This study highlights the applicability and technique of examination of both diffusion weighted imaging and perfusion weighted imaging. Perfusion-weighted imaging (PWI) lesion estimates the region of acute dysfunctional brain tissue, whereas the acute diffusion-weighted imaging (DWI) lesion appears to correspond to the core of the early infarction. The mismatch between the acute PWI lesion and the smaller DWI lesion represents potentially salvageable brain tissue (an estimate of the ischemic penumbra). In patients with a PWI/DWI mismatch, early reperfusion is often associated with substantial clinical improvement and reversal or reduction of DWI lesion growth.