RT Journal Article SR Electronic T1 Segmental Agenesis of the Internal Carotid Artery Distal to the Posterior Communicating Artery Leading to the Definition of a New Embryologic Segment JF American Journal of Neuroradiology JO Am. J. Neuroradiol. FD American Society of Neuroradiology SP 1189 OP 1193 VO 25 IS 7 A1 Philippe Gailloud A1 Richard E. Clatterbuck A1 Jean H.D. Fasel A1 Rafael J. Tamargo A1 Kieran J. Murphy YR 2004 UL http://www.ajnr.org/content/25/7/1189.abstract AB Summary: We report a case of segmental agenesis of the right internal carotid artery (ICA) in a 53-year-old woman, associated with a saccular aneurysm of the left anterior cerebral artery (A1 segment) presenting with a right hemispheric transient ischemic attack. The agenetic segment was located distal to the origin of the posterior communicating artery (PComA), as documented both angiographically and by direct surgical inspection. This observation suggests the existence of a previously unrecognized embryologic segment of the ICA, located between the PComA origin and the terminal bifurcation of the ICA into the anterior and middle cerebral arteries.