Evolution of ischemic lesion volume in echo-planar diffusion weighted MRI (EP-DWI) was investigat-ed in 17 patients with acute ischemic stroke. Comparing to the follow-up MRI studies, lesion volume expansion up to 317 ml was observed in patients whose initial EP-DWI performed within 17 hours after the onset. Misery perfusion was not observed by PET in patients without significant expansion (>10 ml), but in 2 of 5 patients with such an expansion. Significant lesion volume expansion occurred in patients with 1) acute hemispheric symptoms and signs, such as consciousness disturbance, conjugate deviation of eyes, mild to severe hemiplegia, and cortical signs, 2) vascular occlusion of the internal carotid or the middle cerebral arteries, either embolic or thrombotic in nature, and 3) small ischemic lesion volume in the initial EP-DWI study. Patients exhibiting these clinical features at early stage of ischemia should be regarded as a high risk group for the lesion volume expansion and they might have a substantially large volume of potentially salvageable tissue.
