Cerebral spinal fluid is a clear fluid that provides nutrition to our central nervous system (CNS), which contains both the brain and the spinal cord. CSF analysis is used to examine disturbing conditions occurring inside our brain and spine. A sample of cerebrospinal fluid is taken for the test. This fluid is produced in the brain by a group of cells known as choroid plexus, which is then reabsorbed in the bloodstream and replaced every few hours. This test mainly looks for the signs of neurosyphilis in the CSF, which is usually aggravated by HIV or AIDS.