Internal carotid artery dissection

Internal carotid artery dissection, like arterial dissection elsewhere, is a result of blood entering the media through a tear in the intima 1 and is a common cause of stroke in younger patients.

Dissection may occur at any age, but is a common cause of stroke in young patients (20-25% of strokes in patients less than 45 years of age 3,6). Craniocervical arterial dissections (including vertebral artery dissections) have an estimated incidence up to 5 cases per 100,000 in the general population 9.

The classical presentation includes 6:

Unfortunately, this constellation of symptoms and signs is found in less than one-third of patients. Due to a lack of specific signs, the diagnosis often goes unrecognised for some time 6.

Causes of dissection can be separated into spontaneous, traumatic and iatrogenic 3:

  • spontaneous
  • traumatic
    • motor vehicle accidents, sport-related, strong coughing or nose blowing, chiropractic manipulation, lengthy telephone conversations 4,6
  • iatrogenic

The internal carotid arteries, like the vertebral arteries, have differing distribution of elastic fibres compared to similar sized vessels elsewhere (this has been disputed by FT Merei 12).  Although the tunica media and tunica adventitia are present they are only a third as thick as their extracranial counterparts, with the vast majority of elastic fibres located in a subendothelial elastic lamina. This fundamental difference accounts for the markedly different natural history of intracranial arterial dissections compared to their extracranial counterparts. When a tear breaches the aforementioned subendothelial elastic layer, then there is little tissue preventing extension into the subarachnoid space, thus accounting for the very high rate of subarachnoid haemorrhage.

  • Non-contrast brain CT is insensitive for dissection but may demonstrate
    • ischaemic changes within the brain
    • arterial wall haematoma in the upper portion of the ICA: spontaneous crescent-shaped hyperattenuating focus 9
  • CTA may demonstrate 7,9
    • enlargement of the dissected artery
    • an abnormal vessel contour (see DSA below): generally considered highly specific and sensitive
    • classical appearance: narrowed eccentric lumen surrounded by a crescent-shaped mural thrombus and thin annular enhancement (vasa vasorum enhancement in the adventitia)
    • intimal flap
    • dissecting aneurysm (internal carotid artery pseudoaneurysm)
  • high signal crescent sign within the wall of the vessel
  • absent flow-void
  • abnormal vessel contour on MRA (see DSA below)
  • evidence of cerebral ischaemia

Although considered the gold standard, digital subtraction angiography does not always demonstrate definite signs of ICA dissections as the thickness and contents of the arterial wall may not be clearly demonstrated 9. The following may be evident:

Conservative medical management is often all that is required. This consists of antiplatelet therapy, with or without anticoagulation 3. If the patient is symptomatic and there are ongoing ischaemic events that are not controlled by medical management, endovascular treatment may be of benefit. Endovascular options include gentle angioplasty and stent placement 3.

Surgical intervention has a limited role in modern practice and usually consists of bypass or ligation. Detailed knowledge of the circle of Willis anatomy is essential when assessing collateral pathways.

  • fibromuscular dysplasia
    • ICA bilateral involvement reported in ~65% 9
    • multifocal stenosis with adjacent dilatations also referred to as the string of beads sign
  • atherosclerosis
    • involves the carotid bulb
    • ulcerated plaque may mimic an intimal flap on axial images
  • dysgenesis of the ICA
    • carotid canal is absent or hypoplastic
  • isolated traumatic ICA pseudoaneurysm
    • may be indistinguishable from a dissection pseudoaneurysm
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Article information

rID: 6692
Synonyms or Alternate Spellings:
  • Internal carotid arterial dissection
  • Internal carotid artery (ICA) dissection
  • Carotid dissection
  • ICA dissection

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Cases and figures

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    Marfans Dissection
    Case 1: with Marfan syndrome
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    Case 2: with string sign
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    Case 3: with crescent sign
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    Case 3: with Horner syndrome
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    Case 4
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    Case 5: on right side
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    Case 6: on the right side
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    Case 7: traumatic
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    Case 8
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    Case 9
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    Case 10: multimodality holistic case
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    Case 11: left with hyperdense crescent
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    Case 12: right internal carotid artery dissection
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