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Carotid stenosis

Stenosis in the internal carotid artery, either intracranial or extracranial, leading to symptoms of amaurosis fugax, transient ischemic attacks, or ischemic stroke ipsilateral to the lesion.

Introduction

Stenosis in the internal carotid artery, either intracranial or extracranial, leading to symptoms of amaurosis fugax, transient ischemic attacks, or ischemic stroke ipsilateral to the lesion.

  • 80 to 85% strokes are ischemic due to carotid artery stenosis (CAS).

Aetiology

peripheral arterial disease.

Risk factors for atherosclerosis:

CAS is due to atherosclerosis. As the atherosclerosis progresses the atherosclerotic plaques rupture resulting in the formation of thrombus and arterial occlusion or dislodged materials from the plaques blocking the smaller branches of the carotid artery.
  • Dyslipidemia
  • Hypertension
  • Diabetes
  • Obesity
  • Cigarette smoking
  • Advanced glycation end products (AGEs) and its receptors (RAGE, soluble RAGE [sRAGE])
  • Lack of exercise
  • C-reactive protein (CRP)

Pathophysiology

Carotid artery atherosclerosis is mostly present at the carotid bifurcation into external and internal carotid artery. The ostium of the internal carotid artery is mostly affected. Intracranial internal carotid artery and its branches are less affected with atherosclerosis.

Dr. Singh. (2020) Carotid Stenosis | Altair Health. Retrieved November 13, 2020, from https://altairhealth.com/altair-health-neurovascular-center/carotid-stenosis/

Extracranial symptomatic carotid stenosis:

Typically seen at the carotid bifurcation extending to the intracranial internal carotid artery in a portion referred to as the cervical segment.
  • Revascularization techniques for extracranial carotid atherosclerosis include carotid endarterectomy (CEA) or carotid angioplasty and stenting (CAS). Revascularization is discussed in more details below.

Intracranial symptomatic carotid stenosis:

The intracranial carotid artery begins at the petrous segment and continues in the direction of blood flow to the lacerum, cavernous, clinoid, ophthalmic, and communicating segments where it ends at the carotid terminus.
  • Intensive medical management has been demonstrated to be superior to revascularization in patients with severe (70–99%) intracranial stenosis.

Clinical features

Asymptomatic presentation:

CAS is considered symptomatic when ipsilateral retinal or cerebral ischemia occurs and asymptomatic when these symptoms are absent.

Amaurosis fugax:

Ipsilateral transient visual obscuration from retinal ischemia

Transient ischemic attacks (TIA) → Ischemic stroke:

Approximately 30% of strokes are caused by carotid occlusive disease.
  • Contralateral weakness/numbness of an arm, a leg, or the face, or of a combination of these sites
  • Visual field defect
  • Dysarthria
  • Aphasia (in case of dominant (usually left) hemisphere involvement)
The Risk of a First Ipsilateral Stroke at Five Years after Study Entry in the Territories of Carotid Arteries with and without Symptoms, According to the Degree of Stenosis. | Inzitari, D., Eliasziw, M., Gates, P., Sharpe, B. L., Chan, R. K. T., Meldrum, H. E., & Barnett, H. J. M. (2000). The Causes and Risk of Stroke in Patients with Asymptomatic Internal-Carotid-Artery Stenosis. New England Journal of Medicine, 342(23), 1693–1701. https://doi.org/10.1056/NEJM200006083422302
  • Carotid artery disease is responsible for nearly 50% of all TIAs
  • Risk of developing stroke after TIAs is as high as 20% within the 1st month. If untreated, TIAs result in development of stroke within 2 years. Risk of stroke events remains high for 10 to 15 years after TIAs.

Classic symptoms of TIA contrasted with vertebrobasilar symptoms:

It is important to distinguish between these two types of symptoms because patients with transient ischemia of the vertebrobasilar system do not benefit from CEA.
Carotid symptoms compared with vertebrobasilar symptoms | Louridas, G., & Junaid, A. (2005). Management of carotid artery stenosis. Update for family physicians. Canadian family physician Medecin de famille canadien, 51(7), 984–989.

Diagnosis

Carotid auscultation:

  • Carotid bruit: Turbulent flow in carotid artery
    • Associated with increased risk of vascular disease, including stroke, myocardial infarction, and cardiovascular death

Doppler ultrasonography:

First diagnostic imaging tool used to screen for carotid artery stenosis

Catheter angiography:

Criterion standard for defining the degree of stenosis and the morphologic features of the offending plaque. However, catheter angiography is neither feasible nor recommended in every patient because of its risks and costs.
Angiogram of a section of the cervical internal carotid artery A) with 99% stenosis 5 years after radiation therapy, and B) after the successful deployment of a 10-mm-diameter by 4-cm-length self-expanding nitinol stent. | Strickman, N. E., & Loyalka, P. (2005). Carotid artery stenosis: an endovascular specialist’s perspective. Texas Heart Institute journal, 32(3), 318–322.

CT-angiography and MR-angiography (MRA):

Confirmatory test after Doppler study suggestive of hemodynamically significant stenosis in an asymptomatic patient
Features of complex plaque on magnetic resonance imaging: ( A) Two-dimensional (2D) time-of-flight magnetic resonance angiography image shows roughly 50% stenosis of the carotid bulb resulting from a complex plaque. ( B) Contrast-enhanced long-axis T1-weighted (T1W) 2D double inversion recovery (DIR) image, obtained at a resolution of 0.35 × 0.35 × 2 mm. (C) Axial contrast-enhanced fat-suppressed T1W DIR image obtained with a resolution of 0.35 × 0.35 × 2 mm through the plaque reveals an enhancing fibrous cap (FC), a low-intensity non-enhancing lipid-rich necrotic core (LRNC), and a dark area of calcification. | Images courtesy of Bruce Wasserman, Johns Hopkins University.

ABCD2 scoring:

Criteria and Points of the ABCD2 Scoring Systema | Lanzino, G., Rabinstein, A. A., & Brown, R. D., Jr (2009). Treatment of carotid artery stenosis: medical therapy, surgery, or stenting?. Mayo Clinic proceedings, 84(4), 362–368. https://doi.org/10.1016/S0025-6196(11)60546-6

Management

Invasive treatment is considered for symptomatic patients with stenosis greater than 50%6 and for asymptomatic patients with stenosis greater than 60%.

Management of carotid artery stenosis: High-risk patients present with symptoms of motor weakness, speech deficit, hemispatial deficit, and hemianopia; low-risk patients present with only sensory deficit or amaurosis fugax. | Louridas, G., & Junaid, A. (2005). Management of carotid artery stenosis. Update for family physicians. Canadian family physician Medecin de famille canadien, 51(7), 984–989.

Lifestyle changes:

Slow the progression of CAS
  1. Cessation of smoking and use of tobacco products
  2. Diet low in saturated fats, cholesterol, and sodium
  3. Control of body weight
  4. Daily physical exercise
  5. Reduction of dietary calories intake
  6. Limitation of alcohol use

Pharmacological management:

Recommended in asymptomatic patients with low-grade CAS (<50%)
  • Lipid lowering agents: Statins
  • Antihypertensive agents:
    • Stage I HTN: Thiazide diuretics, angiotensin converting enzyme inhibitor (ACE-I), β blockers (BBs), angiotensin receptor blockers (ARBs), calcium channel blockers (CCBs) or combination.
    • Stage II HTN: Thiazide diuretics + ACE-I/ARBs/BBs/CCBs.
  • Anti-AGEs therapy: Aminoguanidine, pyrido-xanthine (natural vitamin 6), benfotiamine (a lipid-soluble derivative of thiamine), aspirin, metformin, candesartan, and orlistat, α-carbonyl compounds (alagebrium)
  • Agents that increase levels of sRAGE: Antidiabetic agents (Insulin and rosiglitazone), Vitamin D, Statins, ACE-I (ramipril)
  • CRP-lowering agents: Celecoxib, clopidogrel. Statins, rosiglitazone, carvedilol, antioxidants (α-tocopherol, vitamin C), ramipril, quinapril, valsartan, candesartan, calcium channel blockers (amlodipine), and combination of hydrochlorothiazide and amlodipine.
  • Antiplatelet therapy: Aspirin, clopidogrel, or ticlopidine

Carotid endarterectomy (CEA):

Recommended in asymptomatic patients with CAS of 50-60%.
Carotid endarterectomy is surgery to remove atheroma (plaque build up) that causes narrowing (stenosis) in the artery to lower the risk for future TIA (transient ischemic attack) and stroke. | Dr Holland In. (2020) So you have carotid stenosis, should you have surgery? | Neurology Update. Retrieved November 13, 2020, from https://mmcneuro.wordpress.com/2012/12/21/so-you-have-carotid-stenosis-should-you-have-surgery/

Carotid angioplasty and stenting (CAS):

Carotid angioplasty and stenting. A, Large catheter (guide catheter, not shown) is placed in the common carotid artery proximal to the stenosis. Through this catheter, a filter wire is used to cross the stenosis and deploy a filter (distal protection) in the internal carotid artery distal to the plaque. The filter captures emboli dislodged during the procedure. B, Angioplasty (predilatation) of the plaque is performed with an angioplasty balloon, followed by stent deployment (C). Occasionally, angioplasty may be necessary after stenting to further dilate residual stenosis. D, The filter is “captured” and withdrawn into the guide catheter. The procedure is done with full heparinization. Patients receive maintenance dual antiplatelet therapy, usually aspirin plus clopidogrel, for at least 4 to 6 weeks. | Lanzino, G., Rabinstein, A. A., & Brown, R. D., Jr (2009). Treatment of carotid artery stenosis: medical therapy, surgery, or stenting?. Mayo Clinic proceedings, 84(4), 362–368. https://doi.org/10.1016/S0025-6196(11)60546-6
Freedom from major adverse events at 1 year. In the intention-to-treat analysis (A), the rate of event-free survival at 1 year was 87.9% among patients randomly assigned to carotid stenting, as compared with 79.9% among those randomly assigned to endarterectomy (P = 0.053). In the actual-treatment analysis (B), the rate of event-free survival at 1 year was 88.0% among patients who received a stent, as compared with 79.9% among those who underwent endarterectomy (P = 0.048). I bars represent 1.5 times the SE. | Yadav JS, Wholey MH, Kuntz RE, Fayad P, Katzen BT, Mishkel GJ, et al. Protected carotid-artery stenting versus endarterectomy in high-risk patients. N Engl J Med 2004;351:1493–501. Copyright © 2004 Massachusetts Medical Society. All rights reserved.)

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