Diffusion-negative stroke: a report of two cases

Abstract

Diffusion-weighted MR imaging is generally thought to be highly sensitive for the diagnosis of acute stroke. We report two cases of hyperacute stroke with absence of changes on diffusion-weighted images within 4 hours of symptom onset. Follow-up studies, performed 4 days later, showed infarction in regions compatible with the clinical presentation and (in one case) with the initial perfusion deficit. These cases indicate that normal findings on diffusion-weighted images in patients with suspected cerebral ischemia do not rule out impending infarction.

fig 1.

Case 1: 67-year-old man with word-finding and comprehension difficulties imaged 4 hours (top row) and 4 days (bottom row) after symptom onset. The T2-weighted (T2W), diffusion-weighted (Isotropic DWI), and D_av images were all normal at 4 hours; but at 4 days, the T2-weighted image showed an area of infarction in the left parietal region (arrows).

fig 2.

Case 2: 65 year-old man with mild to moderate aphasia, a slight left-sided facial droop, and minimal left pronator drift scanned 3.5 hours (top row), 13 hours (middle row), and 4 days (bottom row) after symptom onset. Top row, Initial T2-weighted (T2W), diffusion-weighted (Isotropic DWI), and D_av images were normal, but the perfusion MR image revealed a large area of delayed flow in the right MCA territory. Middle row, At 13 hours, the T2-weighted image remained normal but diffusion-weighted hyperintensity and reduced D_av are now apparent in the right MCA territory. Bottom row, T2-weighted image at 4 days revealed hemorrhagic infarction with edema and mild mass effect. The infarct showed decreased D_av at this time, while the perilesional edema had increased D_av.