HYDROCEPHALUS - IS IMPAIRED CEREBROSPINAL-FLUID CIRCULATION ONLY ONE PROBLEM INVOLVED

Hydrocephalus is a complex disease of the brain as a whole, and imbala nce between cerebrospinal fluid (CSF) formation and absorption is not the sole mechanism involved in its pathophysiology. In the absence of a lymphatic system in the central nervous system, open communication b etween CSF and interstitial fluid (ISF) of the brain may contribute to maintaining homeostasis of the brain, keeping the microchemical envir onment in good balance. Membranes or cell layers separating CSF from I SF of the brain do not provide impermeability, so the CSF communicates with ISF across the ependymal layer and the pial surface of the brain . In contradiction of the classical theory, the CSF one may obtain at the cisterna magna, for instance, is different from the newly formed C SF out of the choroid plexus, because it has been modified by the free communication between CSF and ISF spaces as the CSF descends along th e neural axis. Free flow of water and some smaller molecules provides a bidirectional movement of water and other materials, and this must p lay an important role in brain volume control. The significance of thi s role should not be overlooked in regard to the pathophysiology of hy drocephalus.