2.   Q. What is Pain?
     

       A. There Are Actually 3 Types of Pain

                        "The Greatest Evil is Physical Pain."

                                                                               -- St. Augustine

Medicine traditionally defines pain as the unpleasant sensations associated with either potential or actual tissue damage. In the case of potential tissue damage, this is readily recognized as the sensation felt instantly when a sharp knife is held against the skin. If the force and duration of the contact between the knife for example, and the skin, is light and brief, the pain experienced by the person is immediate, and likewise, immediately resolved once the knife is removed. No tissue has been damaged, and while certainly unpleasant, there are no consequences or ongoing problems as a result. These messages of pain are conveyed from the skin to the brain along specialized and well defined nerve pathways appropriately named 'pain fibers'. This phenomenon was described as early as 1664 by the French scientist and philosopher Rene' Descartes, who insightfully related how:

        "If for example fire comes near the foot, the minute particles of this fire….have the power

          to set in motion the spot of the skin…and by this means pulling upon the delicate thread 

         (nerve) which is attached to the spot on the skin, they open up at the same instance the

         pore (brain) against which the delicate thread ends, just as by pulling at the end of a rope  

        one makes to strike at the same instant a bell which hangs at the other end."

While neuroscience has illuminated many details of this simplified description of what occurs, the basic model has changed little since Descartes, and is still referred to today as the 'pain pathway'. It remains the prevailing scientific and popular model for pain, now termed 'nociception' (pain-sensing) by medical science. In terms of its temporal and distinct functional characteristics, it is best understood as 'immediate pain', or type 1 pain. Other specialized nerve fibers convey sensory information such as temperature, touch/pressure, and muscle stretch/joint position.

Now, if the force and/or duration of the knife/skin contact were sufficient to break the skin and cause a wound, well now there has been cellular damage. As a result of breaking open various cells in the skin, connective tissue, muscle and even bone if strong enough, a variety of potent chemicals are released into the surrounding tissues, initiating a sequence of events over time that medicine refers to as the 'inflammatory cascade'. These inflammatory chemicals stimulate different specialized nerve fibers called 'c fibers' that relay the message of pain to the brain, and are termed algogenic, or pain-causing. The classic physical features of this process are readily recognized as the triad of swelling, redness and warmth, as is typically seen in ankle sprains, muscle contusions/pulled hamstrings, ligament ruptures (ACL of the knee), or the soft tissues surrounding a bone fracture. So now we have the second type of pain, type 2, commonly known as inflammation, or 'acute pain'. Depending on how severe the wound is, as well as how competent the patient's immune system is, will determine how long (generally weeks) it takes for the body to heal the insult.

Types 1 & 2 pain, nociceptive and inflammatory pain, are well recognized and understood by medical science. Indeed, the definition of pain accepted by the I.A.S.P. (International Association for the Study of Pain), the world's leading scientific organization devoted to understanding pain is:

    "Pain is an unpleasant sensory and emotional experience associated with actual or potential  

     tissue damage, or described by the patient in terms of such damage."     (Italics added)

While this definition adequately covers Types 1 (potential tissue damage) & 2 (actual tissue damage) pain, there is another very important and common cause of pain that is NOT associated with 'actual or potential tissue damage', and that type of pain develops when the body's pain detecting system itself, the nerves, are damaged.

"What is deservedly suffered must be borne with calmness, but when the pain is unmerited, the grief is resistless."
                                                                    -- Ovid

Next, let us go back to the knife/skin examples but consider a slightly different scenario, indeed the most common and commonly overlooked scenario that causes chronic soft-tissue pain. Let us presume that instead of a knife, a spoon is being pushed against the soft-tissue, that is, something that is generally non-painful. Normally, the body interprets the stimulus as non-painful, which is what it is. What if, however, the nerve-muscle (neuromuscular) pathways themselves not well, and have become what is called 'super-sensitive'. Now, even when a non-painful stimulus (or even no stimulus) is presented to the soft tissues (skin, muscle, connective), these 'super-sensitive' pathways interpret the stimuli as painful. In this third type of pain, or type 3 pain, it is the body's sensory and motor system itself, that is the nerves, that are the problem. Thus Dr. Gunn termed this type 3 pain, 'neuro-pathic pain' ('nerve-sick pain'). Significantly, unlike types 1 and 2 pain, type 3 pain cannot self-correct by removing a noxious stimulus or healing a wound, and therefore remains until the sick nerves are treated, and therefore is of lasting duration, hence 'chronic pain'. Also significantly, while the symptoms that result from sick nerves can be managed with medication, medicine or surgery will not alleviate the underlying problem.

A nice analogy for type three neuropathic pain is the scenario of a newly installed home security system. Let us imagine that the system has not yet been properly adjusted, and so when a cat walks across the entrance to the home, the pressure sensors in the floorboards trigger the alarm, when they should properly only trigger the alarm when the weight of a human intruder causes them to fire. Similarly, the thermal sensors trigger the alarm when the first rays of sunrise hit the room, rather than triggering only with the warmth of a human intruder. The alarm system is too sensitive, i.e. 'super-sensitive'. Call the electrician!

SUMMARY OF TYPES 1-3 PAIN & THEIR TYPICAL BEHAVIORAL RESPONSES



The Most Common Cause of Neuropathic Pain is 'Spondylosis', or Spinal Degeneration

Due to the anatomy and structure of the nervous system, the peripheral nerves (as opposed to the brain or spinal cord which are part of the central nervous system and protected by the bones of the skull and spinal vertebrae) are especially vulnerable to mechanical trauma at the point where they originate from and branch off the spinal cord at each of 31 segmental levels, beginning in the cervical (neck) and down through the thoracic (mid-back) to the lumbar-sacral (low back) regions. These branch points are known as the nerve roots, and thus the term radiculo (root)-neuropathy is used to more precisely define this most common type of neuropathic pain and its associated soft-tissue (muscle/tendon/ligament) manifestations. It is most common because the gradual process of spinal deterioration and its associated degeneration of the spinal discs/joints over time from repeated insults is essentially a universal phenomenon. This process is called spondylosis, and is associated over time with the X-ray findings of bone spurs, disc space narrowing, cartilage damage and/or facet joint subluxation.

             "If we look over the history of science, there are very long periods when the uncritical

              acceptance of the established ideas was a real hindrance to the new."

                                                                                                                                     - Thomas Gold Sc.D.