Anatomy, Head and Neck, Carotid Arteries


Article Author:
Danielle Sethi
Ekramul Gofur


Article Editor:
Abdul Waheed


Editors In Chief:
Casey Ciresi


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Trevor Nezwek
Radia Jamil
Patrick Le
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Hassam Zulfiqar
Hussain Sajjad
Steve Bhimji
Muhammad Hashmi
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Sarosh Vaqar
Mark Pellegrini
James Hughes
Beata Beatty
Beenish Sohail
Nazia Sadiq
Hajira Basit
Phillip Hynes


Updated:
7/22/2019 8:59:47 AM

Introduction

The head and neck region obtain the majority of its blood supply via the carotid and also vertebral arteries. This activity primarily focuses on the in-depth orientation of the carotid arteries, including their anatomical course, branches and also the area of distribution. The carotid arteries are the primary vessels supplying blood to the brain and face.[1][2] The right common carotid artery (RCCA) originates in the neck from the brachiocephalic artery while the left common carotid artery (LCCA) arises in the thorax from the arch of the aorta.[3] Furthermore, both right and left common carotid arteries bifurcate in the neck at the level of the carotid sinus into the internal carotid artery (ICA), which supplies the brain, and the external carotid artery (ECA), which supplies the neck and face.[3]

Structure and Function

Like most of the vascular system throughout the body, histologically, the carotid arteries are made up of three layers – the inner layer "tunica intima," the middle layer "tunica media," and the outer layer "tunica adventitia." The tunica intima consists of endothelium supported by a fragile elastic and also a collagenous layer of variable thickness. Smooth muscle comprises the tunica media, and it is responsible for changing the diameter of the blood vessel to regulate blood flow and blood pressure. The tunica adventitia attaches the carotid vessel to the surrounding tissue. The carotid arteries originate posterior to the sternoclavicular joints and in the neck, they are contained within the carotid sheath posterior to the sternocleidomastoid muscle. At the location of the upper border of the thyroid cartilage (typically at the level of the fourth or fifth cervical vertebra), the common carotid arteries bifurcate into the ECA and ICA. This bifurcation point is clinically significant as it serves as a point for the location of the "carotid body," a chemoreceptor, and the "carotid sinus," a baroreceptor. The carotid body chemoreceptor is sensitive to decreased PO2, increased PCO2, and decreased pH of blood, and is responsible for alerting the brain to change the respiratory rate. The carotid sinus baroreceptors respond to changes in the stretch of the blood vessel and are responsible for detecting changes and maintaining blood pressure. After its division, the ECA exits the sheath to provide oxygenated blood to the face and neck, while the ICA continues in the carotid sheath to enter the carotid canal within the temporal bone.

The ECA has eight branches, which anastomose with the branches from the contralateral external carotid, allowing for collateral circulation: These branches include

  • Superior thyroid artery
  • Ascending pharyngeal artery
  • Lingual artery
  • Facial artery
  • Occipital artery
  • Posterior auricular artery
  • Maxillary artery
  • Superficial temporal artery

On the other hand, the ICAs anastomose with the branches of the basilar artery to form the circle of Willis. At the circle of Willis, the ICA branches to become the middle cerebral artery (MCA) and anterior cerebral artery (ACA). The MCA is responsible for supplying the motor and sensory cortices of the upper limb and face, as well as the Wernicke area of the temporal lobe and Broca’s area of the frontal lobe. The ACA is responsible for supplying the motor and sensory cortices of the lower limb. The ophthalmic artery is responsible for blood supply to the inner layers of the retina, as well as supplying other parts of the orbit, meninges, face, and upper nose.

Moreover, the course of the ICA is divided into four sections, depending on where the artery is currently traveling. These sections include the cervical, petrous, cavernous, and cerebral parts of the ICA. The ophthalmic artery branches off the cavernous portion of the ICA while the MCA and ACA are branches of the cerebral ICA.[4][5][6][7]

Furthermore, the neurologists, neuroradiologists, and neurosurgeons also use the Bouthillier classification to split the ICA into different parts based on the angiographic appearance of the vessel. According to this classification, the ICA slits into seven parts named as C1 to C7, with each part providing branching into different vessels. These branches of the ICA are generally tiny and inconsistent, and often they might not be present. However, the ophthalmic artery is present pretty much all of the time.[8] The description of this classification is below 

  • C1: Cervical
  • C2: Petrous
    • Caratiotympanic artery
    • Vidian artery
  • C3: Lacerum
  • C4: Cavernous
    • Meningohypophyseal trunk
    • Inferolateral trunk
  • C5: Clinoid
  • C6: Ophthalmic
    • Ophthalmic artery
    • Superior hypophyseal trunk
  • C7: Communicating
    • Posterior communicating artery
    • Anterior choroidal artery
    • Anterior cerebral artery (ACA)
    • Middle cerebral artery (MCA)

Embryology

The embryological devolvement of the carotid vascular system is very interesting. AS the pharyngeal arches begin to form during weeks 4 to 5 of gestation, the common carotid arteries (CCAs) and proximal ICAs derive from the third pharyngeal arch. While the distal ICA derives from the dorsal aorta. Interestingly, the ECA derives from the CCA via angiogenesis.[9]

Nerves

The glossopharyngeal nerve (CN IX) is responsible for transmitting baroreceptor afferent input from the carotid sinus to the solitary nucleus of the medulla. Also, the vagus nerve (CN X) runs posterolaterally to the ICA/CCA and posteromedially to the internal jugular vein within the carotid sheath.

Muscles

Understanding the vascular supply of the carotid arteries is crucial clinically. The muscles of mastication receive vascular supply from the maxillary artery and facial artery, branches of the ECA. The facial artery also supplies muscles of facial expression. The occipital artery, another branch of the ECA, supplies blood to the sternocleidomastoid, trapezius, and deep muscles of the back. The superficial temporal artery supplies the temporal muscle. The extraocular muscles get their vascular supply by branches of the ophthalmic artery, which is a branch of the ICA.[10]

Physiologic Variants

The common carotid artery typically bifurcates at the upper border of the thyroid cartilage, but several studies have shown a variant in which the common carotid artery bifurcates more distally. This bifurcation is significant as the carotid bifurcation is the site of clinically meaningful atherosclerosis and a more distal bifurcation may impact the ability to proceed with standard surgical approaches.[11] 

Rare case reports have presented variants of ICA and ECA agenesis, aplasia, and hypoplasia, and these have been found to be both unilateral or bilateral. The COW usually supplies collateral circulation.[12] Another example of an aberrant ICA is a retropharyngeal ICA which is generally asymptomatic but is essential to recognize in the face of non-typical symptoms. Some symptoms could include submucosal pulsating mass in the posterior pharynx even hoarseness and respiratory issues depending on how medially located the ICA is.[13]

Surgical Considerations

The carotid arteries are vital for providing oxygenated blood to the brain. Just like all arteries, they are susceptible to atherosclerosis, which can lead to stenosis and distal embolism of plaque. Additionally, during aortic arch surgeries, perfusion to the brain must be maintained. Lastly, injury to the carotid arteries must be ruled out in penetrating neck traumas.

  • Carotid Artery Stenosis:  Atherosclerosis of the carotid arteries most often occurs at the bifurcation of the CCA to the ICA and ECA. This condition is one of the major causes of transient ischemic attack and stroke. The condition is usually manageable with optimized medical therapy, but there are two surgical treatment modalities for patients who are asymptomatic with high-grade stenosis (70 to 90%) or patients who are symptomatic with moderate (50 to 69%) or high-grade stenosis. Surgical options include an endovascular approach (angioplasty and stenting) and an open approach (endarterectomy). Several trials are underway to compare the efficacy of these two modalities, as well as comparing them to optimized medical therapy. There are risks and benefits with both approaches, so deciding which approach to use depends on the patient’s level of stenosis and other comorbidities.[14][15]
  • Aortic surgery: During aortic arch repair, cerebral protection is necessary. There are several approaches, including hypothermic circulatory arrest, retrograde cerebral perfusion, and antegrade selective cerebral perfusion via the carotid arteries. One study uses existing evidence to propose hypothermic circulatory arrest and antegrade selective cerebral perfusion as the preferred approaches for neuroprotection during aortic arch repair; a retrospective review later supported this approach.[16][17]
  • Penetrating neck trauma: If a patient with penetrating neck trauma becomes unstable or presents with hard signs, such a condition warrants surgical exploration. Hard signs that would be concerning in regards to the carotid artery include diminished carotid pulse, expanding hematoma, and active arterial bleeding. Injury to the carotid occurs in 4.9 to 6% of penetrating neck traumas. Attempts should always be made to repair the artery due to better rates of survival and lower risk of permanent neurologic deficits. Repair options include primary repair, anastomosis, vein grafting, PTFE patch, and transposition of ECA to injured ICA. Ligation of the artery is necessary when a repair is not possible but has higher rates of mortality and morbidity, such as stroke.[4][18]

Clinical Significance

The common carotid artery can be used to measure the pulse. In the setting of hypovolemic shock, if only the carotid pulse is palpable, this correlates to a systolic blood pressure of 60 to 70 mmHg. As the carotid arteries are responsible for supplying oxygenated blood to the brain, many conditions require monitoring and treatment, especially if the patient is symptomatic, including atherosclerosis leading to stenosis, carotid artery aneurysm, transient ischemic attack, and stroke.


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Anatomy, Head and Neck, Carotid Arteries - Questions

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A 55-year-old male patient presents to the emergency department with the onset of left-sided upper and lower extremity weakness along with slurred speech. The origin of the artery leading to this patient's symptoms is found to have an 80% stenosis. 1 week after stabilization of the patient the medical team offers the patient a surgical treatment which would decrease the degree of stenosis in the origin of the artery leading to his symptoms. What major landmark will the surgeon use to determine the location of the artery in question?

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A 47-year-old male complaining of difficulty seeing out of his left eye is brought to the emergency department. In the ED, the patient is noted to have 2/5 strength and sensation on the right upper and lower extremities. The patient is additionally noted to have a left-sided drooping of the eyelid, and left-sided pupil diameter of 1mm. After some time, the vision to his left eye has returned. Damage to which of the following structures has potentially led to the patient's symptoms?



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A 78-year-old female presents with facial drooping, slurred speech, and 3/5 weakness in both upper and lower extremity on the right. She has a past medical history of peripheral vascular disease, coronary artery disease, and hypercholesteremia. She is currently on low dose aspirin and also on high dose rosuvastatin. The physical examination reveals a bruit in her neck. The artery responsible for her symptoms bifurcates at the level of which of the following structures?



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A 50-year-old female with a past medical history of long-standing hypertension, coronary artery disease, and hypercholesteremia presents with new symptoms of transient visual loss lasting 20 minutes on average. She is currently on propanolol, aspirin, and high dose atorvastatin. According to Bouthillier's classification, which part of the ICA gives rise to the artery leading to this problem?



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A 77-year-old male with a past medical history of myocardial infarction and peripheral artery disease presents for the annual visit. He reports no new concerns or symptoms. On physical examination, a bruit is heard in his neck. The artery responsible for the bruit bifurcates typically at the level of which of the following vertebral levels?



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A 72-year-old male presents to the ED with weakness of the right upper and lower extremities along with left facial drooping and slurring of the speech. The artery leading to this patient's symptoms is found to be 80% stenosed. What is the posterior border of the triangle in the neck that contains the bifurcation of origin of the artery causing this patient's symptoms?

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A 34-year-old male falls off the ladder while cleaning the roof to his house and lands on the left side of his head. He initially loses consciousness. His daughter finds him and can arouse him. She takes him to the emergency department where the patient complains of headache and left-sided chest pain. The medical team order a non-contrast CT of the head showing a hyperdense, lens-shaped lesion which does not cross suture lines on the left side of the skull. Blocking which of the following artery can minimize the symptoms in this patient?



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A 66-year-old female comes to a physician's office complaining of new-onset vision changes. She reports a loss of vision, which she describes as a curtain coming down over her field of vision. However, after 5 minutes the patient is able to see. The involved vessel is a branch of which of the following arteries?

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A 26-year-old medical student during his studies recognizes that when he stands up from sitting his heart rate increases slightly for a few seconds and then normalizes. Which anatomical landmark in the neck will allow the identification of the structure leading to this physiological response in the medical student?

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A surgical intern is asked to assist the vascular surgeon with a procedure in the neck. The surgeon shows the intern an angiogram seen below. Before the procedure, the surgeon mentions that the large artery seen here travels in a structure along with a vein and nerve. Which of the following is a potential deficit if this nerve is damaged?

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A 26-year-old male patient with no significant past medical history was brought to the emergency departments with the complaints that he suffered severe blunt trauma to the chest following after a motor vehicle accident. From the angiogram, it appears that the artery that bifurcates at the level of C4 is leaking. This artery bifurcates into artery "A" and artery "B." Artery "A" travels with the internal jugular vein and vagus nerve while artery "B" does not. Which of the following potential deficit could occur if a branch of artery "B" is damaged?



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A 74-year-old male with a past medical history of hyperlipidemia, hypertension, and 40 pack year smoking history, comes to the office with a complaint of transient vision loss in his right eye. He describes the vision loss as a dark curtain coming down on his visual field. The episodes usually last 10-20 minutes. Which of the following is the most likely source of his symptoms?



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A 24-year-old male presents to the emergency room with a chief complaint of heart palpitations and lightheadedness. EKG shows supraventricular tachycardia and carotid massage is attempted to abort the episode. Which of the following relays this information to the brain?



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Anatomy, Head and Neck, Carotid Arteries - References

References

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