Fig. 3

Concept diagram of potential volume interrelationships of intracranial compartments and compliance. Since brain volume does not significantly change under normal physiological conditions, it is considered constant and is not included in the diagram. The up and down arrows over the compartments indicate an increase or decrease in the respective fluid flow. The dashed arrows and lines represent hypothetical changes due to limited evidence or controversial data. On the right side, the literature studies supporting the depicted volume distribution and ICC changes are presented. The ICP values in the antiorthostatic position are assumed to increase to an upper normal limit of 20 mmHg in healthy individuals