Editorial comment--Challenging the concept of a dynamic penumbra in acute ischemic stroke.

Abstract

Ever since the concept of an ischemic penumbra began receiving wider acceptance in the early 1980s,1 much attention and endeavors has been focused on the demonstration of this “salvageable rim” in order to define the usefulness of acute stroke therapy. Several techniques have been applied to demonstrate the extent of the penumbra in acute stroke in humans. Besides that these techniques are mostly very complex and therefore far from being accessible to a considerable proportion of acute stroke patients, the interpretation and generalization of their results in human stroke are complicated by several factors. First, the ischemic penumbra is considered an unstable, dynamic, and transient condition. Moreover, aside from time since onset, several factors like residual/collateral blood flow, metabolic parameters (eg, glucose), temperature, and the anatomical resolution of the technique applied further contribute to a patient’s “individual” penumbra.2 This is reflected by the fact that, second, flow thresholds for various states of tissue perfusion differ considerably among studies and techniques applied.3 Third, given the complexity and effort associated with the majority of methods capable of measuring penumbral tissue, most of our current knowledge derives from rather small cohorts and may not be applicable to subgroups of ischemic stroke, like lacunar infarction. On first gaze, the retrospective study by Jovin et al is not much different from former studies, as it applies a very sophisticated technique (xenon-enhanced CT cerebral blood flow [Xe-CT …