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. 2022 Nov 29;52(4):480–486. doi: 10.1159/000527432

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Copyright © 2022 by The Author(s). Published by S. Karger AG, Basel

This article is licensed under the Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC). Usage and distribution for commercial purposes requires written permission.

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Fig. 2. — Variants of the COW in anterior and posterior circulation. a Variants in anterior circulation. Type I, two normal A1 + AcomA; type II, normal A1 + hypoplastic A1 + AcomA; type III, normal A1 + missing A1 + AcomA; type IV, two normal A1; type V, normal A1 + hypoplastic A1. b Variants in posterior circulation. Type A, two normal P1 + two PcomA; type B, two hypoplastic P1 + two PcomA; type C, normal P1 + hypoplastic P1 + two PcomA; type D, two normal P1; type E, two normal P1 + one PcomA; type F, normal P1 + hypoplastic P1 + one PcomA; type G, normal P1 + missing P1 + one PcomA; type H, normal P1 + missing P1 + two PcomA; type I, hypoplastic P1 + missing P1 + two PcomA; type J, two missing P1 + two PcomA; type K, two homolateral PCA extended from the internal carotid and basilar arteries.