Cerebrospinal fluid (CSF) is a clear fluid that surrounds the brain and spinal cord, cushioning and protecting these structures. It is produced by specialized cells in the brain and absorbed by blood vessels. Around 125 mL of CSF is present at any given time, with 500 mL produced daily. CSF analysis examines the CSF for signs of infection, bleeding, tumors, or other disorders. CSF is collected via lumbar puncture, then analyzed through chemical tests of glucose, protein, cell counts, and microbiological tests. Abnormal CSF results can indicate conditions like meningitis or neurosyphilis. CSF circulation and composition are also described.