Over 100 million of Americans and 1.5 billion people worldwide suffer some form of pain over the last 3 months and 23 million Americans suffer from chronic or prolonged pain daily. Many chronic pain sufferers have no definitive diagnosis to explain their pain. The health care cost for pain in the US is over $600 billion dollars. In the context of this book our failure to manage pain is also evident in trauma and injury cases.
There is a growing disconnect in the science of pain and our clinical management of pain. The American Academy of Pain Medicine has proposed categorizing pain on a neurobiologic basis as eudynia (acute or tissue damage pain), Greek for "good pain," or maldynia (chronic or destructive pain), Greek for "bad pain.” Genetics, biopsychosocial and other factors are now known to play a major role in the path from eudynia to maldynia. The mechanism of acute pain is not the same as the mechanism of chronic pain.
The nociceptive (pain) system is not just a system for the conduction of pain impulses from the periphery to the brain. We now know that plastic changes can take place in the periphery, the spinal cord and also in higher brain centers following injury or inflammation. These changes may increase the magnitude of the perceived pain and may contribute to the development of chronic pain syndromes. Swiss Med Wkly 2002;132:273– 278
There is good evidence that chronic pain is associated with changes in brain function. It is possible that these brain changes compound chronic pain and future agents may be able to prevent such complications. German J Psychiatry 2003; 6: 8-15.
Pain is a distinctive experience, with a wide range of influential factors in its progression. Predispositions for injury and illness, social influences, economic difficulties, psychological factors, and physiology all play important roles in the development and management of chronic pain. In addition to pain, patients often experience functional deficits including physical difficulties, psychological and emotional distress, poor coping skills, and kinesiophobia (fear of movement). The biopsychosocial model evaluates the integrated “whole person,” with both the mind and the body together as interconnected entities, recognizing biological, psychological, and social components of pain and illness. Genetic predispositions, variables such as stress can alter their phenotypic behavioral expression, and have lasting effects both behaviorally and psychosocially. The Biopsychosocial Model of the Assessment, Prevention, and Treatment of Chronic Pain, US Neurology, 2016; 12(2):98–104.
Your pain warning system is not just a system for the conduction of pain impulses from the periphery to the brain. Scientists now know that changes can take place in the receptors, nerves, the spinal cord and in the higher brain centers following injury, inflammation, continued use of the pain system, disuse of inhibiting factors and learned behaviors. These changes can increase the likelihood that pain is perceived and may contribute to the development of "chronic pain". Neuroplastic changes in structure and function are not only a consequence of chronic pain but are involved in the maintenance of pain symptoms. Therefore, "chronic pain" can in some cases be considered a separate disease, independent of the pathology that initially set off the pain warning system.
Pain is defined by the International Association for the Study of Pain as "an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage". The following points are important to understand about pain:
1. Pain may or may not involve tissue damage.
2. Our nervous system is plastic (constantly changing).
3. There is not always a relationship between tissue damage and pain perception.
4. Pain can now be classified by physiology; tissue damage pain (acute / eudynia ) and neuroplastic or destructive pain (chronic / maldynia ).
5. Genetics and biopsychosocial also play a role in all types of pain.
6. Mechanisms underlying chronic pain differ from those underlying acute pain.
