The term epidural is often short for epidural analgesia, a form of regional analgesia involving injection of drugs through a catheter placed into the epidural space. The injection can cause both a loss of sensation and a loss of pain, by blocking the transmission of signals through nerves in or near the spinal cord. The epidural space is the space inside the bony spinal canal but outside the membrane called the dura mater (sometimes called the "dura"). In contact with the inner surface of the dura is another membrane called the arachnoid mater ("arachnoid")...