A lumbar puncture — also known as a spinal tap — is used to collect the cerebrospinal fluid (CSF) surrounding the brain and spinal cord to detect disease, infection or injury. A lumbar puncture can tell doctors whether blood cancer cells are present in the sample. In addition, the pressure in the fluid surrounding the brain and spinal cord can be measured to provide other important information.
How Is It Done?
Generally, you will lie on your side with your knees pulled up toward your chest. It's important to stay in this position. The doctor carefully inserts a needle between two vertebrae in your lower back and then into the spinal canal. Your lower back is numbed with a local anesthetic, but you may feel some pressure. Sometimes doctors use fluoroscopy — a special x-ray technique — to help guide the needle into the proper position. Once the needle is properly positioned, spinal fluid pressure is measured and fluid is collected. It usually takes several minutes to get the sample of fluid. After removing the needle, the doctor places a bandage over the site and sends the fluid to a lab for analysis. Most spinal taps are done without any problem. In rare instances, patients report headaches, infection or bleeding.