Literature Review

Collar sign in incompletely occluded aneurysms after pipeline embolization: evaluation with angiography and optical coherence tomography

Selected in American Journal of Neuroradiology by JITTAPIROMSAK Pakrit

Authors: Griessenauer CJ, Gupta R, Shi S, Alturki A, Motiei-Langroudi R, Adeeb N, Ogilvy CS, Thomas AJ

Reference: AJNR Am J Neuroradiol. 2017 Feb;38(2):323-326

Published: February 2017

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Wednesday 01 March 2017
Pakrit Jittapiromsak

The collar sign refers to the angiographic appearance of a gap between the parent vessel and an aneurysm. This sign usually occurs at the early follow-up angiography of aneurysm treated by flow diverting stent. 

The authors reviewed 135 aneurysms treated by Pipeline Embolization Device during 2014-2016 in a single institution. Incomplete occlusion was found in 17 aneurysms. Ten of these aneurysms were found to have the collar sign (average 5.5 months). The collar sign had remained on four of these aneurysms at the second follow-up (average 11 months). Optical coherence tomography was done on single remained aneurysm showing variable degree of intimal thickness covering the stent.

Most of aneurysms treated by flow diverting stent show progressive occlusion at following angiography. However, in some particular cases (about 10% in this series) incomplete occlusion may occur. Collar sign seems to be a good sign showing endothelialization, however, incomplete occlusion may persist (up to 40% in this series). Longer follow-up or retreatment is challenging. 

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