Intracranial compensation for mass

Normally, the intracranial components are in equilibrium as shown in chamber 1. Initially, the volume of a space-occupying lesion is compensated for by displacement of blood and CSF  and ICP remains normal (chamber 2). When the limits of this  compensation is reached; any additional increase in the volume of the mass lesion is accompanied by a corresponding increase in ICP (chamber 3, decompensated phase).