RT Journal Article SR Electronic T1 Transient obstruction of the internal carotid artery during angiography. JF American Journal of Neuroradiology JO Am. J. Neuroradiol. FD American Society of Neuroradiology SP 1186 OP 1188 VO 18 IS 6 A1 Cross, D T A1 Allen, B T YR 1997 UL http://www.ajnr.org/content/18/6/1186.abstract AB While performing carotid angiography in a 76-year-old man, we found that the right internal carotid artery repeatedly opened and closed during the examination. The patient experienced no related neurologic events. The explanation, confirmed at surgery, was that a flap associated with an atherosclerotic plaque had acted as a ball valve.