Shunt Site Localization of Direct Carotid-Cavernous Fistula Using 3D Rotational Angiography—Utility of Broken-Rim Sign

Abstract

Direct carotid-cavernous fistulas (DCCF) develop due to breach in the integrity of the wall of the internal carotid artery, and its localization can sometimes be difficult due to rapid high flow shunts. We hypothesized that 3D rotational angiography could locate the fistula site accurately, where an interrupted rim of the carotid wall would be silhouetted against opacified vascular structures. This finding was described as a broken-rim sign, and in this study, we assessed the utility of this sign in the localization of the shunt point of DCCF. Retrospective analysis of 15 cases of DCCF was performed, and the rent was characterized based on the broken-rim sign. Two observers independently evaluated the results and compared them against the intraoperative observations. The broken-rim sign was identified and correlated with the actual fistula site in 86.6% and 100% of patients by observers 1 and 2, respectively. The inter-rater agreement was 0.87 (P < 0.001). Misinterpretation was made in 2 patients by 1 observer, due to poor contrast opacification of the vascular structures secondary to very rapid shunting and mild movement artifacts. Our study highlights the role of 3D rotational angiogram and analysis of the carotid wall in the localization of the shunt site in DCCF. The broken-rim sign accurately points to the location of the fistula.