 - Lumbar puncture spinal tap: Cerebrospinal fluid CSF is collected for analysis. For this procedure, 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. Some fluid is collected through the needle. Blood tests and a physical examination are done before the procedure to make sure it can be done as safely as possible. Patients may also be sedated to prevent any discomfort. 