What is an Internal Carotid Artery (ICA) dissection?

Internal Carotid Artery (ICA) Dissection: Definition and Management

Internal carotid artery dissection is a condition where an intimal tear in the arterial wall initiates an intramural hematoma, causing stenosis (with subintimal dissection) or aneurysmal degeneration (with subadventitial dissection). 1

Pathophysiology and Epidemiology

ICA dissection occurs when blood enters the arterial wall through an intimal tear, creating a false lumen that can:

• Lead to stenosis or occlusion when subintimal
• Result in aneurysmal dilation when subadventitial
• Account for approximately 2% of all ischemic strokes
• Represent 10-15% of strokes in younger patients (under 45 years) 1

The annual incidence is approximately 2.5-3 per 100,000 population 1.

Etiology

ICA dissection can be:

1. Spontaneous - occurring without identifiable trauma
2. Traumatic - associated with:
   • Minor trauma (hyperflexion/hyperextension of neck)
   • Chiropractic manipulation
   • Coughing or nose blowing
   • Motor vehicle accidents 2

Risk Factors and Associated Conditions

• Fibromuscular dysplasia (present in ~15% of cases)
• Connective tissue disorders:
  • Ehlers-Danlos syndrome type IV
  • Marfan syndrome
  • Autosomal dominant polycystic kidney disease
  • Hyperhomocysteinemia
  • Osteogenesis imperfecta 1

Clinical Presentation

The classic presentation includes:

• Unilateral head or neck pain
• Horner syndrome (ptosis, miosis, anhidrosis)
• Cerebral or retinal ischemic symptoms in 50-95% of cases 1
• Pulsatile neck mass 1

Stroke patterns in ICA dissection are predominantly:

• Cortical infarcts (most common)
• Large subcortical infarcts
• Less frequently: small subcortical or junctional infarcts 3

Diagnosis

Imaging Modalities

Class I recommendation: Contrast-enhanced CTA, MRA, and catheter-based contrast angiography are useful for diagnosis of cervical artery dissection. 1

Diagnostic approaches include:

1. MRI/MRA with fat-saturated T1 imaging - Preferred first-line imaging to visualize the intramural hematoma 1

2. CT Angiography (CTA) - Excellent for visualizing the dissection flap and vessel lumen 1

3. Carotid Duplex Ultrasonography - May identify:

   • Dissection flap
   • Differential flow in true and false lumens
   • However, may miss dissections above the angle of the jaw 1, 4

4. Digital Subtraction Angiography - Gold standard for detailed vascular imaging when planning interventions 5

Ultrasonographic findings suggestive of dissection include:

• Direct visualization of intramural hematoma or double lumen
• Distal stenosis/occlusion with Horner's syndrome or cranial nerve palsies
• Distal stenosis/occlusion with spontaneous recanalization within weeks 4

Management

Medical Treatment

Class IIa recommendation: Antithrombotic treatment with either an anticoagulant (heparin, low-molecular-weight heparin, or warfarin) or a platelet inhibitor (aspirin, clopidogrel, or extended-release dipyridamole plus aspirin) for at least 3 to 6 months is reasonable for patients with extracranial carotid or vertebral arterial dissection associated with ischemic stroke or TIA. 1

Treatment approach:

1. Initial therapy: Anticoagulation with intravenous heparin or LMWH
2. Maintenance therapy: Warfarin for 3-6 months or antiplatelet therapy
3. Long-term: Consider transitioning to antiplatelet therapy after symptom resolution 1

The choice between anticoagulation and antiplatelet therapy remains controversial as no randomized trials have definitively established superiority of either approach 1.

Surgical/Endovascular Management

Class IIb recommendation: Carotid angioplasty and stenting might be considered when ischemic neurological symptoms have not responded to antithrombotic therapy after acute carotid dissection. 1

Indications for intervention include:

• Persistent or recurrent symptoms despite medical therapy
• Progressive dissection with pseudoaneurysm formation
• Hemodynamically significant stenosis 5

Surgical options include:

• Direct carotid repair
• Resection with vein graft replacement
• Cervical-to-intracranial ICA bypass for distal dissections 6

Prognosis and Follow-up

• Recanalization occurs in approximately 60% of children with CCAD 1
• Risk of recurrent stroke or TIA is approximately 12% 1
• Annual recurrence rate of dissections is approximately 1%, higher in younger patients and those with family history 1

Pitfalls and Caveats

1. Diagnostic challenges:

   • Dissections above the angle of the jaw may be missed by ultrasound
   • Intracranial dissections may carry higher risk of subarachnoid hemorrhage with anticoagulation

2. Treatment considerations:

   • Avoid anticoagulation in patients with intracranial dissections due to potential increased risk of subarachnoid hemorrhage 1
   • Consider the balance between bleeding risk and thrombotic risk when choosing antithrombotic therapy

3. Monitoring:

   • Regular imaging follow-up is essential to monitor recanalization and detect potential complications