FEATURE PAIN MANAGEMENT BRAIN PAIN SUPPLY Common sources of neurological amplification: nociceptive fibres BY ALEJANDRO ELORRIAGA CLARACO A ccording to the Inter-national Association for the Study of Pain (IASP), pain is de-fined as “an unpleas-ant sensory and emo-tional experience associated with actual or potential tis-sue damage, or described in terms of such damage.” This definition contains two impor-tant agreements that comprise the foundation of understanding pain syndromes: First, that pain is a con-scious experience (i.e. psychological and therefore by definition a brain event), and second, that this brain event may or may not be associated with detectable tissue damage any-where in the body – although it is, also by definition, usually felt as if it was associated to tissue damage. Regarding this last point, and again according to IASP: “ …many people re-port pain in the absence of tissue damage or any likely pathophysiological cause; usually this happens for psychological reasons. There is usually no way to distin-guish their experience from that due to tissue damage if we take the subjective report. If they regard their experience as pain, and if they report it in the same ways as pain caused by tissue damage, it should be accepted as pain. This definition avoids tying pain to the stimulus. Activity induced in the nociceptor and nociceptive pathways by a noxious stimulus is not pain, which is always a psychological state, even though we may well appreciate that pain most often has a proximate physical cause. ” This paragraph suggests that psycho-logical is a realm separated from neu-rological, which is not compatible with contemporary science and neurophys-iology. Despite Descartes insistence in sep-arating reality into the res cognitas (consciousness, mind) and the res ex-tensa (matter, extension), and impreg-nating Western philosophy for more than 300 years with his intellectually appealing, but inaccurate concept of dualism, we know now that there is no such a thing as a mind separated from the matter responsible for the phenom-ena of consciousness and emotions (i.e. the human brain as well as the brain of other animals). At one time, dualism allowed for the separation of sciences and the non-physical realm (allowing scientists to conduct their research without fear of being considered heretics by reli-gious groups). Nowadays, dualism creates a serious problem for anybody approaching the study of mind-related events, such as the aforementioned pain syndromes. Interestingly, it was Descartes himself, in his famous 1637 Discours de la Méthode, who advo-cated the systematic doubting of knowledge, believing that sensed DR. ALEJANDRO ELORRIAGA CLARACO, is an international sports medicine consultant who has worked with hundreds of professional athletes and thousands of clients for over three decades. He has used his extensive clinical experience and research to become an innovative educator in the field of “pain with movement” disorders. You can find out more at mcmasteracupucture.com. 24 Canadian Chiropractor April 2019 perception and reason deceive us and therefore, man cannot have real knowl-edge of nature. The only thing that he believed could be certain was that he was doubtful, leading to his famous phrase Cogito ergo sum : I think therefore I am – which, in an updated version relevant to our subject today, it could read “I doubt, therefore I am scien-tific.” This may seem philosophical, but it is highly relevant to the topic because as I have just demonstrated, science in general and pain medicine in particular are still impregnated with the biases of past centuries, which in turn are con-ditioning the way we see and treat these pain problems in everyday clinical practice. To help clinicians with an updated approach to the management of pain problems, we must discuss the many possible contributors of a com-plex pain experience. Because pain is a brain event and all brain events are by nature the product of non-linear phys-iological processes, they are therefore complex. We seem to have failed so far in pain medicine because of the use of linear models, mostly structure based, that simply cannot explain the ob-served non-linear behaviour of these complex clinical problems. As a complex central nervous system by-product, where sensory, cognitive and emotional contributors are all part of the unpleasant experience, pain is deemed to have numerous physiologi-cal contributors that I’d like to call “pain contributors.” Obviously, the pathophysiology of pain contributors is complex and not fully understood, and www.canadianchiropractor.ca
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