A mathematical study of human intracranial hydrodynamics. Part 1--The cerebrospinal fluid pulse pressure.

An original mathematical model of human intracranial hydrodynamics is proposed. Equations able to mimic the behavior of the intracranial arterial vascular bed, intracranial venous vascular bed, cerebrospinal fluid absorption and production processes, and the constancy of overall intracranial volume are separately presented and discussed. The model parameters were given normal values computed using physiological considerations and recent anatomical data. In this paper the model is used to simulate the genesis and morphology of the intracranial pressure pulse wave. In particular, dependence of the intracranial pressure pulse amplitude on mean intracranial pressure, obtained from the model, shows excellent agreement with recent experimental findings. The model explains the intracranial pressure pulse wave as the result of the pulsating changes in cerebral blood volume (related to cerebrovascular compliance) which occur within a rigid space (i.e., the craniospinal compartment). At low and medium values of intracranial pressure, the intracranial pressure pulse amplitude mainly reflects the cerebral pressure-volume relationship. However, during severe intracranial hypertension, an abrupt increase in the cerebrovascular compliance becomes evident, which is reflected in an abrupt increase in the intracranial pressure pulse wave.