What are the diagnostic tests for Moyamoya disease?

Diagnostic Testing for Moyamoya Disease

Digital subtraction angiography (DSA) is the gold standard for definitive diagnosis of moyamoya disease, though initial screening is best performed with MRI/MRA to evaluate both cerebral vasculature and brain parenchyma. 1

Primary Diagnostic Approach

Initial Imaging

1. MRI with MRA of the head

   • First-line noninvasive screening test 1
   • Provides evaluation of both brain parenchyma and vasculature
   • Key findings include:
     • Absence of flow voids in the ICA, MCA, and ACA
     • Abnormally prominent flow voids from basal ganglia and thalamic collateral vessels 1
     • T2-weighted FLAIR may show high signal in sulci ("ivy sign"), indicating slow flow 1
     • SWI can demonstrate microhemorrhages (present in up to 52% of patients) 1
     • Diffusion-weighted imaging best for acute infarcts 1
     • T1 and T2 imaging better for chronic infarcts 1

2. Digital Subtraction Angiography (DSA)

   • Required for definitive diagnosis 1
   • Diagnostic criteria include:
     • Stenosis or occlusion of arteries centered on terminal portion of intracranial ICA
     • Presence of moyamoya vessels (abnormal vascular networks) near occlusive/stenotic lesions 1
   • Typically obtained as part of preoperative assessment prior to revascularization 1

Secondary/Supplementary Imaging

1. CT Angiography (CTA)

   • Alternative to MRA for initial and follow-up evaluation 1
   • Can demonstrate vessel narrowing and collateral formation

2. Perfusion Studies

   • Assess cerebrovascular reserve and hemodynamic status:
     • MR perfusion (arterial spin-labeling or dynamic susceptibility contrast) 1
     • SPECT with acetazolamide challenge to assess perfusion instability 1
     • CT perfusion (including xenon-enhanced CT) 1

3. Transcranial Doppler (TCD)

   • Provides noninvasive way to follow changes in blood flow velocities over time 1
   • Useful for monitoring disease progression

Diagnostic Criteria

DSA Criteria (Required findings) 1

1. Stenosis/occlusion in arteries centered on terminal portion of intracranial ICA
2. Moyamoya vessels (abnormal vascular networks) near occlusive/stenotic lesions

MRI/MRA Criteria (Required findings) 1

1. Stenosis/occlusion of terminal portion of intracranial ICA
2. Decreased outer diameter of terminal ICA and horizontal portion of MCA bilaterally on heavy T2-weighted MRI

Clinical Considerations and Pitfalls

• Diagnostic accuracy: MRA has good correlation with conventional angiography (83%), but may overestimate stenosis in some cases (17%) 2
• Limitations of MRA: Less reliable for smaller vessel occlusions compared to DSA 1
• Disease progression monitoring: Periodic clinical and radiographic reexaminations are recommended as 27% of patients with unilateral disease eventually develop bilateral involvement 1
• High-risk populations: Consider screening in patients with neurofibromatosis type 1, Down syndrome, and sickle cell disease, but routine screening of first-degree relatives is not recommended unless multiple family members are affected 1
• Combined approach: Assessment is most thorough when using both MRA and MRI together (sensitivity 92%, specificity 100%) 3

Special Considerations

• Moyamoya disease is bilateral by definition (though may be asymmetric), while unilateral involvement is considered moyamoya syndrome 1
• In adults, moyamoya can present with both ischemic and hemorrhagic events, while children more commonly present with ischemic events 1
• Disease progression occurs in approximately 20% of both symptomatic and asymptomatic adult patients 1

By following this diagnostic algorithm, clinicians can effectively identify and evaluate patients with moyamoya disease, leading to appropriate management decisions that can significantly impact morbidity and mortality outcomes.