Moyamoya Disease: Clinical Overview
Presentation
Moyamoya disease presents with either ischemic or hemorrhagic strokes, with clinical manifestations varying by age and disease stage. 1
Key Clinical Features:
- Ischemic presentations: Transient ischemic attacks (TIAs), completed strokes, or crescendo TIAs—most common in adults
- Hemorrhagic presentations: Intracranial hemorrhage, particularly from fragile collateral vessels
- Additional manifestations: Cognitive deficits, migraine-like episodes, psychiatric disorders, movement disorders (from basal ganglia collateral proliferation) 2, 3
Critical pitfall: Adults may present with sudden-onset stroke even in early angiographic stages without preceding TIAs, potentially due to acute in situ thrombotic occlusion at stenotic sites 4. This challenges the traditional view that symptoms are purely hemodynamic.
Diagnostic Workup
Digital subtraction angiography (DSA) remains the gold standard for diagnosis, showing progressive stenosis of the terminal internal carotid arteries and proximal branches with characteristic "puff of smoke" collateral vessels. 5, 3
Diagnostic Algorithm:
Initial imaging:
- Non-contrast CT head: Rule out acute hemorrhage in acute presentations
- MRI with DWI/ADC sequences: Detect acute ischemic stroke with diffusion restriction 3
- MR angiography: Identify bilateral (or unilateral) middle cerebral artery stenosis 2
Confirmatory imaging:
- DSA: Required for definitive diagnosis—visualizes steno-occlusive lesions and moyamoya collaterals 5
- 3D constructive interference in steady-state MRI: Useful for differentiating moyamoya from atherosclerosis 6
Hemodynamic assessment:
- CT perfusion or PET: Identify ischemic vascular territories and assess cerebral blood flow impairment—critical for surgical planning 7, 3
- Vessel wall MRI: May show marked contrast enhancement at stenotic sites, potentially indicating acute thrombotic risk 4
Important update: Recent Japanese guidelines removed the requirement for bilateral involvement—unilateral disease is now recognized given evidence of progression to bilateral involvement 6.
Treatment
Surgical revascularization is the definitive treatment to reduce stroke risk and improve cerebral perfusion; medical therapy alone does not halt disease progression. 1
Treatment Algorithm by Presentation:
For hemorrhagic moyamoya:
- Direct bypass surgery is strongly recommended based on the Japan Adult Moyamoya trial showing significant reduction in rebleeding (2.7%/year vs 7.6%/year with medical therapy alone, P=0.04) 1
- Posterior hemorrhages (from posterior cerebral/choroidal arteries) benefit most from surgical intervention 1
For ischemic moyamoya:
- Combined bypass surgery (direct + indirect) is the most effective approach based on long-term data showing low complication rates (6.3%) and low postoperative stroke rates 7
- Direct bypass provides immediate revascularization; indirect bypass relies on angiogenesis over days-weeks 1
- No randomized trials exist for ischemic disease, but meta-analyses support surgical benefit over medical management alone 1
Medical management:
- Antiplatelet therapy can be considered reasonable per recent guidelines 6
- Medical therapy alone has failed to halt disease progression 3
- Endovascular stenting fails to prevent ischemic events and does not halt progression—avoid this approach 6
Surgical Techniques:
- Direct bypass: Superficial temporal artery to middle cerebral artery anastomosis—technically demanding but provides immediate flow
- Indirect bypass: Apposition of extracranial tissues (STA, galea, temporalis muscle, dura) onto brain surface for synangiosis
- Combined approach: Currently most effective strategy 7
Perioperative Management
Meticulous anesthetic management is critical to prevent perioperative complications, particularly cerebral hyperperfusion syndrome (CHS) which occurs in 16.5% overall (19.9% in adults). 1
Perioperative Protocol:
- Preadmission IV hydration overnight while NPO to prevent hypotension
- Arterial line placement before anesthesia induction
- Blood pressure management: Maintain systolic BP at or above preoperative baseline; avoid >180 mmHg 1
- Ventilation: Maintain normocapnia (end-tidal CO₂ 35-45 mmHg)—hypocapnia causes vasoconstriction and ischemia
- Volume status: Keep euvolemic to mildly hypervolemic; avoid mannitol (causes hypotension and decreased cerebral perfusion) 1
Postoperative CHS prevention:
- Strict blood pressure control with systolic BP <130 mmHg 1
- Monitor for transient neurological deficits (70.2% of CHS cases), hemorrhage (15%), and seizures (5.3%) 1
- Risk factors: Older age, severe preoperative hemodynamic impairment, dominant hemisphere surgery, longer temporary occlusion time 1
Special Considerations
Genetic testing: RNF213 p.R4810K variant is a key susceptibility factor, particularly in East Asian populations 5
Disease progression: Unilateral disease commonly progresses to bilateral involvement—serial imaging surveillance is essential 6
Timing of surgery: Early diagnosis and timely surgery are crucial for prognosis, especially in children where interdisciplinary management is essential 7