Fig. 1

(A) On admission head CT was almost normal; (B) CT scan of the skull base shows the absence of the right carotid canal (blue arrow), while the contralateral was normal (red arrow); (C) Aortic arch angiography reveals the following findings: the right ICA was absent, as was the A1 segment of the right ACA; no remnants were observed in either the proximal or distal segments of the right ICA; the right MCA was supplied by the enlarged PCoA and the right ACA was supplied by the ACoA (black arrow points to the general area of the target) ; there was a severe right VAO stenosis and a mild left VAO stenosis (white arrows); blood flow in the right MCA and its branches was insufficient compared to the vessels on the left side; (D, front position) and (E, lateral position) Right CCA angiography reveals no dysplastic ICA; (F) Right brachiocephalic artery angiography shows a right VAO stenosis (white arrows); (G) Angiography after vertebral artery stent implantation demonstrates a significant improvement in the blood flow of the right MCA