A group of nerves, called a plexus or ganglion, can cause pain to a specific organ or body region. These nerves can be blocked with the injection of medication. The injection of this nerve-numbing substance is called a nerve block. There are two types of nerve blocks: therapeutic and diagnostic. Therapeutic nerve blocks are used to control acute pain. Diagnostic nerve blocks are used to determine sources of pain. These blocks typically contain an anesthetic with a known duration of relief. There are many different types of nerve blocks.