Cerebrospinal Fluid in Diseases in the Nervous System. Cytotoxic edema evolves over minutes to hours and may be reversible, while the vasogenic phase occurs over hours to days, and is considered an irreversibly damaging process. With the rapid accumulation of sodium within cells, water follows to maintain osmotic equilibrium. Increased intracellular calcium activates phospholipases and the release of arachidonic acid, leading to the release of oxygen-derived free radicals and infarction. Normally, the entry of plasma protein-containing fluid into the extracellular space is limited by tight endothelial cell junctions, but in the presence of massive injury there is increased permeability of brain capillary endothelial cells to large molecules.
Vasogenic edema can displace the brain hemisphere and, when severe, lead to cerebral herniation.
The delayed onset of vasogenic edema suggests that time is needed for the defects in endothelial cell function and permeability to develop. Copyright 1997-2001 Internet Stroke Center. All rights reserved.