The target of any therapy of acute stroke is the ischemic, still viable tissue, i.e., that part of cerebral tissue in which the level of ischemia is not so severe to have already produced irreversible structural damage. The acute stroke penumbra and infarct core represent physiologic entities that are not identified with conventional MR imaging. The information obtained with diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) along with those obtained with magnetic resonance angiography (MRA) give a complete picture in terms of pathophysiology, diagnosis, and prognosis. DWI allows us to define the size and location of early structural damage. Although there have been occasional reports of reversible areas of DWI hyperintensities, the presence of early DWI abnormalities indicates an irreversible damage in the majority of cases. Early DWI hyperintensity often increases in size during the following days, indicating that the surrounding tissue proceeds towards infarction in a longer time. PWI allows us to investigate hemodynamic parameters in the ischemic tissue. Within the area of early altered diffusion, caused by severe ischemia, both CBV and CBF are severely decreased (core of absent perfusion). Near, but outside the area of early altered diffusion, where the level of ischemia is less severe, different patterns of altered hemodynamics may be observed. The CBF may be at least in part preserved thanks to an increase of CBV. In these surrounding regions there is often a pattern of delayed perfusion, which indicate that the arterial inflow is perturbed by occlusion with subsequent collateral flow.
|Issue number||4 SUPPL.|
|Publication status||Published - 2000|
ASJC Scopus subject areas
- Clinical Neurology