Why is stenting of the Internal Carotid Artery (ICA) not recommended in patients with Moyamoya disease?

Why Stenting the ICA Should Not Be Performed in Moyamoya Disease

Stenting of the Internal Carotid Artery (ICA) is not recommended in Moyamoya disease due to high complication rates, low success rates (only 25%), and risk of devastating hemorrhage (7%), without evidence of improvement in natural history. 1

Pathophysiological Reasons for Avoiding ICA Stenting

Endovascular treatment with stents or angioplasty fails in Moyamoya disease for several key reasons:

1. Complete Vessel Wall Narrowing: Unlike typical atherosclerotic disease, Moyamoya involves complete vessel wall narrowing rather than isolated luminal stenosis 1

2. Progressive Nature of Disease: Moyamoya is characterized by progressive stenosis of the terminal ICA and development of compensatory collateral vessels 2

3. Complex Hemodynamics: The disease creates complex vortex structures and partial blood hammer phenomena that cannot be adequately addressed by stenting 2

4. Vessel Wall Pathology: Moyamoya involves diffuse wall thickening and proximal stenosis of the extracranial ICA that are significantly associated with poor outcomes after interventions 3

Evidence Against ICA Stenting

The American Heart Association/American Stroke Association's 2023 scientific statement explicitly warns against endovascular treatment in Moyamoya disease:

• Low success rate of only 25% for stenting or angioplasty alone
• High complication rates including devastating hemorrhage in 7% of cases
• No evidence of improvement in natural history 1

Preferred Management Approaches

Surgical Revascularization

Surgical revascularization is the standard of care for Moyamoya disease:

• Direct Bypass: Typically preferred for hemorrhagic presentation (STA-MCA bypass)
• Combined Procedures: Optimal for most patients with ischemic presentation
• Indirect Revascularization: Options include encephaloduroarteriosynangiosis when direct bypass is technically difficult 1, 4

Direct revascularization procedures have been shown to reduce rebleeding rates from 7.6%/year to 2.7%/year in hemorrhagic presentation, while combined procedures provide annual risks of only 0.4% for symptomatic hemorrhage and 0.2% for infarction 4.

Medical Management

For patients who are poor surgical candidates or have mild disease:

• Antiplatelet Therapy: May be considered, though evidence for efficacy is limited 1, 4
• Calcium Channel Blockers: Used in some patients to improve headaches and reduce TIA frequency 1
• Avoid Anticoagulants: Warfarin is generally not recommended due to hemorrhage risk (Class III, Level of Evidence C) 1, 4

Special Considerations

Case-Specific Exceptions

While the general recommendation is against ICA stenting, there are rare documented cases where stenting has been attempted:

• A case report of drug-eluting stent use for supraclinoid ICA stenosis showed no in-stent stenosis at 18-month follow-up 5
• Another case reported successful stenting of the external carotid artery (not ICA) in a patient with Moyamoya 6

However, these isolated cases do not override the strong recommendation against routine ICA stenting in Moyamoya disease.

Monitoring and Follow-up

Regular clinical and radiographic follow-up is essential as:

• 27% of patients with unilateral disease eventually develop bilateral involvement
• Disease progression is more likely in younger patients
• Techniques such as TCD, perfusion CT, PET, and SPECT with acetazolamide challenge can help monitor cerebral blood flow 1, 4

In conclusion, surgical revascularization remains the gold standard treatment for Moyamoya disease, while stenting of the ICA should be avoided due to high complication rates and poor outcomes.