In this technique, a very small catheter is placed in the back and is left in the space outside the spinal canal. Local anesthetic is dripped through the catheter and numbs the nerve roots as they enter the spine. Depending on the strength of the medication, an epidural can result in complete loss of all sensation and movement (from the chest down) or just reduce pain without any affect on movement "walking epidural."
This picture shows insertion of the epidural catheter through a needle into the back of an adult. Next, the needle is removed, leaving the catheter behind.