Enigma of cerebrospinal fluid dynamics

Cerebrospinal fluid (CSF) is a major part of the central ner-vous system (CNS) extracellular fluid, and fine regulation of its composition is vital to the brain’s health. Although CSF dynamics has been studied for an entire century, many of its aspects are still insufficiently understood. Today there are two hypotheses (1,2) on CSF physiology: a) traditional hy-pothesis and b) microcirculatory/microvessel hypothesis. According to the traditional hypothesis, CSF is formed inside the brain ventricles, mostly by secretion from the choroid plexuses, and it circulates along the ventricles and subarachnoid space to be absorbed across the arachnoid villi into the dural venous sinuses, and/or viacranial and spi-nal nerves paraneural sheaths into the lymphatic system. Since substance exchange occurs between the CNS extra-cellular interstitial fluid (ISF) and CSF, it is assumed that CS