engleski

Measurement of cerebrospinal fluid formation and absorption by ventriculo-cisternal perfusion: what is really measured?

The generally accepted hypothesis on cerebrospinal fluid (CSF) hydrodynamics suggests that CSF is actively formed mainly by choroid plexuses, circulates unidirectionally along the brain ventricles and subarachnoid space, and is passively absorbed mainly into the dural venous sinuses. CSF formation rate (Vf) has been extensively studied by the ventriculo-cisternal perfusion technique, the results of which have been used as the key evidence for confirmation of this hypothesis. This method and the equation for the calculation of Vf have been established on the basis of the assumption that the dilution of the indicator substance is a consequence of a newly formed CSF, ie, that a higher CSF formation rate will result in a higher degree of dilution of the indicator substance. However, it has been experimentally shown that the indicator substance dilution inside the CSF system does not occur because of a “newly formed” CSF, but it is a consequence of a number of other factors (departure of substances into the surrounding tissue, passing around the collecting cannula into the cortical and spinal subarachnoid space, departure into the contralateral ventricle, etc). Using this technique it is possible to “calculate” the CSF formation even in dead animals, in an in vitro model, and in any other part of the CSF system outside the ventricles that is being perfused. Therefore, this method is indirect and any dilution of the indicator substance in the perfusate caused by other reasons would result in questionable and often contradictory conclusions regarding CSF formation rates.

arachnoid villi; cerebrospinal fluid; cerebrospinal fluid hydrodynamics; cerebrospinal fluid physiology; choroid plexus; classical hypothesis of cerebrospinal fluid hydrodynamics; hydrocephalus

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