what is cerebrospinal fluid

Cerebrospinal fluid (CSF) is a clear, colourless body fluid found in the brain and spinal cord. It is produced by the specialised ependymal cells in the choroid plexuses of the ventricles of the brain, and absorbed in the arachnoid granulations. There is about 125mL of CSF at any one time, and about 500 mL is generated every day. CSF acts as a cushion or buffer for the brain, providing basic mechanical and immunological protection to the brain inside the skull. CSF also serves a vital function in cerebral autoregulation of cerebral blood flow.

CSF occupies the subarachnoid space (between the arachnoid mater and the pia mater) and the ventricular system around and inside the brain and spinal cord. It fills the ventricles of the brain, cisterns, and sulci, as well as the central canal of the spinal cord. There is also a connection from the subarachnoid space to the bony labyrinth of the inner ear via the perilymphatic duct where the perilymph is continuous with the cerebrospinal fluid.

A sample of CSF can be taken via lumbar puncture. This can reveal the intracranial pressure, as well as indicate diseases including infections of the brain or its surrounding meninges. Although noted by Hippocrates, it was only in the 18th century that Emanuel Swedenborg is credited with its rediscovery, and as late as 1914 that Harvey W. Cushing demonstrated CSF was secreted by the choroid plexus.