Though there are several main categories of pain, health care professionals further define pain based on its source within the body. Pain that has a source external to the nerves that are detecting it is called nociceptive pain, and pain that arises from damage to the nervous system itself is called neuropathic pain or nerve-injury pain.
Nociceptive pain is the ordinary sensation that arises from injury or damage to some part of the body. Nerve endings at the injury or damaged site of the body are activated and send messages to the brain.
Neuropathic pain can occur as a result of injury or disease to the nerve tissue itself. It also may last longer and be more difficult to treat than nociceptive pain. Because the nerves are not functioning properly, they may transmit the sensation of pain to the brain even after the original injury has healed. Neuropathic is frequently described as a burning or shooting sensation and can lead to a heightened sensitivity to stimuli, even to the point of a gentle touch being interpreted as painful. Phantom limb pain, commonly reported by people who have had an amputation, falls into this category. The damage to the nerves themselves makes people feel pain in a part of their body that may not even exist anymore.
Neuropathic pain may, at times, seem to have no physical cause. In other words, there may be no injury to point to and say: this is the cause of the pain.