Chronic nociplastic pain affecting the musculoskeletal system: clinical criteria and grading system

Central aspects of pain associated with physical activity: results from the Investigating Musculoskeletal Health and Wellbeing cohort

Background

Knee pain reduces activity, while inactivity can increase pain. The central nervous system modulates both pain and activity. The 8-item Central Aspects of Pain (CAP) questionnaire measures self-reported symptoms associated with current and future knee pain severity and psychophysical evidence of central pain sensitivity. The objective was to explore associations between CAP and physical inactivity in people with knee pain.

Methods

Participants from the Investigating Musculoskeletal Health and Wellbeing cohort who reported their knee as their most troublesome joint with numerical rating scale pain severity ≥1/10 completed questionnaires at baseline and 12 months addressing demographic and clinical characteristics, CAP questionnaire, and physical inactivity (Frail Non-Disabled questionnaire item). Chi-squared, correlations and multivariable logistic regression were performed.

Results

Seven hundred twenty-two participants provided baseline data and 404 longitudinal data. Higher baseline CAP scores were associated with higher baseline pain severity {OR: 1.25 (95% confidence interval [CI]: 1.02-1.53); P = 0.032} and physical inactivity (OR: 1.18 [95% CI: 1.11-1.25]; P < 0.001). Increasing CAP scores over 12 months were associated with becoming physically inactive (OR: 1.16 [95% CI: 1.01-1.32]; P = 0.032). The effects of CAP on physical inactivity were not fully explained by pain severity nor by any single characteristic of widespread pain distribution, emotional or cognitive factors, sleep disturbance, or fatigue.

Conclusion

Central aspects of pain questionnaire displays cross-sectional and longitudinal associations with physical inactivity. Central nervous system manifestations of pain appear to link pain with physical activity and may be more important than pain severity.

Limited association between central pain processing and clinical outcomes in non-specific chronic neck pain after a manual therapy intervention: A secondary analysis

BACKGROUND

Non-specific chronic neck pain (NSCNP) is a prevalent condition causing significant disability. While manual therapy is recommended, its clinical benefits are limited. The relationship between central pain processing and treatment outcomes in NSCNP remains unclear.

OBJECTIVES

To assess whether central pain processing measures could predict manual therapy outcomes in NSCNP patients.

DESIGN

Pre-planned secondary analysis.

METHODS

Sixty-three NSCNP patients underwent a four-week manual therapy regimen. Central pain processing mechanisms were assessed using Pressure Pain Threshold (PPT), Temporal Summation of Pain (TSP), and Conditioned Pain Modulation (CPM). Clinical outcomes were measured using the Neck Disability Index (NDI), pain intensity, and the Global Rating of Change Scale (GRoC). Univariate and multivariate regression models explored associations between baseline variables and treatment outcomes.

RESULTS

Multivariate analysis identified baseline CPM and neck pain duration as significant predictors of treatment outcome based on GRoC. A weak negative association was found between CPM and GRoC (p < 0.05), suggesting that patients with lower CPM response reported better perceived outcomes. Baseline NDI was inversely associated with changes in disability (p < 0.01). Baseline pain intensity (p < 0.01) and duration (p < 0.05) were inversely related to pain reduction, while baseline CPM narrowly missed significance. No significant associations were found between TSP, PPT, and clinical outcomes.

CONCLUSION

The findings suggest a limited association between pre-treatment central pain processing status and manual therapy outcomes in NSCNP patients. The lower CPM response was modestly predictive of better outcomes, contrary to expectations. Routine use of QST measures to guide treatment decisions in this population is not supported by current data.

Complaints and pain predominance in running-related injuries: A Bayesian inference analyses

INTRODUCTION

Evidence on running-related injuries (RRIs) complaints/symptoms is scarce, raising concerns about defining RRIs by pain alone and highlighting the lack of data on pain's symptoms predominance among runners sustaining injuries.

AIMS

To investigate the main complaints/symptoms of RRIs and to investigate how running-related pain is distributed across duration and pain symptoms predominance.

METHODS

A total of 346 adult runners with ≥3 months of running experience, with no history of surgery and sustaining running-related injuries were included. The outcomes were the complaints/symptoms of RRIs, and the classifications of running-related pain regarding duration (acute or persistent) and pain symptoms predominance (nociceptive, neuropathic and nociplastic). Bayesian analyses estimated proportions using non-informative priors due to a lack of prior scientific evidence on RRIs complaints/symptoms.

RESULTS

The main complaint/symptom of running-related injuries was pain (94.5%, 95% credible interval [CrI] 92.0 to 96.7, n = 327), followed by foot blisters (11.0%, 95% CrI 7.9 to 14.4, n = 38). Persistent pain with nociceptive symptoms (51.1%, 95% CrI 45.6 to 56.5, n = 167) and acute pain with nociceptive symptoms (45.9%, 95% CrI 40.5 to 51.2, n = 150) were the most frequent pain classifications. Cases of 'acute neuropathic-like symptoms' were not reported.

DISCUSSION

Study suggests pain is not the sole symptom of running injuries. Broader definitions capturing any complaints may better represent injury burden for runners.

CONCLUSION

'Musculoskeletal pain' is the main complaint of RRIs. A quarter of injured runners also experience additional complaints besides pain. Our study highlighted prevalent pain symptoms predominance, with 'persistent pain with nociceptive symptoms' and 'acute pain with nociceptive symptoms' being the most common.

Brain inflammation and its predictive value for post-operative pain in total knee arthroplasty patients

Recent evidence suggests that chronic pain patients exhibit elevated brain levels of the neuroinflammation marker 18 kDa translocator protein (TSPO). However, the clinical significance of brain TSPO elevations, and their responses to pain interventions, remain unknown. To explore these questions, we studied patients with knee osteoarthritis (KOA) undergoing total knee arthroplasty (TKA), a procedure which is curative for most, but carries a relatively high risk of persistent post-surgical pain. Pre-surgical KOA patients (n = 41) and healthy controls (n = 22) underwent brain positron emission tomography/magnetic resonance imaging, using the TSPO radioligand [11C]PBR28. A subset of KOA patients (n = 27) returned for a second scan one-year post-TKA. When compared groups, pre-surgical KOA patients exhibited widespread[11C]PBR28 PET signal elevations (Standardized Uptake Value Ratio), with pituitary uptake positively correlating with knee pain severity (rho = 0.51; p = 0.003). A voxel-wise paired t-test revealed that while most brain regions showed no change post-surgery, the [11C]PBR28 PET signal significantly decreased in the thalamus and caudate, reaching control levels. Additionally, a Support Vector Machine model based on pre-surgical imaging, clinical, and demographic features, achieved a correlation of rho = 0.487 (p = 0.001) between the predicted and actual pain improvement. Top predictive features included [11C]PBR28 uptake in the pituitary gland, cuneal cortex, amygdala and other regions. This study suggests that neuroinflammation 1) is widespread in KOA and, in some regions, 2) is linked to pain severity, 3) undergoes normalization following TKA, and 4) can predict post-surgical TKA outcomes. Understanding the neuroinflammatory mechanisms in KOA and post-surgical pain may guide targeted interventions and improve patient outcomes.

[Nociplastic pain in Primary Care: What should we know?]

Nociplastic pain, third mechanistic pain descriptor, was adopted in 2017 by the International Association for the Study of Pain. It is defined as «pain that arises from altered nociception» not fully explained by nociceptive or neuropathic pain mechanisms. Peripheral and/or central sensitization, manifesting as allodynia and hyperalgesia, is typically present, although not specific for nociplastic pain. Understanding pathophysiological mechanisms and their interactions is a requisite for the development of diagnostic tests allowing for individualized treatments and development of new strategies for prevention and treatment. This narrative review summarizes the most important aspects of nociplastic pain in the Primary Care setting and emphasizes the importance of recognizing this type of pain in clinical practice.

Altered Gut Microbiome Composition and Function in Individuals with Complex Regional Pain Syndrome

BACKGROUND

Complex regional pain syndrome is a chronic pain syndrome typically affecting a limb. It is characterized by severe spontaneous and evoked pain, along with vasomotor, autonomic, and motor signs and symptoms. Although dysregulation in several physiologic systems has been suggested in complex regional pain syndrome (CRPS), including aberrant inflammatory and immune responses, vasomotor dysfunction, and nervous system changes, the pathophysiologic mechanisms underlying the syndrome remain elusive. Effective treatment options are also limited. Previous research has highlighted the role of the gut microbiome in chronic pain, prompting us to investigate the composition and function of the gut microbiome in CRPS.

METHODS

The gut microbiomes of individuals with CRPS to age-, sex-, and ethnicity-matched pain-free control participants were compared using 16S rRNA gene amplification. To minimize environmental confounders, participants were recruited from two geographically independent regions. To explore potential changes in gut bacteria-derived metabolites, targeted metabolomic analysis of feces and plasma was performed. Finally, machine learning algorithms were trained to identify the gut microbiome composition specific to CRPS patients and were tested on a validation cohort.

RESULTS

In this study, differential abundance analysis revealed significant differences in several bacterial taxa when comparing 53 CRPS patients to 52 unrelated controls, including alterations in short-chain fatty acid-metabolizing species. Targeted stool and plasma metabolite analysis confirmed differences in fecal and plasma short-chain fatty acid levels between CRPS patients and controls. Notably, the microbiome composition alone allowed accurate classification of patients and controls in a geographically independent test cohort.

CONCLUSIONS

These findings highlight unique compositional and functional changes in the gut microbiome of individuals with CRPS, thus contributing to the growing body of evidence supporting the role of the gut microbiome in chronic pain syndromes. Furthermore, they pave the way for further studies elucidating the pathophysiology of CRPS and exploring new diagnostic aids and treatment modalities.

"Exploring The Nexus": Chronic musculoskeletal pain in diabetic vs non-diabetic population

Introduction

Diabetes-mellitus (DM) has transcended the boundaries and affected populations across globe, it predisposes individual to stiffness and musculoskeletal-pain due to accumulation of glycation-end-products. Musculoskeletal-pain is a common yet frequently neglected complication. Pain mechanisms have been categorized as nociceptive, neuropathic, nociplastic, and idiopathic. Four criteria were put by Kosek-et-al to identify nociplastic pain that affects the musculoskeletal-system. Study aimed to evaluate prevalence of chronic musculoskeletal (cMSK) pain and its association with diabetes and glycaemic control and to evaluate comorbid conditions of cMSK pain.

Methods and materials

A prospective case-control study was conducted at a level-1-tertiary-care-facility. Patients with type-2 DM above 30-years-age who visited outpatient department participated in the study (study group). Age-matched equal number of healthy individuals (control-cohort) were recruited in the study. We collected data from 300 participants in each group. Analysis was done based-on HbA1c-levels, random-blood-sugar (RBS),clinical-history, and comorbidities. Information regarding cMSK-pain was gathered using modified version of Nordic standard questionnaire.

Results

Overall prevalence of cMSK pain was 23.3 % (140 out of 600). Among Group-1/Diabetic group, it was 27.7 % and among group-2/Healthy Cohort it was 19 % and the odds ratio was 1.6. Most commonly reported region with cMSK among group-1 and group-2 was shoulder (32.5 %) and knee (36.8 %) respectively. We found a significant association between cMSK-pain and HbA1c levels (p < 0.005). and individuals with HbA1c levels of more than 12 reported involvements in multiple regions. We didn't find significant association between cMSK and DM, HTN, dyslipidemia, or hypothyroidism (P > 0.05).

Conclusion

Study highlights higher-prevalence and significant impact of cMSK pain in diabetic patients compared to non-diabetic individuals. Addressing musculoskeletal-pain is crucial for improving overall quality-of-life in diabetic patients. Clinicians should adopt a proactive and comprehensive approach to pain management in diabetics. Using a simple Nordic questionnaire during routine check-ups helps with screening of joint and surrounding soft tissue pathology, preventing future complications that could lead to disability.

[Chronic pain syndrome in musculoskeletal diseases-how different are fibromyalgia and long Covid?-Part 1]

Chronic pain is a common problem in rheumatology. Nociceptive pain is distinguished from neuropathic and nociplastic pain. Mechanistically, the former is explained by persistent inflammation, for example. Included in the second category is nerve damage of various causes. In contrast, nociplastic pain is not caused by tissue damage or a lesion in the somatosensory nerve system. It is caused by an altered sensation of pain through the modulation of stimulus processing. The concept of central sensitization, together with further neurobiological and psychosocial mechanisms, best explains such pain conditions. Fibromyalgia (FM) plays a big part in rheumatology - on the one hand, as a differential diagnosis, and on the other, because the management of inflammatory rheumatic conditions is made more difficult by the simultaneous occurrence of FM. In the context of the coronavirus pandemic, persistent pain syndromes with similarities to FM have been described after COVID-19 infection. There is an increasing scientific controversy whether the so-called long Covid syndrome is an actual entity or "only" a variant of FM. This discussion and the current state of knowledge on the problem are the subject of this review.

Frequency of central sensitization and nociplastic pain in patients with plantar fasciitis : Central sensitization and nociplastic pain in plantar fasciitis

PURPOSE

If the pain persists for a long time in the treatment of plantar fasciitis (PF) or if there is no response to treatment, central sensitization (CS) may develop and the pain may transform into nociplastic pain (NP). This study aimed to evaluate the frequency of CS and NP in patients with PF.

METHODS

This cross-sectional study was undertaken between November 2023 and March 2024. The Foot Function Index (FFI) scale, which evaluates the foot's functionality, was applied to the patient group. The Visual Analog Scale (VAS), which evaluates pain intensity; the Pain-DETECT scale, which evaluates NP; and the Central Sensitization Scale (CSI), which evaluates CS, were applied to patient and control groups.

RESULTS

A total of 206 people were included in the study; 106 were in the patient group with PF, and 100 constituted the control group. While we detected NP in 67 (63.2%) patients according to Pain-DETECT and CS was detected in 91 (85.8%) patients according to CSI among 106 patients with chronic PF; we detected NP in seven (7%) patients according to Pain-DETECT and CS in 44 (44.0%) patients according to CSI among 100 control patients. VAS-score and FFI-pain are moderately and positively correlated with pain-DETECT scores and fairly and positively correlated with CSI scores in the PF group. The pain-DETECT score is moderately and positively correlated with the CSI score in the two groups.

CONCLUSIONS

This is the first study to evaluate the presence of CS and NP in PF patients. We found NP and CS to be common in patients with chronic PF. Effective pain management in patients with PF before it becomes chronic can prevent the development of CS and NP.

Bringing Endometriosis to the Road of Contemporary Pain Science

BACKGROUND

Endometriosis pain is mainly understood based on peripheral lesion characteristics and an outdated perspective equating nociception with pain. This limited view may divert understanding of interventions beyond peripheral logic, leading clinicians to see approaches targeting other processes as supplementary, limiting the effective addressing of treatment failure. Integrating critical advancements in pain and endometriosis can promote more comprehensive knowledge.

OBJECTIVES

This article provides a conceptual framework focusing on overlooked or less clearly linked areas concerning the interplay between nociception and factors influencing endometriosis pain. It explores the complexity of nociceptive processing, the association between neuromerically connected structures, and the role of the brain in pain perception. Further, it emphasizes adopting mechanism-based understanding of pain that integrates neurobiological aspects of the nociceptive apparatus and related systems, shaped by psychosocial factors contributing to a possible negative spiral in those living with endometriosis.

CONCLUSION

Aware of such a broader perspective can incentivize a balanced effort to inquire into peripheral lesion-related mechanisms and other domains potentially impacting endometriosis pain.

Recognition and treatment of attention deficit-hyperactivity disorder in patients with treatment-resistant burning mouth syndrome: a retrospective case study

Introduction

Burning mouth syndrome (BMS) is an idiopathic oral pain disorder characterized by burning sensations and dysesthesia, often complicated by psychosocial factors and psychiatric comorbidities, necessitating a multidisciplinary approach. BMS, classified as nociplastic pain (NcplP), frequently involves central sensitization. Attention-deficit/hyperactivity disorder (ADHD), a neurodevelopmental disorder, is commonly comorbid with NcplP, and ADHD-targeted treatment has shown efficacy in NcplP management. However, the role of ADHD diagnosis and treatment on BMS and associated brain function abnormalities remains unexplored. Therefore, we aimed to investigate the prevalence of ADHD comorbidity and its assessment using ADHD scales and the therapeutic efficacy of an ADHD-focused algorithm, including pre- and post-treatment cerebral blood flow single-photon emission computed tomography (SPECT) results, in patients with treatment-resistant BMS referred from the outpatient clinic of dental psychosomatic specialists at a tertiary care institution for multidisciplinary treatment.

Methods

We retrospectively analyzed data from 14 patients with treatment-resistant BMS who received multidisciplinary care, including psychiatric evaluation and SPECT imaging. Clinical assessments included the Conners' Adult ADHD Rating Scale (CAARS-S and CAARS-O), Pain Numerical Rating Scale, Hospital Anxiety and Depression Scale, and Pain Catastrophizing Scale. Algorithm-based pharmacotherapy using ADHD-effective medications (methylphenidate, atomoxetine, guanfacine, aripiprazole, venlafaxine, and duloxetine) was administered.

Results

ADHD was diagnosed in 13 patients (92.9%), with 57.2% exhibiting borderline or clinical-level symptoms. Clinically significant improvements were observed in all clinical scales among the 10 patients who completed algorithm-based treatment. Brain perfusion SPECT identified hypoperfusion in the frontal lobe and hyperperfusion in the perigenual anterior cingulate cortex, insular cortex, posterior cingulate gyrus, and precuneus in 90% of cases, with improvements noted following treatment.

Conclusions

ADHD is frequently comorbid in patients with treatment-resistant BMS, and ADHD-targeted pharmacotherapy may help alleviate pain, cognitive dysfunction, and brain perfusion abnormalities. These findings suggest that ADHD screening, diagnosis, and multidisciplinary management involving psychiatrists could play a crucial role in optimizing clinical outcomes in patients with BMS.

Estrogen-Mediated Neural Mechanisms of Sex Differences in Burning Mouth Syndrome

BACKGROUND/OBJECTIVES

Burning mouth syndrome (BMS) is a chronic pain disorder of the oral cavity in the absence of organic disease and is prevalent among menopausal women. Estrogen may be involved in the formation of nerves involved in pain.

METHODS

This paper presents an inferred mechanism for the relationship between estrogen and BMS based on a synthesis and interpretation of findings from a selection of published studies.

RESULTS

Estrogen influences the formation of neural circuits in BMS by dividing the complex pain circuit into the following three components: the peripheral pain circuit, brain network pain circuit, and memorized pain circuit.

CONCLUSIONS

The development of BMS may be influenced by the formation of neural circuits by sex hormones.

A systematic review and meta-analysis of pharmacological methods to manipulate experimentally induced secondary hypersensitivity

ABSTRACT

Understanding the physiology of specific clinical features of persistent pain, such as secondary hypersensitivity, is crucial for developing effective treatments. This systematic review and meta-analysis investigated the effects of pharmacological manipulations on the magnitude (primary outcome) and surface area (secondary outcome) of experimentally induced secondary hypersensitivity. Following Cochrane Collaboration guidelines and a published and registered protocol, we conducted an electronic search on February 7, 2024. After screening articles in duplicate, we included 117 articles, consisting of 222 datasets. Risk of bias assessments identified potential flaws in methodological quality. Datasets were pooled by the mechanism of action of the manipulation and by outcome. Effect sizes were estimated using standardised mean difference (SMD). Most datasets (207 of 222) had an unclear risk of performance and detection bias for inadequate reporting of blinding procedures. Thirteen different methods were used to induce, and 23 different drug classes were used to manipulate secondary hypersensitivity. The pooled SMDs [95% CI] suggested that alpha-2-delta subunit of voltage-gated calcium channel ligands reduced both the magnitude (-0.24 [-0.39; -0.08]) and surface area (-0.38 [-0.59; -0.18]) of secondary hypersensitivity, and that both N-methyl-D-aspartate receptor antagonists (-0.36 [-0.55; -0.17]) and voltage-gated sodium channel blockers (-1.02 [-1.63; -0.42]) reduced only the surface area of secondary hypersensitivity. These results suggest a need to understand and compare the physiological underpinnings of magnitude and area of secondary hypersensitivity, and to clarify the relative importance of magnitude vs anatomical spread (ie, surface area) of secondary hypersensitivity to people living with pain.

Application of Algorithm-Based Treatment Approach to Low Back Pain in the Emergency Department

Low back pain accounts for nearly 4 million annual emergency department (ED) visits, and patient outcomes following an ED visit for low back pain are poor. Additionally, only a small portion of patients visiting the ED for low back pain follow up with outpatient physical therapy within 3 months, despite established benefits of early versus delayed physical therapy referral such as improved patient outcomes, less opioid use, and reduced downstream health care utilization. Integrating a physical therapist directly into the ED care team can facilitate evidence-based guideline concordant care and improve patient outcomes, however, physical therapists who are staffed into this role from other settings may lack experience with evaluating and managing patients with acute low back pain. Additionally, there are several unique considerations of the ED care environment which may make existing treatment-based classification approaches difficult to apply in this setting, including physical constraints (eg, delivering care in stretchers and hallways), higher symptom severity and psychosocial stressors necessitating an emergency visit, and greater likelihood of alternative medical diagnoses (eg, kidney stone, aortic aneurysm) contributing to symptoms of low back pain. This perspective presents a modified ED treatment-based classification system (ED-TBC) for low back pain with 3 illustrative case examples. The ED-TBC for low back pain can be used to facilitate guideline concordant care, increase physical therapist confidence in evaluating low back pain in the ED, and reduce clinical practice variation.

The concept of difficult-to-treat disease in rheumatology: where next?

New pathogenesis-based therapeutics and evidence-based consensus treatment recommendations, often with predefined treatment goals, have remarkably improved outcomes across many chronic diseases. However, a clinically significant subgroup of patients responds poorly to interventions and show a progressive decline in the disease trajectory, which poses an increasing health-care challenge. Difficult-to-treat approaches exist in several areas of medicine and the need for similar definitions has recently also emerged in rheumatology. The term difficult-to-treat refers not only to patients with pathology-driven, treatment-refractory disease, but also implicates multiple other factors that can contribute to patients being in this state, including having few treatment options, misdiagnosis, and coincident psychosocial factors. Therefore, the difficult-to-treat state requires a comprehensive, holistic, multidisciplinary approach that considers the specific characteristics of each disease and the personalised needs of the patient. In this Personal View, we provide an overview of the different aspects of the concept of difficult-to-treat disease, highlight its advantages, and propose the importance of incorporating this concept more widely in the design of rheumatological treatment strategies.

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.

Differences in the clinical presentation of chronic whiplash-associated disorders and nontraumatic neck pain: a systematic review and meta-analysis

ABSTRACT

Health outcomes may be worse for individuals with whiplash-associated disorders (WAD) compared to nontraumatic neck pain (NTNP), and clinical characteristics may differ. This systematic review examined evidence comparing WAD and NTNP in terms of pain, disability, psychological status, quality of life, measures of nociceptive processing, movement, sensorimotor, and muscle function. Studies were identified through electronic database searches and included after screening against predefined eligibility criteria. Standardized mean differences (SMD) or mean differences (MD) and 95% confidence intervals (CI) were calculated. Associations between MDs with demographics and study characteristics were explored using meta-regression. Certainty of evidence was assessed using Grades of Recommendation, Assessment, Development, and Evaluation. Sixty-one studies were eligible with 45 included in meta-analysis. Individuals with WAD reported clinically relevant higher disability (100-point Neck Disability Index MD [95% CI] 11.15 [8.63, 13.68]), greater remote cold sensitivity (SMD 0.89 [0.57, 1.21]), lower quality of life (SMD -0.96 [-1.77, -0.16]), greater depression (SMD 0.60 [0.27, 0.93]), greater local (SMD -0.56 [-1.00, -0.13]) and remote (SMD -0.50 [-0.81, -0.19]) pressure sensitivity, less cervical flexion (MD -5.30° [-7.44, -3.16]) and extension (MD -5.43° [-9.31, -1.55]), higher pain intensity (100-point numerical rating scale: MD 8.15 [5.80, 10.50]), and greater kinesiophobia (SMD 0.35 [0.11, 0.59]). No between-group differences were found for dizziness symptoms, stress, anxiety, balance, and local cold sensitivity. Meta-regression indicated that disability differences were negatively associated with age (R2 = 29.6%, P = 0.006). Certainty of evidence was mostly moderate. Individuals with chronic WAD have a worse clinical presentation compared to those with chronic NTNP, which has implications for patient assessment and management.

Small Fibre Pathology in Fibromyalgia: A review

Fibromyalgia syndrome (FMS) presents a complex and challenging disorder in both the diagnosis and treatment, with emerging evidence suggesting a role of small fibre pathology (SFP) in its pathophysiology. The significance of the role of SFP in FMS remains unclear; however, recent evidence suggests degeneration and dysfunction of the peripheral nervous system, particularly small unmyelinated fibres, which may influence pathophysiology and underlying phenotype. Both skin biopsy and corneal confocal microscopy (CCM) have consistently demonstrated that ~ 50% of people with FMS have SFP. CCM, a non-invasive measure of small nerve fibres has detected small fibre loss, correlating with neuropathic pain descriptors. Additionally, quantitative sensory testing has shown abnormalities, primarily in pain pressure/mechanical pain thresholds. This narrative review provides a comprehensive understanding of the pathophysiological dimensions of FMS with a clear focus on small nerve fibres and the peripheral nervous system, offering a roadmap for future research.

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.

Exploring the value of a well-established conditioned pain modulation paradigm in women: a Translational Research in Pelvic Pain (TRiPP) study

Background

Conditioned pain modulation (CPM) is considered a human proxy for descending inhibitory pain pathways. However, there is wide variation in the CPM response described in the literature and ongoing debate about its utility.

Methods

Here we explored CPM in women with (n = 59) and without (n = 26) chronic pelvic pain (CPP), aiming to determine the magnitude of effect and factors influencing variability in the CPM response.

Results

Using a pressure pain threshold test stimulus and ischaemic pressure cuff conditioning stimulus (CS), we found no significant difference in the mean CPM effect between CPP and control participants. Using a robust statistical method (+/-2 standard error of measurement) to further investigate CPM, there was no significant difference in the proportion exhibiting inhibition between controls and CPP participants (X2  = 0.003, p = 0.96). Notably, only 23.1% of our healthy controls demonstrated a "true" CPM effect (n = 4 inhibitory, n = 2 facilitatory). Despite a rich data set, we were unable to identify any single questionnaire, clinical or psychophysical covariate correlating with the CPM effect.

Conclusions

Despite using one of the recommended CPM paradigms we were only able to demonstrate "true" CPM in 23.1% of control participants. Thus, the absence of differences between women with and without chronic pelvic pain must be interpreted with caution. Future studies using different CPM paradigms or larger sample sizes may find different results. Although CPM in chronic pain populations is of major theoretical mechanistic interest, the lack of an established assessment standard led us to question its added value in current clinical research.

Effectiveness of Virtual Reality for Pain Management in Musculoskeletal Disorders Across Anatomical Regions: A Systematic Review and Meta-Analysis

INTRODUCTION

The use of virtual reality (VR) in physiotherapy is expanding across various fields; however, while extensively researched in neurology, its application in musculoskeletal (MSK) disorders remains underexplored. This review aims to evaluate the effectiveness of VR in pain management across different anatomical regions.

MATERIALS AND METHODS

The research was conducted using the MEDLINE (via PubMed), Cochrane Library, Scopus, Web of Science, and Embase databases, including randomized controlled trials that evaluated the effectiveness of VR interventions, encompassing immersive VR, specialised non-immersive VR, and gaming platforms. The primary outcomes focused on pain reduction. Data were extracted from the included studies, and methodological quality was assessed using the Revised Cochrane risk-of-bias tool for Randomized Trials (RoB 2). A meta-analysis was conducted using both fixed- and random-effects models to synthesise the findings.

RESULTS

From 1265 records, 27 articles met the eligibility criteria, comprising a total of 1191 participants. Of these, 20 studies contributed data to the meta-analyses. Significant findings were observed for pain relief in the knee region (SMD = - 0.33; 95% CI: - 0.55 to - 0.10; I2 = 13%, p < 0.004), with particularly notable effects within the subgroup utilising specialised non-immersive VR (SMD = - 0.32; 95% CI: - 0.62 to - 0.03; I2 = 10%, p < 0.003). For other anatomical regions, the heterogeneity was substantial, limiting the strength of recommendations for these areas.

CONCLUSIONS

VR shows potential for managing pain in MSK disorders, particularly knee conditions, with significant effectiveness using specialised non-immersive VR. However, high heterogeneity across other regions limits broader recommendations.

Prescription time trends in patients with high-impact chronic pain: A National Patient Registry Study

BACKGROUND

High-impact chronic pain (HICP), defined as chronic pain with a significant impact on daily function, affects approximately 8% of the Western population. In Denmark, HICP still remains to be described at the population level. Some patients with HICP are referred to the Danish pain centres, where they are registered with a procedural code. We conducted a nationwide registry-based study of all Danish patients registered with a visit to a pain centre from January 2005 to March 2022, to explore time trends in the prescription of analgesics and sedatives in this HICP subpopulation. Furthermore, data on socioeconomics and hospital diagnoses are reported.

METHODS

We used data from the Central Person Registry, the Danish National Patient Registry, the Danish National Prescription Registry, combined with data on socioeconomic information from Statistics Denmark. Data was collected on prescriptions 3 months before the first visit to a pain centre. Prescriptions were stratified into five calendar periods: before 2011, 2011-2013, 2014-2016, 2017-2019, and 2020-2022.

RESULTS

We identified 66,577 patients referred to a pain centre. Over 15 years, prescriptions before referral declined for opioids (from 53.2% to 31.7%), NSAIDs (from 28.3% to 23.5%), antidepressants (from 20.5% to 16.8%), anxiolytics (from 12.3% to 3.2%), and sleep medication (from 15.8% to 7.6%). In contrast, prescriptions increased for paracetamol (from 31.1% to 48.9%) and gabapentinoids (from 19.2% to 27.7%).

CONCLUSIONS

In patients with HICP visiting Danish pain centres, prescriptions before referral decreased for opioids over 15 years, with a simultaneously increased prescription of gabapentinoids (gabapentin and pregabalin).

SIGNIFICANCE STATEMENT

This nationwide study of 66,577 Danish patients with high-impact chronic pain reveals a significant decrease in filled opioid prescriptions over the past 15 years, with a simultaneous rise in gabapentinoid use before referral to pain centres. These findings suggest a shift in clinical practice towards alternative pain management strategies. The study underscores the need for continued research into the long-term effects of these changes and their impact on patient outcomes.

The medico-legal pertinence of musculoskeletal nociplastic pain

Pain conditions can be challenging; nociplastic pain, defined as pain that cannot be sufficiently explained by structural/anatomical changes, is newly categorised as the third pain mechanism. Nociplastic pain complaints are subjective, often accompanied by symptoms of fatigue, sleep and mood disturbance and cognitive difficulties with no diagnostic biomarker or reliable measurement of severity. Medico-legal challenges include attribution of causation after an alleged triggering event, assessment of severity, and reported functional impairment. This review considers nociplastic pain in regard to the musculoskeletal system with focus on causation and temporality of the pain condition and impairment. We hope that this overview will provide a better understanding of these challenging pain conditions.

The Effectiveness of Tramadol in Pain Relief in Chronic Diseases: A Review Based on Clinical Trials

Tramadol is a synthetic opioid with a central effect from the aminocyclohexanol group, which has two main mechanisms of action, including as a weak agonist of opioid receptors and as a norepinephrine and serotonin reuptake inhibitor. The present study presents a review based on clinical trials designed in 2023. In July 2023, six international databases, including Medline/PubMed, ProQuest, Scopus, EMBASE, Google Scholar, and ISI (Web of Science), were searched and 58 articles were included in the study. The results of most studies showed that tramadol can be used as an analgesic drug, although in some studies it was shown that tramadol is not therapeutically superior in reducing pain compared to other treatments. Also, complications related to this treatment have been reported in some studies. Physicians should consider these factors to prevent drug toxicity, poor pain relief, use disorder in patients, and unpredictable complications. It should be noted that there is not enough evidence to support the long-term effectiveness of tramadol, but this argument also extends to nonopioid and other types of opioid analgesics, and the lack of long-term trials is due to regulatory and ethical issues. Although opioids can cause addiction when used for a long time, tramadol has a reasonable safety profile. According to the patient's condition and the clinical judgment of the medical professional, tramadol can be prescribed for patients, but the consequences of its use must be considered and a personalized treatment algorithm should be selected if the benefits outweigh the risks of the drug.

Innovative therapeutic strategies using ADHD medications tailored to the behavioral characteristics of patients with chronic pain

Chronic pain affects a significant portion of adults and is linked to psychosocial issues, cognitive dysfunction, and psychiatric disorders, complicating treatment. Attention deficit hyperactivity disorder (ADHD) is increasingly recognized as a contributing factor to chronic pain, particularly nociplastic pain, with a notable prevalence of comorbidity between ADHD and conditions like fibromyalgia and chronic low back pain. ADHD behaviors such as impulsivity and overactivity can exacerbate pain by leading patients to seek risky treatments or discontinue care prematurely. ADHD medications are expected to alleviate pain severity by improving associated cognitive dysfunction and addressing central sensitization, a fundamental mechanism in chronic pain. Brain abnormalities in ADHD contribute to increased spontaneous activity in the anterior cingulate cortex-posterior insular pathway due to neuroinflammation, alterations in action potential firing, and changes in transmission pathways in the spinal dorsal horn. Additionally, increased norepinephrine synthesis and reduced transmission efficiency amplify nociceptive information from the periphery and facilitate central sensitization in ADHD. Beyond typical ADHD medications like central stimulants, norepinephrine reuptake inhibitors, and alpha-2 receptor agonists, various antidepressants, mood stabilizers, antipsychotics, Parkinson's disease medications, and antidementia medications have proven effective in alleviating ADHD symptoms. These medications, effective for ADHD, may offer innovative solutions for managing chronic pain by targeting both the cognitive/behavioral dysfunction and central sensitization observed in chronic pain comorbid with ADHD. Further research into these mechanisms could lead to new, more effective pharmacological treatments for chronic pain with comorbid ADHD, a condition that is often overlooked.

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.

[Treatment of cancer-related pain-From pharmacotherapy to invasive procedures]

Depending on the stage of the tumor up to 80% of the patients suffer from cancer-related pain but treatment is often inadequate. Multiple causes can trigger pain and these can be due to the tumor itself, its secondary consequences but also treatment related. A differentiated assessment and individually tailored treatment of cancer-related pain not only improve the quality of life but also reduce the risk of pain chronification. A differentiation between nociceptive pain and pain caused by hypersensitivity is a mandatory requirement for adequate pharmacotherapy. There is a risk of inadequate pain control, particularly with a lack of consideration and treatment of hypersensitivity, e.g., with anticonvulsants or analgesic antidepressants. Opioids are an integral part of drug treatment for cancer-related pain and especially for the treatment of breakthrough cancer pain. The risk of abuse should be considered. Other substance groups are suitable for special pain situations or in cases refractory to treatment. Nonpharmacological treatment options should also be considered, in particular by offering low-threshold access to psychotherapeutic or psycho-oncological options. Invasive procedures can be a useful supplement. These range from patient-controlled subcutaneous or intravenous infusion pump systems and intrathecal drug administration up to neurolytic and ablative procedures. Due to the invasiveness of these procedures, an interdisciplinary approach is recommended to confirm the indications.

Which Patients With Chronic Pain Do The Primary Care Refers to a Tertiary Hospital in a Developing Country? Experience From a University Hospital

PURPOSE

The study aimed to profile patients with uncontrolled chronic pain referred from primary care to a tertiary hospital in a developing country, and identify factors associated with pain intensity, interference, and its link with mental health.

DESIGN

Cross-sectional design.

METHODS

Data from 906 adult patients with nonmalignant chronic pain during their first visit to the multidisciplinary pain center at the State University of Rio de Janeiro in 2019 were used. The brief pain inventory and the Hospital Anxiety and Depression Scale questionnaire assessed pain intensity, its impact on daily activity, and symptoms of anxiety and depression.

RESULTS

The population was predominantly female (68.8%), over 50 (66.3%), with less than 11 years of education (86.5%), and 75.2% were overweight or obese. Most (81.9%) reported moderate or severe pain, significantly interfering with daily activities (>50%). The lower back was the most commonly affected site. Widespread pain was present in 43.6% of patients. High scores for anxiety (67.4%) and depression (52.2%) were observed. Severe pain was predominantly seen in middle-aged women and individuals with high levels of anxiety and depression.

CONCLUSION

Patients with uncontrolled chronic pain referred from primary care to a tertiary hospital were predominantly female, overweight or obese, and exhibited a high prevalence of depression and anxiety. Their pain significantly interfered with daily activities.

CLINICAL IMPLICATIONS

The study provides valuable insight into the biopsychosocial characteristics of uncontrolled chronic pain patients in primary care, emphasizing the importance of implementing multidisciplinary approaches to manage chronic pain effectively within primary care settings.

Do cytokines play a role in the transition from acute to chronic musculoskeletal pain?

Musculoskeletal pain has a high prevalence of transition to chronic pain and/or persistence as chronic pain for years or even a lifetime. Possible mechanisms for the development of such pain states are often reflected in inflammatory or neuropathic processes involving, among others, cytokines and other molecules. Since biologics such as blockers of TNF or IL-6 can attenuate inflammation and pain in a subset of patients with rheumatoid arthritis, the question arises to what extent cytokines are involved in the generation of pain in human musculoskeletal diseases. In numerous experimental non-human studies, cytokines have been shown to alter neuronal sensitivity in the peripheral and central nociceptive systems. In this review, we addressed the involvement of cytokines in postoperative pain, complex regional pain syndrome, rheumatoid arthritis, osteoarthritis, temporomandibular joint disease, low back pain and fibromyalgia using PubMed searches including meta-analyses of data. There is evidence that certain pro- and anti-inflammatory cytokines are regulated in all of these diseases, often in both acute and chronic disease states. However, within these data, we found a great deal of heterogeneity in the association between cytokine levels and pain. Neutralization of cytokines showed antinociceptive effects in subgroups of patients with chronic pain (e.g., in a proportion of patients with rheumatoid arthritis), but failed to reduce chronic pain in other diseases (e.g., osteoarthritis). More systematic studies are needed to unravel the pathogenic role of cytokines in human musculoskeletal pain, taking into account the disease process and the mechanisms of pain initiation and maintenance.

Sensory profiles and their role in the persistence of central sensitization symptoms in low back pain. A prospective cohort study

INTRODUCTION

Acute lower back pain can lead to neuroplastic changes in the central nervous system, and symptoms of central sensitization after 12 weeks. While sensory sensitivity has been shown to predict symptoms of central sensitization, trait sensory profiles may be prognostic in the persistence of central sensitization symptoms in low back pain over time.

OBJECTIVE

To examine sensory profiles as prognostic symptoms of central sensitization in people with acute low back pain.

METHODS

A longitudinal type 2 prognostic factor research study was performed according to the PROGRESS framework. Baseline and 12-week follow-up measures were taken using the Adolescent/Adult Sensory Profile and the Central Sensitization Inventory measures. Study participants were consecutively included from primary care physiotherapy practices. Univariable, and multivariable regression analyses were performed to adjust sensory profiles based on previous history of low back pain, baseline Central Sensitization Inventory scores, level of pain, disability, age, and duration of low back pain.

RESULTS

After adjustment, the sensory profiles of Low Registration B = 0.44, 95%CI (0.18, 0.70), Sensation Seeking B = 0.38, 95%CI (0.19, 0.57), Sensory Sensitive B = 0.49, 95%CI (0.25, 0.74), Sensation Avoiding B = 0.40, 95% CI (0.15, 0.65) was significantly associated with the persistence of central sensitization symptoms (N = 103).

CONCLUSION

Sensory profiles may predict symptoms of central sensitization after 12 weeks in people with acute low back pain.

Nociplastic pain in axial spondyloarthritis and psoriatic arthritis: role of JAK kinases in immunopathology and therapeutic impact of JAK inhibitors

INTRODUCTION

Pain in both peripheral and axial joints is a major symptom in patients with psoriatic arthritis (PsA) and axial spondyloarthritis (axSpA). Emerging evidence demonstrates pain mechanisms, beyond those related to inflammation or joint damage, based on aberrant processing of nociceptive stimuli peripherally as well as centrally. The Janus kinase/signal transducers and activators of transcription (JAK-STAT) signaling pathway has been implicated in the processing of pain beyond its role in mediating inflammation and inhibitors of this pathway approved for the treatment of axSpA and PsA have been shown to alleviate a broad array of pain outcomes in both axial and peripheral joints.

AREAS COVERED

We review recent definitions and standardization of the nomenclature for categorizing chronic pain according to causality, assessment tools to evaluate nociplastic pain, the pathophysiologic role of JAK-STAT signaling in nociplastic pain, evidence for the presence of nociplastic pain in axSpA and PsA, and the impact of JAK inhibitors (JAKi) on pain outcomes in clinical trials (PubMed: 01/01/2019-04/01-2024).

EXPERT OPINION

Nociplastic pain assessment has been confined almost entirely to the use of a limited number of questionnaires in cross-sectional studies of these diseases. Though effective for alleviating pain, it is unclear if JAKi specifically impact nociplastic pain.

Rehabilitation Management of Neck Pain-Development of a Diagnostic Framework Based on the Pain and Disability Drivers Management Model

RATIONALE

Neck pain is a major cause of disability worldwide, and current rehabilitation strategies show limited effectiveness. Subgrouping patients by their primary pain and disability drivers can help tailor treatments. At this end, the Pain and Disability Drivers Management (PDDM) was developed and has demonstrated preliminary effectiveness in the management of low back pain. Nevertheless, the PDDM model was only validated for this population. Adapting this framework to patients with neck pain would provide a more global view of the patient's experience of pain and support a genuine biopsychosocial intervention.

AIMS AND OBJECTIVES

The aim of this study was to develop and validate the content of the PDDM model for patients living with neck pain.

METHODS

Through a modified DELPHI study design, participants with clinical and research expertize in rehabilitation of neck pain were invited to participate. A questionnaire was developed using literature reviews and endorsed by a steering committee. The relevance of each element of the newly adapted model was evaluated on a 4-point Likert scale. An item reached consensus if it obtained the predefined threshold of > 78% "relevant" and "very relevant." Participants left comments on terminology and recommended items to add in early rounds. Quantitative and qualitative analyses were performed.

RESULTS

An invitation was sent to 1650 potential participants, from which 155 accessed the survey, 64 completed the first round and 55 the second round. A total of 70 elements met consensus and were distributed across six domains: "Nociceptive pain drivers", "nociplastic pain drivers," "drivers associated with neuropathic pain", "comorbidity drivers", "cognitive-emotional drivers" and "environmental or lifestyle drivers, and social determinants of health."

CONCLUSION

Through a modified DELPHI study, the PDDM model was updated and adapted to people with neck pain. Subsequent steps include clinical integration and measures of efficacy when used for assessment/treatment.

ADvAnced PhysioTherapy in MuSculosKeletal Triage: Investigating prognostic factors, healthcare utilisation and clinical outcomes (ADAPT MSK) - a cohort study protocol

Background

Clinical specialist physiotherapist-led musculoskeletal triage clinics were introduced nationally in Ireland in 2011 to improve patient care and reduce waiting times for secondary care orthopaedics and rheumatology. Evidence has shown them to be effective in reducing waiting lists, however there are currently no data on longitudinal patient outcomes following attendance at these clinics. The primary aim of this prospective, cohort study is to identify predictors of clinical outcome (pain and function) at 12-months post MSK-triage appointment. Secondary aims are to describe the clinical course of patients attending MSK triage clinics and measure self-reported use of healthcare resources up to 12 months post-MSK-triage appointment. This is a prospective cohort study.

Methods

ADvAnced PhysioTherapy in MuSculosKeletal Triage (ADAPT MSK) will recruit a cohort of 252 adults through musculoskeletal triage clinics across five secondary care sites in Ireland. The STrengthening the Reporting of Observational studies in Epidemiology (STROBE) guidelines will be adhered to for future reporting. Adults (≥ 18 years old) attending physiotherapist-led musculoskeletal triage clinics with musculoskeletal pain, who do not require surgical or consultant-led medical care will be considered for participation in this study. Participant demographics, health literacy, healthcare utilisation, and self-report questionnaires on pain, function, musculoskeletal health status, musculoskeletal risk stratification, fear of movement, and psychological distress will be obtained at baseline, with follow-ups at three, six, and 12 months. The primary outcomes are pain intensity and function. Secondary outcomes include musculoskeletal risk stratification status, musculoskeletal health status, healthcare utilisation, and work status. Descriptive statistics will be used to profile the cohort of participants and predictors of outcome will be assessed using multivariable linear regression.

Results

Results will be disseminated via peer-reviewed journal publication and presentation at national and international conferences. Engagement with a public patient involvement (PPI) panel will explore dissemination strategies for public and service user engagement.

Chronic overlapping pain conditions and nociplastic pain

Chronic overlapping pain conditions (COPCs) are a subset of chronic pain conditions commonly comorbid with one another and more prevalent in women and individuals assigned female at birth (AFAB). Pain experience in these conditions may better fit with a new mechanistic pain descriptor, nociplastic pain, and nociplastic pain may represent a shared underlying factor among COPCs. We applied GenomicSEM common-factor genome-wide association study (GWAS) and multivariate transcriptome-wide association (TWAS) analyses to existing GWAS output for six COPCs in order to find genetic variation associated with nociplastic pain, followed by genetic correlation (linkage disequilibrium score regression), gene set, and tissue enrichment analyses. We found 24 independent single nucleotide polymorphisms (SNPs), and 127 unique genes significantly associated with nociplastic pain, and showed nociplastic pain to be a polygenic trait with significant SNP heritability. We found significant genetic overlap between multisite chronic pain and nociplastic pain, and to a smaller extent with rheumatoid arthritis and a neuropathic pain phenotype. Tissue enrichment analyses highlighted cardiac and thyroid tissue, and gene set enrichment analyses emphasized potential shared mechanisms in cognitive, personality, and metabolic traits and nociplastic pain along with distinct pathology in migraine and headache. We used a well-powered network approach to investigate nociplastic pain using existing COPC GWAS output, and show nociplastic pain to be a complex, heritable trait, in addition to contributing to understanding of potential mechanisms in development of nociplastic pain.

Pain and the perception of space in fibromyalgia

The Economy of action hypothesis postulates that bodily states rescale the perception of the individual's environment's spatial layout. The estimation of distances and slopes in navigation space (i.e. the space reachable by locomotion) is influenced by sensations relating to body condition and the metabolic cost of the actions. The results of the studies investigating the impact of pain on distance estimation remain inconclusive. 28 women suffering from chronic pain and fibromyalgia (FM), and 24 healthy women (HC) were assessed for musculoskeletal, neuropathic, and visceral pain by means of the Widespread Pain Index, the Symptom Severity Scale and an ad-hoc devised questionnaire for pain (the Verona Pain Questionnaire). In a VR-mediated task, they observed a 3D scenario and estimated the distance of a flag positioned at different distances (1, 2, 3, 4 or 5 m) on virtual ramps with either a 4% or 24% inclination in two different conditions: sitting and standing. Overestimation of distances in the steeper ramp condition was expected, if participants executed the task by internally simulating the movement. The results showed a dissociation between the effects of musculoskeletal and visceral-neuropathic pain on distance estimations. While, according to the Economy of Action hypothesis, the HCs estimated the distances as being farther away when the ramp was more inclined (i.e. with a 24% inclination), there was no effect related to the different ramp inclinations in the FM group. Furthermore, visceral and neuropathic pain were found to affect the performance of the FM group. These results suggest that chronic and widespread pain conditions, that typically characterize fibromyalgia, can affect space representations. In line with the Economy of Action hypothesis, bodily based estimation of distances is compromised in these patients.

Nociplastic pain: controversy of the concept

Classically, pain can be of a nociceptive or neuropathic nature, which refers to non-neural or neural tissue lesions, respectively. Chronic pain in conditions such as migraine, fibromyalgia, and complex regional pain syndrome (CRPS), is thought to perpetuate without a noxious input. Pain in such patients can be assigned neither to the nociceptive nor neuropathic category. Therefore, a third pain descriptor, named "nociplastic pain", has been adopted by the International Association for the Study of Pain. The current controversy-focused narrative review updates littledebated aspects of the new pain concept. The most disputable feature of nociplastic pain is its autonomous persistence, i.e., existence without causative tissue damage, presumably because of a malfunction of pain pathways and processing. This contradicts the fact that nociplastic pain is accompanied by persistent central sensitization that has been shown to require a continuing noxious input, e.g ., nerve injury. Even if sensitization occurs without a lesion, e.g ., in psychogenic and emotional pain, peripheral stimulus is necessary to produce pain. A logical weakness of the concept is that the word "plastic" in biology refers to adaptation rather than to maladaptation. The pathophysiologic mechanism of nociplastic pain may, in fact, be associated with background conditions that elude diagnosis because of the limitations of current diagnostic means. Misapplication of the nociplastic pain category may weaken diagnostic alertness toward occult causes of pain. Possible diagnostic errors could be avoided by understanding that nociplastic pain is a mechanism of pain rather than a diagnosis. Clinical use of this pain descriptor deserves a wider critical discussion.

The role of environmental sensitivity, traumatic experiences, defense mechanisms and mental pain on central sensitivity: testing a path analysis model in chronic headache on quality of life

Central pain sensitivity (CS) is defined as an increased responsiveness of nociceptive neurons in the central nervous system to normal or subthreshold inputs. The main aim of this paper is to investigate if and how specific psychological constructs are related with CS burden in patients with chronic headache (CH). Specifically, research question 1 explores the association of temperament, personality, childhood adversities, defense mechanisms and mental pain with CS burden. Research question 2 aims to test the role of the best predictors of CS burden in affecting the quality of life (QoL) using path analysis. A total of 508 women with CH completed a psycho-diagnostic survey. Results showed that higher levels of low sensory threshold (β = 0.200), bodily threat traumatic experiences (β = 0.156), neurotic defenses (β = 0.109) and mental pain (β = 0.343) emerged as the best predictors of higher CS burden. The model presented demonstrated a satisfactory fit (GFI = 0.984; NFI = 0.966; CFI = 0.979; RMSEA = 0.056 [95% CI 0.028-0.085]) with large and medium effect sizes on physical (-0.654) and psychological QoL (-0.246). The study showed a key role of psychological dimensions in CS burden levels and their relationships with QoL in CH patients. From a clinical perspective, these results suggest the importance of evaluating the level of CS burden during the clinical assessment for chronic pain conditions such as CH, since it may contribute to guide patients to tailored psychological and medical treatments, thereby saving time and costs on diagnostic procedures for chronic pain.

Application of the grading system for "nociplastic pain" in chronic primary and chronic secondary pain conditions: a field study

ABSTRACT

The concept "nociplastic pain" has been developed for patients with features of nociceptive system sensitization that are not explained as nociceptive or neuropathic. Here, we tested how well the recently published grading system differentiates between chronic primary and secondary pain conditions. We recruited patients with fibromyalgia (FMS, n = 41), complex regional pain syndrome (CRPS, n = 11), osteoarthritis (OA, n = 21), or peripheral nerve injury (PNI, n = 8). We used clinical history, pain drawings, quantitative sensory testing (QST), and questionnaires to classify their pains as possibly or probably "nociplastic." All patients with chronic primary pain exhibited widespread/regional pain not explainable by either nociceptive or neuropathic mechanisms. Widespread pain occurred in 12 patients with OA but was identified as nociceptive in 11 of 12. Regional pain occurred in 4 patients with PNI but was identified as neuropathic in 3 of 4. At this step, the grading system had 100% sensitivity and 93% specificity. Clinical evidence for pain hypersensitivity by QST, and history of hypersensitivity and mental comorbidities did not differentiate between chronic primary pain (QST: 36/52 = 69%, history: 43/52 = 83%) and secondary pain conditions (QST: 20/29 = 69%, history: 24/29 83%). Based on these data, specificity remained excellent (93%), but sensitivity dropped substantially (60%) due to lacking evidence for pain hypersensitivity in many patients with FMS. This low sensitivity suggests that the published grading system is not suitable for screening purposes. We suggest structural and content modifications to improve sensitivity, including placement of patient history before clinical examination and addition of a high tender point count as evidence for widespread pain hypersensitivity.

An exploratory data-driven approach to classify subgroups of patients with temporomandibular disorders based on pain mechanisms

Temporomandibular disorders (TMDs) are a common musculoskeletal condition, presenting treatment challenges due to their non-specific nature. Categorizing patients with TMDs into clusters based on neurobiological pain mechanisms could provide a promising approach to facilitate targeted treatments. This observational study (1) used a network analysis (NA) to explore the complexity of TMDs by investigating relationships among biopsychosocial variables, and (2) validated potential TMD subgroups based on mechanism-specific pain categories. One hundred and two patients with TMD were included. Biopsychosocial variables covered: general health, psychosocial features, TMD pain, and TMD characteristics. A NA evaluated the associations between variables and determined the role of each feature within the network. Hierarchical clustering was used to identify TMD subgroups. The NA revealed significant correlations primarily within the same feature domains, indicating a strong interplay between symptoms and psychological factors. Cluster analysis identified two subgroups driven by nociceptive and nociplastic pain mechanisms; the nociplastic group exhibited higher levels of anxiety, depression, pain catastrophization, central sensitization, pain duration, and more pain locations, along with poorer sleep quality, quality of life, and health status. In contrast, the nociceptive group exhibited restricted maximal mouth opening (MMO), heightened pain during TMJ palpation and mouth opening, and a greater positive response to manual therapy. Across all features, psychological factors, pain locations, and MMO primarily contributed to the separation of subgroups. By adopting a data-driven approach, these results support the significant role of considering the neurobiological basis of pain to improve patient classification. This knowledge may facilitate clinical reasoning and personalized treatments. PERSPECTIVE: This study used a network analysis to explore the complex biopsychosocial interactions present in people with TMDs, identifying important variables such as the Central Sensitization Inventory and pain-free maximal mouth opening. The findings distinguish potential nociceptive and nociplastic pain subgroups, offering important insights for targeted therapeutic strategies.

Development of a comprehensive clinical assessment protocol for low back and hip pain in powerlifters: a feasibility study

BACKGROUND

Low back and hip pain problems are frequent in powerlifting. There is a lack of information on the specific pain phenotypes and specific impairments in body function associated with these pain problems, as well as how to reach a clinical diagnosis relevant for powerlifters' pain problems. Therefore, the aim was to develop a comprehensive clinical assessment protocol for pain and function in powerlifters with low back and/or hip pain and evaluate its feasibility for use in further epidemiological or clinical studies of powerlifters.

METHODS

The study was conducted in two phases. In phase one, the protocol was developed according to literature regarding musculoskeletal assessment and sports injuries, and in phase two, feasibility was evaluated. Eight powerlifters with low back/hip pain were included in phase two. Four of them were examined independently by two physical therapists, and the other four were examined by one of the physical therapists. The time spent on the examination, whether the physical therapists could reach a clinical diagnosis without adding items to the protocol, and whether the two physical therapists were consistent in terms of the clinical diagnosis, were evaluated.

RESULTS

The protocol was developed including subjective examination, physical examination, and a clinical diagnosis based mainly on signs and symptoms of associated neurophysiological pain mechanisms and the specific impairments in body functions associated with the powerlifter's pain problem. The protocol met the feasibility criteria. The examination lasted approximately 1 h, no items needed to be added, and both physical therapists were able to make a consistent clinical diagnosis. Visual observation and alteration of movement strategy of the squat/deadlift were thought to be crucial for assessing the powerlifters' pain problem.

CONCLUSIONS

This is the first comprehensive clinical assessment protocol developed to describe powerlifters' pain problems/injuries with a clinical diagnosis based on the dominating neurophysiological pain mechanism and impairments in body functions. However, before use in larger studies, it is recommended that the protocol be further evaluated by a larger number of physical therapists and powerlifters to evaluate its reliability and whether the content of the protocol should be further expanded.

Nociplastic Pain in Endometriosis: A Scoping Review

Endometriosis is an inflammatory chronic condition associated with nociceptive, neuropathic, and nociplastic pain. Central sensitization (CS) is the primary nociplastic pain mechanism. However, there are currently no standardized methods for detecting CS or nociplastic pain. This review aims to identify available tools for characterizing CS/nociplastic pain in endometriosis-related chronic pelvic pain. Following the PRISMA-P protocol, MEDLINE, Embase, Scopus, and PsychINFO databases were searched on 23 April 2024, for the terms "endometriosis", "central sensitization", "nociplastic pain", "widespread pain", and "assessment tools". Publications were selected if they mentioned tool(s) for detecting nociplastic pain or CS in endometriosis patients. Information was extracted on study demographics, assessment types, and the tools used for detection. Of the 379 citations retrieved, 30 papers met the inclusion criteria. When working to identify CS and nociplastic pain, fourteen studies exclusively used patient-reported questionnaires, six used quantitative sensory testing (QST), two used clinical assessments, and eight used multiple approaches combining patient-reported questionnaires and clinical assessment. This review illustrates the diversity of tools currently used to identify CS and nociplastic pain in endometriosis patients. Further research is needed to evaluate their validity and to standardize methods in order to improve the accuracy of nociplastic pain identification and guide treatment.

Validation of a questionnaire for central nervous system aspects of joint pain: the CAP questionnaire

BACKGROUND

Neuropathic-like pain, fatigue, cognitive difficulty, catastrophizing, anxiety, sleep disturbance, depression and widespread pain associate with a single factor in people with knee pain. We report the Central Aspects of Pain questionnaire (CAP) to characterize this across painful musculoskeletal conditions.

METHODS

CAP was derived from the 8-item CAP-Knee questionnaire, and completed by participants with joint pain in the Investigating Musculoskeletal Health and Wellbeing survey. Subgroups had OA, back pain or FM. Acceptability was evaluated by feedback and data missingness. Correlation coefficients informed widespread pain scoring threshold in relation to the other items, and evaluated associations with pain. Factor analysis assessed CAP structure. Intraclass Correlation Coefficient (ICC) between paper and electronic administration assessed reliability. Friedman test assessed score stability over 4 years in people reporting knee OA.

RESULTS

Data were from 3579 participants (58% female, median age 71 years), including subgroups with OA (n = 1158), back pain (n = 1292) or FM (n = 177). Across the three subgroups, ≥10/26 painful sites on the manikin scored widespread pain. Reliability was high [ICC = 0.89 (95% CI 0.84-0.92)] and CAP scores fit to one- and two-factor model, with a total CAP score that was associated with pain severity and quality (r = 0.50-0.72). In people with knee pain, CAP scores were stable over 4 years at the group level, but displayed significant temporal heterogeneity within individual participants.

CONCLUSIONS

Central aspects of pain are reliably measured by the CAP questionnaire across a range of painful musculoskeletal conditions, and is a changeable state.

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.

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.

The concept of nociplastic pain-where to from here?

ABSTRACT

Nociplastic pain, a third mechanistic pain descriptor in addition to nociceptive and neuropathic pain, was adopted in 2017 by the International Association for the Study of Pain (IASP). It is defined as "pain that arises from altered nociception" not fully explained by nociceptive or neuropathic pain mechanisms. Peripheral and/or central sensitization, manifesting as allodynia and hyperalgesia, is typically present, although not specific for nociplastic pain. Criteria for possible nociplastic pain manifesting in the musculoskeletal system define a minimum of 4 conditions: (1) pain duration of more than 3 months; (2) regional, multifocal or widespread rather than discrete distribution of pain; (3) pain cannot entirely be explained by nociceptive or neuropathic mechanisms; and (4) clinical signs of pain hypersensitivity present in the region of pain. Educational endeavors and field testing of criteria are needed. Pharmacological treatment guidelines, based on the three pain types, need to be developed. Currently pharmacological treatments of nociplastic pain resemble those of neuropathic; however, opioids should be avoided. A major challenge is to unravel pathophysiological mechanisms driving altered nociception in patients suffering from nociplastic pain. Examples from fibromyalgia would include pathophysiology of the peripheral as well as central nervous system, such as autoreactive antibodies acting at the level of the dorsal root ganglia and aberrant cerebral pain processing, including altered brain network architecture. Understanding pathophysiological mechanisms and their interactions is a prerequisite for the development of diagnostic tests allowing for individualized treatments and development of new strategies for prevention and treatment.

"Neuroinflammation": does it have a role in chronic pain? Evidence from human imaging

ABSTRACT

Despite hundreds of studies demonstrating the involvement of neuron-glia-immune interactions in the establishment and/or maintenance of persistent pain behaviors in animals, the role (or even occurrence) of so-called "neuroinflammation" in human pain has been an object of contention for decades. Here, I present the results of multiple positron emission tomography (PET) studies measuring the levels of the 18 kDa translocator protein (TSPO), a putative neuroimmune marker, in individuals with various pain conditions. Overall, these studies suggest that brain TSPO PET signal: (1) is elevated, compared to healthy volunteers, in individuals with chronic low back pain (with additional elevations in spinal cord and neuroforamina), fibromyalgia, migraine and other conditions characterized by persistent pain; (2) has a spatial distribution exhibiting a degree of disorder specificity; (3) is parametrically linked to pain characteristics or comorbid symptoms (eg, nociplastic pain, fatigue, depression), as well as measures of brain function (ie, functional connectivity), in a regionally-specific manner. In this narrative, I also discuss important caveats to consider in the interpretation of this work (eg, regarding the cellular source of the signal and the complexities inherent in its acquisition and analysis). While the biological and clinical significance of these findings awaits further work, this emerging preclinical literature supports a role of neuron-glia-immune interactions as possible pathophysiological underpinnings of human chronic pain. Gaining a deeper understanding of the role of neuroimmune function in human pain would likely have important practical implications, possibly paving the way for novel interventions.

Bruxism, temporomandibular disorders, and headache: a narrative review of correlations and causalities

ABSTRACT

The co-occurrence of bruxism, temporomandibular disorders (TMDs), and headache is common in patients. However, there is conflicting evidence regarding whether this association is simply a result of their high prevalence or whether there are indeed causal relationships. This review provides an overview of the current state of research while taking into account the controversies surrounding research methods, particularly in definitions and diagnostic standards. Bruxism-defined as repetitive jaw muscle activity during sleep or wakefulness-is not a painful disorder but may-particularly in co-occurrence with TMD-worsen pre-existing headache. It seems important to differentiate between sleep and awake bruxism because of different impact on pathophysiological processes in different primary headache disorders such as migraine and tension-type headache. Temporomandibular disorder is a heterogenous entity with both myofascial and arthrogenous types of pain in addition to nonpainful disorders. Research suggests a correlation between TMD pain and migraine, as well as between awake bruxism and tension-type headache. However, psychosocial factors may act as confounders in these relationships. Determining causality is challenging because of the limited number of experimental and clinical studies conducted on this topic. The main finding is an apparent lack of consensus on the definition and assessment criteria for bruxism. Treatment wise, it is important to differentiate all 3 conditions because treatment of one condition may have an effect on the other 2 without proving causality. For future research, it is crucial to establish greater consistency and applicability in diagnostic procedures and definitions. In addition, more experimental and clinical studies investigating the question of causality are needed.