Accepted

Chronic low back pain conditions are highly prevalent and constitute the leading cause of disability worldwide. The Analgesic, Anesthetic, and Addiction Clinical Trial Translations Innovations Opportunities and Networks (ACTTION) public-private partnership with the US Food and Drug Administration and the American Pain Society (APS), have combined to create the ACTTION-APS Pain Taxonomy (AAPT). The AAPT initiative convened a working group to develop diagnostic criteria for chronic low back pain. The working group identified three distinct low back pain conditions which result in a vast public health burden across the lifespan. This article focuses on: 1) the axial predominant syndrome of chronic musculoskeletal low back pain, 2) the lateralized, distally-radiating syndrome of chronic lumbosacral radicular pain 3) and neurogenic claudication associated with lumbar spinal stenosis. This classification of chronic low back pain is organized according to the AAPT multidimensional framework, specifically (1) core diagnostic criteria; (2) common features; (3) common medical and psychiatric comorbidities; (4) neurobiological, psychosocial, and functional consequences; and (5) putative neurobiological and psychosocial mechanisms, risk factors, and protective factors. Perspective: An evidence-based classification of chronic low back pain conditions was constructed for the AAPT initiative. This multidimensional diagnostic framework includes: (1) core diagnostic criteria; (2) common features; (3) medical and psychiatric comorbidities; (4) neurobiological, psychosocial, and functional consequences; and (5) putative neurobiological and psychosocial mechanisms, risk factors, and protective factors.

Experimental treatments for treating neuropathic pain include transcranial magnetic stimulation (TMS) and invasive electric motor cortex stimulation (iMCS) of the primary motor cortex (M1). Mechanisms of action of both methods, however, remain largely elusive. Within this paper, we focus on animal-based experiments in order to investigate the biological mechanisms that are involved in alleviating pain by use of TMS and/or iMCS. Therefore, this paper systematically reviewed the animal-based evidence on these mechanisms. Multiple online databases were systematically searched and retrieved articles were assessed using predefined inclusion and exclusion criteria. Twenty-three suitable articles were included; six on TMS and seventeen on iMCS. In general, iMCS and TMS were found to impact the primary motor cortex structure and function in animals. Furthermore, structural and functional changes within the thalamus, striatum, periaqueductal grey, rostral ventromedial medulla and dorsal horn were reported to occur. Although widespread, all areas in which structural and functional changes occurred after TMS and iMCS have been found to be interconnected anatomically. This could provide a rationale for future investigations of treating neuropathic pain by use of neuromodulation.

This review identified prospective cohort studies in the general population which showed incidence (23 papers) and risk factors (37 papers) for fibromyalgia and chronic widespread pain. Median incidence of physician diagnosed fibromyalgia in the general population was 4.3 per 1000 person-years [range = 0.33-18.8] but 14.0 [1.2 – 32.7] if medical illness was present. Median incidence of chronic widespread pain was 12.5 per 1000 person-years [7.2-81.6] but 67 per 1000 person years [14.8 to 124] for those with pre-existing pain. Risk factors included various childhood difficulties, female sex (except with pre-existing medical disorders) , older/middle age, smoking, high BMI, alcohol abstinence and pre-existing medical disorders in adulthood. The strongest associations were with sleep disorders, headaches and other pains, depression and illness behaviour.These data suggest strongly that there are many aetiological routes into fibromyalgia and future research could be enhanced by studying the underlying mechanisms relating to these risk factors.