How expectations influence pain

Direct and mediated effects of treatment context on low back pain outcome: a prospective cohort study

OBJECTIVES

Contextual components of treatment previously associated with patient outcomes include the environment, therapeutic relationship and expectancies. Questions remain about which components are most important, how they influence outcomes and comparative effects across treatment approaches. We aimed to identify significant and strong contextual predictors of patient outcomes, test for psychological mediators and compare effects across three treatment approaches.

DESIGN

Prospective cohort study with patient-reported and practitioner-reported questionnaire data (online or paper) collected at first consultation, 2 weeks and 3 months.

SETTING

Physiotherapy, osteopathy and acupuncture clinics throughout the UK.

PARTICIPANTS

166 practitioners (65 physiotherapists, 46 osteopaths, 55 acupuncturists) were recruited via their professional organisations. Practitioners recruited 960 adult patients seeking treatment for low back pain (LBP).

PRIMARY AND SECONDARY OUTCOMES

The primary outcome was back-related disability. Secondary outcomes were pain and well-being. Contextual components measured were: therapeutic alliance; patient satisfaction with appointment systems, access, facilities; patients' treatment beliefs including outcome expectancies; practitioners' attitudes to LBP and practitioners' patient-specific outcome expectancies. The hypothesised mediators measured were: patient self-efficacy for pain management; patient perceptions of LBP and psychosocial distress.

RESULTS

After controlling for baseline and potential confounders, statistically significant predictors of reduced back-related disability were: all three dimensions of stronger therapeutic alliance (goal, task and bond); higher patient satisfaction with appointment systems; reduced patient-perceived treatment credibility and increased practitioner-rated outcome expectancies. Therapeutic alliance over task (η_p²=0.10, 95% CI 0.07 to 0.14) and practitioner-rated outcome expectancies (η_p²=0.08, 95% CI 0.05 to 0.11) demonstrated the largest effect sizes. Patients' self-efficacy, LBP perceptions and psychosocial distress partially mediated these relationships. There were no interactions with treatment approach.

CONCLUSIONS

Enhancing contextual components in musculoskeletal healthcare could improve patient outcomes. Interventions should focus on helping practitioners and patients forge effective therapeutic alliances with strong affective bonds and agreement on treatment goals and how to achieve them.

Reward processing as a common diathesis for chronic pain and depression

Pain disorders and psychiatric illness are strongly comorbid, particularly in the context of Major Depressive Disorder (MDD). While these disorders account for a significant amount of global disability, the mechanisms of their overlap remain unclear. Understanding these mechanisms is of vital importance to developing prevention strategies and interventions that target both disorders. Of note, brain reward processing may be relevant to explaining how the comorbidity arises, given pain disorders and MDD can result in maladaptive reward responsivity that limits reward learning, appetitive approach behaviours and consummatory response. In this review, we discuss this research and explore the possibility of reward processing deficits as a common diathesis to explain the manifestation of pain disorders and MDD. Specifically, we hypothesize that contextual physical or psychological events (e.g. surgery, divorce) in the presence of a reward impairment diathesis worsens symptoms and results in a negative feedback loop that increases the chronicity and probability of developing the other disorder. We also highlight the implications for treatment and provide a framework for future research.

Patient Expectancy Does Not Predict Success or Failure of Thermal Neurotomy for Persistent Zygapophysial and Sacroiliac Joint Pain

OBJECTIVE

The placebo effect is important in determining the outcome of the treatment of pain for which expectancy and context are the main contributors. The variable success of thermal neurotomy spinal pain procedures is often seen as evidence of the placebo effect. Conversely, proponents of pain procedures explain poorer outcomes by technical procedure deficiencies, including inadequate diagnosis. This cohort study set out to determine whether patient expectancy is a contributing factor in the outcome of thermal neurotomy to the cervical, thoracic, and lumbar zygapophysial and sacroiliac joints.

DESIGN

This single-practitioner, single-site retrospective analysis of prospectively gathered cohort data of 549 patients evaluated the impact of patient preprocedure expectancy (rated on a simple 0-10 or 0-4 numerical rating scale) on outcomes in a large consecutive series of patients who had undergone thermal neurotomy treatment between 2009 and 2019. In addition, a portion of patients were asked to what extent they hoped for or desired a good outcome.

RESULTS

Successful pain relief (≥75% reduction from baseline) was not associated with a higher preprocedure expectancy than were failed procedures. Hope and desire demonstrated no impact on the positive or negative impact of the procedure.

CONCLUSIONS

Altogether, patient expectation of outcome, hope, and desire are not associated with the outcome of effective pain relief by thermal neurotomy that has been performed to the appropriate and commonly available technical standards. Further work is needed to determine the influence of patient expectation across a range of pain intervention modalities.

Intact pain modulation through manipulation of controllability and expectations in aging

BACKGROUND

Pain expectation and controllability can modulate pain processing. However, little is known about age-related effects on these cognitive factors involved in pain control. This study assessed age-related brain changes associated with pain expectation and controllability.

METHODS

17 healthy older adults (9 men; 65.65 ± 4.34 years) and 18 healthy younger adults (8 men; 20.56 ± 5.56 years) participated in the study. Pain evoked potentials and pain ratings were recorded while participants received painful electrical stimuli under two different conditions of pain controllability over the intensity of the stimulation (self-controlled vs. computer controlled) and two conditions of pain expectations (high vs. low pain).

RESULTS

Although the intensity of the painful stimulation was kept constant, all participants showed reduced pain perception in the controllable and low pain expectancy conditions. However, older participants showed reduced amplitudes of pain evoked potentials in the time window between 150 and 500 ms after stimulus onset as compared to younger participants. Moreover, younger participants showed greater negative amplitudes from 80 to 150 ms after stimulus onset for uncontrollable versus controllable pain.

CONCLUSIONS

These results suggest that although cognitive pain modulation is preserved during ageing, neural processing of pain is reduced in older adults.

SIGNIFICANCE

This research describes the impact of age on cognitive pain modulation evoked by the manipulation of pain controllability and pain expectations. Our findings constitute a first step in the understanding of the greater vulnerability of older individuals to chronic pain. Moreover, we show that older adults can benefit from cognitive pain control mechanisms to increase the efficacy of pain treatments.

How expectations of pain elicited by consciously and unconsciously perceived cues unfold over time

Expectation can shape the perception of pain within a fraction of time, but little is known about how perceived expectation unfolds over time and modulates pain perception. Here, we combine magnetoencephalography (MEG) and machine learning approaches to track the neural dynamics of expectations of pain in healthy participants with both sexes. We found that the expectation of pain, as conditioned by facial cues, can be decoded from MEG as early as 150 ms and up to 1100 ms after cue onset, but decoding expectation elicited by unconsciously perceived cues requires more time and decays faster compared to consciously perceived ones. Also, results from temporal generalization suggest that neural dynamics of decoding cue-based expectation were predominately sustained during cue presentation but transient after cue presentation. Finally, although decoding expectation elicited by consciously perceived cues were based on a series of time-restricted brain regions during cue presentation, decoding relied on the medial prefrontal cortex and anterior cingulate cortex after cue presentation for both consciously and unconsciously perceived cues. These findings reveal the conscious and unconscious processing of expectation during pain anticipation and may shed light on enhancing clinical care by demonstrating the impact of expectation cues.

Onset hyperalgesia and offset analgesia: Transient increases or decreases of noxious thermal stimulus intensity robustly modulate subsequent perceived pain intensity

Reported pain intensity depends not only on stimulus intensity but also on previously experienced pain. A painfully hot temperature applied to the skin evokes a lower subjective pain intensity if immediately preceded by a higher temperature, a phenomenon called offset analgesia. Previous work indicated that prior pain experience can also increase subsequent perceived pain intensity. Therefore, we examined whether a given noxious stimulus is experienced as more intense when it is preceded by an increase from a lower temperature. Using healthy volunteer subjects, we observed a disproportionate increase in pain intensity at a given stimulus intensity when this intensity is preceded by a rise from a lower intensity. This disproportionate increase is similar in magnitude to that of offset analgesia. We call this effect onset hyperalgesia. Control stimuli, in which a noxious temperature is held constant, demonstrate that onset hyperalgesia is distinct from receptor or central sensitization. The absolute magnitudes of offset analgesia and onset hyperalgesia correlate with each other but not with the noxious stimulus temperature. Finally, the magnitude of both offset analgesia and onset hyperalgesia depends on preceding temperature changes. Overall, this study demonstrates that the perceptual effect of a noxious thermal stimulus is influenced in a bidirectional manner depending upon both the intensity and direction of change of the immediately preceding thermal stimulus.

Virtual Reality Analgesia for Children With Large Severe Burn Wounds During Burn Wound Debridement

The objective of this study was to compare the effect of adjunctive virtual reality vs. standard analgesic pain medications during burn wound cleaning/debridement. Participants were predominantly Hispanic children aged 6-17 years of age, with large severe burn injuries (TBSA = 44%) reporting moderate or higher baseline pain during burn wound care. Using a randomized between-groups design, participants were randomly assigned to one of two groups, (a) the Control Group = pain medications only or (b) the VR Group = pain medications + virtual reality. A total of 50 children (88% Hispanic) with large severe burns (mean TBSA > 10%) received severe burn wound cleaning sessions. For the primary outcome measure of worst pain (intensity) on Study Day 1, using a between groups ANOVA, burn injured children in the group that received virtual reality during wound care showed significantly less pain intensity than the No VR control group, [mean worst pain ratings for the No VR group = 7.46 (SD = 2.93) vs. 5.54 (SD = 3.56), F (1,48) = 4.29, <0.05, MSE = 46.00]. Similarly, one of the secondary pain measures, "lowest pain during wound care" was significantly lower in the VR group, No VR = 4.29 (SD = 3.75) vs. 1.68 (2.04) for the VR group, F(147) = 9.29, < 0.005, MSE = 83.52 for Study Day 1. The other secondary pain measures showed the predicted pattern on Study Day 1, but were non-significant. Regarding whether VR reduced pain beyond Study Day 1, absolute change in pain intensity (analgesia = baseline pain minus the mean of the worst pain scores on Study days 1-10) was significantly greater for the VR group, F (148) = 4.88, p < 0.05, MSE = 34.26, partial eta squared = 0.09, but contrary to predictions, absolute change scores were non-significant for all secondary measures.

Case Report: Virtual Reality Analgesia in an Opioid Sparing Orthopedic Outpatient Clinic Setting: A Case Study

Immersive virtual reality is proving effective as a non-pharmacologic analgesic for a growing number of painful medical procedures. External fixator surgical pins provide adjunctive stability to a broken pelvic bone until the bones heal back together, then pins are removed. The purpose of the present case study was to measure for the first time, whether immersive virtual reality could be used to help reduce pain and anxiety during the orthopedic process of removing external fixator pins from a conscious patient in the orthopedic outpatient clinic, and whether it is feasible to use VR in this context. Using a within-subject within wound care design with treatment order randomized, the patient had his first ex-fix pin unscrewed and removed from his healing pelvic bone while he wore a VR helmet and explored an immersive snowy 3D computer generated world, adjunctive VR. He then had his second pin removed during no VR, standard of care pain medications. The patient reported having 43% less pain intensity, 67% less time spent thinking about pain, and 43% lower anxiety during VR vs. during No VR. In addition, the patient reported that his satisfaction with pain management was improved with the use of VR. Conducting simple orthopedic procedures using oral pain pills in an outpatient setting instead of anesthesia in the operating room greatly reduces the amount of opioids used, lowers medical costs and reduces rare but real risks of expensive complications from anesthesia including oversedation, death, and post-surgical dementia. These preliminary results suggest that immersive VR merits more attention as a potentially viable adjunctive non-pharmacologic form of treatment for acute pain and anxiety during medical procedures in the orthopedic outpatient clinic. Recent multi-billion dollar investments into R and D and mass production have made inexpensive immersive virtual reality products commercially available and cost effective for medical applications. We speculate that in the future, patients may be more willing to have minor surgery procedures in the outpatient clinic, with much lower opioid doses, while fully awake, if offered adjunctive virtual reality as a non-pharmacologic analgesic during the procedure. Additional research and development is recommended.

Hierarchical models of pain: Inference, information-seeking, and adaptive control

Computational models of pain consider how the brain processes nociceptive information and allow mapping neural circuits and networks to cognition and behaviour. To date, they have generally have assumed two largely independent processes: perceptual inference, typically modelled as an approximate Bayesian process, and action control, typically modelled as a reinforcement learning process. However, inference and control are intertwined in complex ways, challenging the clarity of this distinction. Here, we consider how they may comprise a parallel hierarchical architecture that combines inference, information-seeking, and adaptive value-based control. This sheds light on the complex neural architecture of the pain system, and takes us closer to understanding from where pain 'arises' in the brain.

A Deep Brain Stimulation Trial Period for Treating Chronic Pain

Early studies of deep brain stimulation (DBS) for various neurological disorders involved a temporary trial period where implanted electrodes were externalized, in which the electrical contacts exiting the patient's brain are connected to external stimulation equipment, so that stimulation efficacy could be determined before permanent implant. As the optimal brain target sites for various diseases (i.e., Parkinson's disease, essential tremor) became better established, such trial periods have fallen out of favor. However, deep brain stimulation trial periods are experiencing a modern resurgence for at least two reasons: (1) studies of newer indications such as depression or chronic pain aim to identify new targets and (2) a growing interest in adaptive DBS tools necessitates neurophysiological recordings, which are often done in the peri-surgical period. In this review, we consider the possible approaches, benefits, and risks of such inpatient trial periods with a specific focus on developing new DBS therapies for chronic pain.

Reward Enhances Pain Discrimination in Humans

The notion that reward inhibits pain is a well-supported observation in both humans and animals, allowing suppression of pain reflexes to acquired rewarding stimuli. However, a blanket inhibition of pain by reward would also impair pain discrimination. In contrast, early counterconditioning experiments implied that reward might actually spare pain discrimination. To test this hypothesis, we investigated whether discriminative performance was enhanced or inhibited by reward. We found in adult human volunteers (N = 25) that pain-based discriminative ability is actually enhanced by reward, especially when reward is directly contingent on discriminative performance. Drift-diffusion modeling shows that this relates to an augmentation of the underlying sensory signal strength and is not merely an effect of decision bias. This enhancement of sensory-discriminative pain-information processing suggests that whereas reward can promote reward-acquiring behavior by inhibition of pain in some circumstances, it can also facilitate important discriminative information of the sensory input when necessary.

Placebo effects in pain

Placebo effects influence symptom perceptions and treatment outcomes. Placebo effects can be explored in laboratory settings controlling for natural history and expectations. Such a mechanistic approach to neurological disorders has been implemented in the domain of chronic clinical pain and other neurological disorders. This article therefore focuses on definitions and historical notes related to placebo effects and mechanisms of placebo effects in chronic pain. Knowledge on mechanisms of placebo effects could inform current clinical practice for the treatment of neurological disorders by focusing on patients (and providers) expectations for outcome optimization.

Stimulus predictability moderates the withdrawal strategy in response to repetitive noxious stimulation in humans

Innate defensive behaviors such as reflexes are found across all species, constituting preprogrammed responses to external threats that are not anticipated. Previous studies indicated that the excitability of the reflex arcs like spinal nociceptive withdrawal reflex (NWR) pathways in humans are modulated by several cognitive factors. This study assesses how the predictability of a threat affects the biomechanical pattern of the withdrawal response, showing that distal and proximal muscles are differentially modulated by descending control.

Brain and pain: old assumptions and new science about chronic pain

The authors summarise the evolving understanding of the neuropsychophysiology of chronic pain, including the relevance of adverse childhood experiences in facilitating it and similarities between the central physiology of chronic pain and opioid addiction. Emerging understanding highlights the importance of dopamine-expressing GABAergic neurons in the nucleus accumbens and suggests that D1 expression is associated with a sense of pleasure and approach behaviour and D2 with a sense of punishment and behavioural inhibition. Regulation of D1 and D2 expression may be mediated by nigrostriatal and medial frontal striatal pathways within the increasingly understood brain as a ‘predictive’ organ. The distinction between the predictive brain and personal ‘expectations’ and the importance of the latter for clinical outcomes are emphasised. The relevance of findings for possible future psychopharmacological treatment avenues is also presented.

Virtual Reality Analgesia With Interactive Eye Tracking During Brief Thermal Pain Stimuli: A Randomized Controlled Trial (Crossover Design)

In light of growing concerns about opioid analgesics, developing new non-pharmacologic pain control techniques has become a high priority. Adjunctive virtual reality can help reduce acute pain during painful medical procedures. However, for some especially painful medical procedures such as burn wound cleaning, clinical researchers recommend that more distracting versions of virtual reality are needed, to further amplify the potency of virtual reality analgesia. The current study with healthy volunteers explores for the first time whether interacting with virtual objects in Virtual Reality (VR) via "hands free" eye-tracking technology integrated into the VR helmet makes VR more effective/powerful than non-interactive/passive VR (no eye-tracking) for reducing pain during brief thermal pain stimuli.

METHOD

Forty eight healthy volunteers participated in the main study. Using a within-subject design, each participant received one brief thermal pain stimulus during interactive eye tracked virtual reality, and each participant received another thermal pain stimulus during non-interactive VR (treatment order randomized). After each pain stimulus, participants provided subjective 0-10 ratings of cognitive, sensory and affective components of pain, and rated the amount of fun they had during the pain stimulus.

RESULTS

As predicted, interactive eye tracking increased the analgesic effectiveness of immersive virtual reality. Compared to the passive non-interactive VR condition, during the interactive eye tracked VR condition, participants reported significant reductions in worst pain (p < 0.001) and pain unpleasantness (p < 0.001). Participants reported a significantly stronger illusion of presence (p < 0.001), and significantly more fun in VR (p < 0.001) during the interactive condition compared to during passive VR. In summary, as predicted by our primary hypothesis, in the current laboratory acute pain analog study with healthy volunteers, increasing the immersiveness of the VR system via interactive eye tracking significantly increased how effectively VR reduced worst pain during a brief thermal pain stimulus. Although attention was not directly measured, the pattern of pain ratings, presence ratings, and fun ratings are consistent with an attentional mechanism for how VR reduces pain. Whether the current results generalize to clinical patient populations is another important topic for future research. Additional research and development is recommended.

Virtual reality hand therapy: A new tool for nonopioid analgesia for acute procedural pain, hand rehabilitation, and VR embodiment therapy for phantom limb pain

INTRODUCTION

Affordable virtual reality (VR) technology is now widely available. Billions of dollars are currently being invested into improving and mass producing VR and augmented reality products.

PURPOSE OF THE STUDY

The purpose of the present study is to explore the potential of immersive VR to make physical therapy/occupational therapy less painful, more fun, and to help motivate patients to cooperate with their hand therapist.

DISCUSSION

The following topics are covered: a) psychological influences on pain perception, b) the logic of how VR analgesia works, c) evidence for reduction of acute procedural pain during hand therapy, d) recent major advances in VR technology, and e) future directions-immersive VR embodiment therapy for phantom limb (chronic) pain.

CONCLUSION

VR hand therapy has potential for a wide range of patient populations needing hand therapy, including acute pain and potentially chronic pain patients. Being in VR helps reduce the patients' pain, making it less painful for patients to move their hand/fingers during hand therapy, and gamified VR can help motivate the patient to perform therapeutic hand exercises, and make hand therapy more fun. In addition, VR camera-based hand tracking technology may be used to help therapists monitor how well patients are doing their hand therapy exercises, and to quantify whether adherence to treatment increases long-term functionality. Additional research and development into using VR as a tool for hand therapist is recommended for both acute pain and persistent pain patient populations.

Distinguishing pain from nociception, salience, and arousal: How autonomic nervous system activity can improve neuroimaging tests of specificity

Pain is a subjective, multidimensional experience that is distinct from nociception. A large body of work has focused on whether pain processing is supported by specific, dedicated brain circuits. Despite advances in human neuroscience and neuroimaging analysis, dissociating acute pain from other sensations has been challenging since both pain and non-pain stimuli evoke salience and arousal responses throughout the body and in overlapping brain circuits. In this review, we discuss these challenges and propose that brain-body interactions in pain can be leveraged in order to improve tests for pain specificity. We review brain and bodily responses to pain and nociception and extant efforts toward identifying pain-specific brain networks. We propose that autonomic nervous system activity should be used as a surrogate measure of salience and arousal to improve these efforts and enable researchers to parse out pain-specific responses in the brain, and demonstrate the feasibility of this approach using example fMRI data from a thermal pain paradigm. This new approach will improve the accuracy and specificity of functional neuroimaging analyses and help to overcome current difficulties in assessing pain specific responses in the human brain.

Glial neuroimmune signaling in opioid reward

The opioid epidemic is a growing public concern affecting millions of people worldwide. Opioid-induced reward is the initial and key process leading to opioid abuse and addiction. Therefore, a better understanding of opioid reward may be helpful in developing a treatment for opioid addiction. Emerging evidence suggests that glial cells, particularly microglia and astrocytes, play an essential role in modulating opioid reward. Indeed, glial cells and their associated immune signaling actively regulate neural activity and plasticity, and directly modulate opioid-induced rewarding behaviors. In this review, we describe the neuroimmune mechanisms of how glial cells affect synaptic transmission and plasticity as well as how opioids can activate glial cells affecting the glial-neuronal interaction. Last, we summarize current attempts of applying glial modulators in treating opioid reward.

Mesocorticolimbic Pathways Encode Cue-Based Expectancy Effects on Pain

Expectation interacting with nociceptive input can shape the perception of pain. It has been suggested that reward-related expectations are associated with the activation of the ventral tegmental area (VTA), which projects to the striatum (e.g., nucleus accumbens [NAc]) and prefrontal cortex (e.g., rostral anterior cingulate cortex [rACC]). However, the role of these projection pathways in encoding expectancy effects on pain remains unclear. In this study, we leveraged a visual cue conditioning paradigm with a long pain anticipation period and collected magnetic resonance imaging (MRI) data from 30 healthy human subjects (14 females). At the within-subject level, whole-brain functional connectivity (FC) analyses showed that the mesocortical pathway (VTA-rACC FC) and the mesolimbic pathway (VTA-NAc FC) were enhanced with positive expectation but inhibited with negative expectation during pain anticipation period. Mediation analyses revealed that cue-based expectancy effects on pain were mainly mediated by the VTA-NAc FC, and structural equation modeling showed that VTA-based FC influenced pain perception by modulating pain-evoked brain responses. At the between-subject level, multivariate pattern analyses demonstrated that gray matter volumes in the VTA, NAc, and rACC were able to predict the magnitudes of conditioned pain responses associated with positive and/or negative expectations across subjects. Our results therefore advance the current understanding of how the reward system is linked to the interaction between expectation and pain. Furthermore, they provide precise functional and structural information on mesocorticolimibic pathways that encode within-subject and between-subject variability of expectancy effects on pain.SIGNIFICANCE STATEMENT Studies have suggested that reward-related expectation is associated with the activation of the VTA, which projects to the striatum and prefrontal cortex. However, the role of these projection pathways in encoding expectancy effects on pain remains unclear. Using multimodality MRI and a visual cue conditioning paradigm, we found that the functional connectivity and gray matter volumes in key regions (the VTA, NAc, and rostral ACC) within the mesocorticolimbic pathways encoded expectancy effects on pain. Our results advance the current understanding of how the reward system is linked to the interaction between expectation and pain, and provide precise functional and structural information on mesocorticolimbic pathways that encode expectancy effects on pain.

Pain: A Precision Signal for Reinforcement Learning and Control

Since noxious stimulation usually leads to the perception of pain, pain has traditionally been considered sensory nociception. But its variability and sensitivity to a broad array of cognitive and motivational factors have meant it is commonly viewed as inherently imprecise and intangibly subjective. However, the core function of pain is motivational-to direct both short- and long-term behavior away from harm. Here, we illustrate that a reinforcement learning model of pain offers a mechanistic understanding of how the brain supports this, illustrating the underlying computational architecture of the pain system. Importantly, it explains why pain is tuned by multiple factors and necessarily supported by a distributed network of brain regions, recasting pain as a precise and objectifiable control signal.

The neuroscience of vision and pain: evolution of two disciplines

Research in the neuroscience of pain perception and visual perception has taken contrasting paths. The contextual and the social aspects of pain judgements predisposed pain researchers to develop computational and functional accounts early, while vision researchers tended to simple localizationist or descriptive approaches first. Evolutionary thought was applied to distinct domains, such as game-theoretic approaches to cheater detection in pain research, versus vision scientists' studies of comparative visual ecologies. Both fields now contemplate current motor or decision-based accounts of perception, particularly predictive coding. Vision researchers do so without the benefit of earlier attention to social and motivational aspects of vision, while pain researchers lack a comparative behavioural ecology of pain, the normal incidence and utility of responses to tissue damage. Hybrid hypotheses arising from predictive coding as used in both domains are applied to some perplexing phenomena in pain perception to suggest future directions. The contingent and predictive interpretation of complex sensations, in such domains as 'runner's high', multiple cosmetic procedures, self-harm and circadian rhythms in pain sensitivity is one example. The second, in an evolutionary time frame, considers enhancement of primary perception and expression of pain in social species, when expressions of pain might reliably elicit useful help. This article is part of the Theo Murphy meeting issue 'Evolution of mechanisms and behaviour important for pain'.

When Expectancies Are Violated: A Functional Magnetic Resonance Imaging Study

Positive and negative expectancies drive behavioral and neurobiological placebo and nocebo effects, which in turn can have profound effects on patient improvement or worsening. However, expectations of events and outcomes are often not met in daily life and clinical practice. It is currently unknown how this affects placebo and nocebo effects. We have demonstrated that the violation of expectancies, such as when there is a discrepancy between what is expected and what is actually presented, reduces both placebo and nocebo effects while causing an extinction of placebo effects. The reduction of placebo and nocebo effects was paralleled by an activation of the left inferior parietal cortex, a brain region that redirects attention when discrepancies between sensory and cognitive events occur. Our findings highlight the importance of expectancy violation in shaping placebo and nocebo effects and open up new avenues for managing positive and negative expectations in clinical trials and practices.

Immersive Virtual Reality as an Adjunctive Non-opioid Analgesic for Pre-dominantly Latin American Children With Large Severe Burn Wounds During Burn Wound Cleaning in the Intensive Care Unit: A Pilot Study

Background/Aim: Using a within-subjects, within-wound care design, this pilot study tested for the first time, whether immersive virtual reality (VR) can serve as an adjunctive non-opioid analgesic for children with large severe burn wounds during burn wound cleaning in the ICU, in a regional burn center in the United States, between 2014–2016.

Methods: Participants included 48 children from 6 years old to 17 years of age with >10% TBSA burn injuries reporting moderate or higher worst pain during no VR on Day 1. Forty-four of the 48 children were from developing Latin American countries. Patients played adjunctive SnowWorld, an interactive 3D snowy canyon in virtual reality during some portions of wound care, vs. No VR during comparable portions of the same wound care session (initial treatment condition randomized). Using Graphic Rating scales, children's worst pain ratings during “No VR” (treatment as usual pain medications) vs. their worst pain during “Yes VR” was measured during at least 1 day of wound care, and was measured for up to 10 study days the patient used VR.

Results: VR significantly reduced children's “worst pain” ratings during burn wound cleaning procedures in the ICU on Day 1. Worst pain during No VR = 8.52 (SD = 1.75) vs. during Yes VR = 5.10 (SD = 3.27), t₍₄₇₎ = 7.11, p < 0.001, SD = 3.33, CI = 2.45–4.38, Cohen's d = 1.03 (indicating large effect size). Patients continued to report the predicted pattern of lower pain and more fun during VR, during multiple sessions.

Conclusion: Immersive virtual reality can help reduce the pain of children with large severe burn wounds during burn wound cleaning in the Intensive Care Unit. Additional research and development is recommended.

Placebo and nocebo response magnitude on temporomandibular disorder-related pain: A systematic review and meta-analysis

OBJECTIVES

The aim of this systematic review (SR) was to answer the following question: "In adult patients with temporomandibular disorder (TMD)-related pain, what is the placebo or nocebo effect of different therapies?"

METHODS

A SR was performed with randomised clinical placebo-controlled trials on diagnosed painful TMD studies from five main databases and from three grey literature. Studies included must have sample older than 18 years, with painful TMD, which diagnosis was done by Research Diagnostic Criteria (RDC/TMD) or Diagnostic Criteria (DC/TMD).

RESULTS

Out of 770 articles obtained, 42 met the inclusion criteria for qualitative and 26 for quantitative analysis. Meta-analysis indicated mean variation on pain intensity for placebo therapy was higher on laser acupuncture with 45.5 mm point reduction, followed by avocado soya bean extract with 36 mm and amitriptyline 25 mg with 25.2 mm. Laser showed a 29% of placebo effect, as well medicine with 19% and other therapies with 26%. Possible nocebo effect of 8% pain increase was found for intra-articular injection of Ultracain.

CONCLUSIONS

Based on the available data, the placebo response could play a major effect on TMD pain management and may be responsible from 10% to 75% of pain relief. Laser acupuncture, avocado soya bean and amitriptyline promoted the higher placebo effect. Possible nocebo effect was found only for Ultracain injection with 8%.

CLINICAL RELEVANCE

Clinicians could apply such evidence to optimise pain management and judgement about treatment efficacy, and researches may find it useful when designing their investigations.

The Landscape of Chronic Pain: Broader Perspectives

Chronic pain is a global health concern. This special issue on matters related to chronic pain aims to draw on research and scholarly discourse from an eclectic mix of areas and perspectives. The purpose of this non-systematic topical review is to précis an assortment of contemporary topics related to chronic pain and its management to nurture debate about research, practice and health care policy. The review discusses the phenomenon of pain, the struggle that patients have trying to legitimize their pain to others, the utility of the acute-chronic dichotomy, and the burden of chronic pain on society. The review describes the introduction of chronic primary pain in the World Health Organization's International Classification of Disease, 11th Revision and discusses the importance of biopsychosocial approaches to manage pain, the consequences of overprescribing and shifts in service delivery in primary care settings. The second half of the review explores pain perception as a multisensory perceptual inference discussing how contexts, predictions and expectations contribute to the malleability of somatosensations including pain, and how this knowledge can inform the development of therapies and strategies to alleviate pain. Finally, the review explores chronic pain through an evolutionary lens by comparing modern urban lifestyles with genetic heritage that encodes physiology adapted to live in the Paleolithic era. I speculate that modern urban lifestyles may be painogenic in nature, worsening chronic pain in individuals and burdening society at the population level.

Virtual Reality Analgesia During Venipuncture in Pediatric Patients With Onco-Hematological Diseases

Background: Venipuncture is described by children as one of the most painful and frightening medical procedures. Objective: To evaluate the effectiveness of Virtual Reality (VR) as a distraction technique to help control pain in children and adolescents undergoing venipuncture. Methods: Using a within-subjects design, fifteen patients (mean age 10.92, SD = 2.64) suffering from oncological or hematological diseases received one venipuncture with "No VR" and one venipuncture with "Yes VR" on two separate days (treatment order randomized). "Time spent thinking about pain", "Pain Unpleasantness", "Worst pain" the quality of VR experience, fun during the venipuncture and nausea were measured. Results: During VR, patients reported significant reductions in "Time spent thinking about pain," "Pain unpleasantness," and "Worst pain". Patients also reported significantly more fun during VR, and reported a "Strong sense of going inside the computer-generated world" during VR. No side effects were reported. Conclusion: VR can be considered an effective distraction technique for children and adolescents' pain management during venipuncture. Moreover, VR may elicit positive emotions, more than traditional distraction techniques. This could help patients cope with venipuncture in a non-stressful manner. Additional research and development is needed.