• • • • behavioural-based treatments for neck, shoulder, and back pain were confined to women. Two major hormonal systems influ-ence pain: sex steroids and hypotha-lamic-pituitary-adrenal (HPA) axis: CRH-ACTH (corticotropin-releas-ing hormone and adrenocortico-tropic hormone). A number of metabolic deficiencies cause sufficient impairment of mus-cle metabolism that could be a pri-mary causes of muscle pain. E.g. McArdle’s disease (myophosphoryl-ase deficiency that compromises glycolytic metabolism affecting type II fibres), carnitine palmitoyltrans-ferase deficiency (that affects mito-chondrial oxidative metabolism), or hypothyroidism (lack of energy in the muscle cell). Sympathetic dysfunction will cause abnormal metabolism of the neuro-muscular junction. Emerging data suggest that the function and health of the CNS is modulated by the interaction be-tween: 1) neurotransmitters, im-mune signalling, hormones, and neuropeptides produced in the gut. 2) the composition of the gut micro-biota, and, 3) integrity of the intes-tinal wall serving as a barrier to the external environment A vast topic, and an area of study in rapid development. Also, as pain is a brain event, all the factors discussed in numbers 1-9 need to be put in con-text in relation to the effects they may have in each particular brain neuro-matrix. Some relevant points: • Central neuropathic pain may occur associated to post-traumatic hyper-irritability syndromes, spinal cord injury, brain injury, stroke, multiple sclerosis, CNS tumours, or complex pain syndromes such as fibromyal-gia, where there is a disturbance of central pain processing (neurosen-sory amplification) but with a pe-ripheral sensitization component (including myofascial TPs). • The anterior cingulate cortex (ACC), a component of the limbic system, is related to many pain pro-cessing functions including antici-pation, anxiety, attention and the distress of pain. • The CNS can adapt to peripheral and central injury by the #10 CENTRAL NERVOUS SYS-TEM FACTORS: SENSITIZATION OF NOCICEPTIVE PATHWAYS AND CENTRAL SUPRASPINAL CENTERS WITH AUTONOMIC, PSYCHOEMOTIONAL, AND STRUCTURAL/NEUROPLASTIC CHANGES neuroplastic reorganization of cor-tical somatosensory somatotopic maps. Due to somatic sensory cor-tex anatomical and functional divi-sions, lesions of this region can leave a person capable of feeling pain but incapable of localizing it accurately. • Preliminary work indicates that in-terventions that alter peripheral nerve input by utilizing a correlated conditioning afferent stimulus, may trigger beneficial sensorimotor reor-ganization and improve clinical outcome in chronic pain. • The insula plays a role in the effec-tive processing of pain. In addition to processing nociceptive input, the insula also processes visceral sen-sory and motor activity. The insula has descending projections to the brainstem through which it exerts control over the autonomic nervous system as well as apparently regulat-ing the descending pain control systems. • Thalamic nuclei have widespread cortical efferents projecting to fron-tal, parietal and limbic regions throughout the cortical and subcor-tical pain systems. • A common spinal mechanism of sensitization: increased efficacy of synaptic transmission between pri-mary afferent and spinal neurons with the involvement of NMDA (N-methyl-D-aspartate) glutamate receptors, or activation of NK1 (neurokinin) receptors by substance P. • There has been a shift towards neu-ro-inflammation and hence glial cell activations specifically in the dorsal root ganglion and spinal cord as a mechanism possibly driving the transition to chronic pain. This has led to a focus on non-neuronal cells in the peripheral and central nerv-ous system. • The activation of microglial cells in response to nerve injury has been implicated in the development of neuropathic pain. After reviewing the 10 most com-mon contributors to pain syndromes, it is clear that the complexity of the pain experience requires clinicians to always take a multi-dimensional ap-proach to the analysis and treatment of these problems. July/August 2019 Canadian Chiropractor 19 www.canadianchiropractor.ca
Chiropractic + Naturopathic Doctor JulyAugust 2019: Page 19
