Transventricular and transpial absorption of cerebrospinal fluid into cerebral microvessels.

It is generally accepted that volume of cerebrospinal fluid (CSF) is secreted in brain ventricles and flows to subarachnoid space to be absorbed into dural venous sinuses or/and into lymphatics via perineural sheats of cranial nerves. Since 99% of CSF volume is water, in experiments on cats 3H-water was slowly infused into lateral ventricle and found that it does not flow to subarachnoid space but that it is rapidly absorbed transventricularly into periventricular capillaries. When 3H-water was infused in cortical subarachnoid space, it was absorbed locally into cerebral capillaries via pia mater. On the contrary, when macromolecule 3H-inulin is applied in CSF it is very slowly eliminated in bloodstream, and, with time, is carried by systolic-diastolic pulsations and mixing of CSF bidirectionally along CSF system. Thus, CSF volume (water) is absorbed rapidly into adjacent cerebral capillaries while inulin is distributed bidirectionally due to its long residence time in CSF Previously, the macromolecules have been used to study CSF volume hydrodynamics and with this misconception of CSF physiology arose.