A lumbar puncture is performed to extract the fluid that surrounds the brain and spinal cord called the cerebrospinal fluid. A sample of the cerebrospinal fluid is extracted so it can be analyzed to help detect diseases of the central nervous system. To detect: • Meningitis • Dementia • Subarachnoid hemorrhage • Myelitis • Leukemia • Reye syndrome • Demyelinating diseases • Headaches of unknown cause • Neurosyphilis • Encephalitis • Guillain-Barre syndrome • Bleeding in brain Lumbar puncture is also done for treatments such as injecting local anaesthesia, antibiotics, and cancer medications. Doing so allows the drug to enter the nervous system via the bloodstream. Lumbar puncture is also performed to measure the pressure of cerebrospinal fluid, inject dyes (myelography) and radioactive substances (cisternography) into cerebrospinal fluid to make diagnostic images of the fluid’s flow.