What is the best diagnostic approach for moyamoya disease in pediatric patients?

Diagnostic Approach for Moyamoya Disease in Children

Begin with MRI/MRA as the first-line diagnostic study in all children suspected of having moyamoya disease, and proceed to 6-vessel catheter angiography for definitive confirmation when diagnosis remains uncertain or surgical planning is needed. 1

Initial Imaging: MRI with MRA

MRI should be the initial diagnostic modality for all suspected pediatric moyamoya cases. 1 The following findings on MRI are virtually diagnostic:

• Diminished flow voids in the internal carotid artery (ICA), middle cerebral artery (MCA), and anterior cerebral artery (ACA) 1, 2
• Prominent collateral flow voids in the basal ganglia and thalamus (representing the characteristic moyamoya vessels) 1, 2
• Decreased outer diameter of the terminal ICA and horizontal MCA on heavy T2-weighted imaging 1, 2

MRA can establish the diagnosis when typical findings are clearly present, including bilateral stenosis or occlusion of the terminal ICA. 1, 2 In children with typical bilateral disease, MRI/MRA may be sufficient without requiring catheter angiography. 3, 4

Critical Limitations of MRI/MRA to Recognize

MRA has significant diagnostic limitations that must be understood:

• Misses basal moyamoya collateral vessels in approximately 17% of cases 1, 2
• Misdiagnoses approximately 6-11% of cases overall 1
• Frequently misses smaller-vessel occlusions due to artifact, particularly in early or late disease stages 1, 3
• Shows moyamoya vessels poorly in adults (63% visualization) compared to children (82% visualization) 3

Do not rely on MRA alone when moyamoya vessels are not clearly visualized—proceed to catheter angiography in these cases. 2

Definitive Diagnosis: 6-Vessel Catheter Angiography

Catheter-based 6-vessel angiography remains the gold standard for confirming moyamoya disease in children. 1, 2 This should be performed when:

• MRI/MRA findings are atypical or incomplete 1
• Unilateral disease is suspected (as 20% progress to bilateral involvement) 2
• Surgical planning is needed 1

Advantages of Catheter Angiography:

• Confirms the Suzuki stage of disease progression 1
• Reveals collateral blood supply from external carotid arteries 1
• Guides surgical planning by identifying existing collateral networks that must be preserved 1
• Provides definitive visualization of stenosis/occlusion at the terminal intracranial ICA and moyamoya vessels 2

The complication risk of angiography in children with moyamoya is no higher than in non-moyamoya pediatric populations undergoing cerebrovascular evaluation. 1

Adjunctive Perfusion Studies for Surgical Planning

Cerebral perfusion imaging should be obtained to assess hemodynamic compromise and guide treatment decisions. 1 Options include:

• Acetazolamide-challenged SPECT imaging (measures cerebrovascular reserve capacity) 5
• MRI with arterial spin labeling 2
• Brain CT perfusion 2
• PET with acetazolamide challenge 2

These studies detect regional perfusion instability and cerebrovascular reserve capacity, which are important predictors of stroke risk and determine surgical candidacy. 1, 5 Decreased vascular reserve on SPECT is associated with favorable clinical outcomes after surgery. 6

Inadequate Diagnostic Modalities

CT scanning alone is inadequate to confirm moyamoya diagnosis, though it can identify complications such as hemorrhage and infarcts. 1, 2

CTA has significant limitations in visualizing small moyamoya vessels, though it can identify arterial narrowing and demonstrate collateral vessels in advanced cases. 1, 2

Common Diagnostic Pitfalls to Avoid

• Do not mistake normal flow voids for pathology—the key finding is diminished flow voids in major vessels combined with prominent collateral flow voids in basal ganglia/thalamus 2
• Do not overlook unilateral disease—both unilateral and bilateral involvement satisfy diagnostic criteria 2
• Do not skip catheter angiography in atypical presentations or when MRA fails to visualize moyamoya vessels clearly 1, 2
• Do not delay diagnosis until irreversible hemodynamic changes occur—early diagnosis before infarction is associated with better surgical outcomes 6