Α. NOCICEPTIVE
• PHYSICAL
• VISCERAL
Β. NON-NOCICEPTIVE PAIN
• NEUROPATHIC
• SYMPATHETIC
Nociceptive is the pain induced by the stimulation of specific pain receptors that are called “nociceptors”. These receptors respond to stimuli, such as cold, hot, vibration, dilation and chemical stimuli released by cells that have been impaired.
Non nociceptive is the pain caused by dysfunction or impairment of the peripheral or central nervous system.
SOMATIC PAIN
This is pain originating from tissues, such as skin, muscles, bones, ligaments, and is often referred to as “myoskeletal pain”.
In somatic pain, body tissues have been impaired due to various reasons, such as injury, inflammation, pressure, hot or cold stimuli. Pain signals are identified by receptors reacting to pain, the so-called “nociceptors” (located in the skin, muscles, bones etc).
The pain is often acute, well-localised and reproduces with movement or pressure of the affected tissue or region. Drugs of choice for somatic pain treatment are paracetamol, non steroid anti-inflammatory drugs, mild and strong opioids.
VISCERAL PAIN
This is pain originating from visceral organs of body cavities which have undergone impairment and do not function normally. There are three main cavities in the human body:
1. Chest (heart and lungs)
2. Abdomen (liver, spleen, kidneys and intestine)
3. Pelvis (bladder, ovaries, uterus)
Pain is deep, not well localized, a tightening sensation that is continuous and colic-like. Pain usually reflects to the back or lower back depending on the level of damage. Drugs of choice are mild and strong opioids.
NEUROPATHIC PAIN
Neuropathic pain is due to impairment or dysfunction of the peripheral (nerves inbetween the skin and spinal cord) or the central nervous system (nerves inbetween spinal cord and brain). Nerves may be impaired because of injury (nerve sections or long-standing constant pressure), metabolic dysfunction ( e.g. diabetes mellitus), substance abuse (e.g. alcohol), viral infections (e.g. herpes zoster) or inflammation. Low back pain may also have neuropathic character, as in the case of nerves getting injured due to disc pressure of displacement.
The character of neuropathic pain is usually described as burning (causalgia) or stabbing. It can be either perforating, short-lasting and aggressive or silent and continuous. Sensation as if pinched by a needle or nail may occur to such an extent that even the slightest touching of the skin or simplest daily tasks may cause pain. Low back pain radiating to the lower extremity or even sole and toes accompanied with burning or numbness, could be a manifestation of lumbago with a neuropathic background.
Drugs of choice are antidepressants, antiepileptics, NMDA antagonists, mild and strong opioids and local lidocain and capsaicine patches.
SYMPATHETIC PAIN
Sympathetic pain is probably due to overactivity of the sympathetic system. It may occur following small injuries (e.g. sprain), fractures, soft tissue lesions etc. The mechanism is unknown. The well-known “reflex sympathetic dystrophy syndrome” has now been named into “complex regional pain syndrome” type I and type II (CRPS I, II)
Features of sympathetic pain are excessive oversensitivity of the affected area, allodynia, oedema, limitation of movement, disturbances of the autonomic nervous system, such as changes of temperature and color, trophic changes and sweating.
Drugs of choice are antidepressants, antiepileptics, NMDA antagonists, mild and strong opioids and a2 agonists.
