Changes of frequency spectrum of the CSF pulse wave caused by supratentorial epidural brain compression.

The frequency spectrum of the CSF pulse wave and amplitude transfer function from arterial to CSF pressure were estimated in the lateral ventricle and cisterna magna during the course of supratentorial epidural compression of brain in anaesthetised ventilated cats. Ventricular fluid pressure, the amplitude of spectral components of the CSF pulse and the amplitude of transfer function in the supratentorial compartment were increased in an exponential manner as epidural compression advanced. A transtentorial pressure gradient developed when epidural compression exceeded a critical level. Conduction of the CSF pulse through the tentorial hiatus decreased in an exponential manner when plotted against the transtentorial pressure gradient. Transtentorial conduction of the CSF pulse may serve as a sensitive indicator of the development of tentorial herniation.