A lumbar puncture (also called a spinal tap) can be used to analyze the fluid in the spinal cord. This test is helpful for spinal tumor assessment and also for measuring whether certain cancers have spread to the brain. In this procedure, a special needle is inserted into the lower back spinal canal. This is the area around the spinal cord. The pressure in the spinal canal and brain can then be measured. A small amount of cerebral spinal fluid (CSF), the fluid in the brain and spinal cord, can be removed and sent for testing to determine if there is an infection or other problems.