Cerebrospinal Fluid (CSF) Fluid Analysis is a diagnostic test that examines the composition of cerebrospinal fluid, the clear fluid that surrounds the brain and spinal cord. The test is typically performed by collecting a sample of CSF through a procedure called a lumbar puncture (spinal tap). CSF analysis helps diagnose a variety of neurological conditions, including infections (such as meningitis or encephalitis), multiple sclerosis, bleeding (subarachnoid hemorrhage), and certain cancers (like brain or spinal cord tumors).