Dynamics of cerebral edema. The role of an intact vascular bed in the production and propagation of vasogenic brain edema

Brain edema was produced in cats by a standardized cortical freezing lesion. With a careful microsurgical technique, the injured cortex was removed as a single piece, either immediately after induction or at 2, 4, or 8 hours after lesion production. The injured brain was either discarded or replaced in its bed. Brain edema and the defect in the blood-brain barrier were assessed by determining percent dry weight, increase in volume of white matter, and spread of Evans' blue by planimetry. The results indicate that if the lesion is removed immediately after production, formation of the expected vasogenic brain edema is completely abolished; replacement of the frozen brain is unable to induce significant increase in permeability if the surrounding blood-brain barrier or a significant amount of brain edema; and if the lesion is removed at 2,4, or 8 hours with or without replacement, advancement of the edema front and increase in the amount of edema is stopped. It appears that an intact vascular bed is necessary for the extracellular fluid component of brain edema, and that no edemagenic factors exist within the injured brain in this model that influence either the production or propagation of the increased extracellular fluid volume.