Mechanical Basis of the CSF Pressure-Volume Curve

Abstract

The pressure which is built up in the CSF compartment because of the continuous input of fluid is dependent upon the resistance to the outflow of the fluid in the outflow channels and the pressure in the recipient system. Thus, the volume of separate intracranial components including space-occupying masses does not directly affect the fluid pressure under steady conditions. When there is a change, however, in the volume of some component there is an immediate change in the pressure in the same direction. The magnitude of the initial response of the fluid pressure to the volume change is determined by the elastance of the CSF system defined as the slope dP/dV of its pressure-volume curve. A brief description of the pressure-volume curve in the human was presented by RYDER et al. 1953 (1). The present outline of the mechanical properties of the CSF system is based on a series of experiments in dogs recording the pressure-volume curve in different circumstances (2,3,4,5). The pressure-volume curve was obtained by rapid continuous intrathecal injection of fluid with simultaneous measurement of the pressure. The injection rate was selected in order to minimize errors due to the concomitant loss of fluid in the outflow channels and the generation of dynamic pressure gradients.