal) path, eventually traveling into the skull to supply the brain. The external carotid artery moves closer to the surface and expels numerous branches that supply the neck and face.

In the lower part of the neck, the common carotid artery is very deeply seated, being covered by the integument, superficial fascia, platysma muscle, deep cervical fascia, sternocleidomastoid muscle, sternohyoid, sternothyroid and omohyoid.

In the upper part of its course it is more superficial, being covered merely by the integument, the superficial fascia, the platysma, the deep cervical fascia, and the medial margin of the sternocleidomastoid.

When the sternocleidomastoid muscle is pulled back, the artery is seen to be contained in a triangular space known as the carotid triangle.

This space is limited behind by the sternocleidomastoid, above by the stylohyoid and posterior belly of the digastric muscle, and below by the superior belly of the omohyoid.

This part of the artery is crossed obliquely, from its medial side to its lateral side, by the sternocleidomastoid branch of the superior thyroid artery; It is also crossed by the superior and intermediate thyroid veins (which end in the internal jugular vein).

Descending in front of its envelope is the descending branch of the hypoglossal nerve, this filament being joined by one or two branches of the cervical nerves, which obliquely cross the vessel. Sometimes the descending branch of the hypoglossal nerve is contained within the sheath.

The superior thyroid vein crosses the artery near its termination, and the middle thyroid vein a little below the level of the cricoid cartilage; the anterior jugular vein crosses the artery just above the clavicle, but is separated from it by the sternohyoid and the sternothyroid.

Behind, the artery is separated from the transverse processes of the cervical vertebrae by the longus colli and longus capitis muscles, with the sympathetic trunk interposing between it and the muscles. The inferior thyroid artery crosses behind the lower part of the vessel.

Medially, it is in relation to the intervening esophagus, trachea and thyroid gland (which overlaps), inferior thyroid artery, and recurrent laryngeal nerve; higher up, with the larynx and pharynx. Lateral to the artery, within the carotid sheath with the common carotid, are the internal jugular vein and the vagus nerve.

In the lower part of the neck, on the right side of the body, the right recurrent laryngeal nerve crosses obliquely behind the artery; the right internal jugular vein deviates from the artery.

On the left side, however, the left internal jugular vein approximates and often overlaps the lower part of the artery.

Behind the bifurcation angle of the common carotid artery is a reddish-brown oval body known as the carotid body. It is similar in structure to the coccygeal body which is located in the middle sacral artery.

The relationships of the cervical region of the common carotid artery can be discussed on two points:

  • Internal relations of the organs present within the carotid sheath.
  • Two external relations of the carotid sheath.

Collateral circulation

After ligation of the common carotid, the collateral circulation can be perfectly established, by the free communication that exists between the carotid arteries on opposite sides, both inside and outside the skull, and by the enlargement of the branches of the subclavian artery in the side corresponding to that on which the glass has been tied.

The main communications outside the skull are between the superior and inferior thyroid arteries, and the deep cervical artery and the descending branch of the occipital artery; the vertebral artery takes the place of the internal carotid artery within the skull.



The right common carotid may arise above the level of the superior border of the sternoclavicular joint; this variation occurs in approximately 12 percent of cases.

In other cases, the right-sided artery may arise as a separate branch from the arch of the aorta or together with the left carotid. The left common carotid varies in origin more than the right.

In most abnormal cases it presents with the brachiocephalic trunk; if that artery is absent, the two carotids are generally presented by a single trunk. It rarely joins the left subclavian artery, except in cases of transposition of the aortic arch.

Split point

In most abnormal cases, the bifurcation occurs higher than normal, the artery divides in the opposite direction or even above the hyoid bone.

More rarely, it occurs below, in the opposite direction to the middle of the larynx, or to the lower border of the cricoid cartilage. In at least one reported case, the artery was only 4 cm long and divided at the root of the neck.

Very rarely, the common carotid artery ascends in the neck without any subdivision, whether the external or internal carotid is absent; and in a few cases the common carotid has been found to be absent, the external and internal carotids arising directly from the arch of the aorta.

This peculiarity existed on both sides in some cases, and in others.

Occasional branches

The common carotid usually does not shed any branches before its bifurcation, but occasionally gives rise to the superior thyroid artery or its laryngeal branch, the ascending pharyngeal artery, the inferior thyroid artery, or, more rarely, the vertebral artery.

Clinical significance

The common carotid artery is often used to measure the pulse, especially in patients who are in shock and lack a detectable pulse in the more peripheral arteries of the body.

The pulse is taken by palpating the artery just to the anterior border of the sternocleidomastoid muscle at the level of the superior border of the thyroid cartilage.

The presence of a carotid pulse has been estimated to indicate a systolic blood pressure of more than 40 mmHg, given by the 50% percentile.

It is a syndrome characterized by pain in the carotid artery near the bifurcation. Carotid stenosis can occur in patients with atherosclerosis.

The thickness of the wall of the carotid artery is a marker of subclinical atherosclerosis, which increases with age and with long-term exposure to particulate air pollution.

What is carotid artery disease?

The carotid arteries are the main blood vessels that carry blood to the brain. A carotid artery is located on each side of the neck. When your doctor puts his hands on your neck to detect a pulse, he is feeling one of your carotid arteries.

Carotid artery disease occurs when a blockage in one or both of these arteries decreases the amount of blood flow to your brain. This can lead to a stroke.

According to the Centers for Disease Control and Prevention, more than 795,000 people suffer a stroke each year in the United States.

Most of these strokes are caused by either carotid artery disease or atrial fibrillation, which is an irregular heartbeat.

The National Heart, Lung, and Blood Institute notes that carotid artery disease causes more than half of all strokes in the United States.

What Causes Carotid Artery Disease?

Carotid artery disease is typically caused by atherosclerosis, a disease in which plaque builds up in the arteries.

A similar buildup occurs in the blood vessels of the heart when someone has coronary artery disease. The plate contains clumps of:

  • Cholesterol.
  • Grease.
  • Cell waste.
  • Proteinaceous.
  • Calcic.

Atherosclerosis can make your carotid arteries narrow and less flexible over time. This limits the amount of blood flow to your organs.

Carotid artery disease can also be the result of other diseases that cause arterial damage.

Risk factors for carotid artery disease

Some conditions can damage the arteries and increase the risk of carotid artery disease:

The high blood pressure can weaken the walls of your arteries and make them more prone to dañarse.El High cholesterol is a major risk factor for atherosclerosis.

Diabetes can affect your body’s ability to process blood sugar. It increases your risk of high blood pressure and atherosclerosis. Obesity increases the risk of diabetes, high blood pressure, and atherosclerosis.

Physical inactivity contributes to hypertension, diabetes, and obesity. Smoking can irritate the lining of your arteries. It can also increase your heart rate and blood pressure.

Advanced age makes your arteries stiffer and more susceptible to damage. A family history of atherosclerosis is associated with an increased risk of carotid artery disease.

Symptoms of carotid artery disease

Early carotid artery disease rarely causes symptoms. Symptoms are likely to only appear once one of the carotid arteries has become completely or nearly blocked.

A carotid artery is generally considered to be nearly blocked when it is more than 80 percent blocked. At that time, you are at high risk for having a transient ischemic attack (TIA) or stroke.

A transient ischemic attack is also known as a mini attack because it causes stroke symptoms that last from a few minutes to a few hours. These symptoms include:

  • Sudden weakness or numbness in the face, arms, or legs (usually on one side of the body).
  • Problems speaking (fuzzy speech) or understanding.
  • Sudden vision problems in one or both eyes.
  • Dizziness.
  • Sudden and severe headache.
  • That leans to one side of the face.

Call your local emergency number or go to the emergency room immediately if you experience any of these symptoms. They could be signs of a medical emergency.

Tests to detect carotid artery disease

If you fall into a high-risk group for this disease, your doctor will want to examine you for early signs of damage.

During a physical exam, the doctor will listen to the arteries in the neck with a stethoscope to detect a buzzing sound called a murmur. This is a sign that there is a possible narrowing in the carotid vessels.

The doctor can also evaluate strength, memory, and speech. There are also additional tests that can be used to detect carotid artery disease:

Carotid ultrasound

This noninvasive test uses sound waves to measure the flow and pressure of the blood in the blood vessels.

Computed tomography angiography

This is a way of taking X-ray pictures of your blood vessels. A dye called contrast is placed in the blood vessels. The CT scanner then takes pictures from various angles.

Computed tomography of the head

A head CT scan takes pictures of brain tissue to check for bleeding or abnormalities.

Magnetic resonance angiography

An MRI angiogram also uses contrast to highlight the arteries in the neck and brain. The three-dimensional images are then taken using a high-powered magnet.

Cerebral angiography

For cerebral angiography, the doctor will insert a thin, flexible tube called a catheter into the carotid artery. Contrast dye is injected, and then an X-ray is taken to see any abnormalities. This test is more invasive than other forms of imaging, making it more risky.

What are the complications associated with carotid artery disease?

A stroke is the main potential complication of this disease. A stroke occurs when blood flow to the brain is cut off. This can lead to the loss of

A stroke is the main potential complication of this disease. A stroke occurs when blood flow to the brain is cut off. This can lead to loss of brain function or even death.

Carotid artery disease can cause a stroke in several ways:

Narrow carotid arteries may not supply enough blood to the brain. A piece of plaque can break off and lodge in one of the smallest arteries in the brain, blocking blood flow.

Blood clots can form in the carotid artery, blocking blood flow. Blood clots can break away from inside the carotid artery and block a smaller artery in the brain.

How is carotid artery disease treated?

Your doctor will base your treatment plan on your symptoms and whether or not you’ve had a stroke.

If you are diagnosed with carotid artery disease before you have a stroke, your doctor will suggest that you make preventive lifestyle changes. These include:

  • Give up smoking.
  • Get regular exercise.
  • Eating healthy food.
  • Manage any chronic conditions, such as heart disease and diabetes.
  • Take medications as prescribed.

Treatment is more invasive if you are diagnosed with carotid artery disease after having a stroke.

The doctor may need to open the carotid artery to remove the blockage. There are two different ways to do this.

Carotid endarterectomy is the most common form of surgery for severe carotid artery disease. After the anesthesiologist gives you local or general anesthesia, the doctor will make an incision in the front of your neck.

They will open the carotid artery and remove any blockage. The doctor will stitch up the artery and close it. This procedure can have a long-lasting effect in preventing strokes.

A carotid artery stent is the other option. Your doctor will use a carotid artery stent if the blockage is inconveniently located, if you have a large blockage, or if you have other serious health problems that make you a high-risk surgical candidate.

A stent is a small coil of wire. In this procedure, the doctor uses a balloon to widen a narrow section of the artery. They then place a stent inside to keep the artery open.

Long-term outlook for carotid artery disease

Your long-term prognosis will depend on the extent of your disease. However, there are things you can do to improve your health. These include:

Check your blood pressure regularly. Check your blood sugar and cholesterol levels once or twice a year. Attend regular check-ups with your doctor.

Take an annual carotid Doppler ultrasound (if you have had a previous stroke), which is a short, painless test that allows the doctor to see the blood flow through the carotid arteries.

Can carotid artery disease be prevented?

There are steps you can take to lower your chances of developing carotid artery disease:

Quitting smoking can lower your risk of stroke to that of a non-smoker within a few years. Limiting cholesterol and fat in your diet will reduce your risk of atherosclerosis.

Exercising regularly helps lower blood pressure, increase good cholesterol levels, and improve heart health.

Cutting back on alcohol can improve your heart health. Maintaining a healthy weight can lower your risk of developing carotid artery disease.

Managing diabetes and other chronic health conditions is also a great way to reduce the risk of long-term complications, such as carotid artery disease or stroke. Talk to your doctor about the best way to keep your heart and blood vessels healthy.