Figure 1.

Determination of occlusion type by digital subtraction angiography (DSA) and computed tomography angiography (CTA). On contralateral internal carotid artery (ICA) angiogram, collateral flow cannot advance to ipsilateral middle cerebral artery (MCA) through anterior communicating artery (ACOM) because ipsilateral ICA bifurcation (ICBIF) site is involved in branching-site occlusion (A). On the contrary, collateral flow can progress to ipsilateral MCA in truncal-type occlusion (H). In branching-site occlusion, Y- or T-shaped filling defect (clot) involving arterial bifurcation site can be observed on stent retriever deployment (B), on microcatheter angiogram (C), or after minimal recanalization (D). In addition, owing to the involvement of arterial bifurcation site, only one branch that stent retriever is deployed to can be seen on post-deployment angiogram in branching-site occlusion [arrow in (E–G)], while another branch is not seen [missing branch sign; arrowhead in (E–G)]. In truncal-type occlusion, all major branches and its bifurcation site can be clearly observed by stent retriever deployment [(I,J); arrowhead, distal markers of stent retriever], on microcatheter angiogram beyond occlusion, or after minimal recanalization (K). Those can also be observed on CTA images [(L–N); arrow, original occlusion point]. ACA, anterior cerebral artery; M2, superior and inferior divisions of middle cerebral artery; MCBIF, middle cerebral artery bifurcation site; BABIF, basilar artery bifurcation site.