The cerebral signature for pain perception and its modulation

Stress-Related Brain Alterations in Chronic Pain

BACKGROUND

Stress symptoms are commonly experienced by people with chronic pain. Although stress and chronic pain are associated with similar effects on brain morphology, the present study aims to clarify the relationship between stress severity, chronic pain, and brain morphology.

METHODS

Fifty-two people with chronic pain and 38 pain-free healthy controls (HC) underwent T1-weighted magnetic resonance imaging. Severity of stress symptoms was measured using the civilian version of the posttraumatic stress disorder checklist (PCL-C). A series of multiple linear regressions determined the main effects of group, stress symptom severity (PCL-C total score and symptom-specific scores) and their interaction on grey matter volume of selected regions of interest.

RESULTS

The interaction term was significantly associated with variations in grey matter volume in the left and right putamen, the left middle cingulate cortex (MCC) and the right posterior insula. Results showed significantly smaller left and right putamen when reporting higher stress levels, and significantly larger left MCC and right posterior insula at lower stress levels in people with chronic pain compared to HCs. In addition, increasing stress severity was significantly associated with larger left and right putamen in HCs, and significantly associated with smaller left MCC and right posterior insula in people with chronic pain.

CONCLUSIONS

Severity of stress moderated chronic pain-related grey matter alterations. More severe stress, especially avoidance, was associated with smaller left MCC, a core region of the "pain matrix". The MCC is strongly linked with the somatosensory network and critical for empathy, especially toward pain-related stimuli.

SIGNIFICANCE

To our knowledge, this is the first study to show that stress severity differentially impacts grey matter integrity in people with chronic pain compared to pain-free healthy controls. Briefly, our results indicate that higher levels of stress were associated with larger putamen and right posterior insula in pain-free participants, potentially reflecting mechanisms of resilience to trauma in this group. Higher levels of stress, especially avoidance symptoms, were associated with smaller left middle cingulate cortex, a region with strong links to the somatosensory network and critical for empathy, especially toward pain-related stimuli.

Reduced Cortical Surface Area in the Frontal Operculum as a Causal Risk Predictor for Chronic Pain

Chronic pain is a prevalent and debilitating condition that imposes substantial personal and societal burdens. Despite its significance, the neural mechanisms underlying individual susceptibility to chronic pain remain inadequately understood. In this study, we examined the prospective associations between 1325 brain structural imaging phenotypes and the future risk of developing chronic pain in a UK Biobank cohort of 5754-5756 participants. These phenotypes encompassed regional and tissue volume, cortical surface area and thickness. General linear models (GLMs) were employed to identify brain structural variations associated with the risk of developing chronic pain, and then Mendelian randomization (MR) was employed to explore potential causal relationships between brain structure and chronic pain development. GLMs identified three significant associations between imaging phenotypes and the future development of chronic pain. All three imaging phenotypes pertained to the cortical surface area of the frontal operculum, albeit derived from three different brain atlases. Specifically, reduced cortical surface area in the frontal operculum was significantly associated with an increased risk of developing chronic pain: BA atlas area 44 (T=-4.10, p=4.24 × 10-5), Desikan atlas pars opercularis (T=-4.21, p=2.55 × 10-5), and DKT atlas pars opercularis (T=-3.96, p=7.47 × 10-5). Subsequent MR analysis further demonstrated a causally protective effect of larger cortical area in the prefrontal operculum against the risk of developing chronic pain (OR = 0.91, p=1.91 × 10-2). These results indicate a critical role of the surface area of frontal operculum in individual chronic pain susceptibility and provide a potential risk predictor for chronic pain development.

Remapping Body Representation Using Virtual Reality in Chronic Neuropathic Pain: Systematic Review

BACKGROUND

Chronic neuropathic pain (CNP) is a common consequence of neurological conditions such as spinal cord injury (SCI), complex regional pain syndrome (CRPS), and phantom limb pain (PLP). These conditions are often associated with distorted body representation (BR) and altered sensory processing. Virtual reality (VR) offers immersive, multisensory experiences that can modulate attention, recalibrate BR, and potentially alleviate pain.

OBJECTIVE

This systematic review aims to synthesize evidence on the use of VR-based interventions for managing CNP in patients with neurological conditions. It explores how VR can influence pain perception through body remapping. Furthermore, this review seeks to identify gaps in current research, offering recommendations for future research directions and clinical applications.

METHODS

We performed a comprehensive literature search in PubMed, Web of Science, and Scopus for studies published between January 2014 and December 2024. We included original studies that examined VR interventions in patients with neurological conditions and CNP, assessing pain reduction, improvements in BR, or functional recovery. We excluded reviews, animal model studies, migraine-related studies, and those lacking a clear VR intervention or relevant clinical outcome data. The quality of the included studies was evaluated using the revised Cochrane Risk of Bias Tool for Randomized Trials and the Cochrane Risk of Bias in Nonrandomized Studies of Interventions tool. Given the heterogeneity in study design, VR protocols, and outcome measures, a qualitative synthesis approach was adopted based on the synthesis without meta-analysis framework.

RESULTS

Ten studies-both randomized controlled trials and uncontrolled experimental designs-met the inclusion criteria. These studies focused on the application of VR in SCI (n=4, 40%), CRPS (n=4, 40%), and PLP (n=2, 20%), using interventions such as immersive VR, mirror visual feedback, visuotactile stimulation, and virtual body illusions. Sample sizes ranged from 9 to 70 participants, with varying degrees of neurological impairment. Most of the studies (n=7, 70%) reported substantial reductions in pain intensity and improvements in embodiment and perceived body ownership. In SCI, combining VR with neuromodulation techniques enhanced analgesic effects. In CRPS, modifying the visual appearance of the affected limb improved body image and decreased pain perception. In PLP, kinesthetic and visual feedback delivered through VR environments significantly reduced PLP and improved movement representation.

CONCLUSIONS

Overall, the quality of evidence ranged from moderate to low, mainly due to small sample sizes, protocol heterogeneity, and risk of bias. Evidence regarding adherence to VR therapy was particularly limited. Nonetheless, VR shows strong potential as a noninvasive, patient-tailored therapeutic tool for CNP. VR could provide innovative and engaging strategies to reduce pain and enhance functional outcomes in populations with neurological conditions. Future research should focus on developing standardized protocols and conducting large-scale, high-quality trials to validate VR's long-term efficacy and integration into routine clinical practice.

TRIAL REGISTRATION

PROSPERO CRD42024606150; https://www.crd.york.ac.uk/PROSPERO/view/CRD42024606150.

Impact of conservative versus conventional instrumentation on the release of inflammatory mediators and post-operative pain in mandibular molars with asymptomatic irreversible pulpitis: A randomized clinical trial

AIM

This study aimed to compare the release of inflammatory mediators and post-operative pain after conservative and conventional root canal preparations of mandibular molars with asymptomatic irreversible pulpitis.

METHODOLOGY

Forty-five healthy patients diagnosed with asymptomatic irreversible pulpitis were randomly assigned to three groups based on the system used for root canal preparation (n = 15): ProTaper Gold, OneShape and TruNatomy. Gingival crevicular fluid samples were collected for baseline measurements, 24 and 72 h after root canal treatment. Inflammatory mediators (Substance P, IL-6, IL-10 and PGE-2) were quantified using enzyme-linked immunosorbent assays, and post-operative pain was assessed using the visual analogue scale (VAS) and compared among groups with linear regression analysis.

RESULTS

All mediators exhibited an increase at 24 h and a decrease at 72 h. The release of Substance P in the OneShape group was significantly higher than in the TruNatomy and ProTaper Gold groups (Odds Ratio (OR) = 17.4 and 21.7, respectively, at 24 h and 21.5 and 15.6 at 72 h; p < .05). IL-6 and IL-10 were significantly higher in the OneShape and ProTaper Gold groups compared to TruNatomy at 24 h (p < .05). PGE2 levels were not affected by the type of instruments (p > .05). VAS scores were significantly higher at 24 h compared to baseline, with root canal preparation using OneShape significantly associated with higher post-operative pain than preparation with ProTaper Gold (p < .05). Analgesic intake was not related to the instrumentation group or any other patient- or tooth-related factors.

CONCLUSION

Conservative root canal preparation of mandibular molars with asymptomatic irreversible pulpitis decreased the release of inflammatory mediators but did not influence post-operative pain.

Brain morphological changes in type 2 diabetes patients with painful peripheral neuropathy

We investigates changes in brain volume and cortical thickness in patients with type 2 diabetes mellitus (T2DM) and peripheral neuropathy (DPN), particularly those with neuropathic pain. 105 participants were divided into three groups: T2DM (n = 26), T2DM with DPN (n = 42), and healthy controls (HCs, n = 37). The DPN group was further divided into painless (n = 22) and painful (n = 20) subgroups. Participants underwent clinical neuropsychological testing, electromyography, and brain MRI scans. Voxel-based morphometry was used to analyze gray matter volume (GMV) and cortical thickness. Associations between morphological changes and clinical/neuropsychological indicators were assessed. Average cortical thickness of the three patient subgroups was significantly reduced compared to the HCs. GMV loss in the DPN_ pain group was confined to the cerebellum, right putamen/pallidum, and caudate, while GMV increased in the brainstem. Multiple regression analysis showed correlations between brain regions and factors such as cholesterol levels, neuropathic pain severity, and nerve amplitudes (P < 0.001). The volume of right lateral geniculate nucleus volume was linked to the DN4 score (r = 0.593, P = 0.015) and onset age (r = -0.541, P = 0.031). Specific brain regions and the cortices are more vulnerable to the effects of neuropathic pain and peripheral nerve damage.

A bad break: mechanisms and assessment of acute and chronic pain after bone fracture

ABSTRACT

Pain is one of the primary indicators of a bone fracture and serves both a functional and practical role in guiding recovery. However, fracture pain can persist long after the fracture itself has clinically healed. The neural and molecular mechanisms that drive acute pain postfracture, and how these mechanisms are pathologically usurped to trap patients into persistent, debilitating, and often difficult to treat, chronic pain, are not well understood. The aim of this review is to provide insight into the risk factors for pain persistence after fracture, review the physiological and pathophysiological mechanisms of fracture pain, and critically evaluate the literature around fracture pain assessment techniques/models. Taken together, the concepts covered herein will provide a strong foundation to support the development of more effective treatments to better alleviate postfracture pain.

Pupil dilation evoked by painful electrical stimulation is abolished during pain inhibition by distraction

The aim of the present study was to examine the contribution of spinal and supraspinal processes to pain modulation by attention. It is hypothesized that pain inhibition by distraction is accompanied by reduced pain-evoked pupil dilation and cerebral activity, but no inhibition of the nociceptive flexion reflex (NFR), while pain anticipation is expected to increase pain perception and pain-related responses. Twenty healthy volunteers received 90 painful stimuli in control, distraction (mental arithmetic), and anticipation (visual cue) conditions. Anticipation did not modulate pain (p = .7), while distraction decreased pain significantly (p < .001). Moreover, pupil diameter increased 500-1000 ms post-stimulus in the control condition (p < .05), but this response was abolished by distraction. Distraction also decreased pain-related brain activity (high-gamma oscillations) (p = .004), but not the NFR (p = .3). These results suggest that pain inhibition by distraction is produced, in part, by supraspinal inhibition of nociceptive processes.

Behavioral manifestations and neural mechanisms of empathic pain

Empathy is an important trait that allows individuals to comprehend and share the emotions and sentiments of others. It not only facilitates effective interpersonal communication, but also helps in establishing meaningful connections and fostering trust and understanding. Impaired empathy development can manifest as excessive self-centeredness, extreme egoism, and antisocial behaviors. Many psychiatric disorders, such as autism, narcissistic personality disorder, and schizophrenia, are often accompanied by empathy disorders. Pain empathy, which is a common behavioral paradigm of empathic behavior, is not only observed in humans but also in animals. By delving into the study of pain empathy, we can gain a deeper understanding of empathy itself. This understanding not only contributes to the advancement of scientific, clinical, and social fields, but also promotes the cultivation of emotional resonance and social harmony among humans, with profound significance and impact. This article provides a brief overview of the current understanding and mechanistic studies of pain empathy, as well as suggests future research directions.

White matter and cortical gray matter microstructural alterations in migraine: a NODDI and DTI analysis

BACKGROUND

The pathophysiological mechanism of migraine remains elusive, thereby impeding the effective treatment of the disease. Current neuroimaging research focuses on changes in brain functional connectivity, functional networks, and macrostructural alterations, which reflect abnormal neuronal function during the disease process. The plasticity changes in neuronal structures and neurotransmitter system dysregulations potentially play a crucial role in migraine onset and chronicity of migraine. This study utilizes multimodal neuroimaging techniques to investigate the microstructural and neurotransmitter alterations in migraine and provides new insights into its pathological mechanisms and therapeutic method.

METHODS

Microstructural alterations in both white matter (WM) and cortical gray matter (GM) were evaluated among 40 chronic migraine (CM) patients, 35 episodic migraine (EM) patients, and 45 healthy controls (HCs) using Diffusion Tensor Imaging (DTI) and Neurite Orientation Dispersion and Density Imaging (NODDI) models. Tract-based spatial statistics (TBSS) and Surface-based analysis (SBA) were performed to compare groupwise differences in white and gray matter microstructure, respectively. Furthermore, the cross-modal toolbox JuSpace was used to analyze the correlation between cortical gray matter neurite alterations and neurotransmitter.

RESULTS

In the WM, compared to HC, a decrease in neurite density index (NDI) was identified in the migraine group, and both NDI and fractional anisotropy (FA) were decreased in the CM group. No significant alterations were observed in the EM group. An increase in radial diffusivity (RD) was found in the CM group compared to the EM group. In the cortical GM, compared to HC, the migraine group had fewer neurites in the right insula and temporal pole cortex, and the CM group showed a reduction in neurites in the right middle temporal and fusiform cortex. The cortical GM of neurite damage was negatively correlated with neurotransmitters in migraine and CM. There was no correlation between NODDI and DTI metrics of these brain regions and clinical data after the Bonferroni correction.

CONCLUSION

Our findings indicated that neurite loss was detected in both WM and cortical GM of migraineurs. As the migraine progresses into chronicity, the axonal damage may become more pronounced. The neurite damage of cortical GM was negatively related to neurotransmitters.

Aberrant Spontaneous Low-Frequency Brain Activity in Migraine: A Meta-Analysis of Resting-State fMRI Studies

BACKGROUND AND PURPOSE

Resting-state functional MRI has revealed abnormal brain activity in patients with migraine, though findings have been inconsistent. This meta-analysis utilized Seed-based d Mapping to assess variations in amplitude of low-frequency fluctuations (ALFF) and fractional amplitude of low-frequency fluctuations (fALFF). The aim was to identify common brain regions with altered spontaneous brain activity in migraine patients.

METHODS

A systematic search was conducted in PubMed, Web of Science, and Embase for studies published up to August 2023, comparing spontaneous low-frequency brain activity between migraine patients and healthy controls (HCs). Jackknife sensitivity, heterogeneity, publication bias, and meta-regression analyses were performed to ensure the robustness and reliability of our findings.

RESULTS

Nine studies, including 708 migraine patients and HCs, were included in the analysis. Applying a highly conservative family-wise error rate correction, no significant findings were observed. However, when a less conservative threshold was used, migraine patients exhibited increased ALFF/fALFF in the left anterior thalamus and the corticospinal tract but showed decreased values in the right middle frontal gyrus. Jackknife sensitivity analysis confirmed the reproducibility of these results, while heterogeneity analysis revealed significant variability across studies, likely due to differences in study design and patient populations.

CONCLUSIONS

This meta-analysis provides a comprehensive synthesis of neuroimaging evidence, linking migraine to abnormal spontaneous brain activity in regions associated with pain processing and nociceptive emotional modulation. These findings enhance our understanding of migraine pathophysiology and highlight potential targets for neuromodulation therapies, offering new directions for future research and clinical interventions.

Chronic pain is associated with greater brain entropy in the prefrontal cortex

Chronic pain is a debilitating clinical condition and a severe public health issue that demands to be addressed. Neuroimaging-based techniques have been widely adopted to investigate the neural underpinnings of chronic pain. Despite the efforts the complex nature of pain experience as well as the heterogeneity of chronic pain have made the identification of neuroimaging-based biomarkers extremely challenging. In this study, resting-state fMRI-based brain entropy, a measure reflecting the "irregularity" of brain activity, was adopted as a biomarker of chronic pain by comparing individuals with chronic pain and healthy controls in a sample of middle-to-old-age participants (n > 30,000) drawn from the UK Biobank database. Abnormal brain entropy is associated with altered brain dynamics and may serve as a potential marker of disrupted pain processing in individuals with chronic pain. Compared to healthy controls, individuals with chronic pain exhibited increased brain entropy in a broad set of regions including the frontal, temporal, and occipital lobes, as well as the cerebellum. In addition, individuals with a more distributed chronic pain showed increased brain entropy in occipital lobes. When examining distinct types of chronic pain individually, only participants with headache and pain all over the body showed brain entropy differences compared to a matched sample of healthy controls. PERSPECTIVE: This article investigates the neural substrates of chronic pain using brain entropy, a measure of the randomness and irregularity of brain activity. This measure could potentially aid in the assessment and treatment of chronic pain.

Predicting placebo analgesia responses in clinical trials: where to look next? A meta-analysis of individual patient data

ABSTRACT

Estimating the magnitude of placebo responses across pharmacological and nonpharmacological trials is important for understanding their influence on trial outcomes. Yet, the extent to which more intense placebo interventions like sham acupuncture yield larger analgesic responses than placebo pills, and the factors predicting these responses, remain unclear. This meta-analysis investigated the magnitude and predictors of placebo analgesia responses in pharmacological vs acupuncture trials. Analyses included individual patient data from the placebo arm of 11 randomized controlled trials (RCTs): 9 pharmacological RCTs using placebo pills (N = 2021) and 2 acupuncture RCTs using sham acupuncture (N = 747). All trials were conducted in patients with chronic nociceptive pain (osteoarthritis, N = 2068; low back pain, N = 700). The placebo response was calculated as the change in pain intensity (0-100) between baseline and week 12. A random effects model demonstrated that placebo pills and patients with osteoarthritis exhibited smaller placebo responses than sham acupuncture and patients with low back pain (both P < 0.001, marginal effects). A mixed effects model showed that route of administration interacted significantly with baseline pain, premature termination, and the presence of adverse events. Together, predictors explained 20% to 25% of the individual variance in placebo responses, whereas 75% to 80% remained unaccounted for. In summary, sham acupuncture accounted for slightly larger placebo responses than placebo pills. Since basic trial and patient parameters explained only a small portion of this variability, we might need to start considering the patient's perception of the treatment-including cognition and emotions-to better predict placebo analgesia responses.

Diabetic neuropathy: cutting-edge research and future directions

Diabetic neuropathy (DN) is a prevalent and debilitating complication of diabetes mellitus, significantly impacting patient quality of life and contributing to morbidity and mortality. Affecting approximately 50% of patients with diabetes, DN is predominantly characterized by distal symmetric polyneuropathy, leading to sensory loss, pain, and motor dysfunction, often resulting in diabetic foot ulcers and lower-limb amputations. The pathogenesis of DN is multifaceted, involving hyperglycemia, dyslipidemia, oxidative stress, mitochondrial dysfunction, and inflammation, which collectively damage peripheral nerves. Despite extensive research, disease-modifying treatments remain elusive, with current management primarily focusing on symptom control. This review explores the complex mechanisms underlying DN and highlights recent advances in diagnostic and therapeutic strategies. Emerging insights into the molecular and cellular pathways have unveiled potential targets for intervention, including neuroprotective agents, gene and stem cell therapies, and innovative pharmacological approaches. Additionally, novel diagnostic tools, such as corneal confocal microscopy and biomarker-based tests, have improved early detection and intervention. Lifestyle modifications and multidisciplinary care strategies can enhance patient outcomes. While significant progress has been made, further research is required to develop therapies that can effectively halt or reverse disease progression, ultimately improving the lives of individuals with DN. This review provides a comprehensive overview of current understanding and future directions in DN research and management.

Forebrain networks driving brainstem pain modulatory circuits during nocebo hyperalgesia in healthy humans

ABSTRACT

Prior experiences, conditioning cues, and expectations of improvement are essential for nocebo hyperalgesia expression. The neural circuits that communicate with brainstem pain modulatory nuclei during nocebo hyperalgesia responsivity are underexplored. In this study, we employed a classical conditioning and expectation model in 25 healthy human participants and measured brain activity using ultra-high field functional magnetic resonance imaging. We assessed forebrain activity changes as well as noxious stimulus-independent and -dependent connectivity changes with the lateral midbrain periaqueductal gray matter (lPAG). We found hyperalgesia-related signal increases in the orbitofrontal cortex, insula, and amygdala. In addition, we found stimulus-dependent lPAG connectivity changes with the orbitofrontal, anterior cingulate, and dorsolateral prefrontal cortices and stimulus-independent lPAG connectivity with the anterior cingulate cortex, dorsolateral prefrontal cortex, and nucleus accumbens during hyperalgesia. Whilst these connectivity changes are all associated with hyperalgesia, dynamic causal modelling analysis revealed that the dorsolateral prefrontal cortex was principally responsible for driving the lPAG. Overall, our results show that there is a complex relationship between forebrain activation and connectivity with brainstem pain modulation circuitry that results in the behavioural expression of nocebo hyperalgesia.

Perceptions of music listening for pain management: a multi-method study

OBJECTIVES

Music listening for pain relief is well studied in diverse healthcare settings, but its implementation remains challenging. While healthcare providers generally have a positive attitude, there is a lack of knowledge about healthcare recipients' perceptions and attitudes. Therefore, the aim of this study is to explore healthcare recipients' perceptions of listening to music for pain management, focusing on their general attitudes, implementation strategies and subjective experiences of how music helps (or does not help).

DESIGN

A multi-method study comprising a quantitative survey and qualitative interviews. It is a follow-up conducted 6 months after a randomised experimental study, which assessed the influence of different music genres on pain tolerance. At the end of the original experiment, participants received advice on listening to music in painful situations.

SETTING

Rotterdam, The Netherlands.

PARTICIPANTS

The survey involved 169 participants (age mean 30.6, SD 9.8; 61.9% female) who participated in the initial trial. Following this, 20 in-depth interviews were conducted.

OUTCOME MEASURES

Perceptions of music for pain management were investigated, revealing general trends in the quantitative survey data. Data-led thematic analysis of the qualitative interviews focused on individual perceptions.

RESULTS

Participants showed a high willingness to use music for pain relief, particularly for so-called emotional pain (eg, anxiety, stress and heartbreak). Individual attitudes varied regarding different situations, types of music and types of pain. Barriers such as not considering the option and social sensitivity within healthcare contexts were discussed. A proactive approach by healthcare professionals and autonomy of healthcare recipients were suggested to overcome these barriers. Interestingly, the 'wrong' type of music or the 'wrong' situation were mentioned as non-beneficial or even harmful.

CONCLUSIONS

Awareness of individual needs and potential negative effects is crucial for the use of music for pain relief. A proactive and personalised approach is needed to effectively implement music in healthcare.

To feel is to heal-introduction to Emotional Awareness and Expression Therapy

BACKGROUND

Persistent physical symptoms (PPS), including (primary) pain, can, according to Emotional Awareness and Expression Therapy (EAET), be precipitated, perpetuated, and prolonged by emotional processes related to unresolved trauma and psychosocial conflicts. EAET is a novel, short-term, psychodynamic- and emotion-focused psychological treatment that targets these etiological factors, intending to substantially reduce or eliminate pain and/or somatic symptoms.

OBJECTIVE

This article provides an overview of EAET's theoretical background, core treatment principles, and empirical evidence from randomized controlled trials (RCTs) in alleviating somatic symptoms in people with PPS. Moreover, the potential of EAET and future research directions are discussed.

METHODS

We report a selective literature review synthesizing the foundations and treatment characteristics of EAET and the findings from RCTs investigating EAET since 2017.

RESULTS

Grounded in psychodynamic theory, with influences from affective neuroscience and emotion-focused therapy, the core treatment principles are reframing symptom explanations, fostering emotional processing, and facilitating corrective interpersonal experiences. EAET has been implemented in various formats, including individual therapy, group therapy, and internet-administered self-help. Since 2017, seven RCTs have been published, demonstrating efficacy in reducing symptoms, which appears superior to cognitive-behavioral therapy.

CONCLUSION

EAET is particularly effective for treating chronic (primary) pain conditions such as fibromyalgia and musculoskeletal pain. However, further studies are required to evaluate its long-term efficacy, determine patient characteristics associated with positive outcomes, and better understand its most active mechanisms.

A pontine center in descending pain control

Pain sensation changes according to expectation, context, and mood, illustrating how top-down circuits affect somatosensory processing. Here, we used an intersectional strategy to identify anatomical and molecular-spatial features of supraspinal descending neurons activated by distinct noxious stimulation. This approach captured known descending pain pathways as well as spinal projecting neurons that are anatomically mapped to Barrington's nucleus in the dorsal pontine tegmentum. We determined that this population of neurons expresses corticotropin-releasing hormone in Barrington's nucleus (BarCrh) and exhibits time-locked firing in response to noxious stimulation. Chemogenetic activation of BarCrh neurons attenuated nocifensive responses as well as tactile neuropathic pain, while silencing these neurons resulted in thermal hyperalgesia and mechanical allodynia. Mechanistically, we demonstrated that pain-related input from the ventrolateral periaqueductal gray recruits BarCrh neurons, reduces ascending nociceptive transmission, and preferentially activates spinal dynorphin neurons to mediate analgesia. Our data expose a pontine inhibitory descending pathway that powerfully controls nocifensive sensory input to the brain.

Effects of psychological stress on inflammatory bowel disease via affecting the microbiota-gut-brain axis

ABSTRACT

Inflammatory bowel disease (IBD) is an idiopathic intestinal inflammatory condition with chronic and relapsing manifestations and is characterized by a disturbance in the interplay between the intestinal microbiota, the gut, and the brain. The microbiota-gut-brain axis involves interactions among the nervous system, the neuroendocrine system, the gut microbiota, and the host immune system. Increasing published data indicate that psychological stress exacerbates the severity of IBD due to its negative effects on the microbiota-gut-brain axis, including alterations in the stress response of the hypothalamic-pituitary-adrenal (HPA) axis, the balance between the sympathetic nervous system and vagus nerves, the homeostasis of the intestinal flora and metabolites, and normal intestinal immunity and permeability. Although the current evidence is insufficient, psychotropic agents, psychotherapies, and interventions targeting the microbiota-gut-brain axis show the potential to improve symptoms and quality of life in IBD patients. Therefore, further studies that translate recent findings into therapeutic approaches that improve both physical and psychological well-being are needed.

Thermosensory predictive coding underpins an illusion of pain

The human brain has a remarkable ability to learn and update its beliefs about the world. Here, we investigate how thermosensory learning shapes our subjective experience of temperature and the misperception of pain in response to harmless thermal stimuli. Through computational modeling, we demonstrate that the brain uses a probabilistic predictive coding scheme to update beliefs about temperature changes based on their uncertainty. We find that these expectations directly modulate the perception of pain in the thermal grill illusion. Quantitative microstructural brain imaging further revealed that individual variability in computational parameters related to uncertainty-driven learning and decision-making is reflected in the microstructure of brain regions such as the precuneus, posterior cingulate gyrus, cerebellum, as well as basal ganglia and brainstem. These findings provide a framework to understand how the brain infers pain from innocuous thermal inputs, with important implications for the etiology of thermosensory symptoms under chronic pain conditions.

Brain Mechanisms of Fear Reduction Underlying Habituation to Pain in Humans

Habituation to painful stimuli reflects an endogenous pain alleviation mechanism, and reduced pain habituation has been demonstrated in many chronic pain conditions. In ethology, animals exhibit reduced fear responses while habituating to repeated threatening stimuli. It remains unclear whether pain habituation in humans involves a fear reduction mechanism. In an fMRI experiment, we investigated pain-related brain responses before and after the development of habituation to pain induced by repetitive painful stimulation in healthy adults. In another behavioral experiment, we examined emotional responses in another group of healthy adults to assess pain habituation-related emotional changes. Pain habituation at the repetitively stimulated forearm site entailed reduced fear and engaged the neural system implicated in fear reduction, which included the amygdala, anterior cingulate, and ventromedial prefrontal cortex (vmPFC). Individual pain-related fear, assessed via a questionnaire, predicted neural activity within the periaqueductal gray (a pain-modulating center), which covaried with vmPFC responsivity. Moreover, pain habituation also occurred at nonstimulated sites, and its extent was predicted by habituation at the repetitively stimulated site. This phenomenon again involved the vmPFC, which has also been implicated in safety generalization under threat. These results suggest a role of fear reduction in pain habituation that is related to individual pain fearfulness. The reduced fear acquired at the repetitively stimulated site can be generalized to other body parts to cope with similar aversive situations. The identified link between fear and pain habituation helps explain why impaired fear reduction and reduced pain habituation coexist in chronic pain conditions.

Modulating neuroplasticity for chronic pain relief: noninvasive neuromodulation as a promising approach

Chronic neuropathic pain is a debilitating neuroplastic disorder that notably impacts the quality of life of millions of people worldwide. This complex condition, encompassing various manifestations, such as sciatica, diabetic neuropathy and postherpetic neuralgia, arises from nerve damage or malfunctions in pain processing pathways and involves various biological, physiological and psychological processes. Maladaptive neuroplasticity, known as central sensitization, plays a critical role in the persistence of chronic neuropathic pain. Current treatments for neuropathic pain include pharmacological interventions (for example, antidepressants and anticonvulsants), invasive procedures (for example, deep brain stimulation) and physical therapies. However, these approaches often have limitations and potential side effects. In light of these challenges, interest in noninvasive neuromodulation techniques as alternatives or complementary treatments for neuropathic pain is increasing. These methods aim to induce analgesia while reversing maladaptive plastic changes, offering potential advantages over conventional pharmacological practices and invasive methods. Recent technological advancements have spurred the exploration of noninvasive neuromodulation therapies, such as repetitive transcranial magnetic stimulation, transcranial direct current stimulation and transcranial ultrasound stimulation, as well as innovative transformations of invasive techniques into noninvasive methods at both the preclinical and clinical levels. Here this review aims to critically examine the mechanisms of maladaptive neuroplasticity in chronic neuropathic pain and evaluate the efficacy of noninvasive neuromodulation techniques in pain relief. By focusing on optimizing these techniques, we can better assess their short-term and long-term effects, refine treatment variables and ultimately improve the quality of neuropathic pain management.

Individual variability in cortical representations of tonic pain

When people experience pain in everyday situations, the experience is often long-lasting and fluctuating. However, pain research predominantly focuses on artificial brief and repeated singular painful events. Here, we aimed to approximate clinically relevant pain in 152 sessions from 38 participants who underwent four sessions each. We applied variable levels of contact heat pain to the forearm using a thermode. Participants were asked to continuously rate their pain experience through a potentiometer device. In a whole-brain approach, we related the dynamic fluctuations of cortical activity and connectivity to the time courses of pain. We also explored the variability of cortical processing across participants. In an individual approach, we compared the cortical processing pattern of each individual with the overall group findings. The results revealed a large discrepancy between the group results that are usually reported in publications and the 4-session individual processing patterns: the group findings corroborated previous work localising tonic pain encoding to the secondary somatosensory cortex. By contrast, this region was shadowed by a variety of activity patterns across individuals, represented by a low spatial correlation between group statistics and individual results. The current findings challenge the usefulness and applicability of group results. They do not inform us how pain is processed in the brain as none of the participants exhibited the processing pattern of the group statistics. Therapies to relieve pain that rely on the modulation of brain regions will fail unless they are adapted to an individual's unique pain processing characteristics.

Relationship of opioid tolerance to patient and wound factors, and wound micro-environment in patients with open wounds

OBJECTIVE

Opioid tolerance is a criterion for opioid use disorder, which is currently an epidemic in the US. Individuals with open wounds are frequently administered opioids; however, the phenomenon of opioid tolerance has not been examined in the context of wounds. The purpose of this exploratory study was to compare patient/wound factors, wound microbiome and inflammatory mediators between individuals who were opioid-tolerant versus those who were not opioid-tolerant.

METHOD

Patients with acute open wounds were enrolled in this cross-sectional study. All study data were collected before and during a one-time study dressing change.

RESULTS

The study included a total of 385 participants. Opioid-tolerant participants were significantly younger (p<0.0001); had higher levels of depression (p=0.0055) and anxiety (p=0.0118); had higher pain catastrophising scores (p=0.0035); reported higher resting wound pain (p<0.0001); had a higher number of wounds of <30 days' duration (p=0.0486); and had wounds with lower bacterial richness (p=0.0152) than participants who were not opioid-tolerant. A backward elimination logistic regression model showed that four predictors-resting wound pain, age, bacterial richness and depression-were the most important variables in predicting opioid-tolerance status.

CONCLUSION

These findings provide the first insights into the phenomenon of opioid tolerance in the context of open wounds. This study provides findings from which to guide hypothesis-driven research in the future.

Brain connectivity in individuals with migraine resets during the headache phase: a whole-brain connectivity study

Episodic migraine is reflected by cyclic changes in behavior and cortical processing. We aimed to identify how functional connectivity changes over the entire migraine cycle. By using longitudinal neuroimaging and a whole-brain connectivity analysis approach, we tested 12 episodic migraine patients across 82 functional MRI recordings during spontaneous migraine headaches with follow-up measurements over the pain-free interval without any external stimulation. We found that the functional connectivity linearly increased over the interictal interval. In the prodromal phase, we observed the strongest connections between the anterior agranular insula and the posterior orbitofrontal cortex with sensory, motor and cingulate areas. The strength of the connections dropped during the headache. Peak connectivity during the prodromal phase and its collapse during the headache can be regarded as a mechanism of normalizing cortical processing. We speculate about a malfunction at the molecular level in agranular frontal and insular regions, which needs to be addressed in subsequent studies.

The Role of Maladaptive Plasticity in Modulating Pain Pressure Threshold Post-Spinal Cord Injury

BACKGROUND

Spinal cord injury (SCI) frequently leads to pain, leading to significant disability. Pain sensitization, a key feature of SCI, is commonly assessed via quantitative sensory testing like the Pressure Pain Threshold (PPT), though the factors influencing PPT changes remain unclear. This study hypothesizes that specific clinical and neurophysiological factors modulate PPT in SCI patients. The primary objective is to identify predictors of PPT in SCI patients.

METHODS

We conducted a cross-sectional analysis of neurophysiological, clinical, and demographic data from 102 SCI patients in an ongoing prospective cohort study called "Deficit of Inhibition as a Marker of Neuroplasticity" (DEFINE study). Multivariable regression analyses were used to evaluate demographic, clinical, and functional variables associated with PPT, the primary outcome measure.

RESULTS

The sample comprised 87.9% males with an average age of 41. Trauma was the leading cause of SCI (77.45%), predominantly affecting the cervical and thoracic levels. Pain was reported by 44% of participants, and the mean PPT was 8.3 kPa, measured bilaterally. Multivariate analysis of PPT in the left, right, and bilateral thenar regions revealed consistent trends. Significant negative associations were found between bilateral PPT and low beta EEG frequency in the central area (β = -14.94, p = 0.017), traumatic lesion etiology (β = -1.99, p = 0.038), and incomplete lesions by the American Spinal Injury Association classification (β = -1.68, p = 0.012). In contrast, positive associations were observed with age (β = 0.08, p < 0.001).

CONCLUSIONS

Our findings show that increased beta oscillations and traumatic brain injury having a lower PPT indicate that factors associated with maladaptive plasticity are associated with decreased and likely less functional PPT. On the other hand, increased motor function may help to regulate PPT in a more functional status.

A septo-hypothalamic-medullary circuit directs stress-induced analgesia

Stress is a potent modulator of pain. Specifically, acute stress due to physical restraint induces stress-induced analgesia (SIA). However, where and how acute stress and pain pathways interface in the brain are poorly understood. Here, we describe how the dorsal lateral septum (dLS), a forebrain limbic nucleus, facilitates SIA through its downstream targets in the lateral hypothalamic area (LHA) of mice. Taking advantage of transsynaptic viral-genetic, optogenetic, and chemogenetic techniques, we show that the dLS→LHA circuitry is sufficient to drive analgesia and is required for SIA. Furthermore, our results reveal that the dLS→LHA pathway is opioid-dependent and modulates pain through the pro-nociceptive neurons in the rostral ventromedial medulla (RVM). Remarkably, we found that the inhibitory dLS neurons are recruited specifically when the mice struggle to escape under restraint and, in turn, inhibit excitatory LHA neurons. As a result, the RVM neurons downstream of LHA are disengaged, thus suppressing nociception. Together, we delineate a poly-synaptic pathway that can transform escape behavior in mice under restraint to acute stress into analgesia.

Comparative effectiveness of various exercise interventions on central sensitisation indices: A systematic review and network meta-analysis

BACKGROUND

Central sensitisation (CS) increases musculoskeletal pain. Quantitative sensory testing (QST) or self-report questionnaires might indicate CS. Indices of CS might be suppressed by exercise, although the optimal exercise regimen remains unclear.

OBJECTIVES

We conducted a systematic review and network meta-analysis (NMA) to investigate effectiveness of different exercise regimens on these CS indices in adults.

METHODS

We searched 6 electronic databases from inception to November 2023. Meta-analysis of randomised controlled trials (RCTs) investigated effects of exercise on all CS indices. Two independent reviewers assessed risk of bias. NMA of RCTs compared CS indices between exercise types. Sensitivity analysis using only high-quality studies was performed to verify the robustness of our results. Certainty was assessed using the GRADE approach.

RESULTS

Of the 249 eligible studies identified, 164 were RCTs, of which 89 provided data suitable for NMA. Meta-analysis revealed large improvement of post-intervention CS indices compared to baseline (SMD -0.81, 95 % CI -0.93 to -0.70). All reported categories of exercise, except stretching exercise alone, were more effective than non-exercise controls. Combined exercises that include stretching together with strengthening exercises (SMD -1.67, 95 % Credible Interval (CrI) -2.41 to -0.97), or strengthening, stretching and aerobic components (SMD -1.61, 95 % CrI -2.74 to -0.56) were most effective at reducing CS indices compared to non-exercise controls. Sensitivity analysis confirmed the robustness of our findings, particularly for combined stretching and strengthening exercise.

CONCLUSIONS

Our meta-analysis suggested that various exercise interventions are effective in improving CS. Multi-component exercise tends to be the most effective, but some exercise combinations might be better than others. Combined exercise featuring strengthening and stretching components, with or without aerobic exercise, shows the greatest likelihood among other combinations of being the optimal exercise type. These findings might have utility informing future trials and personalising treatment strategies for people with CS features.

How control modulates pain

Pain, an indicator of potential tissue damage, ideally falls under individual control. Although previous work shows a trend towards reduced pain in contexts where pain is controllable, there is a large variability across studies that is probably related to different aspects of control. We therefore outline a taxonomy of different aspects of control relevant to pain, sketch how control over pain can be integrated into a Bayesian pain model, and suggest changes in expectations and their precision as potential mechanisms. We also highlight confounding cognitive factors, particularly predictability, that emphasize the necessity for careful experimental designs. Finally, we describe the neurobiological underpinnings of how control affects pain processing in studies using different types of control, and highlight the roles of the anterior insula, middle frontal gyrus (MFG), and anterior cingulate cortex (ACC).

A proposed test to determine physical working capacity at pain intensity threshold (PWCPIT)

PURPOSE

This study aimed to establish a new threshold parameter called the physical working capacity at pain intensity threshold (PWCPIT) using a pain intensity scale and mathematical methods similar to those used to develop the physical working capacity at oxygen consumption threshold (PWCVO2) and physical working capacity at heart rate threshold (PWCHRT). The study had two objectives: (i) to examine the relationship between PWCPIT and traditional PWC measures and (ii) to explore the physiological mechanisms underlying the relationship between pain perception and capacity thresholds.

METHODS

Fourteen male volunteers (age 21 ± 2 years, height 176 ± 6 cm, weight 76 ± 9 kg, VO2peak 37.8 ± 7.8 ml/kg/min-1) underwent an incremental exhaustion test and four 8-min randomly ordered work bouts on different days at 70-100% peak power output (119-320 W) to establish their PWCPIT, PWCHRT and PWCVO2. One-way repeated-measures ANOVA with Bonferroni post hoc tests and a zero-order correlation matrix were used to analyze these thresholds.

RESULTS

PWCPIT significantly correlated with PWCHRT (r = 0.88, P < 0.001), PWCVO2 (r = 0.84, P < 0.001), and gas exchange threshold (GET) (r = 0.7, P = 0.006).

CONCLUSION

The model for estimating PWCHRT and PWCVO2 can be applied to determine the PWCPIT. By examining how PWCPIT aligns with, differs from, or complements existing PWC threshold measures, researchers may provide a more comprehensive understanding of the factors that govern endurance performance.

Glial activation and nociceptive neuropeptide elevation associated with the development of chronic post-traumatic headache following repetitive blast exposure

Chronic headaches and pain are prevalent in those who are exposure to blast events, yet there is a gap in fundamental data that identifies the pathological mechanism for the chronification of pain. Blast-related post-traumatic headaches (PTH) are understudied and chronic pain behaviors in preclinical models can be vital to help elucidate PTH mechanisms. The descending pain modulatory system controls pain perception and involves specific brain regions such as the cortex, thalamus, pons, and medulla. In this study, male rats were exposed to repeated blast events to induce traumatic brain injury (bTBI) and subsequently assessed for the development of PTH by testing for chronic pain behaviors and examining the neuropathology of the descending pain pathway. The results demonstrated that facial hypersensitivity developed as early as week two following bTBI and persisted throughout the study (12 weeks). Depressive-like behaviors were observed at 12 weeks following bTBI, and these behaviors were associated with neuropathologies such as microglia ramification and neuropeptide elevation (Calcitonin Gene-Related Peptide, CGRP; Substance P, SP). Overall, these findings support the hypothesis that bTBI causes the activation of microglia and elevation of neuropeptides, which contribute to the development of chronic PTH behaviors.

Management of Refractory Functional Gastrointestinal Disorders: What Role Should Psychiatrists Have?

Currently, it has been stated that psychiatric and psychological problems are equally paramount aspects of the clinical modulation and manifestation of both the central nervous and digestive systems, which could be used to restore balance. The present narrative review aims to provide an elaborate description of the bio-psycho-social facets of refractory functional gastrointestinal disorders, psychiatrists' role, specific psychiatric approach, and the latest psychiatric and psychological perspectives on practical therapeutic management. In this respect, "psyche," "psychiatry," "psychology," "psychiatrist," "psychotropic," and "refractory functional gastrointestinal disorders" (as the keywords) were searched in relevant English publications from January 1, 1950, to March 1, 2024, in the PubMed, Web of Science, Scopus, EMBASE, Cochrane Library, and Google Scholar databases. Eventually, the narrative technique was adopted to reach a compelling story with a high level of cohesion through material synthesis. The current literature recognizes the brain-gut axis modulation as a therapeutic target for refractory functional gastrointestinal disorders and the bio-psycho-social model as an integrated framework to explain disease pathogenesis. The results also reveal some evidence to affirm the benefits of psychotropic medications and psychological therapies in refractory functional gastrointestinal disorders, even when psychiatric symptoms were absent. It seems that psychiatrists are required to pay higher levels of attention to both the assessment and treatment of patients with refractory functional gastrointestinal disorders, accompanied by educating and training practitioners who take care of these patients.

Comparisons of the effects of psychologically-informed and usual physiotherapy on pain sensitivity in chronic low back pain: an exploratory randomized controlled trial

Introduction

The presence of altered central pain processing and modulation, as well as negative psychological factors, have been suggested to impede recovery in chronic low back pain (CLBP). Psychologically-informed physiotherapy (PiP) aims to specifically address the latter factors-in addition to physical factors-to improve treatment effects. This study aims to determine if the effect of PiP is superior to usual physiotherapy (UP) on pain sensitivity and modulation in participants with CLBP and if changes in these variables were associated with changes in clinical outcomes.

Methods

Forty participants with CLBP were randomly allocated to PiP or UP. Seven physiotherapy sessions over 6 weeks plus a booster session at an 11-week follow-up were delivered. Pressure pain threshold (PPT), temporal summation of pain (TSP), and exercise-induced hypoalgesia were assessed on lumbar, upper, and lower limb sites at baseline and after 6 weeks. Linear mixed models tested if PiP was superior to UP on pain sensitivity/modulation. Linear regressions tested if pain sensitivity/modulation changes were associated with changes in clinical outcomes (pain intensity, physical functioning, symptoms of central sensitization).

Results

PiP was not superior to UP to modulate pain sensitivity/modulation variables. All PPTs increased after 6 weeks regardless of the approach. Lumbar PPT and lumbar and lower limb TSP changes were associated with physical functioning changes.

Conclusion

Although our study suggests that neither approach has a superiority to impact on pain sensitivity, both approaches elicited widespread hypoalgesia. Future powered trials should verify if pain sensitivity can be a mediator of physical functioning improvement, as suggested by our results.

Pain is what you think: functional magnetic resonance imaging evidence toward a cognitive and affective approach for pain research

The sensory/discriminative domain of pain is often given more consideration than the cognitive and affective influences that ultimately make pain what it is: a highly subjective experience that is based on an individual's life history and experiences. While many investigations of the underlying mechanisms of pain have focused on solely noxious stimuli, few have compared somatosensory stimuli that cross the boundary from innocuous to noxious. Of those that have, there is little consensus on the similarities and differences in neural signaling across these sensory domains. The purpose of this study was to apply our established network connectivity analyses toward the goal of understanding the neural mechanisms behind sensory, cognitive, and affective responses to noxious and innocuous stimuli. Functional MRI data were collected from 19 healthy women and men that experienced warm and hot thermal stimuli across multiple trials. This is a within-subjects cross-sectional experimental study with repeated measures. Ratings of stimulus intensity and unpleasantness that were collected during each run confirmed significant perceptual differences between the two types of stimuli. Despite this finding, no group differences in network connectivity were found across conditions. When individual differences related to pain ratings were investigated, subtle differences were found in connectivity that could be attributed to sensory and association regions in the innocuous condition, and cognitive, affective, and autonomic regions in the pain condition. These results were reflected in the time-course data for each condition. Overall, signaling mechanisms for innocuous and noxious somatosensation are intricately linked, but pain-specific perception appears to be driven by our psychological and autonomic states.

Altered connectivity of central autonomic network: effects of dysautonomia in hereditary transthyretin amyloidosis with polyneuropathy

BACKGROUND

Hereditary transthyretin amyloidosis with polyneuropathy (ATTRv-PN) is a progressive fatal disorder caused by deposition of mutant transthyretin (TTR) amyloids mainly in the nerves and heart. Autonomic dysfunction is a major disabling manifestation, affecting 90% of patients with late-onset ATTRv-PN. The current study aimed to investigate brain functional alterations associated with dysautonomia due to peripheral autonomic nerve degeneration in ATTRv-PN.

METHODS

Resting-state functional MRI data were acquired from 43 ATTRv-PN patients predominantly of A97S (p.A117S) genotype, and the functional connectivity of central autonomic regions was assessed.

RESULTS

Compared with age-matched healthy controls, the ATTRv-PN patients exhibited (1) reduced functional connectivity of the central autonomic regions such as hypothalamus, amygdala, anterior insula, and middle cingulate cortex with brain areas of the limbic, frontal, and somatosensory systems, and (2) correlations of reduced functional autonomic connectivity with the severity of autonomic dysfunction especially orthostatic intolerance, decreased heart rate variability, and greater clinical disability.

CONCLUSIONS

Our findings provide evidence linking peripheral autonomic dysfunction with altered connectivity in the central autonomic network in ATTRv-PN.

How to Distinguish Non-Inflammatory from Inflammatory Pain in RA?

PURPOSE OF THE REVIEW

Managing non-inflammatory pain in rheumatoid arthritis (RA) can be a huge burden for the rheumatologist. Pain that persists despite optimal RA treatment is extremely challenging for patient and physician alike. Here, we outline the latest research relevant to distinguishing non-inflammatory from inflammatory RA pain and review the current understanding of its neurobiology and management.

RECENT FINDINGS

Nociplastic pain is a recently introduced term by the international pain community. Its definition encompasses the non-inflammatory pain of RA and describes pain that is not driven by inflamed joints or compromised nerves, but that is instead driven by a functional reorganisation of the central nervous system (CNS). Insights from all areas of nociplastic pain research, including fibromyalgia, support a personalised pain management approach for non-inflammatory pain of RA, with evidence-based guidelines favouring use of non-pharmacological interventions. Future developments include novel CNS targeting pharmacotherapeutic approaches to treat nociplastic pain.

Mechanism of Action of Mindfulness-Based Interventions for Pain Relief-A Systematic Review

Background: Currently, no systematic evidence synthesis of the mechanism of action of mindfulness-based approaches exists for pain conditions. Aim: To identify and synthesize experimental and clinical studies examining aspects of the mechanism of action of mindfulness for pain relief. Methods: The following databases and search interfaces were searched: Embase (via Embase.com) and Medline (via PubMed). Additional references were identified via bibliographies of included studies. The following were the inclusion criteria applied: (1) original studies published in peer-reviewed journals, (2) in adult populations that (3) examined the mechanism of action of mindfulness meditation on pain outcomes or (4) provided conclusions regarding the potential mechanism of action of mindfulness meditation. The studies were selected by two independent reviewers. Discrepancies were resolved by discussion. Results: A total of 21 studies published in English met the inclusion criteria, of which 5 studies were clinical studies, which included patients with chronic pain, and 16 studies used experimental pain induction. The investigation into brain mechanisms through functional magnetic resonance imaging and diffusion tensor imaging revealed mindfulness meditation's ability to modulate brain activity, particularly in the anterior cingulate cortex, anterior insula, and orbitofrontal cortex, and to enhance structural and functional connectivity in regions associated with pain perception. Regarding the role of opioids, findings across five studies indicated that the analgesic effects of mindfulness are maintained even when opioid receptors are blocked, suggesting a nonopioidergic pathway for pain modulation. Pain perception studies highlighted that mindfulness practices foster pain acceptance and modify pain control beliefs, serving as key mediators in improving pain outcomes. For experienced versus novice mindfulness practitioners, results demonstrated that long-term practice enhances pain threshold and reduces pain unpleasantness through increased activity in salience and attentional control regions. Conclusion: This systematic review highlights mindfulness meditation as a multifaceted approach to pain management, utilizing mechanisms such as cognitive and emotional reappraisal, nonopioidergic pathways, and enhanced attention in control regions. It emphasizes the role of mindfulness in fostering pain acceptance and altering pain control perceptions, showcasing its broad impact on the neurological and experiential dimensions of pain. However, the predominance of studies on healthy subjects and methodological variations across experiments necessitates careful interpretation of the findings. The review calls for further research to explore the mechanisms of mindfulness in chronic pain populations more deeply, distinguishing the specific effects of mindfulness from nonspecific effects and expanding its applicability in clinical settings for chronic pain management.

Rasch Analysis of the Chinese Version of the Nociception Coma Scale-Revised in Patients with Prolonged Disorders of Consciousness

OBJECTIVES

The aim of this study was to analyze the Chinese version of the Nociception Coma Scale-Revised in patients with prolonged disorders of consciousness within the framework of Rasch modeling, including investigating the invariance of total scores across different etiologies of disorders of consciousness.

DESIGN

Prospective psychometric study.

PARTICIPANTS

Patients with prolonged disorders of consciousness from the Rehabilitation and Neurology units in hospital.

INTERVENTIONS

None.

MAIN OUTCOME MEASURE

The Nociception Coma Scale-Revised was undertaken by trained raters and the Coma Recovery Scale-Revised was used to assess patients' consciousness. The psychometric properties within the Rasch model including item-person targeting, reliability and separation, item fit, unidimensionality, and differential item functioning were assessed.

RESULTS

84 patients with prolonged disorders of consciousness (mean age 53 years; mean injury 5 months; 42 with Minimally Conscious State and 42 with Unresponsive Wakefulness Syndrome) of 252 observations were enrolled in the study. Through the procedure of repeated assessment and differential item function, a lower item bias Rasch set was purified. The Rasch model assumptions were examined and met, with item reliability and validity meeting the recommended threshold.

CONCLUSIONS

The Chinese version of the Nociception Coma Scale-Revised demonstrated unidimensionality, good reliability and separation, and good item fit, but dissatisfied person fit and item-person targeting. The verbal subscale showed a notable discrepancy between person responses and the difficulty of the items, suggesting limited clinical significance.

The Evil Twins of Chronic Pelvic Pain Syndrome: A Systematic Review and Meta-Analysis on Interstitial Cystitis/Painful Bladder Syndrome and Endometriosis

BACKGROUND

Chronic pelvic pain is a debilitating condition affecting quality of life. Endometriosis is one of the leading causes of CPP, but recent studies highlighted the role of interstitial cystitis/bladder pain syndrome (IC/PBS) in causing CPP. Only some studies addressed the coexistence of these two conditions, which seems more frequent than what is supposed, leading to diagnostic delays and unnecessary surgeries. This systematic review aimed to evaluate the estimate of the prevalence of the comorbidity of endometriosis and IC/PBS.

METHODS

We performed a systematic review of the literature indexed on PubMed, Scopus, ISI Web of Science, and Cochrane using a combination of keywords and text words represented by "painful bladder syndrome", "endometriosis", "interstitial cystitis", and "bladder pain syndrome". We performed a meta-analysis of the results.

RESULTS

The meta-analysis shows that the coexistence of endometriosis and IC/PBS in women with CPP ranged from 15.5% to 78.3%, which is higher than the prevalence of IC/PBS in the general population.

CONCLUSIONS

Prevalence data about the coexistence of endometriosis and IC/PBS are highly heterogeneous, probably due to the paucity of available data. However, in cases of endometriosis unresponsive to treatment, other reasons for CPP (such as IC/PBS) need to be ruled out.

Intensity dependence of auditory evoked potentials distinguish participants with unmedicated depression from non-depressed controls

Depression is a heterogeneous syndrome that impacts an individual's emotional, social, cognitive and bodily functioning. Depression is associated with biases in emotional processing, but alterations in basic sensory processing have received less attention in depression research. Here, we measured event-related potentials (ERPs) in response to changes in the intensity of auditory stimuli and the location of somatosensory stimuli in participants with depression and in non-depressed control participants. We tested whether auditory mismatch negativity, P3a or N1 intensity dependence response or somatosensory mismatch response, P3a, P50 or N80 can dissociate depressed participants and non-depressed controls, and we also analysed the effects of depression medication and age in this sample. N1 intensity dependence response was increased in unmedicated depressed participants relative to non-depressed controls. When age was controlled for in the analysis, the effect of depression was only at a trend level. N1 intensity dependence response correlated with depression severity at the whole sample level. We did not observe any depression-related alterations in auditory mismatch negativity or P3a or somatosensory ERPs. Our results may reflect an association between the N1 intensity dependence response and altered neurotransmitter activity in depression, but this should be confirmed in future studies.

Pain-Discriminating Information Decoded From Spatiotemporal Patterns of Hemodynamic Responses Measured by fMRI in the Human Brain

Functional magnetic resonance imaging (fMRI) has been widely used in studying the neural mechanisms of pain in the human brain, primarily focusing on where in the brain pain-elicited neural activities occur (i.e., the spatial distribution of pain-related brain activities). However, the temporal dynamics of pain-elicited hemodynamic responses (HDRs) measured by fMRI may also contain information specific to pain processing but have been largely neglected. Using high temporal resolution fMRI (TR = 0.8 s) data acquired from 62 healthy participants, in the present study we aimed to test whether pain-distinguishing information could be decoded from the spatial pattern of the temporal dynamics (i.e., the spatiotemporal pattern) of HDRs elicited by painful stimuli. Specifically, the peak latency and the response duration were used to characterize the temporal dynamics of HDRs to painful laser stimuli and non-painful electric stimuli, and then were compared between the two conditions (i.e., pain and no-pain) using a voxel-wise univariate analysis and a multivariate pattern analysis. Furthermore, we also tested whether the two temporal characteristics of pain-elicited HDRs and their spatial patterns were associated with pain-related behaviors. We found that the spatial patterns of HDR peak latency and response duration could successfully discriminate pain from no-pain. Interestingly, we also observed that the Pain Vigilance and Awareness Questionnaire (PVAQ) scores were correlated with the average response duration in bilateral insula and secondary somatosensory cortex (S2) and could also be predicted from the across-voxel spatial patterns of response durations in the middle cingulate cortex and middle frontal gyrus only during painful condition but not during non-painful condition. These findings indicate that the spatiotemporal pattern of pain-elicited HDRs may contain pain-specific information and highlight the importance of studying the neural mechanisms of pain by taking advantage of the high sensitivity of fMRI to both spatial and temporal information of brain responses.

Development and validation of the Italian version of the pain attitudes and beliefs scale-musculoskeletal (PABS-MSK) among physiotherapists working with patients with musculoskeletal chronic pain

BACKGROUND

Due to their high prevalence, long-term disability, work absenteeism, and low productivity capacity they often lead to, nociplastic and chronic pain are a major public health and social concern. Although high-level literature recommends the Biopsychosocial model, the traditional Biomedical approach is still very diffuse in clinical practise. It is recognized that the beliefs and attitudes of clinicians have an impact on those of patients. The Exploratory Factor Analysis (EFA) was used to validate the Italian version of the PABS-MSK questionnaire.

OBJECTIVES

The aim of this study was to translate the original PABS-MSK items into Italian and then assess the construct validity of the new Italian version of the PABS-MSK questionnaire, addressed to physiotherapists, to gain knowledge about physiotherapists' attitudes and beliefs toward the management of chronic musculoskeletal pain and to correlate them with individual characteristics.

METHODS

An EFA was performed to validate the modified-Italian-PABS-MSK questionnaire. Furthermore, multivariable regression models were implemented to assess any statistically significant differences in the total score of the two dimensions for sociodemographic and occupational characteristics.

RESULTS

The sample consisted of 563 subjects who are members of the order of physiotherapists. The Parallel Analysis suggested extracting two factors, and the EFA showed that the first scale (which we called Biopsychosocial) had higher factor loadings values, while two items (7 and 19) did not adequately represent the other scale (Biomedical). Moreover, the regression models showed that younger and freelance clinicians are more prone to adhere to the Biopsychosocial model.

CONCLUSIONS

The modified-Italian-PABS-MSK questionnaire appears to measure two factors related to the Biopsychosocial and Biomedical beliefs of physiotherapists in the management of chronic musculoskeletal pain. The results suggest that professional training based on the evidence and recommendations of international guidelines is necessary to improve the adherence of physiotherapists to the Biopsychosocial model. However, additional studies are needed to further validate the scales, and assess the test-retest reliability, responsiveness, and construct validity.

Home-based EEG Neurofeedback for the Treatment of Chronic Pain: A Randomized Controlled Clinical Trial

This parallel, 2-arm, blinded, randomized controlled superiority trial examined whether, when added to usual care, active-electroencephalography neurofeedback (EEG NFB) was safe and more effective than sham control-EEG NFB for chronic pain. In total, 116 participants with chronic pain were randomly assigned (1:1) to usual care plus ≥32 sessions of active-EEG NFB upregulating relative alpha power over C4 or usual care plus ≥32 sessions of sham control-EEG NFB. Per-protocol analyses revealed no significant between-group differences in the primary outcome, Brief Pain Inventory average pain (mean difference [95% confidence interval]: -.04 [-.39 to .31], P = .90), or any secondary outcomes. However, 44% of participants in the active-EEG NFB group and 45% in the control-EEG NFB group reported at least a moderate (≥30%), clinically important improvement in Brief Pain Inventory average pain. The number of treatment-emergent adverse events were similar in both groups (P = .83), and none were serious. Post hoc analyses revealed similar upregulated relative alpha power in both groups during training, with concordant positive rewards delivered to the active-EEG group 100% of the time and the control-EEG group ∼25% of the time, suggesting a partially active sham intervention. When added to usual care, the active-EEG NFB intervention used in this study was not superior to the sham control-EEG NFB intervention. However, a large proportion of participants in both groups reported a clinically important reduction in pain intensity. A partially active sham intervention may have obscured between-group differences. The intervention was free of important side effects, with no safety concerns identified. PERSPECTIVE: This study is the first attempt at an appropriately blinded, randomized, sham-controlled trial of alpha EEG NFB for the treatment of chronic pain. The findings may interest people living with chronic pain, clinicians involved in chronic pain management, and may inform the design of future EEG NFB trials. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry (ANZCTR): ACTRN12621000667819.

Respiratory Depression Associated with Opioids: A Narrative Review

OPINION

All opioids have a risk of causing respiratory depression and reduced cerebral circulation. Fentanyl has the greatest risk of causing both. This is particularly a concern when combined with illicit opioids such as diamorphine (also known as heroin). Fentanyl should not be used as a frontline potent opioid due its significant risks. Buprenorphine, a schedule III opioid, morphine, or hydromorphone is preferred, followed by oxycodone, which has a significant risk of abuse relative to buprenorphine and morphine. Although all opioids were equally effective in producing analgesia, the relative safety of each opioid is no longer a secondary concern when prescribing. In the face of an international opioid epidemic, clinicians need to choose opioid analgesics safely, wisely, and carefully.

Altered Endogenous Pain-Inhibitory Function in Older Adults With Chronic Pain Is Associated With Disruptions in Functional Connectivity During Resting State

Increasing research points to a decline in the ability to internally regulate pain as a contributing factor to the increased pain susceptibility in aging. This study investigated the connection between pain regulation and resting-state functional connectivity (rsFC) in older adults with chronic pain. We compared functional magnetic resonance imaging rsFC of 30 older adults with chronic pain (69.5 ± 6.58 years, 14 males), 29 pain-free older (70.48 ± 4.60, 15 males), and 30 younger adults (20.0 ± 1.58, 15 males). Pain inhibition and facilitatory capabilities were assessed using conditioned pain modulation (CPM) and temporal summation. Older adults with chronic pain displayed lower pain inhibition during the CPM than pain-free older and younger adults. rsFC analysis showed that older adults with chronic pain, in comparison with younger participants, displayed an abnormal hyperconnectivity between right dorsolateral prefrontal cortex and left amygdala, which was significantly correlated with lower pain inhibition during the CPM. Older adults with chronic pain displayed higher connectivity between the primary somatosensory cortex and nucleus accumbens than pain-free older adults. Finally, both older adult groups displayed reduced connectivity between brain structures involved in pain inhibition and processing in comparison with younger adults. Altogether, our results suggest that suffering from pain during aging leads to a dysfunction of pain-inhibitory processes, which significantly surpass those caused by normal aging. Furthermore, our results point to a key role of emotional and motivational brain areas, and their interaction with executive and somatosensory areas, in the reduced inhibitory capacity and likely the maintenance of chronic pain in aging. PERSPECTIVE: This study examines the link between reduced pain-inhibition capacity and increased resting-state connectivity between affective, sensory, and executive brain structures in older adults with chronic pain. These findings could inform new pain assessment and treatment programs for this population.

Spatiotemporal integration of contextual and sensory information within the cortical hierarchy in human pain experience

Pain is not a mere reflection of noxious input. Rather, it is constructed through the dynamic integration of current predictions with incoming sensory input. However, the temporal dynamics of the behavioral and neural processes underpinning this integration remain elusive. In the current study involving 59 human participants, we identified a series of brain mediators that integrated cue-induced expectations with noxious inputs into ongoing pain predictions using a semicircular scale designed to capture rating trajectories. Temporal mediation analysis revealed that during the early-to-mid stages of integration, the frontoparietal and dorsal attention network regions, such as the lateral prefrontal, premotor, and parietal cortex, mediated the cue effects. Conversely, during the mid-to-late stages of integration, the somatomotor network regions mediated the effects of stimulus intensity, suggesting that the integration occurs along the cortical hierarchy from the association to sensorimotor brain systems. Our findings advance the understanding of how the brain integrates contextual and sensory information into pain experience over time.

Probing white matter microstructure in youth with chronic pain and its relation to catastrophizing using neurite orientation dispersion and density imaging

ABSTRACT

Chronic pain is common in young people and can have a major life impact. Despite the burden of chronic pain, mechanisms underlying chronic pain development and persistence are still poorly understood. Specifically, white matter (WM) connectivity has remained largely unexplored in pediatric chronic pain. Using diffusion-weighted imaging, this study examined WM microstructure in adolescents (age M = 15.8 years, SD = 2.8 years) with chronic pain (n = 44) compared with healthy controls (n = 24). Neurite orientation dispersion and density imaging modeling was applied, and voxel-based whole-white-matter analyses were used to obtain an overview of potential alterations in youth with chronic pain and tract-specific profile analyses to evaluate microstructural profiles of tracts of interest more closely. Our main findings are that (1) youth with chronic pain showed widespread elevated orientation dispersion compared with controls in several tracts, indicative of less coherence; (2) signs of neurite density tract-profile alterations were observed in several tracts of interest, with mainly higher density levels in patients; and (3) several WM microstructural alterations were associated with pain catastrophizing in the patient group. Implicated tracts include both those connecting cortical and limbic structures (uncinate fasciculus, cingulum, anterior thalamic radiation), which were associated with pain catastrophizing, as well as sensorimotor tracts (corticospinal tract). By identifying alterations in the biologically informative WM microstructural metrics orientation dispersion and neurite density, our findings provide important and novel mechanistic insights for understanding the pathophysiology underlying chronic pain. Taken together, the data support alterations in fiber organization as a meaningful characteristic, contributing process to the chronic pain state.

Bedside Neuromodulation of Persistent Pain and Allodynia with Caloric Vestibular Stimulation

BACKGROUND

Caloric vestibular stimulation (CVS) is a well-established neurological diagnostic technique that also induces many phenomenological modulations, including reductions in phantom limb pain (PLP), spinal cord injury pain (SCIP), and central post-stroke pain.

OBJECTIVE

We aimed to assess in a variety of persistent pain (PP) conditions (i) short-term pain modulation by CVS relative to a forehead ice pack cold-arousal control procedure and (ii) the duration and repeatability of CVS modulations. The tolerability of CVS was also assessed and has been reported separately.

METHODS

We conducted a convenience-based non-randomised single-blinded placebo-controlled study. Thirty-eight PP patients were assessed (PLP, n = 8; SCIP, n = 12; complex regional pain syndrome, CRPS, n = 14; non-specific PP, n = 4). Patients underwent 1-3 separate-day sessions of iced-water right-ear CVS. All but four also underwent the ice pack procedure. Analyses used patient-reported numerical rating scale pain intensity (NRS-PI) scores for pain and allodynia.

RESULTS

Across all groups, NRS-PI for pain was significantly lower within 30 min post-CVS than post-ice pack (p < 0.01). Average reductions were 24.8% (CVS) and 6.4% (ice pack). CRPS appeared most responsive to CVS, while PLP and SCIP responses were less than expected from previous reports. The strongest CVS pain reductions lasted hours to over three weeks. CVS also induced substantial reductions in allodynia in three of nine allodynic CRPS patients, lasting 24 h to 1 month. As reported elsewhere, only one patient experienced emesis and CVS was widely rated by patients as a tolerable PP management intervention.

CONCLUSIONS

Although these results require interpretative caution, CVS was found to modulate pain relative to an ice pack control. CVS also modulated allodynia in some cases. CVS should be examined for pain management efficacy using randomised controlled trials.

Advances and challenges in neuroimaging-based pain biomarkers

Identifying neural biomarkers of pain has long been a central theme in pain neuroscience. Here, we review the state-of-the-art candidates for neural biomarkers of acute and chronic pain. We classify these potential neural biomarkers into five categories based on the nature of their target variables, including neural biomarkers of (1) within-individual perception, (2) between-individual sensitivity, and (3) discriminability for acute pain, as well as (4) assessment and (5) prospective neural biomarkers for chronic pain. For each category, we provide a synthesized review of candidate biomarkers developed using neuroimaging techniques including functional magnetic resonance imaging (fMRI), structural magnetic resonance imaging (sMRI), and electroencephalography (EEG). We also discuss the conceptual and practical challenges in developing neural biomarkers of pain. Addressing these challenges, optimal biomarkers of pain can be developed to deepen our understanding of how the brain represents pain and ultimately help alleviate patients' suffering and improve their well-being.

Towards non-invasive imaging through spinal-cord generated magnetic fields

Non-invasive imaging of the human spinal cord is a vital tool for understanding the mechanisms underlying its functions in both healthy and pathological conditions. However, non-invasive imaging presents a significant methodological challenge because the spinal cord is difficult to access with conventional neurophysiological approaches, due to its proximity to other organs and muscles, as well as the physiological movements caused by respiration, heartbeats, and cerebrospinal fluid (CSF) flow. Here, we discuss the present state and future directions of spinal cord imaging, with a focus on the estimation of current flow through magnetic field measurements. We discuss existing cryogenic (superconducting) and non-cryogenic (optically-pumped magnetometer-based, OPM) systems, and highlight their strengths and limitations for studying human spinal cord function. While significant challenges remain, particularly in source imaging and interference rejection, magnetic field-based neuroimaging offers a novel avenue for advancing research in various areas. These include sensorimotor processing, cortico-spinal interplay, brain and spinal cord plasticity during learning and recovery from injury, and pain perception. Additionally, this technology holds promise for diagnosing and optimizing the treatment of spinal cord disorders.

To Be in Pain: Pain Multidimensional Questionnaire as Reliable Tool to Evaluate Multifaceted Aspects of Pain

Background/Objectives: Pain is a multidimensional experience influenced by sensory, emotional, and cognitive factors. Traditional pain assessments often fail to capture this complexity. This study aimed to develop and validate the Pain Multidimensional Questionnaire (Pa-M-QU), a new self-report tool designed to assess pain catastrophizing, sensitivity, and coping strategies. Methods: Two independent samples of Italian-speaking participants, aged 18 and above, were recruited online. The first sample (n = 392; mean age = 29.36) was used for exploratory factor analysis (EFA), and the second sample (n = 123; mean age = 28.0) for confirmatory factor analysis (CFA). Pearson's correlations and convergent validity analyses were conducted. Results: From an initial pool of 59 items identified through focus group discussions, 35 items were removed based on reliability analysis. The final 24-item Pa-M-QU features a three-factor structure: catastrophizing, pain sensitivity, and coping with pain. Conclusions: The Pa-M-QU offers a rapid, non-invasive assessment that captures the multidimensional nature of pain. It is a starting point to develop tools for both clinical and research settings, aiding in evaluating pain in healthy individuals and predicting acute and chronic pain disorders. Future research should focus on refining the Pa-M-QU for broader clinical applications and exploring its potential to complement or replace traditional pain assessments, thereby advancing pain management and research.