What is the recommended revascularization procedure for patients with Moyamoya disease?

Revascularization Procedures for Moyamoya Disease

For patients with moyamoya disease, direct revascularization (STA-MCA bypass) is recommended for adults with hemorrhagic presentation, while combined direct and indirect revascularization procedures are optimal for most patients with ischemic presentation to maximize long-term stroke prevention. 1

Types of Revascularization Procedures

Surgical revascularization procedures for moyamoya disease fall into three main categories:

1. Direct revascularization:

   • Creation of a direct extracranial-intracranial anastomosis
   • Typically superficial temporal artery (STA) to middle cerebral artery (MCA) bypass
   • Provides immediate blood flow to ischemic regions

2. Indirect revascularization:

   • Apposition of vascularized tissues (superficial temporal artery, galea, temporalis muscle, inverted dura) onto brain surface
   • Includes techniques such as encephaloduroarteriosynangiosis (EDAS), encephalomyosynangiosis (EMS), and pial synangiosis
   • Relies on angiogenic proliferation over weeks to months

3. Combined revascularization:

   • Incorporates both direct and indirect techniques in the same procedure

Evidence-Based Recommendations by Patient Population

For Hemorrhagic Moyamoya:

• Direct bypass is strongly recommended based on the Japan Adult Moyamoya (JAM) trial, which demonstrated reduction in rebleeding with direct bypass surgery (2.7%/year) versus medical therapy (7.6%/year) 1
• Particularly beneficial for posterior hemorrhages related to posterior cerebral or choroidal arteries 1

For Ischemic Moyamoya:

• Combined revascularization procedures show excellent long-term outcomes with annual risks of symptomatic hemorrhage and infarction of only 0.4% and 0.2%, respectively 2
• The TODAI protocol (Tokyo Daigaku) demonstrates excellent results with:
  • Combined STA-MCA bypass with EMS for patients ≥10 years old
  • EDAS with EMS for patients ≤9 years old 3

Age-Specific Considerations:

• Children: Indirect revascularization (EDAS, EMS, pial synangiosis) is often preferred due to technical challenges of direct bypass in small vessels 1
• Adults: Direct or combined approaches are feasible and effective 1, 4

Efficacy of Different Approaches

• Direct bypass: Provides immediate revascularization but carries higher technical demands and risk of cerebral hyperperfusion syndrome 1
• Indirect bypass: A review of 143 children with moyamoya treated with pial synangiosis showed reduction in stroke frequency from 67% preoperatively to 3.2% after one year 1
• Combined approach: Long-term studies show stable clinical improvement with significant increase in revascularization area (54.8% of supratentorial area at 5 years) 2

Perioperative Management

Careful perioperative management is crucial to minimize complications:

• Maintain systolic blood pressure at or above patient's asymptomatic baseline (avoid >180 mmHg) 1
• Maintain normocapnia with end-tidal CO₂ between 35-45 mmHg to prevent vasoconstriction 1
• Keep patients euvolemic to mildly hypervolemic 1
• Avoid mannitol 1
• Consider intravenous fluids at 1.5 times normal maintenance rate for 48-72 hours postoperatively 1
• Implement pain management techniques to prevent hyperventilation-induced vasoconstriction 1

Potential Complications

• Cerebral hyperperfusion syndrome (CHS) occurs in approximately 16.5% of cases (19.9% in adults, 3.8% in children) 1
• Risk factors for CHS include older age, severe preoperative hemodynamic impairment, dominant hemisphere surgery, and longer temporary occlusion time 1
• Very high post-anastomosis MCA flow (>30 mL/min) is associated with postoperative stroke, hemorrhage, and transient neurologic deficits 5
• To mitigate CHS, maintain strict blood pressure control (systolic <130 mmHg) 1

Follow-up and Monitoring

• Regular clinical and radiographic follow-up is recommended as 27% of patients with unilateral disease eventually develop bilateral involvement 1
• Techniques such as TCD, perfusion CT, PET, and SPECT with acetazolamide challenge can help monitor cerebral blood flow and assess treatment efficacy 1

Important Caveats

• Endovascular treatment with stents or angioplasty has shown low success rates (25%) and high complication rates in moyamoya disease 1
• Disease progression is more likely in younger patients, and reoperation rates due to refractory disease range from 1.8% to 18% 1
• Antiplatelet agents may be considered for patients who are poor surgical candidates or have mild disease, but evidence for efficacy is limited 1