Alterations of Brain Water with Increased Intracranial Pressure

Abstract

The presence or absence of a cerebral extracellular space bulk flow continues to be a debated point with accumulated evidence on both sides of the issue. A few Years ago we presented data from a modification of the cortical subarachnoid diffusion technique which we felt was most consistent with a cortical bulk flow arising from the locus of greatest capillary surface area which exists in lamina IV. Extracellular space (ECS) fluid arising from transcapillary bulk flow would be directed both toward the subarachnoid space and toward the deeper cortical laminae and white matter, but the restricted ECS of the dense cell body layer, lamina II, offers such a high flow resistence that all of the flow is redirected centripetally toward the white matter. It has been argued that the diffusion profile from which we supported our hypothesis could as easily be interpreted to show no bulk flow existed in the cortical ECS, only simple diffusion.