Assessments of intracranial compliance and lumbar compliance during lumbar infusion. This diagram illustrates the intracranial and lumbar pressure-volume curves and the relationship to the pulsatility parameters. Under normal physiologic conditions with high intracranial compliance, ICP wave amplitude is correspondingly small. As intracranial compliance decreases (steep part of the pressure-volume curve), the brain behaves increasingly like a linear elastance and so variations in intracranial volume correlate increasingly well with changes in ICP wave amplitude, thus the steepness of the pressure-volume curve accounts for large-amplitude ICP waveforms. The cranial pressure-volume curve is left of the lumbar pressure-volume curve, illustrating that compliance is higher in the lumbar compartment.