Collaterals in ischemic stroke

Collateral flow plays a pivotal role, both in acute and chronic phases of cerebral ischemia. Recruitment of these redundant vascular networks maintains cerebral blood flow to ischemic areas, while primary arterial conduits are obstructed either due to steno-occlusive or acute occlusive lesion. Until recently, a heavy focus had been placed solely on such impaired antegrade flow, while the contribution from primary and secondary collateral pathways has been largely disregarded. Imaging of the brain with focus on delineating the collateral circulation has been critical to interpret the mechanism of vascular remodeling that occurs with ischemic injury. Recent multimodal imaging modalities have encouraged physicians to assess collateral flow and hemodynamics from a temporal perspective, distinguishing individual cases to tailor the treatment. Collateral status varies among individuals, correlating with stroke severity and reperfusion outcomes. While new techniques to enhance collateral flow have been speculative, we provide a comprehensive review on the role of collaterals and its therapeutic applications during cerebral ischemia. (c) 2020 Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).