Figure 5: A 15-year-old male presenting with transient right hemiparesis. (a) MRI T2-weighted Turbo Spin Echo image shows vascular abnormality in left portion of the circle of Willis (arrow). (b) MR-angiogram shows a progressive reduction of diameter of the supraclinoid internal carotid artery associated with occlusion of the origin of left middle cerebral artery (curved white arrow) and presence of tiny newly formed compensatory network (white arrows). (c) Intra-arterial digital subtraction angiography better shows the occlusion of left middle cerebral artery and the typical presence of tortuous tiny vessels appearing as the so-called “puff of smoke” (“moya-moya”) (arrow), formed to compensate for the supply blockage.