The Influence of Body Position on Cerebrospinal Fluid Pressure Gradient and Movement in Cats with Normal and Impaired Craniospinal Communication

Marijan Klarica,# 1 , * Milan Radoš, 1 Gorislav Erceg, 1 Antonio Petošić, 2 Ivana Jurjević, 1 and Darko Orešković# 3

Abstract

Intracranial hypertension is a severe therapeutic problem, as there is insufficient knowledge about the physiology of cerebrospinal fluid (CSF) pressure. In this paper a new CSF pressure regulation hypothesis is proposed. According to this hypothesis, the CSF pressure depends on the laws of fluid mechanics and on the anatomical characteristics inside the cranial and spinal space, and not, as is today generally believed, on CSF secretion, circulation and absorption. The volume and pressure changes in the newly developed CSF model, which by its anatomical dimensions and basic biophysical features imitates the craniospinal system in cats, are compared to those obtained on cats with and without the blockade of craniospinal communication in different body positions.

During verticalization, a long-lasting occurrence of negative CSF pressure inside the cranium in animals with normal cranio-spinal communication was observed. CSF pressure gradients change depending on the body position, but those gradients do not enable unidirectional CSF circulation from the hypothetical site of secretion to the site of absorption in any of them. Thus, our results indicate the existence of new physiological/pathophysiological correlations between intracranial fluids, which opens up the possibility of new therapeutic approaches to intracranial hypertension.


""CSF pressure is usually measured while a person is lying in a horizontal recumbent position. Normal CSF pressure values, in that case, are around 15 cm H2O, and the pressure is the same along the spinal subarachnoid space and inside the cranium [1]. Thus, according to the data that is available, in a horizontal position there is no hydrostatic pressure gradient that would be necessary in order for CSF to circulate inside the cranial and spinal CSF space.

In sitting subjects (upright position), Masserman [9], Loman [10], Loman et al. [11], Von Storch et al. [12], O'Connell [13], Magnaes [14], [15] and many others all found fluid pressure to be at the atmospheric pressure level in the upper cervical region or at the level of the foramen magnum. Inside the lumbar region, the pressure is positive and its value corresponds to the distance from the CM to the measuring site in the lumbar region. This fact raises a question: How can CSF circulate through the spinal subarachnoid space from the CM to the lumbar region while we are in an upright position? That circulation direction would be contrary to the hydrostatic pressure gradient.

Furthermore, it is known that the change in body position (from horizontal to upright, head up or sitting position) is followed by a transient fall in intracranial pressure (ICP) [14], [15] to the subatmospheric value, and it results in a new pressure gradient along the craniospinal axis. It is generally accepted that this decrease lasts for a very short period of time, and that the ICP remains positive. Namely, according to the classical hypothesis, in physiological conditions the rate of CSF secretion (Vf) should be the same as the rate of absorption. Otherwise, when absorption is lesser than secretion, CSF will accumulate and increase the intracranial pressure [16]. The famous formula of professor Marmarou [16] links the classical concept of CSF physiology and intracranial pressure:"
The Influence of Body Position on Cerebrospinal Fluid Pressure Gradient and Movement in Cats with Normal and Impaired Craniospinal 
Apology's if animal experiments don't sit well with you. They don't with me and are unnecessary.

The Influence of Body Position on Cerebrospinal Fluid Pressure Gradient and Movement in Cats with Normal and Impaired Craniospinal Communication
Marijan Klarica,# 1 , * Milan Radoš, 1 Gorislav Erceg, 1 Antonio Petošić, 2 Ivana Jurjević, 1 and Darko Orešković# 3


https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3991613/?fbclid=IwAR3WBoewDLDGguFc0eHS4el7mP6QCzY-IYygEhVo1XOKUWCd0lH5wLLoRx4

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