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MR of diffusion slowing in global cerebral ischemia
1Neuroimaging Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892.
Purpose:
To investigate the causal connections between ischemia and the hyperintensity in diffusion-weighted MR images that has been associated with it.
Methods:
Diffusion-weighted and T2-weighted MR imaging were used in a feline global cerebral ischemia/reperfusion model. Single 30-minute vascular occlusions followed by reperfusion were studied. Global occlusions were used to avoid interpretive complications associated with the temporally unstable hemodynamics of the penumbral zones around focal occlusions and the possible growth of the ischemic and penumbral regions with time.
Results:
Diffusion-weighted hyperintensity and the associated diffusional slowing were not attributable exclusively to the cessation of blood flow because: 1) it does not appear abruptly at the onset of ischemia; 2) it resolves slowly early in reperfusion; and 3) it reappears after prolonged reperfusion.
Conclusion:
The times during which diffusion-weighted hyperintensity is manifested during ischemia, and recovers with reperfusion, point to a role for energy metabolism failure.