Carotid Artery Stenosis, Extracranial

Diseases,

This section discusses extracranial internal carotid artery stenosis due to atherosclerotic disease.

Diagnosis:

Catheter angiography DSA digital subtraction angiography:

  • Gold standard test
  • NASCET measurement:
    • N= narrowest diameter of residual lumen
    • D= diameter of ICA well beyond the bulb
    • Percentage stenosis= (1-N/D) X 100
  • Useful for:
    • Suspected Total occlusion, Difficult anatomy, Fibromuscular dysplasia, Dissection, Disconcordant tests, Very calcified carotid stenosis

Carotid artery duplex ultrasound (B mode ultrasound +doppler):

  • Moderate stenosis 50-70%
  • Severe stenosis 70-99%
  • Differentiates between atheroma and thrombosis/acute plaque change:
    • Lucent areas in the plaque: corresponding to necrosis or hemorrhage
    • Thickness of fibrous cap: thin cap is associated with ulceration & necrosis
  • Can assess Carotid Intima-Media Thickness

MRA:

  • Time of flight TOF method: over-estimates the occlusion
  • High spatial resolusion CE MRA: for stenosis >70% & for occlusion. Thrombosis may be mistaken for atherma

CTA:

  • Narrowest portion of internal carotid artery correlates to NASCET-style measured stenosis:
  • 2.2mm to 50% NASCET-style stenosis
  • 1.3 mm to 70% NASCET-style stenosis

Transcranial Doppler  ultrasound TCD:

  • Absence of microemboli confers lower risk.

Investigations to consider:

  • Lipid panel: Cholesterol, triglycerides
  • Fasting glucose, HbA1c
  • ECG
  • MRI or CT: silent infarcts for baseline

Treatment:

Address risk factors:

  • BP, Cholesterol, diabetes

Asymptomatic Carotid Artery Stenosis:

  • Antiplatelet:
    • Clopidogrel, or Aspirin +/-dipyridamole, or Cilostazol
  • +/-Revascularization (carotid artery stenting or Endarterectomy) if >70% (debatable but supported by current evidence in spite of high NNT, ACST)

Symptomatic: also see TIA, or stroke section

  • Antiplatelet:
    • Clopidogrel, or Aspirin +/-dipyridamole, or Cilostazol
  • +Revascularization (carotid artery stenting or Endarterectomy) if >70% by NASCET criteria within 2 weeks of symptoms at the latest

Carotid artery stenting (CAS):

  • best done under local anesthesia with consciouss sedation (angioplasty +stenting) [CAVATAS,SAPHIRE,EVA-3S,SPACE, ICSS]
  • Heparin during procedure, protection device is used
  • Aspirin +clopidogrel for 3 months afterwards

Carotid endarterectomy (CEA):

  • Mostly under general anaesthetic, +patch: synthetic or veinous +intraoperative shunt +/-transcranial ultrasound
  • With antiplatelets [Mayo clinic trial]

Things that don’t work:

  • Extracranial-intracranial bypass [EC/IC]

 

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