NF1 and neurofibromatosis type 1: Radiographically, the MRI appearance of NF1-related and non-NF1 moyamoya is indistinguishable, with both groups showing FLAIR hyperintensity (“ivy sign”) in underperfused cortex, a characteristic narrowing of the parent vessels in the anterior circulation of the brain, and in later stages evidence of collateral formation and strokes in the same vascular distribution [25].