CSF anatomy with emphasis on relations to nasal cavity and labyrinthine fluids

Cerebrospinal fluid, occupying the subarachnoid space, is elaborated in an active process by the choroid plexus. It supports the brain and spinal cord and acts in lieu of a lymphatic system for central nervous tissue. Whether or not absorption of CSF into dural venous sinuses is an active or passive process is still controversial. A very thin layer of bone separates the posterior ethmoid air sinus from the subarachnoid space. There appears to be potential in man for flow of cerebrospinal fluid into the perilymphatic space of the inner ear, but it seldom occurs.