What is the diagnostic modality of choice between Computed Tomography Angiography (CTA), 4-Vessel (4V) angiography, and Magnetic Resonance Angiography (MRA) for diagnosing Moya Moya disease in pediatric patients?

Diagnostic Modality of Choice for Moyamoya Disease in Children

Catheter-based 6-vessel angiography (including bilateral ICAs, VAs, and ECAs) is the gold standard for confirming moyamoya disease in children, though MRI/MRA may be sufficient when typical findings are clearly present and catheter angiography is not feasible. 1

Diagnostic Algorithm

Initial Evaluation: MRI with MRA

• All children suspected of having moyamoya should undergo MRI as the first-line diagnostic study (Class II recommendation). 1
• MRI findings virtually diagnostic of moyamoya include: diminished flow voids in the ICA, MCA, and ACA coupled with prominent collateral flow voids in the basal ganglia and thalamus. 1, 2
• MRA can detect stenosis of major intracranial vessels and may establish diagnosis when all typical findings are present, including bilateral stenosis/occlusion of terminal ICA and decreased outer diameter of terminal ICA and horizontal MCA. 2, 3

Confirmatory Testing: Catheter Angiography

• 6-vessel catheter angiography (bilateral ICAs, VAs, and ECAs) is recommended to definitively confirm moyamoya arteriopathy (Class II recommendation). 1
• Catheter angiography provides critical advantages: confirms Suzuki stage, reveals collateral blood supply from external carotid arteries, and guides surgical planning by identifying existing collateral networks to preserve. 1
• The complication risk of angiography in children with moyamoya is no higher than in non-moyamoya pediatric populations undergoing cerebrovascular evaluation. 1

When MRI/MRA Alone May Suffice

• Noninvasive imaging (MRA or CTA) may be sufficient when catheter angiography is not feasible AND typical findings are present with high certainty (Class II recommendation). 1
• This applies particularly to bilateral moyamoya disease in children where MRI shows characteristic findings. 3, 4

Limitations of Each Modality

MRA Limitations

• MRA frequently misses basal moyamoya collateral vessels and smaller-vessel occlusions due to artifact, particularly in adults and early/late disease stages. 1, 4
• MRA misdiagnoses approximately 6-11% of cases and fails to visualize moyamoya vessels in about 17% of cases. 2, 5
• While MRA shows good correlation with conventional angiography for stenotic changes at the carotid fork (83% good correlation), it tends to overestimate stenosis in 17% of cases. 4
• Small moyamoya vessels are poorly shown on MRA, particularly in adults (63% inadequate visualization). 4

CTA Limitations

• CT scanning alone is inadequate to confirm moyamoya diagnosis. 1
• CTA can identify arterial narrowing and demonstrate collateral vessels at the base of the brain in advanced cases, but has significant limitations in visualizing small vessels. 1, 2
• CTA is primarily useful for detecting complications (hemorrhage, infarcts) rather than establishing the diagnosis. 1, 2

Critical Pitfalls to Avoid

• Do not rely on MRA alone when moyamoya vessels are not clearly visualized, as this leads to missed diagnoses in approximately 17% of cases. 2
• Do not use CT or CTA as the primary diagnostic modality—these are inadequate for confirming moyamoya despite their ability to identify some arterial narrowing. 1, 2
• Do not overlook unilateral disease—both unilateral and bilateral involvement satisfy diagnostic criteria, and approximately 20% progress from unilateral to bilateral disease. 2
• In early or end stages of moyamoya disease, diagnosis by MRA should be carefully evaluated as sensitivity is reduced in these phases. 4

Adjunctive Perfusion Studies

• Cerebral perfusion techniques (TCD ultrasonography, Xe-enhanced CT, PET, SPECT with acetazolamide challenge, MRI with arterial spin labeling) are useful for diagnosis, treatment decisions, and follow-up (Class IIb recommendation). 1, 2, 6
• These studies detect regional perfusion instability and cerebrovascular reserve capacity, which are important predictors of stroke risk and guide surgical candidacy. 2, 6