The cerebrospinal fluid (CSF) is a body fluid that surrounds the brain and spinal cord within the arachnoid space. It has a volume of 120 to 250 ml in humans. Because the brain and spinal cord are virtually floating in CSF, this arrangement effectively protects the brain from traumatic effects.

CSF is formed by choroid plexuses - which are found in the brain ventricles. It circulates in the ventricles, the subarachnoid space, and the central canal of the spinal cord. It’s reabsorbed into the venous circulation through the arachnoid granulations.

Figure 1: Protection of the Central Nervous System