- Lumbar puncture (spinal tap): This procedure will be done during the last month before starting treatment and during the seventh month of treatment to examine immune changes that occur in the cerebrospinal fluid (CSF), which circulates through and surrounds the brain and spinal cord. A local anesthetic is given and a needle is inserted in the space between the bones in the lower back where the CSF circulates below the spinal cord. A small amount of fluid is collected through the needle.