Nature of Chronic Pain for Practicing Physicians

Francis Bacon, the renowned English scholar of the 17th century, clearly characterized the role of theory in the understanding of natural phenomena. He made the following comparison for this purpose: "A hobbling cripple, taking the true road, may overtake a trotter if the latter runs an incorrect course. Actually, moreover, the faster the trotter runs, having once strayed from the path, the further behind it will be left by the cripple." This is exactly the situation that has developed at the present time in relation to teaching on chronic pain. Searching for the truth by "trial and error" has only partially elucidated the issue. This being the case, the main issue - the internal structure of the pain process, which must guide the medical logic of the physician to correct decision-making - remained "outside the frame".

Currently, a paradoxical situation has arisen in the study of pain, in which new knowledge in the fields of neurophysiology and neurochemistry of this phenomenon is scarcely reflected on the results of pain therapy. It was discovered that such knowledge is crucial primarily for specialists in the field of clinical pharmacology, who are engaged in the development of new and the improvement of existing opiate and non-opiate analgesic medications. As for the practice of medicine, new knowledge concerning the morphology and functional organization of pain sensitivity conductors was demanded exclusively by neurosurgeons, while physicians in other fields could not draw substantial benefit from this information for the successful treatment of chronic pain.

Until now, the possibility of achieving an analgesic effect by means of non-medicinal therapy in response to many types of pain pathologies has been extremely limited. The cause is not so much in lack of requisite knowledge of the problem, but rather in unilateral approach to its resolution, which leads to the loss of the clinical component in the understanding of conditions involved in the appearance and abatement of pain syndromes. There are many arguments to support the case that resolution of the problem of pain is not hindered by the lack of some undiscovered knowledge, but rather by the opposite problem – the lack of a complete analysis of the wealth of information obtained over the many years during which this problem has been studied. What is the difficulty?  

As we see it, the main difficulty lies in the problem of defining the initial theoretical principles that would offer the possibility of correctly interpreting the varied manifestations of chronic pain. It is possible to reach an understanding of these truths only if the nature of chronic pain is conceived of correctly. New knowledge in the fields of neurophysiology and neurochemistry of this phenomenon has not formed the basis of a full-fledged theory of chronic pain medicine. Most of this knowledge is descriptive and devoted to the establishment of the principles of the structure and connections of the conductors of pain sensitivity, or to the neurophysiologic mechanisms of action of numerous groups of analgesic agents. It is very difficult to understand the nature of pain from the perspectives of these investigations. Therefore, until now our notions of this phenomenon have been disconnected and fragmentary. And although the accumulation of data on this problem is continuing in clinical practice, it has been nearly impossible to make progress. This is true, above all, because of the great difficulty in systematizing pain phenomena and the lack of principles for their analysis. What is impeding the resolution of these questions?

The site presents a fundamental discovery in Pain Medicine. The discovery was a missing portion of the science of chronic pain – tissue factor, - lacking which this science has long been unable to distinguish itself as an independent clinical discipline…

Considering this, any case of pain in human body is viewed to be the manifestation of very different pain mechanisms, the nature of which is determined by structure of specific organs and tissues involved in the pathological process. The dependence of mechanisms of pain upon the tissue structure (the «Law of Tissue Specificity and Mutation of Mechanisms of Chronic Pain» by Y. F. Kamenev) became the basis for the creation of the «clinical alphabet of pain» by the authors of the site. Tissue mechanisms are multifaceted and sufficiently specific in terms of the formation of peripheral pain of specific forms (tissue, neurogenic, vascular and other origins). The alphabet equips physicians with knowledge essential for effective treatment of chronic pain. The optimal course of treatment is based on physician’s knowledge of concrete mechanisms of pain inherent in different organs and tissues constituting the pain origin.

Tissue mechanisms of pain are the key to solving the problems of pain. The understanding of the tissue specificity mechanisms of chronic pain and of the causes of its transition from one form to another (that is, its mutation mechanisms of pain) constituted the previously missing fundamental aspect of the science of chronic pain. The tissue determinacy of mechanisms of chronic pain orients specialists to the fact that pain arising from various tissue structures varies in terms of sensory modality, emotional tone of perception, conditions for its appearance and abatement. We do not doubt that as well the new understanding of the initial mechanisms of chronic pain (as applied to many biological structures) will be the basis of an advanced theory and practice for the treatment of various types of chronic pain.

In chronic pain, the nervous system is no longer a mere conductor of pain impulses; it is itself actively involved in the process of formation of pain sensations. A consequence of this is disturbance of the regulation of pain sensitivity of the peripheral tissues at the focus of injury. What is the mechanism of dysfunction of the nervous system?

According to modern conception, the path physiological foundation of chronic pain syndromes not associated with trauma are the formation and activity within the pain sensory system of generators of pathologically enhanced stimulation, an aggregate of hyperactive neurons forming originally at the level of ganglia and, subsequently, in absence of adequate treatment, at higher levels of the central nervous system, thereby substantially affecting the body’s pain sensitivity regulation. We identify the nervous nature of chronic pain according to type of pain, depending on which nervous system branch, somatic or vegetative, is involved in the perception of multimodal afferent information transmitted from the periphery.

Together, the tissue and the nervous factors create a pathological algesic system (PAS)., the liquidation of which, and subsequent elimination of pain syndromes, may only be possible by means of carefully selected medical procedures directed at each of the factors serial in sequence. A more complete and thoroughly discussed theory of generative and systemic mechanisms of pain is provided in the works of the Russian academician G.N.Kryazhanovskiy, who viewed this problem from the standpoint of regulation mechanism impairment and considered pain syndromes to be a manifestation of a dysregulation pathology. We interpreted of chronic pain as a combined pathology of peripheral tissues, the nervous system (somatic and vegetative) and the human emotional sphere. 

Considering this, the chronic nature of peripheral pain prevails in two cases: 1) during continuation in the periphery of effect caused by the source of nociceptive irritation; 2) appearance within the pain transmission system of the brain and spine of pathologically enhanced stimuli capable of performing self-sustaining activities without additional pain impulses from the periphery. In such cases, pain continues even after elimination of the pathological cause responsible for the initial pain sensation. The treatment of patients in the presence of chronic pain must consist of two independent components: 1) the treatment of the basic pathology that was the cause of the appearance of the pain syndrome, and 2) the treatment of chronic pain in accordance with concrete mechanisms of pain inherent in different organs and tissues.

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