Collateral Circulation in Ischemic Stroke: An Updated Review

Abstract

The collateral circulation plays a crucial role in maintaining perfusion to brain tissue in ischemic stroke, which prolongs the time window for effective therapies to be provided and ultimately avoids irreversible damage that may lead to worse clinical outcomes. The understanding of this complex vascular bypass system has advanced greatly in the past few years, yet effective treatments for its potentiation as a therapeutic target remain a challenge. The assessment of the collateral circulation is now part of the routine neuroimaging protocols for acute ischemic stroke, which provides a more complete pathophysiological picture in each patient that allows for a better selection for acute reperfusion therapies and a more accurate prognostication of outcomes, among other potential uses. In this review, we aim to provide a structured and updated approach to the collateral circulation while highlighting ongoing research areas with promising future clinical applications.

Benefit of endovascular treatment for primary versus secondary medium vessel occlusion: A multi‐center experience

“…In this study, the proportion of LMC in patients with primary MeVO was significantly lower than that in patients with secondary MeVO (23% vs. 45%). We speculate that it may be related to the lower pressure gradients at the distal position 40 and the lower proportion of atherosclerotic‐related stroke in distal arterial territories 41 . The difference in collateral circulation compensation between MeVO and LVO needs further study.…”

Review of Cerebral Collateral Circulation and Insight into Cardiovascular Strategies to Limit Collateral Damage in Ischemic Stroke

“…11 In addition to the posterior communicating artery, the anterior and posterior circulation may also be connected via direct carotid-vertebrobasilar connections, which rarely may persist beyond embryonic stages but are very important to recognize when found clinically. 11 The secondary collateral network consists of finer leptomeningeal vessels that exist as a bridge between the distal branches of the primary named cerebral vessels (between ACA-MCA regions, ACA-PCA regions, and MCA-PCA regions) and the cerebellar vessels mentioned above. 10 Studies have shown that the robustness of the network between the ACA-MCA regions is greater than that between PCA-MCA and ACA-PCA regions.…”

“…Such a link facilitates retrograde flow to terminal intracranial cerebral artery branches, which can maintain perfusion even with proximal occlusions of these intracranial vessels. [8][9][10][11] There also exists a tertiary system, which involves vessels established through neoangiogenesis (formation of capillaries from existing blood vessels) and arteriogenesis (de novo formation of blood vessels). 13 Angiogenesis is primarily stimulated by the release of angiogenic growth factors at the peripheries of an ischemic bed.…”

“…Various studies have shown a complete circle exists in less than 50% of cases. 11 In addition to the posterior communicating artery, the anterior and posterior circulation may also be connected via direct carotid-vertebrobasilar connections, which rarely may persist beyond embryonic stages but are very important to recognize when found clinically. 11…”

“…Such a link facilitates retrograde flow to terminal intracranial cerebral artery branches, which can maintain perfusion even with proximal occlusions of these intracranial vessels. 8–11…”