Introduction 

Cerebrospinal fluid is a clear liquid that flows within the central nervous system surrounding the brain and spinal cord. The CNS is surrounded by three layers of membranous tissue known as meninges. The innermost layer is known as the pia mater, the middle layer is the arachnoid mater and the outermost layer is the dura mater. The space which separates the pia mater from the arachnoid mater is known as the subarachnoid space. It is in the subarachnoid space where the CSF is located. The CSF also flows in the ventricular system, cisterns and sulci of the brain as well as the central canal of the spinal cord. The brain is completely surrounded by CSF so essentially floating. This significantly reduces the net weight of the brain whilst providing a cushioning effect in response to an impact on the skull. The primary function of the meninges and CSF is to protect the CNS from mechanical harm (such as head trauma) and immunological harm (such as viruses).

Para-sagittal MRI of the head image courtesy of Wikimedia Commons under the creative commons license. 

The cerebrospinal fluid is also important for the transport of neuroendocrine factors (hormones such as neuropeptides which are released in response to a neural stimulus) around the CNS. Proteins, glucose and cells which circulate within the CSF can be analyzed (via a lumbar puncture) to diagnose many neurological diseases such as meningitis or multiple sclerosis. A culture examination of the CSF may even reveal a microorganism responsible for an infection (for examples of this see the News section).

Banner image courtesy of Flickr under the creative commons license.