Hydrocortisone Differentially Affects Reinstatement of Pain-related Responses in Patients With Chronic Back Pain and Healthy Volunteers

Despite the crucial role of effective and sustained extinction of conditioned pain-related fear in cognitive-behavioral treatment approaches for chronic pain, experimental research on extinction memory retrieval in chronic pain remains scarce. In healthy populations, extinction efficacy of fear memory is affected by stress. Therefore, we investigated the effects of oral hydrocortisone administration on the reinstatement of pain-related associations in 57 patients with non-specific chronic back pain (CBP) and 59 healthy control (HC) participants in a differential pain-related conditioning paradigm within a placebo-controlled, randomized, and double-blind design. Participants' skin conductance responses indicate hydrocortisone-induced reinstatement effects in HCs but no observable reinstatement in HCs receiving placebo treatment. Interestingly, these effects were reversed in patients with CBP, that is, reinstatement responses were only observed in the placebo and not in the hydrocortisone group. Our findings corroborate previous evidence of stress-induced effects on extinction efficacy and reinstatement of fear memory in HCs, extending them into the pain context, and call for more research to clarify the role of stress in fear extinction and return of fear phenomena possibly contributing to treatment failure in chronic pain treatment. PERSPECTIVE: Opposing effects in HCs and patients with non-specific CBP may be associated with changes in the patients' stress systems. These findings could be of relevance to optimizing psychological, extinction-based treatment approaches.

Translating knowledge on placebo and nocebo effects into clinical practice

Introduction

Positive and negative treatment expectations are powerful modulators of health and treatment outcomes. A substantial part of treatment success is due to contextual factors modulating patient's expectations towards a treatment. Consequently, treatment expectations should be a target of therapeutic interventions themselves.

Objectives

This article highlights the neurobiological underpinnings of treatment expectations as well as strategies to modulate contextual factors to optimize treatment outcomes in daily clinical settings.

Methods

This clinical update aligns with the 2022 IASP Global Year Translating Pain Knowledge into Practice and selectively reviews the best available evidence and practice.

Results

The effects of treatment expectations, also known as placebo and nocebo effects, are observed in various clinical conditions and physiological systems. However, most of our knowledge comes from the field of pain, where expectation effects substantially contribute to overall analgesic treatment outcomes. Experimental placebo analgesia paradigms provide the best illustration of how analgesic effects can be attributed not only to a pharmacological or specific treatment, but instead are the result of the expectation towards the treatment. The impact of expectations on treatment outcome is highly variable between individuals, and the identification of factors predicting an individual's response has proven to be challenging. Further research is required to provide personalized treatment strategies for the daily clinical practice.

Conclusion

Patient's previous experiences and expectations are powerful modulators of treatment efficacy, tolerability, and adherence. By providing a comprehensive overview of recent advances in this field, this review offers valuable insights for clinicians and researchers seeking to improve patient-clinician interaction.

EFFects of Exposure and Cognitive behavioral Therapy for chronic BACK pain ("EFFECT-BACK"): study protocol for a randomized controlled trial

INTRODUCTION

Chronic back pain is a widespread medical condition associated with high socioeconomic costs and increasing prevalence. Despite the advanced implementation of multidisciplinary approaches, providing a satisfactory treatment offer for those affected is often not possible. Exposure therapy (EXP) promises to be an effective and economical form of treatment and in a previous pilot study showed to be superior to cognitive behavioral therapy (CBT) in reducing perceived limitations of movement. The current study aims to further compare the efficacy of both treatment methods and identify those patient groups that particularly benefit from EXP.

METHODS

The general objective of this randomized multicenter clinical trial (targeted N = 380) is to improve and expand the range of treatments available to patients with chronic back pain. As the primary objective of the study, two different psychological treatments (EXP and CBT) will be compared. The primary outcome measure is a clinically significant improvement in pain-related impairment, measured by the QPBDS, from baseline to 6-month follow-up. Secondary outcome measures are absolute changes and clinically significant improvements in variables coping, psychological flexibility, depressiveness, catastrophizing, exercise avoidance and fear of exercise, and intensity of pain. Participants are recruited in five psychological and medical centers in Germany and receive ten sessions of manualized therapy by trained licensed CBT therapists or clinical psychologists, who are currently in their post-gradual CBT training. Potential predictors of each treatment's efficacy will be explored with a focus on avoidance and coping behavior.

CONCLUSION

This study will be the first RCT to compare CBT and EXP in chronic back pain in a large sample, including patients from different care structures due to psychological and medical recruitment centers. By identifying and exploring potential predictors of symptom improvement in each treatment group, this study will contribute to enable a more individualized assignment to treatment modalities and thus improves the care situation for chronic back pain and helps to create a customized treatment program for subgroups of pain patients. If our findings confirm EXP to be an efficacious and efficient treatment concept, it should gain more attention and be further disseminated.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05294081. Registered on 02 March 2022.

Open-label placebo treatment does not enhance cognitive abilities in healthy volunteers

The use of so-called 'smart drugs' such as modafinil to improve cognitive performance has recently attracted considerable attention. However, their side effects have limited user enthusiasm. Open-label placebo (OLP) treatment, i.e., inert treatments that are openly disclosed to individuals as having no active pharmacological ingredient, has been shown to improve various medical symptoms and conditions, including those related to cognitive performance. OLP treatment could therefore be an exciting alternative to pharmacological cognitive enhancers. Here, we used a randomized-controlled design to investigate the effect of a 21-day OLP treatment on several sub-domains of cognitive performance in N = 78 healthy volunteers. Subjective and objective measures of cognitive performance as well as different measures of well-being were obtained before and after the treatment period. Using a combination of classic Frequentist and Bayesian analysis approaches showed no additional benefit from OLP treatment in any of the subjective or objective measures of cognitive performance. Our study thus highlights possible limitations of OLP treatment in boosting cognitive performance in healthy volunteers. These findings are discussed in the light of expectancy-value considerations that may determine OLP efficacy.

Brain morphology predicts individual sensitivity to pain: a multicenter machine learning approach

ABSTRACT

Sensitivity to pain shows a remarkable interindividual variance that has been reported to both forecast and accompany various clinical pain conditions. Although pain thresholds have been reported to be associated to brain morphology, it is still unclear how well these findings replicate in independent data and whether they are powerful enough to provide reliable pain sensitivity predictions on the individual level. In this study, we constructed a predictive model of pain sensitivity (as measured with pain thresholds) using structural magnetic resonance imaging-based cortical thickness data from a multicentre data set (3 centres and 131 healthy participants). Cross-validated estimates revealed a statistically significant and clinically relevant predictive performance (Pearson r = 0.36, P < 0.0002, R2 = 0.13). The predictions were found to be specific to physical pain thresholds and not biased towards potential confounding effects (eg, anxiety, stress, depression, centre effects, and pain self-evaluation). Analysis of model coefficients suggests that the most robust cortical thickness predictors of pain sensitivity are the right rostral anterior cingulate gyrus, left parahippocampal gyrus, and left temporal pole. Cortical thickness in these regions was negatively correlated to pain sensitivity. Our results can be considered as a proof-of-concept for the capacity of brain morphology to predict pain sensitivity, paving the way towards future multimodal brain-based biomarkers of pain.

The influence of psychological traits and prior experience on treatment expectations

BACKGROUND

Placebo and nocebo responses are modulated by the treatment expectations of participants and patients. However, interindividual differences predicting treatment expectations and placebo responses are unclear. In this large-scale pooled analysis, we aim to investigate the influence of psychological traits and prior experiences on treatment expectations.

METHODS

This paper analyses data from six different placebo studies (total n = 748). In all studies, participants' sociodemographic information, treatment expectations and prior treatment experiences and traits relating to stress, somatization, depression and anxiety, the Big Five and behavioral inhibition and approach tendencies were assessed using the same established questionnaires. Correlation coefficients and structural equation models were calculated to investigate the relationship between trait variables and expectations.

RESULTS

We found small positive correlations between side effect expectations and improvement expectations (r = 0.187), perceived stress (r = 0.154), somatization (r = 0.115), agitation (r = 0.108), anhedonia (r = 0.118), and dysthymia (r = 0.118). In the structural equation model previous experiences emerged as the strongest predictors of improvement (β = 0.32, p = .005), worsening (β = -0.24, p = .005) and side effect expectations (β = 0.47, p = .005). Traits related to positive affect (β = - 0.09; p = .007) and negative affect (β = 0.04; p = .014) were associated with side effect expectations.

DISCUSSION

This study is the first large analysis to investigate the relationship between traits, prior experiences and treatment expectations. Exploratory analyses indicate that experiences of symptom improvement are associated with improvement and worsening expectations, while previous negative experiences are only related to side effect expectations. Additionally, a proneness to experience negative affect may be a predictor for side effect expectation and thus mediate the occurrence of nocebo responses.

Study protocol: effects of treatment expectation toward repetitive transcranial magnetic stimulation (rTMS) in major depressive disorder-a randomized controlled clinical trial

BACKGROUND

Patients' expectations toward any given treatment are highly important for the effectiveness of such treatment, as has been demonstrated for several disorders. In particular, in major depressive disorder (MDD), one of the most frequent and most serious mental disorders with severe consequences for the affected, the augmentation of available treatment options could mean a ground-breaking success. Repetitive transcranial magnetic stimulation (rTMS), a new, non-invasive, and well-tolerated intervention with proven effects in the treatment of MDD, appears particularly suitable in this context as it is assumed to exert its effect via structures implicated in networks relevant for both expectation and depression.

METHODS

All patients will receive rTMS according to its approval. Half of the patients will be randomized to a psychological intervention, which is a comprehensive medical consultation aiming to improve positive treatment expectations; the control group will receive a conventional informed consent discussion (in the sense of a treatment-as-usual condition). As outcome parameters, instruments for both self-assessment and external assessment of depression symptoms will be applied. Furthermore, psycho-immunological parameters such as inflammation markers and the cortisol awakening response in saliva will be investigated. Resting-state functional magnetic resonance imaging (rs fMRI) will be performed to analyze functional connectivity, including the cerebellum, and to identify neuronal predictors of expectation effects. In addition, possible cerebellar involvement will be assessed based on a cerebellar-dependent motor learning paradigm (i.e., eyeblink conditioning).

DISCUSSION

In this study, the effects of treatment expectations towards rTMS are investigated in patients with MDD. The aim of this study is to identify the mechanisms underlying the expectation effects and, beyond that, to expand the potential of non-invasive and well-tolerated treatments of MDD.

TRIAL REGISTRATION

German Registry of Clinical Studies (DRKS DRKS00028017. Registered on 2022/03/07. URL: https://www.drks.de/drks_web/ .

Neural underpinnings of preferential pain learning and the modulatory role of fear

Due to its unique biological relevance, pain-related learning might differ from learning from other aversive experiences. This functional magnetic resonance imaging study compared neural mechanisms underlying the acquisition and extinction of different threats in healthy humans. We investigated whether cue-pain associations are acquired faster and extinguished slower than cue associations with an equally unpleasant tone. Additionally, we studied the modulatory role of stimulus-related fear. Therefore, we used a differential conditioning paradigm, in which somatic heat pain stimuli and unpleasantness-matched auditory stimuli served as US. Our results show stronger acquisition learning for pain- than tone-predicting cues, which was augmented in participants with relatively higher levels of fear of pain. These behavioral findings were paralleled by activation of brain regions implicated in threat processing (insula, amygdala) and personal significance (ventromedial prefrontal cortex). By contrast, extinction learning seemed to be less dependent on the threat value of the US, both on the behavioral and neural levels. Amygdala activity, however, scaled with pain-related fear during extinction learning. Our findings on faster and stronger (i.e. "preferential") pain learning and the role of fear of pain are consistent with the biological relevance of pain and may be relevant to the development or maintenance of chronic pain.

Needs and Demands for eHealth Pain Management Interventions in Chronic Pain Patients

Although chronic pain is a global health problem, the current care situation is often inadequate. eHealth offers many advantages as an additional option for treating chronic pain. Yet, an intervention's efficacy can only be fully exhausted if patients intend to use it. This study aims to identify the needs and demands of patients with chronic pain regarding intervention concepts and frameworks to develop specifically tailored eHealth pain management interventions. A cross-sectional study was conducted, including 338 individuals with chronic pain. Within the cohort, a distinction between a high- and a low-burden group was made. Respondents generally preferred a permanently accompanying mobile app, but the preferred content varied with group. According to the majority, interventions should be made available on smartphones, offer sessions once per week with a duration from 10 to 30 min, and be recommended by experts. These results can provide the basis for future eHealth pain management interventions tailored to the patients' needs and demands.

No long-term effects after a 3-week open-label placebo treatment for chronic low back pain: a 3-year follow-up of a randomized controlled trial

ABSTRACT

Chronic low back pain is prevalent, highly disabling, and a relevant socioeconomic health concern. Although allocated to placebo groups, patients in randomized controlled trials show significant pain relief, pointing to the relevance of placebo effects. Overcoming ethical and legal concerns related to deceptive placebos, recent studies have demonstrated the efficacy of short-term treatments for chronic low back pain with open-label (ie, nondeceptive) placebos. However, data on long-term efficacy of open-label placebos are sparse. Here, we report a 3-year follow-up of our previously published randomized controlled trial demonstrating pain reduction, improvement in disability, and depressive symptoms after a 3-week treatment with open-label placebos. Including records from 89 previously enrolled patients, we investigated changes between the groups with and without previous open-label placebo treatment in pain intensity (primary outcome), disability and mood (secondary outcomes), biopsychosocial factors and lifestyle (exploratory outcomes) from parent baseline to follow-up. Over the 3-year period, there were no differences in any outcome between groups with and without open-label placebo treatment. Therefore, our follow-up data do not support the previously suggested assumption that a 3-week open-label placebo treatment has long-term effects. This study was preregistered on April 14, 2020, in the German Clinical Trials Register (registration number DRKS00021405).

[Placebo effects in analgesia : Influence of expectations on the efficacy and tolerability of analgesic treatment]

Expectations of patients influence the perception and neuronal processing of acute and chronic pain and modulate the effectiveness of analgesic treatment. The expectation of treatment is not only the most important determinant of placebo analgesia. Expectations of treatment also influence the efficacy and tolerability of "active" pharmacological and non-pharmacological treatment of pain. Recent insights into the psychological and neurobiological mechanisms underlying the clinically relevant effects of treatment expectations enable and call for the systematic integration and modulation of treatment expectations into analgesic treatment concepts. Such a strategy promises to optimize analgesic treatment and to prevent or reduce the burden of unwanted side effects and the misuse of analgesics, particularly of opioids. This review highlights the current concepts, recent achievements and also challenges and key open research questions.

Savor the flavor: A randomized double-blind study assessing taste-enhanced placebo analgesia in healthy volunteers

Placebo effects substantially contribute to analgesic treatment outcomes and might be leveraged to enhance gold-standard treatments. The taste of oral medications has been proposed to boost placebo effects. Here, we aimed at estimating how far the taste of an oral medication enhances placebo analgesia. We conducted a randomized, double-blind, between-group, single-visit study, with pre-treatment baseline. Over the course of three substudies, 318 healthy volunteers (297 included) were tested in a clinical trial setting. Participants were subjected to experimental tonic cold water pain (cold pressor test) before and after receiving taste-neutral (water), or bitter (quinine), or sweet (saccharin), or no placebo drops. Pre- versus post-treatment changes in area under the pain rating curve, the main outcome, indicated that placebo treatment showed a small analgesic effect versus no treatment. Added taste induced placebo enhancement in the very small effect size range, but accounted for a substantial portion of the overall placebo effect. No noteworthy advantage of sweet over bitter placebo was observed. An exploration of heart rate (HR) recordings indicated that placebo treatments were associated with an increase in peak HR-response to cold water, but these were not associated with placebo analgesia at an individual level. Placebo treatments were associated with minimal side effects. These results indicate that added taste may be an easy-to-implement, cost-effective, and safe way to optimize treatment outcomes and that taste-neutral preparations may reduce placebo-related outcome variance in clinical trials. Further studies are needed to test if these findings can be translated into clinical scenarios.

Determining the Influencing Factors on Acceptance of eHealth Pain Management Interventions Among Patients With Chronic Pain Using the Unified Theory of Acceptance and Use of Technology: Cross-sectional Study

Background

Chronic pain is a complex disease with high prevalence rates, and many individuals who are affected do not receive adequate treatment. As a complement to conventional therapies, eHealth interventions could provide many benefits to a multimodal treatment approach for patients with chronic pain, whereby future use is associated with the acceptance of these interventions.

Objective

This study aims to assess the acceptance of eHealth pain management interventions among patients with chronic pain and identify the influencing factors on acceptance. A further objective of the study is to evaluate the viability of the Unified Theory of Acceptance and Use of Technology (UTAUT) model and compare it with its extended version in terms of explained variance of acceptance.

Methods

We performed a cross-sectional web-based study. In total, 307 participants with chronic pain, as defined according to the International Association for the Study of Pain criteria, were recruited through flyers, posters, and web-based inquiries between December 2020 and July 2021. In addition to sociodemographic and medical data, the assessment included validated psychometric instruments and an extended version of the well-established UTAUT model. For statistical analyses, group comparisons and multiple hierarchical regression analyses were performed.

Results

The acceptance of eHealth pain management interventions among patients with chronic pain was overall moderate to high (mean 3.67, SD 0.89). There was significant difference in acceptance among age groups (W=9674.0; r=0.156; P=.04). Effort expectancy (β=.37; P<.001), performance expectancy (β=.33; P<.001), and social influence (β=.34; P<.001) proved to be the most important predictors of acceptance. The extended UTAUT (including the original UTAUT factors as well as sociodemographic, medical, and eHealth-related factors) model explained 66.4% of the variance in acceptance, thus supporting the viability of the model. Compared with the original UTAUT model (performance expectancy, effort expectancy, and social influence), the extended model explained significantly more variance (F_25,278=1.74; P=.02).

Conclusions

Given the association between acceptance and future use, the knowledge of the influencing factors on acceptance should be used in the development and promotion of eHealth pain management interventions. Overall, the acceptance of eHealth pain management interventions was moderate to high. In total, 8 predictors proved to be significant predictors of acceptance. The UTAUT model is a valuable instrument for determining acceptance as well as the factors that influence acceptance of eHealth pain management interventions among patients with chronic pain. The extended UTAUT model provided the greatest predictive value for acceptance.

Greater interruption of visual processing and memory encoding by visceral than somatic pain in healthy volunteers - An fMRI study

Visceral pain is regarded as more salient than somatic pain. It has greater affective and emotional components, i.e., it elicits higher levels of pain-related fear and is perceived as more unpleasant than somatic pain. In this fMRI study, we examined the neural effects of painful visceral as compared to painful somatic stimulation on visual processing and memory encoding in a visual categorization and surprise recognition task in healthy volunteers. During the categorization task, participants received either rectal distensions or heat stimuli applied to the forearm, with stimuli being individually matched for unpleasantness. Behaviorally, visceral pain reduced memory encoding as compared to somatic pain (Kleine-Borgmann et al., 2021). Imaging analyses now revealed that visceral pain was associated with reduced activity (i.e., greater pain-related interruption) in neural areas typically involved in visual processing and memory encoding. These include the parahippocampal gyrus, fusiform gyrus, striatum, occipital cortex, insula, and the amygdala. Moreover, reduced engagement of the lateral occipital complex during visual categorization under visceral pain was associated with higher visceral pain-related fear. These findings obtained in healthy volunteers shed light on the neural circuitry underlying the interruptive effect of visceral pain and pave the way for future studies in patient samples.

Impaired pain-related threat and safety learning in patients with chronic back pain

ABSTRACT

Pain-related learning mechanisms likely play a key role in the development and maintenance of chronic pain. Previous smaller-scale studies have suggested impaired pain-related learning in patients with chronic pain, but results are mixed, and chronic back pain (CBP) particularly has been poorly studied. In a differential conditioning paradigm with painful heat as unconditioned stimuli, we examined pain-related acquisition and extinction learning in 62 patients with CBP and 61 pain-free healthy male and female volunteers using valence and contingency ratings and skin conductance responses. Valence ratings indicate significantly reduced threat and safety learning in patients with CBP, whereas no significant differences were observed in contingency awareness and physiological responding. Moreover, threat learning in this group was more impaired the longer patients had been in pain. State anxiety was linked to increased safety learning in healthy volunteers but enhanced threat learning in the patient group. Our findings corroborate previous evidence of altered pain-related threat and safety learning in patients with chronic pain. Longitudinal studies exploring pain-related learning in (sub)acute and chronic pain are needed to further unravel the role of aberrant pain-related learning in the development and maintenance of chronic pain.

Influence on study outcomes of an inpatient study by the behavior of the study staff (PINgPOng): study protocol for a randomized clinical trial

Background

The placebo effect as the symptom improvement following inert treatments is a fixed component of RCTs to differentiate between specific effects of the tested pharmacological substance from other unspecific effects. The PINgPOng study was set up to analyze the influence of a study team trained to either minimize the placebo response and optimize drug-placebo differences or to maximize the placebo response to increase drug efficacy by unspecific factors on the study results of a RCT in a classical early clinical trial setting.

Methods/design

PINgPOng is a single-center, prospective, randomized, double-blind, placebo-controlled study in a 3-group, 2-sequence, 2-period cross-over design. The study is conducted according to the principles of ICH-GCP and the Declaration of Helsinki on the Phase I-Unit of the University Hospital Bonn. The primary endpoint is the pain intensity in the cold pressor test before and after the administration of 15 mg oxycodone or placebo. The pain intensity is compared between three study conditions: 32 healthy volunteers in each study arm will be treated either by an untrained study team (arm A), by a study team trained to maximize (arm B), or to minimize placebo responses (arm C). Neuroendocrine factors (alpha-amylase activity, salivary cortisol), characteristic traits (anxiety, depression, stress), and somatic reactions are analyzed as covariates of the pain perception.

Discussion

The PINgPOng study will allow to answer the question whether and to what extent the behavior of a trained study team (neutral vs. maximize vs. minimize placebo responses) will differentially affect placebo responses in a setting of a highly standardized early clinical trial. The results will help to control the placebo effects by education of the clinical study team and to avoid unnecessary high placebo effects in clinical development.

Trial registration

German Clinical Trials Register DRKS00013586. Registered on December 22, 2017.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06436-0.

[Neurobiological and neurochemical mechanisms of placebo analgesia]

BACKGROUND

The efficacy of pain therapies can be substantially modulated by treatment expectations, which is reflected by the substantial placebo effects observed in pain (so called placebo analgesia).

QUESTION

What is currently known about the neurobiological and neurochemical mechanisms underlying placebo analgesia?

MATERIALS AND METHODS

A focused presentation of key publications in the field embedded in a structured overview of the mechanistic concepts and current theories according to recent evidence.

RESULTS

Experimental studies with functional neuroimaging showed that the effect of placebo analgesia is reflected by changes in brain activity related to pain processing and cognitive control. The important neurotransmitters involved include opioids and dopamine.

CONCLUSION

Placebo analgesia is associated with complex neurobiological and -physiological mechanisms. An advanced comprehension of these processes should be applied to optimize existing and future therapeutic approaches in pain therapy.

Hippocampus mediates nocebo impairment of opioid analgesia through changes in functional connectivity

The neural mechanisms underlying placebo analgesia have attracted considerable attention over the recent years. In contrast, little is known about the neural underpinnings of a nocebo-induced increase in pain. We previously showed that nocebo-induced hyperalgesia is accompanied by increased activity in the hippocampus that scaled with the perceived level of anxiety. As a key node of the neural circuitry of perceived threat and fear, the hippocampus has recently been proposed to coordinate defensive behaviour in a context-dependent manner. Such a role requires close interactions with other regions involved in the detection of and responses to threat. Here, we investigated the functional connectivity of the hippocampus during nocebo-induced hyperalgesia. Our results show an increase in functional connectivity between hippocampus and brain regions implicated in the processing of sensory-discriminative aspects of pain (posterior insula and primary somatosensory/motor cortex) as well as the periaqueductal gray (PAG). This nocebo-induced increase in connectivity scaled with an individual's increase in anxiety. Moreover, hippocampus connectivity with the amygdala was negatively correlated with the pain intensity reported during nocebo hyperalgesia relative to the placebo condition. Our findings suggest that the hippocampus links nocebo-induced anxiety to a heightened responsiveness to nociceptive input through changes in its crosstalk with pain-modulatory brain areas.

Impact of the COVID-19 pandemic on patients with chronic pain in Germany: associations with expectations and control beliefs

Background

While the COVID‐19 pandemic is affecting people's well‐being worldwide, it may place a particularly high burden on people with chronic pain, as pain is known to be influenced by societal and psychological conditions.

Methods

In this observational study, we conducted telephone interviews with 196 patients with chronic pain to assess the impact of the pandemic on various aspects of their pain and everyday life. The initial interviews were conducted between April and May 2020 and were followed up by a second interview between August and December 2020.

Results

A substantial percentage of patients (39% at the first and 32% at the second interview) reported an increase in pain intensity due to the pandemic. Exploratory analyses revealed that patients who already suffered from greater pain and who experienced greater restrictions due to the pandemic were more likely to express pain worsening. Psychological factors such as negative expectations about the development of their pain and pain treatment and a high external locus of control were also associated with increases in pain.

Conclusions

These findings illustrate the complexity of chronic pain, suggesting that not only the impact of the pandemic on various areas of life but also the severity of the pain‐symptoms themselves and psychological factors influence the course of patients' symptoms during the pandemic.

Significance

This study underlines the importance of psychosocial factors in chronic pain and demonstrates that the societal and psychological impact of the COVID‐19 pandemic can affect patients' pain and their ability to cope with it. The extent to which patients experience pain aggravation seems to interact with other psychological factors such as pain expectations and control beliefs.

Acquisition learning is stronger for aversive than appetitive events

Appetitive and aversive learning are both key building blocks of adaptive behavior, yet knowledge regarding their differences is sparse. Using a capsaicin heat pain model in 36 healthy participants, this study directly compared the acquisition and extinction of conditioned stimuli (CS) predicting pain exacerbation and relief. Valence ratings show stronger acquisition during aversive compared to appetitive learning, but no differences in extinction. Skin conductance responses and contingency ratings confirmed these results. Findings were unrelated to individual differences in pain sensitivity or psychological factors. Our results support the notion of an evolutionarily hardwired preponderance to acquire aversive rather than appetitive cues as is protective for acute aversive states such as pain but may contribute to the development and maintenance of clinical conditions such as chronic pain, depression or anxiety disorders.

In this study, acquisition and extinction of conditioned stimuli are compared in a capsaicin heat pain paradigm in healthy human participants. The results demonstrate a preponderance to acquire aversive rather than appetitive cues, which could initially have a protective function but eventually contribute to the maintenance of chronic pain.

Does pain modality play a role in the interruptive function of acute visceral compared with somatic pain?

ABSTRACT

Acute pain captures attentional resources and interferes with ongoing cognitive processes, including memory encoding. Despite broad clinical implications of this interruptive function of pain for the pathophysiology and treatment of chronic pain conditions, existing knowledge exclusively relies on studies using somatic pain models. Visceral pain is highly prevalent and seems to be more salient and threatening, suggesting that the interruptive function of pain may be higher in acute visceral compared with somatic pain. Implementing rectal distensions as a clinically relevant experimental model of visceral pain along with thermal cutaneous pain for the somatic modality, we herein examined the impact of pain modality on visual processing and memory performance in a visual encoding and recognition task and explored the modulatory role of pain-related fear and expectation in 30 healthy participants. Despite careful and dynamically adjusted matching of stimulus intensities to perceived pain unpleasantness over the course of trials, we observed greater impairment of cognition performance for the visceral modality with a medium effect size. Task performance was not modulated by expectations or by pain-related fear. Hence, even at matched unpleasantness levels, acute visceral pain is capable of interfering with memory encoding, and this impact seems to be relatively independent of pain-related cognitions or emotions, at least in healthy individuals. These results likely underestimate the detrimental effect of chronic pain on cognitive performance, which may be particularly pronounced in acute and chronic visceral pain.

The beneficial effect of positive treatment expectations on pharmacological migraine prophylaxis

ABSTRACT

Migraine is one of the leading causes of years lived with disability and considered to be a major global health concern. Pharmacological preventive treatment often causes side effects that limit the adherence to longer-term treatment regimens. Both experimental and clinical evidence suggests that positive expectations can modulate pain and analgesic treatment effects. However, the role of expectations in migraine prophylactic treatment has not systematically been investigated. Here, we examined the influence of treatment expectation before commencing pharmacological preventive treatment on its efficacy and tolerability in N = 134 episodic (30%) and chronic migraine (70%) patients in a prospective, longitudinal observational study over the course of 6 months. The migraine prophylaxis reduced the number of headache and migraine days with acceptable tolerability. Positive treatment expectation was associated with a generally lower number of headache and migraine days and a stronger reduction in headache days over the course of the treatment in chronic but not in episodic migraine patients. Moreover, patients with prior treatment showed a stronger reduction in headache days with higher expectation as compared to patients without prior experience. Our results underscore the relevance of further exploring the role of treatment expectation and its systematic modulation in patients with migraine and other pain conditions.

The occurrence of neuropathic pain following surgery of brainstem cavernous malformations

BACKGROUND AND PURPOSE

This study aimed to assess the occurrence and significance of postoperative neuropathic pain (NP) in patients with surgically treated brainstem cavernous malformations (BSCMs).

METHODS

Seventy-four BSCM patients surgically treated between 2003 and 2019 were reviewed for the occurrence of postoperative NP and related treatment. The relevance of BSCM location, preoperative characteristics, influence on functional outcome, postoperative health-related quality of life (HRQOL) and life satisfaction was evaluated.

RESULTS

Six out of 74 patients (8%) suffered from NP. The Leeds Assessment of Neuropathic Symptoms and Signs scores ranged from 12 to 16 (mean 14.28 ± 1.6). Visual analog scale pain was 5.2 ± 2.0. NP had no effect on preoperative characteristics or functional outcome. Bodily pain (HRQOL) and vocational time (life satisfaction) were significantly decreased in NP compared to non-NP patients. Specific BSCM location (regarding brainstem nuclei involved in pain processing) and other preoperative patient- and BSCM-related parameters were not associated with the occurrence of postoperative NP. Three out of six patients were currently under NP-specific treatment. The proportion of patients suffering from postoperative NP (8%) was substantially higher compared to previously published studies. The pain affected the HRQOL of patients, most of whom were insufficiently treated and not satisfied with treatment results.

CONCLUSION

Our findings may help to raise awareness for postoperative NP in BSCM, which is essential to improve diagnosis and initiation of proper treatment, as well as preoperative informed consent of patients.

What Should Clinicians Tell Patients about Placebo and Nocebo Effects? Practical Considerations Based on Expert Consensus

INTRODUCTION

Clinical and laboratory studies demonstrate that placebo and nocebo effects influence various symptoms and conditions after the administration of both inert and active treatments.

OBJECTIVE

There is an increasing need for up-to-date recommendations on how to inform patients about placebo and nocebo effects in clinical practice and train clinicians how to disclose this information.

METHODS

Based on previous clinical recommendations concerning placebo and nocebo effects, a 3-step, invitation-only Delphi study was conducted among an interdisciplinary group of internationally recognized experts. The study consisted of open- and closed-ended survey questions followed by a final expert meeting. The surveys were subdivided into 3 parts: (1) informing patients about placebo effects, (2) informing patients about nocebo effects, and (3) training clinicians how to communicate this information to the patients.

RESULTS

There was consensus that communicating general information about placebo and nocebo effects to patients (e.g., explaining their role in treatment) could be beneficial, but that such information needs to be adjusted to match the specific clinical context (e.g., condition and treatment). Experts also agreed that training clinicians to communicate about placebo and nocebo effects should be a regular and integrated part of medical education that makes use of multiple formats, including face-to-face and online modalities.

CONCLUSIONS

The current 3-step Delphi study provides consensus-based recommendations and practical considerations for disclosures about placebo and nocebo effects in clinical practice. Future research is needed on how to optimally tailor information to specific clinical conditions and patients' needs, and on developing standardized disclosure training modules for clinicians.

Network properties and regional brain morphology of the insular cortex correlate with individual pain thresholds

Pain thresholds vary considerably across individuals and are influenced by a number of behavioral, genetic and neurobiological factors. However, the neurobiological underpinnings that account for individual differences remain to be fully elucidated. In this study, we used voxel‐based morphometry (VBM) and graph theory, specifically the local clustering coefficient (CC) based on resting‐state connectivity, to identify brain regions, where regional gray matter volume and network properties predicted individual pain thresholds. As a main finding, we identified a cluster in the left posterior insular cortex (IC) reaching into the left parietal operculum, including the secondary somatosensory cortex, where both regional gray matter volume and the local CC correlated with individual pain thresholds. We also performed a resting‐state functional connectivity analysis using the left posterior IC as seed region, demonstrating that connectivity to the pre‐ as well as postcentral gyrus bilaterally; that is, to the motor and primary sensory cortices were correlated with individual pain thresholds. To our knowledge, this is the first study that applied VBM in combination with voxel‐based graph theory in the context of pain thresholds. The co‐location of the VBM and the local CC cluster provide first evidence that both structure and function map to the same brain region while being correlated with the same behavioral measure; that is, pain thresholds. The study highlights the importance of the posterior IC, not only for pain perception in general, but also for the determination of individual pain thresholds.

Impact of a 12-week open-label placebo treatment on headache days in episodic and chronic migraine: a study protocol for a parallel-group, multicentre, randomised controlled trial

INTRODUCTION

Migraine is the most common neurological disorder and one of the major causes of years lived with disability. Its treatment (especially of chronic forms) is often challenging and accompanied with adverse effects. Although new therapeutic approaches have recently emerged (eg, calcitonin gene-related peptide antibodies), these are linked to strict prescribing guidelines and therefore limited to only a minority of patients. Recently, randomised controlled trials have demonstrated that open-label placebo treatments can lead to significant and clinically relevant improvements of chronic pain conditions.

METHODS AND ANALYSIS

This multicentre, randomised controlled clinical trial following a parallel group between-subject design aims to systematically investigate the impact of a 12-week open-label placebo treatment on moderate to severe headache days (primary outcome) in patients with episodic and chronic migraine in addition to treatment as usual. Secondary outcomes comprise the number of migraine days, pain intensity, intake of acute medication, quality of life, disability, global impression of change, tolerability and a responder rate. To systematically address potential predictors of placebo responses in patients with migraine, this study assesses potential psychometric predictors, salivary cortisol and alpha-amylase awakening responses, catechol-o-methyltransferase Val158Met polymorphisms, as well as functional and structural brain connectivity (ie, resting state functional MRI, diffusion tensor imaging). The data analysis will be performed on basis of the general linear model considering repeated measures (mixed model).

ETHICS AND DISSEMINATION

This protocol and all corresponding documents were approved with regard to their content and compliance with ethical regulations by the Ethics Committee of the Medical Faculty of the University Duisburg-Essen, Germany and the Ethics Committee of the Landesärztekammer Hessen. The results from this study will be actively disseminated through manuscript publications and conference presentations.

TRIAL REGISTRATION NUMBER

German Clinical Trials Register (DRKS00021259).

Tilidine and dipyrone (metamizole) in cold pressor pain: A pooled analysis of efficacy, tolerability, and safety in healthy volunteers

The cold pressor test (CPT) is widely implemented and offers a simple, experimental acute pain model utilizing cold pain. Previous trials have frequently paired the CPT with opioids in order to investigate the mechanisms underlying pharmacological analgesia, due to their known analgesic efficacy. However, opioid side effects may lead to unblinding and raise concerns about the safety of the experimental setting. Despite the established clinical efficacy of dipyrone (metamizole), its efficacy, tolerability, and safety in cold pressor pain has not been systematically addressed to date. This pooled analysis included data of 260 healthy volunteers from three randomized, placebo‐controlled, double‐blind substudies using the CPT following a pre‐test‐post‐test‐design. These substudies allow for comparing a single dose of 800 mg dipyrone with two different doses of the opioid tilidine/naloxone (50/4 mg and 100/8 mg, respectively). Outcomes included pain intensity ratings, pain tolerance, medication‐attributed side effects, as well as changes of blood pressure and heart rate. We demonstrate that both opioid doses and dipyrone had a comparable, significant analgesic effect on cold pressor pain. However, dipyrone was associated with significantly less self‐reported adverse effects and these were not significantly different from those under placebo. These results indicate that the combination of dipyrone and the CPT provides a safe, tolerable, and effective experimental model for the study of pharmacological analgesia. In combination with a CPT, dipyrone may be useful as a positive control, or baseline medication for the study of analgesic modulation.

Meta-analysis of neural systems underlying placebo analgesia from individual participant fMRI data

The brain systems underlying placebo analgesia are insufficiently understood. Here we performed a systematic, participant-level meta-analysis of experimental functional neuroimaging studies of evoked pain under stimulus-intensity-matched placebo and control conditions, encompassing 603 healthy participants from 20 (out of 28 eligible) studies. We find that placebo vs. control treatments induce small, widespread reductions in pain-related activity, particularly in regions belonging to ventral attention (including mid-insula) and somatomotor networks (including posterior insula). Behavioral placebo analgesia correlates with reduced pain-related activity in these networks and the thalamus, habenula, mid-cingulate, and supplementary motor area. Placebo-associated activity increases occur mainly in frontoparietal regions, with high between-study heterogeneity. We conclude that placebo treatments affect pain-related activity in multiple brain areas, which may reflect changes in nociception and/or other affective and decision-making processes surrounding pain. Between-study heterogeneity suggests that placebo analgesia is a multi-faceted phenomenon involving multiple cerebral mechanisms that differ across studies.

Effects of Patients' Expectation in Dermatology: Evidence from Experimental and Clinical Placebo Studies and Implications for Dermatologic Practice and Research

Patients' expectations towards the benefit of a treatment are key determinants of placebo responses and can affect the development and course of medical conditions and the efficacy and tolerability of active medical treatment. The mechanisms mediating these placebo and nocebo effects have been best described in the field of experimental pain and placebo analgesia. However, also in dermatology experimental and clinical studies demonstrate that various skin diseases such as inflammatory dermatoses and allergic reactions can be modulated by patients' expectations. Dermatologists should consider the important modulatory role of patients' expectations on the efficacy and tolerability of specific treatments and the key role of verbal information, patients' prior treatment experiences (associative learning), and the quality and quantity of doctor-patient communication in shaping treatment expectation. As a consequence, techniques aiming at maximizing patients' expectation effects should be implemented into daily clinical routine. By contrast, in clinical studies expectation effects should be maximally controlled and harmonized to improve the "assay sensitivity" to detect new compounds. Further translational studies, also in dermatoses that have not been investigated yet, are needed to better characterize the mechanisms underlying patients' expectation and to gain further insights into potential clinical implications of these effects in dermatologic conditions. Therefore, in this review, we provide a brief overview on the concept of expectation effects on treatment outcome in general, summarize what is already known about this topic for dermatologic diseases, and finally present the relevance of this topic in clinical dermatology.

Der Placeboeffekt in der Schmerztherapie – für den klinischen Alltag nutzbar? Ja, unbedingt!

Als Placeboeffekte bezeichnet man positive physiologische oder psychologische Veränderungen, die nach einer Einnahme von Medikamenten ohne spezifischen Wirkstoff oder Scheineingriffen auftreten und durch Erwartungs- und Konditionierungsprozesse induziert werden. Die mit Placeboeffekten einhergehenden neurobiologischen und peripher-physiologischen Vorgänge können auch bei der Vergabe von wirkstoffhaltigen Medikamenten eine wichtige Rolle spielen und sind somit nicht zwingend an die Gabe eines Scheinmedikamentes gebunden. Die Darreichung von „traditionellen“ Placebos ist im klinischen Alltag aus juristischen und ethischen Gründen höchst problematisch. Dieser Beitrag zeigt neben neuen Erkenntnissen zu offenen Placebo-Anwendungen (Open-Label Placebos) Wege auf, wie die zugrundeliegenden Mechanismen von Placeboantworten dennoch gezielt im schmerztherapeutischen Alltag genutzt werden können, um die Wirksamkeit, Verträglichkeit und Compliance bestehender pharmakologischer und anderer Therapien zum Wohle des Patienten zu optimieren.

[Placebo effects in pain therapy]

In the past few decades, research on pain and placebo analgesia has gained importance both scientifically and clinically. In this article, the current findings and focus of research as well as the significance of placebo research for assessing the effectiveness of pain medication are illustrated. The underlying mechanisms of placebo analgesia not only have implications for theoretical models but also offer clinically relevant guidelines for everyday interventions in pain treatment. However, many placebo phenomena are not fully understood and have to be investigated further in order to exploit the full potential of placebo effects. Interindividual differences and their inclusion in treatment will play a major role in this aspect.

Enhanced pain-related conditioning for face compared to hand pain

Pain is evolutionarily hardwired to signal potential danger and threat. It has been proposed that altered pain-related associative learning processes, i.e., emotional or fear conditioning, might contribute to the development and maintenance of chronic pain. Pain in or near the face plays a special role in pain perception and processing, especially with regard to increased pain-related fear and unpleasantness. However, differences in pain-related learning mechanisms between the face and other body parts have not yet been investigated. Here, we examined body-site specific differences in associative emotional conditioning using electrical stimuli applied to the face and the hand. Acquisition, extinction, and reinstatement of cue-pain associations were assessed in a 2-day emotional conditioning paradigm using a within-subject design. Data of 34 healthy subjects revealed higher fear of face pain as compared to hand pain. During acquisition, face pain (as compared to hand pain) led to a steeper increase in pain-related negative emotions in response to conditioned stimuli (CS) as assessed using valence ratings. While no significant differences between both conditions were observed during the extinction phase, a reinstatement effect for face but not for hand pain was revealed on the descriptive level and contingency awareness was higher for face pain compared to hand pain. Our results indicate a stronger propensity to acquire cue-pain-associations for face compared to hand pain, which might also be reinstated more easily. These differences in learning and resultant pain-related emotions might play an important role in the chronification and high prevalence of chronic facial pain and stress the evolutionary significance of pain in the head and face.

Quantitative Sensory Testing (QST) in Drug-Naïve Patients with Parkinson's Disease

BACKGROUND

Pain is highly prevalent in patients with Parkinson's disease (PD), but underlying pathophysiological mechanisms are largely unclear. Alterations in somatosensory processing might contribute to sensory abnormalities in PD.

OBJECTIVE

This study investigated sensory processing in PD patients.

METHODS

We used the standardized "Quantitative Sensory Testing" (QST) protocol (German Research Network on Neuropathic Pain) to investigate 13 somatosensory parameters in 19 PD patients naïve to dopaminergic medication and 19 healthy controls matched for age, gender, and handedness. We tested for differences in sensory parameters between i) drug-naïve PD patients and healthy controls, ii) patients' more and less affected body side, and iii) for an association of somatosensory parameters with disease-specific factors.

RESULTS

We did not observe any significant group differences in somatosensory parameters between PD patients and healthy subjects. In PD patients, QST mean z-scores did not differ between the predominantly and the less affected body side, PD patients with and without PD-specific chronic pain or between different PD subtypes. Age, but not PD disease severity, was associated with a greater loss of function in thermal and mechanical detection thresholds.

CONCLUSIONS

Somatosensory processing, as assessed with the well-established QST protocol, was normal in drug-naïve PD patients. Thus, somatosensory abnormalities previously reported in medicated PD patients might rather be a result of dopaminergic medication, or may occur later in the course of the disease or with increasing age.

Pain-free resting-state functional brain connectivity predicts individual pain sensitivity

Individual differences in pain perception are of interest in basic and clinical research as altered pain sensitivity is both a characteristic and a risk factor for many pain conditions. It is, however, unclear how individual sensitivity to pain is reflected in the pain-free resting-state brain activity and functional connectivity. Here, we identify and validate a network pattern in the pain-free resting-state functional brain connectome that is predictive of interindividual differences in pain sensitivity. Our predictive network signature allows assessing the individual sensitivity to pain without applying any painful stimulation, as might be valuable in patients where reliable behavioural pain reports cannot be obtained. Additionally, as a direct, non-invasive readout of the supraspinal neural contribution to pain sensitivity, it may have implications for translational research and the development and assessment of analgesic treatment strategies.

Somatosensory Deficits After Ischemic Stroke

Background and Purpose- About 50% to 80% of stroke survivors present with somatosensory deficits. Somatosensory deficits because of an ischemic stroke are determined by the infarct location. However, a detailed understanding of the long-term effect of lesions on somatosensory performance is lacking. Methods- This prospective observational study enrolled 101 ischemic stroke patients. For voxel-based lesion-symptom mapping, magnetic resonance imaging fluid-attenuated inversion recovery imaging infarct lesions were segmented within 5 days after stroke. Standardized tests such as the National Institutes of Health Stroke Scale and the Rivermead Assessment of Somatosensory Performance were performed during acute stage, after 3 and 12 months. This included bilateral testing for multiple tactile and proprioceptive somatosensory modalities (pressure, light touch, sharp-dull discrimination, temperature discrimination, sensory extinction, 2-point discrimination, and joint position and movement sense). We further study the association of acute somatosensory deficit with functional outcome 12 months after stroke assessed by the modified Rankin Scale using univariate and multiple linear regression analysis also including acute motor deficit assessed by the arm research action test. Results- Sixty patients (59.4%) showed impairment in at least one somatosensory modality. Light touch was most frequently affected (38.7%), whereas temperature was least frequently affected (21.8%). After 3 months, significant recovery was observed in all somatosensory modalities, with only minor additional improvements after 12 months. Voxel-based lesion-symptom mapping revealed significant associations of lesions in the primary and secondary somatosensory and insular cortex with somatosensory deficits. Acute somatosensory deficit was associated with functional outcome at 12 months. However, including the acute motor deficit, somatosensory deficit was no longer an independent predictor of functional outcome. Conclusions- Our study confirms that somatosensory deficits are frequent in acute ischemic stroke but largely recover over time. Infarct lesions in the primary and secondary somatosensory cortex and insula show a robust association with somatosensory impairment. Long-term disability is influenced by somatosensory deficits but driven by motor symptoms.

Placebo response rates and potential modifiers in double-blind randomized controlled trials of second and newer generation antidepressants for major depressive disorder in children and adolescents: a systematic review and meta-regression analysis

Children and adolescents with major depressive disorder (MDD) appear to be more responsive to placebo than adults in randomized placebo-controlled trials (RCTs) of second and newer generation antidepressants (SNG-AD). Previous meta-analyses obtained conflicting results regarding modifiers. We aimed to conduct a meta-analytical evaluation of placebo response rates based on both clinician-rating and self-rating scales. Based on the most recent and comprehensive study on adult data, we tested whether the placebo response rates in children and adolescents with MDD also increase with study duration and number of study sites. We searched systematically for published RCTs of SNG-AD in children and/or adolescents (last update: September 2017) in public domain electronic databases and additionally for documented studies in clinical trial databases. The log-transformed odds of placebo response were meta-analytically analyzed. The primary and secondary outcomes were placebo response rates at the end of treatment based on clinician-rating and self-rating scales, respectively. To examine the impact of study duration and number of study sites on placebo response rates, we performed simple meta-regression analyses. We selected other potential modifiers of placebo response based on significance in at least one previous pediatric meta-analysis and on theoretical considerations to perform explorative analyses. We applied sensitivity analyses with placebo response rates closest to week 8 to compare our data with those reported for adults. We identified 24 placebo-controlled trials (2229 patients in the placebo arms). The clinician-rated placebo response rates ranged from 22 to 62% with a pooled response rate of 45% (95% CI 41-50%). The number of study sites was a significant modifier in the simple meta-regression analysis [odds ratio (OR) 1.01, 95% CI 1.01-1.02, p = 0.0003, k = 24) with more study sites linked to a higher placebo response. Study duration was not significantly associated with the placebo response rate. The explorative simple analyses revealed that publication year may be an additional modifier. However, in the explorative multivariable analysis including the number of study sites and the publication year only the number of study sites reached a p value ≤ 0.05. The self-rated placebo response rates ranged from 1 to 68% with a pooled response rate of 26% (95% CI 10-54%) (k = 6; n = 396). This meta-analysis confirms a high pooled placebo response rate in children and adolescents based on clinician ratings, which exceeds that observed in the most recent meta-analysis of placebo effects in adults (36%; 95% CI 35-37%) published in 2016. However, and similar to findings in adults, the pooled response rates based on self-ratings were substantially lower. In accordance with previous meta-analyses, we corroborated the number of study sites as significant modifier. In comparison to the recent adult meta-analysis, the substantially lower number of pediatric studies entails a reduced power to detect modifiers. Future studies should provide more precise and homogenous information to support discovery of potential modifiers and consider no-treatment-if ethically permissible-to allow differentiation between placebo and spontaneous remission rates. If these differ, practicing clinicians should facilitate placebo effects as an addition to the verum effect to maximize benefits. Further research is required to explain the discrepant response rates between clinician and self-ratings.

The Context of Values in Pain Control: Understanding the Price Effect in Placebo Analgesia

The experience of pain relief arises from physiological and psychological factors, and attributes such as the commercial features of analgesic treatments have been shown to influence placebo analgesia by affecting treatment expectations. Therefore, treatment valuation from price information should influence the placebo analgesic effect. This hypothesis was tested in a functional magnetic resonance imaging study in which healthy subjects were enrolled in a 2-day experiment. On day 1, the participants (n = 19) had treatment experiences with 2 different placebo creams during a conditioning session without receiving information on treatment price. On day 2, placebo analgesia was tested after providing price information (high vs low) while functional magnetic resonance imaging was performed. The results showed that the higher priced placebo treatment leads to enhanced pain relief. Placebo analgesia in response to the higher priced treatment was associated with activity in the ventral striatum, ventromedial prefrontal cortex, and ventral tegmental area. The behavioral results indicate that the experience of pain was influenced by treatment valuation from price. Our findings reveal that the context of values in pain control is associated with activity in expectation- and reward-related circuitry. PERSPECTIVE: Treatment with higher price was associated with enhanced placebo analgesia, and this effect was influenced by activities in expectation and reward processing brain areas. The context of value such as medical cost influences cognitive evaluation processes to modulate pain. Our study may help evaluate a patient's preference toward high-priced drugs.

Placebo Effects on the Neurologic Pain Signature: A Meta-analysis of Individual Participant Functional Magnetic Resonance Imaging Data

Importance

Placebo effects reduce pain and contribute to clinical analgesia, but after decades of research, it remains unclear whether placebo treatments mainly affect nociceptive processes or other processes associated with pain evaluation.

Objective

We conducted a systematic, participant-level meta-analysis to test the effect of placebo treatments on pain-associated functional neuroimaging responses in the neurologic pain signature (NPS), a multivariate brain pattern tracking nociceptive pain.

Data Sources

Medline (PubMed) was searched from inception to May 2015; the search was augmented with results from previous meta-analyses and expert recommendations.

Study Selection

Eligible studies were original investigations that were published in English in peer-reviewed journals and that involved functional neuroimaging of the human brain with evoked pain delivered under stimulus intensity-matched placebo and control conditions. The authors of all eligible studies were contacted and asked to provide single-participant data.

Data Extraction and Synthesis

Data were collected between December 2015 and November 2017 following the Preferred Reporting Items for Systematic Review and Meta-Analyses of individual participant data guidelines. Results were summarized across participants and studies in a random-effects model.

Main Outcomes and Measures

The main, a priori outcome was NPS response; pain reports were assessed as a secondary outcome.

Results

We obtained data from 20 of 28 identified eligible studies, resulting in a total sample size of 603 healthy individuals. The NPS responses to painful stimulation compared with baseline conditions were positive in 575 participants (95.4%), with a very large effect size (g = 2.30 [95% CI, 1.92 to 2.69]), confirming its sensitivity to nociceptive pain in this sample. Placebo treatments showed significant behavioral outcomes on pain ratings in 17 of 20 studies (85%) and in the combined sample (g = -0.66 [95% CI, -0.80 to -0.53]). However, placebo effects on the NPS response were significant in only 3 of 20 studies (15%) and were very small in the combined sample (g = -0.08 [95% CI, -0.15 to -0.01]). Similarly, analyses restricted to studies with low risk of bias (g = -0.07 [95% CI, -0.15 to 0.00]) indicated very small effects, and analyses of just placebo responders (g = -0.22 [95% CI, -0.34 to -0.11]) indicated small effects, as well.

Conclusions and Relevance

Placebo treatments have moderate analgesic effects on pain reports. The very small effects on NPS, a validated measure that tracks levels of nociceptive pain, indicate that placebo treatments affect pain via brain mechanisms largely independent of effects on bottom-up nociceptive processing.

The cerebellum is involved in processing of predictions and prediction errors in a fear conditioning paradigm

Prediction errors are thought to drive associative fear learning. Surprisingly little is known about the possible contribution of the cerebellum. To address this question, healthy participants underwent a differential fear conditioning paradigm during 7T magnetic resonance imaging. An event-related design allowed us to separate cerebellar fMRI signals related to the visual conditioned stimulus (CS) from signals related to the subsequent unconditioned stimulus (US; an aversive electric shock). We found significant activation of cerebellar lobules Crus I and VI bilaterally related to the CS+ compared to the CS-. Most importantly, significant activation of lobules Crus I and VI was also present during the unexpected omission of the US in unreinforced CS+ acquisition trials. This activation disappeared during extinction when US omission became expected. These findings provide evidence that the cerebellum has to be added to the neural network processing predictions and prediction errors in the emotional domain.

Conditioned pain modulation in drug-naïve patients with de novo Parkinson's disease

Background

Pain is highly prevalent in patients with Parkinson’s disease (PD), but underlying pathophysiological mechanisms are largely unclear. In many chronic pain syndromes deficits in endogenous pain inhibition have been detected that can be assessed using conditioned pain modulation paradigms. Previous studies employing this approach in medicated PD patients did not find abnormal pain inhibition. However, these results might have been confounded by residual dopaminergic medication.

Methods

An established conditioned pain modulation paradigm was used in 17 drug-naïve de novo PD patients and 17 healthy age and gender-matched controls. We tested i) whether conditioned pain modulation responses differed between the patient and control group and ii) whether pain inhibition differed between PD subtypes.

Results

PD patients and healthy controls did not differ in their conditioned pain modulation responses. Furthermore, there were no significant differences in CPM responses depending on the PD subtype. However, at a descriptive level, tremor-dominant patients showed a tendency for better descending pain inhibition compared to akinetic-rigid and mixed type patients.

Conclusions

In this first study investigating conditioned pain modulation in de novo PD patients, we found no additional impairment in descending pain modulation besides the known age-related decline. Our findings indicate that mechanisms other than an impaired descending inhibition contribute to high pain prevalence rates in PD and suggest that mechanisms underlying pain may differ between PD subtypes.

Electronic supplementary material

The online version of this article (10.1186/s42466-019-0029-x) contains supplementary material, which is available to authorized users.

Enhanced Neural Reinstatement for Evoked Facial Pain Compared With Evoked Hand Pain

Memory retrieval is accompanied by a reactivation of cortical and subcortical areas that have been active during encoding. This neural reinstatement is stronger during retrieval of pain-associated material compared with other unpleasant events. In this functional magnetic resonance imaging study, we investigated the differences in neural reinstatement during recognition of visual stimuli that had been paired with face or hand pain during memory encoding. Body site-specific neural reinstatement was tested in 23 healthy young volunteers who performed a visual categorization and a surprise recognition task. Our data shows increased neural reinstatement in task-specific and encoding-related areas, such as the parahippocampus (left: x = -26, y = -30, z = -18, t = 4.11; right: x = 26, y = -38, z = -6, t = 4.36), precuneus (x = 2, y = -56, z = 2, t = 3.77), fusiform gyrus (left: x = -24, y = -26, z = -20, t = 5.41; right: x = 18, y = -58, z = -14, t = 4.52), and amygdala (x = -34, y = -4, z = -20, t = 4.49) for pictures that were previously presented with face compared with hand pain. These results correlated with the individual's recognition confidence, although recognition rates did not differ between the conditions. Functional connectivity was increased between the amygdala and parahippocampus (x = 34, y = -10, z = -28, t = 5.13) for pictures that had previously been paired with face compared with hand pain. Our results were positively correlated with pain-related fear, represented by neural activation in the thalamus (x = -14, y = -35, z = 4, t = 3.54). The reported results can be interpreted as compensatory resource activation and support the notion of a stronger affective component of face compared with hand pain, potentially in line with its greater biological relevance. PERSPECTIVE: This study demonstrates neural reinstatement of face pain-related information, which might be related to the increased biological and affective component of face pain compared with pain on the extremities. Our results might contribute to the understanding of the development and prevalence of head and face pain conditions.

Probabilistic TFCE: A generalized combination of cluster size and voxel intensity to increase statistical power

The threshold-free cluster enhancement (TFCE) approach integrates cluster information into voxel-wise statistical inference to enhance detectability of neuroimaging signal. Despite the significantly increased sensitivity, the application of TFCE is limited by several factors: (i) generalisation to data structures, like brain network connectivity data is not trivial, (ii) TFCE values are in an arbitrary unit, therefore, P-values can only be obtained by a computationally demanding permutation-test. Here, we introduce a probabilistic approach for TFCE (pTFCE), that gives a simple general framework for topology-based belief boosting. The core of pTFCE is a conditional probability, calculated based on Bayes' rule, from the probability of voxel intensity and the threshold-wise likelihood function of the measured cluster size. In this paper, we provide an estimation of these distributions based on Gaussian Random Field theory. The conditional probabilities are then aggregated across cluster-forming thresholds by a novel incremental aggregation method. pTFCE is validated on simulated and real fMRI data. The results suggest that pTFCE is more robust to various ground truth shapes and provides a stricter control over cluster "leaking" than TFCE and, in many realistic cases, further improves its sensitivity. Correction for multiple comparisons can be trivially performed on the enhanced P-values, without the need for permutation testing, thus pTFCE is well-suitable for the improvement of statistical inference in any neuroimaging workflow. Implementation of pTFCE is available at https://spisakt.github.io/pTFCE.