Time course of tissue elasticity and fluidity in vasogenic brain edema.

We examined chronological changes in regional tissue elasticity (stiffness) and fluidity (1/viscosity) of the white matter during the development and resolution of vasogenic brain edema. Cryogenic injury was created in the cortex of cat brain, and the brain was prepared for measurement of regional tissue elasticity and fluidity. The results were then compared with the histology and tissue water content. Vasogenic edema developed in the white matter under the lesioned cortex (4-24 h) and was resolved by day 10. Regional tissue elasticity decreased significantly during the initial 24 h (45.3 +/- 32.5% of the control (mean +/- S.D.), and then increased to 158.6 +/- 32.3% of the control level at day 10. Regional tissue fluidity increased to 376.7 +/- 240.4% of the control level during the initial 24 h decreased to 77.7 +/- 17.9% of the control level at day 10. Histological examination of the white matter revealed widening of the inter-fiber space at 4-24 h after lesioning and astrocytosis at day 10. Thus vasogenic edema causes an increase of tissue fluidity with a decrease of tissue elasticity. Reactive astrocytosis after the resolution of edema causes an increase of tissue elasticity with mild decrease in tissue fluidity.