Volume 22, Issue 4

Increasing evidence suggests an association between gene expression and clinical pain. Epigenetic modifications are the main modulators of gene expression or protein translation in response to environmental stimuli and pathophysiological conditions. Preclinical and clinical studies indicate that epigenetic modifications could also impact the development of pain, the transition from acute to chronic pain, and the maintenance hereof.

Emotions are allostatic processes that transform the relationship between the environment and the desired bodily states into behaviour supporting homeostasis and well-being. Central emotion circuits are thus tightly coupled with the visceral signaling pathways and the autonomic nervous system (ANS). Although ANS activity patterns are not always emotion-specific, self-reported bodily sensations and pattern recognition analysis of functional magnetic resonance imaging data suggest discrete bodily and neural basis of emotions. The advent of total-body positron emission tomography (PET) systems allows simultaneous measurement of the central and peripheral axis of the emotional response. This provides a unique opportunity for quantifying the systems-level biology of the human emotion circuits.

Quantitative sensory testing (QST) has been optimized to diagnose in particular small fiber neuropathy and has been successfully used for decades. “Sensory phenotypes” have been derived from the QST data in an attempt to stratify patients with chronic pain and to gain mechanistic insights. However, studies consistently show that there is no difference in sensory phenotypes between neuropathy patients with and without pain and no successful stratification has been shown using the current version of “sensory phenotypes”. Thus, after falsification of the initial hypothesis it is time to focus on more promising approaches.

Currently available treatments for neuropathic pain fail in roughly half of the patients – and it is impossible to predict which treatments will help patients. Stratification of neuropathic pain patients is needed, and sensory profiling has so far been the most promising approach: it has been shown to be responsive to treatment, linked to potential mechanisms, and, most importantly, predictive of treatment success. Despite a number of limitations, it is the currently most promising stratification tool and should be refined rather than disregarded.

Objectives Chronic pain is common following cancer treatment. This is a brief discussion of pain assessment after cancer treatment. Methods Summary of a lecure for the SASP (Scandinavian Journal of Pain) annual meeting 2022. Results Assessment of pain involves identifying the presence of pain, its underlying cause, its impact as well as underlying mechanisms. Conclusions Detailed pain assessment is important for the clinic and for epidemiological and mechanistic studies as well as pain treatment studies.

Our current understanding of central nervous system mechanisms supporting the experience of pain remains remarkably limited and produces substantial challenges when seeking to better diagnose and treat chronic pain. A new conceptual framework – The Distributed Nociceptive System – emphasizes system-level aspects of nociceptive processing by incorporating population coding and distributed process. The Distributed Nociceptive System provides a structure for understanding complex spatial aspects of chronic pain and provides a clear rationale for the further development of multi-disciplinary treatments for chronic pain.

Similar to the purpose of an infographic, visualizing spatial and qualitative sensations on a body chart is a fast and digestible method for communicating complex information and experiences. Further, digitizing these body charts into an interactive medium creates unprecedented opportunities for collecting extensive data. Moreover, applying simple rule-based algorithms or more advanced machine learning approaches to these charts catapults the quantification and spatiotemporal relations of pain and qualitative pain sensations into a new field ripe for pioneering discoveries.

The transition from a healthy to a persistent severe pain state following otherwise successful elective surgery is a feared complication. Groin hernia repair, previously considered minor surgery, is a standard surgical procedure annually performed on 2,000 individuals per one million residents. A trajectory into persistent severe pain is, unfortunately, seen in 2–4%, severely impeding physical and psychosocial daily functions.