Fig 2. A 10-year-old boy with Moyamoya disease who presented with weakness of the right upper extremity. Right internal carotid arteriogram in posterior-anterior projection (A) shows that the right proximal anterior cerebral artery is mildly stenotic (black arrow). No steno-occlusive change is found in the ICA or MCA. The right ICA is in stage 1. No Moyamoya vessels are seen. Left internal carotid arteriograms in posterior-anterior projection (B) show that the right distal ICA and the anterior and MCAs are occluded (white arrow). The left ICA is in stage 3. Marked Moyamoya vessels are seen, and peripheral branches of the anterior cerebral artery and MCA are opacified via the collateral vessels (black arrowhead). On the left vertebral arteriogram in posterior-anterior projection (C), no steno-occlusive change is found in the bilateral posterior cerebral artery. The bilateral posterior cerebral artery is in stage 1. Leptomeningeal collateral vessels from the left posterior cerebral artery to the anterior circulation are seen (white arrowhead). MTT map (D) shows the areas of prolonged mean MTT in the left frontal and temporal lobes. This map was calculated with the AIF obtained from a right MCA branch.