Fig. 1

DSA demonstrating the partial fPCA and complete fPCA. a, b Representative images of partial fPCA on DSA. The arrow on a shows the PComA is continuous as PCA in the same diameter of the lumen, but the arrow on b shows the PCA is originating from the basilar artery. c, d Representative images of complete fPCA on DSA. The arrow on c shows PComA is continuous as PCA in the same diameter of the lumen; the arrow on d shows the right PComA was absent. fPCA, fetal posterior cerebral artery; PComA, posterior communicating artery; PCA, posterior cerebral artery; DSA, digital subtraction angiography