Neuroimaging of Pain: Human Evidence and Clinical Relevance of Central Nervous System Processes and Modulation

Pediatric Neural Changes to Physical and Emotional Pain After Intensive Interdisciplinary Pain Treatment: A Pilot Study

Brain areas activated during pain can contribute to enhancing or reducing the pain experience, showing a potential connection between chronic pain and the neural response to pain in adolescents and youth. This study examined changes in brain activation associated with experiencing physical pain, and the observation of physical and emotional pain in others, by using functional magnetic resonance imaging (fMRI) before and after intensive interdisciplinary pain treatment (IIPT). Eighteen youth (age 14 to 18) with widespread chronic pain completed fMRI testing before and after IIPT to assess changes in brain activation in response to physical and emotional pain. Broadly, brain activation changes were observed in frontal, somatosensory, and limbic regions. These changes suggest improvements in descending pain modulation via thalamus and caudate, and the different pattern of brain activation after treatment suggests better discrimination between physical and emotional pain. Brain activation changes were also correlated with improvements in clinical outcomes of catastrophizing (reduced activation in right caudate, right mid-cingulate, and postcentral gyrus) and pain-related disability (increased activation in precentral gyrus, left hippocampus, right middle occipital cortex, and left superior frontal gyrus). These changes support interpretation that reduced brain protective responses to pain were associated with treatment-related improvements. This pilot study highlights the need for larger trials designed to better understand the brain mechanisms involved in pediatric widespread pain treatment.

Prognostic models for chronic postsurgical pain-Current developments, trends, and challenges

PURPOSE OF REVIEW

Prognostic models for chronic postsurgical pain (CPSP) aim to predict the likelihood for development and severity of CPSP in individual patients undergoing surgical procedures. Such models might provide valuable information for healthcare providers, allowing them to identify patients at higher risk and implement targeted interventions to prevent or manage CPSP effectively. This review discusses the latest developments of prognostic models for CPSP, their challenges, limitations, and future directions.

RECENT FINDINGS

Numerous studies have been conducted aiming to develop prognostic models for CPSP using various perioperative factors. These include patient-related factors like demographic variables, preexisting pain conditions, psychosocial aspects, procedure-specific characteristics, perioperative analgesic strategies, postoperative complications and, as indicated most recently, biomarkers. Model generation, however, varies and performance and accuracy differ between prognostic models for several reasons and validation of models is rather scarce.

SUMMARY

Precise methodology of prognostic model development needs advancements in the field of CPSP. Development of more accurate, validated and refined models in large-scale cohorts is needed to improve reliability and applicability in clinical practice and validation studies are necessary to further refine and improve the performance of prognostic models for CPSP.

Aberrant Intrinsic Brain Network Functional Connectivity During a Face-Matching Task in Women Diagnosed With Premenstrual Dysphoric Disorder

BACKGROUND

Premenstrual dysphoric disorder (PMDD) is characterized by affective, cognitive, and physical symptoms, suggesting alterations at the brain network level. Women with PMDD demonstrate aberrant discrimination of facial emotions during the luteal phase of the menstrual cycle and altered reactivity to emotional stimuli. However, previous studies assessing emotional task-related brain reactivity using region-of-interest or whole-brain analysis have reported conflicting findings. Therefore, we utilized both region-of-interest task-reactivity and seed-voxel functional connectivity (FC) approaches to test for differences in the default mode network, salience network, and central executive network between women with PMDD and control participants during an emotional-processing task that yields an optimal setup for investigating brain network changes in PMDD.

METHODS

Twenty-four women with PMDD and 27 control participants were classified according to the Daily Record of Severity of Problems. Participants underwent functional magnetic resonance imaging scans while completing the emotional face-matching task during the midfollicular and late-luteal phases of their menstrual cycle.

RESULTS

No significant between-group differences in brain reactivity were found using region-of-interest analysis. In the FC analysis, a main effect of diagnosis was found showing decreased default mode network connectivity, increased salience network connectivity, and decreased central executive network connectivity in women with PMDD compared with control participants. A significant interaction between menstrual cycle phase and diagnosis was found in the central executive network for right posterior parietal cortex and left inferior lateral occipital cortex connectivity. A post hoc analysis revealed stronger FC during the midfollicular than the late-luteal phase of PMDD.

CONCLUSIONS

Aberrant FC in the 3 brain networks involved in PMDD may indicate vulnerability to experience affective and cognitive symptoms of the disorder.

Pain chronification impacts whole-brain functional connectivity in women with hip osteoarthritis during pain stimulation

OBJECTIVE

Previous neuroimaging studies have shown that patients with chronic pain display altered functional connectivity across distributed brain areas involved in the processing of nociceptive stimuli. The aim of the present study was to investigate how pain chronification modulates whole-brain functional connectivity during evoked clinical and tonic pain.

METHODS

Patients with osteoarthritis of the hip (n = 87) were classified into 3 stages of pain chronification (Grades I-III, Mainz Pain Staging System). Electroencephalograms were recorded during 3 conditions: baseline, evoked clinical hip pain, and tonic cold pain (cold pressor test). The effects of both factors (recording condition and pain chronification stage) on the phase-lag index, as a measure of neuronal connectivity, were examined for different frequency bands.

RESULTS

In women, we found increasing functional connectivity in the low-frequency range (delta, 0.5-4 Hz) across pain chronification stages during evoked clinical hip pain and tonic cold pain stimulation. In men, elevated functional connectivity in the delta frequency range was observed in only the tonic cold pain condition.

CONCLUSIONS

Across pain chronification stages, we found that widespread cortical networks increase their synchronization of delta oscillations in response to clinical and experimental nociceptive stimuli. In view of previous studies relating delta oscillations to salience detection and other basic motivational processes, our results hint at these mechanisms playing an important role in pain chronification, mainly in women.

Towards data-driven biopsychosocial classification of non-specific chronic low back pain: a pilot study

The classification of non-specific chronic low back pain (CLBP) according to multidimensional data could guide clinical management; yet recent systematic reviews show this has not been attempted. This was a prospective cross-sectional study of participants with CLBP (n = 21) and age-, sex- and height-matched pain-free controls (n = 21). Nervous system, lumbar spinal tissue and psychosocial factors were collected. Dimensionality reduction was followed by fuzzy c-means clustering to determine sub-groups. Machine learning models (Support Vector Machine, k-Nearest Neighbour, Naïve Bayes and Random Forest) were used to determine the accuracy of classification to sub-groups. The primary analysis showed that four factors (cognitive function, depressive symptoms, general self-efficacy and anxiety symptoms) and two clusters (normal versus impaired psychosocial profiles) optimally classified participants. The error rates in classification models ranged from 4.2 to 14.2% when only CLBP patients were considered and increased to 24.2 to 37.5% when pain-free controls were added. This data-driven pilot study classified participants with CLBP into sub-groups, primarily based on psychosocial factors. This contributes to the literature as it was the first study to evaluate data-driven machine learning CLBP classification based on nervous system, lumbar spinal tissue and psychosocial factors. Future studies with larger sample sizes should validate these findings.

Depressive symptoms moderate functional connectivity within the emotional brain in chronic pain

BACKGROUND

Depressive symptoms are often comorbid with chronic pain. These conditions share aberrant emotion processing and regulation, as well as having common brain networks. However, the relationship between depressive symptoms and chronic pain and the effects on emotional brain function are unclear.

AIMS

The present study aimed to disentangle the effects of chronic pain and depressive symptoms on functional connectivity between regions implicated in both these conditions.

METHOD

Twenty-six individuals with chronic pain (referred to as the pain group) and 32 healthy controls underwent resting-state functional magnetic resonance imaging and completed the Beck Depression Inventory. Main effects of group, depressive symptoms (total severity score) and their interaction on the functional connectivity of three seed regions (the left and right amygdalae and the medial prefrontal cortex; mPFC) with the rest of the brain were evaluated. In cases of significant interaction, moderation analyses were conducted.

RESULTS

The group × depressive symptoms interaction was significantly associated with changes in connectivity between the right amygdala and the mPFC (family-wise error-corrected P-threshold (pFWEc = 0.008). In the moderation analysis, the pain group showed weaker connectivity between these regions at lower levels of depressive symptoms (P = 0.020), and stronger connectivity at higher levels of depressive symptoms (P = 0.003), compared with the healthy controls. In addition, the strength of connectivity decreased in the healthy controls (P = 0.005) and increased in the pain group (P = 0.014) as the severity of depressive symptoms increased.

CONCLUSIONS

Depressive symptoms moderate the impact of chronic pain on emotional brain function, with potential implications for the choice of treatment for chronic pain.

A Comparison of Functional Connectivity in the Human Brainstem and Spinal Cord Associated with Noxious and Innocuous Thermal Stimulation Identified by Means of Functional MRI

The somatosensory system is multidimensional and processes important information for survival, including the experience of pain. The brainstem and spinal cord serve pivotal roles in both transmitting and modulating pain signals from the periphery; although, they are studied less frequently with neuroimaging when compared to the brain. In addition, imaging studies of pain often lack a sensory control condition, failing to differentiate the neural processes associated with pain versus innocuous sensations. The purpose of this study was to investigate neural connectivity between key regions involved in descending modulation of pain in response to a hot, noxious stimulus as compared to a warm, innocuous stimulus. This was achieved with functional magnetic resonance imaging (fMRI) of the brainstem and spinal cord in 20 healthy men and women. Functional connectivity was observed to vary between specific regions across painful and innocuous conditions. However, the same variations were not observed in the period of anticipation prior to the onset of stimulation. Specific connections varied with individual pain scores only during the noxious stimulation condition, indicating a significant role of individual differences in the experience of pain which are distinct from that of innocuous sensation. The results also illustrate significant differences in descending modulation before and during stimulation in both conditions. These findings contribute to a deeper understanding of the mechanisms underlying pain processing at the level of the brainstem and spinal cord, and how pain is modulated.

Reduced Spinal Cord Gray Matter in Patients with Fibromyalgia Using Opioids Long-term

Objective

Chronic pain involves alterations in brain gray matter volume (GMV). Moreover, opioid medications are known to reduce GMV in numerous brain regions involved in pain processing. However, no research has evaluated (1) chronic pain-related GMV alterations in the spinal cord or (2) the effect of opioids on spinal cord GMV. Accordingly, this study evaluated spinal cord GMV in health controls and patients with fibromyalgia who were using and not using opioids long-term.

Methods

We analyzed average C5 - C7 GMV of the spinal cord dorsal and ventral horns in separate female cohorts of healthy controls (HC, n = 30), fibromyalgia patients not using opioids (FMN, n = 31), and fibromyalgia patients using opioids long-term (FMO, n = 27). To assess the effect of group on average dorsal and ventral horn GMV, we conducted a one-way multivariate analysis of covariance.

Results

After controlling for age, we observed a significant effect of group on ventral horn GMV (p = 0.03, η2 = 0.09), and on dorsal horn GMV (p = 0.05, η2 = 0.08). Tukey's posthoc comparisons showed that, compared to HC participants, FMOs had significantly lower ventral (p = 0.01) and dorsal (p = 0.02) GMVs. Among FMOs only, ventral horn GMV was significantly positively associated with pain severity and interference, and both dorsal and ventral GMVs were significantly positively associated with cold pain tolerance.

Conclusion

Long-term opioid use may impact sensory processing in fibromyalgia via gray matter changes within the cervical spinal cord.

Network-specific metabolic and haemodynamic effects elicited by non-invasive brain stimulation

Repetitive transcranial magnetic stimulation (TMS), when applied to the dorsolateral prefrontal cortex (dlPFC), treats depression. Therapeutic effects are hypothesized to arise from propagation of local dlPFC stimulation effects across distributed networks; however, the mechanisms of this remain unresolved. dlPFC contains representations of different networks. As such, dlPFC TMS may exert different effects depending on the network being stimulated. Here, to test this, we applied high-frequency TMS to two nearby dlPFC targets functionally embedded in distinct anti-correlated networks-the default and salience networks- in the same individuals in separate sessions. Local and distributed TMS effects were measured with combined 18fluorodeoxyglucose positron emission tomography and functional magnetic resonance imaging. Identical TMS patterns caused opposing effects on local glucose metabolism: metabolism increased at the salience target following salience TMS but decreased at the default target following default TMS. At the distributed level, both conditions increased functional connectivity between the default and salience networks, with this effect being dramatically larger following default TMS. Metabolic and haemodynamic effects were also linked: across subjects, the magnitude of local metabolic changes correlated with the degree of functional connectivity changes. These results suggest that TMS effects upon dlPFC are network specific. They also invoke putative antidepressant mechanisms of TMS: network de-coupling.

The neurobiology of irritable bowel syndrome

Irritable bowel syndrome (IBS) is the most prevalent disorder of brain-gut interactions that affects between 5 and 10% of the general population worldwide. The current symptom criteria restrict the diagnosis to recurrent abdominal pain associated with altered bowel habits, but the majority of patients also report non-painful abdominal discomfort, associated psychiatric conditions (anxiety and depression), as well as other visceral and somatic pain-related symptoms. For decades, IBS was considered an intestinal motility disorder, and more recently a gut disorder. However, based on an extensive body of reported information about central, peripheral mechanisms and genetic factors involved in the pathophysiology of IBS symptoms, a comprehensive disease model of brain-gut-microbiome interactions has emerged, which can explain altered bowel habits, chronic abdominal pain, and psychiatric comorbidities. In this review, we will first describe novel insights into several key components of brain-gut microbiome interactions, starting with reported alterations in the gut connectome and enteric nervous system, and a list of distinct functional and structural brain signatures, and comparing them to the proposed brain alterations in anxiety disorders. We will then point out the emerging correlations between the brain networks with the genomic, gastrointestinal, immune, and gut microbiome-related parameters. We will incorporate this new information into a systems-based disease model of IBS. Finally, we will discuss the implications of such a model for the improved understanding of the disorder and the development of more effective treatment approaches in the future.

Doctor trustworthiness influences pain and its neural correlates in virtual medical interactions

Trust is an important component of the doctor-patient relationship and is associated with improved patient satisfaction and health outcomes. Previously, we reported that patient feelings of trust and similarity toward their clinician predicted reductions in evoked pain in response to painful heat stimulations. In the present study, we investigated the brain mechanisms underlying this effect. We used face stimuli previously developed using a data-driven computational modeling approach that differ in perceived trustworthiness and superimposed them on bodies dressed in doctors' attire. During functional magnetic resonance imaging, participants (n = 42) underwent a series of virtual medical interactions with these doctors during which they received painful heat stimulation as an analogue of a painful diagnostic procedure. Participants reported increased pain when receiving painful heat stimulations from low-trust doctors, which was accompanied by increased activity in pain-related brain regions and a multivariate pain-predictive neuromarker. Findings suggest that patient trust in their doctor may have tangible impacts on pain and point to a potential brain basis for trust-related reductions in pain through the modulation of brain circuitry associated with the sensory-discriminative and affective-motivational dimensions of pain.

Recent trends in acupuncture for chronic pain: A bibliometric analysis and review of the literature

BACKGROUND

Acupuncture has been increasingly used in patients with chronic pain, yet no bibliometric analysis of acupuncture studies for chronic pain exists.

OBJECTIVES

To investigate the characteristics, hotspots and frontiers of global scientific output in acupuncture research for chronic pain over the past decade.

METHODS

We retrieved publications on acupuncture for chronic pain published from 2011 to 2022 from the Science Citation Index Expanded (SCI-expanded) of the Web of Science Core Collection (WoSCC). The co-occurrence relationships of journals/countries/institutions/authors/keywords were performed using VOSviewer V6.1.2, and CiteSpace V1.6.18 analyzed the clustering and burst analysis of keywords and co-cited references.

RESULTS

A total of 1616 articles were retrieved. The results showed that the number of annual publications on acupuncture for chronic pain has increased over time, with the main types of literature being original articles (1091 articles, 67.5 %) and review articles (351 articles, 21.7 %). China had the most publications (598 articles, 37 %), with Beijing University of Traditional Chinese Medicine (93 articles, 5.8 %) and Evidence-based Complementary and Alternative Medicine ranked first (169 articles, 10.45 %) as the most prolific affiliate and journal, respectively. Liang FR was the most productive author (43 articles), and the article published by Vickers Andrew J in 2012 had the highest number of citations (625 citations). Recently, "acupuncture" and "pain" appeared most frequently. The hot topics in acupuncture for chronic pain based on keywords clustering analysis were experimental design, hot diseases, interventions, and mechanism studies. According to burst analysis, the main research frontiers were functional connectivity (FC), depression, and risk.

CONCLUSION

This study provides an in-depth perspective on acupuncture for chronic pain studies, revealing pivotal points, research hotspots, and research trends. Valuable ideas are provided for future research activities.

Measuring pain and nociception: Through the glasses of a computational scientist. Transdisciplinary overview of methods

In a healthy state, pain plays an important role in natural biofeedback loops and helps to detect and prevent potentially harmful stimuli and situations. However, pain can become chronic and as such a pathological condition, losing its informative and adaptive function. Efficient pain treatment remains a largely unmet clinical need. One promising route to improve the characterization of pain, and with that the potential for more effective pain therapies, is the integration of different data modalities through cutting edge computational methods. Using these methods, multiscale, complex, and network models of pain signaling can be created and utilized for the benefit of patients. Such models require collaborative work of experts from different research domains such as medicine, biology, physiology, psychology as well as mathematics and data science. Efficient work of collaborative teams requires developing of a common language and common level of understanding as a prerequisite. One of ways to meet this need is to provide easy to comprehend overviews of certain topics within the pain research domain. Here, we propose such an overview on the topic of pain assessment in humans for computational researchers. Quantifications related to pain are necessary for building computational models. However, as defined by the International Association of the Study of Pain (IASP), pain is a sensory and emotional experience and thus, it cannot be measured and quantified objectively. This results in a need for clear distinctions between nociception, pain and correlates of pain. Therefore, here we review methods to assess pain as a percept and nociception as a biological basis for this percept in humans, with the goal of creating a roadmap of modelling options.

Pain control based on oscillatory brain activity using transcranial alternating current stimulation: An integrative review

Developing effective tools and strategies to relieve chronic pain is a high-priority scientific and clinical goal. In particular, the brain regions related to pain processing have been investigated as potential targets to relieve pain by non-invasive brain stimulation (NIBS). In addition to elucidating the relationship between pain and oscillatory brain activity, transcranial alternating current stimulation (tACS), which can non-invasively entrain oscillatory brain activity and modulate oscillatory brain communication, has attracted scientific attention as a possible technique to control pain. This review focuses on the use of tACS to relieve pain through the manipulation of oscillatory brain activity and its potential clinical applications. Several studies have reported that tACS on a single brain reduces pain by normalizing abnormal oscillatory brain activity in patients with chronic pain. Interpersonal tACS approaches based on inter-brain synchrony to manipulate inter-brain communication may result in pain relief via prosocial effects. Pain is encoded by the spatiotemporal neural communication that represents the integration of cognitive, emotional-affective, and sensorimotor aspects of pain. Therefore, future studies should seek to identify the pathological oscillatory brain communication in chronic pain as a therapeutic target for tACS. In conclusion, tACS could be effective for re-establishing oscillatory brain activity and assisting social interaction, and it might help develop novel approaches for pain control.

Electroencephalography functional connectivity-A biomarker for painful polyneuropathy

BACKGROUND AND PURPOSE

Advanced analysis of electroencephalography (EEG) data has become an essential tool in brain research. Based solely on resting state EEG signals, a data-driven, predictive and explanatory approach is presented to discriminate painful from non-painful diabetic polyneuropathy (DPN) patients.

METHODS

Three minutes long, 64 electrode resting-state recordings were obtained from 180 DPN patients. The analysis consisted of a mixture of traditional, explanatory and machine learning analyses. First, the 10 functional bivariate connections best differentiating between painful and non-painful patients in each EEG band were identified and the relevant receiver operating characteristic was calculated. Later, those connections were correlated with selected clinical parameters.

RESULTS

Predictive analysis indicated that theta and beta bands contain most of the information required for discrimination between painful and non-painful polyneuropathy patients, with area under the receiver operating characteristic curve values of 0.93 for theta and 0.89 for beta bands. Assessing statistical differences between the average magnitude of functional connectivity values and clinical pain parameters revealed that painful DPN patients had significantly higher cortical functional connectivity than non-painful ones (p = 0.008 for theta and p = 0.001 for alpha bands). Moreover, intra-band analysis of individual significant functional connections revealed a positive correlation with average reported pain in the previous 3 months in all frequency bands.

CONCLUSIONS

Resting state EEG functional connectivity can serve as a highly accurate biomarker for the presence or absence of pain in DPN patients. This highlights the importance of the brain, in addition to the peripheral lesions, in generating the clinical pain picture. This tool can probably be extended to other pain syndromes.

FDG PET Imaging of the Pain Matrix in Neuropathic Pain Model Rats

Pain is an unpleasant subjective experience that is usually modified by complex multidimensional neuropsychological processes. Increasing numbers of neuroimaging studies in humans have characterized the hierarchical brain areas forming a pain matrix, which is involved in the different dimensions of pain components. Although mechanistic investigations have been performed extensively in rodents, the homologous brain regions involved in the multidimensional pain components have not been fully understood in the rodent brain. Herein, we successfully identified several brain regions activated in response to mechanical allodynia in neuropathic pain rat models using an alternative neuroimaging method based on 2-deoxy-2-[¹⁸F]fluoro-d-glucose positron emission tomography (FDG PET) scanning. Regions such as the medial prefrontal cortex, primary somatosensory cortex hindlimb region, and the centrolateral thalamic nucleus were identified. Moreover, brain activity in these regions was positively correlated with mechanical allodynia-related behavioral changes. These results suggest that FDG PET imaging in neuropathic pain model rats enables the evaluation of regional brain activity encoding the multidimensional pain aspect. It could thus be a fascinating tool to bridge the gap between preclinical and clinical investigations.

A Forehead Wearable Sensor for the Objective Measurement of Chronic Pain

Chronic pain impacts one in five Americans and is difficult to manage, costing ~USD 600 billion annually. The subjective experience of pain is a complex processing of central nervous system input. Recent advances in magnetic resonance imaging revealed the prefrontal cortex as vital to the perception of pain and that changes in the cerebral hemodynamics can be used to detect painful sensations. Current pain monitoring is dependent on the subjective rating provided by patients and is limited to a single time point. We have developed a biomarker for the objective, real-time and continuous chronic pain assessment using proprietary algorithms termed ROPA and cerebral optical spectrometry. Using a forehead sensor, the cerebral optical spectrometry data were collected in two clinical sites from 41 patients (19 and 22, respectively, from sites 1 and 2), who elected to receive an epidural steroid injection for the treatment of chronic pain. Patients rated their pain on a numeric rating scale, ranging from 0-10, which were used to validate the ROPA objective pain scoring. Multiple time points, including pre- and post-procedure were recorded. The steroid injection was performed per standard medical practice. There was a significant correlation between the patient's reported numeric rating scale and ROPA, for both clinical sites (Overall ~0.81). Holding the subjective pain ratings on a numeric rating scale as ground truth, we determined that the area under the receiver operator curves for both sites revealed at least good (AUC: 64%) to excellent (AUC > 98%) distinctions between clinically meaningful pain severity differentiations (no/mild/moderate/severe). The objective measure of chronic pain (ROPA) determined using cerebral optical spectrometry significantly correlated with the subjective pain scores reported by the subjects. This technology may provide a useful method of detection for the objective and continuous monitoring and treatment of patients with chronic pain, particularly in clinical circumstances where direct assessment is not available, or to complement the patient-reported pain scores.

Replication of neural responses to monetary incentives and exploration of reward-influenced network connectivity in fibromyalgia

Neuroimaging research has begun to implicate alterations of brain reward systems in chronic pain. Previously, using functional magnetic resonance imaging (fMRI) and a monetary incentive delay (MID) task, Martucci et al. (2018) showed that neural responses to reward anticipation and outcome are altered in fibromyalgia. In the present study, we aimed to test the replicability of these altered neural responses to reward in a separate fibromyalgia cohort. In addition, the present study was conducted at a distinct U.S. location but involved a similar study design. For the present study, 20 patients with fibromyalgia and 20 healthy controls participated in MID task fMRI scan procedures and completed clinical/psychological questionnaires. fMRI analyses comparing patient and control groups revealed a consistent trend of main results which were largely similar to the prior reported results. Specifically, in the replication fibromyalgia cohort, medial prefrontal cortex (MPFC) response was reduced during gain anticipation and was increased during no-loss (non-punishment) outcome compared to controls. Also consistent with previous findings, the nucleus accumbens response to gain anticipation did not differ in patients vs. controls. Further, results from similarly-designed behavioral, correlational, and exploratory analyses were complementary to previous findings. Finally, a novel network-based functional connectivity analysis of the MID task fMRI data across patients vs. controls implied enhanced connectivity within the default mode network in participants with fibromyalgia. Together, based on replicating prior univariate results and new network-based functional connectivity analyses of MID task fMRI data, we provide further evidence of altered brain reward responses, particularly in the MPFC response to reward outcomes, in patients with fibromyalgia.

Mindfulness-Based Stress Reduction, Cognitive Behavioral Therapy, and Acupuncture in Chronic Low Back Pain: Protocol for Two Linked Randomized Controlled Trials

BACKGROUND

Nonpharmacologic mind-body therapies have demonstrated efficacy in low back pain. However, the mechanisms underlying these therapies remain to be fully elucidated.

OBJECTIVE

In response to these knowledge gaps, the Stanford Center for Low Back Pain-a collaborative, National Institutes of Health P01-funded, multidisciplinary research center-was established to investigate the common and distinct biobehavioral mechanisms of three mind-body therapies for chronic low back pain: cognitive behavioral therapy (CBT) that is used to treat pain, mindfulness-based stress reduction (MBSR), and electroacupuncture. Here, we describe the design and implementation of the center structure and the associated randomized controlled trials for characterizing the mechanisms of chronic low back pain treatments.

METHODS

The multidisciplinary center is running two randomized controlled trials that share common resources for recruitment, enrollment, study execution, and data acquisition. We expect to recruit over 300 chronic low back pain participants across two projects and across different treatment arms within each project. The first project will examine pain-CBT compared with MBSR and a wait-list control group. The second project will examine real versus sham electroacupuncture. We will use behavioral, psychophysical, physical measure, and neuroimaging techniques to characterize the central pain modulatory and emotion regulatory systems in chronic low back pain at baseline and longitudinally. We will characterize how these interventions impact these systems, characterize the longitudinal treatment effects, and identify predictors of treatment efficacy.

RESULTS

Participant recruitment began on March 17, 2015, and will end in March 2023. Recruitment was halted in March 2020 due to COVID-19 and resumed in December 2021.

CONCLUSIONS

This center uses a comprehensive approach to study chronic low back pain. Findings are expected to significantly advance our understanding in (1) the baseline and longitudinal mechanisms of chronic low back pain, (2) the common and distinctive mechanisms of three mind-body therapies, and (3) predictors of treatment response, thereby informing future delivery of nonpharmacologic chronic low back pain treatments.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02503475; https://clinicaltrials.gov/ct2/show/NCT02503475.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/37823.

Altered brain functional activity and connectivity in bone metastasis pain of lung cancer patients: A preliminary resting-state fMRI study

Bone metastasis pain (BMP) is one of the most prevalent symptoms among cancer survivors. The present study aims to explore the brain functional activity and connectivity patterns in BMP of lung cancer patients preliminarily. Thirty BMP patients and 33 healthy controls (HCs) matched for age and sex were recruited from inpatients and communities, respectively. All participants underwent fMRI data acquisition and pain assessment. Low-frequency fluctuations (ALFF) and regional homogeneity (ReHo) were applied to evaluate brain functional activity. Then, functional connectivity (FC) was calculated for the ALFF- and ReHo-identified seed brain regions. A two-sample t-test or Manny–Whitney U-test was applied to compare demographic and neuropsychological data as well as the neuroimaging indices according to the data distribution. A correlation analysis was conducted to explore the potential relationships between neuroimaging indices and pain intensity. Receiver operating characteristic curve analysis was applied to assess the classification performance of neuroimaging indices in discriminating individual subjects between the BMP patients and HCs. No significant intergroup differences in demographic and neuropsychological data were noted. BMP patients showed reduced ALFF and ReHo largely in the prefrontal cortex and increased ReHo in the bilateral thalamus and left fusiform gyrus. The lower FC was found within the prefrontal cortex. No significant correlation between the neuroimaging indices and pain intensity was observed. The neuroimaging indices showed satisfactory classification performance between the BMP patients and HCs, and the combined ALFF and ReHo showed a better accuracy rate (93.7%) than individual indices. In conclusion, altered brain functional activity and connectivity in the prefrontal cortex, fusiform gyrus, and thalamus may be associated with the neuropathology of BMP and may represent a potential biomarker for classifying BMP patients and healthy controls.

Evaluation by Survival Analysis of Cold Pain Tolerance in Patients with Fibromyalgia and Opioid Use

Purpose

The cold pressor test (CPT) is a clinical pain research method used to measure cold pain tolerance. During this test, participants immerse an extremity (ie, hand or foot) into cold water for as long as tolerable. The duration of the test (traditionally up to an experimentally imposed cut-off at 2 minutes) indicates the amount of cold pain tolerance by the participant. Prior research studies have investigated cold pain tolerance in patients with chronic pain. However, few of these studies have used survival analysis, which allows for proper handling of data censoring and is therefore, an optimal statistical method for CPT data analysis. The goal of the present study was to use survival analysis to evaluate cold pain tolerance in patients with fibromyalgia. Furthermore, we aimed to model relationships between psychological and clinical variables as well as opioid medication use and cold pain tolerance.

Patients and Methods

A total of 85 patients with fibromyalgia (42 who were taking opioids) and 47 healthy pain-free controls provided CPT and questionnaire data (collected across 2 study sites) for a case-control study. We used survival analysis using Cox regression to evaluate group differences (patients vs controls) in cold pain tolerance and to evaluate cold pain tolerance relationships with psychological, clinical, and medication use.

Results

As compared to healthy controls, patients with fibromyalgia exhibited significantly lower CPT survival (HR = 2.17, 95% CI: [1.42, 3.31], p = 0.00035). As indicated by Cox regression models, the significant group difference in CPT survival did not relate to our selected psychological and clinical measures (p > 0.05). The groups of non-opioid-taking patients and healthy controls showed consistent CPT survival across study sites. However, patients taking opioid pain medications showed differences in CPT survival across study sites.

Conclusion

By using survival analysis, an optimal method for time-to-event pain measures such as the CPT, we confirmed previously identified reductions in cold pain tolerance in patients with fibromyalgia. While our selected psychological and clinical measures were not significantly associated with cold pain tolerance, our data suggest that opioid medication use may impart greater cold pain tolerance in some patients.

Chronic back pain sub-grouped via psychosocial, brain and physical factors using machine learning

Chronic back pain (CBP) is heterogenous and identifying sub-groups could improve clinical decision making. Machine learning can build upon prior sub-grouping approaches by using a data-driven approach to overcome clinician subjectivity, however, only binary classification of pain versus no-pain has been attempted to date. In our cross-sectional study, age- and sex-matched participants with CBP (n = 4156) and pain-free controls (n = 14,927) from the UkBioBank were included. We included variables of body mass index, depression, loneliness/social isolation, grip strength, brain grey matter volumes and functional connectivity. We used fuzzy c-means clustering to derive CBP sub-groups and Support Vector Machine (SVM), Naïve Bayes, k-Nearest Neighbour (kNN) and Random Forest classifiers to determine classification accuracy. We showed that two variables (loneliness/social isolation and depression) and five clusters were optimal for creating sub-groups of CBP individuals. Classification accuracy was greater than 95% for when CBP sub-groups were assessed only, while misclassification in CBP sub-groups increased to 35-53% across classifiers when pain-free controls were added. We showed that individuals with CBP could sub-grouped and accurately classified. Future research should optimise variables by including specific spinal, psychosocial and nervous system measures associated with CBP to create more robust sub-groups that are discernible from pain-free controls.

Pain, depression, and poor quality of life in chronic pancreatitis: Relationship with altered brain metabolites

BACKGROUND

To evaluate if altered brain metabolites are connected to pain, depression and affective responses in CP.

METHODS

In this prospective study we evaluated pain characteristics, QOL (EORTC QLQc30+PAN28), depression (Beck depression inventory [BDI] II) in 558 patients with CP and 67 healthy controls. Brain metabolites were evaluated using magnetic resonance spectroscopy (MRS) in 49 patients and 5 healthy controls. We measured plasma metabolites using gas chromatography-mass spectrometry (GC-MS/MS). Relationship between metabolomic alterations, pain, depression and QOL components were assessed using statistical/bioinformatics methods. Benjamini-Hochberg FDR correction was applied for multiple testing.

RESULTS

261 (46.8%) patients had depression compared to 5 (7.5%) among healthy controls [n = 67](p < 0.0001). Risk [OR (95% CI) of developing depression in the presence of pain was 1.9 (1.33-1.68); p = 0.0004. The depression scores correlated negatively with functional components and positively with symptom components of EORTC QLQ30. Significant negative correlation, though based on a small sample size, was observed between N-acetyl aspartate in the left hippocampus and choline in the left prefrontal cortex with emotional and cognitive functions. PLS-DA modelling revealed significant alteration in the plasma metabolomic profile among patients with CP who had depression. Six metabolites were significantly different between CP with depression and healthy controls, of which glycine contributed most significantly to the PLS-DA model (VIP score of 3.5).

CONCLUSIONS

A significant proportion of patients with CP develops depression that correlate with poor QOL functions. Pain, depression, and emotional components of QOL in patients with CP correlated with N-acetyl aspartate and choline in the left hippocampus and left prefrontal cortex of the brain.

Altered Functional Connectivity in Pain-Related Brain Regions and Its Correlation with Pain Duration in Bone Metastasis with Cancer Pain

Bone metastatic pain is thought to be a severe type of cancer pain that has refractory characteristics and a long duration. This study is aimed at exploring the brain functional connectivity (FC) pattern in lung cancer patients with bone metastatic pain. In this study, 27 lung cancer patients with bone metastatic pain (CP+), 27 matched lung cancer patients without pain-related complaints (CP-), and 27 matched healthy controls (HC) were recruited. All participants underwent fMRI data acquisition and clinical assessments. One-way ANOVA or a Mann-Whitney U test was applied to compare clinical data according to data distribution. Seventeen hypothesis-driven pain-related brain regions were selected as regions of interest (ROIs). FC values among pain-related brain regions across the three groups were computed by using ROI-ROI functional connectivity analysis. ANCOVA with a post hoc test was applied to compare FC differences among the three groups. p < 0.05 indicated statistical significance. Correlation analysis was conducted to explore the potential relationship between the FC values and clinical characteristics. Except for years of education, no significant differences were revealed among the three groups in age, gender, or neuropsychological assessment. In the CP+ group, FC alterations were mainly concentrated in the dorsal lateral prefrontal cortex (DLPFC), anterior cingulate cortex (ACC), secondary somatosensory cortex (SII), and amygdala compared to the CP- group. Among these brain regions with statistical differences, FC between the right DLPFC and the right ACC showed a positive correlation with the duration of cancer pain in the CP+ group. In addition, in the CP- group, altered FC was found in the bilateral SII, ACC, and thalamus compared to the HC group. Altered FC in pain-related brain regions may be a brain pattern of bone metastatic pain and may be associated with the long duration of cancer pain.

Somatosensory Profiles Differentiate Pain and Psychophysiological Symptoms Among Young Adults With Irritable Bowel Syndrome: A Cluster Analysis

OBJECTIVE

The aim of this study was to investigate if somatosensory profiles can differentiate pain and psychophysiological symptoms among young adults with irritable bowel syndrome (IBS).

METHODS

We performed a cluster analysis of data collected from a randomized clinical trial of 80 IBS patients and 21 age-matched healthy controls (HCs) to stratify pain and symptoms among young adults with IBS by their peripheral sensory profiles. Data of quantitative sensory testing and IBS-related pain and symptoms were collected at baseline and 6-week and 12-week follow-ups.

RESULTS

Using the K-means method, IBS patients were classified into 2 clusters, the "IBS normal threshold" (IBS-NT) and the "IBS increased threshold" (IBS-IT). The IBS-NT cluster had a similar pain threshold as the HCs, and the IBS-IT cluster had an increased threshold of somatic pain perception (lower cold pain threshold, higher heat pain threshold, and higher pressure pain threshold, all P<0.001) than HCs. Compared with the IBS-NT cluster, the IBS-IT cluster reported higher levels of IBS-related pain intensity, anxiety, fatigue, and sleep disturbance over the 3 visits (all P<0.05).

DISCUSSION

Young adults with IBS fell into 2 clusters, one with a similar sensory threshold as the HCs and another with an increased pain threshold, who reported higher pain intensity and more severe symptoms. Somatic sensory profiles should be integrated into further personalized self-management intervention among patients with IBS.

Brain structure, psychosocial, and physical health in acute and chronic back pain: a UK Biobank study

ABSTRACT

Brain structure, psychosocial, and physical factors underpin back pain conditions; however, less is known about how these factors differ based on pain duration and location. We examined, cross-sectionally, 11,106 individuals from the UK Biobank who (1) were pain-free (n = 5616), (2) had acute back pain (n = 1746), (3) had chronic localised back pain (CBP; n = 1872), or (4) had chronic back pain and additional chronic pain sites (CWP; n = 1872). We found differences in structural brain measures in the chronic pain groups alone. Both CBP and CWP groups had lower primary somatosensory cortex {CBP mean difference (MD) (95% confidence interval [CI]): -250 (-393, -107) mm3, P < 0.001; CWP: -170 (-313, -27)mm3, P = 0.011} and higher caudate gray matter volumes (CBP: 127 [38,216]mm3, P = 0.001; CWP: 122 [33,210]mm3, P = 0.002) compared with pain-free controls. The CBP group also had a lower primary motor cortex volume (-215 [-382, -50]mm3, P = 0.005), whereas the CWP group had a lower amygdala gray matter volume (-27 [-52, -3]mm3, P = 0.021) compared with pain-free controls. Differences in gray matter volumes in some regions may be moderated by sex and body mass index. Psychosocial factors and body mass index differed between all groups and affected those with widespread pain the most (all, P < 0.001), whereas grip strength was only compromised in individuals with widespread pain (-1.0 [-1.4, -0.5] kg, P < 0.001) compared with pain-free controls. Longitudinal research is necessary to confirm these interactions to determine the process of pain development in relation to assessed variables and covariates. However, our results suggest that categorised pain duration and the number of pain sites warrant consideration when assessing markers of brain structure, psychosocial, and physical health.

Chronic Musculoskeletal Pain Moderates the Association between Sleep Quality and Dorsostriatal-Sensorimotor Resting State Functional Connectivity in Community-Dwelling Older Adults

Aging is associated with poor sleep quality and greater chronic pain prevalence, with age-related changes in brain function as potential underlying mechanisms. Objective. The following cross-sectional study aimed to determine whether self-reported chronic musculoskeletal pain in community-dwelling older adults moderates the association between sleep quality and resting state functional brain connectivity (rsFC). Methods. Community-dwelling older individuals (mean age = 73.29 years) part of the NEPAL study who completed the Pittsburg Sleep Quality Index (PSQI) and a rsFC scan were included (n = 48) in the present investigation. To that end, we tested the effect of chronic pain-by-PSQI interaction on rsFC among atlas-based brain regions-of-interest, controlling for age and sex. Results and Discussion. A significant network connecting the bilateral putamen and left caudate with bilateral precentral gyrus, postcentral gyrus, and juxtapositional lobule cortex, survived global multiple comparisons (FDR; q < 0.05) and threshold-free network-based-statistics. Greater PSQI scores were significantly associated with greater dorsostriatal-sensorimotor rsFC in the no-pain group, suggesting that a state of somatomotor hyperarousal may be associated with poorer sleep quality in this group. However, in the pain group, greater PSQI scores were associated with less dorsostriatal-sensorimotor rsFC, possibly due to a shift of striatal functions toward regulation sensorimotor aspects of the pain experience, and/or aberrant cortico-striatal loops in the presence of chronic pain. This preliminary investigation advances knowledge about the neurobiology underlying the associations between chronic pain and sleep in community-dwelling older adults that may contribute to the development of effective therapies to decrease disability in geriatric populations.

Amygdala functional connectivity mediates the association between catastrophizing and threat-safety learning in youth with chronic pain

ABSTRACT

There is a need to identify brain connectivity alterations predictive of transdiagnostic processes that may confer vulnerability for affective symptomology. Here, we tested whether amygdala resting-state functional connectivity (rsFC) mediated the relationship between catastrophizing (negative threat appraisals and predicting poorer functioning) and altered threat-safety discrimination learning (critical to flexibly adapt to new and changing environments) in adolescents with persistent pain. We examined amygdala rsFC in 46 youth with chronic pain and 29 healthy peers (age M = 15.8, SD = 2.9; 64 females) and its relationship with catastrophizing and threat-safety learning. We used a developmentally appropriate threat-safety learning paradigm and performed amygdala seed-based rsFC and whole-brain mediation analyses. Patients exhibited enhanced connectivity between the left amygdala and right supramarginal gyrus (SMG) (cluster-level P-FDR < 0.05), whereas right amygdala rsFC showed no group differences. Only in patients, elevated catastrophizing was associated with facilitated threat-safety learning (CS+>CS-; rp = 0.49, P = 0.001). Furthermore, in patients, elevated catastrophizing was associated with reduced left amygdala connectivity with SMG / parietal operculum, and increased left amygdala connectivity with hippocampus, dorsal striatum, paracingulate, and motor regions (P < 0.001). In addition, blunted left amygdala rsFC with right SMG/parietal operculum mediated the association between catastrophizing and threat-safety learning (P < 0.001). To conclude, rsFC between the left amygdala (a core emotion hub) and inferior parietal lobe (involved in appraisal and integration of bodily signals and attentional reorienting) explains associations between daily-life relevant catastrophizing and threat-safety learning. Findings provide a putative model for understanding pathophysiology involved in core psychological processes that cut across diagnoses, including disabling pain, and are relevant for their etiology.

Supraspinal Mechanisms Underlying Ocular Pain

Supraspinal mechanisms of pain are increasingly understood to underlie neuropathic ocular conditions previously thought to be exclusively peripheral in nature. Isolating individual causes of centralized chronic conditions and differentiating them is critical to understanding the mechanisms underlying neuropathic eye pain and ultimately its treatment. Though few functional imaging studies have focused on the eye as an end-organ for the transduction of noxious stimuli, the brain networks related to pain processing have been extensively studied with functional neuroimaging over the past 20 years. This article will review the supraspinal mechanisms that underlie pain as they relate to the eye.

Early Fractional Amplitude of Low Frequency Fluctuation Can Predict the Efficacy of Transcutaneous Auricular Vagus Nerve Stimulation Treatment for Migraine Without Aura

Migraine is a common primary headache disorder. Transcutaneous auricular vagus nerve stimulation (taVNS) has been verified to be effective in patients with migraine without aura (MWoA). However, there are large interindividual differences in patients’ responses to taVNS. This study aimed to explore whether pretreatment fractional amplitude of low frequency fluctuation (fALFF) features could predict clinical outcomes in MWoA patients after 4-week taVNS. Sixty MWoA patients and sixty well-matched healthy controls (HCs) were recruited, and migraineurs received 4-week taVNS treatment. Resting-state functional magnetic resonance imaging (rs-fMRI) data were collected, and the significant differences of fALFF were detected between MWoA patients and HCs using two-sample t-test. A mask of these significant regions was generated and used for subsequent analysis. The abnormal fALFF in the mask was used to predict taVNS efficacy for MWoA using a support vector regression (SVR) model combining with feature select of weight based on the LIBSVM toolbox. We found that (1) compared with HCs, MWoA patients exhibited increased fALFF in the left thalamus, left inferior parietal gyrus (IPG), bilateral precentral gyrus (PreCG), right postcentral gyrus (PoCG), and bilateral supplementary motor areas (SMAs), but decreased in the bilateral precuneus and left superior frontal gyrus (SFG)/medial prefrontal cortex (mPFC); (2) after 4-week taVNS treatment, the fALFF values significantly decreased in these brain regions based on the pretreatment comparison. Importantly, the decreased fALFF in the bilateral precuneus was positively associated with the reduction in the attack times (r = 0.357, p = 0.005, Bonferroni correction, 0.05/5), whereas the reduced fALFF in the right PoCG was negatively associated with reduced visual analog scale (VAS) scores (r = −0.267, p = 0.039, uncorrected); (3) the SVR model exhibited a good performance for prediction (r = 0.411, p < 0.001),which suggests that these extracted fALFF features could be used as reliable biomarkers to predict the treatment response of taVNS for MWoA patients. This study demonstrated that the baseline fALFF features have good potential for predicting individualized treatment response of taVNS in MWoA patients, and those weight brain areas are mainly involved in the thalamocortical (TC) circuits, default mode network (DMN), and descending pain modulation system (DPMS). This will contribute to well understanding the mechanism of taVNS in treating MWoA patients and may help to screen ideal patients who respond well to taVNS treatment.

Differences in Structural Brain Characteristics Between Individuals with Chronic Nonspecific Neck Pain and Asymptomatic Controls: A Case–Control Study

Background

Neck pain is a prevalent and costly problem, but its underlying mechanisms are poorly understood. Neuroimaging studies show alterations in brain morphometry in chronic musculoskeletal pain, but reports on neck pain are scarce.

Objective

This study investigates (1) differences in brain morphometry between individuals with chronic nonspecific neck pain and asymptomatic individuals and (2) associations between brain morphometry and patient-reported outcomes.

Methods

Sixty-three participants (33 pain, 11 female, mean [SD] age 35 [10] years; 30 control, 12 female, age 35 [11] years) underwent magnetic resonance imaging. Brain regions of interest (ROIs) were determined a priori, outcomes included cortical thickness and volume. Between-group differences were determined using cluster-wise correction for multiple comparisons and analyses of pain-related ROIs.

Results

Between-group differences in volume were identified in the precentral, frontal, occipital, parietal, temporal, and paracentral cortices. ROI analyses showed that parahippocampal cortical thickness was larger in the neck pain group (p=0.015, 95% CI: −0.27 to −0.03). Moderate to strong associations between volume and thickness of the cingulate cortex, prefrontal cortex, and temporal lobe and neck pain duration, pain intensity, and neck disability were identified (p-values 0.006 to 0.048).

Conclusion

Alterations in brain morphology that are associated with clinical characteristics inform the mechanisms underlying chronic nonspecific neck pain and may guide the development of more effective treatment approaches.

Brain Structural Changes during Juvenile Fibromyalgia: Relationships with Pain, Fatigue and Functional Disability

Objective

Juvenile fibromyalgia (FM) is a prevalent chronic pain condition affecting children and adolescents worldwide during a critical period of brain development. To date, no published studies have addressed the pathophysiology of juvenile FM. This study was undertaken to characterize gray matter volume (GMV) alterations in juvenile FM patients for the first time, and to investigate their functional and clinical relevance.

Methods

Thirty‐four female adolescents with juvenile FM and 38 healthy adolescents underwent a structural magnetic resonance imaging examination and completed questionnaires assessing core juvenile FM symptoms. Using voxel‐based morphometry, we assessed between‐group GMV differences and associations between GMV and functional disability, fatigue, and pain interference in juvenile FM. We also studied whether validated brain patterns predicting pain, cognitive control, or negative emotion were amplified/attenuated in juvenile FM patients and whether structural alterations reported in adult FM were replicated in adolescents with juvenile FM.

Results

Compared to controls, juvenile FM patients showed GMV reductions in the anterior midcingulate cortex (aMCC) region (family‐wise error corrected P [P_FWE‐corr] = 0.04; estimated with threshold‐free cluster enhancement [TFCE]; n = 72) associated with pain. Within the juvenile FM group, patients reporting higher functional disability had larger GMV in inferior frontal regions (P_FWE‐corr = 0.006; TFCE estimated; n = 34) linked to affective, self‐referential, and language‐related processes. Last, GMV reductions in juvenile FM showed partial overlap with findings in adult FM, specifically for the anterior/posterior cingulate cortices (P = 0.02 and P = 0.03, respectively; n = 72).

Conclusion

Pain‐related aMCC reductions may be a structural hallmark of juvenile FM, whereas alterations in regions involved in emotional, self‐referential, and language‐related processes may predict disease impact on patients’ well‐being. The partial overlap between juvenile and adult FM findings strengthens the importance of early symptom identification and intervention to prevent the transition to adult forms of the disease.

Genetic basis to structural grey matter associations with chronic pain

Structural neuroimaging studies of individuals with chronic pain conditions have often observed decreased regional grey matter at a phenotypic level. However, it is not known if this association can be attributed to genetic factors. Here we employed a novel integrative data-driven and hypothesis-testing approach to determine whether there is a genetic basis to grey matter morphology differences in chronic pain. Using publicly available genome-wide association study summary statistics for regional chronic pain conditions (n = 196 963) and structural neuroimaging measures (n = 19 629-34 000), we applied bivariate linkage disequilibrium-score regression and latent causal variable analyses to determine the genetic correlations (rG) and genetic causal proportion (GCP) between these complex traits, respectively. Five a priori brain regions (i.e. prefrontal cortex, cingulate cortex, insula, thalamus and superior temporal gyrus) were selected based on systematic reviews of grey matter morphology studies in chronic pain. Across this evidence-based selection of five brain regions, 10 significant negative genetic correlations (out of 369) were found (false discovery rate < 5%), suggesting a shared genetic basis to both reduced regional grey matter morphology and the presence of chronic pain. Specifically, negative genetic correlations were observed between reduced insula grey matter morphology and chronic pain in the abdomen (mean insula cortical thickness), hips (left insula volume) and neck/shoulders (left and right insula volume). Similarly, a shared genetic basis was found for reduced posterior cingulate cortex volume in chronic pain of the hip (left and right posterior cingulate), neck/shoulder (left posterior cingulate) and chronic pain at any site (left posterior cingulate); and for reduced pars triangularis volume in chronic neck/shoulder (left pars triangularis) and widespread pain (right pars triangularis). Across these negative genetic correlations, a significant genetic causal proportion was only found between mean insula thickness and chronic abdominal pain [rG (standard error, SE) = -0.25 (0.08), P = 1.06 × 10-3; GCP (SE) = -0.69 (0.20), P = 4.96 × 10-4]. This finding suggests that the genes underlying reduced cortical thickness of the insula causally contribute to an increased risk of chronic abdominal pain. Altogether, these results provide independent corroborating evidence for observational reports of decreased grey matter of particular brain regions in chronic pain. Further, we show for the first time that this association is mediated (in part) by genetic factors. These novel findings warrant further investigation into the neurogenetic pathways that underlie the development and prolongation of chronic pain conditions.

On pain - Virginia Woolf and the language of poets and patients

Influenced by Virginia Woolf pain is traditionally believed to be a private object that defies language. However, our analysis of classical and contemporary works of British and American poets, in addition to our own clinical experiences, leads us to challenge this notion. In accordance with Wittgenstein we instead view pain as a concept and objective experience that should encourage interaction. Reasons why patients and healthcare providers often assume language to be insufficient to grasp the complexity of pain are manifold. Based on neuro-cognitive mechanisms we propose an important contributor might be that patients in pain speak a different language than their pain-free peers and doctors.

Brain circuits for pain and its treatment

[Figure: see text].

Pain modulation induced by electronic wrist-ankle acupuncture: A functional near-infrared spectroscopy study

BACKGROUND

As a new technology, electronic wrist-ankle acupuncture (E-WAA) combines the advantages of wrist-ankle acupuncture and transcutaneous electrical nerve stimulation, but the analgesic effect and mechanism need to be clarified. The purpose of this study was to identify the pain modulation caused by E-WAA by evaluating the response of the prefrontal cortex (PFC) from the perspective of neurophysiology.

METHODS

Fifty male volunteers (age 25.00 ± 1.05 years) with trapezius myofascial pain syndrome were randomly allocated into intervention group (E-WAA treatment) or sham control group at a 1:1 ratio. An outcome evaluation system was used to induce tenderness on the Jianjing point and record the pain value. A multichannel functional near-infrared spectroscope was used to detect the PFC activation during tenderness before and after treatment to demonstrate the neuromodulation mechanism. A general linear model and t-test (p < 0.05) were used to analyze the difference in the oxyhemoglobin (HbO) concentration and pain value.

RESULTS

In the intervention group, the pain value of volunteers decreased significantly (p = 0.017) after E-WAA treatment, whereas there was no statistical difference (p = 0.082) in the sham group. Before treatment, the frontopolar (FP) and dorsolateral prefrontal cortex (DLPFC) were the activation areas of the PFC. The E-WAA treatment then suppressed the activation of the two areas. The HbO concentration of the FP and DLPFC changed from a sharp rise during tenderness to not changing with tenderness stimulation.

CONCLUSION

The results demonstrated that the E-WAA have a great analgesic effect. The FP and DLPFC were relative to the analgesia neuromodulation induced by the E-WAA.

Multidimensional Self-report Assessment of Children's Acute Pain in an Inpatient Setting

OBJECTIVE

This study assessed the feasibility of administering a multidimensional, self-report pain assessment protocol to children in an inpatient, acute pain context, and sought insight into the interrelationships between sensory, affective, and evaluative pain dimensions.

METHODS

A total of 132 children (5 to 16 y) experiencing acute pain were recruited from acute pain ward rounds or the short-stay surgical unit. A multidimensional self-report assessment protocol was administered, assessing pain intensity, pain-related affect, bother, perceived unfairness, and pain expectations (for tomorrow and in 1 wk). Duration of protocol administration was assessed and ease of administration was rated. Pain-related behaviors were rated using the Face, Legs, Activity, Cry, and Consolability (FLACC) Scale.

RESULTS

The duration of protocol administration was <2.5 minutes, on average, for all age groups. Median ease of protocol administration was 7/10 for 5- to 7-year-olds and 8/10 for older age groups. Pain-related bother was higher for 14- to 16-year-olds, relative to younger age groups, and significantly correlated with perceived unfairness (r=0.59, P<0.01), intensity (r=0.76, P<0.01), and affect (r=0.33, P<0.05). For younger age groups, bother was significantly positively correlated only with pain intensity (rs=0.59 to 0.79, Ps<0.01) and affect (rs=0.4 to 0.71, Ps <0.05). A stepwise multiple regression analysis found multidimensional self-reported information (especially pain intensity and perceived unfairness), accounted for significant additional amount of variance, beyond that explained by age, pain duration, and observed pain behavior.

DISCUSSION

Sensory, affective, and evaluative aspects of children's clinical, acute pain experience may be assessed using self-report tools, which provide unique and valuable information about their pain experience.

Supraspinal nociceptive networks in neuropathic pain after spinal cord injury

Neuropathic pain following spinal cord injury involves plastic changes along the whole neuroaxis. Current neuroimaging studies have identified grey matter volume (GMV) and resting-state functional connectivity changes of pain processing regions related to neuropathic pain intensity in spinal cord injury subjects. However, the relationship between the underlying neural processes and pain extent, a complementary characteristic of neuropathic pain, is unknown. We therefore aimed to reveal the neural markers of widespread neuropathic pain in spinal cord injury subjects and hypothesized that those with greater pain extent will show higher GMV and stronger connectivity within pain related regions. Thus, 29 chronic paraplegic subjects and 25 healthy controls underwent clinical and electrophysiological examinations combined with neuroimaging. Paraplegics were demarcated based on neuropathic pain and were thoroughly matched demographically. Our findings indicate that (a) spinal cord injury subjects with neuropathic pain display stronger connectivity between prefrontal cortices and regions involved with sensory integration and multimodal processing, (b) greater neuropathic pain extent, is associated with stronger connectivity between the posterior insular cortex and thalamic sub-regions which partake in the lateral pain system and (c) greater intensity of neuropathic pain is related to stronger connectivity of regions involved with multimodal integration and the affective-motivational component of pain. Overall, this study provides neuroimaging evidence that the pain phenotype of spinal cord injury subjects is related to the underlying function of their resting brain.

Intranasal Administration for Pain: Oxytocin and Other Polypeptides

Pain, particularly chronic pain, remains one of the most debilitating and difficult-to-treat conditions in medicine. Chronic pain is difficult to treat, in part because it is associated with plastic changes in the peripheral and central nervous systems. Polypeptides are linear organic polymers that are highly selective molecules for neurotransmitter and other nervous system receptors sites, including those associated with pain and analgesia, and so have tremendous potential in pain therapeutics. However, delivery of polypeptides to the nervous system is largely limited due to rapid degradation within the peripheral circulation as well as the blood–brain barrier. One strategy that has been shown to be successful in nervous system deposition of polypeptides is intranasal (IN) delivery. In this narrative review, we discuss the delivery of polypeptides to the peripheral and central nervous systems following IN administration. We briefly discuss the mechanism of delivery via the nasal–cerebral pathway. We review recent studies that demonstrate that polypeptides such as oxytocin, delivered IN, not only reach key pain-modulating regions in the nervous system but, in doing so, evoke significant analgesic effects. IN administration of polypeptides has tremendous potential to provide a non-invasive, rapid and effective method of delivery to the nervous system for chronic pain treatment and management.

The effects of long-term menstrual pain on pain empathy in women with primary dysmenorrhea

ABSTRACT

Primary dysmenorrhea (PDM) is not only a painful experience but also affects the psychological and affective states of women. Neuroimaging studies have revealed shared neural substrates for somatic and empathic pains in healthy subjects. However, little is known about the relationship between pain intensity and pain empathy in pain disorders. The cyclic nature of PDM makes it a unique model for investigating this issue during a patients' pain phase. To study how long-term pain modulates empathy for pain, T1-weighted magnetic resonance imaging scans were obtained in 39 PDM patients and 41 matched female healthy controls during menstruation. Subjects viewed static visual stimuli of the limbs submitted to painful and nonpainful stimulation to solicit empathy. The visual analogue scale for pain intensity and the Interpersonal Reactivity Index for empathic ability were also obtained. We found that women with PDM exhibited higher pain empathy compared with controls. The anterior insula and brain regions related to sensory discrimination with decreased gray matter volumes were not only shared but also acted as a mediator between pain intensity and pain empathy in PDM patients. In addition, the general linear modeling analysis revealed that long-term pain experience was a more important factor to pain empathy compared with pain intensity. This indicated that long-term pain may cause maladaptive brain structural plasticity, which may further affect psychological adjustment to bring patients more vivid pain when they witness suffering and distress in others.

Chronic pain: an update on burden, best practices, and new advances

Chronic pain exerts an enormous personal and economic burden, affecting more than 30% of people worldwide according to some studies. Unlike acute pain, which carries survival value, chronic pain might be best considered to be a disease, with treatment (eg, to be active despite the pain) and psychological (eg, pain acceptance and optimism as goals) implications. Pain can be categorised as nociceptive (from tissue injury), neuropathic (from nerve injury), or nociplastic (from a sensitised nervous system), all of which affect work-up and treatment decisions at every level; however, in practice there is considerable overlap in the different types of pain mechanisms within and between patients, so many experts consider pain classification as a continuum. The biopsychosocial model of pain presents physical symptoms as the denouement of a dynamic interaction between biological, psychological, and social factors. Although it is widely known that pain can cause psychological distress and sleep problems, many medical practitioners do not realise that these associations are bidirectional. While predisposing factors and consequences of chronic pain are well known, the flipside is that factors promoting resilience, such as emotional support systems and good health, can promote healing and reduce pain chronification. Quality of life indicators and neuroplastic changes might also be reversible with adequate pain management. Clinical trials and guidelines typically recommend a personalised multimodal, interdisciplinary treatment approach, which might include pharmacotherapy, psychotherapy, integrative treatments, and invasive procedures.

Magnesium for Pain Treatment in 2021? State of the Art

Background: Magnesium (Mg) is commonly used in clinical practice for acute and chronic pain and has been reported to reduce pain intensity and analgesics consumption in a number of studies. Results are, however, contested. Objectives: This review aims to investigate randomised clinical trials (RCTs) on the effectiveness of Mg treatment on pain and analgesics consumption in situations including post-operative pain, migraine, renal pain, chronic pain, neuropathic pain and fibromyalgia. Results: The literature search identified 81 RCTs (n = 5447 patients) on Mg treatment in pain (50 RCTs in post-operative pain, 18 RCTs in migraine, 5 RCTs in renal pain, 6 RCTs in chronic/neuropathic pain, 2 RCTs in fibromyalgia). Conclusion: The level of evidence for the efficacy of Mg in reducing pain and analgesics consumption is globally modest and studies are not very numerous in chronic pain. A number of gaps have been identified in the literature that need to be addressed especially in methodology, rheumatic disease, and cancer. Additional clinical trials are needed to achieve a sufficient level of evidence and to better optimize the use of Mg for pain and pain comorbidities in order to improve the quality of life of patients who are in pain.

Psychological profile and unexpected pain in oral lichen planus: A case-control multicenter SIPMO studya

OBJECTIVES

To analyze psychological profiles, pain, and oral symptoms in patients with oral lichen planus (OLP).

MATERIALS AND METHODS

300 patients with keratotic OLP (K-OLP; reticular, papular, plaque-like subtypes), 300 patients with predominant non-keratotic OLP (nK-OLP; erythematosus atrophic, erosive, ulcerative, bullous subtypes), and 300 controls were recruited in 15 universities. The number of oral sites involved and oral symptoms were recorded. The Numeric Rating Scale (NRS), Total Pain Rating Index (T-PRI), Hamilton Rating Scales for Depression and for Anxiety (HAM-D and HAM-A), Pittsburgh Sleep Quality Index (PSQI), and Epworth Sleepiness Scale (ESS) were administered.

RESULTS

The OLP patients, especially the nK-OLP, showed higher scores in the NRS, T-PRI, HAM-D, HAM-A and PSQI compared with the controls (p-value < .001** ). A positive correlation between the NRS, T-PRI, HAM-A, HAM-D, and PSQI was found with the number of oral symptoms and number of oral sites involved. Pain was reported in 67.3% of nK-OLP and 49.7% of K-OLP cases with poor correspondence between the site of lesions and the site of the symptoms.

CONCLUSIONS

Mood disorders are frequently associated with OLP with an unexpected symptomatology correlated with the number of oral symptoms and with the extension of disease suggesting a peripheral neuropathy.

[Prediction and prevention of chronic postoperative pain]

Chronic postoperative pain has been identified as a major medical and socioeconomic problem. A prevention of the chronification processes is potentially possible and preventive treatment could start early (e.g. preoperatively). So far, however, evidence for the effectiveness of preventive strategies is basically low. Important reasons for this dilemma are the lack of appropriate risk assessment as well as effective and mechanism-based preventive (procedure-sepcific) strategies for the chronification process, a lack of stratification of treatment approaches and a so far barely investigated combination of various treatment approaches. In this review article recent findings on the appropriate identification of patients at risk for developing postoperative chronic pain are presented, predictive models for the valid estimation of the individual risk of patients are assessed and studies on pharmaceutical and regional analgesia techniques influencing the pain chronification process are discussed. As a chronification process is, however, extremely complex and dynamic and also necessitates adaptation of the prevention during the course of the process, only combinations of treatment, interdisciplinary and if necessary even longer term approaches might be successful. Future studies are needed to address with which preventive treatment strategies and in which patients chronic pain after surgery can effectively be prevented.

Relationship Between Blood Cytokine Levels, Psychological Comorbidity, and Widespreadness of Pain in Chronic Pelvic Pain

Background: Low-grade inflammation has been implicated in the etiology of depression, long-term fatigue and chronic pain. TNFα and IL-6 are perhaps the most studied pro-inflammatory cytokines in the field of psychoneuroimmunology. The purpose of our study was to further investigate these relationships in patients with chronic pelvic pain specifically. Using plasma samples from a large, well-described cohort of patients with pelvic pain and healthy controls via the Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network, we examined the relationship between TNFα and IL-6 and comorbid psychological symptoms. We also investigated the relationship between IL-8 and GM-CSF, and widespreadness of pain. Methods: We included baseline blood samples in the analyses, 261 patients (148 women) and 110 healthy controls (74 women). Fourteen pro- and anti-inflammatory or regulatory cytokines were analyzed in a Luminex^® xMAP^® high-sensitivity assay. We used regression models that accounted for known factors associated with the outcome variables to determine the relationship between cytokine levels and clinical measures. Results: There were no statistical differences in cytokine levels between patients and healthy controls when controlling for age. In patients, TNFα was significantly associated with levels of fatigue (p = 0.026), but not with pain intensity or depression. IL-6 was not significantly related to any of the outcome variables. Women with pelvic pain showed a negative relationship between IL-8 and widespreadness of pain, while men did not (p = 0.003). For both sexes, GM-CSF was positively related to widespreadness of pain (p = 0.039). Conclusion: Our results do not suggest low-grade systemic inflammation in chronic pelvic pain. Higher TNFα blood levels were related to higher fatigue ratings, while higher systemic GM-CSF levels predicted more widespread pain. Our study further suggests a potentially protective role of IL-8 with regard to with regard to the widepreadness of pain in the body, at least for women.

Transcutaneous auricular vagus nerve stimulation (taVNS) for migraine: an fMRI study

BACKGROUND

Dysfunction of the thalamocortical connectivity network is thought to underlie the pathophysiology of the migraine. This current study aimed to explore the thalamocortical connectivity changes during 4 weeks of continuous transcutaneous vagus nerve stimulation (taVNS) treatment on migraine patients.

METHODS

70 migraine patients were recruited and randomized in an equal ratio to receive real taVNS or sham taVNS treatments for 4 weeks. Resting-state functional MRI was collected before and after treatment. The thalamus was parceled into functional regions of interest (ROIs) on the basis of six priori-defined cortical ROIs covering the entire cortex. Seed-based functional connectivity analysis between each thalamic subregion and the whole brain was further compared across groups after treatment.

RESULTS

Of the 59 patients that finished the study, those in the taVNS group had significantly reduced number of migraine days, pain intensity and migraine attack times after 4 weeks of treatment compared with the sham taVNS. Functional connectivity analysis revealed that taVNS can increase the connectivity between the motor-related thalamus subregion and anterior cingulate cortex/medial prefrontal cortex, and decrease the connectivity between occipital cortex-related thalamus subregion and postcentral gyrus/precuneus.

CONCLUSION

Our findings suggest that taVNS can relieve the symptoms of headache as well as modulate the thalamocortical circuits in migraine patients. The results provide insights into the neural mechanism of taVNS and reveal potential therapeutic targets for migraine patients.

Mild traumatic brain injury is associated with effect of inflammation on structural changes of default mode network in those developing chronic pain

Background

Mild traumatic brain injury (mTBI) has a higher prevalence (more than 50%) of developing chronic posttraumatic headache (CPTH) compared with moderate or severe TBI. However, the underlying neural mechanism for CPTH remains unclear. This study aimed to investigate the inflammation level and cortical volume changes in patients with acute PTH (APTH) and further examine their potential in identifying patients who finally developed CPTH at follow-up.

Methods

Seventy-seven mTBI patients initially underwent neuropsychological measurements, 9-plex panel of serum cytokines and MRI scans within 7 days post-injury (T-1) and 54 (70.1%) of patients completed the same protocol at a 3-month follow-up (T-2). Forty-two matched healthy controls completed the same protocol at T-1 once.

Results

At baseline, mTBI patients with APTH presented significantly increased GM volume mainly in the right dorsal anterior cingulate cortex (dACC) and dorsal posterior cingulate cortex (dPCC), of which the dPCC volume can predict much worse impact of headache on patients’ lives by HIT-6 (β = 0.389, P = 0.007) in acute stage. Serum levels of C-C motif chemokine ligand 2 (CCL2) were also elevated in these patients, and its effect on the impact of headache on quality of life was partially mediated by the dPCC volume (mean [SE] indirect effect, 0.088 [0.0462], 95% CI, 0.01–0.164). Longitudinal analysis showed that the dACC and dPCC volumes as well as CCL2 levels had persistently increased in patients developing CPTH 3 months postinjury.

Conclusion

The findings suggested that structural remodelling of DMN brain regions were involved in the progression from acute to chronic PTH following mTBI, which also mediated the effect of inflammation processes on pain modulation.

Trial registration

ClinicalTrial.gov ID: NCT02868684; registered 16 August 2016.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-020-01201-7.