Background: Only 20% of adults have a “fetal” posterior communicating artery (PCOMM) with carotid flow to the posterior cerebral artery. Dynamic pressure changes at the circle of Willis due to proximal artery occlusion may restore such collateral blood flow patterns. We investigated the findings and implications of PCOMM blood flow in middle cerebral artery (MCA) stroke at angiography in IMS III.
Methods: The angiography core lab prospectively evaluated PCOMM blood flow and collateral circulation in proximal MCA or M1 occlusion. Proximal or distal M1 occlusion was noted with PCOMM flow scored (0-2) on ipsilateral carotid injections before and after endovascular therapy, correlating PCOMM status with ASITN/SIR leptomeningeal collateral grade, TICI reperfusion and subsequent clinical outcomes.
Results: 122 patients with M1 occlusion at angiography (60 proximal, 62 distal) had peri-procedural evaluation of PCOMM status and associated collateral grade. Ipsilateral carotid injections revealed PCOMM flow diversion in 87/122 (71%) prior to revascularization, including 41/60 (68%) in proximal M1 and 46/62 (74%) in distal M1 (p=0.61) occlusions. After treatment, PCOMM patency was noted in 86/122 (71%), with 40/60 (67%) in proximal M1 and 46/62 (74%) in distal M1 (p=0.48) occlusions. Decrease in PCOMM score after therapy was noted in 11/122 (9%); 9/11 (82%) had mTICI 2B-3 reperfusion compared to 48/111 (43%) mTICI 2B-3 reperfusion in those with PCOMM unchanged (p=0.03). PCOMM flow (n=85) was associated with worse ASITN/SIR collaterals (median 2, IQR 2-3) than those without (n=29; median 3, IQR 2-3), p=0.09. PCOMM patency before treatment had 90-day mRS median of 4 (2-6) versus 3 (1-4), p=0.37.
Conclusions: PCOMM flow diversion is common in MCA stroke, revealing an inverse correlation with leptomeningeal collaterals and dynamic changes following reperfusion.