Pain medicine basics: Overview

Neuromodulation: Technology at the Neural Interface is the preeminent journal in the area of neuromodulation, providing our readership with the state of the art clinical, translational and basic science research in our field and representing the needs of the broad neuromodulation community. For clinicians, engineers, scientists and members of the biotechnology industry alike, Neuromodulation provides timely and rigorously peer reviewed articles on the technology, science and clinical application of devices that interface with the nervous system to treat disease and improve function. Neuromodulation covers an ever expanding field including pain, headache, movement disorders, spasticity, paralysis, psychiatric disorders, epilepsy, sensory deprivation, gastric dysfunction, obesity and incontinence.

Regional Anesthesia & Pain Medicine, the official publication of the American Society of Regional Anesthesia and Pain Medicine (ASRA Pain Medicine), is a monthly journal that publishes peer-reviewed scientific and clinical studies to advance the understanding and clinical application of regional techniques for surgical anesthesia and postoperative analgesia. Coverage includes intraoperative regional techniques, perioperative pain, chronic pain, obstetric anesthesia, paediatric anesthesia, outcome studies, and complications.

Abstract
Research on social disparities in pain and pain treatment has grown substantially in recent decades, as reflected in a growing number of review articles on these topics. This scoping review of reviews provides a macrolevel overview of scholarship in this area by examining what specific topics and findings have been presented in published reviews. We searched CINAHL, Cochrane Database of Systematic Reviews, Embase, PsycINFO, PubMed, and Web of Science for English-language, peer-reviewed review articles, qualitative or quantitative, that aimed to characterize or explain pain-related differences or inequities across social groups. Of 4432 unique records screened, 397 articles, published over a 56-year period, were included. For each, we documented (1) axes of social difference studied (eg, sex/gender, race/ethnicity), (2) pain-related outcomes (eg, chronic pain prevalence), (3) broad findings, (4) types of mechanisms proposed, and (5) policy or practice recommendations. Findings reveal a sharp increase in the number of published review articles on pain-related disparities since approximately the year 2000. The most commonly studied social dimension was sex/gender, followed by race/ethnicity and age. Studies examining disparities by socioeconomic status, geography, or other categories were rarer. While most findings showed disadvantaged social groups to have worse pain outcomes, there were intriguing exceptions. Biological, psychological, and sociocultural mechanisms were considered much more frequently than sociostructural (macrolevel) ones. Policy/practice recommendations were typically individual-level behavioral suggestions for providers or patients. We identify high-priority areas for future research, including greater attention to lower-income countries, chronic pain prevention, and macrolevel drivers of pain disparities.

Abstract
The perception of pain and ability to cope with it varies widely amongst people, which in part could be due to the presence of inhibitory (antinociceptive) or facilitatory (pronociceptive) effects in conditioned pain modulation (CPM). This study examined whether individual differences in CPM reflect functional connectivity (FC) strengths within nodes of the descending antinociceptive pathway (DAP). A heat-based CPM paradigm and resting-state functional magnetic resonance imaging (rs-fMRI) were used to test the hypothesis that an individual's capacity to exhibit inhibitory CPM (changes in test stimuli [TS] pain due to a conditioning stimulus [CS]) reflects FC of the subgenual anterior cingulate cortex (sgACC), periaqueductal gray (PAG), and rostral ventromedial medulla (RVM). A total of 151 healthy participants (72 men, 79 women) underwent CPM testing and rs-fMRI. Three types of CPM were identified based on the effect of the CS on TS pain: (1) Antinociception: CS reduced TS pain in 45% of participants, (2) No-CPM: CS did not change TS pain in 15% of participants, and (3) Pronociception: CS increased TS pain in 40% of participants. Only the Antinociceptive subgroup exhibited FC between the left sgACC and PAG, right sgACC and PAG, and RVM and PAG. Furthermore, only the Antinociceptive subgroup exhibited a correlation of both left and right sgACC-RVM FC (medium effect sizes) with CPM effect magnitude. Women, compared with men were more likely to be categorized as pronociceptive. These data support the proposition that FC of the DAP reflects or contributes to inhibitory CPM.