An experimental study on artificially induced CSF pulse waveform morphological modifications

The analysis of cerebrospinal fluid (CSF) pulse pressure waveform has been considered as a reliable method to investigate the intracranial system (ICS) dynamics. We have examined the morphological changes of the CSF pulse wave and of the sagittal sinus pressure (SSP) wave during a progressive increase in intracranial pressure (ICP) in order to investigate the ICS dynamics.

Four dogs were anesthetized. Blood pressure, ICP, and SSP were simultaneously recorded. Two vertical tubes were inserted inside one lateral ventricle, thus allowing the half-opening (one tube open) and opening (both tubes open) of the ICS. ICP was modified by varying the height of the liquid column into the tubes. Pressures were analyzed by applying the fast Fourier transformation on each pulse pressure wave. We distinguished two peaks (first and second peaks) and a notch in each pulse pressure wave. The pressure was raised from resting pressure up to 50 mmHg.

A progressive and distinct change in the CSF pulse pressure shape was evident when opening the ICS to the atmosphere: a reduction in the height of the dicrotic notch and in the amplitude of the second peak and a corresponding positive shift of the first harmonic with respect to the onset of the CSF pulse pressure wave.

A decrease in the amplitude of the CSF pulse waveform second peak and a positive phase shift of its first harmonic indicate an opening of the ICS to the atmosphere, i.e. an increase in the intracranial compliance.