What is pain?
It is an unpleasant sensation of an acute or chronic nature so differentiated by the factor of time (Cailliet, R. 1996).
Margo McCaffery (RN and pioneer of the field of pain management nursing) Defines pain as “whatever the experiencing person says it is, existing whenever and wherever the person say it does” (1979).
The Physiology of Pain
Pain is a warning signal that helps to protect the body from tissue damage. It originates within the skin, deeper soft tissues and organs. Neural pathways are stimulated (nociceptors or pain sensitive afferents). It is transmitted through the peripheral and Central Nervous Systems until its final destination at the sensory cortex. This is where the interpretation of pain occurs.
Nociceptors are the receptors for pain. They are free nerve endings found in every tissue of the body except the brain. Can occur in the skin, deeper soft tissues or the organs.
Stimulation required to activate these nociceptors can be thermal, mechanical or chemical. Irritation or injury to the tissues releases chemicals such as prostaglandins, kinins and potassium ions. These chemical mediators released or synthesized from trauma and inflammation which can be elicited by excessive stretching of a structure, prolonged muscular contractions, muscles spasms ischaemia (inadequate blood flow to an organ) or trauma.
The nerve fiber types that transmit the sensation of pain are small myelinated A-alpha fibers (sharp pain) and unmyelinated C fibers(duller and more enduring pain). It is the small diameter C fibres that are considered to be involved with chronic pain and are the fibers that respond to our touch. There are two types of peripheral nociceptor fibers, being fast and slow. The afferent nerves transmitting the sensation of pain are mostly (80%) unmyelinated nerves (C fibers). These fibers conduct slowly. It can take up to 3-5 sec to recognize the sensation of a burnt hand. Stimulation of these fibres can be described as chronic, throbbing, burning or aching.
Painful sensations are carried within specific tracts in the spinal cord, mainly spinothalamic tracts to the thalamus. Pain is also transmitted in the spinoreticulothalamic tracts synapsing with neurons of the reticular system, which may produce more diffuse and emotionally disturbing pains. Both tracts terminate at different sites within the thalamus, both regions projecting to different sensory cortical sites.
Chronic pain is an umbrella term for any type of persistent pain, from migraines to fibromyalgia, that lasts anywhere from several months to the rest of your life. The National Center for Health Statistics estimates that 76.5 million Americans suffer from it, with arthritis and back pain accounting for up to 60% of the cases. For some reason — researchers have not yet figured out why — most of the sufferers are women.
There are consequences of being in constant pain all the time, in terms of brain physiology. It interferes with your cognition, your attention. It causes emotional distress and depression. Pain is not just about how much it hurts. It can be described as an experience as opposed to a sensation. The sensation of pain is influenced by attention, expectancy, learning, anxiety, fear and distraction.
In chronic pain situations, the pain pursues even after the painful stimulus is removed and the acute pain pathway is hyperactive. This increased responsiveness to pain is caused by sensitization of inflammatory mediators such as bradykinin, prostaglandins and nerve growth factor.
Pain Regulation and Melzak and Wall’s pain-gate theory
Modulation of pain exists within the central nervous system. This theory suggests that pain sensation is altered by other afferent impulses (eg touch, pressure, vibration) which enter the spinal cord and have a ‘gating’ or inhibitory effect on impulse transmission. Therefore pain sensation may be modulated by other sensory modalities such as Osteopathy, massage, heat,TENS.
There are also intrinsic factors in the system that modulates pain.These are the naturally occurring opioid peptides(endorphins) that act as neurotransmitters and are widely distributed within the Central Nervous System.
How Osteopathic treatment can reduce or eliminate pain
Osteopaths can help to reduce pain by working directly or indirectly on the mechanoreceptors as the afferent nerves (nerves travelling up towards the brain via the spinal cord) can inhibit spinothalamic cell discharge. Therefore this can explain why we rub an injured area.
• Improves range of movement to the joints
• Stimulate or relax tensions found in the soft tissues.
• Enhances circulation.
• Decrease tissue oedema and congestion.
• Improves immune function.
• Improves respiration.
• Improves metabolism.
• Aids tissue repair.
• Helps digestion.
• Helps to normalise musculature.
• Sooths nerves.
*Picture sited from www.perioperativepain.com/Neuroanatomy_of_pain.htm (accessed 7.5.12)