Functional activation within the PI-DWI mismatch region in recovery from ischemic stroke: preliminary observations

In this study, we sought to investigate if brain tissue affected by ischemia can accommodate areas of activation related to restoration of brain function following ischemic stroke. In two patients perfusion imaging (PI) and diffusion weighted imaging (DWI) obtained in the acute phase after stroke was coregistered with BOLD imaging of brain functions acquired when profound recovery had occurred. Both patients suffered from thrombembolic brain infarction due to dissection of the internal carotid artery (ICA) characterized by a severe PI-DWI mismatch in the acute stage of stroke. Following ICA recanalization and clinical recovery BOLD imaging showed task-specific activation adjacent to the infarct lesion within the former PI-DWI mismatch area. The data in these two stroke patients provide evidence that brain tissue at risk of infarction as shown by the PI-DWI mismatch can survive and, thereby, constitute the major site underlying post-ischemic recovery.