The pressure-volume function of brain elasticity

Abstract

The intracranial pressure-volume function as determined by brain elasticity was reported in normal dogs. Rapid subarachnoid infusions clearly defined an exponential relationship between pressure and volume. An aliquot technique to measure elastance (dP/dV) at multiple intracranial pressures demonstrated a linear relationship between elastance and pressure. This followed mathematically from the exponential nature of the basic pressure-volume function. The clinical significance of brain elastance measurements was discussed. The effects of pressure on CSF dynamics are superimposed on the pressure-volume function of brain elasticity and probably account for the process of spatial compensation for an expanding mass lesion. It was not apparent that elastance measurements can serve as indicators of impending decompensation, since the pressure-volume function of brain elasticity provided no direct information about CSF dynamics. The clinical usefullness of elastance measurements was seriously questioned.