Lumbar puncture

During a lumbar puncture, the doctor inserts a needle between 2 of the bones that make up the spine. Then, they use the needle to collect a small sample of "cerebrospinal fluid" ("CSF") from around the spinal cord. The needle goes in below where the spinal cord is a solid cord, so it is unlikely to get injured by the needle.

Spinal anesthesia is done in a similar way. The doctor uses a needle to inject medicine into the CSF. This can be used to block pain, for example, during surgery or childbirth.