Collateral perfusion: time for novel paradigms in cerebral ischemia.

Collateral circulation and associated potential compensation in downstream perfusion have been recognized long before arterial occlusions were known to cause ischemic stroke. Arterial aspects and the venous capacity of collaterals to offset potentially devastating effects of blocking a cerebral artery have been studied in various animal species and even human populations with stroke, providing a framework for translational research. The time has come for collaterals to move from the periphery to a central position in stroke therapeutics, propelled by the momentum of imaging data and culminating in novel paradigms with respect to time, imaging approaches and treatment strategies. It is time for a concerted focus on collateral perfusion to harness potential therapeutic advances from acute stroke to chronic cerebrovascular disorders.