Assessment and manifestation of central sensitisation across different chronic pain conditions

How different experimental models of secondary hyperalgesia change the nociceptive flexion reflex

OBJECTIVE

In this neurophysiological study in healthy humans, we assessed how central sensitization induced by either high-frequency stimulation (HFS) or topical capsaicin application modulates features of the RIII reflex response. The ability of these stimuli to engage the endogenous pain modulatory system was also tested.

METHODS

In 26 healthy participants we elicited an RIII reflex using suprathreshold stimulation of the sural nerve. Subsequently HFS or capsaicin were applied to the foot and the RIII reflex repeated after 15 minutes. Contact heating of the volar forearm served as the heterotopic test stimulus to probe activation of the endogenous pain modulatory system.

RESULTS

HFS significantly reduced the pain threshold by 29% and the RIII reflex threshold by 20%. Capsaicin significantly reduced the pain threshold by 17% and the RIII reflex threshold by 18%. Both HFS and capsaicin left RIII reflex size unaffected. Numerical Rating Scale (NRS) pain scores elicited by the heterotopic noxious heat stimulus were unaffected by capsaicin and slightly increased by HFS.

CONCLUSIONS

HFS and capsaicin similarly modulated the pain threshold and RIII reflex threshold, without a concomitant inhibitory effect of the endogenous pain modulatory system.

SIGNIFICANCE

Our neurophysiological study supports the use of the RIII reflex in investigating central sensitization in humans.

Central sensitization in burning mouth syndrome: a practical approach using questionnaires

OBJECTIVES

Some experts have suggested that burning mouth syndrome (BMS) should be included in the family of central sensitivity syndromes, a group of similar medical disorders linked by the central sensitization (CS) mechanism. Our objective is to assess the presence of CS in patients with BMS by performing a clinical examination and administering questionnaires to measure the generalized extent of pain, the presence of associated symptoms, and the number of other concurrent chronic pain conditions.

STUDY DESIGN

We conducted a case-control study in 82 subjects (40 patients with BMS and 42 controls). Patients with BMS were diagnosed using The International Classification of Headache Disorders 3rd edition, beta version (ICHD-IIIβ) criteria. The Widespread Pain Index (WPI) and Symptom Severity (SS) Score questionnaires were used to determine the degree of central sensitivity. The number of other concurrent chronic pain conditions was determined with the Neblett inventory.

RESULTS

Data indicative of CS show a statistically significant association with BMS. Both SS Score and Widespread Pain Index scores higher in patients with BMS. Additionally, patients with BMS reported a significantly higher number of other central sensitivity syndromes.

CONCLUSIONS

Patients with BMS could present a CS component as well as other chronic pain conditions. The use of questionnaires may be useful to determine the degree of central sensitivity in patients with BMS.

Bedside clinical tests to assess sensitization in office workers with chronic neck pain

OBJECTIVE

This study aimed to assess pain sensitization in individual office workers with chronic neck pain through simple bedside quantitative sensory tests (QST) and to associate the findings with pain intensity and pain catastrophizing.

METHODS

One hundred-and-four office workers with chronic neck pain were assessed using pressure pain threshold (PPT) considering pain sensitive if PPTs were lower than 155 kPa in the upper trapezius and 245 kPa in the tibialis anterior. Pain sensitive to temporal summation of pain (TSP) was considered if there was a difference of two points in the visual analogue scale (VAS) comparing the first and last stimulus. Pain sensitive was considered to conditioned pain modulation (CPM) if the CPM-effect was less than -7.5%. Pain intensity and catastrophizing were measured using VAS and with the Pain Catastrophizing Scale.

RESULTS

There was at least one pain sensitive QST finding in 66 office workers (63.5%). TSP findings were the most common (48.1%), followed by PPT's (31.7%) and CPM (20.2%). Based on the QST findings, office workers were divided based on the number of individual QST findings, and higher pain intensity and pain catastrophizing scores were found in office workers with one (N = 38, P < 0.05) or two (N = 28, P < 0.05) compared with office workers with no QST findings (N = 38).

CONCLUSION

This study demonstrated that most office workers with chronic neck pain exhibit either widespread pressure hyperalgesia, facilitated TSP or impaired CPM, indicating pain sensitization within the central nervous system. This was associated with increased clinical pain and pain catastrophizing rumination scores.

Functional and structural neuroplastic changes related to sensitization proxies in patients with Osteoarthritis: a systematic review

OBJECTIVE

Several reports in literature have identified sensitization as a possible basis for the enhanced pain reactions associated with Osteoarthritis (OA). The aim of this current systematic review is to summarize functional and structural brain changes associated with surrogate sensitization parameters assessed in patients with OA-related pain.

DESIGN

Systematic review.

SUBJECTS

Patients with OA related pain.

METHODS

A literature search was conducted systematically in MEDLINE, CINAHL, EMBASE databases for human studies up to December 2019. Articles were included if they assessed brain imaging and senzitisation parameters (quantitative sensory testing and questionnaires) in adults with OA related pain. Methodological quality was assessed using the Methodological Index for Non-Randomized Studies (MINORS) score.

RESULTS

Five studies reporting on 138 patients were included in this review. The MINORS scale yielded mean scores of 8.5/16 and 12.3/24, for the cohort and case-control studies respectively. Four low-quality studies suggest a greater pain matrix activation associated with clinical measures of sensitization in patients with OA, while another study underlined the presence of structural changes (reduced gray matter volume) in the cortical areas involved in the nociceptive processing possible also related to sensitization.

CONCLUSION

This review shows conflicting evidence for structural and functional neuroplastic brain changes related to sensitization proxies in patients with OA.

Assessment of pain associated with chronic pancreatitis: An international consensus guideline

Pain is the most common symptom in chronic pancreatitis (CP) with a major impact on quality of life. Few validated questionnaires to assess pain in CP exist, and the lack of consensus negatively impacts clinical management, research and meta-analysis. This guideline aims to review generic pain questionnaires for their usability in CP, to outline how pain assessment can be modified by confounding factors and pain types, to assess the value of additional measures such as quality of life, mental health and quantitative sensory testing, and finally to review pain assessment questionnaires used specifically in CP. A systematic review was done to answer 27 questions that followed the PICO (Population; Intervention; Comparator; Outcome) template. Quality of evidence of the statements was judged by Grades of Recommendation, Assessment, Development and Evaluation (GRADE) criteria. The manuscript was sent for review to 36 experts from various disciplines and continents in a multi-stage Delphi process, and finally reviewed by patient representatives. Main findings were that generic pain instruments are valid in most settings, but aspects of pain are specific for CP (including in children), and instruments have to account for the wide phenotypic variability and development of sensitization of the central nervous system. Side effects to treatment and placebo effects shall also be considered. Some multidimensional questionnaires are validated for CP and are recommended together with assessment of quality of life and psychiatric co-morbidities. This guideline will result in more homogeneous and comprehensive pain assessment to potentially improve management of painful CP.

Post-inflammatory Abdominal Pain in Patients with Inflammatory Bowel Disease During Remission: A Comprehensive Review

Patients with inflammatory bowel disease often experience ongoing pain even after achieving mucosal healing (i.e., post-inflammatory pain). Factors related to the brain-gut axis, such as peripheral and central sensitization, altered sympatho-vagal balance, hypothalamic-pituitary-adrenal axis activation, and psychosocial factors, play a significant role in the development of post-inflammatory pain. A comprehensive study investigating the interaction between multiple predisposing factors, including clinical psycho-physiological phenotypes, molecular mechanisms, and multi-omics data, is still needed to fully understand the complex mechanism of post-inflammatory pain. Furthermore, current treatment options are limited and new treatments consistent with the underlying pathophysiology are needed to improve clinical outcomes.

Changes in Pain Sensitivity and Conditioned Pain Modulation During Recovery From Whiplash-associated Disorders

OBJECTIVE

The objective of this study was to investigate the pain-sensory profile of patients with whiplash-associated disorders (WADs) prior and post 2 weeks of standardized rehabilitation and after a 6-month follow-up.

MATERIALS AND METHODS

Twenty-two WAD participants (grade II; 14 women) and 22 sex-matched and age-matched healthy pain-free controls were enrolled. Pressure pain thresholds (PPTs) were assessed at local and distal muscles. Conditioned pain modulation (CPM) of PPTs was assessed using cuff pressure around the upper arm. Referred area of pain following supra-threshold pressure stimulation of the infraspinatus muscle was recorded on a body chart. Psychometric variables (pain intensity, area of perceived pain, pain catastrophizing, kinesiophobia, sleep problems, and depression level) were assessed. WAD group additionally completed the Neck Disability Index.

RESULTS

The WAD group demonstrated lower local PPTs compared with controls at all time points (P<0.05) and lower distal PPTs at baseline and at 2 weeks when compared with 6 months (within-group) (P<0.05). The WAD group had a reduced CPM response and larger induced referred pain areas compared with controls (P<0.05), while no within-group changes were observed at any time point. The WAD group reported higher pain intensity and perceived area of pain compared with controls at all time points (P<0.05) and a mean Neck Disability Index score of 41% at baseline, 16% at 2 weeks, and 4% at 6 months. Furthermore, the WAD group reported improvements in all other psychometric variables (P<0.05), although only pain catastrophizing levels were comparable to controls at 2 weeks.

DISCUSSION

PPTs but not CPM improved in the WAD group and were comparable to controls following 2 weeks following standardized rehabilitation, indicating that normalization of CPM may not be required to recover from WAD.

Exploring multidimensional characteristics in cervicogenic headache: Relations between pain processing, lifestyle, and psychosocial factors

OBJECTIVE

Although multidimensional interventions including physiotherapy, psychology, and education are generally recommended in managing headache, and to prevent chronification, such approach is lacking in cervicogenic headache (CeH). Therefore, exploring CeH within a biopsychosocial framework is deemed an essential first step.

METHODS

Non-randomized cross-sectional design to compare pain processing, lifestyle, and psychosocial characteristics between 18 participants with CeH (CeH group) (40.2 ± 10.9 years) and 18 matched controls (control group) (39.2 ± 13.1 years). Pain processing characteristics included degree of central sensitization (Central Sensitization Inventory), and (extra)-cephalic pressure pain thresholds (kPa/cm²/s). Lifestyle characteristics included sleep quality (Pittsburgh Sleep Quality Index), physical activity, screen time, and sedentary time (hours a week). Psychosocial characteristics included degree of depression, anxiety and stress (Depression Anxiety Stress Scale-21), and quality of life (Headache Impact Test-6).

RESULTS

Pain processing characteristics: More (p = .04) participants in the CeH group showed higher degrees of central sensitization compared to the control group. Lower (p < .05) (extra)-cephalic pressure pain thresholds were revealed in the CeH group compared to the control group for each muscle. Lifestyle and psychosocial characteristics: Compared to the control group, sleep quality and headache-related quality of life were worse (p < .0001) in the CeH group. Severe to extreme stress was experienced by more participants in the CeH group (p = .02). Further, significant relations between pain processing and (1) lifestyle characteristics and (2) psychosocial characteristics were seen in the CeH group.

CONCLUSION

Exploring multidimensional characteristics in CeH exposed relations between pain processing, lifestyle, and psychosocial characteristics. These novel findings fill a gap in the current scientific literature, and highlight the need for outcome research targeting lifestyle and psychosocial factors.

Exploring the effect of capsaicin-induced central sensitization on the upper limb nociceptive withdrawal reflex threshold

The nociceptive withdrawal reflex (NWR) threshold is commonly employed in the lower limb to assess clinical and experimentally induced pain. However, no studies to date have investigated changes in spinal nociception in the upper limb, via the NWR threshold, following experimentally induced central sensitization (CS). We tested the hypothesis that experimentally induced CS of the C5-C6 spinal segment significantly reduces NWR thresholds in muscles of the upper limb. Upper limb NWR thresholds from 20 young, healthy adults were assessed by applying noxious electrical stimuli to the right index finger and recording muscle activity from the biceps brachii (BI), triceps brachii (TRI), flexor carpi ulnaris (WF), and extensor carpi radialis longus (WE) muscles via surface electromyography. Topical cream (either 0.075% capsaicin, or control) was applied to the C5-C6 dermatome of the lateral forearm (50 cm²). NWR thresholds were compared at baseline, and four 10-min intervals after topical application. WF muscle NWR thresholds were significantly reduced in the capsaicin session compared to control, while TRI muscle NWR thresholds were significantly reduced 40 min after capsaicin application only (p < 0.05). There were no significant differences for BI or WE muscle NWR thresholds. We observed poor to moderate test-retest reliability for all upper limb NWR thresholds, a key contributor to the selective reduction in NWR thresholds among muscles. Accordingly, while our findings demonstrate some comparability to previously reported lower limb NWR studies, we concurrently report limitations of the upper limb NWR technique. Further exploration of optimal parameters for upper limb NWR acquisition is needed.

Investigation of Correlations Between Pain Modulation Paradigms

OBJECTIVE

Endogenous pain modulation can be quantified through the use of various paradigms. Commonly used paradigms include conditioned pain modulation (CPM), offset analgesia (OA), spatial summation of pain (SSP), and temporal summation of pain (TSP), which reflect spatial and temporal aspects of pro- and antinociceptive processing. Although these paradigms are regularly used and are of high clinical relevance, the underlying physiological mechanisms are not fully understood.

DESIGN

The aim of this study is therefore to assess the association between these paradigms by using comparable protocols and methodological approaches.

SETTING

University campus.

SUBJECTS

Healthy and pain-free volunteers (n = 48) underwent psychophysical assessment of CPM, OA, SSP, and TSP (random order) at the same body area (volar nondominant forearm) with individualized noxious stimuli.

METHODS

CPM included heat stimuli before, during, and after a noxious cold-water bath, whereas for OA, three heat stimuli were applied: baseline trial, offset trial, and constant trial. For the SSP paradigm, two differently sized heat stimulation areas were evaluated, whereas for TSP, the first and last stimulus of 10 consecutive short heat stimuli were assessed. A computerized visual analog scale was used to continuously evaluate pain intensity. The magnitudes of all associations between all paradigm pairs were analyzed with Spearman's correlation, and individual influencing factors were assessed with a multivariate linear regression model.

RESULTS

Weak to moderate correlations among all four paradigms were found (P > 0.05), and no distinct influencing factors were identified.

CONCLUSIONS

A limited association between pain modulation paradigms suggests that CPM, OA, SSP, and TSP assess distinct aspects of endogenous analgesia with different underlying physiological mechanisms.

Anodal Transcranial Direct Current Stimulation Reduces Secondary Hyperalgesia Induced by low Frequency Electrical Stimulation in Healthy Volunteers

The aim of the study was to determine whether transcranial direct current stimulation (tDCS) reduced pain and signs of central sensitization induced by low frequency electrical stimulation in healthy volunteers. Thirty-nine participants received tDCS stimulation under 4 different conditions: anodal tDCS of the primary motor cortex (M1), anodal tDCS of the dorsolateral prefrontal cortex (DLPFC), anodal tDCS over M1 and DLPFC concurrently, and sham tDCS. Participants were blind to the tDCS condition. The order of the conditions was randomized among participants. Pain ratings to pinpricks, the current level that evoked moderate pain, and pain induced by low frequency electrical stimulation were assessed in the forearm by an experimenter who was blind to the tDCS conditions. Anodal tDCS at M1 increased the current level that evoked moderate pain compared to sham and other conditions. Anodal tDCS of DLPFC completely abolished secondary hyperalgesia. Unexpectedly, however, concurrent anodal tDCS over M1 and DLPFC did not reduce pain or hyperalgesia more than M1 alone or DLPFC alone. Overall, these findings suggest that anodal tDCS over M1 suppresses pain, and that anodal tDCS over DLPFC modulates secondary hyperalgesia (a sign of central sensitization) in healthy participants. PERSPECTIVE: Anodal transcranial current stimulation (atDCS) at the left motor cortex and the dorsolateral prefrontal cortex increased the electrically-evoked pain threshold and reduced secondary hyperalgesia in healthy participants. Replication of this study in chronic pain populations may open more avenues for chronic pain treatment.

Peripheral, Central, and Cross Sensitization in Endometriosis-Associated Pain and Comorbid Pain Syndromes

Endometriosis-associated pain and the mechanisms responsible for its initiation and persistence are complex and difficult to treat. Endometriosis-associated pain is experienced as dysmenorrhea, cyclical pain related to organ function including dysuria, dyschezia and dyspareunia, and persistent pelvic pain. Pain symptomatology correlates poorly with the extent of macroscopic disease. In addition to the local effects of disease, endometriosis-associated pain develops as a product of peripheral sensitization, central sensitization and cross sensitization. Endometriosis-associated pain is further contributed to by comorbid pain conditions, such as bladder pain syndrome, irritable bowel syndrome, abdomino-pelvic myalgia and vulvodynia. This article will review endometriosis-associated pain, its mechanisms, and its comorbid pain syndromes with a view to aiding the clinician in navigating the literature and terminology of pain and pain syndromes. Limitations of our current understanding of endometriosis-associated pain will be acknowledged. Where possible, commonalities in pain mechanisms between endometriosis-associated pain and comorbid pain syndromes will be highlighted.

Characterizing Pain and Generalized Sensory Sensitivity According to Trauma History Among Patients With Knee Osteoarthritis

BACKGROUND

Childhood trauma and adversity have been linked to chronic pain and pain sensitivity, particularly centralized pain. Yet, there remain numerous gaps in our understanding of this link.

PURPOSE

We explored the association between nonviolent and violent childhood trauma and a component of centralized pain (i.e., generalized sensory sensitivity) and pain sensitivity using self-report measures of centralized pain and quantitative sensory testing (QST).

METHODS

Patients scheduled for a total knee arthroplasty (n = 129) completed questionnaires and QST prior to surgery.

RESULTS

We found that self-report measures of centralized pain (i.e., widespread pain, somatic awareness, and sensory sensitivity) displayed a graded relationship across trauma groups, with patients with a history of violent trauma reporting the highest scores. Univariable multinomial logistic regression analyses showed that higher sensory sensitivity was associated with increased risk of being in the nonviolent trauma group compared to the no trauma group. Furthermore, higher widespread pain, higher somatic awareness, and higher sensory sensitivity distinguished the violent trauma group from the no trauma group. In multivariable analyses, sensory sensitivity is uniquely distinguished between the violent trauma group and the no trauma group. QST did not distinguish between groups.

CONCLUSIONS

The findings highlight the need for future research and interventions that reduce sensory sensitivity for chronic pain patients with a history of violent childhood trauma.

Exploring the Pain in Patellofemoral Pain: A Systematic Review and Meta-Analysis Examining Signs of Central Sensitization

BACKGROUND

Patellofemoral pain (PFP) has high recurrence rates and minimal long-term treatment success. Central sensitization refers to dysfunctional pain modulation that occurs when nociceptive neurons become hyperresponsive. Researchers in this area of PFP have been increasingly productive in the past decade.

OBJECTIVE

To determine whether evidence supports manifestations of central sensitization in individuals with PFP.

DATA SOURCES

We searched MeSH terms for quantitative sensory testing (QST) pressure pain thresholds (PPTs), conditioned pain modulation (CPM), temporal summation, sensitization, hyperalgesia, and anterior knee pain or PFP in PubMed, SPORTDiscus, CINAHL, Academic Search Complete, and EBSCOhost.

STUDY SELECTION

Peer-reviewed studies that were written in English and published between 2005 and 2020 and investigated QST or pain mapping in a sample with PFP were included in this review.

DATA EXTRACTION

The initial search yielded 140 articles. After duplicates were removed, 78 abstracts were reviewed. The full text of 21 studies was examined, and we included 15 studies in our evaluation: 6 in the meta-analysis, 4 in the systematic review, and 5 in both the meta-analysis and systematic review.

DATA SYNTHESIS

A random-effects meta-analysis was conducted for 4 QST variables (local PPTs, remote PPTs, CPM, temporal summation). Strong evidence supported lower local and remote PPTs, impaired CPM, and facilitated temporal summation in individuals with PFP compared with pain-free individuals. Evidence for heat and cold pain thresholds was conflicting. Pain mapping demonstrated expanding pain patterns associated with long duration of PFP symptoms.

CONCLUSIONS

Signs of central sensitization were present in individuals with PFP, indicating altered pain modulation. The etiologic and treatment models of PFP should reflect the current body of evidence regarding central sensitization. Signs of central sensitization should be monitored clinically, and treatments with central effects should be considered as part of a multimodal plan of care.

From One Pain to Many: The Emergence of Overlapping Pains in Children and Adolescents

OBJECTIVES

The objective of this study was to compare children and adolescents with overlapping chronic pains (OCP) to those with single chronic pains (SCP) among youth presenting in specialized clinical settings, in an effort to identify potential risk factors for developing overlapping pains.

METHODS

A total of 1235 youth ages 8 to 18 seen in a tertiary care multidisciplinary pain clinic or a multidisciplinary headache clinic completed self-report measures of pain, disability, psychological functioning and clinical history and characteristics at the time of initial clinic visit. Information was captured in a chronic pain data repository and accessed for the current study.

RESULTS

Subsequent pain symptoms developed on average 11.9 months (SD=24.5 mo) after onset of the first pain symptom. Compared with patients with SCP, patients with OCP report more medical comorbidity, more developmental issues, and poorer current sleep and school functioning. They also scored significantly higher than patients with SCP on self-reported functional disability, pain catastrophizing, fear of pain, depression, anxiety, and psychological stress and lower quality of life (all Ps<0.001). In multivariate analysis, variables most strongly associated with presenting with OCP were age (odds ratio [OR]: 1.1, P<0.001), having a clinically significant high functional disability (OR: 1.4, P=0.3), and low quality of life (OR: 2.5, P<0.001).

DISCUSSION

Given their tendency toward more psychological and medical comorbidities, patients with OCP may require more intense and diverse treatment approaches. Some early life experiences may be a risk factor for development of OCP. Longitudinal studies are needed to fully evaluate the heightened risk for OCP associated with some of these factors.

Pain Catastrophizing, Self-reported Disability, and Temporal Summation of Pain Predict Self-reported Pain in Low Back Pain Patients 12 Weeks After General Practitioner Consultation: A Prospective Cohort Study

OBJECTIVES

Patients with low back pain (LBP) often demonstrate pain sensitization, high degree of pain catastrophizing, and psychological distress. This study investigated whether pain sensitization mechanisms, the Pain Catastrophizing Scale (PCS), and Start Back Screening Tool were associated with pain in recurrent LBP patients 12 weeks after consulting their general practitioner (GP).

MATERIALS AND METHODS

In 45 LBP patients, pressure pain thresholds, temporal summation of pain (TSP), conditioned pain modulation (CPM), the Roland Morris Disability Questionnaire (RMDQ), and the PCS were assessed before consultation. Patients were classified into low to medium or high risk of poor prognosis on the basis of the Start Back Screening Tool. Worst pain within the last 24 hours was assessed on a visual analogue scale (VAS) at inclusion and 12 weeks after GP consultation.

RESULTS

VAS scores were reduced after 12 weeks in the low-to-medium (N=30, P<0.05), but not the high-risk group (N=15, P=0.40). RMDQ was reduced after 12 weeks (P<0.001), but with no difference between the groups. PCS was reduced in the low-to-medium and the high-risk group (P<0.05). TSP was significantly higher at follow-up in the high-risk group compared with the low-to-medium-risk group (P<0.05). A linear regression model explained 54.9% of the variance in VAS scores at follow-up utilizing baseline assessments of TSP, RMDQ, and PCS.

DISCUSSION

This study indicate that patients with LBP and high self-reported disability, high pain catastrophizing, and facilitated TSP assessed when consulting the GP might predictive poor pain progression 12 weeks after the consultation.

Variability in clinical and neurophysiological evaluation of pain development following acute spinal cord injury: a case report

INTRODUCTION

Chronic neuropathic pain (NeP) often develops following traumatic spinal cord injury (SCI). This case report explores variability in clinical and neurophysiological aspects of pain evaluation in early post-trauma stages.

CASE PRESENTATION

A 34-year old female presenting with acute incomplete sensorimotor tetraplegia C4 AIS D was examined by neurological examination and pain assessment at three time points after acute trauma T1 (8 weeks), T2 (11 weeks), and T3 (24 weeks). Quantitative sensory testing (QST) and laser-evoked potentials (LEPs) were measured above (control area), at (area of NeP), and below (foot) the neurological level of injury (NLI). Musculo-skeletal and neuropathic pain were clinically present already during T1 but showed variations in localization and occurrence over time. Neuropathic pain classification varied between time points due to shifting of NLI. Above-level QST revealed minor, less pronounced abnormalities similar to at-level site. At-level QST (site of NeP) showed loss for thermal and mechanical detection thresholds but also gain of function for mechanical pain thresholds with a tendency of amelioration over time. QST below-level did not reveal remarkable changes over time. LEPs above- and below-level were within normal limits. At-level LEPs abolished after T1.

DISCUSSION

In early stages post injury (up to 6 month) variations in pain presentation for both, musculo-skeletal and neuropathic pain as well as QST and LEP could be demonstrated. These findings suggest ongoing adaption mechanisms in sensory pathways, which require further exploration and may be relevant for prognostic and preventive strategies against the development of chronic neuropathic and nociceptive pain.

The Combination of Preoperative Pain, Conditioned Pain Modulation, and Pain Catastrophizing Predicts Postoperative Pain 12 Months After Total Knee Arthroplasty

OBJECTIVES

Approximately 20% of knee osteoarthritis patients undergoing total knee arthroplasty (TKA) report chronic postoperative pain. Studies suggest that preoperative variables such as impaired descending pain control, catastrophizing, function, and neuropathic pain-like symptoms may predict postoperative pain 12 months after TKA, but the combined prediction value of these factors has not been tested. The current prospective cohort study aimed to combine preoperative risk factors to investigate the predictive value for postoperative pain 12 months after TKA.

DESIGN

Prospective cohort with follow-up 12 months after surgery.

PATIENTS

A consecutive sample of 131 knee osteoarthritis patients undergoing TKA.

METHODS

Pain intensity, Pain Catastrophizing Scale (PCS) scores, PainDETECT Questionnaire scores, conditioned pain modulation (CPM), and Oxford Knee Score (OKS) were obtained before and 12 months after TKA.

RESULTS

TKA improved pain (P < 0.001), PCS scores (P < 0.001), PainDETECT Questionnaire scores (P < 0.001), and OKSs (P < 0.001). Preoperative pain correlated with preoperative PCS scores (r = 0.38, P  <  0.001), PainDETECT scores (r = 0.53, P  <  0.001), and OKSs (r = -0.25, P  =  0.001). Preoperative PainDETECT scores were associated with preoperative PCS scores (r = 0.53, P  <  0.001) and OKSs (r = -0.25, P  =  0.002). Higher postoperative pain was correlated with high preoperative pain (r = 0.424, P  <  0.001), PCS scores (r = 0.33, P  <  0.001), PainDETECT scores (r = 0.298, P  =  0.001), and lower CPM (r = -0.18, P  =  0.04). The combination of preoperative pain, PCS score, and CPM explained 20.5% of variance in follow-up pain. PCS scores had a significant effect on pain trajectory when accounting for patient variance (t  =  14.41, P  <  0.0005).

CONCLUSION

The combination of high preoperative clinical pain intensity, high levels of pain catastrophizing thoughts, and impaired CPM may predict long-term postoperative pain 12 months after surgery.

A reliability study of a novel visual ischemic palpation scale in an experimental setting

BACKGROUND

Manual palpation is an important part of the clinical examination and generally it has low reliability. The aim of this study was to assess the reliability of a novel method for discriminating 3 different levels of palpation force.

METHODS

This reliability study included 96 healthy physiotherapists and physiotherapy students, who have been taught a new palpation graduated procedure called Visual Ischemic Palpatory Scale (VIPS), aimed to classify the applied pressure based on the finger's ischemia. Force was recorded by a force measurement system putting sensor over a rigid surface. To study the characteristic of VIPS the analysis of variance (ANOVA), Spearman rank correlation coefficient, Intraclass Correlation Coefficient (ICC), Standard Error of Measurements (SEM), and Minimal Detectable Change (MDC) were calculated.

RESULTS

Three distinct degrees were found with distinct forces expression: 1st degree 76.04 g (95% CI 65.86-86.22), 2nd degree 307.87 g (95% CI 263.29-352.44) and 3rd degree 1319.48 g (CI 1204.73-1434.23). Male participants significantly recorded a greater force than females. Good to excellent reliability across degrees were found (0.89 [95% CI: 0.82-0.97]), and final agreement found that more than 65.6% of sample recorded a force in the cut-offs identified. SEM values became bigger as the recorded force increased and MDC were equal to 48.94 g, 188.73 g, and 379.24 g for 1st, 2nd, and 3rd degree, respectively.

CONCLUSIONS

VIPS would appear to have three distinct degrees, sex dependent, with specific force expression for each degree and a good to excellent intra-rater reliability, but a poor agreement between raters.

Sensitization in office workers with chronic neck pain in different pain conditions and intensities

OBJECTIVES

Office workers with chronic neck pain demonstrates signs of widespread hyperalgesia, less efficient descending pain modulation, which could indicate sensitization of central pain pathways. No studies have assessed a wide variety of office workers with different chronic neck pain disorders and assessed the impact of pain intensity on assessments of central pain pathways. This study aimed to assessed pressure pain thresholds (PPTs), temporal summation of pain (TSP) and conditioned pain modulation (CPM) and to associate these with pain intensity and disability in subgroups of office workers.

METHODS

One hundred-and-seventy-one office workers were distributed into groups of asymptomatic and chronic neck pain subjects. Chronic neck pain was categorized as chronic trapezius myalgia and chronic non-specific neck pain and as 'mild-pain' (Visual Analog Scale [VAS]≤3) and 'moderate-pain' (VAS>3) groups. PPTs, TSP, CPM, and Copenhagen Psychosocial Questionnaire II were assessed in all subjects. Neck Disability Index and Pain Catastrophizing Scale were assessed in all the symptomatic office workers.

RESULTS

PPTs were lower in moderate pain (n=49) and chronic trapezius myalgia (n=56) compared with asymptomatic subjects (n=62, p<0.05). TSP was facilitated in moderate pain group compared with mild pain (n=60, p<0.0001) group and asymptomatic subjects (p<0.0001). No differences were found in CPM comparing the different groups (p<0.05). Multiple regression analysis identified Neck Disability Index and TSP as independent factors for prediction of pain intensity in chronic trapezius myalgia (R²=0.319) and chronic non-specific neck pain (R²=0.208). Somatic stress, stress and sleep as independent factors in chronic non-specific neck pain (R²=0.525), and stress in moderate pain group (R²=0.494) for the prediction of disability.

CONCLUSIONS

Office workers with chronic trapezius myalgia and moderate pain intensity showed significant signs of widespread pressure hyperalgesia. Moreover, the moderate pain group demonstrated facilitated TSP indicating sensitization of central pain pathways. Neck Disability Index and TSP were independent predictors for pain intensity in pain groups. Sleep and stress were independent predictors for disability.

Reliability of pressure pain threshold to discriminate individuals with neck and low back pain

BACKGROUND

Pressure pain threshold (PPT) is decreased in several musculoskeletal disorders, giving indirect evidence regarding pain status. Despite the fact that PPT has been already proven to be reliable in patients with acute conditions, there is great variability of methods and results observed within studies, and only a few evidences confirming its reliability in chronic conditions.

OBJECTIVE

The objective of this study was to determine the test-retest reliability of PPT in the neck and low back regions to discriminate individuals with neck or low back pain from healthy individuals. Additionally, one secondary aim was to establish the minimum detectable change (MDC) and the standard error of measurement for future clinical studies and interventions.

METHODS

In this reliability study, 74 individuals (15 individuals from the neck pain and 17 from the neck control group; 21 individuals from the low back pain and 21 from the low back control group). PPT was measured in the neck region (suboccipital, trapezius and supraspinal muscles) and in the lower back region (paraspinal muscles in the levels of L1, L3 and L5). Intrarater reliability was assessed using intraclass correlation coeficient and Bland-Altman.

RESULTS

Excellent intra-rater reliability was observed for both (ICC of 0.874 for the neck pain versus ICC of 0.895 in neck control group; ICC of 0.932 for the low back pain group versus ICC of 0.839 for the control group). A small bias was observed for all groups (-0.08 for the neck pain group versus 0.10 in the control group; and 0.32 in low back pain group versus 0.44 in the control group). Minimum detectable change of 0.63 kgf of neck pain and 1.21 kgf of low back pain was calculated. It was found difference in PPT between pain and control groups (p< 0.05).

CONCLUSION

It may be suggested that the protocol with PPT is reliable and able to discriminate individuals with and without neck and low back pain with a minor measurement error. Therefore, this method may be used to detect possible progress after interventions in patients with neck or low back pain.

C-tactile touch perception in patients with chronic pain disorders

Supplemental Digital Content is Available in the Text. C-tactile stimulation in patients with chronic pain results in reduced pleasantness perception. Results suggest impaired C-tactile function with functional loss of pleasant touch perception in patients with postherpetic neuralgia.

Introduction:

Slow brushing over the skin activates C-tactile nerve fibers that transmit pleasant tactile experiences in healthy subjects, leading to an inverted U-shaped velocity dependence of ratings: C-tactile optimal stroking stimulations are rated as more pleasant than slower or faster stimulations. Chronic pain diseases such as postherpetic neuralgia (PHN) and complex regional pain syndrome show altered C-fiber innervation density, sensory loss, and pain sensitization.

Objectives:

We aimed to investigate whether C-tactile function is affected in painful conditions.

Methods:

We assessed psychophysically C-tactile function and sensory perception thresholds in 16 patients with PHN, 19 patients with complex regional pain syndrome, and 22 healthy controls.

Results:

Assessment of C-tactile function showed a significantly altered perceived pleasantness of CT stimulation between healthy controls and patients with chronic pain. In specific, tactile stimulation was perceived less pleasant on the affected and contralateral side when compared with controls. In patients with PHN, velocity-dependent pleasantness ratings could not be obtained, suggesting highly impaired C-tactile function with functional loss of pleasant touch perception.

Conclusions:

In conclusion, this is the first report of impaired C-tactile function in patients with PHN. Reduced pleasantness resulting from gentle touch can reflect defective C-fiber function or result from central nervous system effects in a chronic pain state.

Psychological Interventions for Women with Persistent Pelvic Pain: A Survey of Mental Health Clinicians

Objective

To establish which psychological therapies mental health professionals use with reference to the treatment of women with persistent pelvic pain conditions. This research investigates overall therapies and specific techniques that clinicians believe are the most effective with this patient group, and the challenges mental health clinicians face in administering interventions. The study aims to suggest improvements to clinical practice and establish directions for targeted future research.

Design

Cross-sectional survey design.

Methods

An online survey was developed to ask mental health clinicians questions regarding the therapies and techniques they use with women experiencing persistent pelvic pain, their perspective on their practice in this area. The survey was advertised on relevant social media and professional websites. Survey results were tabled, and chi-square statistical analyses were undertaken to examine differences in therapy use according to country and profession.

Results

Mental health clinicians predominantly utilized cognitive behavioral therapy, acceptance and commitment therapy and associated techniques for women with persistent pelvic pain conditions. The results of the chi-square analyses showed that psychologists were more likely to use cognitive behavioral therapy or acceptance and commitment therapy, than counsellors who preferred counselling interventions. Chi-square analyses showed that Australian clinicians used acceptance and commitment therapy with a higher frequency than mental health clinicians in other countries. Clinicians provided multiple insights into their experiences working with women affected by persistent pelvic pain and their opinions as to valuable future research directions.

Conclusion

Cognitive behavioral therapy, acceptance and commitment therapy, and mindfulness therapies were most commonly used by mental health clinicians working with women with persistent pelvic pain conditions, despite severely limited evidence for the use of these psychological interventions in this client group.

The Automatization of a New Thermography Method Using Invasive Nociceptive Stimulation to Confirm an Autonomic Phenomenon within a Trigger Point Referred Pain Zone

The trigger points (TrPs) related to chronic low back pain that mimic sciatica have been lately recognized and included in the International Classification of Diseases, 11th Revision. This study examined the MATLAB software utility for the objective stratification of low back pain patients using the Minimally Invasive Procedure (MIP). The two diagnostic MIP parameters were: average temperature (ΔTavr) and autonomic referred pain (AURP). Chronic sciatica patients with TrPs (n = 20) and without TrPs (n = 20) were examined using the MIP. A significant increase in both parameters was confirmed for the thigh ROI of the TrP-positive patients, with ΔTavr being the leading parameter (p = 0.016, Exp(β) = 2.603). A continued significance of both parameters was confirmed from 6′00″ to 15′30″ (p < 0.05). The maximum AURP value was confirmed at 13′30″ (p < 0.05) (TrPs(+) 20.4 ± 19.9% vs. TrPs(-) 3.77 ± 9.14%; p = 0.000; CI (0.347,0.348)).

Quantitative Sensory Testing in Women After Surgery for Breast Cancer: A Systematic Review and Narrative Synthesis

OBJECTIVES

Quantitative sensory testing (QST) is a noninvasive technique to evaluate functioning of the somatosensory system. In many women surgically treated for breast cancer (BC), somatosensory functioning is disturbed with high prevalence of sensory loss and/or pain. The aims of this systematic review were (1) to summarize literature about QST methods; (2) to summarize the results within women surgically treated for BC (patients and survivors); (3) to compare QST results between women surgically treated for BC with and without pain; and (4) to compare the results between women surgically treated for BC and women without history of BC.

METHODS

A systematic literature search was conducted up to February 2020. Included studies had to report on QST methods (mechanical or thermal detection-pain thresholds, pressure pain thresholds [PPT], temporal summation [TS], or conditioned pain modulation [CPM]) in women over 18 years with-without pain, who had undergone unilateral surgery for BC.

RESULTS

Twenty-eight studies were included. Discrepancies in QST methods were greatest for TS and CPM. A local disturbance in thermal detection and an increased pain facilitation were found in BC survivors with pain in the surgical area. BC survivors with upper limb pain had significantly lower PPT at the surgical area and PPT were also significantly lower compared with women without history of BC, at affected and nonaffected sides for both local and remote body regions.

DISCUSSION

Standardized QST incorporating assessments of CPM is warranted in order to draw conclusions about neurobiological mechanisms of pain and somatosensory disturbances after surgical treatment for BC and to enhance mechanism-based management of these sequelae.

The development of a novel questionnaire assessing alterations in central pain processing in people with and without chronic pain

Background and aims The purpose of this study was to (a) develop and (b) conduct exploratory factor analysis on a novel self-report instrument for symptoms associated with altered central pain processing. Methods We first developed a 25-item questionnaire based on previous literature identifying symptoms and behaviours that may reflect altered spinal and supraspinal pain processing. We then administered this questionnaire to 183 people with chronic pain (n = 99) and healthy individuals (n = 84). Exploratory factor analysis was conducted to identify the factor structure of the questionnaire. Results Our results support a two-factor solution for the 25-item questionnaire that accounted for 57.2% of the total variance of responses in people with and without chronic pain. Factor one (11 items) included items related to alterations in sensation of pain, while factor two (seven items) included items associated with emotional and fatigue symptoms. Seven items showed weak factor loadings and were eliminated. Reliability was excellent, while both factors showed strong correlations with previously-validated self-report Instruments: (pain catastrophising, mood, vigilance, pain self-efficacy) and conditioned pain modulation, providing evidence for their validity. Conclusions We have developed a questionnaire containing two factors that appear to be related to two different symptom clusters, one of which is specifically related to pain and one of which contains other health-related symptoms related to mood and fatigue. These factors show excellent internal consistency and validity. This questionnaire may be a quick, easy and reliable instrument to assess central pain processing in clinical settings.

Predictive value of quantitative sensory testing for acute and chronic postsurgical pain after total joint arthroplasty: a systematic review

ABSTRACT

Quantitative sensory testing (QST) can be useful to identify high-risk patients for the development of chronic postsurgical pain. This systematic review aims to assess if presurgical sensory sensitivity measured using QST is associated with acute and chronic postsurgical pain after total joint arthroplasty. A systematic search was performed in September 2020 in PubMed, EMBASE, Web of Science, and Scopus, using terms related to total joint arthroplasty and QST. Prospective studies were included if they reported an association between presurgical QST and postsurgical pain in adults with osteoarthritis undergoing primary unilateral total joint arthroplasty. From 2994 identified studies, 18 met the inclusion criteria (1869 patients). Total knee arthroplasty was the most common surgery (16 studies), and pressure pain threshold was the most common test (11 studies), followed by dynamic measures (9 studies). Postsurgical pain was assessed at acute (5 studies), subacute (2 studies), and chronic (13 studies) time points. Risk of bias was assessed using the Quality in Prognosis Studies tool and evaluated as low to moderate in most domains. Fourteen studies reported at least one statistically significant association between QST and pain (acute: 4 studies, subacute: 1 study, and chronic: 9 studies). Pressure pain threshold was associated with postsurgical pain in 6 studies (of 11, 55%), heat pain threshold in 2 studies (of 6, 33%), conditioned pain modulation in 1 study (of 6, 17%), and temporal summation of pain in 5 studies (of 8, 63%). The predictive role of presurgical QST for postarthroplasty pain remains unclear, mainly because of heterogeneous methodologies and inconsistent results.

Revealing the time course of laser-evoked potential habituation by high temporal resolution analysis

BACKGROUND AND OBJECTIVES

Reduced laser-evoked potential (LEP) habituation indicates abnormal central pain processing. But the paradigm (four stimulation blocks a 25 stimuli) is time consuming and potentially omits important information on the exact habituation time course. This study examined whether a high temporal resolution (HTR) analysis (dividing the four stimulation blocks into 12 analysis blocks) can answer the following questions: (a) After how many stimuli does LEP habituation occur? (b) Is there a difference in LEP habituation in younger versus older subjects? (c) Is HTR applicable on radiculopathy patients?

METHODS

EEG data of 129 subjects were included. Thirty-four young healthy and 28 advanced-aged healthy subjects were tested with LEPs on the hand dorsum. Thirty-seven radiculopathy patients and 30 controls were tested with LEPs on the L3 dermatome. The EEG data of the hand dorsa have been analysed conventionally and with HTR analysis. The applicability of HTR has been tested on radiculopathy patients and respective controls.

RESULTS

HTR was well feasible in young healthy subjects and revealed a strong habituation effect during the first 25 stimuli (i.e. within the first 5 min). After approximately 48 stimuli, no further significant habituation was detectable. LEP amplitudes were higher in young subjects. HTR was unsuitable for elderly subjects and middle-aged radiculopathy patients.

CONCLUSIONS

In young healthy subjects, HTR allows a shortening of the test protocol while providing a detailed information on the time course of LEP habituation. A shorter protocol might be useful for the applicability of the LEP paradigm for clinical and experimental settings as well as pharmacological studies.

SIGNIFICANCE

The usage of high temporal resolution (HTR) analysis in young healthy subjects enables a short test protocol and provides the exact time course of laser-evoked potential habituation. This can be useful for the examination of neurological conditions affecting younger patients and for pharmacological studies. HTR was inapplicable in advanced-aged subjects and patients with radiculopathy.

Patients with symptomatic permanent atrial fibrillation show quantitative signs of pain sensitisation

Objective

Most patients with atrial fibrillation (AF) report symptoms, while one-third are asymptomatic. We hypothesised that sensory processing, in particular pain, differs in patients with symptomatic and asymptomatic AF.

Methods

Thirty individuals with permanent AF (15 symptomatic and 15 asymptomatic) completed the Atrial Fibrillation 6 (AF6) and short form 36 Health Survey questionnaires and underwent quantitative pain sensitisation testing using pressure algometry at the sternum (referred pain area) and the tibialis anterior muscle (generalised pain area). The primary objective was to assess differences in pressure pain thresholds (PPT), temporal summation of pain (TSP) and conditioned pain modulation (CPM) in the two groups. The secondary objective was to determine association of demographic and clinical parameters to measures of pain sensitisation.

Results

The symptomatic group had lower PPTs at both tibialis (p=0.004) and sternum (p=0.01), and impaired CPM (p=0.025) and facilitated TSP (p=0.008) at the tibialis but not sternum, compared with the asymptomatic group. The AF6 sum score was negatively correlated to PPT on both tibialis (r=−0.50, p=0.005) and sternum (r=−0.42, p=0.02) and positively correlated to TSP on both tibialis (r=0.57, p=0.001) and sternum (r=0.45, p=0.01), but not to CPM. The physical component summary score was positively correlated to the PPT on both tibialis (r=0.52, p=0.003) and sternum (r=0.40, p=0.03) and negatively to TSP on the tibialis (r=−0.53, p=0.003) but not sternum.

Conclusions

Patients with symptomatic AF exhibit lower pain tolerance than patients with asymptomatic AF, as well as impaired pain inhibitory control and facilitated summation of pain, indicating that pain sensitisation may be of importance in symptomatic AF.

Trial registration number

NCT04649437.

Reduction in Pain Inhibitory Modulation and Cognitive-Behavioral Changes in Patients With Chronic Low Back Pain: A Case-Control Study

BACKGROUND

Recent studies indicate that the assessment of conditioned pain modulation (CPM) responses and emotional factors can provide important information regarding chronification mechanisms, choices for more efficient therapeutic strategies, and clinical variables supporting a therapeutic prognosis.

AIMS

To investigate the impact of nonspecific chronic low back pain (NSCLBP) on CPM and psychosocial factors in individuals with NSCLBP compared with healthy controls.

DESIGN

Case-control study.

METHODS

Eighteen patients with NSCLBP and 18 healthy controls were recruited for this study. Pain intensity and affective-emotional aspects of pain, functional disability, kinesiophobia, depression, anxiety, and catastrophizing pain were obtained using a questionnaire. A CPM protocol was established to assess the functioning of the descending inhibitory system, with a cold pressor test as a conditioning stimulus and pressure pain threshold as a test stimulus. The maximal isometric strength of the trunk extensors also was evaluated.

RESULTS

Healthy participants demonstrated a greater CPM response than those with NSCLBP. Patients with NSCLBP exhibited significantly lower pressure pain threshold than healthy subjects. Moreover, patients with NSCLBP presented with a considerable exacerbation of cognitive-behavioral changes. NSCLBP patients showed diminished maximal isometric strength of the trunk extensor compared to healthy subjects.

CONCLUSIONS

The endogenous pain inhibition system is reduced in patients with NSCLBP, with significant cognitive-behavioral changes indicated by high levels of anxiety and moderate pain intensity.

SETTING

Clinical School of Physical Therapy of the Federal University of Delta of Parnaíba, Piauí - Brazil.

PARTICIPANTS/SUBJECTS

36 subjects with and without NSCLBP.

The Central Aspects of Pain in the Knee (CAP-Knee) questionnaire; a mixed-methods study of a self-report instrument for assessing central mechanisms in people with knee pain

OBJECTIVES

Pain is the prevailing symptom of knee osteoarthritis. Central sensitisation creates discordance between pain and joint pathology. We previously reported a Central Pain Mechanisms trait derived from eight discrete characteristics: Neuropathic-like pain, Fatigue, Cognitive-impact, Catastrophising, Anxiety, Sleep disturbance, Depression, and Pain distribution. We here validate and show that an 8-item questionnaire, Central Aspects of Pain in the Knee (CAP-Knee) is associated both with sensory- and affective- components of knee pain severity.

METHODS

Participants with knee pain were recruited from the Investigating Musculoskeletal Health and Wellbeing study in the East Midlands, UK. CAP-Knee items were refined following cognitive interviews. Psychometric properties were assessed in 250 participants using Rasch-, and factor-analysis, and Cronbach's alpha. Intra-class correlation coefficients tested repeatability. Associations between CAP-Knee and McGill Pain questionnaire pain severity scores were assessed using linear regression.

RESULTS

CAP-Knee targeted the knee pain sample well. Cognitive interviews indicated that participants interpreted CAP-Knee items in diverse ways, which aligned to their intended meanings. Fit to the Rasch model was optimised by rescoring each item, producing a summated score from 0 to 16. Internal consistency was acceptable (Cronbach's alpha = 0.74) and test-retest reliability was excellent (ICC2,1 = 0.91). Each CAP-Knee item contributed uniquely to one discrete 'Central Mechanisms trait' factor. High CAP-Knee scores associated with worse overall knee pain intensity, and with each of sensory- and affective- McGill Pain Questionnaire scores.

CONCLUSION

CAP-Knee is a simple and valid self-report questionnaire, which measures a single 'Central Mechanisms' trait, and may help identify and target centrally-acting treatments aiming to reduce the burden of knee pain.

Prognosis and transition of multi-site pain during the course of 5 years: Results of knee pain and function from a prospective cohort study among 756 adolescents

INTRODUCTION

Multi-site pain has not been investigated among adolescents suffering from knee pain. This study aimed to examine the trajectory of pain in adolescents with knee-pain, to determine if multi-site pain in adolescents together with other established prognostic factors (frequency of pain, sex, sports participation, Health Related Quality of Life (HRQoL)) was associated with five-year prognosis of knee-pain and function.

METHODS

This prospective cohort study included 504 adolescents with knee pain and 252 controls. At five-year follow-up, participants responded to an questionnaire which documented prescence and severity of knee pain and co-occurring pain.

RESULTS

At follow-up, 358 (71.0%) of those with knee-pain at baseline, and 182 (72.2%) controls responded. Female sex, low HRQoL, daily pain, and multi-site pain were associated with an increased odds of knee pain after 5 years (odds ratio: 1.41-3.37). Baseline multi-site pain was not associated with problems running at follow-up, whereas higher sports participation at baseline was associated with less problems running at follow-up (odd ratio 0.49). Among those with knee-pain at inclusion, the number of pain sites increased from a median of 2 (IQR 1-3) to 4 (IQR 2-6) at follow-up (P<0.05). Those with multi-site pain at follow-up score significantly worse in self-reported knee function, compared to those with one pain site only.

CONCLUSION

This study identified a set of factors that appeared to be associated with an increased risk of knee pain at five years follow up. Research is needed to understand and help direct treatment of adolescents with multi-site pain.

Effect of anodal high-definition transcranial direct current stimulation on the pain sensitivity in a healthy population: a double-blind, sham-controlled study

ABSTRACT

High-definition transcranial direct current stimulation (HD-tDCS) of brain areas related to pain processing may provide analgesic effects evident in the sensory detection and pain thresholds. The somatosensory sensitivity was assessed after HD-tDCS targeting the primary motor cortex (M1) and/or the dorsolateral prefrontal cortex (DLPFC). Eighty-one (40 females) subjects were randomly assigned to 1 of 4 anodal HD-tDCS protocols (20 minutes) applied on 3 consecutive days: Sham-tDCS, DLPFC-tDCS, M1-tDCS, and DLPFC&M1-tDCS (simultaneous transcranial direct current stimulation [tDCS] of DLPFC and M1). Subjects and experimenter were blinded to the tDCS protocols. The somatosensory sensitivity were assessed each day, before and after each tDCS by detection and pain thresholds to thermal and mechanical skin stimulation, vibration detection thresholds, and pressure pain thresholds. Subjects were effectively blinded to the protocol, with no significant difference in rates of whether they received real or placebo tDCS between the 4 groups. Compared with the Sham-tDCS, none of the active HD-tDCS protocols caused significant changes in detection or pain thresholds. Independent of tDCS protocols, pain and detection thresholds except vibration detection were increased immediately after the first tDCS protocol compared with baseline (P < 0.05). Overall, the active stimulation protocols were not able to induce significant modulation of the somatosensory thresholds in this healthy population compared with sham-tDCS. Unrelated to the HD-tDCS protocol, a decreased sensitivity was found after the first intervention, indicating a placebo effect or possible habituation to the quantitative sensory testing assessments. These findings add to the increasing literature of null findings in the modulatory effects of HD-tDCS on the healthy somatosensory system.

Safety and efficacy of an equimolar mixture of oxygen and nitrous oxide: a randomized controlled trial in patients with peripheral neuropathic pain

ABSTRACT

Nitrous oxide (N2O) is an odorless and colorless gas routinely used as an adjuvant of anesthesia and for short-duration analgesia in various clinical settings mostly in the form of an N2O/O2 50%-50% equimolar mixture (EMONO). Experimental studies have suggested that EMONO could also induce long-lasting analgesic effects related to the blockade of N-methyl-D-aspartate receptors. We designed the first international multicenter proof of concept randomized, placebo-controlled study to assess the efficacy and safety of a 1-hour administration of EMONO or placebo (medical air) on 3 consecutive days up to 1 month after the last administration in patients with chronic peripheral neuropathic pain. A total of 240 patients were recruited in 22 centers in France and Germany and randomly assigned to 1 study group (120 per group). Average pain intensity (primary outcome), neuropathic pain characteristics (Neuropathic Pain Symptom Inventory), Patient Global Impression of Change, anxiety, depression, and quality of life were systematically assessed before and after treatment. The changes in average pain intensity between baseline and 7 days after the last administration were not significantly different between the 2 groups. However, evoked pain intensity (predefined secondary endpoint) and Patient Global Impression of Change (exploratory endpoint) were significantly improved in the EMONO group, and these effects were maintained up to 4 weeks after the last treatment administration. Mostly transient side effects were reported during the treatment administration. These encouraging results provide a basis for further investigation of the long-term analgesic effects of EMONO in patients with neuropathic pain.

Translation, cross-cultural adaptation and psychometric validation of the Thai version of the STarT Back Screening Tool in patients with non-specific low back pain

BACKGROUND

Low back pain (LBP) is a top musculoskeletal problem and a substantial cause of socioeconomic burden internationally. The STarT Back Screening Tool (SBST) is a useful screening tool to manage patients with LBP but it is unavailable in Thai. Therefore, the aims of this study were to translate and cross-culturally adapt the SBST into a Thai version (SBST-TH) and validate its psychometric properties (e.g., factor analysis, internal consistency, test-retest reliability, agreement, convergent validity and discriminative validity).

METHODS

Translation and cross-cultural adaptation of the SBST into Thai version were conducted according to standard guidelines. A total of 200 participants with non-specific LBP were invited to complete the SBST, visual analogue scale for pain intensity, Roland-Morris disability questionnaire (RMDQ), fear-avoidance beliefs questionnaire, pain catastrophising scale, hospital anxiety and depression scale and the EuroQol five-dimensional questionnaire. Thirty participants completed the SBST-TH twice with an interval of 48 h to evaluate test-retest reliability.

RESULTS

Factor analysis demonstrated two (physical and psychological) components for the SBST-TH (39.38% of the total variance). The Cronbach's alpha (0.86 for total score and 0.76 for psychosocial subscore) represent satisfactory internal consistency. The acceptability of intraclass correlation coefficient was found in the total (0.73) and subscore (0.79). The areas under the curve (AUC) for the total score ranged 0.67-0.85 and 0.66-0.75 for subscore. The excellent discriminative validity was observed (AUC = 0.85, 95% confidence interval = 0.72, 0.97) between the total score of the SBST-TH and disability (RMDQ). Spearman's correlation coefficients represented moderate to strong correlation (0.32-0.56) between the SBST-TH and all questionnaires. The findings suggest a good relationship between the SBST-TH and disability and quality of life. Owing to the results from the convergent and discriminative validity, construct validity of the SBST-TH can be supported. The minimal detectable changes of the total score and subscore were 2.04 and 1.60, respectively. Significant floor and ceiling effects were not found in the SBST-TH.

CONCLUSION

The SBST-TH was successfully translated and adapted. It is a valid and reliable tool to classify Thai patients with non-specific LBP into low, moderate and high risks for chronicity.

TRIAL REGISTRATION

TCTR20191009005 #.

Percutaneous cryoneurolysis for acute pain management: current status and future prospects

Introduction: Conventional nerve blocks utilize local anesthetic drugs to provide pain relief for hours or days following surgery or trauma. However, postoperative and trauma pain can last weeks or months. Ultrasound-guided percutaneous cryoneurolysis is an anesthetic modality that offers substantially longer pain relief compared to local anesthetic-based nerve blocks.Areas covered: In this review, we discuss the history, mechanism of action, and use of ultrasound-guided percutaneous cryoneurolysis by anesthesiologists in the setting of acute pain management.Expert opinion: Ultrasound-guided percutaneous cryoneurolysis offers the potential to provide weeks or months of pain relief following surgery or trauma. Compared to continuous local anesthetic-based peripheral nerve blocks, currently the gold standard for providing long duration postoperative analgesia, cryoneurolysis has benefits that include: 1) longer duration measured in weeks or months rather than days; 2) no external reservoir of local anesthetic to be carried by the patient; 3) no risk of infection; and 4) no risk of catheter dislodgement. However, cryoneurolysis can induce a prolonged motor block in addition to the sensory block, decreasing the appropriate indications to those in which potential sensory and motor deficits are acceptable. Additionally, cryoneurolysis of multiple nerves can have a substantial time requirement relative to conventional nerve blocks.

Strength training in addition to neuromuscular exercise and education in individuals with knee osteoarthritis-the effects on pain and sensitization

BACKGROUND

There is a lack of evidence of the relative effects of different exercise modes on pain sensitization and pain intensity in individuals with knee osteoarthritis (KOA).

METHODS

Ninety individuals with radiographic and symptomatic KOA, ineligible for knee replacement surgery, were randomized to 12 weeks of twice-weekly strength training in addition to neuromuscular exercise and education (ST+NEMEX-EDU) or neuromuscular exercise and education alone (NEMEX-EDU). Outcomes were bilateral, lower-leg, cuff pressure pain- and tolerance thresholds (PPT, PTT), temporal summation (TS), conditioned pain modulation (CPM), self-reported knee pain intensity and number of painful body sites.

RESULTS

After 12 weeks of exercise, we found significant differences in increases in PPT (-5.01 kPa (-8.29 to -1.73, p = .0028)) and PTT (-8.02 kPa (-12.22 to -3.82, p = .0002)) in the KOA leg in favour of ST+NEMEX-EDU. We found no difference in effects between groups on TS, CPM or number of painful body sites. In contrast, there were significantly greater pain-relieving effects on VAS mean knee pain during the last week (-8.4 mm (-16.2 to -0.5, p = .0364) and during function (-16.0 mm (-24.8 to -7.3, p = .0004)) in favour of NEMEX-EDU after 12 weeks of exercise.

CONCLUSION

Additional strength training reduced pain sensitization compared to neuromuscular exercise and education alone, but also attenuated the reduction in pain intensity compared to neuromuscular exercise and education alone. The study provides the first dose- and type-specific insight into the effects of a sustained exercise period on pain sensitization in KOA. Future studies are needed to elucidate the role of different exercise modes.

SIGNIFICANCE

This study is an important step towards better understanding the effects of exercise in pain management of chronic musculoskeletal conditions. We found that strength training in addition to neuromuscular exercise and education compared with neuromuscular exercise and education only had a differential impact on pain sensitization and pain intensity, but also that regardless of the exercise mode, the positive effects on pain sensitization and pain intensity were comparable to the effects of other therapeutic interventions for individuals with knee osteoarthritis.

The predictive value of quantitative sensory testing: a systematic review on chronic postoperative pain and the analgesic effect of pharmacological therapies in patients with chronic pain

Studies have suggested that quantitative sensory testing (QST) might hold a predictive value for the development of chronic postoperative pain and the response to pharmacological interventions. This review systematically summarizes the current evidence on the predictive value of QST for chronic postoperative pain and the effect of pharmacological interventions. The main outcome measures were posttreatment pain intensity, pain relief, presence of moderate-to-severe postoperative pain, responders of 30% and 50% pain relief, or validated questionnaires on pain and disability. A systematic search of MEDLINE and EMBASE yielded 25 studies on surgical interventions and 11 on pharmacological interventions. Seventeen surgical and 11 pharmacological studies reported an association between preoperative or pretreatment QST and chronic postoperative pain or analgesic effect. The most commonly assessed QST modalities were pressure stimuli (17 studies), temporal summation of pain (TSP, 14 studies), and conditioned pain modulation (CPM, 16 studies). Of those, the dynamic QST parameters TSP (50%) and CPM (44%) were most frequently associated with chronic postoperative pain and analgesic effects. A large heterogeneity in methods for assessing TSP (n = 4) and CPM (n = 7) was found. Overall, most studies demonstrated low-to-moderate levels of risk of bias in study design, attrition, prognostic factors, outcome, and statistical analyses. This systematic review demonstrates that TSP and CPM show the most consistent predictive values for chronic postoperative pain and analgesic effect, but the heterogeneous methodologies reduce the generalizability and hence call for methodological guidelines.

The Effect of Conditioned Pain Modulation on Tonic Heat Pain Assessed Using Participant-Controlled Temperature

OBJECTIVE

Descending pain modulation can be experimentally assessed by way of testing conditioned pain modulation. The application of tonic heat as a test stimulus in such paradigms offers the possibility of observing dynamic pain responses, such as adaptation and temporal summation of pain. Here we investigated conditioned pain modulation effects on tonic heat employing participant-controlled temperature, an alternative tonic heat pain assessment. Changes in pain perception are thereby represented by temperature adjustments performed by the participant, uncoupling this approach from direct pain ratings. Participant-controlled temperature has emerged as a reliable and sex-independent measure of tonic heat.

METHODS

Thirty healthy subjects underwent a sequential conditioned pain modulation paradigm, in which a cold water bath was applied as the conditioning stimulus and tonic heat as a test stimulus. Subjects were instructed to change the temperature of the thermode in response to variations in perception to tonic heat in order to maintain their initial rating over a two-minute period. Two additional test stimuli (i.e., lower limb noxious withdrawal reflex and pressure pain threshold) were included as positive controls for conditioned pain modulation effects.

RESULTS

Participant-controlled temperature revealed conditioned pain modulation effects on temporal summation of pain (P = 0.01). Increased noxious withdrawal reflex thresholds (P = 0.004) and pressure pain thresholds (P < 0.001) in response to conditioning also confirmed inhibitory conditioned pain modulation effects.

CONCLUSIONS

The measured interaction between conditioned pain modulation and temporal summation of pain supports the participant-controlled temperature approach as a promising method to explore dynamic inhibitory and facilitatory pain processes previously undetected by rating-based approaches.

Cold pain hypersensitivity predicts trajectories of pain and disability after low back surgery: a prospective cohort study

Improving the ability to predict persistent pain after spine surgery would allow identification of patients at risk and guide treatment decisions. Quantitative sensory tests (QST) are measures of altered pain processes, but in our previous study, preoperative QST did not predict pain and disability at single time-points. Trajectory analysis accounts for time-dependent patterns. We hypothesized that QST predict trajectories of pain and disability during 1 year after low back surgery. We performed a trajectory analysis on the cohort of our previous study (n = 141). Baseline QST included electrical, pressure, heat, and cold stimulation of the low back and lower extremity, temporal summation, and conditioned pain modulation. Pain intensity and Oswestry Disability Index were measured before, and 2, 6, and 12 months after surgery. Bivariate trajectories for pain and disability were computed using group-based trajectory models. Multivariable regressions were used to identify QST as predictors of trajectory groups, with sociodemographic, psychological, and clinical characteristics as covariates. Cold pain hypersensitivity at the leg, not being married, and long pain duration independently predicted worse recovery (complete-to-incomplete, incomplete-to-no recovery). Cold pain hypersensitivity increased the odds for worse recovery by 3.8 (95% confidence intervals 1.8-8.0, P < 0.001) and 3.0 (1.3-7.0, P = 0.012) in the univariable and multivariable analyses, respectively. Trajectory analysis, but not analysis at single time-points, identified cold pain hypersensitivity as strong predictor of worse recovery, supporting altered pain processes as predisposing factor for persisting pain and disability, and a broader use of trajectory analysis. Assessment of cold pain sensitivity may be a clinically applicable, prognostic test.

Temporal summation of mechanical pain prospectively predicts movement-evoked pain severity in adults with chronic low back pain

BACKGROUND

Biopsychosocial factors above and beyond pathoanatomical changes likely contribute to the severity of chronic low back pain. A pro-nociceptive endogenous pain modulatory balance (↓inhibition and ↑facilitation) may be an important contributor to chronic low back pain severity and physical function; however, additional research is needed to address this possibility. The objective of this study was to determine whether quantitative sensory tests of endogenous pain inhibition and facilitation prospectively predict movement-evoked pain and cLBP severity self-reported on a validated questionnaire.

METHODS

One hundred thirty-four individuals with chronic low back pain were enrolled in this two-session study. During the first study session, temporal summation of mechanical pain and conditioned pain modulation were assessed at the lumbar spine to determine endogenous pain facilitation and inhibition, respectively. One week later, participants returned for a second study session whereby they reported their pain severity and pain interference using the Brief Pain Inventory-Short Form. Movement-evoked pain and physical function capacity were assessed upon completion of the balance, walking, and transition from sit to stand tests of the Short Physical Performance Battery.

RESULTS

Temporal summation of mechanical pain, but not conditioned pain modulation, significantly and prospectively predicted greater movement-evoked pain and poorer physical function on the Short Physical Performance Battery. Neither temporal summation nor conditioned pain modulation were significantly related to self-reported pain severity or pain interference on the Brief Pain Inventory-Short Form.

CONCLUSIONS

Findings suggest that a pro-nociceptive pain modulatory balance characterized by enhanced pain facilitation may be an important driver of movement-evoked pain severity and poor physical function in individuals with chronic low back pain.

Human surrogate models of central sensitization: A critical review and practical guide

Background

As in other fields of medicine, development of new medications for management of neuropathic pain has been difficult since preclinical rodent models do not necessarily translate to the clinics. Aside from ongoing pain with burning or shock‐like qualities, neuropathic pain is often characterized by pain hypersensitivity (hyperalgesia and allodynia), most often towards mechanical stimuli, reflecting sensitization of neural transmission.

Data treatment

We therefore performed a systematic literature review (PubMed‐Medline, Cochrane, WoS, ClinicalTrials) and semi‐quantitative meta‐analysis of human pain models that aim to induce central sensitization, and generate hyperalgesia surrounding a real or simulated injury.

Results

From an initial set of 1569 reports, we identified and analysed 269 studies using more than a dozen human models of sensitization. Five of these models (intradermal or topical capsaicin, low‐ or high‐frequency electrical stimulation, thermode‐induced heat‐injury) were found to reliably induce secondary hyperalgesia to pinprick and have been implemented in multiple laboratories. The ability of these models to induce dynamic mechanical allodynia was however substantially lower. The proportion of subjects who developed hypersensitivity was rarely provided, giving rise to significant reporting bias. In four of these models pharmacological profiles allowed to verify similarity to some clinical conditions, and therefore may inform basic research for new drug development.

Conclusions

While there is no single “optimal” model of central sensitization, the range of validated and easy‐to‐use procedures in humans should be able to inform preclinical researchers on helpful potential biomarkers, thereby narrowing the translation gap between basic and clinical data.

Significance

Being able to mimic aspects of pathological pain directly in humans has a huge potential to understand pathophysiology and provide animal research with translatable biomarkers for drug development. One group of human surrogate models has proven to have excellent predictive validity: they respond to clinically active medications and do not respond to clinically inactive medications, including some that worked in animals but failed in the clinics. They should therefore inform basic research for new drug development.

Pressure pain thresholds in office workers with chronic neck pain: A systematic review and meta-analysis

OBJECTIVES

The purpose of this study was to (a) compare pressure pain threshold (PPT) values between office workers with chronic neck pain and asymptomatic controls; (b) establish reference PPT values in chronic neck pain; and (c) evaluate associations between PPTs and pain intensity, and disability.

METHODS

Seven English/Portuguese databases were searched for relevant literature. Studies investigating adult office workers (age >18 years) with chronic neck pain were included if PPTs were an outcome. The risk of bias was assessed using the Downs and Black checklist. Meta-analysis was conducted if a cluster contained at least two studies reporting the same PPTs.

RESULTS

Ten high quality, two low quality, and one poor quality studies were included. The meta-analysis revealed decreased PPT values in the upper trapezius, extensor carpi ulnaris, and tibialis anterior in office workers with chronic neck pain when compared with healthy workers, without a statistical difference (p > 0.05). The PPT reference value in the upper trapezius was 263 kPa (95% confidence interval [CI] = 236.35 to 289.70), and 365 kPa (95% CI = 316.66 to 415.12) for the tibialis anterior in office workers with chronic neck pain. No correlations were found between the upper trapezius PPT and pain intensity and disability.

CONCLUSION

This meta-analysis found that all the PPT measurements were not significantly reduced in office workers with chronic neck pain compared with healthy workers. These assumptions were based on a small sample of existing studies, and therefore further studies are necessary to quantify the differences in PPTs. Hypersensitivity PPT reference values are proposed for localized and extrasegmental sites in office workers with chronic neck pain.

The interrelatedness of chronic cough and chronic pain

Since chronic cough has common neurobiological mechanisms and pathophysiology with chronic pain, both clinical disorders might be interrelated. Hence, we examined the association between chronic cough and chronic pain in adult subjects in the Rotterdam Study, a large prospective population-based cohort study.Using a standardised questionnaire, chronic pain was defined as pain lasting up to 6 months and grouped into a frequency of weekly/monthly or daily pain. Chronic cough was described as daily coughing for at least 3 months duration. The longitudinal and cross-sectional associations were investigated bi-directionally.Of 7141 subjects in the study, 54% (n=3888) reported chronic pain at baseline. The co-prevalence of daily chronic pain and chronic cough was 4.4%. Chronic cough was more prevalent in subjects with daily and weekly/monthly chronic pain compared with those without chronic pain (13.8% and 10.3% versus 8.2%; p<0.001). After adjustment for potential confounders, prevalent chronic pain was significantly associated with incident chronic cough (OR 1.47, 95% CI 1.08-1.99). The association remained significant in subjects with daily chronic pain (OR 1.49, 95% CI 1.06-2.11) with a similar effect estimate, albeit non-significant in those with weekly/monthly chronic pain (OR 1.43, 95% CI 0.98-2.10). After adjustment for covariables, subjects with chronic cough had a significant risk of developing chronic pain (OR 1.63, 95% CI 1.02-2.62) compared with those without chronic cough.Chronic cough and chronic pain confer risk on each other among adult subjects, indicating that both conditions might share common risk factors and/or pathophysiologic mechanisms.

Stuck in the Middle With You: Why a Broad-Brush Approach to Defining Central Sensitization Does Not Help Clinicians and Patients

Central sensitization is (1) increasingly interpreted as central nervous system hyperexcitability that accounts for a general increase in sensitivity, and (2) used to explain a variety of pain and nonpain symptoms. In this commentary, we argue that such a broad interpretation might not be clinically useful because it fails to distinguish one patient from another based on pathophysiological mechanisms and does not facilitate tailored treatment. We recommend that clinicians use a person-centered approach when assessing and managing patients, considering the different interacting processes/mechanisms that can contribute to a patient's clinical presentation. J Orthop Sports Phys Ther 2021;51(5):204-206. Epub 15 Mar 2021. doi:10.2519/jospt.2021.10340.

Data-science-based subgroup analysis of persistent pain during 3 years after breast cancer surgery: A prospective cohort study

BACKGROUND

Persistent pain extending beyond 6 months after breast cancer surgery when adjuvant therapies have ended is a recognised phenomenon. The evolution of postsurgery pain is therefore of interest for future patient management in terms of possible prognoses for distinct groups of patients to enable better patient information.

OBJECTIVE(S)

An analysis aimed to identify subgroups of patients who share similar time courses of postoperative persistent pain.

DESIGN

Prospective cohort study.

SETTING

Helsinki University Hospital, Finland, between 2006 and 2010.

PATIENTS

A total of 763 women treated for breast cancer at the Helsinki University Hospital.

INTERVENTIONS

Employing a data science approach in a nonredundant reanalysis of data published previously, pain ratings acquired at 6, 12, 24 and 36 months after breast cancer surgery, were analysed for a group structure of the temporal courses of pain. Unsupervised automated evolutionary (genetic) algorithms were used for patient cluster detection in the pain ratings and for Gaussian mixture modelling of the slopes of the linear relationship between pain ratings and acquisition times.

MAIN OUTCOME MEASURES

Clusters or groups of patients sharing patterns in the time courses of pain between 6 and 36 months after breast cancer surgery.

RESULTS

Three groups of patients with distinct time courses of pain were identified as the best solutions for both clustering of the pain ratings and multimodal modelling of the slopes of their temporal trends. In two clusters/groups, pain decreased or remained stable and the two approaches suggested/identified similar subgroups representing 80/763 and 86/763 of the patients, respectively, in whom rather high pain levels tended to further increase over time.

CONCLUSION

In the majority of patients, pain after breast cancer surgery decreased rapidly and disappeared or the intensity decreased over 3 years. However, in about a tenth of patients, moderate-to-severe pain tended to increase during the 3-year follow-up.

The Modulatory Effect of QST in Shoulder Pain: A Systematic Review and Meta-Analysis

BACKGROUND

The underlying mechanisms for shoulder pain (SP) are still widely unknown. Previous reviews report signs of altered pain processing in SP measured using quantitative sensory testing (QST). Evidence suggests that QST might hold predictive value for SP after intervention, yet it is not known whether QST profiles can be modulated in response to different treatments. Therefore, this systematic review and meta-analysis aimed to assess if QST-parameters can be modified by interventions for patients with SP.

METHODS

Three databases were searched to identify eligible studies. Eligible studies had a prospective design, with at least one QST variable as an outcome in conjunction with an intervention measured before and after intervention. Studies that involved SP caused by spinal or brain injury and studies looking at combined chronic neck/shoulder pain were excluded.

RESULTS

19 studies investigating SP were eligible for inclusion for this review. Pressure pain threshold (PPT) was the most frequently used QST-parameter investigating local and widespread hyperalgesia. A meta-analysis was performed with data from 10 studies with a total of 16 interventions. Results demonstrated an overall acute effect (<24 hours after intervention) of interventions in favour of local decreased pain sensitivity and of remote decreased pain sensitivity comparing PPTs before and after interventions.

CONCLUSIONS

This study demonstrates that interventions such as exercise and manual therapy can modulate PPTs acutely both locally and remotely in patients with shoulder pain. Further research investigating the acute and long-term modulatory ability of these interventions on other QST-parameters is needed in patients with shoulder pain.