Carefully :) Lp is typically performed in the office. You will lie on your side curled up into a tight ball. After sterilizing the area, local anesthetic is injected into the skin at the small of the back, and then a spinal needle is advanced between the vertebrae into the spinal canal. Once in the canal, the fluid pressure is measured and fluid is removed for analysis. Total time is typically 20 mins.
Use of needle. A special needle is employed and the test can be done with/without fluoroscopic viewing, by inserting the needle just below the spinal cord ending in the lower back area after local instillation of anesthetic. Fluid is withdrawn, spinal fluid pressures are measured, and results send to lab for various tests. Best to stay flat subsequently to avoid post-spinal headache, but usually quite safe.