A spinal puncture, or spinal tap, is a procedure in which cerebrospinal fluid (CSF) is removed through a needle in the back. Cerebrospinal fluid, sometimes also called spinal fluid, surrounds and protects the brain and the spinal cord. A sample of spinal fluid may be used to diagnose problems of the central nervous system, such as infections or tumors.
Sometimes, large amounts of spinal fluid may build up, a condition called hydrocephalus, leading to increased pressure on the brain. In such cases, removing excess spinal fluid can be therapeutic by relieving symptoms. Therapeutic spinal punctures may also be used to inject medication into the spinal cord to treat cancer or for anesthesia before surgery.
Most often, a spinal puncture is performed in the lower back or lumbar region, called a lumbar puncture. You will usually be positioned on your side while your doctor inserts a hollow needle into your back. A small sample of spinal fluid will be collected, or medication will be injected. If large amounts of spinal fluid need to be removed, a lumbar drain, or thin tube, may be inserted in place of the needle. Following the procedure, the needle or drain will be removed, and the puncture site is closed and covered with a bandage.