The autonomic nervous system (ANS) and the hypothalamic-pituitary-adrenal axis (HPA axis) have proven to be dysfunctional in a number of chronic pain conditions. Spinal manipulation is a therapeutic technique used by manual therapists that can have far-reaching neurophysiological effects. The autonomic nervous system has been linked to the modulation of these effects. The theory is proposed that spinal manipulation has the potential to be used as a tool to restore the balance of the autonomic nervous system. Anatomically, the ganglia of the sympathetic nervous system (NS) lie directly in front of the articulation of the ribs with their vertebrae in the thoracic spine. This could excite preganglionic sympathetic nerve cells during manipulation. Furthermore, thoracic spinal manipulation excites various mechanoreceptors. These stimuli travel via the dorsal horn in the spinal cord up to several regions of the brainstem (central nucleus of the amygdala (CeNa), paraventricular nucleus (PVN), periaqueductal gray (PAG), rostral ventrolateral medulla (RVM)). The periaqueductal gray, in particular, plays an important role. If excited by manipulation, it initiates a fight-or-flight response typical of the sympathetic NS. This activation is also associated with opioid-independent analgesia. CRH neurons (corticotropin-releasing hormone) present in the CeNa and PVN then modulate the response of the ANS and HPA axis. Therefore, it can be argued that spinal manipulation can also lead to a co-activation of both systems, namely the ANS and the endocrine system (HPA axis). The end products of these two systems (catecholamines and glucocorticoids) would then modulate the inflammatory response and tissue healing. Sympathetic activation of the PAG also has analgesic significance. The PAG is strongly connected to the hypothalamus and limbic forebrain structures, including the amygdala. The PAG projects into the RVM, which in turn sends its output to the dorsal horn. In summary, the PAG-RVM system is known as a central site of action for analgesics such as opioids, cyclooxygenase inhibitors, and cannabinoids. This explains the possible influence on pain perception in chronic pain patients. Since the autonomic nervous system and the HPA axis play an important role in many clinical pain syndromes, it is interesting that thoracic spinal manipulation may influence these two systems simultaneously. Because both systems are overactivated in these symptoms, thoracic spinal manipulation could be a good and safe method to restore the balance of the autonomic nervous system and thus also normalize the HPA axis. Consequently, thoracic spinal manipulation is a suitable means to treat problems characterized by ANS and HPA axis dysfunction.
Summary:
The autonomic nervous system (ANS) and the hypothalamic-pituitary-adrenal axis (HPA axis) have proven to be dysfunctional in a number of chronic pain conditions. Spinal manipulation is a therapeutic technique used by manual therapists that can have far-reaching neurophysiological effects. The autonomic nervous system has been linked to the modulation of these effects. The theory is proposed that spinal manipulation has the potential to be used as a tool to restore the balance of the autonomic nervous system. During manipulation, the brain receives stimuli from nerve fibers of the autonomic and somatic nervous systems and transmits them to specific regions in the brainstem. The periaqueductal gray (PAG), in particular, plays an important role. If excited by manipulation, it initiates a fight-or-flight response typical of the sympathetic NS. This activation is also associated with opioid-independent analgesia. CRH neurons (corticotropin-releasing hormone) present in the CeNa and PVN then modulate the response of the ANS and HPA axis. Therefore, it can be argued that spinal manipulation can also lead to a co-activation of both systems, namely the ANS and the endocrine system (HPA axis). Because both systems are overactivated in chronic pain, thoracic spinal manipulation could be a good and safe method to restore the balance of the autonomic nervous system and thus also normalize the HPA axis. Consequently, thoracic spinal manipulation is a suitable means to treat problems characterized by ANS and HPA axis dysfunction. Bibliography: Sampath K, Mani R et Al. Measurable changes in the neuro-endocrinal mechanism following spinal manipulation. Med. Hypotheses. 2015;85(6): 819-824.
