Nociplastic Pain Criteria or Recognition of Central Sensitization? Pain Phenotyping in the Past, Present and Future

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 IASP Grading System to Identify Underlying Pain Mechanisms in Patients With Knee Osteoarthritis: A Prospective Cohort Study

OBJECTIVES

This study aimed to apply the International Association for the Study of Pain (IASP) grading system for identifying nociplastic pain in knee osteoarthritis (KOA) awaiting total knee arthroplasty (TKA) and propose criteria to fine-tune decision-making. In addition, the study aimed to characterize a "probable" versus "no or possible" nociplastic pain mechanism using biopsychosocial variables and compare both groups in their 1-year post-TKA response.

METHODS

A secondary analysis of baseline data of a longitudinal prospective study involving 197 patients with KOA awaiting total TKA in Belgium and the Netherlands was performed. Two approaches, one considering 4 and the other 3 pain locations (step 2 of the grading system), were presented. Linear mixed model analyses were performed to compare the probable and no or possible nociplastic pain mechanism groups for several preoperative biopsychosocial-related variables and 1-year postoperative pain. Also, a sensitivity analysis, comparing 3 pain mechanism groups, was performed.

RESULTS

Thirty (15.22%-approach 4 pain locations) and 46 (23.35%-approach 3 pain locations) participants were categorized under probable nociplastic pain. Irrespective of the pain location approach or sensitivity analysis, the probable nociplastic pain group included more woman, was younger, exhibited worse results on various preoperative pain-related and psychological variables, and had more pain 1-year post-TKA compared with the other group.

DISCUSSION

This study proposed additional criteria to fine-tune the grading system for nociplastic pain (except for discrete/regional/multifocal/widespread pain) and characterized a subgroup of patients with KOA with probable nociplastic pain. Future research is warranted for further validation.

Predictors for severe persisting pain in rheumatoid arthritis are associated with pain origin and appraisal of pain

OBJECTIVES

To determine the proportion of patients with rheumatoid arthritis (RA) with severe persisting pain and to identify predictive factors despite treatment-controlled disease activity.

METHODS

This prospective multicentre study included outpatients with RA scheduled for escalation of anti-inflammatory treatment due to active disease and severe pain (Disease Activity Score 28 (DAS28)>3.2 and Visual Analogue Scale (VAS)>50). At week 24, patients were stratified into reference group (DAS28 improvement>1.2 or DAS28≤3.2 and VAS pain score<50), non-responders (DAS28 improvement≤1.2 and DAS28>3.2, regardless of VAS pain score) and persisting pain group (DAS28 improvement>1.2 or DAS28≤3.2 and VAS pain score≥50). The former two subgroups ended the study at week 24. The latter continued until week 48. Demographic data, DAS28-C reactive protein, VAS for pain, painDETECT Questionnaire (PD-Q) to identify neuropathic pain (NeP) and the Pain Catastrophising Scale were assessed and tested for relation to persisting pain.

RESULTS

Of 567 patients, 337 (59.4%) were classified as reference group, 102 (18.0%) as non-responders and 128 (22.6%) as patients with persisting pain. 21 (8.8%) responders, 28 (35.0%) non-responders and 27 (26.5%) persisting pain patients tested positive for NeP at week 24. Pain catastrophising (p=0.002) and number of tender joints (p=0.004) were positively associated with persisting pain at week 24. Baseline PD-Q was not related to subsequent persisting pain.

CONCLUSIONS

Persisting and non-nociceptive pain occur frequently in RA. Besides the potential involvement of NeP, pain catastrophising and a higher number of tender joints coincide with persisting pain.

Central sensitization symptoms in vulvodynia: exploring the role of temperament, personality traits, childhood adverse events, defense mechanisms, and mental pain on quality of life

BACKGROUND

Vulvodynia is a chronic pain syndrome characterized by persistent vulvar pain, occurring without clinically identifiable disorders. Central sensitization (CS) is suggested to play a role in the pathophysiology of vulvodynia, as for other nociplastic pain conditions.

AIM

This study delves into the complex interplay between psychosocial factors and CS burden in women with vulvodynia, aiming to identify potential predictors (temperament, personality traits, childhood adverse events, defense mechanisms, and mental pain) and understand their impact on quality of life (QoL).

METHODS

A cohort-based cross-sectional web survey of 357 women with vulvodynia.

OUTCOMES

Outcomes included 8 self-report measures to assess the Central Sensitization Inventory (CSI) and psychological variables, including sensory processing sensitivity, traumatic experiences, personality traits, defense mechanisms, and mental pain.

RESULTS

Hierarchical multiple regression analyses were conducted in study 1, revealing that the following predicted higher CSI scores in women with vulvodynia: higher emotional overexcitability, decreased low sensory threshold, increased bodily threat experiences, elevated psychoticism, greater use of immature and neurotic defense mechanisms, and heightened mental pain. The final regression model identified the following as the strongest predictors of CS: low sensory threshold (β = 0.316), bodily threat experiences (β = 0.145), neurotic defenses (β = 0.210), and mental pain (β = 0.269). In study 2, the model presented interactions among these psychological factors in predicting CSI values explaining 48.9% of the variance in CS, 30.3% in psychological QoL, and 57.1% in physical QoL.

CLINICAL TRANSLATION

This model opens discussion for tailored psychological interventions aimed to improve overall QoL in women with vulvodynia.

STRENGTHS AND LIMITATIONS

Strengths of the study include innovative insights into the interplay between psychological variables and the construct of CS and quality of life. As a limitation, the research was conducted as a cross-sectional study with self-reported measures.

CONCLUSION

The study calls for comprehensive assessments that consider physical and mental aspects, paving the way for holistic health care approaches in the management of vulvodynia.

Assessment of decision-making autonomy in chronic pain patients: a pilot study

BACKGROUND

Patient decision-making autonomy refers to the patients' ability to freely exert their own choices and make their own decisions, given sufficient resources and information to do so. In pain medicine, it is accepted that appropriate beneficial management aims to propose an individualized treatment plan shared with the patients, as agents, to help them live as autonomously as possible with their pain. However, are patients in chronic pain centers sufficiently autonomous to participate in the therapeutic decisions that concern them? As this question still remains unanswered, a pilot study was set up to that aim.

METHODS

Over a 2-month period, first-time patients within a tertiary multidisciplinary pain center underwent a systematic evaluation of their autonomy using the MacArthur Competence Assessment Tool for Treatment (MacCAT-T), considered the benchmark tool for measuring a patient's ability to consent to treatment. Demographic data and pain characteristics of the patients were collected and their respective attending pain physicians were asked to clinically assess their patients' degree of autonomy. Another physician, who had not participated in the initial patient evaluation, subsequently administered the MacCAT-T questionnaire to the same patients.

RESULTS

Twenty-seven patients were included during the study period (21 women and 6 men), with an average age of 50 years. The average duration of pain was 8 years. Based on their clinical experience, the 4 different pain physicians in charge of these patients considered that out of 25 assessed patients, 22 of them (89%) had full decision-making capacity, with no deficit in autonomy. According to the MacCAT-T results, only 13 of these 25 patients (48%) had no deficit, while 7 (26%) had a major deficit in autonomy. The only patient characteristic that appeared to be related to autonomy was pain type, specifically nociplastic pain. The average time taken to complete the test was 20 min, and patients were very satisfied with the interview.

CONCLUSION

Results from the present pilot study suggest that patients suffering from chronic pain do not appear to be entirely autonomous in their decision to consent to the proposed treatment plan according to the MacCAT-T questionnaire, and physicians seem to find it difficult to properly assess this competence in a clinical setting. Further studies with larger samples are needed to better evaluate this concept to improve the complex management of these patients.

Hip Fracture in the Sportive Adult: Case Report of Complete Functional Recovery After Removal of Hardware

CONTEXT

Pertrochanteric hip fractures in sportive young adults are mainly caused by a high-energy trauma and treated in the same way as in the older population, using an osteosynthesis immediately followed by a rehabilitation program for several months. The current standard is not to remove osteosynthesis material, similar to the case of older patients.

CASE PRESENTATION

A 45-year-old male cyclist experienced a right pertrochanteric femoral fracture, treated with cephalomedullary nails. After 9 months of adequate rehabilitation, weakness of the quadriceps musculature and functional complaints persisted, objectified through an isokinetic strength test and a significantly reduced score on the Hip Disability and Osteoarthritis Outcome Score questionnaire. The patient was unable to return to his previous level of cycling performance.

MANAGEMENT AND OUTCOME

After exclusion of structural bone complications, nerve injury, and central sensitization, the functional complaints and strength deficiency were hypothesized to be related to the osteosynthesis material. Therefore, the hardware was removed 9 months after the first surgery, and the rehabilitation was continued for another 20 weeks. Very soon after the removal of the hardware, the functional complaints disappeared with a remarkable improvement of the Hip Disability and Osteoarthritis Outcome Score. The isokinetic strength test showed complete recovery of muscle strength 20 weeks after osteosynthesis removal, and preinjury cycling performance values were obtained 9 months posthardware removal.

CONCLUSION

Despite an adequate rehabilitation following a hip fracture, sporty young adults may fail to reach their previous level of functioning. Osteosynthesis removal may be indicated in this sportive population to reach complete muscle strength and functional recovery. The management of hip fractures in the sportive young adult and the identification of patients who may benefit from removal of the hardware require more research.

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.

Impact of Central Sensitization on Clinical and Functional Aspects of Psoriatic Arthritis

Background/Objectives: Psoriatic arthritis (PsA) is an inflammatory rheumatic disease characterized by peripheral arthritis, enthesitis, spondylitis and psoriasis. The objective of this study was to examine the prevalence of central sensitization (CS) and its impact on the clinical and functional aspects of PsA. Methods: Adult patients with PsA according to the Classification of Psoriatic Arthritis (CASPAR) criteria were included in this cross-sectional observational study. The Central Sensitization Inventory (CSI) was used to assess the presence of CS. The study evaluated the impact of CS on individuals by analyzing many factors including demographic information, laboratory findings, clinical features, disease activity, quality of life, severity of sleeplessness, frequency of depression and anxiety. The patients were categorized into distinct groups based on the existence and intensity of CS, and a comparative analysis was conducted on their respective outcomes. Results: A total of 103 PsA patients with a mean age of 43.2 (SD: 6.7) years and including 42 (40.8%) males were included. The mean CSI score was 45.4 (SD: 15.1), and 67 (65.1%) patients had CS. The logistic regression analysis revealed that the variables Psoriasis Area Severity Index (PASI), General Anxiety Disorder-7 (GAD-7), and Insomnia Severity Index (ISI) exhibit considerable predictive power in relation to the outcome variable CS (p < 0.05). PASI was observed as the most important variable in predicting CS (OR 9.70 95% CI: 1.52-62.21). Conclusions: CS has demonstrable efficacy in influencing laboratory, clinical, and functional markers among individuals with PsA. When assessing pain sensitivity in these patients, it is important to take into account the presence of CS.

Quantitative sensory testing and chronic pain syndromes: a cross-sectional study from TwinsUK

OBJECTIVE

The chronic pain syndromes (CPS) include syndromes such as chronic widespread pain (CWP), dry eye disease (DED) and irritable bowel syndrome (IBS). Highly prevalent and lacking pathognomonic biomarkers, the CPS are known to cluster in individuals in part due to their genetic overlap, but patient diagnosis can be difficult. The success of quantitative sensory testing (QST) and inflammatory biomarkers as phenotyping tools in conditions such as painful neuropathies warrant their investigation in CPS. We aimed to examine whether individual QST modalities and candidate inflammatory markers were associated with CWP, DED or IBS in a large, highly phenotyped population sample.

DESIGN

Cross-sectional study.

SETTING

Community-dwelling cohort.

PARTICIPANTS

Twins from the TwinsUK cohort PRIMARY AND SECONDARY OUTCOME MEASURES: We compared 10 QST modalities, measured in participants with and without a CWP diagnosis between 2007 and 2012. We investigated whether inflammatory markers measured by Olink were associated with CWP, including interleukin-6 (IL-6), IL-8, IL-10, monocyte chemoattractant protein-1 and tumour necrosis factor. All analyses were repeated in DED and IBS with correction for multiple testing.

RESULTS

In N=3022 twins (95.8% women), no association was identified between individual QST modalities and CPS diagnoses (CWP, DED and IBS). Analyses of candidate inflammatory marker levels and CPS diagnoses in n=1368 twins also failed to meet statistical significance.

CONCLUSION

Our findings in a large population cohort suggest a lack of true association between singular QST modalities or candidate inflammatory markers and CPS.

Pain with orgasm in endometriosis: potential etiologic factors and clinical correlates

BACKGROUND

Pelvic pain worsened by orgasm is a poorly understood symptom in patients with endometriosis.

AIM

To assess the prevalence of pelvic pain worsened by orgasm in patients with endometriosis and explore its association with potential etiologic factors, including pelvic floor myalgia, uterine tenderness and adenomyosis, and central nervous system sensitization.

METHODS

An analysis was done of a prospective data registry based at a tertiary referral center for endometriosis. Eligible participants were patients aged 18 to 50 years who were referred between January 1, 2018, and December 31, 2019, diagnosed with endometriosis, and subsequently underwent surgery at the center. Clinical features were compared between participants reporting worsening pelvic pain with orgasm and those without worsening pain with orgasm, including patient-reported variables, physical examination findings, and anatomic phenotyping at the time of surgery. Pelvic floor myalgia and uterine tenderness were assessed by palpation on pelvic examination, adenomyosis by ultrasound, and central nervous system sensitization via the Central Sensitization Inventory (range, 0-100).

OUTCOMES

Outcomes included pelvic or lower abdominal pain in the last 3 months that worsened with orgasm (yes/no).

RESULTS

Among 358 participants with endometriosis, 14% (49/358) reported pain worsened by orgasm while 86% (309/358) did not. Pain with orgasm was significantly associated with pelvic floor myalgia (55% [27/49] vs 35% [109/309]; Cohen's h = 0.40, P = .01) and higher scores on the Central Sensitization Inventory (mean ± SD, 53.3 ± 17.0 vs 42.7 ± 18.2; Cohen's d = 0.60, P < .001) but not with uterine tenderness or adenomyosis. Other clinical features associated with pain with orgasm were poorer sexual health (higher scores: deep dyspareunia, Cohen's h = 0.60; superficial dyspareunia, Cohen's h = 0.34; and Female Sexual Distress Scale-Revised, Cohen's d = 0.68; all P < .05) and poorer mental health (higher scores: Patient Health Questionnaire-9, 12.9 ± 6.7 vs 9.1 ± 6.3, Cohen's d = 0.59, P < .001; Generalized Anxiety Disorder-7, 9.4 ± 5.6 vs 6.8 ± 5.5, Cohen's d = 0.48, P = .002). Anatomic findings at the time of surgery did not significantly differ between the groups.

CLINICAL IMPLICATIONS

Interventions targeting pelvic floor myalgia and central nervous system sensitization may help alleviate pain worsened by orgasm in patients with endometriosis.

STRENGTHS AND LIMITATIONS

A strength is that pain worsened by orgasm was differentiated from dyspareunia. However, pain with orgasm was assessed by only a binary question (yes/no). Also, the study is limited to a single center, and there were limited data on sexual function.

CONCLUSION

Pelvic pain exacerbated by orgasm in people with endometriosis may be related to concurrent pelvic floor myalgia and central sensitization.

Linking Intra-Articular Inflammatory Biomarkers with Peripheral and Central Sensitization in Late-Stage Knee Osteoarthritis Pain: A Pilot Study

Background/Objectives: To investigate if intra-articular biomarkers relate to peripheral and central sensitization in patients with late-stage knee osteoarthritis (KOA). Methods: A total of 17 (6M, 11F) patients (aged 69 ± 10 years) were assessed for peripheral (pressure pain thresholds (PPT)) and central (temporal summation (TS) and conditioned pain modulation (CPM)) sensitization the day before total knee arthroplasty. Synovial fluid was collected during surgery and assayed for IL-6, IL-8, IL-10, TNF-α, CXCL-10, BDNF, NGF, CCL2, CCL5, VEGF, IL-1RI, MMP-1, MMP-7, IL-1β, and CXCL-9. Associations of biomarkers and their combinations reflecting chronic (CXCL-9) and acute ((CCL2×CXCL-10)/IL-10)) inflammation, cartilage degeneration (MMP-1×MMP-7), and neurotrophy (NGF×BDNF) with PPT, TS, and CPM were analyzed by bivariate correlations and by multiple linear regression analyses corrected for BMI, sex, and age. Results: The medial joint line and the superior medial joint region showed the lowest PPT. Higher acute inflammation related significantly to worse pressure tenderness at the superior medial joint region (R2 = 0.642; p = 0.010). Cartilage degeneration and chronic inflammation were associated with both absolute (R2 = 0.827; p = 0.001) and relative CPM (R2 = 0.882; p < 0.001). Acute inflammation and neurotrophy were related to relative TS at the m. tibialis anterior (R2 = 0.728; p = 0.02). Conclusions: This study demonstrates that increased levels of intra-articular biomarkers of acute inflammation are related to peripheral sensitization and that biomarkers of cartilage degeneration and chronic inflammation are associated with central sensitization. These results may be a stepping-stone toward a better understanding of the working mechanism of peripheral and central sensitization in KOA pain and the development of more targeted therapeutic interventions.

Parabrachial neurons promote nociplastic pain

The parabrachial nucleus (PBN) in the dorsal pons responds to bodily threats and transmits alarm signals to the forebrain. Parabrachial neuron activity is enhanced during chronic pain, and inactivation of PBN neurons in mice prevents the establishment of neuropathic, chronic pain symptoms. Chemogenetic or optogenetic activation of all glutamatergic neurons in the PBN, or just the subpopulation that expresses the Calca gene, is sufficient to establish pain phenotypes, including long-lasting tactile allodynia, that scale with the extent of stimulation, thereby promoting nociplastic pain, defined as diffuse pain without tissue inflammation or nerve injury. This review focuses on the role(s) of molecularly defined PBN neurons and the downstream nodes in the brain that contribute to establishing nociplastic pain.

Prevalence of Fibromyalgia and Widespread Pain in Psoriatic Arthritis: Association With Disease Severity Assessment in a Large US Registry

OBJECTIVE

The classic conception of pain etiology in rheumatologic disease is nociceptive pain-tissue injury and inflammation signaling through peripheral and central nerve fibers. But this can be mixed with other pain etiologies, including nociplastic, which is augmented pain experience due to central sensitization. The pain of fibromyalgia (FM) is nociplastic, occurs in 10% to 30% of patients with rheumatologic disease, and its presence can influence disease severity assessment. The objective of our study was to (1) ascertain the prevalence of FM and widespread pain (WP) in the CorEvitas psoriatic arthritis (PsA) registry as assessed by the Widespread Pain Index (WPI) and Symptom Severity Scale (SSS) questionnaires; (2) characterize the demographic and clinical factors associated with FM and WP; and (3) ascertain the association of FM and WP on the Clinical Disease Activity in Psoriatic Arthritis (cDAPSA) score and other disease activity measures.

METHODS

PsA registry patients completing the WPI/SSS questionnaires since May 2020, at their most recent visit recorded in the registry, were analyzed.

RESULTS

The analysis included 1,823 patients with PsA; 11.1% fulfilled the FM definition and 20.6% fulfilled the WP definition. Several factors were associated with the FM definition, including female sex, depression and/or anxiety, impaired function, increased body mass index, and increased number of comorbidities. cDAPSA, patient pain and global assessment, and tender joint count were twice as severe in patients with FM compared to those without.

CONCLUSION

FM prevalence is elevated in PsA and is associated with elevated disease measures, confounding reliable disease assessment for treat-to-target goals. Identification of FM as an influential contextual factor in disease assessment is recommended.

Evaluating Sensitization-associated, Neuropathic-like Symptoms and Psychological Factors in Patients With Interstitial Lung Disease

The aims of this study were to phenotype pain in patients with interstitial lung disease (ILD) by investigating the association between sensitization-associated symptoms with quality of life, anxiety/depression, pain catastrophizing, and kinesiophobia levels and identifying those risk factors explaining the variance of quality of life in individuals with ILD and pain. One hundred and thirty-two (38.6% women, mean age: 70, standard deviation: 10.5 years) patients with ILD completed clinical (age, sex, height, weight), psychological (Hospital Anxiety and Depression Scale [HADS] and the Pittsburgh Sleep Quality Index), and health-related quality of life (EQ-5D-5L) variables, as well as the Central Sensitization Inventory (CSI), the Self-Report Leeds Assessment of Neuropathic Symptoms (S-LANSS), Pain Catastrophizing Scale, and Tampa Scale for Kinesiophobia (TSK-11) questionnaires. The prevalence of sensitization-associated symptomatology (CSI), neuropathic-like features (S-LANSS), anxiety symptoms, depressive symptoms, or poor sleep was 20.5%, 23.5%, 23.6%, 22.9%, or 51.6%. Significant associations between CSI, S-LANSS, HADS-A, HADS-D, Pain Catastrophizing Scale, TSK-11, and EQ-5D-5L (.220 < r < .716) were found. The regression analysis revealed that CSI, TSK-11, and HADS-D explained 44.8% of the variance of EQ-5D-5L (r2 adjusted: .448). This study found the presence of sensitization-associated and neuropathic-like symptoms as well as other central nervous system-derived symptoms, such as anxiety, depression, poor sleep, pain catastrophizing, and kinesiophobia in 25% of ILD patients with pain. Sensitization-associated symptoms, depression, and kinesiophobia were associated with a worse quality of life. These findings would support that individuals with ILD can exhibit different pain phenotypes, including nociplastic-like pain phenotype based on self-reported measurements. PERSPECTIVE: Pain in patients with ILD can fulfill features of different phenotypes, including nociplastic pain, when sensory, emotional, and cognitive mechanisms are involved at the same time.

Reliability of Pressure Pain Threshold (PPT) and Conditioned Pain Modulation (CPM) in Participants with and without Chronic Shoulder Pain

The objectives of this study were to estimate the intra-rater and inter-rater reliability of the Pressure Pain Threshold (PPT) and Conditioned Pain Modulation (CPM) in healthy participants and patients with chronic shoulder pain. Additionally, the Standard Error of Measurement (SEM) and Smallest Detectable Change (SDC) were calculated. Thirty-one healthy volunteers and twenty patients with chronic shoulder pain were assessed using the PPT and CPM by two raters, with a 24 h interval between sessions. Excellent intra-rater reliability was demonstrated for PPT, with similar SEM and SDC when assessed by the same rater. The inter-rater reliability for PPTs in patients was moderate to good (ICC = 0.59-0.89) with higher SEM (73.83-121.98 kPa) and SDC (61.58-97.59) values than the asymptomatic group (ICC = 0.92-0.96, SEM = 49.61-103.12 kPa, SDC = 42.01-56.30) respectively. CPM's intra-rater reliability was good (ICC = 0.82) in the patients and moderate (ICC = 0.67) in the asymptomatic group, while inter-rater reliability was low for the asymptomatic group (ICC = 0.37) and extremely low (ICC = 0.074) for the patients, with comparable SEM and SDC outcomes in both groups. PPT and CPM measurements are highly reliable when conducted by the same rater on the same day. Patients had lower inter-rater PPT reliability but better intra-rater CPM reliability. Clinicians need to be mindful of potential variability when interpreting these test results.

Prevalence of Spinal Segmental Sensitization Syndrome in Outpatients Attending Physical Medicine and Rehabilitation Centers for Chronic Musculoskeletal Pain: A Multicenter Study

OBJECTIVE

To determine the prevalence of spinal segmental sensitization (SSS) syndrome, a regional pain disorder, among patients visiting physical medicine and rehabilitation centers (PM&RCs) for chronic musculoskeletal pain (CMSP).

DESIGN

An observational, descriptive, cross-sectional study conducted from March to July 2023.

SETTING

Seven PM&RCs from 5 cities, representing 3 care systems: Social Security (SS), Ministry of Health (MH), and private practice (PP).

PARTICIPANTS

All patients, regardless of age, attending a physiatry consultation for CMSP for the first time and who provided informed consent to participate were included. Nonprobabilistic sampling was employed.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

We estimated the overall prevalence of SSS syndrome as a percentage among patients with CMSP, stratified by health care institution, sex, age, and occupation type. We also recorded the spinal segments involved and any concomitant painful disorders (CPDs). SSS syndrome was diagnosed using standardized criteria.

RESULTS

Of the eligible participants, 319 with CMSP were enrolled; 73.4% were women, and the median age of participants was 56.9 (range, 13-89y) years. The overall prevalence of SSS syndrome was 53.3%. Of these, 69.1%, 42.2%, and 13.8% were in the SS, MH, and PP systems, respectively. The most affected were female participants (56.4%), those aged 50-64 years (60.4%), and those with active jobs (58.8%). Most commonly, the lumbosacral and lumbar segments were affected, followed by the lower and middle cervical levels. Spine pathologies were the most common CPDs.

CONCLUSION

The prevalence of SSS syndrome was high among patients who visited PM&RCs for CMSP and varied according to the care system. Further research on SSS syndrome is warranted to relieve the burden it poses on patients with CMSP and ensure proper diagnosis in clinical practice.

HfAlOx-based ferroelectric memristor for nociceptor and synapse functions

Efficient data processing is heavily reliant on prioritizing specific stimuli and categorizing incoming information. Within human biological systems, dorsal root ganglions (particularly nociceptors situated in the skin) perform a pivotal role in detecting external stimuli. These neurons send warnings to our brain, priming it to anticipate potential harm and prevent injury. In this study, we explore the potential of using a ferroelectric memristor device structured as a metal-ferroelectric-insulator-semiconductor as an artificial nociceptor. The aim of this device is to electrically receive external damage and interpret signals of danger. The TiN/HfAlOx (HAO)/HfSiOx (HSO)/n+ Si configuration of this device replicates the key functions of a biological nociceptor. The emulation includes crucial aspects, such as threshold reactivity, relaxation, no adaptation, and sensitization phenomena known as "allodynia" and "hyperalgesia." Moreover, we propose establishing a connection between nociceptors and synapses by training the Hebbian learning rule. This involves exposing the device to injurious stimuli and using this experience to enhance its responsiveness, replicating synaptic plasticity.

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.

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

PURPOSE OF THE REVIEW

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

RECENT FINDINGS

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

Rethinking neck-related arm pain: hypothetical clinical scenarios to differentiate the underlying IASP-defined pain mechanisms

Neck-related arm pain is frequently encountered in clinical settings, yet its underlying pain mechanisms remain elusive. While such pain radiating from the neck to the arm is often attributed to injuries or diseases of the nervous system (neuropathic pain), it can also arise from nociceptive (referred) or nociplastic sources. Regrettably, patients exhibiting this specific pain distribution are frequently diagnosed with varying terms, including 'cervicobrachialgia', 'cervicobrachial neuralgia', 'cervicobrachial pain syndrome', and 'cervical radiculopathy'. The ambiguity surrounding these diagnostic labels complicates the clinical reasoning process. It is imperative for clinicians to discern and comprehend the dominant pain mechanism. Three distinct hypothetical clinical scenarios depict patients with almost identical pain distribution but divergent dominant pain mechanisms. Within these scenarios, both subjective and objective examinations are employed to elucidate the dominant pain mechanism associated with neck-related arm pain: nociceptive, neuropathic, and nociplastic. Furthermore, clinicians must remain aware that the dominant pain mechanism can evolve over time.

Reduction of Chronic Primary Low Back Pain by Spinal Manipulative Therapy is Accompanied by Decreases in Segmental Mechanical Hyperalgesia and Pain Catastrophizing: A Randomized Placebo-controlled Dual-blind Mixed Experimental Trial

Chronic primary low back pain (CPLBP) refers to low back pain that persists over 3 months, that cannot be explained by another chronic condition, and that is associated with emotional distress and disability. Previous studies have shown that spinal manipulative therapy (SMT) is effective in relieving CPLBP, but the underlying mechanisms remain elusive. This randomized placebo-controlled dual-blind mixed experimental trial (NCT05162924) aimed to investigate the efficacy of SMT to improve CPLBP and its underlying mechanisms. Ninety-eight individuals with CPLBP and 49 controls were recruited. Individuals with CPLBP received SMT (n = 49) or a control intervention (n = 49), 12 times over 4 weeks. The primary outcomes were CPLBP intensity (0-100 on a numerical rating scale) and disability (Oswestry Disability Index). Secondary outcomes included pressure pain thresholds in 4 body regions, pain catastrophizing, Central Sensitization Inventory, depressive symptoms, and anxiety scores. Individuals with CPLBP showed widespread mechanical hyperalgesia (P < .001) and higher scores for all questionnaires (P < .001). SMT reduced pain intensity compared with the control intervention (mean difference: -11.7 [95% confidence interval, -11.0 to -12.5], P = .01), but not disability (P = .5). Similar mild to moderate adverse events were reported in both groups. Mechanical hyperalgesia at the manipulated segment was reduced after SMT compared with the control intervention (P < .05). Pain catastrophizing was reduced after SMT compared with the control intervention (P < .05), but this effect was not significant after accounting for changes in clinical pain. Although the reduction of segmental mechanical hyperalgesia likely contributes to the clinical benefits of SMT, the role of pain catastrophizing remains to be clarified. PERSPECTIVE: This randomized controlled trial found that 12 sessions of SMT yield greater relief of CPLBP than a control intervention. These clinical effects were independent of expectations, and accompanied by an attenuation of hyperalgesia in the targeted segment and a modulation of pain catastrophizing.

Pain neuroscience education improves post-traumatic stress disorder, disability, and pain self-efficacy in veterans and service members with chronic low back pain: Preliminary results from a randomized controlled trial with 12-month follow-up

Post-traumatic stress disorder (PTSD) and chronic low back pain (CLBP) are frequently co-morbid. Some research suggests that PTSD and CLBP may share common neurobiological mechanisms related to stress. Traditional biomedical education may be ineffective for PTSD and CLBP, especially when co-morbid. The purpose of this study is to determine if pain neuroscience education (PNE) is more effective than traditional education in reducing PTSD, disability, pain, and maladaptive beliefs in patients with CLBP. Participants with CLBP and possible PTSD/PTSD-symptoms were recruited for this study. Participants were randomly allocated to a PNE group or a traditional education group. The intervention included 30 minutes of education followed by a standardized exercise program once a week for 4-weeks with a 4 and 8-week follow-up and healthcare utilization assessed at 12-months. Forty-eight participants consented for this research study with 39 allocated to treatment (PNE n = 18, traditional n = 21). PNE participants were more likely to achieve a clinically meaningful reduction in PTSD symptoms and disability at short-term follow-up. At 12-months, the PNE group utilized healthcare with 76% lower costs. In participants with CLBP, PNE may reduce hypervigilance toward pain and improve PTSD symptoms. Participants who received PNE were more confident body-tissues were safe to exercise. These beliefs about pain could contribute to a decrease in perceived disability and healthcare consumption for CLBP.

Fatigue can influence the development of late-onset pain in post-COVID-19 syndrome: An observational study

BACKGROUND

Late-onset pain is frequent following COVID-19, and many pathogenetic mechanisms have been proposed. Identifying the main features of patients may help in designing tailored rehabilitative interventions.

METHODS

We enrolled post-COVID-19 patients with an increase in pain intensity of two points on the COVID-19 Yorkshire Rehabilitation Scale (C19-YRS) at 52 weeks compared to the pre-COVID-19 condition. All subjects were retrospectively monitored at 12, 26, and 52 weeks. A specific pain assessment was performed to determine the characteristics and mechanisms of pain. Catastrophizing, kinesiophobia, and other psychological symptoms were evaluated. The pressure pain threshold (PPT) and temporal summation (TS) were measured and compared in age- and sex-matched healthy controls to analyse pain characteristics.

RESULTS

A total of 67 patients were recruited, with 20 of them presenting an increase in pain at 52 weeks. Subjects of the two subgroups were similar in demographic and clinical characteristics at baseline; significant differences in fatigue, anxiety, mobility, ability to perform daily activities, and general health perception were recorded at 26 weeks. Fatigue significantly predicted pain onset (β = 0.54, p = 0.002). Sixteen different body regions were identified as painful, with a pain intensity of 6.0 ± 1.9. Most of the samples did not show neuropathic or nociplastic mechanisms. No differences in PPT and TS were recorded between patients and healthy controls.

CONCLUSIONS

Almost one out of three patients hospitalized for COVID-19 developed pain 1 year later, and fatigue seems responsible for chronicity. An overlapping of conditions may explain late-onset post-COVID-19 pain, and a comprehensive approach must be considered for patient management.

SIGNIFICANCE

Late-onset pain is frequent in post-COVID-19 syndrome and an overlapping of different mechanisms seems to be responsible for its development. Among many predisposing factors, fatigue in the months before seems to be one of the primary causes of pain one year following infection and its management may help to identify new strategies for prevention and treatment of late-onset pain.

Mental Health Outcomes of Endometriosis Patients during the COVID-19 Pandemic: Impact of Pre-pandemic Central Nervous System Sensitization

To correlate pain-related phenotyping for central nervous system sensitization in endometriosis-associated pain with mental health outcomes during the COVID-19 pandemic, the prospective Endometriosis and Pelvic Pain Interdisciplinary Cohort (ClinicalTrials.gov #NCT02911090) was linked to the COVID-19 Rapid Evidence Study of a Provincial Population-Based Cohort for Gender and Sex (RESPPONSE) dataset. The primary outcomes were depression (PHQ-9) and anxiety (GAD-7) scores during the pandemic. The explanatory variables of interest were the Central Sensitization Inventory (CSI) score (0-100) and endometriosis-associated chronic pain comorbidities/psychological variables before the pandemic. The explanatory and response variables were assessed for correlation, followed by multivariable regression analyses adjusting for PHQ-9 and GAD-7 scores pre-pandemic as well as age, body mass index, and parity. A higher CSI score and a greater number of chronic pain comorbidities before the pandemic were both positively correlated with PHQ-9 and GAD-7 scores during the pandemic. These associations remained significant in adjusted analyses. Increasing the CSI score by 10 was associated with an increase in pandemic PHQ-9 by .74 points (P < .0001) and GAD-7 by .73 points (P < .0001) on average. Each additional chronic pain comorbidity/psychological variable was associated with an increase in pandemic PHQ-9 by an average of .63 points (P = .0004) and GAD-7 by .53 points (P = .0002). Endometriosis patients with a history of central sensitization before the pandemic had worse mental health outcomes during the COVID-19 pandemic. As a risk factor for mental health symptoms in the face of major stressors, clinical proxies for central sensitization can be used to identify endometriosis patients who may need additional support. PERSPECTIVE: This article adds to the growing literature of the clinical importance of central sensitization in endometriosis patients, who had more symptoms of depression and anxiety during the COVID-19 pandemic. Clinical features of central sensitization may help clinicians identify endometriosis patients needing additional support when facing major stressors.

Persistent physical symptoms: definition, genesis, and management

Persistent physical symptoms (synonymous with persistent somatic symptoms) is an umbrella term for distressing somatic complaints that last several months or more, regardless of their cause. These symptoms are associated with substantial disability and represent a major burden for patients, health-care professionals, and society. Persistent physical symptoms can follow infections, injuries, medical diseases, stressful life events, or arise de novo. As symptoms persist, their link to clearly identifiable pathophysiology often weakens, making diagnosis and treatment challenging. Multiple biological and psychosocial risk factors and mechanisms contribute to the persistence of somatic symptoms, including persistent inflammation; epigenetic profiles; immune, metabolic and microbiome dysregulation; early adverse life experiences; depression; illness-related anxiety; dysfunctional symptom expectations; symptom focusing; symptom learning; and avoidance behaviours, with many factors being common across symptoms and diagnoses. Basic care consists of addressing underlying pathophysiology and using person-centred communication techniques with validation, appropriate reassurance, and biopsychosocial explanation. If basic care is insufficient, targeted psychological and pharmacological interventions can be beneficial. A better understanding of the multifactorial persistence of somatic symptoms should lead to more specific, personalised, and mechanism-based treatment, and a reduction in the stigma patients commonly face.

Is the Central Sensitization Inventory (CSI) associated with quantitative sensory testing (QST)? A systematic review and meta-analysis

Central sensitization (CS) involves an amplification of neural processing within the central nervous system that can result in widespread pain patterns and hypersensitivity to stimuli. The Central Sensitization Inventory (CSI) and various quantitative sensory testing (QST) methods purport to assess clinical markers of CS. The purpose of this systematic review and meta-analysis was to summarize and quantify the associations between total CSI scores and QST measures from previous studies. A systematic search identified 39 unique studies that were deemed eligible for the systematic review and 33 studies for meta-analyses (with 3314 subjects and 154 effect sizes), including five QST modalities: conditioned pain modulation, temporal summation, pressure pain threshold, heat pain threshold, and cold pain threshold. The meta-analysis yielded statistically significant CSI-QST correlations in total subject samples for all five QST modalities. The strongest associations were identified between CSI scores and pain threshold testing, especially pressure pain threshold, in which 51% of effects sizes, from 29 studies and 3071 subjects, were determined to be in a medium to large range.

Reported biological effects following Osteopathic Manipulative Treatment: A comprehensive mapping review

BACKGROUND AND PURPOSE

Osteopathic Manipulative Treatment (OMT) is a therapeutic whole-body approach mainly focused on correcting somatic dysfunctions. The aim of this scoping review is to systematically map the literature regarding the documented biological effects observed following OMT.

METHODS

The 2020 JBIRM version and the PRISMA-ScR were followed for the conceptualization and reporting of this review. The protocol was registered on the "Open Science Framework Registry" (https://doi.org/10.17605/OSF.IO/MFAUP). We searched for original articles published on Medline, Embase, and Scopus, from inception to the present.

RESULTS

Overall, 10,419 records were identified. After duplicate removal, screening for title and abstract, and specific exclusions with reasons, a total of 146 studies were included. Wide differences were detected among studies in their geographical localization, study design, temporal distribution, participants' condition, OMT protocols, and documented biological effects. Such variety in frequency distribution was properly described through descriptive statistics.

CONCLUSIONS

Biological modifications that appear to be induced by OMT have been detected in several body systems, but mostly in neurophysiological correlates and musculoskeletal changes. Results suggest a growing interest over the years on this topic, especially in the last two decades. More efforts in research are recommended to highlight whether such changes specifically depend on OMT, and to demonstrate its specific contribution to clinical practice.

Phenotyping of chronic pain in breast cancer survivors: an original study using the cancer pain phenotyping (CANPPHE) Network multidisciplinary international guidelines

PURPOSE

The primary aim of this cross-sectional study is to examine the prevalence of pain phenotypes in breast cancer survivors (BCS). A secondary aim entails examining whether health related quality of life differs between the main pain phenotypes in BCS.

METHODS

BCS who experienced chronic pain were asked to complete the numeric pain rating scale for pain, Margolis pain diagram, and short form 36 (SF-36). Following administration of questionnaires and quantitative sensory examinations were applied. To determine the prevalence of the predominant type of pain, a recently proposed classification system by the Cancer Pain Phenotyping (CANPPHE) Network was used.

RESULTS

Of the 86 female participants, 19 (22.09%) had dominant neuropathic pain, 18 (20.93%) had dominant nociceptive pain and 14 (16.28%) had dominant nociplastic pain. 35 participants (40.70%) were classified as having mixed pain. One-way ANOVA revealed a significant difference between the four pain groups for the SF-36 general health (F = 3.205, p = 0.027), social functioning (F = 4.093, p = 0.009), and pain (F = 3.603, p = 0.017) subscale scores.

CONCLUSION

This study found that pain in BCS was mostly of mixed phenotype, followed by predominantly neuropathic and nociplastic pain. Furthermore, it was found that, compared to BCS with predominant neuropathic and nociceptive pain, BCS with predominant nociplastic pain have lower health related quality of life in the areas of bodily pain and social functioning.

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 assigned female at birth (AFAB) individuals. Pain experience in these conditions may better fit with a new mechanistic pain descriptor, nociplastic pain, and nociplastic type 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 type 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 type pain, and showed nociplastic type pain to be a polygenic trait with significant SNP-heritability. We found significant genetic overlap between multisite chronic pain and nociplastic type 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 type pain along with distinct pathology in migraine and headache. We use a well-powered network approach to investigate nociplastic type pain using existing COPC GWAS output, and show nociplastic type pain to be a complex, heritable trait, in addition to contributing to understanding of potential mechanisms in development of nociplastic pain.

Rikkosan's Short-Term Analgesic Effect on Burning Mouth Syndrome: A Single-Arm Cohort Study

Burning mouth syndrome (BMS) is a chronic oral pain disorder. There is a theory that BMS is a form of nociplastic pain. A standard treatment for BMS has not yet been established. Kampo medicine is a traditional oriental medicine. The purpose of this study is to evaluate the effectiveness of Rikkosan-a traditional Japanese herbal medicine (Kampo)-in the treatment of BMS. A single-center retrospective study was conducted on 20 patients who were diagnosed with BMS and treated with Rikkosan alone (total daily dose; 7.5 g) three times daily for approximately 4 weeks (29.5 ± 6.5 days). Rikkosan was dissolved in hot water and taken internally. They had an average age of 63 years, and 90% were being treated for other illnesses, but their medication status was the same during this study period, except for Rikkosan. No adverse events were observed in patients. Numerical rating scale (NRS) or visual analog scale (VAS)/10 scores decreased significantly between the time of the initiation of Rikkosan and one month after (-2.1 ± 1.2, p < 0.05). Rikkosan has a short-term effect of reducing NRS by two levels in BMS patients.

Overview: Chronic Pain and Cannabis-Based Medicines

Chronic pain is primarily conceptualized as a disease in its own right when it is associated with emotional distress and functional impairment. Pathophysiologically, dysfunction of the cortico-mesolimbic connectome is of major importance, with overlapping signals in the nociceptive and stress systems. The endocannabinoid system plays an important role in the central processing of nociceptive signals and regulates the central stress response. Clinically, there is moderate evidence that cannabis-based medicines (CBM) can contribute to a significant reduction in pain, especially the associated pain affect, and improvement in physical function and sleep quality in a proportion of patients with chronic pain. The analgesic effect appears to be largely independent of the cause of pain. In this context, CBM preferentially regulates stress-associated pain processing.

Assessment of Multisensory Sensitivity May Assist With the Management of Children With Chronic Pain

Chronic pain is a significant problem in adults; however, it can also be challenging to evaluate and manage effectively in pediatric and adolescent populations. Many theories implicate different factors that cause pain to become chronic, more severe, or more detrimental to function. There is emerging evidence for the role of generalized multisensory sensitivity (MSS) as a contributing factor to chronic pain in the adult population; however, similar evidence in the pediatric literature is lacking. Thus, the purpose of this case series is to highlight the clinical use of MSS assessment in children and adolescents with chronic pain to better phenotype and provide targeted treatment. In this case series, we reviewed 5 patients between 12 and 16 years of age who received evaluation for multifocal, chronic pain in a multidisciplinary pain clinic. During the initial consultations, we reviewed the medical records, completed a full medical history, performed a physical examination, and assessed for MSS. It is theorized that MSS is a marker of increased central nervous system sensitivity to sensory input that may also impact pain processing and, potentially, a poorer prognosis. Four patients with MSS appeared to benefit from the inclusion of additional therapies, such as desensitization and occupational therapy, which was in contrast to the patient without notable MSS. Based on anecdotal observation of these 5 cases, increased sensory hypersensitivity is 1 additional factor that may be used to delineate possible neurobiological mechanisms and aid in the treatment decision-making for this challenging population.

Differential relationships between physical activity and pain phenotypes in individuals with spinal cord injury

BACKGROUND

Chronic pain affects 70% of individuals with spinal cord injury (SCI) and leads to declines in health and quality of life. Neuropathic and nociceptive pain are phenotypes derived from different mechanisms that contribute to pain perception. The objective of this research was to investigate differential pain responses to moderate-to-vigorous physical activity (MVPA) in two chronic pain phenotypes: neuropathic and nociceptive pain.

METHODS

Community-based physical activity levels were collected for one week in 17 individuals with SCI using a wrist-worn accelerometer, and daily pain ratings were assessed and categorized by phenotype. Physical activity levels were summarized to calculate minutes of MVPA. Correlational analyses were conducted to compare relationships between pain intensity and MVPA across individual participants and between pain phenotype groups.

RESULTS

The neuropathic pain group revealed significant negative correlation between MVPA and pain intensity. In the nociceptive pain group, there was no significant correlation between MVPA and pain intensity. Further analysis revealed two subgroups of positive (N = 4) and negative (N = 3) correlations between MVPA and pain intensity. Pain location differed between the subgroups of nociceptive pain. Individuals with negative correlation experienced neck and upper back pain, whereas individuals with positive correlation experienced unilateral upper extremity pain.

CONCLUSION

Differential relationships exist between pain phenotypes and MVPA in individuals with SCI. Pain location differed between the subgroups of nociceptive pain, which we presume may indicate the presence of nociplastic pain in some individuals. These results may contribute to the advancement of personalized pain management by targeting non-pharmacological interventions for specific pain phenotypes.Trial registration: ClinicalTrials.gov identifier: NCT05236933..

Parabrachial Calca neurons drive nociplasticity

Pain that persists beyond the time required for tissue healing and pain that arises in the absence of tissue injury, collectively referred to as nociplastic pain, are poorly understood phenomena mediated by plasticity within the central nervous system. The parabrachial nucleus (PBN) is a hub that relays aversive sensory information and appears to play a role in nociplasticity. Here, by preventing PBN Calca neurons from releasing neurotransmitters, we demonstrate that activation of Calca neurons is necessary for the manifestation and maintenance of chronic pain. Additionally, by directly stimulating Calca neurons, we demonstrate that Calca neuron activity is sufficient to drive nociplasticity. Aversive stimuli of multiple sensory modalities, such as exposure to nitroglycerin, cisplatin, or lithium chloride, can drive nociplasticity in a Calca-neuron-dependent manner. Aversive events drive nociplasticity in Calca neurons in the form of increased activity and excitability; however, neuroplasticity also appears to occur in downstream circuitry.

Sensitization-Associated Symptoms and Neuropathic-like Features in Patients with Cervical Dystonia and Pain

Background: This exploratory study evaluated the presence of sensitization-associated and neuropathic-like symptoms and identified their association with pressure sensitivity, pain, and disability in patients with cervical dystonia (CD). Methods: Thirty-one patients with CD (74.2% women, age: 61.2 years, SD 10.1) participated. Data collected included clinical variables, the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS), the Central Sensitization Inventory (CSI), the Self-administered Leeds Assessment of Neuropathic Symptoms and Signs (S-LANSS), the Hospital Anxiety and Depression Scale (HADS) and the Pittsburgh Sleep Quality Index (PSQI), as well as widespread pressure pain thresholds (PPTs). Results: Patients with CD with pain (n = 20, 64.5%) showed higher scores on the TWSTRS disability subscale and the CSI (p < 0.001), and lower PPTs (p < 0.05). Fifteen patients (15/31, 48%) showed sensitization-associated symptoms (CSI ≥ 40), whereas five of the patients with pain (5/20, 25%) exhibited neuropathic-like symptoms (S-LANSS ≥ 12). The CSI and S-LANSS were positively associated with the TWSTRS, HADS-A and HADS-D, and negatively associated with PPTs. HADS-D and S-LANSS explained 72.5% of the variance of the CSI (r2: 0.725), whereas CSI explained 42.3% of the variance of the S-LANSS (r2: 0.423). Conclusions: Pain is an important source of disability in CD, and may be a consequence of different mechanisms, including sensitization.

Virtually delivered Mindfulness-Oriented Recovery Enhancement (MORE) reduces daily pain intensity in patients with lumbosacral radiculopathy: a randomized controlled trial

Introduction

Lumbosacral radiculopathy (LR), also known as sciatica, is a common type of radiating neurologic pain involving burning, tingling, and numbness in the lower extremities. It has an estimated lifetime prevalence as high as 43%.

Objectives

The objective of this randomized controlled trial was to evaluate the impact of virtually delivered Mindfulness-Oriented Recovery Enhancement (MORE) on patients with LR during the COVID-19 pandemic.

Methods

Potentially eligible patients were identified using electronic health record queries and phone screenings. Participants were then randomized to MORE or treatment-as-usual (TAU) for 8 weeks, with pain intensity assessed daily. At baseline and follow-up visits, participants completed questionnaires assessing the primary outcome, disability, as well as quality of life, depression, mindful reinterpretation of pain, and trait mindfulness.

Results

In our study, patients undergoing virtual delivery of MORE had greater improvements in daily pain intensity (P = 0.002) but not in disability (P = 0.09), depression (P = 0.26), or quality of life (P = 0.99 and P = 0.89, SF-12 physical and mental component scores, respectively), relative to TAU patients. In addition, patients in MORE experienced significantly greater increases in mindful reinterpretation of pain (P = 0.029) and trait mindfulness (P = 0.035).

Conclusion

Among patients with lumbar radiculopathy, MORE significantly reduced daily pain intensity but did not decrease disability or depression symptoms. Given the long duration of symptoms in our sample, we hypothesize the discrepancy between changes in daily pain intensity and disability is due to fear avoidance behaviors common in patients with chronic pain. As the first trial of a mindfulness intervention in patients with LR, these findings should inform future integrative approaches to LR treatment, particularly when considering the increasing use of virtual interventions throughout the COVID-19 pandemic.

Current understanding of nociplastic pain

Nociplastic pain by the "International Association for the Study of Pain" is defined as pain that arises from altered nociception despite no clear evidence of nociceptive or neuropathic pain. Augmented central nervous system pain and sensory processing with altered pain modulation are suggested to be the mechanism of nociplastic pain. Clinical criteria for possible nociplastic pain affecting somatic structures include chronic regional pain and evoked pain hypersensitivity including allodynia with after-sensation. In addition to possible nociplastic pain, clinical criteria for probable nociplastic pain are pain hypersensitivity in the region of pain to non-noxious stimuli and presence of comorbidity such as generalized symptoms with sleep disturbance, fatigue, or cognitive problems with hypersensitivity of special senses. Criteria for definitive nociplastic pain is not determined yet. Eight specific disorders related to central sensitization are suggested to be restless leg syndrome, chronic fatigue syndrome, fibromyalgia, temporomandibular disorder, migraine or tension headache, irritable bowel syndrome, multiple chemical sensitivities, and whiplash injury; non-specific emotional disorders related to central sensitization include anxiety or panic attack and depression. These central sensitization pain syndromes are overlapped to previous functional pain syndromes which are unlike organic pain syndromes and have emotional components. Therefore, nociplastic pain can be understood as chronic altered nociception related to central sensitization including both sensory components with nociceptive and/or neuropathic pain and emotional components. Nociplastic pain may be developed to explain unexplained chronic pain beyond tissue damage or pathology regardless of its origin from nociceptive, neuropathic, emotional, or mixed pain components.

Role of sexuality in women with chronic pain: Results from an Italian cross-sectional study on chronic headache, fibromyalgia, and vulvodynia

Background/objectives

To compare sexual functioning, genital pain, and satisfaction among women diagnosed with various Chronic pain (CP) conditions. Additionally, it seeks to explore the role of sexual factors in predicting levels of central sensitization (indicative of CP-related mental and physical distress), physical, and mental quality of life (QoL) for each condition individually.

Methods

From April 2023 to January 2024, 1006 women categorized into five groups (Chronic Headache - CH; Fibromyalgia - FM, Vulvodynia - VU, Comorbidity group - CO, and Healthy Controls - HC) completed an online protocol.

Results

All groups reported sexual impairment: VU group exhibited the highest genital pain prevalence (97.93 %), followed by CO (74.29 %) and FM (55.91 %). ANCOVAs indicated lower sexual functioning scores for FM, VU, and CO compared to HC and CH. VU and CO reported lower satisfaction scores than other groups. Genital pain emerged as the primary predictor of central sensitization across all groups except controls. Regarding mental QoL, sexual satisfaction was significant for CH and CO, while genital pain and sexual satisfaction were significant for VU.

Conclusion

This study emphasizes the importance of integrating genito-pelvic pain assessment and addressing related sexual difficulties in CP diagnostics and care to enhance overall well-being and QoL.

Cutaneous targets for topical pain medications in patients with neuropathic pain: individual differential expression of biomarkers supports the need for personalized medicine

Introduction

Numerous potential cutaneous targets exist for treating chronic pain with topically applied active pharmaceutical ingredients. This preliminary human skin tissue investigation was undertaken to characterize several key biomarkers in keratinocytes and provide proof-of-principle data to support clinical development of topical compounded formulations for peripheral neuropathic pain syndromes, such as postherpetic neuralgia (PHN).

Objectives

The study intended to identify objective biomarkers in PHN skin on a patient-by-patient personalized medicine platform. The totality of biopsy biomarker data can provide a tissue basis for directing individualized compounded topical preparations to optimize treatment efficacy.

Methods

Referencing 5 of the most common actives used in topical pain relief formulations (ketamine, gabapentin, clonidine, baclofen, and lidocaine), and 3 well-established cutaneous mediators (ie, neuropeptides, cannabinoids, and vanilloids), comprehensive immunolabeling was used to quantify receptor biomarkers in skin biopsy samples taken from ipsilateral (pain) and contralateral (nonpain) dermatomes of patients with PHN.

Results

Epidermal keratinocyte labeling patterns were significantly different among the cohort for each biomarker, consistent with potential mechanisms of action among keratinocytes. Importantly, the total biomarker panel indicates that the enriched PHN cohort contains distinct subgroups.

Conclusion

The heterogeneity of the cohort differences may explain studies that have not shown statistical group benefit from topically administered compounded therapies. Rather, the essential need for individual tissue biomarker evaluations is evident, particularly as a means to direct a more accurately targeted topical personalized medicine approach and generate positive clinical results.

Nociceptive, neuropathic, or nociplastic low back pain? The low back pain phenotyping (BACPAP) consortium's international and multidisciplinary consensus recommendations

The potential to classify low back pain as being characterised by dominant nociceptive, neuropathic, or nociplastic mechanisms is a clinically relevant issue. Preliminary evidence suggests that these low back pain phenotypes might respond differently to treatments; however, more research must be done before making specific recommendations. Accordingly, the low back pain phenotyping (BACPAP) consortium was established as a group of 36 clinicians and researchers from 13 countries (five continents) and 29 institutions, to apply a modified Nominal Group Technique methodology to develop international and multidisciplinary consensus recommendations to provide guidance for identifying the dominant pain phenotype in patients with low back pain, and potentially adapt pain management strategies. The BACPAP consortium's recommendations are also intended to provide direction for future clinical research by building on the established clinical criteria for neuropathic and nociplastic pain. The BACPAP consortium's consensus recommendations are a necessary early step in the process to determine if personalised pain medicine based on pain phenotypes is feasible for low back pain management. Therefore, these recommendations are not ready to be implemented in clinical practice until additional evidence is generated that is specific to these low back pain phenotypes.

Social cognition abilities in patients with primary and secondary chronic pain

Previous evidence suggested that chronic pain is characterized by cognitive deficits, particularly in the social cognition domain. Recently, a new chronic pain classification has been proposed distinguishing chronic primary pain (CPP), in which pain is the primary cause of patients' disease, and chronic secondary pain (CSP), in which pain is secondary to an underlying illness. The present study aimed at investigating social cognition profiles in the two disorders. We included 38 CPP, 43 CSP patients, and 41 healthy controls (HC). Social cognition was assessed with the Ekman-60 faces test (Ekman-60F) and the Story-Based Empathy Task (SET), whereas global cognitive functioning was measured with the Montreal Cognitive Assessment (MoCA). Pain and mood symptoms, coping strategies, and alexithymia were also evaluated. Correlations among clinical pain-related measures, cognitive performance, and psychopathological features were investigated. Results suggested that CSP patients were impaired compared to CPP and HC in social cognition abilities, while CPP and HC performance was not statistically different. Pain intensity and illness duration did not correlate with cognitive performance or psychopathological measures. These findings confirmed the presence of social cognition deficits in chronic pain patients, suggesting for the first time that such impairment mainly affects CSP patients, but not CPP. We also highlighted the importance of measuring global cognitive functioning when targeting chronic pain disorders. Future research should further investigate the cognitive and psychopathological profile of CPP and CSP patients to clarify whether present findings can be generalized as disorder characteristics.

Physical activity level and physical fitness in subjects with chronic musculoskeletal pain: a cross-sectional study

Background

Low physical activity (PA) levels and low physical fitness (PF) have been reported in subjects with temporality-based chronic pain; however, it is unknown whether there are differences in subjects with nociplastic pain (NP) compared with subjects with non-nociplastic pain (NNP).

Objective

The aim was to compare the levels of PA and PF in patients with chronic, nociplastic, and non-nociplastic musculoskeletal pain.

Methods

This is an analytical, cross-sectional study. The sample comprised 30 patients receiving ambulatory physiotherapy treatment. Pain was classified as NP or NNP according to the International Association for the Study of Pain categorization system. The PA level was measured with the International Physical Activity Questionnaire-Short Form, and the PF level was measured with the hand grip strength test (HGS) to assess upper limb strength, the five Repetition Sit-to-Stand Test (5R-SRTS) to assess lower limb strength and power, and the YMCA 3 Min Step Test (YMCA-3MST) to estimate peak VO2. The results were compared with independent samples t-tests (with p < 0.05 considered significant). Cohen's d was calculated to determine the effect size.

Results

The NP group reported a significantly lower PA level than the NNP group, specifically the vigorous PA (p = 0.0009), moderate PA (p = 0.0002), and total PA (p = 0.005) dimensions. The NP group also showed significantly lower 5R-STS (p = 0.000) and HGS (p = 0.002) results compared with the NNP group. There were no significant differences in the YMCA-3MST between the NP and NNP groups (p = 0.635).

Conclusion

It is possible that the neurophysiological and neuromuscular changes related to NP are associated with a reduced ability to perform vigorous PA. Clinicians should identify the presence of NP comorbidities in conjunction with the diagnosis when establishing the therapeutic goals.

IUPHAR review: Navigating the role of preclinical models in pain research

Chronic pain is a complex and challenging medical condition that affects millions of people worldwide. Understanding the underlying mechanisms of chronic pain is a key goal of preclinical pain research so that more effective treatment strategies can be developed. In this review, we explore nociception, pain, and the multifaceted factors that lead to chronic pain by focusing on preclinical models. We provide a detailed look into inflammatory and neuropathic pain models and discuss the most used animal models for studying the mechanisms behind these conditions. Additionally, we emphasize the vital role of these preclinical models in developing new pain-relief drugs, focusing on biologics and the therapeutic potential of NMDA and cannabinoid receptor antagonists. We also discuss the challenges of TRPV1 modulation for pain treatment, the clinical failures of neurokinin (NK)- 1 receptor antagonists, and the partial success story of Ziconotide to provide valuable lessons for preclinical pain models. Finally, we highlight the overall success and limitations of current treatments for chronic pain while providing critical insights into the development of more effective therapies to alleviate the burden of chronic pain.

Exploring the complexities of pain phenotypes: OMERACT 2023 chronic pain working group workshop

OBJECTIVE

To educate and discuss pain mechanisms (nociceptive, neuropathic, nociplastic) illuminating its possible impact when measuring different outcomes, which may modify, confound and potentially bias the outcome measures applied across various aspects of Rheumatic Musculoskeletal Diseases (RMDs) clinical trials.

METHODS

In the plenary presentations, PM lectured on different pain mechanisms and impact on disease activity assessment. Data from two data sets of RMDs patients, which assessed the prevalence and impact of nociplastic pain were presented and reviewed. Audience breakout group sessions and polling were conducted.

RESULTS

Mixed pain etiologies may differentially influence disease activity assessment and therapeutic decision-making. Polling demonstrated a consensus on the need to assess different types of pain as a phenotype, as it constitutes an important contextual factor (a variable that is not an outcome of the trial, but needs to be recognized [and measured] to understand the study results), and to standardize across RMDs.

CONCLUSION

There is need for a standardized pain measure that can differentiate underlying pain mechanisms.

Altered somatosensory functioning and mechanism-based classification in breast cancer patients with persistent pain

Pain is one of the most frequent and persistent side effects of breast cancer treatment. Besides pain, breast cancer survivors (BCS) are prone to experience a myriad of other signs and symptoms related to altered somatosensory function, including for example, hypoesthesia, allodynia, and hyperalgesia, both at the local site of cancer and in remote body parts. Different breast cancer treatments can have a direct effect on somatosensory functioning, resulting in a wide range of these signs and symptoms. To our knowledge, currently no comprehensive overview exists on altered somatosensory functioning and resulting signs and symptoms in BCS with persistent pain. Investigating altered somatosensory functioning in this population could provide more insights in the underpinning pathophysiological mechanisms and consequently improve prevention and treatment in the future. Therefore, in this paper, first, normal somatosensory functioning is described. Second, quantitative sensory testing is presented as the recommend method to evaluate somatosensory functioning. Third, existing evidence on altered somatosensory functioning in BCS with persistent pain is summarized. Altered somatosensory functioning related to the most common cancer treatment modalities, including surgery and radiotherapy, hormone therapy, and chemotherapy are discussed. In addition, evidence on the presence of nociplastic pain as pain resulting from altered somatosensory functioning without evidence for nociception and/or neuropathy in BCS is summarized. At last, a discussion on this available evidence, limitations, and perspectives for clinical practice and for research are made.

Contextualization of the concept of nociplastic pain in irritable bowel syndrome

The objective of this letter to the editor is to contextualize the concept of "nociplastic pain" in functional digestive disorders, especially in irritable bowel syndrome (IBS); and try to differentiate it from the term central sensitization, increasingly used in the literature, and with notable relevance in the pathophysiology of IBS.

Conservative Management of Acute Sports-Related Concussions: A Narrative Review

This review explores the application of the conservative management model for pain to sports-related concussions (SRCs), framing concussions as a distinct form of pain syndrome with a pathophysiological foundation in central sensitization. Drawing parallels with proven pain management models, we underscore the significance of a proactive approach to concussion management. Recognizing concussions as a pain syndrome allows for the tailoring of interventions in alignment with conservative principles. This review first covers the epidemiology and controversies surrounding prolonged concussion recovery and persistent post-concussion symptoms (PPCS). Next, the pathophysiology of concussions is presented within the central sensitization framework, emphasizing the need for early intervention to mitigate the neuroplastic changes that lead to heightened pain sensitivity. Five components of the central sensitization process specific to concussion injuries are highlighted as targets for conservative interventions in the acute period: peripheral sensitization, cerebral metabolic dysfunction, neuroinflammation, glymphatic system dysfunction, and pain catastrophizing. These proactive interventions are emphasized as pivotal in accelerating concussion recovery and reducing the risk of prolonged symptoms and PPCS, in line with the philosophy of conservative management.

Central Sensitization and Neuropathic Pain Cumulatively Affect Patients Reporting Inferior Outcomes Following Total Knee Arthroplasty

UPDATE

This article was updated on November 17, 2023, because of previous errors, which were discovered after the preliminary version of the article was posted online. On page 102, the text that had read "In a post hoc analysis of the preoperative results, Group 1 showed significantly inferior WOMAC pain, function, and total scores compared with Group 4 (p < 0.05 for all). Groups 2 and 3 showed worse preoperative WOMAC pain, function, and total subscores compared with Group 4 (p < 0.05 for all). These results remained the same at 2 years after surgery." now reads "In a post hoc analysis of the preoperative results, Groups 1, 2, and 3 showed significantly inferior WOMAC pain, function, and total scores compared with Group 4 (p < 0.05 for all). At 2 years postoperatively, Group 1 showed inferior WOMAC pain, function, and total scores compared with the other groups (p < 0.05 for all). Also, Groups 2 and 3 had worse WOMAC pain, function and total scores compared with Group 4 (p < 0.05 for all)." Also, on page 106, the title of Table IV, which had previously read "Inter-Group Comparison of Preoperative Scores (Post Hoc Analysis)" now reads "Inter-Group Comparison of Postoperative Scores (Post Hoc Analysis)."

Maintaining vulvar, vaginal and perineal health: Clinical considerations

Knowledge of female genital anatomy and physiology is often inadequate or incorrect among women. Precise patient-physician conversations can be inhibited by a reluctance or inability to speak accurately about the vulva and vagina, with the terms often being used interchangeably. There is a paucity of scientific evidence and clinical guidelines to support women and physicians in ensuring best practices in feminine hygiene. In this review, the unmet needs in the field are highlighted. Evidence is provided for the complex array of physiological and pathological systems, mechanisms and behaviours that either protect or, if inappropriate, predispose the vulva and vagina to infections, irritation or other conditions. The need for attention to perineal health is recommended, given the interdependence of perineal and vulvar microbiota and the risk of colonic pathogens reaching the vulva and the vagina. Differences in feminine hygiene practices can vary widely across the world and among varying age groups, and suboptimal habits (such as vaginal douching or the use of certain cleansers) can be associated with increased risks of vulvar and vaginal conditions. Critical areas for discussion when advising women on their intimate health include: advice surrounding aesthetic vulvar cosmetic trends (such as depilation and genital cosmetic surgery), bowel health and habits, and protection against sexually transmitted infections. Routine, once-daily (maximum twice-daily) washing of the vulva with a pH-balanced, mild cleanser is optimal, ideally soon after bowel voiding, when feasible. Due to the finely balanced ecosystems of the vulva, the vagina and the perineal area, a scientific and clinical perspective is essential when determining the most appropriate vulvar cleansers based on their components. Correct intimate care may contribute to improved genital and sexual health and overall well-being. An increased awareness of correct practices will empower women to be the advocates of their own intimate health.