New findings and concepts on production and absorption of cerebrospinal fluid: reconsiderations and revisions of an unquestioningly accepted dogma of 100 years

Abstract

It has been recently pointed out that there are fallacies in the bulk flow theory, a dogmatic idea of cerebrospinal fluid (CSF) physiology, which assumes that CSF is produced by the choroid plexus and circulates unidirectionally from the ventricles to the subarachnoid space to be absorbed by the arachnoid villi in the parietal region. Therefore, CSF physiology now needs to be reconsidered. Since there is free exchange of water between the CSF and the brain interstitial fluid (ISF), when considering the dynamics of water in the brain, we should regard these two fluid compartments collectively as brain extracellular fluid. In this review, I discuss the contentious issues in the traditional theory of CSF physiology, and then introduce new understandings of the production and absorption of the brain extracellular fluid, such as the capillary theory asserting that brain ISF is produced and absorbed mainly at the cerebral capillaries, the brain lymphatic drainage pathway, and the non-existence of unidirectional CSF circulation.