Hyperacute ischemic stroke missed by diffusion-weighted imaging

Abstract

We present two cases of hyperacute ischemic stroke that were initially missed by diffusion-weighted imaging; abnormalities in locations corresponding to focal neurologic deficits were discovered by MR angiography and perfusion-weighted imaging. Within hours, follow-up diffusion-weighted scans revealed partial conversion of the hypoperfused regions to complete stroke. These cases illustrate the potential for a nonresolving stroke-in-evolution to go undetected by diffusion-weighted imaging at hyperacute timepoints.

fig. 1. 72-year-old woman scanned 3 and 8 hours post ictus. A, Diffusion-weighted imaging reveals a questionable area of restricted diffusion in the left frontal lobe, not identified prospectively. B, Perfusion-weighted imaging demonstrates a large region of delayed time-to-peak (hyperintensity) in the left middle cerebral artery territory. C, Diffusion-weighted imaging at 8 hours shows acute cortical and subcortical infarcts in the left frontal watershed zone. D, T2-weighted image at 8 hours shows no abnormality.

fig. 2. 81-year-old woman scanned 2 and 19 hours post ictus. A, Diffusion-weighted imaging at 2 hours shows subtle restricted diffusion in the left deep cerebral structures, not appreciated prospectively. B and C, Perfusion-weighted imaging bolus-tracking curves (B) for selected regions (C) show approximately 6-second delayed transit to the distal left middle cerebral artery vessels (solid line). D, MR angiography demonstrates decreased flow-related enhancement in the left middle cerebral artery territory. E, Diffusion-weighted imaging at 19 hours reveals acute infarct in left basal ganglia and insular cortex. F, T2*-weighted imaging demonstrates a new 1-cm focus of profound hypointensity in the left putamen, consistent with focal hemorrhage or localized desaturation of hemoglobin. G, CT scan at 2 days reveals a 1-cm focus of petechial hemorrhage in the left putamen surrounded by ischemic infarct.