Estimation of Severity of Moyamoya Disease with [15O]Water-Positron Emission Tomography Compared with Magnetic Resonance Imaging and Angiography.

BACKGROUND Moyamoya disease is a steno-occlusive disease of the circle of Willis with growth of pathologic collaterals. We compared functional perfusion imaging ([15O]water-positron emission tomography [PET] with acetazolamide challenge) with conventional magnetic resonance imaging (MRI) and angiography for determining indication for cerebral revascularization in patients with moyamoya. METHODS We performed a retrospective blinded analysis of individual imaging modalities (MRI, angiography, PET) and scored each modality for severity of disease in 21 untreated patients with moyamoya with 78 affected vascular territories. RESULTS Positive predictive value to identify insufficient perfusion on angiography and MRI together was 98.3% as proven on combined PET/computed tomography. Negative predictive value to identify sufficient perfusion on angiography and/or MRI only was 60%. Negative predictive value to predict good perfusion on PET based on MRI (no infarctions in the respective territory) was only 17%. An assumed good perfusion based on the suggestion of good collaterals on angiography was correct in only 13.4% of cases. Positive predictive value (angiography of main vessel and weak or no collateralization) to predict insufficient perfusion on PET/computed tomography was 76.9%; negative predictive value (angiography of main vessel and strong collateralization) to identify good perfusion was 13.4%. CONCLUSIONS Reliable evaluation of cerebral blood flow might not be possible with angiography and basic MRI alone. We strongly recommend additional functional imaging (e.g., [15O]water-PET with acetazolamide challenge) to precisely evaluate the indication for cerebral revascularization.