Carotid artery stenosis: what causes narrowing of the carotid artery, what symptoms does it have?

Carotid artery stenosis: what causes narrowing of the carotid artery, what symptoms does it have?
Photo source: Getty images

Narrowing of the carotid artery is a serious condition that can lead to impaired blood supply to the brain and even stroke. Atherosclerosis is not the only cause.

Most common symptoms

Show more symptoms

Characteristics

Narrowing of the carotid artery, or simpy the carotid, is risky in terms of reducing and restricting blood supply to the brain. Impaired blood supply can lead to cerebral ischemia - a stroke.

Narrowing of the carotid artery = carotid (artery) stenosis.

A cerebrovascular accident, or CVA, (a stroke) is one of the most serious diseases and ranks among the leading causes of mortality along with heart disease and cancer.

Of the total number of strokes, approximately 85% are ischemic in origin. Haemorrhage accounts for the remaining 15%.

Brain tissue ischemia = decreased blood supply. 

Brain anaemia manifests as a deterioration of neurological function - neurological deficit. Through impaired vision, speech or mobility to short-term loss of consciousness - collapse and unconsciousness.

Notable data:
Ischaemic stroke accounts for 85% of cases.
The most common cause is atherosclerosis of the arteries. 
15-20% CVA due to narrowing of the carotid arteries.
90-95% of carotid stenoses are caused by atherosclerosis.

Briefly about the carotid artery and cerebral blood supply

The brain, as the centre of the nervous system, thinking and control, must be continuously supplied with blood. More precisely, with oxygen and the energy component, which consists of sugar.

Without oxygen and glucose, it is unable to perform its function.

Table: what the brain needs to run

What the brain needs Description
Sugar
  • glucose
    • approximately 115 grams of sugar per day
    • 100 grams of brain tissue requires 5.5 mg of glucose
    • which is approximately 75 grams per minute
Oxygen
  • 100 grams of brain tissue needs about 3.5 ml of oxygen
  • 50 ml O2 per minute for the brain
    • which represents 15-20% of the body's total requirement for the brain alone for one minute
Blood
  • 50-60 ml of blood per minute
  • approximately 750 ml of blood per minute flows through the brain at rest
  • blood flow increases by up to 50% during exercise
Blood circulation disorder
  • 2-8 seconds until brain tissue uses up the oxygen
  • 12 seconds without oxygen = unconsciousness
    • collapse to unconsciousness sets in
  • after 3-4 minutes = irreversible damage to brain tissue
  • after 9 minutes without O2 = no brain survival possible
    • Hypothermia may prolong brain survival time due to reduced energy demand and O2 requirement  

Blood is supplied to the brain by two main arteries, which are paired, that is, on both the right and left sides of the body. They are...

Let's look at the cervical and vertebral arteries.

Carotid artery - in the neck. 
Vertebral artery - in the vertebrae. 

The carotid and vertebral arteries branch further into smaller arteries and arterioles. Together, they form vascular circulation to provide a constant blood supply to the brain.

The circuit of the main cerebral arteries is referred to as the Circle of Willis. 

After nutrients and oxygen have been consumed, blood is then drained from the brain through a system of veins. This is to the paired internal jugular vein - vena jugularis interna.

The carotid artery

This paired artery that leads blood to the head and partly to the neck. It has a section that is located in the chest and the upper cranial part in the neck goes to the head. 

There are two carotid arteries: the right a. and the left a.

The carotid arteries are pulsatile and bilaterally well palpable on the side away from the trachea and thyroid cartilage.

The right one branches off from the truncus brachiocephalicus (brachiocephalic trunk), which exits from the aorta. It subsequently courses into the neck.

The left one branches off directly from the aorta, more precisely from the arch (arcus aortae), and goes up into the neck.

The main carotid artery is referred to as:
arteria carotis communis dextra = right common carotid artery, 
arteria carotis communis sinistra = left common carotid artery. 
They are abbreviated as ACC.

The common carotid artery runs down the neck to approximately the upper edge of the thyroid gland. At this point it divides into two branches. Up to this point it has no other branches.

The carotid artery is embedded in the carotid neurovascular bundle. This contains the blood vessels, both artery and vein, plus the vagus nerve and other nerves of the crura.

The common carotid has two branches:

  1. arteria carotis externa - external carotid artery, ACE
    • it is further divided into smaller arteries that supply part of the neck and head, organs and muscles, for example:
      • thyroid gland
      • larynx
      • neck muscles
      • partly the muscles of the neck
      • oral cavity
      • facial muscles
      • pharynx
      • and other areas, muscles and organs of the head outside the supply of the internal carotid artery
  2. arteria carotis interna - internal carotid artery, ACI
    • it supplies
      • orbit
      • eyeballs
      • eyelids
      • the back of the nose
      • middle ear cavity
      • part of the meninges
      • pituitary 
      • brain

That's not all.

In the carotid artery there are important pressure receptors - pressor receptors or baroreceptors, on the basis of which blood pressure is regulated. This is a cluster of nerve receptors.

The site is referred to as the carotid sinus - sinus caroticus. It is located near the branching of the common carotid artery into internal and external.

An increase in pressure at a given location will cause a drop in blood pressure, a decrease in heart rate and even cardiac arrest and, if it lasts more than 3 seconds, collapse and loss of consciousness.

Mechanical irritation can also be caused externally.

For example: Tightening the tie too much,  tight collar, when bending the head (washing hair in the hairdresser's sink),  a sharp turn of the head (rotation) or tilted back. 

Compression of the carotid arteries on both sides of the neck is therefore very dangerous. 

Want to know more about narrowing of the carotid arteries?
What causes it? 
How does it manifest? 
What is its course? 
Can it be treated? 
Read on. 

What is a narrowing of the carotid artery?

Carotid stenosis, or narrowing of the carotid artery, is an affection of a blood vessel that is responsible for reducing blood supply to the brain.

It is a condition of narrowing of the internal carotid artery - a. carotis interna.

The reduction of the arterial translucency and the unevenness of the vascular wall are the basis for the disruption of blood flow. Impaired blood flow leads to the formation of blood clots.

The blood clot again reduces the space for blood to flow to the brain. Also, it is a risk factor for embolism.

A blood clot, formed on the uneven surface of a blood vessel, breaks off and travels in the bloodstream. Subsequently, it clogs a smaller cerebral artery.

The blockage will cause insufficient blood supply to the brain tissue. This will cause brain dysfunction.

Embolism by a blood clot will cause an embolic ischemic stroke.
See also the article on Stroke.

Depending on the location and extent, neurological difficulties occur, which may manifest as visual impairment, blindness in one eye, impaired speech and mobility, and even impaired consciousness.

Brain anaemia can be temporary or permanent. If it is a permanent interruption of blood supply we call it a stroke.

Stroke = ischemic cerebrovascular accident (CVA).

The temporary form is one in which symptoms are present but resolve within a few hours. It is referred to as a transient ischaemic attack, abbreviated TIA.

Causes

The most common cause of carotid stenosis is atherosclerosis. However, other mechanisms and problems are also involved in the development of vascular narrowing.

Atherosclerosis is the commonest

Atherosclerosis is a slowly progressive long-term disease of the arteries. On the basis of hardening of the arteries, a shrinkage of the inner space of the vessel occurs.

The lumen of the artery, and therefore the space for blood flow, decreases over time.

This has the effect of reducing the amount of blood that is able to flow through the narrowing. Also, the obstruction in blood flow creates the conditions for clots to form.

The process of hardening of the arteries begins in early youth. However, for a long time it proceeds unnoticed. Most often, the onset of difficulties is manifested in middle age or old age.

Substances are deposited in the artery wall that are not normally there. These are mainly fatty and other components of the blood.

In short, this long-lasting development can be described as follows:

  1. impaired functionality of the endothelium - the inner lining of the blood vessel
  2. accumulation of lipids - fat
  3. lipid core formation
  4. fibrous cap formation
  5. association of an inflammatory process
  6. scar formation
  7. change in blood flow
  8. deposition of platelets

But that's not all.

Vasoconstriction + loss of blood vessel elasticity = impaired ability to regulate blood pressure.

In addition to mechanical constriction, the altered vessel wall is the cause of triggering the biochemical cascade and inflammation that is behind the formation of a blood clot on the vessel wall.

Normal state = blood flows in healthy blood vessels undisturbed, it does not clot or boil.

But...

Pathological = disease-related. A disrupted and narrowed vascular wall creates an obstruction in the flow of blood.

The blood circulates.

Changes in blood flow promote blood clot formation.

A blood clot - a thrombus, in turn, reduces the space in the vessel wall. Of course, this again negatively affects blood flow.

Mechanism of constriction + impaired flow + thrombus formation = vicious circle.

A thrombus partially or completely clogs a blood vessel.

The atherosclerotic plaque located in the vessel wall can rupture. This triggers an immediate reaction of deployment of platelets and other clotting components. 

A thrombus forms. At this point, the acute form occurs.

Both, whether long-term or suddenly formed, are also risky from the point of view of the break-off of the thrombus.

The blood clot is released from the vascular wall. It then travels through the blood. Now, it is already referred to as an embolus.

An embolus by blocking a smaller artery in the brain will cause an embolism. The unblooded part behind the blockage - the occlusion, or closure of the artery, is not blooded, causing its ischemia, infarction, or in other words, stroke. 

An ischaemic stroke develops = also known as a cerebral infarction.

The process of atherosclerosis occurs anywhere in the human body. And in several places at the same time. Most of the time, not just one blood vessel is affected. 

Research has demonstrated the fact that:
At least two or three blood vessels are affected at the same time.
Arteries of the heart and arteries of the lower extremities.
In a smaller proportion, the vessels of the brain and lower extremities,
or arteries of all three systems.
This is especially true for people over the age of 62.

Depending on which part it interferes with, it will also prove to be an example:

Table: the most common causes of narrowing of the artery 

Name Description
Atherosclerosis
  • the most common cause
  • prevalence of carotid stenosis:
    • in 50-year-olds: 0.5%
    • in 80-year-olds: above 0.5%
  • the most common site of atherosclerotic changes is
    • in the bifurcation of the a. carotis communis - part of the branching to the internal and external carotid arteries
      • bifurcation = a split or branching off into two parts
    • plus in the section of the posterior wall of the ACI - internal carotid artery
Dissection
  • rupture of the vessel wall longitudinally and bleeding between the layers of the vessel
  • spontaneous - predisposition to weakening of the vascular wall
  • injury-related
Aneurysm of the carotid artery
  • vascular wall aneurysm
  • reduces the internal lumen of the artery
Injury
  • damage to a blood vessel in blunt trauma
  • formation of dissection
  • traffic accidents
    • rapid deceleration - deceleration to a stop
    • hyperextension with rotation in the neck
    • so-called whiplash injuries
  • fall from a height
  • but also seemingly simple injuries
    • quick head turn and neck rotation
    • for coughing, sneezing, sports and exercise
Inflammation of blood vessels
  • carotid vasculitis
    • inflammatory
    • autoimmune
Fibromuscular dysplasia
  • a non-inflammatory disease of the vascular lining that causes narrowing or closure of a blood vessel
Cystic degeneration of the intima
  • changes in the vascular wall

In the development of the disease, some risk factors are mentioned. And since it is preferably an atherosclerotic stimulus, they are common to both problems.

Risk factors for atherosclerosis and carotid artery stenosis: 

Symptoms

Symptoms of carotid artery narrowing develop depending on the location and extent of the brain involvement. The most serious condition is anemia of the brain. And it can take place in several forms.

The are several possibilities...

For example, the short episode. During its duration, manifestations of anemia are added, namely, impaired neurological functions.

The duration is in minutes up to an hour or two. Within 24 hours, the discomfort completely subsides.

Such a temporary period is referred to as:

TIA - Transient Ischemic Attack.

Alternatively, these are multiple episodes of short duration with neurological deficit over hours to days

This type of TIA is referred to in professional circles as:
Crescendo TIA = 2 or more episodes within hours to a week. 

Remember:

After overcoming transient anaemia, the risk of developing a stroke increases.

Another important concept is: 

Stroke in evolution. This indicates the progression of neurological deficit over 24 hours
And
Focal brain ischemia = complete cerebral infarction and persistence of neurological discomfort for 5 days.

Focal brain ischemia = focal cerebral ischemia - local deficiency of blood and metabolic substrates due to insufficient arterial zásobenie.

The assessment of neurological deficit and its classification is important.

Classification of stages:

  • 1st stage - asymptomatic stenosis - without symptoms
  • 2nd stage - transient state of anaemia = Focal brain ischemia
  • 3rd stage - focal brain ischemia in acute phase, i.e. stroke in evolution
  • 4th stage - total focal brain ischemia with persistent neurological deficit

Table: main symptoms of neurological deficit

Symptoms Description
Loss of limb control
  • impaired limb mobility occurs on the opposite side to the affected brain
  • contralateral disability
  • partial paralysis of one half of the body = hemiparesis
  • complete paralysis of one half of the body = hemiplegia
  • associated skin sensitivity disorder
    • paresthesias - tingling in the limb
    • numbness, anaesthesia
Mobility impairment
  • the person is unable to coordinate walking and movements
  • partially to completely immobile
  • pulls one limb behind the other
  • the person is pulled to one side
Speech impairment
  • problem with pronunciation of words
  • incomprehensible speech
  • dysarthria - a speech disorder with faulty articulation
Visual impairment
  • visual issues may manifest as:
    • blurred vision, double vision
    • blindness
    • on one eye
    • on the side of theblood circulation disorder
  • Amaurosis fugax - temporary loss of vision in one or two eyes
Paresis of the facial muscles
  • facial nerve paresis, drooping of one side of the face
  • drooping of the corner of the mouth
    • curved mouth
    • drooping of the face
  • drooping of the eye and finding wrinkles on one side

Other symptoms occurring in cerebrovascular accident.

The development of difficulties is acute i.e. sudden.
Early recognition of a stroke,
diagnosis
and
early treatment are important. 
Otherwise, there is a risk of irreversible brain damage. 

Noteworthy: 
The occurrence of collapses due to a specific position of the head.
Lying down while watching TV, in the hairdresser's chair while washing your head, in the dentist's chair.
There is a strangulation of the vessel's lumen and partial to complete restriction of blood flow through the carotid artery.
The condition is also referred to as kinking.

Diagnostics

Early recognition of stroke is crucial for diagnosis and early treatment management. Its role is to shorten the time course of cerebral ischemia. 

The shorter the duration of the lack of blood supply, the smaller the neurological deficit will be.

Of course, the prognosis depends on several characteristics.

Detection of carotid artery narrowing is important in preventing the development of stroke.

From a practical point of view, it is divided into asymptomatic and symptomatic ACI (arteria carotis interna).

The asymptomatic form is usually detected accidentally during another examination. Since it is not yet manifested, the doctor does not diagnose the narrowing of the ACI purposefully.

Conversely...

The symptomatic form.

Differential diagnosis is made when symptoms develop that lead to a diagnosis of stroke. The task is thus to pinpoint the source of the symptoms.

Of course, the important thing is the medical history taken from the affected person. If this cannot be ascertained then from a relative or witness to the event.

This is followed by a physical examination, which mainly includes measurement of blood pressure and pulse rate, heart rate regularity, and subjective and objective assessment of respiration.

A general neurological examination will be performed as well.

The auscultatory examination of the carotid arteries and the presence of a murmur over the carotid arteries are also important. The latter will reveal problematic blood flow around the obstruction.

These basic examination methods are followed by imaging methods.

Their task is to detect possible AS (atherosclerotic) changes of the ACI or ACC unilaterally or bilaterally - bilaterally. Plus the state of cerebral blood supply and cardiac function.

Medical imaging techniques:

  • the complete basis and first choice in suspected stroke is CT and angio CT - angiography
  • next, an MRI - magnetic resonance imaging may follow
  • ultrasonography of the carotid arteries is performed to detect narrowing of the carotid artery
    • also called a SONO of the neck vessels
    • the gold standard in the diagnosis of ACC and ACI stenosis
    • duplex ultrasound, Doppler
  • DSA - digital subtraction angiography
  • also, ECHO - echocardiography
  • ECG

The degree of ACI stenosis also plays a role in the decision-making process for the subsequent management and treatment of the patient:

  • mild stenosis up to 50%
  • moderate stenosis 50 - 69 %
  • severe stenosis 70 - 95%
  • preocclusive stenosis 96-99 %
  • ACI occlusion 100% - complete blockage of the ACI

Read about other vascular diseases:
Diseases of the cerebral vessels
Diseases of the aorta
Peripheral arterial disease 
Chronic venous disease
Chronic venous insufficiency
Deep vein thrombosis
Thrombophlebitis

Course

The course of carotid artery stenosis is a long-term and progressive process. That is, it progresses and worsens over time.

Long-lasting or persistent = chronic.

Hardening of the arteries occurs at a young age. At this time, it is not yet manifested.

In this period, it is referred to as asymptomatic ACI stenosis.

However, when the narrowing of a blood vessel reaches a certain state, difficulties associated with insufficient blood supply to the area of the body, organ or tissue, and muscle occur. In this case, the brain.

At this point, it is already a symptomatic ACI stenosis.

In the event that the atherosclerotic plaque is damaged, platelets are seeded onto the damaged vessel wall. These also narrow the space in the blood vessel for blood flow.

Or they clog the blood vessel completely = occlusion of the blood vessel.

A possible condition that can develop from a formed blood clot is the aforementioned embolism. It arises as a complication of thrombosis , when the clot breaks away from the vessel wall.

The embolus becomes trapped in a blood vessel with a narrower translucency. And beyond the area of blockage, ischemia occurs.

Poor blood supply to a part of the brain may be temporary. In such a case, the discomfort will subside within hours. Multiple episodes in a row may recur.

The condition may also persists. Without timely treatment, permanent damage to the ischemic part of the brain occurs. 

Both forms are characterized by a rapid onset of symptoms.

How it is treated: Carotid artery stenosis

Treatment of carotid stenosis: Medications, lifestyle and surgery

Show more
fshare on Facebook

Interesting resources

  • Sila CA, Higashida RT, Clagett GP (April 2008). "Clinical decisions. Management of carotid stenosis". N. Engl. J. Med358 (15): 1617–21. doi:10.1056/NEJMclde0800741. PMID 18403770.
  • Drug Therapy Gains Favor to Avert Stroke, By THOMAS M. BURTON, Wall Street Journal, MARCH 3, 2009. Layman's summary of surgery vs. medication-only debate.
  • Jahromi, AS; Cinà, CS; Liu, Y; Clase, CM (June 2005). "Sensitivity and specificity of color duplex ultrasound measurement in the estimation of internal carotid artery stenosis: a systematic review and meta-analysis". Journal of Vascular Surgery41 (6): 962–72. doi:10.1016/j.jvs.2005.02.044. PMID 15944595.
  • Saxena, A; Yin Kwee, E; Lim, S (2019). "Imaging modalities to diagnose carotid artery stenosis: progress and prospect". BioMedical Engineering OnLine18 (1): 66. doi:10.1186/s12938-019-0685-7. PMC 6537161. PMID 31138235. Retrieved 2 July 2021.
  • Bartlett ES, Walters TD, Symons SP, Fox AJ (January 2006). "Quantification of carotid stenosis on CT angiography". AJNR. American Journal of Neuroradiology27 (1): 13–19. PMC 7976065. PMID 16418349.
  • White JH, Bartlett ES, Bharatha A, Aviv RI, Fox AJ, Thompson AL, Bitar R, Symons SP (July 2010). "Reproducibility of semi-automated measurement of carotid stenosis on CTA". The Canadian Journal of Neurological Sciences37 (4): 498–503. doi:10.1017/s0317167100010532. PMID 20724259.
  • Lian K, White JH, Bartlett ES, Bharatha A, Aviv RI, Fox AJ, Symons SP (May 2012). "NASCET percent stenosis semi-automated versus manual measurement on CTA". The Canadian Journal of Neurological Sciences39 (3): 343–6. doi:10.1017/s0317167100013482. PMID 22547515.
  • Solomon, Caren G.; Grotta, James C. (19 September 2013). "Carotid Stenosis". New England Journal of Medicine369 (12): 1143–1150. doi:10.1056/NEJMcp1214999. PMID 24047063.
  • US Preventive Services Task, Force.; Krist, AH; Davidson, KW; Mangione, CM; Barry, MJ; Cabana, M; Caughey, AB; Donahue, K; Doubeni, CA; Epling JW, Jr; Kubik, M; Ogedegbe, G; Pbert, L; Silverstein, M; Simon, MA; Tseng, CW; Wong, JB (2 February 2021). "Screening for Asymptomatic Carotid Artery Stenosis: US Preventive Services Task Force Recommendation Statement". JAMA325 (5): 476–481. doi:10.1001/jama.2020.26988. ISSN 0098-7484. PMID 33528542.
  • Brott, Thomas G.; Halperin, Jonathan L.; Abbara, Suhny; Bacharach, J. Michael; Barr, John D.; Bush, Ruth L.; Cates, Christopher U.; Creager, Mark A.; Fowler, Susan B.; Friday, Gary; Hertzberg, Vicki S. (2011-07-26). "2011 ASA/ACCF/AHA/AANN/AANS/ACR/ASNR/CNS/SAIP/SCAI/SIR/SNIS/SVM/SVS Guideline on the Management of Patients With Extracranial Carotid and Vertebral Artery Disease: Executive Summary: A Report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines, and the American Stroke Association, American Association of Neuroscience Nurses, American Association of Neurological Surgeons, American College of Radiology, American Society of Neuroradiology, Congress of Neurological Surgeons, Society of Atherosclerosis Imaging and Prevention, Society for Cardiovascular Angiography and Interventions, Society of Interventional Radiology, Society of NeuroInterventional Surgery, Society for Vascular Medicine, and Society for Vascular Surgery". Circulation124 (4): 489–532. doi:10.1161/CIR.0b013e31820d8d78. ISSN 0009-7322. PMID 21282505.
  • Ricotta, John J.; AbuRahma, Ali; Ascher, Enrico; Eskandari, Mark; Faries, Peter; Lal, Brajesh K. (September 2011). "Updated Society for Vascular Surgery guidelines for management of extracranial carotid disease: Executive summary". Journal of Vascular Surgery54 (3): 832–836.