Revascularization for Moyamoya Disease
In patients with moyamoya disease and a history of ischemic stroke or TIA, surgical revascularization with direct or indirect extracranial-intracranial bypass is beneficial for preventing recurrent ischemic events and should be performed. 1, 2
Understanding Moyamoya Disease
Moyamoya disease is an idiopathic rare steno-occlusive disease affecting the arteries of the circle of Willis, typically the anterior circulation. It is characterized by:
- Progressive stenosis of intracranial vessels
- Development of abnormal collateral vessels (the "puff of smoke" appearance on angiography)
- Bimodal age distribution with peaks in childhood and adulthood
- Higher prevalence in Asian populations, though it affects all ethnicities
- Association with conditions like Down syndrome, sickle cell disease, neurofibromatosis, and prior radiation exposure (termed "moyamoya syndrome")
Revascularization Approaches
Direct Revascularization
- Superficial temporal artery to middle cerebral artery (STA-MCA) bypass
- Provides immediate augmentation of cerebral blood flow
- Technically more demanding procedure
- Particularly beneficial for hemorrhagic presentation, reducing rebleeding rates from 7.6% to 2.7% per year 2
- Used in 95.1% of adult patients in large case series 3
Indirect Revascularization
- Includes encephalo-duro-arterio-myo-synangiosis (EDAMS)
- Relies on development of new collateral vessels over time
- Less technically demanding
- May be preferred in pediatric patients or when direct bypass is not feasible
- Used in cases where vessels are too small for direct anastomosis
Combined Approaches
- Direct plus indirect revascularization
- May provide optimal outcomes for ischemic presentation
- Annual risks after combined procedures: 0.4% for symptomatic hemorrhage and 0.2% for infarction 2
Surgical Outcomes and Efficacy
- Surgical morbidity rate of 3.5% and mortality rate of 0.7% per treated hemisphere 3
- Cumulative 5-year risk of perioperative or subsequent stroke or death: 5.5% 3
- 91.8% of patients presenting with TIAs become symptom-free at 1 year or later 3
- Significant improvement in quality of life as measured by modified Rankin Scale 3
- In sickle cell-associated moyamoya syndrome, revascularization reduced stroke rates from 1 per 3.43 patient-years to 1 per 23.14 patient-years 4
Perioperative Management
Pre-surgical Preparation
- Preadmission for intravenous fluid administration
- Arterial line placement before anesthesia induction 2
- Maintain euvolemic to mildly hypervolemic state 2
Intraoperative Management
- Maintain normocapnia
- Avoid mannitol
- Preserve temporal muscle and middle meningeal artery for indirect revascularization 5
- Small arachnoid membrane opening and water-tight closure to avoid post-operative fluid collection 5
Post-operative Care
- Monitor for cerebral hyperperfusion syndrome (occurs in ~16.5% of cases) 2
- Maintain strict blood pressure control (systolic <130 mmHg) 2
- Intravenous fluids at 1.5 times normal maintenance rate for 48-72 hours 2
- Adequate pain management to prevent hyperventilation-induced vasoconstriction 2
Medical Management
- Antiplatelet therapy (typically aspirin monotherapy) may be reasonable in patients with moyamoya disease and history of ischemic stroke or TIA 1, 2
- Avoid medications causing vasoconstriction or inhibiting vasodilation 2
- Anticoagulants such as warfarin are generally not recommended due to hemorrhage risk 2
Rescue Strategies for Failed Revascularization
- Radial artery grafts from external carotid artery to M2 or M3 portion of MCA can be used when STA-MCA bypass fails 6
- This approach has been shown to prevent further cerebrovascular events in patients with failed initial revascularization 6
Follow-up
- Regular clinical and radiographic follow-up is recommended 2
- 27% of patients with unilateral disease eventually develop bilateral involvement 2
- Techniques such as transcranial Doppler, perfusion CT, PET, and SPECT with acetazolamide challenge can help monitor cerebral blood flow 2
Potential Complications
- Transient ischemic attacks may recur for several months after surgery 5
- Chronic subdural hematoma 5
- Cerebral hyperperfusion syndrome 2
- Delayed graft failure, though collateral vessels may develop to compensate 6
Despite significant knowledge gaps and the lack of prospective randomized controlled trials comparing medical management with surgical intervention, the available evidence strongly supports surgical revascularization for patients with moyamoya disease who have experienced ischemic events.