Changes in the Cerebrospinal Fluid Pulse Wave Spectrum Associated with Raised Intracranial Pressure

Abstract

The frequency spectrum of the cerebrospinal fluid (CSF) pulse and the amplitude transfer function between arterial and CSF pressures were measured from the cisterna magna of anesthetized, artificially ventilated cats when the intracranial pressure (ICP) was raised by saline infusion. The spectrum of CSF pulsation was composed of a fundamental and three higher harmonic waves. The amplitude and the amplitude transfer function of each spectral component revealed significant positive correlation with ICP and negative correlation with cerebral perfusion pressure (CPP). Both the amplitude and the transfer function of the fundamental CSF pulse wave showed an exponential correlation with ICP and CPP. A distortion factor of the CSF pulse wave, a measure of its difference from a simple sine wave, was calculated from the spectral components. This showed that distortion of the CSF pulse wave was rapidly and progressively reduced as the ICP rose to 50 mm Hg and then was reduced less thereafter.

Monitoring and interpretation of intracranial pressure

“…30 Pulse transmission between arterial pressure and mean ICP has been investigated by various groups. [31][32][33] It depends upon assumptions about the linearity of the transmission model. Such assumptions are probably unrealistic particularly in pathological circumstances.…”

Index of Cerebrospinal Compensatory Reserve in Hydrocephalus

“…Measuring the fundamental harmonics instead of the full shape of the AMP implies some loss of information. However, similar techniques proved to be useful in waveform analysis of ICP or transcranial Doppler for assessing critical closing pressure (1,32). Generally, good correlation between the AMP first harmonic and the peak-to-peak amplitude is reported within or between patients (19).…”

Bayesian tracking of intracranial pressure signal morphology

“…For example, it has been shown that variations of the ICP pulse morphology are linked to the development of intracranial hypertension [4,5] and cerebral vasospasm [6], acute changes in the cerebral blood carbon dioxide (CO 2 ) levels [7,8], changes in the craniospinal compliance [9], decreased cerebral blood flow [10], and elevated ICP [11]. Therefore, the extraction of morphological features may provide insight to monitor and to understand ICP in an automatic fashion with the ultimate goal of improving the treatment of pathophysiological intracranial and cerebrovascular dynamics.…”