Intracranial pressure regulation: a comparative model of cerebrospinal fluid systems.

A comparative model of the cerebrospinal fluid (CSF) system in rat, dog and man was derived from manometric data using low volume, short duration infusions into the subarchanoid space in order to describe the mechanisms governing intracranial pressure dynamics. The mathematical model indicates that steady-state elevations of intracranial pressure are regulated primarily by a nonlinear, pressure dependent outflow resistance to CSF reabsorption. While the form of the resistance relationship is similar for the three species tested, differences in the magnitude of CSF outflow parameters are apparent. Model stimulation on a digital computer suggests that parameter changes within the resistance relationship can have a profound effect on the intracranial pressure. In contrast, intracranial compliance acts only to buffer transient changes in volume prior to the establishment of steady-state CSF pressures.