Assessment and manifestation of central sensitisation across different chronic pain conditions

Towards a better definition of nociplastic pain conditions: a psychological grounded study on fibromyalgia, chronic headache and vulvodynia

Background: This study investigates the psychological underpinnings of chronic pain conditions, specifically fibromyalgia, chronic headache, vulvodynia, and mixed condition (consisting of fibromyalgia in comorbidity with chronic headache and/or vulvodynia), with a focus on nociplastic pain mechanisms.Objective: The aim of the study is to better understand the psychological functioning of women with different chronic pain conditions to identify and discuss similarities and differences. In particular, we aim to explore any significant differences in the domain of traumatic experiences, in global defensive functioning, and in the domain of alexithymia among the evaluated groups. Further, the 4 groups with chronic pain will be compared with a healthy control group.Methods: A sample of 1006 Italian women diagnosed with chronic pain participated in the study, categorized into four clinical groups and a healthy control group. Measures were assessed using self-report measures, in particular: Traumatic Experiences Checklist, Defense Mechanism Rating Scales, and Toronto Alexithymia Scale.Results: There are significant differences among groups, with mixed conditions exhibiting the highest levels of traumatic experiences, particularly emotional neglect and physical threats. Fibromyalgia and mixed condition groups displayed greater reliance on neurotic defense mechanisms. Additionally, fibromyalgia and mixed condition participants exhibited higher levels of alexithymia, indicating difficulties in emotional processing.Conclusions: These findings underscore the complex interplay between psychological factors and nociplastic pain conditions, emphasizing the importance of personalized psychological interventions in managing nociplastic pain. The study highlights the need for multidisciplinary approaches to nociplastic pain treatment, considering the diverse psychological profiles of affected individuals.

Reference Values of Joint-Specific Pressure Pain Thresholds in Healthy Male Individuals: A Retrospective Study

BACKGROUND

Pressure pain thresholds (PPT) are a component of Quantitative Sensory Testing and are used to assess mechanical pain sensitivity. Joint-specific PPT measurements are relevant because many joint disorders involve altered pain processing at and around joints. This study aims to establish such reference values that might contribute to evaluate deviations in pain sensitivity in specific patient populations.

METHODS

This study retrospectively analysed PPT data from 407 healthy male individuals. Pressure was applied in a standardised manner using an algometer at eight anatomical landmarks: bilaterally at the elbow, knee and ankle joints, as well as the sternum and forehead. Percentile-based, landmark-discriminative normative data were calculated for PPT in general and segmented for age, BMI and mean subjective pain over 4 weeks.

RESULTS

Median (IQR) PPT values (N/cm2) for anatomical landmarks are as follows: ankle = 47.2 (35.9, 63.8), knee = 65.9 (48.6, 89.1), elbow = 58.0 (40.5, 81.1), sternum = 39.8 (30.2, 53.3) and forehead = 35.5 (26.8, 45.0). Between-group analyses revealed no significant effect of BMI on PPT at any landmark assessed, no significant effect of age, except for the elbow joint (p = 0.035) and no effect of the presence of pain, except for the ankle (p = 0.020) and elbow joint (p = 0.010).

CONCLUSION

This study provides normative joint-specific PPT values in healthy male individuals, offering reference values for both clinical and research applications. These values can assist in interpreting PPT measured in clinical settings and in identifying abnormal pain sensitivity.

SIGNIFICANCE STATEMENT

Pressure pain thresholds are an important measure in Quantitative Sensory Testing, yet comprehensive normative data for joint-specific PPT in healthy individuals have been lacking. This study establishes reference values across multiple anatomical landmarks, providing a critical benchmark for evaluating pain sensitivity deviations in musculoskeletal disorders. These findings enhance the interpretation of PPT measurements, supporting improved pain assessment and diagnostic accuracy.

Microalgae and exercise: from molecular mechanisms and brain health to clinical perspectives in the context of 3P medicine

Microalgae are emerging as innovative bioresources with diverse therapeutic applications, particularly in cardiovascular health, neuroprotection, anti-inflammatory, and antioxidant responses. These bioactive compounds effectively reduce inflammatory mediators, mitigate oxidative stress, and support mitochondrial health-critical factors in exercise performance, recovery, and chronic disease management. Notably, microalgae such as Spirulina and Chlorella exhibit promising biological activities in preclinical and limited clinical studies, including anti-inflammatory and neuroprotective effects. However, large-scale, randomized controlled trials (RCTs) remain scarce, limiting their clinical translation. Although preliminary evidence suggests potential benefits for sports performance, oxidative stress reduction, and cognitive function, most studies are small-scale, preclinical, or observational. Large, well-powered RCTs are needed to confirm their efficacy and safety. Within the framework of Predictive, Preventive, and Personalized Medicine (PPPM/3PM), this review explores microalgae's potential in predictive diagnostics, targeted prevention, and individualized supplementation strategies. Despite promising findings, clinical application requires a cautious approach due to insufficient high-quality trials supporting microalgae-based interventions in medical practice. Future research should prioritize RCTs, pharmacokinetic studies, and long-term safety assessments to establish evidence-based guidelines for their use in health and disease management.

Trajectories of cold but not mechanical sensitivity correspond with disability trajectories after whiplash injury

ABSTRACT

Developmental trajectories for neck disability after whiplash injury have been identified. Their relationship to cold and mechanical sensitivity trajectories is not known. We aimed to (1) identify recovery trajectories of cold and mechanical sensitivity, (2) explore their codevelopment with disability trajectories, (3) identify predictors of sensitivity trajectories, and (4) explore codevelopment of cold and mechanical sensitivity trajectories. Participants (n = 233) were assessed at <1, 3, 6, and 12 months after whiplash injury. Outcomes were cold pain detection threshold (CPT at neck), pressure pain detection thresholds (PPT, neck C5, and tibialis anterior), and the Neck Disability Index. We used group-based trajectory models to identify postinjury recovery trajectories and multinominal logistic regression to explore associations between baseline characteristics and trajectory membership. We identified the following trajectory groups: CPT (low [50.0%], moderate [29.7%], and high [20.4%] sensitivity); PPT C5 (low [10.8%] and high [89.2%] sensitivity); and PPT tibialis anterior (low [23.9%], moderate [39.0%], and high [37.1%] sensitivity); all were stable over the 12 months. There was good correspondence between disability and cold sensitivity trajectory groups but not for mechanical sensitivity; cold and mechanical sensitivity trajectories were not well associated. Higher baseline pain predicted membership of the high cold sensitivity trajectory (RR 1.27, 95% CI 1.01-1.59) and hyperarousal symptoms predicted membership of the moderate cold sensitivity trajectory (RR 1.17, 95% CI 1.01-1.36). We found no associations between baseline characteristics and mechanical sensitivity. There is an interplay between cold allodynia, pain, and hyperarousal symptoms in development of ongoing disability after whiplash injury. Different mechanisms likely underlie cold and mechanical sensitivity.

Disrupted spatial but not temporal aspects of nociceptive processing determine painful polyneuropathies

ABSTRACT

Polyneuropathy remains a diagnostic and clinical challenge, with limited understanding of the mechanisms underlying painful and nonpainful phenotypes. While previous studies have examined various characteristics of these patients, the temporal and spatial dynamics of endogenous pain modulation remains not fully elucidated. In this study, offset analgesia (OA) and spatial summation of pain (SSp) were used as measures of pain modulation in individuals with distal symmetric polyneuropathy, stratified by the presence (n = 30) or absence of pain (n = 30), and compared with healthy controls (n = 30). All participants underwent quantitative sensory testing and assessments of OA and SSp using a thermal stimulator applied to the dorsum of the foot. Patients with painful polyneuropathy exhibited enhanced SSp compared with the pain-free polyneuropathy group and healthy controls (P < 0.05), and impaired OA compared with healthy controls (P < 0.05). The pain-free neuropathy group showed less efficient OA and a slightly enhanced SSp, but this finding did not reach significance. The data suggest that changes in spatial summation were primarily driven by heightened pain responses to nociceptive input from smaller areas, rather than larger ones. Notably, spatial summation and the effects of OA were found to be correlated, irrespective of pain diagnosis. These findings underscore specific impairments in endogenous pain modulation in individuals with painful neuropathy, thus advancing our understanding of its pathophysiological mechanisms. They further highlight the differential roles of spatial and temporal dynamics in pain modulation across various neuropathic populations, offering promising avenues for improved diagnostics and prognostics related to polyneuropathy-associated pain.

Redefining Clinical Trials on Regenerative Therapies to Target Responsiveness in Temporomandibular Joint Osteoarthritis Treatment

BACKGROUND

Temporomandibular joint osteoarthritis (TMJ-OA) presents a significant clinical challenge, marked by limited therapeutic options and variable patient responses. While regenerative therapies show promising results, conventional clinical trial methodologies often fail to demonstrate a significant clinical difference, largely due to response variabilities, which is critical in complex conditions like TMJ-OA. As such, methodologies traditionally used in clinical trials for regenerative therapies targeting TMJ-OA may need to be restructured to better identify and accommodate the distinctive profiles of responders and non-responders.

OBJECTIVE

This paper proposes a revised clinical trial framework that focuses on differentiating responders from non-responders within treatment groups, rather than relying solely on traditional control groups.

METHODS

Analysing non-responders provides valuable insights for therapeutic individualisation and optimises patient selection, as understanding predictive factors can lead to improved outcomes. We present recommendations that integrate imaging diagnostics, chronic pain characteristics, and psychosocial assessments, offering a novel approach to enhance efficacy of TMJ-OA treatment.

CONCLUSION

This work advocates for a re-evaluation of standard clinical trial designs to support more personalised and effective strategies for the management of TMJ-OA.

The periaqueductal gray in chronic low back pain: dysregulated neurotransmitters and function

ABSTRACT

Mechanisms underlying chronic pain are insufficiently understood, hampering effective treatment approaches. Preclinical evidence suggests a potential contribution of decreased excitatory (glutamatergic) and increased inhibitory (γ-aminobutyric acid [GABA]ergic) neurotransmission in the periaqueductal gray (PAG), a key descending pain modulatory brainstem area. This magnetic resonance spectroscopy (MRS) study investigated (1) whether a lower excitatory/inhibitory balance is also observed in the PAG of patients with nonspecific chronic low back pain (CLBP) and (2) whether the excitatory/inhibitory balance relates to psychophysical measures of descending pain modulation and pain sensitivity. Magnetic resonance spectroscopy was acquired on a 3T MR system in 41 patients with CLBP and 29 age- and sex-matched controls. Descending pain modulation and pain sensitivity were evaluated using conditioned pain modulation and pressure pain stimuli, respectively, which were both assessed at the lower back as the most painful area and the nondominant hand as a pain-free, remote area. Patients with CLBP presented with a lower glutamate + glutamine (Glx)/GABA ratio compared with controls (P = 0.002), driven by both decreased Glx (P = 0.012) and increased GABA (P = 0.038). Controls with lower Glx/GABA were more sensitive to pressure pain in both areas, but this association was missing in the patients (lower back: P = 0.004; hand: P = 0.002). Patients with more severe clinical pain showed impaired descending pain modulation at the hand (P = 0.003). In line with preclinical evidence, these findings support a dysregulated PAG in patients with CLBP that might be associated with dysfunctional descending pain inhibition.

Effect of depressive symptoms on treatment response in patients with axSpA: data from the RABBIT-SpA register

OBJECTIVES

This analysis aimed to evaluate the effect of depressive symptoms on treatment outcomes in patients with axial spondyloarthritis (axSpA), focusing on low disease activity (LDA) and inactive disease (ID) at 3 and 6 months after the start of a new systemic therapy.

METHODS

This analysis used data from the longitudinal, observational RABBIT-SpA register. Depressive symptoms were assessed using the WHO-5 Well-Being Index, with scores below 29 indicating moderate-to-severe symptoms. The treatment outcomes LDA and ID, based on the Axial Spondyloarthritis Disease Activity Score with C-reactive protein, were evaluated after 3 and 6 months. Logistic regression models adjusted for confounding variables, selected via a directed acyclic graph, were used to assess the relationship between baseline depressive symptoms and treatment outcomes. Multiple imputation was used to handle missing data.

RESULTS

A total of 1755 patients with axSpA were included in the analysis. Moderate-to-severe depressive symptoms were present in 29% of patients at baseline. Fewer patients with moderate-to-severe depressive symptoms reached LDA or ID at 3 months and 6 months compared with those with no or mild symptoms. Logistic regression analysis showed that depressive symptoms were associated with lower odds of reaching LDA or ID at both time points.

CONCLUSION

Depressive symptoms have a significant and independent negative effect on treatment response in patients with axSpA, particularly in achieving LDA and ID. These findings highlight the importance of routine mental health screening and treatment of depressive symptoms in axSpA management to optimise disease outcomes.

Neurophysiological Examination for the Diagnosis of Orofacial Pain and Temporomandibular Disorders: A Literature Review

Temporomandibular disorders (TMD) are a cluster of musculoskeletal conditions that involve the overall structures of jaw movements, including the temporomandibular joint, the masticatory muscles, and the surrounding structures. The etiology of TMD-related pain may be either central or peripheral, and differential diagnoses with other orofacial conditions are commonly required. Central pain etiology is associated with altered brain function linked to sensitization of pain-producing centers, whereas peripheral etiology of TMD is considered multifactorial, with some predisposing factors. Differentiating between neurological conditions and TMD requires a comprehensive clinical evaluation, as overlapping symptoms can complicate the diagnostic process. The aim of this review was to summarize the current literature about the role of neurophysiological examination in the management of orofacial pain and temporomandibular disorders to provide clear data that could be useful for clinical practice and for future clinical studies in this field.

Somatosensory profiling to differentiate distinct painful diseases of the pancreas-a quantitative sensory testing case-control study

ABSTRACT

Mechanisms of pancreatic pain are insufficiently understood, and quantitative sensory testing (QST) may help to identify the underlying mechanisms. Accordingly, this study assessed comprehensive somatosensory profiles encompassing nociceptive and nonnociceptive parameters in 70 patients with distinct pancreatic diseases, namely acute (n = 23), chronic (n = 20), or autoimmune pancreatitis (n = 10) and pancreatic cancer (n = 17) and compared it with 30 healthy control subjects by standardized QST (protocol of the German research network on neuropathic pain). Patients with pancreatic diseases presented significant somatosensory deficits in all thermal and tactile detection and pain thresholds in the pancreatic viscerotome (Th10), when compared with a remote control area (dermatome C5) or reference data of matched healthy controls (P < 0.05-P < 0.0001). Unaltered vibration detection emphasizes the strictly regional character of losses. Loss of sensitivity paralleled the occurrence of paradoxical heat sensation (Th10 vs C5; P < 0.05), an indicator of thermal integration deficit. Punctate hyperalgesia or pain to light touch, the hallmark signs of spinal central sensitization were mostly absent and pain summation remained unchanged (P > 0.05). Stratification of patients revealed that somatosensory deficits were significantly more pronounced in acute compared with chronic pancreatitis (eg, cold and warm detection thresholds: -2.19 ± 1.42 vs -1.10 ± 1.23 and -1.30 ± 1.68 vs -0.11 ± 1.80 z-values; P < 0.05 each). Notably, blunt pressure hyperalgesia, the only somatosensory parameter exhibiting significant gain compared with the patients' remote C5 segment, was a frequent finding only in acute, but not in chronic pancreatitis. The somatosensory phenotype of patients with distinct pancreatic disorders was characterized by a wide array of sensory losses being most severe in acute pancreatitis.

Endogenous pain modulation is not different in basketball or volleyball athletes with patellar tendinopathy compared to asymptomatic athletic controls

BACKGROUND

Patellar tendinopathy is highly prevalent in basketball and volleyball athletes. Despite pain being the main symptom reported, underlying mechanisms are unclear.

OBJECTIVES

Our primary aim was to compare endogenous pain inhibition using a conditioned pain modulation protocol in basketball and volleyball athletes with patellar tendinopathy to asymptomatic athletic controls. Our secondary aim was to compare endogenous pain facilitation using a temporal summation protocol.

DESIGN

Cross-sectional case-control.

METHODS

Twenty-six athletes and 19 asymptomatic controls participated. We calculated the difference in PPT at the patellar tendon over the most painful site (pain site), the ipsilateral tibialis anterior (regional site), and the contralateral elbow lateral epicondyle (remote site), before and after immersion of the hand (ipsilateral to pain site) in painful cold-water. PPT change was used to quantify endogenous pain inhibition. Participants rated pain on a numerical rating scale (NRS; 0 = no pain to 10 = worst pain imaginable) at five, 20, 60 and 120 s during the cold-water immersion task. Change in NRS from five to 20 s quantified temporal summation.

RESULTS

Median symptom duration in our patellar tendinopathy group was 39 (IQR 22.5-55.5) months, and 85% experienced symptoms bilaterally. We did not observe alterations in endogenous pain inhibition at any site, or in temporal summation, in athletes with patellar tendinopathy compared to controls (p > 0.05).

CONCLUSION

Our findings indicate that altered central nervous system function is not a predominate feature contributing to pain in jumping athletes with patellar tendinopathy. Accordingly, clinicians should view pain as being of a local tissue source if targeting this symptom.

Pain mechanistic networks: the development using supervised multivariate data analysis and implications for chronic pain

ABSTRACT

Chronic postoperative pain is present in approximately 20% of patients undergoing total knee arthroplasty. Studies indicate that pain mechanisms are associated with development and maintenance of chronic postoperative pain. The current study assessed pain sensitivity, inflammation, microRNAs, and psychological factors and combined these in a network to describe chronic postoperative pain. This study involved 75 patients with and without chronic postoperative pain after total knee arthroplasty. Clinical pain intensity, Oxford Knee Score, and pain catastrophizing were assessed as clinical parameters. Quantitative sensory testing was assessed to evaluate pain sensitivity and microRNAs, and inflammatory markers were likewise analyzed. Supervised multivariate data analysis with "Data Integration Analysis for Biomarker Discovery" using Latent cOmponents (DIABLO) was used to describe the chronic postoperative pain intensity. Two DIABLO models were constructed by dividing the patients into 3 groups or 2 defined by clinical pain intensities. Data Integration Analysis for Biomarker discovery using Latent cOmponents model explained chronic postoperative pain and identified factors involved in pain mechanistic networks among assessments included in the analysis. Developing models of 3 or 2 patient groups using the assessments and the networks could explain 81% and 69% of the variability in clinical postoperative pain intensity. The reduction of the number of parameters stabilized the models and reduced the explanatory value to 69% and 51%. This is the first study to use the DIABLO model for chronic postoperative pain and to demonstrate how different pain mechanisms form a pain mechanistic network. The complex model explained 81% of the variability of clinical pain intensity, whereas the less complex model explained 51% of the variability of clinical pain intensity.

Quantifying Impairments in the Subacute Phase of Whiplash Associated Disorders-A Cross-Sectional Study

Whiplash-Associated Disorders (WADs) often result from traffic accidents, leading to persistent symptoms, including neck pain, disability, dizziness, and central sensitization (CS). A key concern is cervical range of motion (cROM) impairment and sensorimotor dysfunction, which contribute to prolonged disability. This study assessed functional performance in individuals with subacute (>1, <3 months) WADs (n = 122) compared to healthy controls (n = 45). Clinical measures included cROM, movement control (Butterfly test), and position sense (Head-Neck Relocation Test, HNRT). Patient-reported outcomes included neck disability, pain intensity, central sensitization, and dizziness. Mixed and linear models evaluated group differences and the influence of demographic and symptom-related factors. WAD patients had significantly reduced cROM and impaired movement control (p < 0.001). Neck disability (p < 0.001) and pain intensity (p = 0.015) affected cROM within the WAD group. Interaction effects revealed greater amplitude accuracy (AA) impairments at greater difficulty levels (p = 0.043), while time on target (TOT) differences decreased (p < 0.001). Dizziness was associated with increased undershoot (p < 0.001), while pain negatively impacted both AA (p = 0.003) and TOT (p = 0.037). Position sense did not differentiate WAD patients from controls. Findings suggest task-dependent sensorimotor deficits, highlighting the need for multimodal assessment. Early CS screening may optimize rehabilitation and prevent chronic disability.

Conditioned Pain Modulation in Patients with Hemophilic Arthropathy: A Cross-Sectional Cohort Study

Background/Objectives: Hemophilic arthropathy causes functional impairment, disability, and chronic pain. Conditioned pain modulation describes the effect of endogenous pathways that potentiate or diminish the effects of noxious afferent stimuli. The objective was to identify conditioned pain modulation in patients with bilateral hemophilic ankle and knee arthropathy, and the best predictive model thereof. Methods: Cross-sectional cohort study. Forty-nine adult patients with hemophilic arthropathy were recruited. The dependent variable was the Conditioned Pain Modulation Index (CPMI). Age was the predictor variable. Secondary variables, estimated as modifying or confounding variables, were kinesiophobia (Tampa Scale for Kinesiophobia), catastrophizing (Pain Catastrophizing Scale), anxiety (State-Trait Anxiety Inventory), and clinical, anthropometric, and sociodemographic variables. Results: Conditioned pain modulation in patients with hemophilic arthropathy presents values close to zero (mean = 0.004: 95%CI: -0.05; 0.06). Anxiety, pain intensity, and pressure pain threshold explained the variability in the conditioned modulation of ankle pain (R2adj = 0.24). Variables explaining 23.05% of variability of conditioned modulation of knee pain were age, inhibitor development, anxiety, and pressure pain threshold (R2adj = 0.23). Conclusions: Patients with hemophilia presented a modulation close to zero, representing a balance between the ability to inhibit and facilitate painful stimuli. The predictive model of conditioned modulation of ankle pain includes anxiety, and pain intensity and threshold. Age, inhibitory development, anxiety, and pain threshold predict knee pain modulation.

Implications of nociceptor receptors and immune modulation: emerging therapeutic targets for autoimmune diseases

Chronic painful autoimmune disorders such as multiple sclerosis (MS), inflammatory bowel disease (IBD), and rheumatoid arthritis (RA) induce significant discomfort. They are defined by persistent inflammation and immune-mediated tissue injury. The activation and sensitisation of nociceptors, mutated in various disorders, are fundamental components contributing to the pain experienced in these conditions. Recent discoveries indicate that immunological mediators and nociceptive receptors interact functionally within peripheral and central sensitisation pathways, amplifying chronic pain. This research examines the involvement of nociceptors in rheumatoid arthritis, multiple sclerosis, and inflammatory bowel disease. It explores how immune cells and pro-inflammatory cytokines induce, sensitise and regulate various nociceptive receptors (P2X, TRPA1 and TRPV1). Finally, we address possible future directions with respect to the treatment of long-lasting effects on immunity, and what new drug targets could be pursued as well, in order to counteract such either neuro-immune interactions in conditions involving the immunological system. By studying nociceptive mechanisms across autoimmune illnesses, we want to identify shared pathways and activation of nociceptors specific to individual diseases. This will shed insight on potential therapies for managing pain associated with autoimmune diseases.

Pathophysiology, Assessment, and Management of Pain Associated with Chronic Pancreatitis

Chronic pancreatitis (CP) is a fibroinflammatory disease, with pain as its most prominent symptom. This article provides a comprehensive review of the pathophysiology, assessment methodologies, and management strategies pertaining to pain in CP. Pathophysiological mechanisms include inflammatory and neuropathic components, including peripheral and central sensitization. Pain assessment can include unidimensional and multidimensional pain assessment scales, neurophysiological assessments, and advanced imaging techniques. Management strategies include a spectrum from lifestyle modifications, pharmacologic interventions, and interventional procedures to neuromodulatory techniques and other experimental treatments.

The Interplay Between Chronic Pelvic Pain and Pelvic Organ Prolapse

INTRODUCTION AND HYPOTHESIS

Chronic pelvic pain (CPP) affects approximately 26% of the world's female population and has various proposed etiologies. This manuscript aims to review concepts related to pelvic organ prolapse (POP) and CPP, encompassing its etiology, risk factors, clinical findings, and pain management.

METHODS

A narrative review was performed using MeSH terms and text words on PubMed, and the Cochrane Database of Systematic Reviews through May 2024. A total of 33 references were used to address the questions posed in this review.

RESULTS

Specific risk factors for CPP associated with POP include pain antedating POP onset, POP surgery duration, and extent of soft tissue trauma. Studies indicate that uterosacral ligament repair performed during surgical interventions for POP correction has alleviated CPP symptoms whether performed vaginally or laparoscopically. Women with preexisting CPP or central sensitization syndrome (CSS) undergoing pelvic reconstructive surgery for POP may experience less favorable postoperative outcomes compared to those without preexisting pain conditions. These outcomes include lower patient satisfaction, less resolution of discomfort, and poorer improvement in urinary symptoms.

CONCLUSIONS

On the basis of current evidence, surgeries for POP correction, especially those involving the uterosacral ligament, have shown a positive impact on reducing pelvic pain. However, untreated CPP is associated with lower satisfaction and less improvement in outcomes after POP surgery regarding pelvic symptoms and quality of life. Screening for and treating CPP conditions prior to POP surgery should be prioritized. Pain management of CPP should be addressed preoperatively, perioperatively, and postoperatively.

Assessing signs of central sensitization: A critical review of physiological measures in experimentally induced secondary hyperalgesia

BACKGROUND AND OBJECTIVES

Central sensitization (CS) is believed to play a role in many chronic pain conditions. Direct non-invasive recording from single nociceptive neurons is not feasible in humans, complicating CS establishment. This review discusses how secondary hyperalgesia (SHA), considered a manifestation of CS, affects physiological measures in healthy individuals and if these measures could indicate CS. It addresses controversies about heat sensitivity changes, the role of tactile afferents in mechanical hypersensitivity and detecting SHA through electrical stimuli. Additionally, it reviews the potential of neurophysiological measures to indicate CS presence.

DATABASES AND DATA TREATMENT

Four databases, PubMed, ScienceDirect, Scopus and Cochrane Library, were searched using terms linked to 'hyperalgesia'. The search was limited to research articles in English conducted in humans until 2023.

RESULTS

Evidence for heat hyperalgesia in the SHA area is sparse and seems to depend on the experimental method used. Minimal or no involvement of tactile afferents in SHA was found. At the spinal level, the threshold of the nociceptive withdrawal reflex (RIII) is consistently reduced during experimentally induced SHA. The RIII area and the spinal somatosensory potential (N13-SEP) amplitude are modulated only with long-lasting nociceptive input. At the brain level, pinprick-evoked potentials within the SHA area are increased.

CONCLUSIONS

Mechanical pinprick hyperalgesia is the most reliable behavioural readout for SHA, while the RIII threshold is the most sensitive neurophysiological readout. Due to scarce data on reliability, sensitivity and specificity, none of the revised neurophysiological methods is currently suitable for CS identification at the individual level.

SIGNIFICANCE

Gathering evidence for CS in humans is a crucial research focus, especially with the increasing interest in concepts such as 'central sensitization-like pain' or 'nociplastic pain'. This review clarifies which readouts, among the different behavioural and neurophysiological proxies tested in experimental settings, can be used to infer the presence of CS in humans.

Psychological, disability, and somatosensory characteristics across different risk levels in individuals with low back pain: A cross-sectional study

BACKGROUND

Current low back pain (LBP) treatment might be improved by tailoring treatments to subgroup characteristics. The Start Back screening Tool (SBT) and Central Sensitization Inventory (CSI) classify people with LBP into subgroups. It is currently unknown whether linear trends exist regarding somatosensory changes, psychological characteristics, and physical disability across severity levels of the SBT and CSI in patients with LBP.

OBJECTIVE

To investigate whether linear trends in psychological variables (kinesiophobia, pain catastrophizing), disability, and somatosensory characteristics exist in a sample of people with acute and chronic LBP in primary care across severity levels based on the SBT and CSI.

METHODS

Participants with LBP were recruited in primary care. Demographic, psychological, and disability data were obtained. A comprehensive Quantitative Sensory Testing (QST) protocol was followed. Linear contrast analysis was conducted.

RESULTS

Kinesiophobia and pain catastrophizing show significant positive linear trends across the subgroups based on the SBT (p < 0.001) and CSI (p < 0.001 to p = 0.01). Heat pain threshold at the lower leg (p = 0.005) and pressure pain threshold at the lumbar region and lower leg (p = 0.02 and p = 0.04, respectively) show significant negative linear trends within the SBT. Negative linear trends in sensory changes exist within CSI for all pressure pain thresholds and a positive linear trend was seen in δ conditioned pain modulation at the thumb (p = 0.03).

CONCLUSION

Kinesiophobia, pain catastrophizing, disability, and pain intensity are positively related with the severity levels based on the SBT and CSI in our participants. Results of somatosensory changes were sometimes related to the severity levels.

Pain profiles and variability in temporal summation of pain and conditioned pain modulation in pain-free individuals and patients with low back pain, osteoarthritis, and fibromyalgia

BACKGROUND

Pain profiles (e.g. pro- and anti-nociceptive) can be developed using quantitative sensory testing (QST) but substantial variability exists. This study describes the variability in temporal summation of pain (TSP) and conditioned pain modulation (CPM) in chronic musculoskeletal pain patients, proposes cut-off values, and explores the association with clinical pain intensity.

METHODS

This is a secondary analysis in which TSP and CPM were assessed using cuff algometry in pain-free subjects (n = 69), and patients with chronic low back pain (cLBP, n = 267), osteoarthritis (n = 134), and fibromyalgia (n = 101). Using TSP and CPM from the pain-free subjects as a reference, four distinct pain profiles TSP (low/high) and CPM (low/high) were created, and differences in clinical pain between pain profiles were explored.

RESULTS

Individual data revealed large inter-person variability. High TSP and low CPM were found in fibromyalgia (p < 0.01) and osteoarthritis (p < 0.01) but not cLBP when compared to pain-free subjects. The proportion of patients classified into the distinct pain profiles was significantly different (p < 0.001) with the largest proportion in the high TSP and low CPM group in fibromyalgia (52.5%) and osteoarthritis (41.4%). Clinical pain was not significantly different comparing the pain profiles, and no significant correlations were observed between clinical pain and TSP or CPM.

CONCLUSION

These results demonstrated substantial inter-person variability in TSP and CPM in patients with different chronic pain conditions and pain-free subjects. The proportion of patients with a pro-nociceptive profile appears larger in fibromyalgia and osteoarthritis, but we found no association to clinical pain.

SIGNIFICANT STATEMENT

This analysis shows that there is variability when assessing TSP and CPM in both pain-free subjects and patients with chronic pain. A cut-off for determining when a person is pain-sensitive is proposed, and data based on this cut-off approach suggest that significantly more patients with osteoarthritis and fibromyalgia are pain-sensitive (i.e. higher TSP and lower CPM) compared to pain-free subjects. This analysis does not find an association between pain sensitivity and clinical pain.

Association between central sensitization and multisite pain in the general population: A cross-sectional analysis of The Wakayama Health Promotion Study

BACKGROUND

Central sensitization (CS), which is characterized by amplified nociceptive processing within the central nervous system, is a key mechanism underlying chronic pain disorders. Chronic pain is a significant global health issue; however, the relationship between CS and pain distribution in the general population remains unclear. This study aimed to investigate the association between CS and the number of locations of body pain in a representative sample of the general population.

METHODS

This cross-sectional study included 739 participants (340 men, 399 women) from the Wakayama Health Promotion Study. CS was assessed using the Japanese version of the Central Sensitization Inventory (CSI-J), with scores of ≥30 indicating CS. Participants reported pain at 13 locations. Statistical analyses, including chi-square tests, Student's t-tests, and multiple regression analyses, were performed to determine the associations between Central Sensitization Inventory (CSI) scores and pain locations.

RESULTS

Among the participants, 9.5 % were diagnosed with CS. Females had significantly higher CSI scores than males. Lower back pain (20.6 %) and shoulder pain (15.0 %) were most common in men, whereas shoulder pain (20.6 %), knee pain (20.1 %), and lower back pain (19.5 %) were most common in women. Multivariate analysis revealed that sex, headache, neck pain, shoulder pain, arm pain, lower back pain, hip pain, thigh pain, and knee pain were significantly associated with CSI scores. Participants with ≥3 locations were 14.4 times more likely to have CS.

CONCLUSIONS

This study highlights the significant prevalence of CS in the general population, with a higher prevalence in females. Specific locations of pain, particularly those close to the trunk, are strongly associated with CS. These findings underscore the importance of assessing CS in individuals with multisite pain for targeted management and treatment strategies.

Allodynia: A Review Article

PURPOSE OF REVIEW

Allodynia is characterized by a painful response to a non-noxious stimulus. This article reviews the pathophysiology, clinical presentation, differential diagnosis, diagnostic testing, and management approaches for the causes of allodynia.

RECENT FINDINGS

Allodynia remains difficult to evaluate and manage. Despite ongoing research, significant progress is still needed to optimize the management of allodynia. Allodynia is a debilitating condition that can be difficult to treat. Diagnostic modalities and treatment options are limited. Advancements in diagnostic and treatment options are necessary to improve patient care.

Effectiveness of mindfulness-based online therapy or internet-delivered cognitive behavioral therapy compared with treatment as usual among patients with persistent somatic symptoms: Protocol for a randomized controlled trial

BACKGROUND

Persistent somatic symptoms unexplained by a defined medical or psychiatric condition often include a component of central sensitization. Many treatment options are based on cognitive behavioral therapy. Effective widely available therapies are scarce. There are self-management programs and e-therapies that aim at overcoming the central sensitization by modifying interoceptive neural networks in the brain.

OBJECTIVES

This study aims to investigate the effect of a mindfulness-based amygdala and insula retraining (AIR) online program and an internet delivered therapist assisted therapy offered by Helsinki University Hospital (HUS iCBTpss) compared to treatment as usual (TAU) in the treatment of conditions causing persistent somatic symptoms.

METHODS

We will perform a randomized controlled trial aiming at 360 patients. Consenting patients will be randomized to three study arms: online AIR program, HUS iCBTpss (both interventions as add-ons to TAU); and TAU. Functional ability and quality of life surveys will be collected from participants at baseline and at 3, 6, and 12 months after entering the study.

CONCLUSIONS

This study is one of the first to explore non-drug based online interventions developed to overcome the brain's central sensitization and are available and accessible to patients both in primary and secondary care. The results will develop the management of the common, often debilitating persistent somatic symptoms related to many conditions unexplained by a defined somatic or psychiatric illness.

TRIAL REGISTRATION NUMBER

NCT05212467.

Applying Nociplastic Pain Criteria in Chronic Musculoskeletal Conditions: A Vignette Study

Background/Objectives: The International Association for the Study of Pain (IASP) recently introduced clinical criteria and a grading system to identify nociplastic pain, marking a pivotal step toward improving diagnostic accuracy. This study aimed to evaluate the reliability and validity of the IASP criteria using clinical vignettes, assessing their effectiveness in identifying nociplastic pain in clinical settings. Methods: A reliability and diagnostic accuracy study was conducted using 32 clinical vignettes based on the literature and pre-existing clinical data. The vignettes represented patients with and without the characteristics of nociplastic pain and were reviewed independently by two expert physiotherapists. Inter-rater and intra-rater reliability were evaluated with a 1-month interval between assessments. Criterion validity was analyzed by comparing the IASP criteria against the standardized vignettes as the reference standard. Sensitivity, specificity, and predictive values were calculated to assess diagnostic accuracy. Results: The IASP criteria demonstrated moderate-to-perfect intra-rater agreement (κ = 0.71-1.00, p < 0.05) and weak-to-perfect inter-rater agreement (κ = 0.52-1.00, p < 0.05). Criterion validity was moderate (κ = 0.68), with strong specificity (89.0%) and moderate sensitivity (69.0%). Positive and negative predictive values were high at 81.8% and 81.0%, respectively, supporting the criteria's accuracy in identifying and excluding nociplastic pain. Conclusions: The IASP criteria for nociplastic pain exhibited satisfactory reliability and criterion validity in this preliminary study, particularly after initial rater familiarization. Future research should evaluate their application in real-world clinical settings, explore concurrent and prognostic validity, and involve a broader range of raters to enhance generalizability.

Pain is Modulated Differently Between Females With and Without Patellofemoral Pain: Factors Related to Sensitization

CONTEXT

Patellofemoral pain (PFP) has poor long-term recovery outcomes. Central sensitization describes central nervous system changes altering pain modulation, which can complicate recovery (poorer prognosis and worse function). Signs of central sensitization include amplified pain facilitation, pain hypersensitivity, and impaired pain inhibition, which can be measured with temporal summation of pain (TSP), pressure pain thresholds (PPTs), and conditioned pain modulation (CPM), respectively. Sex differences exist for these test responses, but female-only PFP investigations of sensitization are uncommon. Understanding pain modulation in females with PFP could improve treatment protocols.

OBJECTIVE

To determine whether females with PFP exhibit signs of central sensitization (greater TSP, lower PPTs, and reduced CPM) compared with pain-free females.

DESIGN

Cross-sectional study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Thirty-three females ([20 PFP, 13 pain free]; age: PFP 29.2 ± 7 years, pain free 28 ± 7 years; height: PFP 166.7 ± 5.9 cm, pain free 166 ± 9.5 cm; mass: PFP 66.7 ± 9.6 kg, pain free 69.3 ± 7.5 kg).

MAIN OUTCOME MEASURE(S)

Temporal summation of pain was assessed with 10 punctate stimuli applied to the knee and calculated by the difference in pain intensity between beginning and end responses. Pressure pain thresholds were tested at 4 sites (3 for local hypersensitivity [knee] and 1 for widespread hypersensitivity [hand]). Conditioned pain modulation was conducted by comparing PPTs during 2 conditions (baseline and ice immersion). Conditioned pain modulation response was defined as the percent difference between conditions. Between-groups differences in TSP response were analyzed with a Welch test. Separate Welch tests analyzed group comparisons of PPTs and CPM responses at 4 sites.

RESULTS

Females with PFP exhibited greater TSP response (P = .019) and lower CPM response at patella center (P = .010) and hand sites (P = .007) than pain-free females. Pressure pain thresholds group differences were not observed at any site (P > .0125).

CONCLUSIONS

Females with PFP modulate pain differently than pain-free females. Clinicians should recognize signs of central sensitization and their potential effect on treatment options.

Blood proteomics and multimodal risk profiling of human volunteers after incision injury: A translational study for advancing personalized pain management after surgery

A significant number of patients develop chronic pain after surgery, but prediction of those who are at risk is currently not possible. Thus, prognostic prediction models that include bio-psycho-social and physiological factors in line with the complex nature of chronic pain would be urgently required. Here, we performed a translational study in male volunteers before and after an experimental incision injury. We determined multi-modal features ranging from pain characteristics and psychological questionnaires to blood plasma proteomics. Outcome measures included pain intensity ratings and the extent of the area of hyperalgesia to mechanical stimuli surrounding the incision, as a proxy of central sensitization. A multi-step logistic regression analysis was performed to predict outcome measures based on feature combinations using data-driven cross-validation and prognostic model development. Phenotype-based stratification resulted in the identification of low and high responders for both outcome measures. Regression analysis revealed prognostic proteomic, specific psychophysical, and psychological features. A combinatorial set of distinct features enabled us to predict outcome measures with increased accuracy compared to using single features. Remarkably, in high responders, protein network analysis suggested a protein signature characteristic of low-grade inflammation. Alongside, in silico drug repurposing highlighted potential treatment options employing antidiabetic and anti-inflammatory drugs. Taken together, we present here an integrated pipeline that harnesses bio-psycho-physiological data for prognostic prediction in a translational approach. This pipeline opens new avenues for clinical application with the goal of stratifying patients and identifying potential new targets, as well as mechanistic correlates, for postsurgical pain.

Exploring the Potential of Psychedelics in the Treatment of Headache Disorders: Clinical Considerations and Exploratory Insights

PURPOSE OF REVIEW

Exploration of the potential of serotonergic psychedelic drugs, such as psilocybin and LSD, as potential treatments for headache disorders. This review addresses the need for well-informed physician guidelines and discusses mechanisms, safety, and efficacy of these treatments. Further research, including the consideration of combination with psychotherapy, is needed.

RECENT FINDINGS

Psychedelics demonstrate promising outcomes as treatments for headache disorders. Recent findings indicated that some patients who underwent brief periods of treatment with psychedelics experienced a reduction in headache attack frequency, severity, or duration. When prescription medications are ineffective at treating headache disorders, or are habit-forming, patients often turn to alternative options. There is anecdotal evidence that psychedelic drugs like LSD and psilocybin can effectively treat and prevent pain in patients with headache disorders, such as migraine or cluster headache. It is vital that physicians treating patients who self-treat with psychedelics be well-informed about the mechanisms and their effects to best advise their patients and coordinate their care well. This is a review assessing the literature on the mechanisms, safety, and efficacy of psychedelic drugs as a headache management intervention. We believe there is evidence that may support further investigation into the clinical use of psychedelic medications to treat cluster headache and migraine, including the consideration of use in conjunction with other interventions like cognitive behavioral therapy or acceptance and commitment training.

Subgroup Characteristics of Middle-Aged and Older Women with Chronic Low Back Pain by Multiple Factors: A Hierarchical Cluster Analysis

BACKGROUND/OBJECTIVES

Chronic low back pain (CLBP) after middle age is a complex multifactorial condition, and subgrouping is recommended to determine effective treatment strategies. Multidimensional data help create new groupings to increase the effectiveness of interventions in middle-aged and older adults with CLBP. This study aimed to investigate the relationship between the factors associated with CLBP after middle age and to create and characterize a new subgroup based on these factors.

METHODS

A cross-sectional observational study was conducted and included 46 women aged ≥40 years with CLBP who participated in health events. Trunk muscle mass, lumbar movement control ability, autonomic balance, lumbar tenderness threshold, lumbar proprioception, and severity of central sensitization were assessed.

RESULTS

Partial correlation analysis revealed a significant negative correlation between lumbar movement control ability and autonomic balance. A significant positive correlation was observed between trunk muscle mass and the lumbar tenderness threshold. Hierarchical clustering analysis identified three subgroups. The cluster 1 participants had low trunk muscle mass, low tenderness threshold, and low severity of central sensitization. The cluster 2 participants had low trunk muscle mass and tenderness threshold and high severity of central sensitization. The cluster 3 participants had high trunk muscle mass and tenderness threshold and were sympathetically predominant. Trunk muscle mass, pressure pain threshold, severity of central sensitization, and autonomic balance were significantly different between the clusters.

CONCLUSIONS

Three characteristic subgroups were identified. The results contribute to treatment and prevention strategies for middle-aged and older adults with CLBP based on the characteristics of the subgroups rather than a uniform approach.

ADHD (Attention-Deficit Hyperactivity Disorder) Symptoms Are Associated With Chronic Pain Interference: Results From a Prospective Cohort Study

BACKGROUND

Despite a known relationship between attention-deficit hyperactivity disorder (ADHD) and chronic pain, the association between ADHD symptoms and pain interference has not been prospectively investigated.

METHODS

Young adults were recruited following receipt of a prescription opioid from ambulatory surgery clinics, outpatient clinics and emergency departments as part of a larger study. Participants completed measures of ADHD symptoms, depression, pain catastrophizing, adverse childhood experiences and pain interference at enrolment and 6 months later. Logistic regression was used to examine the relationship between ADHD symptoms and covariates on moderate-to-severe pain interference at 6 months.

RESULTS

Participants were 116 young adults who completed the baseline ADHD symptoms measure; 71 completed the 6-month timepoint. Moderate-to-severe pain interference was present among 89.7% at baseline and 52.3% at 6 months. ADHD symptoms (OR [odds ratio] = 1.42, 95% CI [confidence interval] = 1.05-1.93), depression (OR = 1.08, 95% CI = 1.02-1.14) and pain catastrophizing (OR = 1.06, 95% CI = 1.01-1.12) were significantly associated with odds of moderate-to-severe pain interference at 6 months. In multivariable regression, ADHD symptoms (OR = 1.52, 95% CI = 1.09-2.12) and pain catastrophizing (OR = 1.07, 95% CI = 1.01-1.13) were significant predictors of moderate-to-severe pain interference at 6 months.

CONCLUSIONS

Participants with more ADHD symptoms were at greater risk for chronic pain interference. This is consistent with prior studies examining the role of attention in chronic pain. Individuals with ADHD symptoms may be at greater risk for chronic pain and future research should investigate tailored prevention and treatment approaches.

The Role of Central Sensitization in Autoimmune Connective Tissue Diseases: A Comparative Cross-Sectional Study

OBJECTIVE

To investigate the central sensitization (CS) in patients with autoimmune connective tissue diseases (ACTDs) and its relationship with disease activity, laboratory findings, medical treatments, organ involvements, and comorbidity.

METHODS

One hundred and eleven patients with ACTDs and 40 healthy individuals were included. All patients were divided into three groups in terms of their diseases: Sjögren's syndrome (SS), rheumatoid arthritis (RA), and systemic lupus erythematosus (SLE). The CS was assessed using the central sensitization inventory (CSI-A and CSI-B scores). The disease activity, laboratory findings, medical treatments, organ involvements, and comorbidity of all patients were evaluated.

RESULTS

Overall, 41.4% patients with ACTDs had CS. SS group had the highest CS positivity (n = 21, 58.3%) compared to the RA (n = 14, 36.8%) and SLE (n = 11, 29.7%) groups. The SS group had a significantly higher CSI-A score (p < 0.016) than the RA and SLE group, which had similar scores. CSI-A (p = 0.008, r = -0.63) and CSI-B (p = 0.001, r = -0.76) scores were moderately to high correlated with vitamin D3 levels in SLE group. CSI-B score was moderately correlated with folic acid levels (p = 0.03, r = 0.50) and TSH (p = 0.005, r = 0.55) in SS group. The CSI-A score ≥ 40 subgroup had more female gender, frequency of COPD or asthma, more coexisting fibromyalgia, higher VAS score, more common exocrine gland involvement, and higher corticosteroid dose compared to the CSI score < 40 subgroup.

CONCLUSIONS

CS is commonly seen in patients with ACTDs, especially in SS. CS is associated with vitamin D3, folic acid, and TSH levels in ACTD subgroups and the patients with clinical CS have a specific profile.

Cross-Cultural Adaptation and Validation of the Central Sensitization Inventory Among Chinese Patients with Chronic Non-Specific Low Back Pain

Purpose

This research aims to develop and validate the Chinese version of the Central Sensitization Inventory (CSI-CV) for patients suffering from chronic non-specific low back pain (CNSLBP). The study evaluates both the validity and reliability of the CSI-CV.

Patients and Methods

The cross-cultural adaptation of the scale strictly adhered to the principles of Bombardier and Beaton. Initially, two professors of Chinese-English translation independently translated the original CSI scale into the target language, and then collaborated with an expert in cross-cultural adaptation to merge into a single version. This version was back-translated into English by two professors whose native language is English. Following this, the scale underwent preliminary review by bilingual experts and the research team, and was preliminarily tested, ultimately culminating in the formation of the CSI-CV version. A total of 310 patients with CNSLBP completed the CSI-CV, while 50 of them repeated the survey one week later to test the stability of the scale. The CSI-CV's reliability, validity, and internal consistency were assessed through exploratory factor analysis (EFA), correlation coefficients, and Cronbach's α.

Results

EFA revealed five distinct factors from the 25 CSI-CV items, covering physical symptoms, emotional distress, fatigue and sleep disturbances, headaches and jaw symptoms, and urinary issues, with a total explained variance of 60.24%. The Cronbach's α was 0.910, and the intraclass correlation coefficient (ICC) was 0.924, indicating strong reliability. Moderate correlations were observed between CSI-CV scores and Five-Level EuroQol Five-Dimensional Questionnaire (r = -0.515), the Brief Pain Inventory (r = 0.586) and Oswestry Disability Index (r = 0.416), demonstrating significant associations with these measures.

Conclusion

The CSI-CV exhibits excellent internal consistency, factor structure, and reliability. Its successful cultural adaptation offers valuable insights for improving treatment approaches for patients with CNSLBP.

Can Clinical, Psychophysical or Psychological Variables Help in Discriminating Women with Migraines from a Tertiary Center? A Diagnostic Accuracy Study

Background: Migraine diagnosis is mainly clinically based on symptomatology. The objectives of this study were (1) to determine the ability of pain thresholds to differentiate between women with and without migraines and (2) to determine the ability of clinical, psychological and psychophysical variables to differentiate between women with episodic and chronic migraines. A diagnostic accuracy study was conducted. Methods: Pressure-pain thresholds (PPTs) at one trigeminal (temporalis muscle) and one extra-trigeminal (cervical spine) and two distant-pain free (second metacarpal and tibialis anterior muscle) areas, as well as dynamic pain thresholds (DPTs), were bilaterally assessed in 100 women with migraines, recruited from tertiary hospitals (50% episodic, 50% chronic), and 50 comparable women without headaches. Migraine pain features (headache diary), migraine-associated burden (HDI), anxiety and depressive levels (HADS) and state (STAI-S)-trait (STAI-T) anxiety were also evaluated. The area under the receiver operating characteristic (ROC) curve, with optimal cut-off points, as well as the sensitivity, specificity and positive/negative likelihood ratios (LR) for each variable, were calculated. The women with migraines showed lower PPTs and DPTs than those without migraines. Results: The women with chronic migraines showed lower PPTs in the temporalis muscle than the women with episodic migraines. No clinical, psychological or psychophysical variables exhibited acceptable ROC values (≥0.7) for differentiating between women with and without migraines or between women with episodic and chronic migraines. Conclusions: Although the women with migraines had widespread pressure-pain hyperalgesia, neither the clinical, psychological nor psychophysical (pain threshold) variable exhibited the proper diagnostic accuracy to distinguish between women with and without migraines or between women with episodic and chronic migraines. New studies should clarify the clinical relevance of the findings of the current study.

Studying the Effect of Expectations on High-Frequency Electrical Stimulation-Induced Pain and Pinprick Hypersensitivity

Negative expectations can increase pain, but can they promote the development of central sensitization? This study used an inert treatment and verbal suggestions to induce expectations of increased high-frequency electrical stimulation (HFS)-induced pain and assessed their effects on pain ratings during HFS and HFS-induced pinprick hypersensitivity. Fifty healthy volunteers were randomly allocated to either a control group (N = 25) or a nocebo group (N = 25). Participants in both groups received a patch containing water on the right forearm. The nocebo group was told that the patch contained capsaicin that sensitized their skin, while the control group was told that the patch contained water that had no effect on skin sensitivity. Before and after patch attachment, single electrical stimuli were delivered to the area of the patch to measure the perceived intensity to these stimuli. After patch removal and after the participant rated expected pain and fear for HFS, HFS was delivered to the same skin site, followed by the assessment of pinprick sensitivity. The nocebo group rated the perceived intensity for the single electrical stimulus after removal of the patch as more intense compared with the control group, indicating that our manipulation worked. Yet, this effect did not transfer to expected pain for HFS, nor did it affect pain intensity ratings during HFS. HFS increased pinprick sensitivity but no group differences were found. Because of the lack of differences in expected pain and pain intensity ratings for HFS between groups, no firm conclusions can be drawn regarding their effect on pinprick hypersensitivity. PERSPECTIVE: This study shows that sham treatment combined with verbal suggestions induces a nocebo effect but does not necessarily change expectations and experience of upcoming pain.

Multisensory sensitivity in relation to pain: a scoping review of terminology and assessment

Chronic pain is a debilitating health problem affecting 20 million Americans annually. Most patients with chronic pain report negative impacts on daily function and quality of life, which can result in devastating emotional and financial stress. Although the causes of chronic pain remain elusive, there is increasing interest in sensitivity to everyday sensory stimuli as it relates to chronic pain, potentially serving as an indirect marker of altered central nervous system sensory processing. However, sensitivity to multiple sensory inputs, eg, bright lights, certain fabrics, loud noises, etc, is described using multiple terminologies. The lack of a common vocabulary makes it difficult to find and summarize related discoveries, potentially inhibiting scientific progress. Thus, the purpose of this scoping review was to identify and characterize the terminology used in publications assessing some form of multisensory sensitivity as it relates to pain (eg, a pain cohort or pain sensitivity). Our review of 6 databases (PubMed, Scopus, Embase, CINAHL, PsycINFO+, and Cochrane) comprehensively cataloged peer-reviewed studies published through March 2023 in this domain. Of 12,841 possible studies identified, 92 met all inclusion criteria, with over 80% being published in the last decade. A wide range of terminology has been used for this construct, likely in part a result of the many different professional disciplines represented. These results provide valuable insights for future development of a standardized vocabulary and serve as a resource to aid future investigators of multisensory sensitivity and pain in their study design.

Abdominal Pain in Inflammatory Bowel Disease-Epidemiology, Pathophysiology, and Management: A Narrative Review

Abdominal pain is a major symptom of inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, and has a significant impact on patients' quality of life. Given the evolving understanding of IBD pathology and management strategies, there is an urgent need to review the recent research findings. In this review, we have analyzed the epidemiology, pathophysiology, and management of abdominal pain in IBD over the past decade. We draw on the current literature and highlight emerging trends, challenges, and advances in this field. By synthesizing key findings, this review provides insights into the complex interplay between abdominal pain, disease progression, and therapeutic interventions for IBD.

The Association Between the Central Sensitisation Inventory and Temporomandibular Disorders Is Confounded by Migraine, Depression, Widespread Pain and Parafunction. A Cross-Sectional Telehealth Study

BACKGROUND

Temporomandibular disorders (TMDs) are conditions that involve the temporomandibular joints, masticatory muscles, and associated tissues, causing orofacial pain. Central sensitisation (CS) is a relevant part of the TMD pathophysiology. Migraine, psychological aspects, parafunctional oral habits and widespread pain are commonly associated with both TMD and CS and could confound the association between them.

OBJECTIVES

To investigate the association between painful TMD and the Central Sensitisation Inventory (CSI) score, and to assess the presence of confounders in this association.

METHODS

Cross-sectional study that assessed women with and without orofacial pain complaints using telehealth. The TMD Pain Screener and an online physical examination determined the presence of painful TMD. The following questionnaires were applied: CSI, Headache Screening Questionnaire, Generalized Anxiety Disorder-7, Patient Health Questionnaire-9, Oral Behavior Checklist, Jaw Functional Limitation Scale and the Nordic musculoskeletal questionnaire. A single regression investigated the association between the CSI score and TMD, and a multiple regression investigated the effect of the other outcomes as possible confounders. Confounding was considered present when the association between TMD and the CSI score changed more than 10% after adding a possible confounder to the regression model.

RESULTS

Forty-two women with painful TMD and 53 without TMD were included. There was a significant association between the CSI score and the presence of painful TMD (R2 = 0.639; p < 0.001). This association changed when the following outcomes were added to the model: presence of migraine, symptoms of depression, widespread pain and parafunctional oral habits.

CONCLUSION

The positive association between TMD and the CSI score was confounded by migraine, symptoms of depression, widespread pain and parafunctional oral habits.

Discordant dry eye disease and chronic pain: A systematic review and meta-analysis

PURPOSE

To evaluate the relative contributions of objective and subjective indicators of dry eye disease (DED) in individuals with chronic pain conditions compared with controls.

METHODS

A systematic review and meta-analysis was conducted of studies that reported the signs and symptoms of DED and/or their prevalence in individuals with chronic pain compared with controls. International Association for the Study of Pain (IASP) International Classification of Diseases (ICD)-11 codes for chronic pain conditions were applied, and outcomes defined as DED signs and symptoms. A search strategy utilised the EMBASE, Web of Science, Cochrane Library and MEDLINE databases. Risk of bias assessment was performed with the Newcastle-Ottawa scale. Random effects meta-analysis calculated mean differences (MD) and odds ratios (OR), while subgroup analysis of different chronic pain conditions explored their relative association with the signs and symptoms of DED. Evidence certainty was evaluated using Grades of Recommendation, Assessment, Development, and Evaluation (GRADE).

RESULTS

Fourteen observational studies comprising 3,281,882 individuals were included. Meta-analysis found high quality evidence that individuals with chronic pain were more likely to experience symptoms of DED than controls (OR = 3.51 [95 %CI: 3.45,3.57]). These symptoms were more severe (MD = 18.53 [95 %CI: 11.90, 25.15]) than controls with a clinically meaningful effect size. Individuals with chronic pain had more rapid tear film disruption (MD = -2.45 [95 %CI: -4.20, -0.70]) and reduced tear production (MD = -5.57 [95 %CI: -9.56, -1.57]) compared with controls (with moderate evidence quality). High quality evidence revealed individuals with chronic pain had lower basal tear production (anaesthetised) than controls (MD = -2.59 [95 %CI: -3.60, -1.58]). Tear film osmolarity showed no significant differences between the chronic pain and pain-free groups. Group differences for DED signs were not considered clinically meaningful.

CONCLUSION

More severe, clinically meaningful symptoms of DED were reported in individuals with chronic pain than controls, however group differences for the signs of DED were typically of limited or questionable clinical relevance. This ocular phenotype where DED is felt more than it is seen in chronic pain may reflect underlying sensory hypersensitivity, shared by both conditions and contributing to their frequent comorbidity. Advancing understanding of this potential pathophysiological mechanism may guide clinical management.

Temporal summation of pain in sickle cell disease: comparison of adolescents and young adults with chronic vs. infrequent pain

OBJECTIVE

This study examined the role of central sensitization in the experience of pain among adolescents and young adults with the most severe genotypes of sickle cell disease (SCD). We hypothesized that adolescents and young adults with chronic SCD pain would demonstrate a higher perceptual response to repeated stimulation of identical intensity (i.e., temporal summation of pain, TSP) compared to counterparts with infrequent pain. We also examined psychological risk factors that can impact pain sensitivity.

METHODS

Patients ages 12-21 years, diagnosed with SCD type Hb SS or Hb S Beta0Thalasemia, who reported infrequent pain (≤2 pain days/month; n = 25) or met AAPT criteria for chronic SCD pain (n = 25) were enrolled. Patients were age- and sex-matched, with similar proportions receiving chronic blood transfusion and hydroxyurea. Patients completed static quantitative sensory testing (QST) and dynamic TSP testing to assess pain sensitivity. Patients and a caregiver completed demographic and psychological measures (depression, anxiety, pain interference, pain catastrophizing).

RESULTS

Simple slope analysis revealed differentially elevated heat TSP among adolescents and young adults with chronic SCD pain (b = 3.14, p = .002) but not those with infrequent pain (b = 0.45, p = .61). Faster habituation was further observed for those with chronic compared to infrequent pain. Adolescents and young adults with chronic pain reported more frequent depression, anxiety, and pain interference symptoms; however, psychological symptoms and pain catastrophizing were not associated with QST or TSP (ps >.17).

CONCLUSION

Current results demonstrate that a well-established, prognostic, QST risk marker (i.e., TSP) may distinguish chronic from infrequent pain subgroups of adolescents and young adults with SCD.

Comparable Conditioned Pain Modulation and Painful-Exercise-Induced Hypoalgesia in Healthy Young Adults: A Randomized Crossover Trial

Conditioned pain modulation and exercise-induced hypoalgesia reflect inhibitory pain controls emanating from the brain. The aim of this study was to compare the extent of pain inhibition from exercise-induced hypoalgesia (isometric wall squat), conditioned pain modulation (cold-water immersion), and their combination (wall squat followed by cold water in fixed order) in healthy pain-free adults. Sixty-one participants (median age 21 years) completed 3 sessions (wall-squat, cold-water, and combined) in random order. Sessions were separated by at least a week. In each session, pressure-pain thresholds, single-pinprick-pain ratings, and pinprick-temporal summation of pain (the fifth minus the first) were obtained at quadriceps, forearms, and forehead, before and after wall squat and/or cold water. Each intervention inhibited pain to pressure (partial η2 = .26) and single pinprick (partial η2 = .16) to a similar extent; however, pressure-pain inhibition was negligible in the forehead. After adjusting for age and sex, single-pinprick-pain inhibition in the forehead induced by wall squat was associated with that induced by cold water (adjusted R2 = .15; P = .007), and stronger pain inhibition was predicted by a higher thigh-pain rating to wall squat (adjusted R2 = .10; P = .027). Neither intervention affected pinprick-temporal summation of pain. Together, the findings suggest that pain-inhibitory effects of exercise-induced hypoalgesia and conditioned pain modulation may overlap when exercise is at least moderately painful (6/10 intensity). Pressure pain in body regions remote from the exercised or conditioned sites may be weakly modulated. PERSPECTIVE: The current findings suggest that pain-inhibitory effects induced by painful wall squat and by cold-water immersion may overlap. The magnitude of pain inhibition in the forehead remote from the exercised thigh or the conditioned foot appears smaller, which could be examined further in future research.

Understanding neuropathic pain: the role of neurophysiological tests in unveiling underlying mechanisms

Neuropathic pain, arising from lesions of the somatosensory nervous system, presents with diverse symptoms including ongoing pain, paroxysmal pain, and provoked pain, usually accompanied by sensory deficits. Understanding the pathophysiological mechanisms behind these symptoms is crucial for targeted treatment strategies. Neurophysiological techniques such as nerve conduction studies, reflexes, and evoked potentials help elucidate these mechanisms by assessing large myelinated non-nociceptive fibres and small nociceptive fibres. This argumentative review highlights the importance of tailored neurophysiological assessments for improving our understanding of the pathophysiological mechanisms behind neuropathic pain symptoms.

Sensitization-associated and neuropathic-associated symptoms in patients with unilateral lateral elbow tendinopathy: an exploratory study

OBJECTIVES

We evaluate the presence of sensitization-associated symptoms and neuropathic pain features and identify if there is an association between these symptoms and pressure pain sensitivity, pain, and related-disability in lateral elbow tendinopathy.

METHODS

Thirty-seven (43% women, age: 45.5 ± 9.5 years) patients with lateral elbow tendinopathy completed: demographic (i.e. age, height, and weight); clinical (i.e. pain history, pain intensity, and Disabilities of the Arm, Shoulder and Hand); and psychophysical (i.e. pressure pain thresholds at the elbow, cervical spine, hand, and leg) outcomes, and the Central Sensitization Inventory and Self-administered Leeds Assessment of Neuropathic Symptoms and Signs questionnaires. Step-wise multiple linear regression models were performed to identify predictors of sensitization- or neuropathic-associated symptoms.

RESULTS

Six (16%) patients exhibited sensitization-associated symptoms (mean: 46.5, SD: 6.1), whereas 13 (35%) patients showed neuropathic-associated symptoms (mean: 13.5; SD: 1.4). Sensitization-associated symptoms were positively associated with neuropathic-associated symptoms (r = 0.538, P = .001) and negatively associated with pressure pain thresholds at the leg (r = -0.378, P = .021). Neuropathic-associated symptoms were positively associated with related-disability (r = 0.479, P = .003) and negatively associated with pressure pain threshold at the elbow (r = -0.394, P = .017). Stepwise regression analyses revealed that neuropathic-like symptoms explained 26.8% of the variance of sensitization symptoms (r2: 0.268), whereas pressure pain threshold at the elbow explained an additional 6.6% to neuropathic-like symptoms (r2: 0.334).

CONCLUSION

This explorative study identified sensitization- and neuropathic-associated symptoms in 16% and 35% of the people with lateral elbow tendinopathy. Sensitization- and neuropathic-associated symptoms were associated. Pressure pain sensitivity at the elbow (peripheral sensitization) was associated with neuropathic -associated symptoms.

Do measures of central sensitization relate to movement-evoked pain in people with chronic low back pain? A longitudinal prospective study

BACKGROUND

One of the most frequent complaints among people with musculoskeletal pain is pain during physical activity, commonly referred to as movement-evoked pain. It is suggested to be associated with quantitative sensory testing measures of central pain process in individuals with musculoskeletal pain.

OBJECTIVE

To investigate the predictive association between movement-evoked pain scores and measures of central sensitization in patients with chronic nonspecific low back pain. The secondary aim was to determine whether changes in movement-evoked pain scores are associated with changes in measures of central sensitization.

METHODS

In this longitudinal prospective study, 50 participants with chronic low back pain were included. Pain pressure thresholds, temporal summation of pain, descending pain modulation, and the central sensitization index were assessed as measures of central sensitization. Movement-evoked pain was evaluated using the Back Performance Scale and a 5-minute walk test.

RESULTS

Measures of central sensitization, specifically pressure pain thresholds and temporal summation, demonstrated predictive associations with movement-evoked pain measures. In response to treatment, improvements in movement-evoked pain were associated with improvements in measures of central sensitization (i.e., pressure pain thresholds and temporal summation) and improved pressure pain thresholds in the plantar toe significantly predict movement-evoked pain measures experienced during the 5-minute walk test.

CONCLUSIONS

These results imply that movement-evoked pain is related to processes related to central modulation of pain in patients with nonspecific chronic low back pain.

An interdisciplinary perspective on peripheral drivers of pain in rheumatoid arthritis

Pain is one of the most debilitating symptoms of rheumatoid arthritis (RA), and yet remains poorly understood, especially when pain occurs in the absence of synovitis. Without active inflammation, experts most often attribute joint pain to central nervous system dysfunction. However, advances in the past 5 years in both immunology and neuroscience research suggest that chronic pain in RA is also driven by a variety of abnormal interactions between peripheral neurons and mediators produced by resident cells in the local joint environment. In this Review, we discuss these novel insights from an interdisciplinary neuro-immune perspective. We outline a potential working model for the peripheral drivers of pain in RA, which includes autoantibodies, resident immune and mesenchymal cells and their interactions with different subtypes of peripheral sensory neurons. We also offer suggestions for how future collaborative research could be designed to accelerate analgesic drug development.

From fibrositis to fibromyalgia to nociplastic pain: how rheumatology helped get us here and where do we go from here?

Rheumatologists and rheumatology have had a prominent role in the conceptualisation of nociplastic pain since the prototypical nociplastic pain condition is fibromyalgia. Fibromyalgia had been previously known as fibrositis, until it became clear that this condition could be differentiatied from autoimmune disorders because of a lack of systemic inflammation and tissue damage. Nociplastic pain is now thought to be a third descriptor/mechanism of pain, in addition to nociceptive pain (pain due to peripheral damage or inflammation) and neuropathic pain. Nociplastic pain can occur in isolation, or as a co-morbidity with other mechanisms of pain, as commonly occurs in individuals with autoimmune disorders. We now know that the cardinal symptoms of nociplastic pain are widespread pain (or pain in areas not without evidence of inflammation/damage), accompanied by fatigue, sleep and memory issues. There is objective evidence of amplification/augmentation of pain, as well as of non-painful stimuli such as the brightness of lights and unpleasantness of sound or odors. Nociplastic pain states can be triggered by a variety of stressors such as trauma, infections and chronic stressors. Together these features suggest that the central nervous system (CNS) is playing a major role in causing and maintaining nociplastic pain, but these CNS factors may in some be driven by ongoing peripheral nociceptive input. The most effective drug therapies for nociplastic pain are non-opioid centrally acting analgesics such as tricyclics, serotonin-norepinephrine reuptake inhibitors and gabapentinoids. However the mainstay of therapy of nociplastic pain is the use of a variety of non-pharmacological integrative therapies, especially those which improve activity/exercise, sleep and address psychological co-morbidities.

Contribution of inflammation markers and quantitative sensory testing (QST) indices of central sensitisation to rheumatoid arthritis pain

BACKGROUND

Pain, the primary complaint in rheumatoid arthritis (RA), is multifaceted, and may be driven by inflammatory disease activity and central sensitisation. We aimed to ascertain what proportion of RA pain severity is explained by markers of inflammation and quantitative sensory testing (QST) indices of central sensitisation.

METHODS

This was a cross-sectional analysis of data from individuals with clinically active RA. Pain severity was assessed using numerical rating scales and inflammation via 28-joint Disease Activity Score (DAS28) and Ultrasound (Greyscale, Power Doppler). Pain sensitivity was assessed by 'static' (tibialis anterior or brachioradialis pressure pain detection threshold-PPT-TA/PPT-BR) and 'dynamic' (temporal summation-TS, conditioned pain modulation-CPM) QST. Bivariate associations used Spearman's correlation coefficients, and multivariable linear regression models determined relative contributions to pain severity.

RESULTS

In bivariate analyses of N = 96 (age 65 ± 10y, 77% females) people with RA, pain severity was significantly associated with inflammation indices (r = 0.20 to 0.55), and CPM (r=-0.26). In multivariable models that included TS, CPM, age, sex, and body mass index, inflammation indices remained significantly associated with pain severity. Multivariable models explained 22 to 27% of pain variance. Heterogeneity was apparent for associations with pain between subscores for pain now, strongest or average over the past 4-weeks.

CONCLUSIONS

In individuals with clinically active RA, markers of inflammatory disease activity best explain RA pain with only marginal contributions from QST indices of central sensitisation. Although inflammation plays a key role in the experience of RA pain, the greater proportion of pain severity remains unexplained by DAS28 and ultrasound indices of inflammation.

The effects of C-tactile stimulation on temporal summation of second pain: A study of the central and peripheral neural correlates

Affective touch is mediated by specialized receptors sensitive to gentle and slow touch called C-tactile afferents (CT). The activation of these receptors has shown promise in reducing subjective pain ratings, however, how this type of touch can affect central sensitization processes is poorly studied. This work aimed to investigate if affective touch is able to modulate pain sensitization and its electrophysiological correlates during Temporal Summation of Second Pain (TSSP), a phenomenon characterized by an increase in pain perception due to repeated noxious stimuli. Thirty-seven participants underwent a TSSP protocol involving three conditions: TSSP alone, TSSP during vibrotactile stimulation, and TSSP during CT stimulation (administered with a brush mounted in a robot arm). We measured subjective pain ratings, electroencephalographic (N2-P2 complex) and electrocardiographic activity during these conditions. Participants reported a significantly lower increase of pain during CT stimulation compared to vibrotactile stimulation, but not to TSSP alone. In addition, TSSP was reduced when administered in the ipsilateral arm compared to the other somatosensory stimulation. Subjective reports of attention towards painful stimuli, amplitude of the N2-P2 complex, and heart rate were also reduced during CT stimulation. Conclusion: Our results indicated that the activation of CT receptors may reduce sensitization compared to other types of somatosensory stimulation, which is possibly related to the reduction of the attention devoted to nociceptive stimulation. Our results suggest that activation of CT receptors may alleviate the occurrence of central pain sensitization.

Pressure and cold pain threshold reference values in a pain-free older adult population

Background

More sex-specific pain sensitivity normative values from population-based cohorts in pain-free older adults are required. The aims of this study were (1) to provide sex- and age-specific normative values of pressure and cold pain thresholds in older pain-free adults and (2) to examine the association of potential correlates of pain sensitivity with pain threshold values.

Methods

This study investigated sex-specific pressure (lumbar spine, tibialis anterior, neck and dorsal wrist) and cold (dorsal wrist) pain threshold estimates for older pain-free adults aged 41-70 years. This cross-sectional study used participants (n = 212) from the Raine Study Gen1-26 year follow-up. The association of pain thresholds, with correlates including sex, test site, ethnicity, waist-hip ratio, smoking status, health-related quality of life, depression, anxiety and stress symptoms, sleep quality, socioeconomic status and physical activity levels, was examined.

Results

Values for pressure and cold pain thresholds for older pain-free adults are provided, grouped by vicennium, sex and test site (pressure). Statistically significant independent correlates of increased pressure pain sensitivity were test site, ethnicity and sex. Only lower waist/hip ratio was a statistically significant, independent correlate of increased cold pain sensitivity.

Conclusions

This study provides robust sex- and age-specific normative values for pressure pain threshold and cold pain threshold for an older adult pain-free population. Combined with existing values, these data provide an important resource in assisting interpretation of pain sensitivity in clinical pain disorders and provide insights into the complex association of pain sensitivity with correlates that can be used in research.

Endogenous pain modulation after sleep restriction in migraine: a blinded crossover study

BACKGROUND

Patients with migraine are vulnerable to insufficient sleep, but the impact of sleep restriction is largely unknown. In addition, the importance of sleep may be different in patients with migraine who mostly have attack onsets during sleep, so called sleep-related migraine, compared to patients with non-sleep-related migraine. In this study we investigate the effect of sleep restriction on endogenous pain modulation in patients with migraine and healthy controls. We also compared the effect of sleep restriction in sleep-related and in non-sleep-related migraine.

METHODS

Measurements were conducted in 39 patients with migraine between attacks and 31 controls, once after habitual sleep and once after two consecutive nights of partial sleep restriction. There were 29 and 10 patients with non-sleep-related and sleep-related migraine respectively. Test stimulus was 2-min tonic noxious heat to the left volar forearm. Temporal summation was calculated as the regression coefficient for rated pain in the late part of this 2-min stimulation. Conditioning stimulus was right hand-immersion in 7 °C water. Conditioned pain modulation was defined as the difference in rated pain with and without the conditioning stimulus and was calculated for temporal summation and mean rated pain for the test stimulus. The effect of sleep restriction on temporal summation and conditioned pain modulation was compared in migraine subjects and controls using two-level models with recordings nested in subjects.

RESULTS

Conditioned pain modulation for temporal summation of heat pain tended to be reduced after sleep restriction in patients with migraine compared to controls (p = 0.060) and, in an exploratory analysis, was reduced more after sleep restriction in sleep-related than in non-sleep-related migraine (p = 0.017). No other differences between groups after sleep restriction were found for temporal summation or conditioned pain modulation.

CONCLUSION

Patients with migraine may have a subtly altered endogenous pain modulation system. Sleep restriction may have an increased pronociceptive effect on this system, suggesting a mechanism for vulnerability to insufficient sleep in migraine. This effect seems to be larger in sleep-related migraine than in non-sleep-related migraine.

Neuroplasticity in the transition from acute to chronic pain

Acute pain is a transient sensation that typically serves as part of the body's defense mechanism. However, in certain patients, acute pain can evolve into chronic pain, which persists for months or even longer. Neuroplasticity refers to the capacity for variation and adaptive alterations in the morphology and functionality of neurons and synapses, and it plays a significant role in the transmission and modulation of pain. In this paper, we explore the molecular mechanisms and signaling pathways underlying neuroplasticity during the transition of pain. We also examine the effects of neurotransmitters, inflammatory mediators, and central sensitization on neuroplasticity, as well as the potential of neuroplasticity as a therapeutic strategy for preventing chronic pain. The aims of this article is to clarify the role of neuroplasticity in the transformation from acute pain to chronic pain, with the hope of providing a novel theoretical basis for unraveling the pathogenesis of chronic pain and offering more effective strategies and approaches for its diagnosis and treatment.

Exercise-induced changes in central sensitization outcomes in individuals with chronic musculoskeletal pain: A systematic review with meta-analysis

BACKGROUND AND OBJECTIVE

Temporal summation of pain (TSP) and conditioned pain modulation (CPM) are the two most commonly used clinical measures of central sensitization (CS). However, the effectiveness of exercise on TSP and CPM has yet to be evaluated. This review aims to investigate the effect of exercise alone on CS outcomes in individuals with chronic musculoskeletal pain.

DATABASES AND DATA TREATMENT

This is a systematic review and meta-analysis. MEDLINE, EMBASE, CINAHL, PEDro and Cochrane databases were searched. Data were extracted based on the exercise modality and grouped into aerobic, resistance, isometric, or motor control modalities. Risk of bias was assessed using RoB2, RoB2 for crossover trials and ROBINS-I tools. Quality of evidence was assessed using GRADE. Random-effects meta-analyses were conducted, with subgroup analysis conducted for each exercise modality.

RESULTS

The meta-analyses included thirteen studies, consisting of eight non-randomized studies, three randomized controlled trials and three randomized crossover trials. Data were categorized into four subgroups for analyses based on exercise modality. No statistically significant effect existed for both TSP and conditioned pain modulation. However, motor control exercise was found to have a significant enhancing effect on conditioned pain modulation. No significant differences were found between the exercise subgroup for both TSP and conditioned pain modulation.

CONCLUSIONS

We did not find an overall effect of physical exercise on TSP and CPM. However, subgroup analysis shows favourable effects of motor control exercise in individuals with chronic neck pain. Future research should focus on exercise modality and dosage and their role in the mechanism involved in TSP and CPM in predefined populations.

SIGNIFICANCE STATEMENT

Results from this study found that motor control exercise has a significant enhancing effect on conditioned pain modulation, with subgroup analysis showing favourable effects of motor control exercise in individuals with chronic neck pain. This indicates that physical exercise may have a positive effect on central sensitisation in individual with chronic neck pain. However, differential effects may exist between different types of exercise. These findings will inform understanding of neurobiological effects underlying chronic neck pain and may guide the development of more effective, personalised treatments.