Causes of Chronic Pain

The perception of pain, or nociception, can be initiated by many means. It can occur in any diseased or traumatized tissue or organ that has nerve endings, or it can occur in the nerves themselves if they become damaged, irritated, or otherwise compromised.

General categories of where one might experience pain are:

• Cutaneous Pain
  Pain that originates in skin and is triggered by pain receptors just below surface of skin.
  
  
• Somatic Pain
  Pain that originates in bones, tendons, ligaments, nerves.
  
  
• Visceral Pain
  Pain that originates from internal organs ("viscera"). Pain that is "visceral” in nature is often "referred pain”. Referred pain refers to the situation when pain occurs in one place (i.e., heart) but is felt elsewhere (i.e., arm or hand).
  
  
• Phantom Limb Pain
  The odd state where an amputee continues to feel pain in the severed limb.
  
  
• Neuropathic Pain
  Pain that exists due to disease to the nerve tissue itself (e.g., myelination disease) or because of injury to a nerve. There might not be true pain, a smoking gun that one can point to, but the brain interprets it as being pain even though there is no real cause..