Focal cerebral edema impedes convective fluid/tracer movement through paravascular pathways in cat brain.

Cerebral blood vessels are accompanied by longitudinal paravascular fluid pathways that communicate with the subarachnoid space. After infusion into the subarachnoid space, the tracer protein, HRP, distributes throughout the brain with such rapidity as to suggest that the paravascular fluid transport system serves to flush the entire brain parenchyma. However, it was found that the tracer is largely excluded from regions of experimental vasogenic brain edema as well as from remotely situated white matter in the cold-lesioned hemisphere. The results suggest that the persistence and spread of vasogenic edema may be related to an impairment or disruption of the normal paravascular fluid transport system of the brain.