Effect of osmolarity on CSF volume during ventriculo-aqueductal and ventriculo-cisternal perfusions in cats

Development of hydrocephalus and classical hypothesis of cerebrospinal fluid hydrodynamics: Facts and illusions

“…Thus, the increase in CSF osmolarity as compared to the blood and surrounding tissue, enhanced CSF volume, and vice versa. This was confirmed by a very recent investigation (Maraković et al, 2010) in which it was shown that the volume of the CSF depends on both CSF osmolarity and the size of the contact area between the CSF system and the surrounding tissue exposed to hyperosmolar CSF. It means that if a larger contact area had been included, a stronger effect, i.e., larger increase in CSF volume, would be obtained.…”

“…In experiments in which the choroid plexuses (main site of CSF secretion) have been removed, no changes in the volume and composition of the newly formed CSF have been observed (Milhorat, 1969;Milhorat et al, 1976). Furthermore, it has been shown that there is no net formation of CSF in isolated brain ventricles, and that CSF does not circulate along the CSF system, but rather that permanent CSF changes happen within the surrounding tissue, depending on the fluid osmolarity (Bulat et al, 2008;Maraković et al, 2010;Orešković et al, 2001;Orešković et al, 2002;Wald et al, 1976). By monitoring the behavior of different substances in the CSF of some patients, it was also concluded that CSF is formed everywhere and absorbed everywhere inside the CSF cavities (Di Chiro, 1964;1966).…”

“…Recent experimental works have shown that the hypothesis regarding CSF circulation is hardly sustainable/explicable (Bulat and Klarica, 2010;Bulat et al, 2008;Maraković et al, 2010;Orešković and Klarica, 2010;Orešković et al, 2002). Since water constitutes 99% of CSF volume (Bulat and Klarica, 2010), and since, by definition, CSF circulation means the circulation of CSF volume, it is apparent that water should demonstrate the dynamics (bulk flow) of the CSF.…”

“…Therefore, the maintenance of CSF volume is the maintenance of water volume, while CSF hydrodynamics is the hydrodynamics of water. We have suggested that the control of ISF-CSF volume is influenced by hydrostatic and osmotic forces in CNS microvessels (Bulat, 1993;Maraković et al, 2010;Orešković et al, 2000;Orešković et al, 2002;Orešković et al, 1991, Orešković and and that CSF volume will change depending on the prevalence of those forces. Thus, the total volume of CSF is not dependent on CSF secretion inside the brain ventricles and the passive CSF absorption in subarachnoid space, but rather depends on a permanent dynamic change in water volume along the entire CSF system (Fig.…”

“Compensated hyperosmolarity” of cerebrospinal fluid and the development of hydrocephalus

“…As there are almost no obstacles/barriers for water within the CNS, and as water quickly and easily crosses from one compartment to another (blood, CSF, ISF, intracellular fluid), the cause of excessive fluid accumulation should be searched for in pathophysiological conditions leading to the displacement of water into the CSF space, and its accumulation within the CSF system. It is well documented that osmotic gradients play a significant part in the regulation of brain water and CSF volume (Hochwald et al, 1974;Wald et al, 1976;Orešković et al, 2002;Maraković et al, 2010;Jurjević et al, 2012). Because of this, it has been presumed that without significant obstruction or stenosis of the CSF system, all pathological processes in which an increase of CSF osmolarity (the osmotic load of CSF) takes place should lead to an increase in CSF volume, and consequently should cause hydrocephalus (Krishnamurthy et al, 2009;Orešković and Klarica 2010; what speaks in favor the most recent multiinstitutional studies of hydrocephalus as a consequence of hemispherectomy surgery for medically intractable epilepsy treatment (Lew et al, 2013).…”