Carotid Artery Stenosis

Definition

Carotid Artery Stenosis is the narrowing of the passageway of the artery, usually from atherosclerosis (plaque in the lumen composed of coagulated fat).

Pathophysiology

Arterial walls can be damaged by different factors. Smoking introduces harmful chemicals that cause injury, and cholesterol buildup in blood makes it easy to stick to the walls. Damage to the wall and extra cholesterol aggregation create an uneven and rough surface that other material can further bind to. Eventually the accumulation of lipid and fibrous material forms the plaque. This narrows the vessel, and makes the wall thick and rigid as well.

Risks:

Older Age, male gender
Cigarette smoking
Hypertension, diabetes, hyperlipidemia
Family history of atherosclerosis

Symptoms & Signs

Symptoms of Stroke or TIA (Transient Ischemic Attack) are the most worrisome:

Drooping of one side of face/body
aLOC or loss of consciousness
Amaurosis fugax (transient loss of vision)
Inability to walk/speech

Best Imaging Modality

Stenosis Measurement

North American Symptomatic Carotid Endarterectomy Trial (NASCET):

Gold Standard: Cerebral Angiography

Pros: Can evaluate the ENTIRE carotid artery pathway. It can help evaluate: presence of atherosclerosis, shape of the plaque, collateral vasculature around the vessel.

Cons: Invasive, expensive, risk of morbidity due to neurologic complications.
Carotid Duplex Ultrasound

Uses ultrasound and Doppler U/S to detect local changes in blood flow - as you might imagine, fluid flows faster across a narrower pipe under the same pressure. Thus, in CDUS, peak systolic velocity is measured to determine the degree of stenosis.

Specificity: 100% for peak systolic velocity (PSV) >4.4m/s. Overall 82-89% specific for detecting stenosis in ICA.
Sensitivity: 96% for PSV >2m/s. 81-98% sensitive.
Pros: noninvasive, inexpensive
Cons: tends to overestimate the degree of stenosis. Less precise when evaluating < 50% stenosis.

Adjunct: Transcranial Doppler

Evaluates the big arteries in the brain through the skull base and the orbit. It is used with CDUS to look into how much the brain is being perfused in the context of the ICA stenosis.

ICA lumen at the origin < 1.5mm is generally determined as a significant stenosis
Transorbital: Reversed flow in ophthalmic artery, and 50% PSV difference between the distal ICAs on either side.
Transtemporal: >35% difference in PSV between MCA, and >50% difference between ACA are significant.

Other Modalities

Contrast-Enhanced U/S, 3D Ultrasound, Compound Ultrasound, Magnetic Resonance Angiography, Computed Tomography Angiography

Treatment

Stenosis >70% of the ICA benefits from revascularization procedure for stroke risk reduction, and it outweighs the risks. Ideally, the procedure must be performed within 2 weeks of first symptoms. Carotid revascularization options:

Carotid Endarterectomy

Carotid Artery Stenting

References

Furie KL. Evaluation of carotid artery stenosis. UpToDate.com. (accessed on August 2022)