Targeting cortical representations in the treatment of chronic pain: a review

Tactile acuity, left/right judgment performance, motor imagery ability, and pressure-pain threshold in patients with chronic rotator cuff-related shoulder pain: a cross-sectional case-control study

BACKGROUND

Chronic pain can alter cortical pain representation, and tests like Two-Point Discrimination Test (TPDT), Left/Right Judgment Task (LRJT), motor imagery, and Pressure-Pain Threshold (PPT) can assess these changes. However, their applicability to all pain mechanisms is uncertain.

OBJECTIVE

To compare the TPDT, LRJT, motor imagery ability, and PPT of chronic rotator cuff-related shoulder pain (C-RCRSP) patients with asymptomatic and pain-free controls.

METHODS

Forty-eight C-RCRSP patients and 45 pain-free controls were assessed using a caliper for TPDT and the Recognize® application for LRJT. Motor ability, PPT, physical function, fear avoidance, pain catastrophizing, and Central Sensitization Inventory (CSI) were also evaluated. As part of the subgroup analysis, C-RCRSP patients were divided into two groups based on their CSI (≥40, n = 19; <40, n = 29).

RESULTS

C-RCRSP patients demonstrated higher TPDT thresholds [acromion (F = 5.41, p = 0.001) and deltoid (F = 26.67, p < 0.001)] but no significant differences in LRJT performance [recognition accuracy (F = 2.47, p = 0.063) and response time (F = 0.98, p = 0.414)] than pain-free controls in both shoulder joints. C-RCRSP patients had poorer motor imagery abilities (p < 0.001). The deltoid region PPT differed significantly between the groups (F = 17.45, p < 0.001), but it was not significant for the tibialis anterior region (F = 1.16, p = 0.33). C-RCRSP patients with a CSI≥40 reported higher night pain, reduced shoulder range of motion, slower response times, poorer motor imagery ability, and higher scores on pain-related questionnaires compared to those with a CSI<40 (p = 0.043-<0.001).

CONCLUSION

C-RCRSP patients demonstrated poorer tactile acuity, mechanical sensitivity, and motor imagery ability especially in those with central sensitization, which should be considered in treatment planning.

Comparison of Two Different Neuromodulation Treatments in Patients With Acute Zoster-Related Trigeminal Neuropathic Pain and Pain Catastrophizing

OBJECTIVE

This study aimed to compare the efficacy of two neuromodulation techniques, peripheral nerve stimulation (PNS) and pulsed radiofrequency (PRF), in patients with acute zoster-related trigeminal neuropathic pain with pain catastrophizing.

MATERIALS AND METHODS

A total of 65 patients with acute zoster-related trigeminal neuropathic pain and pain catastrophizing were recruited from the Department of Pain Management of the Affiliated Hospital of Southwest Medical University between March 2019 and March 2024. According to the order of enrollment, participants were randomly assigned to two groups: the PNS group (n = 31), which received stimulation of the supraorbital nerve, and the PRF group (n = 34), which underwent PRF treatment of the same nerve. Pain levels were assessed using a visual analog scale (VAS), and the dosage of the anticonvulsant pregabalin was recorded at baseline, one week, two weeks, one month, three months, and six months postoperatively. Additionally, patients were evaluated using the Pain Catastrophizing Scale (PCS) and the Short Form 36 (SF-36) Health Survey at baseline and one, three, and six months postoperatively. Both groups were also monitored for adverse events and patient satisfaction throughout the study period.

RESULTS

Both the PNS and PRF groups experienced significant pain relief. However, the PNS group demonstrated superior outcomes compared with the PRF group at both short-term follow-up time points (p < 0.05). No significant difference in VAS scores was observed between the PNS and PRF groups during the long-term (six-month) follow-up. Improvements were noted in the SF-36 (across all eight dimensions) and PCS scores in both groups following treatment (p < 0.05). Notably, the PCS scores in the PNS group were consistently lower than those in the PRF group at all follow-up time points (p < 0.05). Additionally, patients in the PNS group exhibited greater improvements in physical role limitations, somatic pain, general health, social functioning, emotional role limitations, and mental health compared with those in the PRF group (p < 0.05). There were no significant differences between the two groups regarding improvements in physical functioning and vigor. After treatment, the average daily dose of pregabalin (mg/d) was reduced in both groups, with patients in the PNS group requiring a lower dose than those in the PRF group. Furthermore, patients in the PNS group reported a significantly higher level of satisfaction (p < 0.05) based on satisfaction evaluations. No instances of bleeding, infection, or other adverse effects were observed in either group after treatment.

CONCLUSION

Both PNS and PRF are effective and feasible for managing pain in patients with acute zoster-related trigeminal neuropathic pain and pain catastrophizing. However, PNS demonstrates superior efficacy in terms of early pain relief, reduction of pain catastrophizing, and improvements in quality of life, accompanied by higher patient satisfaction compared with PRF.

Effectiveness of a scapular exercise program on functional outcomes in patients with hand, wrist or elbow disorders: A comprehensive systematic review with meta-analysis

BACKGROUND

Usually, patients with hand, wrist/forearm disorders report musculoskeletal complaints in the shoulder. Although, role of scapula is fundamental for movement and functional stability across the upper limb kinetic chain; however, there are no systematic reviews and meta-analyses that have analyzed the effect of scapular exercises in these patients.

PURPOSE

This study aimed to determine the effectiveness of a scapular exercise program on functional outcomes in patients with hand, wrist or elbow disorders.

STUDY DESIGN

Systematic review with meta-analysis.

METHODS

An electronic search was performed of the MEDLINE, EMBASE, Web of Science, Scopus, CENTRAL, Epistemonikos, CINAHL, SPORTDiscus, PEDro, and LILACS databases. The eligibility criteria included randomized clinical trials that investigated the effects of scapular exercises added to a conventional physiotherapy program on functional outcomes in patients with hand, wrist or elbow injuries or pathologies. Two authors independently performed the search, study selection, data extraction, and risk of bias assessment.

RESULTS

Six trials met the eligibility criteria and were included in the quantitative synthesis. For the comparison of scapular exercises plus conventional physiotherapy versus conventional physiotherapy alone, the mean difference for elbow and wrist function was 7.6 points (p = 0.04), upper limb function was 16.1 points (p < 0.01), grip strength was 15.4% (p = 0.01), pain free grip strength was 19.1 N (p = 0.13) and pain intensity at rest was -1.1 cm (p < 0.01). Additionally, there was a significant increase in muscle strength of serratus anterior 46.2 N (p < 0.01), middle trapezius 29.9 N (p = 0.01) and lower trapezius 45.9 N (p < 0.01).

CONCLUSIONS

In the short term, adding scapular exercises to conventional physiotherapy showed statistically significant differences in functional outcomes in patients with lateral elbow tendinopathy and distal radius fracture. However, most of these differences did not reach the minimum threshold to be considered clinically important. The evidence strength was high to low according to the GRADE approach. More quantity and quality of clinical trials is needed to confirm our findings.

PROSPERO REGISTRATION

CRD42022364829.

Effectiveness of movement representation techniques in non-specific shoulder pain: a systematic review and meta-analysis

This systematic review and meta-analysis aims to assess the effects of movement representation techniques (MRT) on pain, range of motion, functional outcomes, and pain-related fear in patients with non-specific shoulder pain (NSSP). A literature search conducted in PubMed, PEDro, EBSCO, Scopus, Cochrane Library, ScienceDirect, and gray literature on April 31, 2023. We selected seven randomized controlled trials based on the PICOS framework. Incomplete data or non-NSSP excluded. Study quality was assessed using the PEDro scale (mean score = 6.43), and certainty of evidence was evaluated with the GRADE approach. MRT demonstrated a large effect size for pain reduction (high heterogeneity, I2 = 85.2%, Hedges'g = 1.324, 95% CI = 0.388-2.260, P = 0.006), functional improvement (moderate heterogeneity, I2 = 70.82%, Hedges'g = 1.263, 95% CI = 0.622-1.904, P < 0.001), and reduction of pain-related fear (moderate heterogeneity, I2 = 70.86%, Hedges'g = 0.968, 95% CI = 0.221-1.716, P < 0.001). MRT also showed significant benefits for range of motion, particularly in flexion (low heterogeneity, I2 = 26.38%, Hedges'g = 0.683), abduction (low heterogeneity, I2 = 33.27%, Hedges'g = 0.756), and external rotation (low heterogeneity, I2 = 48.33%, Hedges'g = 0.542) (P < 0.001 for all), while no significant effect was found for internal rotation (P > 0.05). No publication bias was detected. While limited evidence and methodological concerns necessitate further research, MRT appears to positively impact pain, range of motion, functional outcomes, and pain-related fear in NSSP patients.

A multisite validation of brain white matter pathways of resilience to chronic back pain

Chronic back pain (CBP) is a global health concern with significant societal and economic burden. While various predictors of back pain chronicity have been proposed, including demographic and psychosocial factors, neuroimaging studies have pointed to brain characteristics as predictors of CBP. However, large-scale, multisite validation of these predictors is currently lacking. In two independent longitudinal studies, we examined white matter diffusion imaging data and pain characteristics in patients with subacute back pain (SBP) over 6- and 12-month periods. Diffusion data from individuals with CBP and healthy controls (HC) were analyzed for comparison. Whole-brain tract-based spatial statistics analyses revealed that a cluster in the right superior longitudinal fasciculus (SLF) tract had larger fractional anisotropy (FA) values in patients who recovered (SBPr) compared to those with persistent pain (SBPp), and predicted changes in pain severity. The SLF FA values accurately classified patients at baseline and follow-up in a third publicly available dataset (Area under the Receiver Operating Curve ~0.70). Notably, patients who recovered had FA values larger than those of HC suggesting a potential role of SLF integrity in resilience to CBP. Structural connectivity-based models also classified SBPp and SBPr patients from the three data sets (validation accuracy 67%). Our results validate the right SLF as a robust predictor of CBP development, with potential for clinical translation. Cognitive and behavioral processes dependent on the right SLF, such as proprioception and visuospatial attention, should be analyzed in subacute stages as they could prove important for back pain chronicity.

Comparison of tactile acuity between patients with chronic patellofemoral pain with central sensitization and healthy persons: A cross-sectional study

BACKGROUND

Patellofemoral pain (PFP) is a common multifactorial condition in young and physically active people.

OBJECTIVE

The occurrence of central sensitization may play an important role in sensory disturbance. This study was designed to investigate, in patients with chronic PFP, the presence of disturbances in tactile acuity with central sensitization.

METHODS

Thirty patients with chronic PFP and 30 matched healthy controls entered this cross-sectional study. Graphesthesia (numerical score), two-point discrimination (mm), and point-to-point sensation (mm) were assessed in all participants.

RESULTS

The results of between-group comparisons showed that there were significant differences between the involved knee in patients with chronic PFP and healthy participants in graphesthesia (median = 13 [case], 19 [control]; p < .001), two-point discrimination (median = 25.8 [case], 20.3 [control]; p < .001), and point-to-point sensation (median = 14.5 [case], 6.2 [control]; p < .001). There was also a significant difference in graphesthesia between the non-involved knee in patients with chronic PFP and healthy participants (median = 17 [case], 19 [control]; p = .003). The results of within-group comparisons revealed a significant difference in graphesthesia, two-point discrimination, and point-to-point sensation between the involved and non-involved knee in patients with chronic PFP (p < .001). Moreover, there was a positive correlation between two-point discrimination and pain in patients with chronic PFP (r = 0.446, p = .014).

CONCLUSION

The findings of this study reveal that there is a sensory deficit in patients with chronic PFP. Because sensory information is necessary for motor control and pain perception, we can assume that clinical symptoms in these patients are related to sensory deficits.

Rehabilitation Interventions for Adults With Complex Regional Pain Syndrome: A Scoping Review Protocol

OBJECTIVES

This scoping review will explore the literature related to rehabilitation interventions for the treatment of adults living with complex regional pain syndrome (CRPS), describe the domains and outcome measures used to assess their effectiveness, and examine the neurophysiological bases of these interventions.

INTRODUCTION

The unremitting symptoms of CRPS, a chronic pain condition, are associated with long-term disability, poor psychological health, decreased emotional and social well-being, and reduced quality of life. Effective treatment for persistent symptoms is notoriously difficult. Therapeutic approaches such as graded motor imagery or pain exposure therapy are recommended for CRPS but show mixed results, insufficient effectiveness, variability in outcome measures, and unclear neurophysiological bases.

INCLUSION CRITERIA

This review will consider studies that include any form of non-invasive rehabilitation intervention delivered by a healthcare professional in any setting for adults with a CRPS diagnosis. Quantitative, qualitative and observational studies, text and opinion papers will be considered.

METHODS

The Joanna Briggs Institute (JBI) methodology will be used to conduct this scoping review. MEDLINE, Embase, Scopus, APA PsycINFO, CINAHL, Cochrane, OpenGrey Google and ProQuest Dissertations and Theses Global (ProQuest) will be searched for studies in English published between 2007 and 2024. Two independent reviewers will screen the titles, abstracts, and full texts of the selected studies. Data collection will be performed using a tool developed by the researchers based on the standardised JBI tool. Data will be presented in a comprehensive narrative summary.

TRAIL REGISTRATION

https://doi.org/10.17605/OSF.IO/P967T.

The relationship between sustained hamstring pain and reorganisation of somatosensory representations: a randomised, controlled study

ABSTRACT

Recurrent hamstring injuries are highly prevalent amongst sporting populations. It has been hypothesised that pain from an initial hamstring injury may induce reorganisation of somatosensory representations that could contribute to reinjury. However, because of the cross-sectional nature of existing research, it remains unknown whether somatosensory changes are a cause or effect of pain or if they are driven by other potentially confounding factors. Here, we explored the effect of experimentally induced sustained hamstring pain on tasks that interrogate somatosensory and spatial representations. Fifty healthy participants were randomly allocated to an experimental group that performed an eccentric exercise protocol on the right hamstring to induce delayed onset muscle soreness or a control group performing a repetition-matched concentric exercise protocol. The tactile cortical representation was assessed using two-point discrimination and tactile localisation, whereas the proprioceptive representation was assessed using a left-right judgement task. Peripersonal spatial representations were assessed using an auditory localisation task. Assessments were performed at baseline and day 2. No between-group differences in tactile acuity were observed. However, improvements in left-right judgments and worsening of auditory localisation occurred in the experimental group compared with the control group. This study provides preliminary evidence showing that somatosensory changes occur in response to sustained hamstring pain. Experimentally induced, sustained hamstring pain elicited enhancements in proprioceptive processing and deficits in peripersonal spatial processing, suggesting a shift in the allocation of attentional resources from the external (peripersonal) to internal (body) environment. These findings may hold important implications for reinjury risk and rehabilitation following hamstring pain.

Psychological, physical and complementary therapies for the management of neuropathic pain

This chapter aims to explain and evaluate the evidence for psychological, physical and complementary therapies as part of a holistic plan for managing neuropathic pain. Psychological therapies refer to interventions targeting mental health, while physical therapies refer to interventions designed to target movement and functional ability, and complementary therapies are those that attempt to target key mechanisms of change to alter brain and body functioning, or thought processes related to the experience of pain. Each therapeutic modality is discussed to narratively report on the evidence and provide implications for clinicians. Where evidence was unavailable for neuropathic pain populations, evidence from chronic pain populations more broadly was considered. Although promising, there is a lack of high-quality evidence investigating the benefits and safety of psychological, physical and complementary therapies for the management of neuropathic pain. The low certainty evidence and lack of evidence across different neuropathic pain conditions impacts the ability to make recommendations for clinical practice. However, there are several potential areas for future research. Psychological therapies that focus on the underlying mechanisms related to emotion regulation may improve mood and pain, while cognitive and behavioural based approaches may improve psychological comorbidities such as anxiety and depression. Physical therapies involving physical activity and exercise, education, and graded motor imagery may improve functioning and reduce pain. Finally, complementary therapies including electroencephalography neurofeedback, acupuncture, virtual reality, hypnosis and transcutaneous electrical nerve stimulation may provide promising reductions in pain. There is a clear need for further high-quality trials to evaluate the benefits and safety of psychological, physical and complementary therapies to guide the management of neuropathic pain.

Body awareness disturbances in patients with low back pain: a systematic review

BACKGROUND

The pain-neuroscience literature has recently emphasized body perception or awareness. Impaired body perception results have been reported in many different chronic pain problems. Studies have reported that individuals with low back pain (LBP) also have body perception disturbances related to the lumbar spine.

OBJECTIVES

This review aimed to determine the evidence that body awareness alterations in individuals with LBP.

DESIGN

Systematic review.

METHOD

Studies were searched in PubMed, Cochrane Library, and Pedro databases up to January 2021. Each database was searched independently, according to a specific iteration research string. The protocol record of the systematic review was entered into the PROSPERO system.

RESULTS

Nine studies were included in this research. We found evidence to support more perceptual impairments in patients with LBP than healthy counterparts. In addition, the results of the studies showed an association between disrupted body awareness and pain severity, pain catastrophizing, and disability.

CONCLUSIONS

Body perception disturbances in LBP seem to be a promising path that needs to be further explored, with the ultimate goal of developing treatment contents targeting body awareness as a more comprehensive and valid evaluation and therapeutic method.

TRIAL REGISTRATION

The registration number was CRD42021235934.

Enhancing chronic low back pain management: an initial neuroimaging study of a mobile interoceptive attention training

Introduction

Chronic low back pain (cLBP) poses significant challenges, often addressed through avoidance or distraction. Emerging evidence suggests that mind-body interventions, like our novel Mind Your Pain (MyP) smartphone mobile application, may offer relief. We conducted a single-arm, mixed-methods neuroimaging study to assess the degree to which treatment response to our 8-week intervention, as measured by the reduction in the Pain, Enjoyment of Life and General Activity Scale (PEG), was associated with enhanced pain-related insula activation over time.

Methods

Twenty-nine individuals with cLBP completed patient-reported assessments, qualitative sensory testing (QST) measures, and neuroimaging pre- and post-MyP. Functional MRI data during experimental heat pain on the left forearm were collected and analyzed, comparing responders (≥50% reduction in PEG scores) and non-responders.

Results

MyP led to significant decreases in PEG scores overall. Furthermore, MyP responders exhibited increased pain-related activation in key brain regions, including the contralateral posterior insula, bilateral ventral anterior insula, ventral anterior cingulate, dorsolateral prefrontal cortex, and nucleus accumbens. Although baseline behavioral and sensory measures did not differ between the two responder groups, baseline neural differences related to the impact of the endogenous back pain were observed.

Discussion

MyP appears to modify pain response and underlying neural circuitry, suggesting neural changes in interoception may serve as biomarkers for mind-body interventions in cLBP. This study highlights the potential of MyP as a novel approach for cLBP management, warranting further investigation.

Brain white matter pathways of resilience to chronic back pain: a multisite validation

Chronic back pain (CBP) is a global health concern with significant societal and economic burden. While various predictors of back pain chronicity have been proposed, including demographic and psychosocial factors, neuroimaging studies have pointed to brain characteristics as predictors of CBP. However, large-scale, multisite validation of these predictors is currently lacking. In two independent longitudinal studies, we examined white matter diffusion imaging data and pain characteristics in patients with subacute back pain (SBP) over six- and 12-month periods. Diffusion data from individuals with CBP and healthy controls (HC) were analyzed for comparison. Whole-brain tract-based spatial statistics analyses revealed that a cluster in the right superior longitudinal fasciculus (SLF) tract had larger fractional anisotropy (FA) values in patients who recovered (SBPr) compared to those with persistent pain (SBPp), and predicted changes in pain severity. The SLF FA values accurately classified patients at baseline and follow-up in a third publicly available dataset (Area under the Receiver Operating Curve ~ 0.70). Notably, patients who recovered had FA values larger than those of HC suggesting a potential role of SLF integrity in resilience to CBP. Structural connectivity-based models also classified SBPp and SBPr patients from the three data sets (validation accuracy 67%). Our results validate the right SLF as a robust predictor of CBP development, with potential for clinical translation. Cognitive and behavioral processes dependent on the right SLF, such as proprioception and visuospatial attention, should be analyzed in subacute stages as they could prove important for back pain chronicity.

Effects of Disturbed Body Perception on Arm Function in Patients With Frozen Shoulder

Purpose Considering pain-related beliefs, this study aimed to investigate the influence of disturbed body perception on arm function in patients with frozen shoulder (FS). Methods This study included 90 patients with FS who visited the orthopedic outpatient clinic. We recorded measurements including the Visual Analog Scale (VAS) for pain at rest and during movement, the quick disability of the arm, shoulder, and hand (QDASH) questionnaire for perceived arm function, the short version of the Pain Self-Efficacy Questionnaire-2 (PSEQ-2) for self-efficacy in pain, the short version of the Pain Catastrophizing Scale (PCS-6) for catastrophic thoughts about pain, the short version of the Tampa Scale for Kinesiophobia (TSK-11) for fear of movement, and the Fremantle Shoulder Awareness Questionnaire (FreSHAQ) for disturbed perception around the shoulder. For statistical analysis, we constructed three models. Model 1 used the QDASH score as the dependent variable, with gender, age, duration of disease onset, VAS score at rest, and VAS score during movement as control variables. Model 2 included pain-related beliefs (PSEQ-2, PCS-6, and TSK-11) added to the variables in Model 1. Model 3 further included the FreSHAQ to the variables in Model 2. We calculated the difference in the adjusted coefficients of determination (R² adj) from Model 1 to Model 2 and Model 3 to determine the amount of change (ΔR² adj). Additionally, we calculated the standardized regression coefficient (β-value) of the input factors to examine their effects. Result Hierarchical multiple regression analysis showed a ΔR² adj of 0.13 and 0.17 for Models 2 and 3, respectively, indicating an increase in ΔR²adj after adding the FreSHAQ. Furthermore, the FreSHAQ had the largest effect of all factors, with β = 0.27 (p<0.05). Conclusions The influence of disturbed body perception on perceived arm function in patients with FS was demonstrated, suggesting the importance of considering somatosensory factors in clinical practice.

Pain and temporality: a merleau-pontyian approach

Chronic pain is a common disorder with enormous sociomedical importance. A major part of primary and secondary costs of illness is caused by the various pain syndromes. Nociception - the sensory perception of a painful stimulus - is a complex process relying on an intricate system of anatomical, neurophysiological and biochemical networks. This applies even more so to pain - the state of experiencing a nociceptive event, of interpreting it in terms of meaning for the affected individual and of suffering a range of emotions it elicits. This intricacy renders it obvious, that the empirical medical sciences alone cannot explain all aspects of pain. Hence, it has also become a focus of phenomenological research. One aspect of these investigations is the interaction of pain and the perception of the lived body's spatiality. The focus of this article will build on these concepts to develop a construct of the alteration of temporality caused by chronic pain and the effects this spells out for the affected subject. To this end, I will primarily draw on Merleau-Ponty's ideas of the lived body as well as on theories of enactivism and embodiment. I will also point out parallels to neuroscientific data, thereby demonstrating the proximity of phenomenology and neuroscience. A possible partial solution to the pain dilemma may be derived from psychology: techniques relying on cognitive behavioural intervention, awareness training, and existential analysis may provide alleviation to patients suffering from chronic pain.

Cervical and Thoracic Spine Mobility in Rotator Cuff Related Shoulder Pain: A Comparative Analysis with Asymptomatic Controls

Rotator cuff related shoulder pain (RCRSP) is a prevalent clinical presentation characterized by substantial diagnostic uncertainty. Some of this uncertainty relates to the involvement of the cervical and thoracic spine as a source of or contributing factor to RCRSP. Thirty-two RCRSP cases and thirty-two asymptomatic controls (AC), recruited from Hospital La Paz-Carlos III between March 2023 and September 2023, were matched for age, gender and hand dominance. Assessed variables included cervical, thoracic range of motion (ROM) and neck disability index (NDI). Independent t-tests were used to compare each of these measurements and multiple linear regression was used to examine the capacity of neck or psychosocial variables to predict the variability of the NDI. The RCRSP group had significantly reduced cervical rotation [RCRSP (111.14 ± 22.98); AC (130.23 ± 21.20), d = 0.86, p < 0.01] and flexo-extension ROM [RCRSP (112.47 ± 2.07); AC (128.5 ± 17.85), d = 0.80, p < 0.01] as well as thoracic spine flexion [RCRSP (33.02 ± 1.14); AC (34.14 ± 1.01), d = 1.04, p < 0.01], extension [RCRSP (28.63 ± 0.89); AC (27.37 ± 0.89), d = -1.40, p < 0.01], right rotation [RCRSP (40.53 ± 10.39); AC (54.45 ± 9.75), d = 1.38, p < 0.01], left rotation [RCRSP (39.00 ± 11.26); AC (54.10 ± 10.51), d = 1.39, p < 0.01] and a significantly increased NDI score [RCRSP (17.56 ± 7.25); AC (2.47 ± 3.25), d = -2.69, p < 0.01]. The variables best explaining neck disability were central sensitization index and SF-12 total score (adjusted R2 = 0.75; p < 0.01). These results suggest that clinicians should assess cervical and thoracic spine mobility in patients with RCRSP.

TNFR1/p38αMAPK signaling in Nex + supraspinal neurons regulates estrogen-dependent chronic neuropathic pain

Upregulation of soluble tumor necrosis factor (sTNF) cytokine signaling through TNF receptor 1 (TNFR1) and subsequent neuronal hyperexcitability are observed in both animal models and human chronic neuropathic pain (CNP). Previously, we have shown that estrogen modulates sTNF/TNFR1 signaling in CNP, which may contribute to female prevalence of CNP. The estrogen-dependent role of TNFR1-mediated supraspinal neuronal circuitry in CNP remains unknown. In this study, we interrogated the intersect between supraspinal TNFR1 mediated neuronal signaling and sex specificity by selectively removing TNFR1 in Nex + neurons in adult mice (NexCreERT2::TNFR1f/f). We determined that mechanical hypersensitivity induced by chronic constriction injury (CCI) decreases over time in males, but not in females. Subsequently, we investigated two downstream pathways, p38MAPK and NF-κB, important in TNFR1 signaling and injury response. We detected p38MAPK and NF-κB activation in male cortical tissue; however, p38MAPK phosphorylation was reduced in NexCreERT2::TNFR1f/f males. We observed a similar recovery from acute pain in male mice following CCI when p38αMAPK was knocked out of supraspinal Nex + neurons (NexCreERT2::p38αMAPKf/f), while chronic pain developed in female mice. To explore the intersection between estrogen and inflammation in CNP we used a combination therapy of an estrogen receptor β (ER β) inhibitor with a sTNF/TNFR1 or general p38MAPK inhibitor. We determined both combination therapies lends therapeutic relief to females following CCI comparable to the response evaluated in male mice. These data suggest that TNFR1/p38αMAPK signaling in Nex + neurons in CNP is male-specific and lack of therapeutic efficacy following sTNF inhibition in females is due to ER β interference. These studies highlight sex-specific differences in pathways important to pain chronification and elucidate potential therapeutic strategies that would be effective in both sexes.

Unraveling the Left-Right Judgment Task in Chronic Low Back Pain: Insights Through Behavioral, Electrophysiological, Motor Imagery, and Bodily Disruption Perspectives

Bodily disruptions have been consistently demonstrated in individuals with chronic low back pain. The performance on the left-right judgment task has been purposed as an indirect measure of the cortical proprioceptive representation of the body. It has been suggested to be dependent on implicit motor imagery, although the available evidence is conflicting. Hence, the aim of this case-control observational study was to examine the performance (accuracy and reaction times) and event-related potentials while performing the left-right judgment task for back and hand images in individuals with chronic low back pain versus healthy controls, along with its relationship with self-reported measurements and quantitative sensory testing. While self-reported data suggested bodily disruptions in the chronic low back pain sample, this was not supported by quantitative sensory testing. Although both groups displayed the same performance, our results suggested an increased attentional load on participants with chronic low back pain to achieve equal performance, measured by a higher N1 peak amplitude in occipital electrodes, especially when the effect of contextual images arises. The absence of differences in the reaction times for the left-right judgment task between both groups, along with inconsistencies in self-reported and quantitative sensory testing data, could question the involvement of implicit motor imagery in solving the task. In conclusion, our results suggest disrupted attentional processing in participants with chronic low back pain to solve the left-right judgment task. PERSPECTIVE: Although there are no differences in the performance of the left-right judgment task (hits, reaction times) between chronic low back pain patients and controls, the analysis of event-related potentials revealed that patients require a higher cognitive load, measured by N1 peak amplitude.

Assessment of Temporal Somatosensory Discrimination in Females with Fibromyalgia: Reliability and Discriminative Ability of a New Assessment Tool

We assessed the test-retest reliability and discriminative ability of a somatosensory temporal discrimination (SSTD) assessment tool for fibromyalgia syndrome (FMS) and determined if pain-related variables were associated with SSTD performance. Twenty-five women with FMS and twenty-five asymptomatic women were assessed during two sessions 7 to 10 days apart. The proportion of correct responses (range 0-100) was calculated. Sociodemographic information was collected for both groups. The participants with FMS also completed the widespread pain index and the Brief Pain Inventory. Test-retest reliability was verified by calculating intraclass correlation coefficients. Discriminative ability was verified by a between-group comparison of scores using a t-test. Associations between SSTD score and pain variables were tested using Pearson or Spearman correlation coefficients. The test-retest reliability of the SSTD score was excellent (ICC > 0.9, CI: 0.79-0.96) for the asymptomatic group and good for the FMS group (ICC: 0.81, 95% CI: 0.62-0.91). The median (Q1-Q3) test session SSTD score differed significantly between the FMS 84.1 (71-88) and the asymptomatic 91.6 (83.4-96.1) groups (p < 0.001). Only pain duration was associated with the SSTD score. In conclusion, the new SSTD test seems reliable for people with FMS and is discriminative. Further studies should examine its sensitivity to change and correlations with other SSTD tests.

Patients' experiences of treatment-relevant processes in multimodal pain rehabilitation for severe complex regional pain syndrome - a qualitative study

PURPOSE

Complex regional pain syndrome (CRPS) is a longstanding condition with spontaneous and evoked pain, that usually occurs in an upper or lower extremity. Although it often resolves within the first year, it may for a minority progress to a chronic and occasionally severely disabling condition. The aim of this study was to explore patients' experiences and perceived effects of a specific treatment, designed for patients with severe and highly disabling CRPS, in order to identify possible treatment-relevant processes.

METHODS

The method used was a qualitative design, using semi-structured interviews with open-ended questions to capture participants' experiences and perceptions. Ten interviews were analyzed using applied thematic analysis.

RESULTS

Despite the fact that participants had a severe conditions, including nerve damage and a long duration of illness, they reported having been helped to increase flexible persistence, reduce fear and avoidance, and improve connections. This helped participants to significant improvements in daily life functioning.

CONCLUSIONS

The participants described distinct possible treatment-relevant processes leading to a substantial improvement in everyday life. The results imply that there is hope for this group that has been severely disabled for many years. This may help guide future clinical treatment trials.

Altered brain function and structure in carpal tunnel syndrome: a systematic review and meta-analysis of structural and functional brain imaging

This systematic review with a meta-analysis aimed to identify the altered brain structure and function in carpal tunnel syndrome (CTS) by summarizing the literature about magnetic resonance imaging (MRI), functional magnetic resonance imaging (fMRI), and magnetoencephalography (MEG) outcomes compared to healthy controls (HC). CTS is the most common nerve entrapment in the arm associated with altered peripheral and central nociceptive system. PRISMA guidelines were used to report the outcomes. Six databases were searched for relevant literature (Web of Science, Scopus, PubMed, Sage, EBSCO host, and Cochrane). Eligible studies comparing MRI, fMRI, and MEG findings in people with CTS (present for at least 2 months) and HC through the following parameters: (1) interdigit cortical separation distance, (2) white and grey matter changes, (3) peak latency of M20 wave and recovery function of N20 from the somatosensory cortex (SI), and (4) surface area of activated digit cortical representation. The results from different studies were pooled and a meta-analysis was done. From 17 included, there was a significant reduction of interdigit cortical separation distance of index-middle and index-little fingers in the CTS (SMD = - 0.869, 95% CI (- 1.325, - 0.413), p-value = 0.000) and (SMD = - 0.79, 95% CI (- 1.217, - 0.364), p-value = 0.000), respectively. Middle-little fingers interdigit separation showed no difference (SMD = - 0.2, 95% CI (- 0.903, 1.309), p-value = 0.718). There is evidence supporting the altered brain structure and function in CTS as evidenced by reduction of interdigit cortical separation distance, and excessive blurring and disinhibition of SI, with low resting state functional connectivity. Thus, centrally directed therapeutic approaches might complement peripheral treatments.

Beyond traditional therapies: a network meta-analysis on the treatment efficacy for chronic phantom limb pain

BACKGROUND

Phantom limb pain (PLP) frequently affects individuals with limb amputations. When PLP evolves into its chronic phase, known as chronic PLP, traditional therapies often fall short in providing sufficient relief. The optimal intervention for chronic PLP remains unclear.

OBJECTIVE

The objectives of this network meta-analysis (NMA) were to examine the efficacy of different treatments on pain intensity for patients with chronic PLP.

EVIDENCE REVIEW

We searched Medline, EMBASE, Cochrane CENTRAL, Scopus, and CINAHL EBSCO, focusing on randomized controlled trials (RCTs) that evaluated interventions such as neuromodulation, neural block, pharmacological methods, and alternative treatments. An NMA was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The primary outcome was pain score improvement, and the secondary outcomes were adverse events.

FINDINGS

The NMA, incorporating 12 RCTs, indicated that neuromodulation, specifically repetitive transcranial magnetic stimulation, provided the most substantial pain improvement when compared with placebo/sham groups (mean difference=-2.9 points, 95% CI=-4.62 to -1.18; quality of evidence (QoE): moderate). Pharmacological intervention using morphine was associated with a significant increase in adverse event rate (OR=6.04, 95% CI=2.26 to 16.12; QoE: low).

CONCLUSIONS

The NMA suggests that neuromodulation using repetitive transcranial magnetic stimulation may be associated with significantly larger pain improvement for chronic PLP. However, the paucity of studies, varying patient characteristics across each trial, and absence of long-term results underscore the necessity for more comprehensive, large-scale RCTs.

PROSPERO REGISTRATION NUMBER

CRD42023455949.

Comparison of head posture and neck proprioceptive sense of individuals with chronic neck pain and healthy controls: A cross-sectional study

BACKGROUND

Chronic pain can affect body perception at the central level by causing the somatosensory cortex to rearrange. Additionally, cervical afferent abnormalities in individuals with neck pain can impair proprioceptive sensitivity, potentially leading to alterations in body alignment and biomechanics. Nevertheless, there are insufficient studies exploring these notions.

OBJECTIVE

The main objective of this study was to compare the head posture and neck proprioceptive sense of individuals with chronic neck pain and healthy controls.

METHODS

Utilizing a cross-sectional study, a total of 76 volunteers comprising 38 individuals with neck pain and 38 matched healthy controls participated in the study. Head posture and cervical joint position sense were measured using a Cervical Range of Motion Deluxe (CROM) device. Firstly, the deviation angles of the head in three planes were evaluated, then the Head Repositioning Accuracy (HRA) test was performed to determine the joint position error. Visual Analogue Scale (VAS) was used to determine the severity of pain in individuals with neck pain.

RESULTS

The deviation angles of the head in all three planes were significantly lower in the healthy control group (p< 0.05). Joint position error values were significantly higher in all directions (flexion-extension, right-left lateral flexion, and rotation) in the neck pain group (p< 0.001).

CONCLUSION

The findings show that the proprioceptive sensation of the cervical region in individuals with neck pain was adversely affected, with changes were observed in the head posture.

NOTE

The abstract of this study was presented as a verbal declaration at the International Congress of Health Sciences-ICHES-IDU 2020 that was held in İzmir on 20-21 June 2020.

Not a general, symptom-unspecific, transdiagnostic marker for functional symptoms: sensorimotor processing of head control is intact in chronic pain

Introduction

Functional disorders are prevalent in all medical fields and pose a tremendous public health problem, with pain being one of the most common functional symptoms. Understanding the underlying, potentially unifying mechanism in functional (pain) disorders is instrumental in facilitating timely diagnosis, stigma reduction, and adequate treatment options. Neuroscientific models of perception suggest that functional symptoms arise due to dysregulated sensorimotor processing in the central nervous system, with brain-based predictions dominating the eventual percept. Experimental evidence for this transdiagnostic mechanism has been established in various functional symptoms. The goal of the current study was to investigate whether erroneous sensorimotor processing is an underlying transdiagnostic mechanism in chronic (functional) pain.

Method

A total of 13 patients with chronic (functional) pain [three patients with chronic (functional) pain disorder, F45.40, ICD-10; 10 patients with chronic pain disorder with somatic and psychological factors, F45.41, ICD-10]; and 15 healthy controls performed large combined eye-head gaze shifts toward visual targets, naturally and with increased head moment of inertia. We simultaneously measured participants' eye and head movements to assess head oscillations at the end of the gaze shift, which are an established indicator of (transdiagnostic) sensorimotor processing deficits of head control.

Results

Using a Bayesian analysis protocol, we found that patients with chronic (functional) pain and control participants stabilized their heads equally well (Bayes Factor 01 = 3.7, Bayes Factor exclusion = 5.23; corresponding to substantial evidence) during all sessions of the experiment.

Conclusion

Our results suggest that patients with chronic (functional) pain do not show measurable symptom-unspecific sensorimotor processing deficits. We discuss outcome parameter choice, organ system specificity, and selection of patient diagnoses as possible reasons for this result and recommend future avenues for research.

A single session of action observation therapy versus observing a natural landscape in adults with chronic neck pain - a randomized controlled trial

BACKGROUND

Action observation (AO) has emerged as a potential neurorehabilitation therapy for patients with neck pain (NP), but evidence of its effectiveness is scarce. This study aims to assess the effect of a single session of AO when compared to observing a natural landscape on NP intensity, fear of movement, fear-avoidance beliefs, neck muscles' strength, pressure pain threshold, and tactile acuity.

METHODS

Sixty participants with NP were randomly allocated to the AO group (n = 30) or control group (n = 30). Both groups watched an 11-minute video: the AO group watched a video of a person matched for age and sex performing neck exercises, while the control group watched a video of natural landscapes. Neck pain intensity, fear of movement, fear-avoidance beliefs, tactile acuity, pressure pain thresholds, and neck muscle strength were assessed both at baseline and post-intervention. General linear models of repeated measures (ANCOVA of two factors) were used to explore between-group differences at post-intervention.

RESULTS

There was a significant main effect of time for pain intensity (p = 0.02; η2p = 0.09; within-group mean change and 95% CI: AO=-1.44 (-2.28, -0.59); control=-1.90 (-2.74, -1.06), but no time versus group interaction (p = 0.46). A time versus group significant interaction was found for one out of the six measurement sites of two-point discrimination and the neck flexors strength (p < 0.05) favoring the control group. No other statistically significant differences were found for the remaining variables).

CONCLUSIONS

Results suggest a similar acute benefit for both a single session of AO and observing natural landscapes for promoting hypoalgesia, but no impact on kinesiophobia, fear-avoidance beliefs, or pressure pain thresholds. Also, AO had no positive effect on two-point discrimination and muscle strength. Further research is needed, with longer interventions.

TRIAL REGISTRATION

Clinialtrials.gov (NCT05078489).

The effects of basic body awareness therapy on balance in patients with chronic neck pain: a randomised crossover trial

PURPOSE

This study aimed to compare the effects of basic body awareness therapy (BBAT) and conventional treatments (CT) on balance in patients with chronic neck pain.

METHODS

Thirty-five patients with neck pain participated in this randomised two-period crossover trial. Patients were divided into A (BBAT/CT) (n = 17) and B (CT/BBAT) (n = 18) groups. Group A received BBAT twice a week for 6 weeks, whereas Group B received CT within the same parameters. After a 5-week washout period, the treatments received by the groups were changed. The primary outcome was balance, assessed via the sensory organisation test (SOT) using the computerised dynamic posturography device. The secondary outcome was pain assessed by the visual analogue scale. Assessments were performed before and after primary and secondary treatments.

RESULTS

In Group A, the SOT conditions 4, 5, 6; composites score; and visual and vestibular system scores increased after BBAT; however, only condition five scores and vestibular system scores increased (p < .05) in Group B, which started with CT. Within the groups, both treatments were effective for easing pain (p < .05).

CONCLUSIONS

Although patients who started the therapy with BBAT showed more improvement in balance, no differences were observed between the therapies.

Low frequency oscillations during hand laterality judgment task with and without personal perspectives: a preliminary study

Sense of personal perspective is crucial for understanding in attentional mechanisms of the perception in "self" or "other's" body. In a hand laterality judgment (HLJ) task, perception of perspective can be assessed by arranging angular orientations and depths of images. A total of 11 healthy, right-handed participants (8 females, mean age: 38.36 years, education: 14 years) were included in the study. The purpose of this study was to investigate behavioural and cortical responses in low-frequency cortical rhythms during a HLJ task. A total of 80-visual hand stimuli were presented through the experiment. Hand visuals were categorized in the way of side (right vs. left) and perspective (1st vs. 3rd personal perspective). Both behavioural outcomes and brain oscillatory characteristics (i.e., frequency and amplitude) of the Electroencephalography were analysed. All reaction time and incorrect answers for 3rd person perspective were higher than the ones for 1st person perspective. Location effect was statistically significant in event-related theta responses confirming the dominant activity of theta frequency in spatial memory tasks on parietal and occipital areas. In addition, we found there were increasing in delta power and phase in hand visuals with 1st person perspective and increasing theta phase in hand visuals with 3rd person perspective (p < 0.05). Accordingly, a clear dissociation in the perception of perspectives in low-frequency bands was revealed. These different cortical strategy in the perception of hand visual with and without perspectives may be interpreted as delta activity may be related in self-body perception, whereas theta activity may be related in allocentric perception.

Mechanisms of education and graded sensorimotor retraining in people with chronic low back pain: a mediation analysis

ABSTRACT

An improved understanding of the biopsychosocial influences that contribute to and maintain pain has promoted the development of new efficacious treatments for chronic low back pain (CLBP). This study aimed to investigate the mechanisms of a new treatment-education and graded sensorimotor retraining-on pain and disability. We conducted a preplanned causal mediation analysis of a randomized clinical trial which allocated 276 participants with CLBP to 12 weekly clinical sessions of education and graded sensorimotor retraining (n = 138) or a sham and attention control (n = 138). Outcomes were pain intensity and disability, both assessed at 18 weeks. Hypothesized mediators included tactile acuity, motor coordination, back self-perception, beliefs about the consequences of back pain, kinesiophobia, pain self-efficacy, and pain catastrophizing, all assessed at the end of treatment (12 weeks). Four of 7 mechanisms (57%) mediated the intervention effect on pain; the largest mediated effects were for beliefs about back pain consequences (-0.96 [-1.47 to -0.64]), pain catastrophizing (-0.49 [-0.61 to -0.24]), and pain self-efficacy (-0.37 [-0.66 to -0.22]). Five of 7 mechanisms (71%) mediated the intervention effect on disability; the largest mediated effects were for beliefs about back pain consequences (-1.66 [-2.62 to -0.87]), pain catastrophizing (-1.06 [-1.79 to -0.53]), and pain self-efficacy (-0.84 [-1.89 to -0.45]). When all 7 mechanisms were considered simultaneously, the joint mediation effect explained most of the intervention effect for both pain and disability. Optimizing interventions to target beliefs about the consequences of back pain, pain catastrophizing, and pain self-efficacy is likely to lead to improved outcomes for people with CLBP.

Inter- and Intra-Examiner Reliability Study of Two-Point Discrimination Test (TPD) and Two-Point Estimation Task (TPE) in the Sacral Area of Pain-Free Individuals

Tactile acuity is typically measured by a two-point discrimination test (TPD) and a two-point estimation task (TPE). In the back area, they are only conducted in the lumbar and cervical regions of the spine. Considering that such measurements have not been conducted in the sacral regions, the purpose of this study was to assess the inter- and intra-examiner reliability of the TPD and TPE at the level of the S3 segment. The study included 30 pain-free subjects aged 20-30 years. Tests were performed with a pair of stainless hardened digital calipers. The TPD was measured in two locations: 5 and 15 cm from the midline; for TPE both, points were located inside the measured area. Session 1 involved assessments by two examiners in 10-min intervals. Session 2 was measured by one examiner, at analogous intervals between tests. The TPD inter-rater reliability was excellent for mean measurements (ICC3.2: 0.76-0.8; ICC3.3: 0.8-0.92); the intra-rater reliability was excellent for mean measurements (ICC2.2: 0.79-0.85; ICC2.3: 0.82-0.86). The TPE inter-rater reliability was good to excellent for mean measurements (ICC3.2: 0.65-0.92; ICC3.3: 0.73-0.94); the intra-rater reliability for all studies (ICC2.1, ICC2.2, ICC2.3) was excellent (0.85-0.89). Two measurements are sufficient to achieve good reliability (ICC ≥ 0.75), regardless of the assessed body side.

Regional vs global physical therapy interventions to treat chronic pain in survivors of trauma: a randomized controlled trial

BACKGROUND

A history of traumatic life events is associated with chronic pain in later life. Physical therapists utilize a variety of methods to treat pain, however, they have struggled to find effective interventions to improve patient outcomes.

OBJECTIVE

To compare impairment-based, regional (REGION-PT) physical therapy (PT) to a global (GLOBAL-PT) model consisting of pain neuroscience education, graded motor imagery, and exercise for adults with chronic pain and history of trauma.

DESIGN

Randomized Controlled Trial.

METHODS

Adults ≥ 18 years of age with chronic pain and a history of ≥1 trauma identified through the Life Events Checklist received the allocated intervention once a week for six weeks. Treatment effects were assessed using linear mixed models.

RESULTS

Ninety-eight participants completed the trial. There were no difference in outcomes between groups. There were significant interactions between race and intervention. Both interventions were associated with improvements in pain interference for white participants, but non-white participants experienced improvement only with GLOBAL-PT. Regardless of allocation, participants improved in physical function, six of the PROMIS-29 domains, and in pain interference measures.

CONCLUSION

Both interventions are reasonable strategies for individuals with chronic pain and a history of trauma.

Lifeworlds in pain: a principled method for investigation and intervention

The experience of pain spans biological, psychological and sociocultural realms, both basic and complex, it is by turns necessary and devastating. Despite an extensive knowledge of the constituents of pain, the ability to translate this into effective intervention remains limited. It is suggested that current, multiscale, medical approaches, largely informed by the biopsychosocial (BPS) model, attempt to integrate knowledge but are undermined by an epistemological obligation, one that necessitates a prior isolation of the constituent parts. To overcome this impasse, we propose that an anthropological stance needs to be taken, underpinned by a Bayesian apparatus situated in computational psychiatry. Here, pain is presented within the context of lifeworlds, where attention is shifted away from the constituents of experience (e.g. nociception, reward processing and fear-avoidance), towards the dynamic affiliation that occurs between these processes over time. We argue that one can derive a principled method of investigation and intervention for pain from modelling approaches in computational psychiatry. We suggest that these modelling methods provide the necessary apparatus to navigate multiscale ontology and epistemology of pain. Finally, a unified approach to the experience of pain is presented, where the relational, inter-subjective phenomenology of pain is brought into contact with a principled method of translation; in so doing, revealing the conditions and possibilities of lifeworlds in pain.

Widespread Proprioceptive Acuity Impairment in Chronic Back Pain: A Cross-sectional Study

OBJECTIVE

To investigate whether proprioceptive accuracy measured with the Joint Position Sense (JPS) in patients with chronic neck and low back pain is impaired exclusively in affected areas or also in distant areas, not affected by pain.

DESIGN

Cross-sectional study.

SETTING

Interdisciplinary outpatient rehabilitation clinic for back and neck pain.

PARTICIPANTS

Patients with chronic neck pain (n=30), patients with chronic low back pain (n=30), and age- and sex-matched asymptomatic control subjects (n=30; N=90).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Patients and asymptomatic control subjects completed a test procedure for the JPS of the cervical spine, lumbar spine, and ankle in a randomized order. Between group differences were analyzed with the univariate analysis of variance and associations of the JPS with clinical features using the Pearson's correlation coefficient.

RESULTS

Both patients with chronic neck pain (P<.001) and patients with chronic low back pain (P<.01) differed significantly from asymptomatic controls in the JPS of the cervical spine, lumbar spine and ankle joint, regardless of the painful area. No difference was shown between patient groups (P>.05). An association of the JPS with clinical characteristics, however, could not be shown.

CONCLUSION

These results suggest widespread impairment of proprioceptive accuracy in patients with chronic and low back pain and a role for central sensorimotor processes in musculoskeletal pain conditions.

Are clinical outcomes associated with baseline sensory profiles in people with musculoskeletal shoulder pain? Protocol for a prospective longitudinal observational study

BACKGROUND

Musculoskeletal shoulder pain is a common problem and its symptoms often become persistent. The experience of pain is multidimensional, and therefore, a range of patient characteristics may influence treatment response. An altered sensory processing has been associated with persistent musculoskeletal pain states and may contribute to outcomes in patients with musculoskeletal shoulder pain. The presence and potential impact of altered sensory processing in this patient cohort is not currently known. The aim of this prospective longitudinal cohort study is to investigate if baseline sensory characteristics are associated with clinical outcomes in patients presenting to a tertiary hospital with persistent musculoskeletal shoulder pain. If found, a relationship between sensory characteristics and outcome may lead to the creation of more effective treatment strategies and improvements in risk adjustment and prognosis.

METHODS

This is a single-centre prospective cohort study with 6-, 12- and 24-month follow-up. A total of 120 participants aged ≥18 years with persistent musculoskeletal shoulder pain (≥3 months) will be recruited from an Australian public tertiary hospital orthopaedic department. Baseline assessments, including quantitative sensory tests and a standardised physical examination, will be performed. In addition, information will be obtained from patient interviews, self-report questionnaires and medical records. Follow-up outcome measures will comprise information from the Shoulder Pain and Disability Index and a six-point Global Rating of Change scale.

ANALYSIS

Descriptive statistics will be used to report baseline characteristics and outcome measures over time. Change in outcome measures at the primary endpoint of six months from baseline will be calculated using paired t-tests. Associations between baseline characteristics and outcomes at a 6-month follow-up will be reported using multivariable linear and logistic regression models.

DISCUSSION

Understanding the relationship between sensory profile and the variable response to treatment in people with persistent musculoskeletal shoulder pain may enhance our understanding of the mechanisms contributing to the presentation. In addition, through better understanding of the contributing factors, the results of this study may contribute to the development of an individualised, patient-centred approach to treatment for people with this highly prevalent and debilitating condition.

TNFR1/p38αMAPK signaling in Nex+ supraspinal neurons regulates sex-specific chronic neuropathic pain

Upregulation of soluble tumor necrosis factor (sTNF) cytokine signaling through TNF receptor 1 (TNFR1) and subsequent neuronal hyperexcitability are observed in both animal models and human chronic neuropathic pain (CNP) [1-4]. To test the hypothesis that supraspinal circuitry is critical to pain chronification, we studied the intersect between supraspinal TNFR1 mediated neuronal signaling and sex specificity by selectively removing TNFR1 in Nex + neurons in adult mice (NexCreERT2::TNFR1f/f). We determined that following chronic constriction injury (CCI), pain resolves in males; however, female acute pain transitions to chronic. Subsequently, we investigated two downstream pathways, p38MAPK and NF-κB, important in TNFR1 signaling and injury response. We detected p38αMAPK and NF-κB activation in male cortical tissue; however, p38αMAPK phosphorylation was reduced in NexCreERT2::TNFR1f/f males. We observed similar behavioral results following CCI in NexCreERT2::p38αMAPKf/f mice. Previously, we established estrogen's ability to modulate sTNF/TNFR1 signaling in CNP, which may contribute to female prevalence of CNP [5-9]. To explore the intersection between estrogen and inflammation in CNP we used a combination therapy of an estrogen receptor β (ER β) inhibitor with a sTNF/TNFR1 or general p38MAPK inhibitor. We determined both combination therapies lend "male-like" therapeutic relief to females following CCI. These data suggest that TNFR1/p38αMAPK signaling in Nex + neurons in CNP is male-specific and lack of therapeutic efficacy following sTNF inhibition in females is due to ER β interference. These studies highlight sex-specific differences in pathways important to pain chronification and elucidate potential therapeutic strategies that would be effective in both sexes.

Does graded motor imagery benefit individuals with knee pain: A systematic review and meta-analysis

OBJECTIVE

Evaluate how Graded Motor Imagery (GMI) may be used in those with knee pain, if individuals with knee pain present with a central nervous system (CNS) processing deficit, and if GMI is associated with improved outcomes.

METHODS

An electronic database search was conducted of PubMed, SPORTDiscus, CINHAL, MEDLINE, Google Scholar, and Sports Medicine Education Index using keywords related to GMI and knee pain. This review was reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Out of the 13,224 studies reviewed, 14 studies were included that used GMI for knee pain. Effect sizes were reported with standardized mean differences (SMD).

RESULTS

Individuals with knee osteoarthritis demonstrated poor performance with correctly identifying images of left or right knees, and GMI improved performance. In contrast, individuals with an anterior cruciate ligament injury demonstrated no evidence of CNS processing deficit and mixed outcomes with GMI. Meta-analysis was limited to individuals post total knee arthroplasty showing low certainty that GMI can improve quadriceps force production [SMD 0.64 (0.07,1.22)], but evidence of no effect to reduce pain or improve Timed up and Go performance and self-reported function.

CONCLUSIONS

Graded motor imagery may be an effective intervention for individuals with knee osteoarthritis. However, there was limited evidence that GMI was effective for an anterior cruciate ligament injury.

The Biology of Chronic Pain and Its Implications for Pain Neuroscience Education: State of the Art

Pain is an individualized experience for the person suffering from chronic pain. Significant strides have been made in the last few decades in understanding various biological changes that coincide with chronic pain. This state-of-the-art overview looks at the current evidence related to the biology of chronic pain and the implications these findings have on the delivery of pain neuroscience education (PNE). The paper summarizes the various (epi)genetic, neural, endocrine, and immune factors discovered and explored in the scientific literature concerning chronic pain. Each of these biological factors has various implications for the content and delivery of PNE. We discuss the future directions these biological factors have for the clinical implementation of PNE by linking the importance of behavior change, optimizing the learning environment, and using an individualized multimodal treatment approach with PNE. In addition, future directions for research of PNE based on these biological factors are provided with importance placed on individualized patient-centered care and how PNE can be used with traditional modes of care and growing trends with other care methods. PNE was originally and continues to be rooted in understanding chronic pain biology and how that understanding can improve patient care and outcomes.

Interventions for treating pain and disability in adults with complex regional pain syndrome- an overview of systematic reviews

BACKGROUND

Complex regional pain syndrome (CRPS) is a chronic pain condition that usually occurs in a limb following trauma or surgery. It is characterised by persisting pain that is disproportionate in magnitude or duration to the typical course of pain after similar injury. There is currently no consensus regarding the optimal management of CRPS, although a broad range of interventions have been described and are commonly used. This is the first update of the original Cochrane review published in Issue 4, 2013.

OBJECTIVES

To summarise the evidence from Cochrane and non-Cochrane systematic reviews of the efficacy, effectiveness, and safety of any intervention used to reduce pain, disability, or both, in adults with CRPS.

METHODS

We identified Cochrane reviews and non-Cochrane reviews through a systematic search of Ovid MEDLINE, Ovid Embase, Cochrane Database of Systematic Reviews, CINAHL, PEDro, LILACS and Epistemonikos from inception to October 2022, with no language restrictions. We included systematic reviews of randomised controlled trials that included adults (≥18 years) diagnosed with CRPS, using any diagnostic criteria.  Two overview authors independently assessed eligibility, extracted data, and assessed the quality of the reviews and certainty of the evidence using the AMSTAR 2 and GRADE tools respectively. We extracted data for the primary outcomes pain, disability and adverse events, and the secondary outcomes quality of life, emotional well-being, and participants' ratings of satisfaction or improvement with treatment.  MAIN RESULTS: We included six Cochrane and 13 non-Cochrane systematic reviews in the previous version of this overview and five Cochrane and 12 non-Cochrane reviews in the current version. Using the AMSTAR 2 tool, we judged Cochrane reviews to have higher methodological quality than non-Cochrane reviews. The studies in the included reviews were typically small and mostly at high risk of bias or of low methodological quality. We found no high-certainty evidence for any comparison.  There was low-certainty evidence that bisphosphonates may reduce pain intensity post-intervention (standardised mean difference (SMD) -2.6, 95% confidence interval (CI) -1.8 to -3.4, P = 0.001; I2 = 81%; 4 trials, n = 181) and moderate-certainty evidence that they are probably associated with increased adverse events of any nature (risk ratio (RR) 2.10, 95% CI 1.27 to 3.47; number needed to treat for an additional harmful outcome (NNTH) 4.6, 95% CI 2.4 to 168.0; 4 trials, n = 181).  There was moderate-certainty evidence that lidocaine local anaesthetic sympathetic blockade probably does not reduce pain intensity compared with placebo, and low-certainty evidence that it may not reduce pain intensity compared with ultrasound of the stellate ganglion. No effect size was reported for either comparison. There was low-certainty evidence that topical dimethyl sulfoxide may not reduce pain intensity compared with oral N-acetylcysteine, but no effect size was reported. There was low-certainty evidence that continuous bupivacaine brachial plexus block may reduce pain intensity compared with continuous bupivacaine stellate ganglion block, but no effect size was reported. For a wide range of other commonly used interventions, the certainty in the evidence was very low and provides insufficient evidence to either support or refute their use. Comparisons with low- and very low-certainty evidence should be treated with substantial caution. We did not identify any RCT evidence for routinely used pharmacological interventions for CRPS such as tricyclic antidepressants or opioids.

AUTHORS' CONCLUSIONS

Despite a considerable increase in included evidence compared with the previous version of this overview, we identified no high-certainty evidence for the effectiveness of any therapy for CRPS. Until larger, high-quality trials are undertaken, formulating an evidence-based approach to managing CRPS will remain difficult. Current non-Cochrane systematic reviews of interventions for CRPS are of low methodological quality and should not be relied upon to provide an accurate and comprehensive summary of the evidence.

Recovery of pinch force sense after short-term fatigue

The aim of this study was to identify the exact origin of force sense and identify whether it arises centrally or peripherally. The present study was designed to analyze the effects of short-term fatigue on pinch force sense and the duration of these effects. During the fatigue protocol, twenty (10 men and 10 women; Mage = 22.0 years old) young Chinese participants were asked to squeeze maximally until the pinch grip force decreased to 50% of its maximal due to fatigue. Participants were instructed to produce the target force (10% of maximal voluntary isometric contraction) using the same hand before and after fatigue (immediately, 10, 30, 60, 180, 300 s). The results showed significantly higher absolute error immediately after fatigue (1.22 ± 1.06 N) than before fatigue (0.68 ± 0.34 N), and 60 s (0.76 ± 0.69 N), 180 s (0.67 ± 0.42 N), and 300 s (0.75 ± 0.37 N) after fatigue (all P < 0.05) but with no effect on the variable error (P > 0.05). It was also revealed that there was a significant overestimate of the constant error values before (0.32 ± 0.61 N) and immediately after fatigue (0.80 ± 1.38 N, all P < 0.05), while no significant overestimation or underestimation exceeded 300 s after fatigue (P > 0.05). Our study results revealed that short-term fatigue resulted in a significant decrease in force sense accuracy, but it did not affect force sense consistently; however, force sense accuracy recovered to a certain extent within 10 s and 30 s, whereas it recovered fully within 60 s, and force sense directivity improvement exceeded 300 s after fatigue. The present study shows that the sense of tension (peripherally) is also an important factor affecting force sense. Our study supports the view that the periphery is part of the origin of force sense.

Grip force makes wrist joint position sense worse

Background

The purpose of this study was to investigate how grip force affects wrist joint position sense.

Methods

Twenty-two healthy participants (11 men and 11 women) underwent an ipsilateral wrist joint reposition test at 2 distinct grip forces [0 and 15% of maximal voluntary isometric contraction (MVIC)] and 6 different wrist positions (pronation 24°, supination 24°, radial deviation 16°, ulnar deviation 16°, extension 32°, and flexion 32°).

Results

The findings demonstrated significantly elevated absolute error values at 15% MVIC (3.8 ± 0.3°) than at 0% MVIC grip force [3.1 ± 0.2°, t(20) = 2.303, P = 0.032].

Conclusion

These findings demonstrated that there was significantly worse proprioceptive accuracy at 15% MVIC than at 0% MVIC grip force. These results may contribute to a better comprehension of the mechanisms underlying wrist joint injuries, the development of preventative measures to lower the risk of injuries, and the best possible design of engineering or rehabilitation devices.

Primary somatosensory cortex bidirectionally modulates sensory gain and nociceptive behavior in a layer-specific manner

The primary somatosensory cortex (S1) is a hub for body sensation of both innocuous and noxious signals, yet its role in somatosensation versus pain is debated. Despite known contributions of S1 to sensory gain modulation, its causal involvement in subjective sensory experiences remains elusive. Here, in mouse S1, we reveal the involvement of cortical output neurons in layers 5 (L5) and 6 (L6) in the perception of innocuous and noxious somatosensory signals. We find that L6 activation can drive aversive hypersensitivity and spontaneous nocifensive behavior. Linking behavior to neuronal mechanisms, we find that L6 enhances thalamic somatosensory responses, and in parallel, strongly suppresses L5 neurons. Directly suppressing L5 reproduced the pronociceptive phenotype induced by L6 activation, suggesting an anti-nociceptive function for L5 output. Indeed, L5 activation reduced sensory sensitivity and reversed inflammatory allodynia. Together, these findings reveal a layer-specific and bidirectional role for S1 in modulating subjective sensory experiences.

Role of Immersive Virtual Reality in Motor Behaviour Decision-Making in Chronic Pain Patients

Primary chronic pain is a major contributor to disability worldwide, with an estimated prevalence of 20-33% of the world's population. The high socio-economic impact of musculoskeletal pain justifies seeking an appropriate therapeutic strategy. Immersive virtual reality (VR) has been proposed as a first-line intervention for chronic musculoskeletal pain. However, the growing literature has not been accompanied by substantial progress in understanding how VR exerts its impact on the pain experience and what neurophysiological mechanisms might be involved in the clinical effectiveness of virtual reality interventions in chronic pain patients. The aim of this review is: (i) to establish the state of the art on the effects of VR on patients with chronic pain; (ii) to identify neuroplastic changes associated with chronic pain that may be targeted by VR intervention; and (iii) to propose a hypothesis on how immersive virtual reality could modify motor behavioral decision-making through an interactive experience in patients with chronic pain.

The effect of mirror therapy in patients with frozen shoulder

Introduction

This study was designed to compare mirror therapy and visual feedback with the control group in adhesive capsulitis patients.

Methods

Thirty-six patients, divided into three groups as mirror therapy, visual feedback and control for 15 sessions of treatment. Evaluations were made before treatment, at 6th and 10th weeks. Bilateral glenohumeral exercise was performed at the end of each session with the affected extremity behind the mirror in the mirror group, with both upper extremities in front of the mirror in the visual feedback group, and without the mirror in the control group.

Results

There were statistically significant differences between the mirror therapy and visual feedback in terms of pain severity change, and the visual feedback was superior to the change in pain severity compared to the control. Visual feedback showed significant improvement in mean change from baseline to week 10 in shoulder pain and disability index scores compared to control (p = 0.012). There was no significant difference between the groups in terms of modified constant score, proprioception and shoulder range of motion.

Conclusion

It was determined that the exercises performed by seeing the affected extremity in the mirror were more effective than mirror therapy and control group.

Tactile acuity and left/right judgment performance in patients with knee osteoarthritis: A cross-sectional study

BACKGROUND

Left/right judgment task (LRJT) performance and tactile acuity are impaired in chronic pain conditions, however, evidence is limited for knee osteoarthritis (OA).

OBJECTIVE

To compare LRJT performance and the two-point discrimination threshold (TPDT) of chronic knee OA patients with asymptomatic knee and pain-free controls.

DESIGN

Cross-sectional study.

METHODS

Fifty knee OA patients and 50 age and gender-matched pain-free controls were assessed using the Recognize® application by displaying knee images and a digital caliper for the TPDT of the medial and lateral knee joint line.

RESULTS

TPDTs over the lateral joint line in symptomatic (mean difference [MD]: 13.59 mm; 95% confidence interval [CI]: 8.72, 18.46; d = 1.40) and asymptomatic knee (MD: 10.15 mm; 95% CI: 5.08, 15.22; d = 0.99) were significantly increased compared to pain-free controls. Similarly, TPDTs of the medial joint line were significantly increased in symptomatic (MD: 12.19 mm; 95% CI: 7.59, 16.79; d = 1.31) and asymptomatic knee (MD: 7.64 mm; 95% CI: 3.64, 11.64; d = 1.31) compared to pain-free controls. Patients with knee OA were less accurate (MD: 7.80%; 95% CI: 15.32, -0.27; d = 0.52) recognizing images of their symptomatic knee. No correlation was found between pain severity, pain duration, LRJT performance, and TPDTs. Post-hoc analysis revealed no differences in LRJT and TPDTs between patients with and without clinically relevant symptoms of central sensitization.

CONCLUSION

Chronic knee OA is associated with increased TPDT for medial and lateral knee joint lines and decreased recognition accuracy performance which should be considered during treatment process.

Assessment of exercise-induced hypoalgesia in chronic low back pain and potential associations with psychological factors and central sensitization symptoms: A case-control study

INTRODUCTION

Exercise is the most recommended treatment for chronic low back pain (CLBP) and is effective in reducing pain, but the mechanisms underlying its effects remain poorly understood. Exercise-induced hypoalgesia (EIH) may play a role and is thought to be driven by central pain modulation mechanisms. However, EIH appears to be disrupted in many chronic pain conditions and its presence in people with CLBP remains unclear. As people suffering from chronic pain often exhibit psychological factors and central sensitization symptoms influencing pain perception, EIH might be associated with these factors.

OBJECTIVE

The aim of this study is to compare the level of EIH between participants with and without CLBP following back and wrist exercises and to assess the associations between EIH, psychological factors, and symptoms of central sensitization (using the central sensitization inventory - CSI) in CLBP.

METHOD

Twenty-eight participants with CLBP and 23 without pain were recruited. Pressure pain thresholds (PPT) were measured at 4 sites (2 bony sites = capitate, S1|2 muscle sites = wrist flexors, lumbar erector spinae) before and after each of two exercises (wrist flexion and lumbar extension). Exercise-induced hypoalgesia was defined as percent change in PPT from pre- to post-exercise. Participants with CLBP also completed questionnaires to measure psychological factors (e.g., kinesiophobia, catastrophizing, anxiety, and self-efficacy) and symptoms of central sensitization (CSI), and correlations with EIH were calculated.

RESULTS

After wrist exercise, EIH measured at the muscle sites was lower in the CLBP group compared with the pain-free group (p = 0.047) but no differences were found at bony sites (p = 0.49). No significant differences for EIH were observed following back exercise at muscle sites (p = 0.14) or at bony sites (p = 0.65). Exercise-induced hypoalgesia was not correlated with any psychological factors or with the CSI score.

CONCLUSION

The lower EIH following wrist exercises may represent an alteration in pain modulation control in CLBP. However, psychological factors and central sensitization symptoms may not explain the differences observed.

Body image and perception among adults with and without phantom limb pain

BACKGROUND

Following lower-limb amputation, phantom limb pain (i.e., pain perceived as coming from the amputated portion of the limb) is common. Phantom limb pain may be associated with impaired body image and perception, which may be targets for rehabilitative intervention.

OBJECTIVE

To compare measures of body image and perception between adults with and without phantom limb pain post amputation and evaluate associations between measures of body image and perception and phantom limb pain.

DESIGN

Survey.

SETTING

Online, remote assessment.

PARTICIPANTS

Seventy-two adults ≥1 year post unilateral lower-limb loss (n = 42 with phantom limb pain, n = 30 without phantom limb pain or pain in the remaining portion of the limb).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Self-reported outcome measures assessing body image (i.e., Amputee Body Image Scale-Revised), perceptual disturbances associated with the phantom limb (i.e., a modified Bath Complex Regional Pain Syndrome Body Perception Disturbance Scale), and prosthesis satisfaction (i.e., Trinity Amputation and Prosthesis Experience Scale) were administered; participants with phantom limb pain reported pain interference via the Brief Pain Inventory-Short Form. Between-group comparisons of self-reported outcome measure scores were conducted using Mann Whitney U or chi-square tests, as appropriate (a = .05).

RESULTS

Compared to peers without phantom limb pain, adults with phantom limb pain reported more negative body image; increased phantom limb ownership, attention, and awareness; and reduced prosthesis satisfaction and embodiment (U = 175.50-364.00, p < .001 to .034). Disturbances in phantom limb perception (i.e., size, weight, pressure, temperature) were similar between groups (p = .086 to >.999). More negative body image was associated with increased phantom limb pain interference (τb  = .25, p = .026).

CONCLUSIONS

Adults with phantom limb pain demonstrate more negative body image and hypervigilance of the phantom limb as compared to peers with nonpainful phantom sensations. Mind-body treatments that target impaired body image and perception may be critical interventions for adults with phantom limb pain.

Pelvic floor physical therapy and mindfulness: approaches for chronic pelvic pain in women-a systematic review and meta-analysis

PURPOSE

Chronic pelvic pain (CPP) in women is a complex syndrome and symptoms are associated with sexual dysfunction, musculoskeletal and myofascial disorders, and comorbid psychiatric disorders. Its widespread prevalence results in substantial expense due to therapy and lost productivity, and it is perhaps one of the most urgent and neglected medical needs. This systematic review and meta-analysis aimed to estimate the role of mindfulness and pelvic floor physical therapy (PFPT) in the treatment or management of women with CPP.

METHODS

This systematic review (CRD42020204987) searched for relevant publications between January 2000 and November 2020 on MEDLINE/PubMed, Web of Science, One File GALE, and Technology Research databases using the following search terms: chronic pelvic pain, pelvic floor physical therapy/physiotherapy, mindfulness, and their variants. Risk of bias and quality of evidence were evaluated.

RESULTS

Seven clinical trials (n = 279) were included in the review, and five in the meta-analysis (n = 225). For the pain outcome and its catastrophizing, there was a statistical difference for the Pain Catastrophizing Scale after treatment and during follow-up with mindfulness and PFPT (MD = - 3.82 [- 6.97, - 0.68], p = 0.01, and MD = - 4.49 [- 7.61, - 1.37], p = 0.00, respectively). Sexual function, assessed by the female sexual function index, differed significantly during follow-up between PFPT and mindfulness (MD = - 0.72 [- 1.38, - 0.05], p = 0.03).

CONCLUSION

The small number of studies applying both PFPT and mindfulness to CPP suggests that a multidisciplinary approach is required to treat women with CPP, and further studies involving these therapeutic techniques throughout the CPP cycle are needed.

Uncertainty in low back pain care - insights from an ethnographic study

PURPOSE

To explore how uncertainty plays out in low back pain (LBP) care and investigate how clinicians manage accompanying emotions/tensions.

MATERIALS AND METHODS

We conducted ethnographic observations of clinical encounters in a private physiotherapy practice and a public multidisciplinary pain clinic. Our qualitative reflexive thematic analysis involved abductive thematic principles informed by Fox and Katz (medical uncertainty) and Ahmed (emotions).

RESULTS

We identified three themes. (1) Sources of uncertainty: both patients and clinicians expressed uncertainty during clinical encounters (e.g., causes of LBP, mismatch between imaging findings and presentation). Such uncertainty was often accompanied by emotions - anger, tiredness, frustration. (2) Neglecting complexity: clinicians often attempted to decrease uncertainty and associated emotions by providing narrow answers to questions about LBP. At times, clinicians' denial of uncertainty also appeared to deny patients the right to make informed decisions about treatments. (3) Attending to uncertainty?: clinicians attended to uncertainty through logical reasoning, reassurance, acknowledgement, personalising care, shifting power, adjusting language and disclosing risks.

CONCLUSIONS

Uncertainty pervades LBP care and is often accompanied by emotions, emphasising the need for a healthcare culture that recognises the emotional dimensions of patient-clinician interactions and prepares clinicians and patients to be more accepting of, and clearly communicate about, uncertainty.IMPLICATIONS FOR REHABILITATIONUncertainty pervades LBP care and is often accompanied by emotions.Neglecting complexity in LBP care may compromise person-centred care.Acknowledging uncertainty can enhance communication, balance patient-clinician relationships and address human aspects of care.

Mechanism of Action of Peripheral Nerve Stimulation for Chronic Pain: A Narrative Review

The use of stimulation of peripheral nerves to test or treat various medical disorders has been prevalent for a long time. Over the last few years, there has been growing evidence for the use of peripheral nerve stimulation (PNS) for treating a myriad of chronic pain conditions such as limb mononeuropathies, nerve entrapments, peripheral nerve injuries, phantom limb pain, complex regional pain syndrome, back pain, and even fibromyalgia. The ease of placement of a minimally invasive electrode via percutaneous approach in the close vicinity of the nerve and the ability to target various nerves have led to its widespread use and compliance. While most of the mechanism behind its role in neuromodulation is largely unknown, the gate control theory proposed by Melzack and Wall in the 1960s has been the mainstay for understanding its mechanism of action. In this review article, the authors performed a literature review to discuss the mechanism of action of PNS and discuss its safety and usefulness in treating chronic pain. The authors also discuss current PNS devices available in the market today.

Sensory retraining for Central Post-Stroke Pain: A subgroup analysis within a randomized controlled trial

BACKGROUND

Explicit Sensory Retraining (SR) has been suggested for pain management in several neuropathic pain syndromes.

OBJECTIVES

To study the effectiveness of SR on Central Post Stroke Pain (CPSP) symptoms.

METHODS

A preplanned subgroup of 23 subjects post-stroke reporting central pain were randomized within a larger study, to receive either explicit sensory discrimination retraining (SR) (in subgroup n = 11) or implicit repeated exposure to stimuli (RE) (in subgroup n = 12), applied to the lower limb. Pain intensity measured by VAS, measures of sensory ability; balance and gait activities; and participation were assessed by a blinded assessor at four points in time.

RESULTS

A group*time interaction effect was demonstrated (p = 0.04) for VAS, as for the SR treatment group VAS decreased from 56/100 to 23/100. Nine out of eleven subjects in the SR group demonstrated positive response to treatment. Pain alleviation was maintained at follow-up. A similar interaction effect was found for tactile threshold (p = 0.03). Significant improvement was noted for all other variables with no group differences.

CONCLUSION

This study provides preliminary evidence to the clinically relevant positive effect of explicit sensory retraining for subjects with CPSP. The positive effect on tactile threshold detection could potentially indicate pain alleviation mechanisms.

Atypical influence of biomechanical knowledge in Complex Regional Pain Syndrome-towards a different perspective on body representation

Part of the multifaceted pathophysiology of Complex Regional Pain Syndrome (CRPS) is ascribed to lateralized maladaptive neuroplasticity in sensorimotor cortices, corroborated by behavioral studies indicating that patients present difficulties in mentally representing their painful limb. Such difficulties are widely measured with hand laterality judgment tasks (HLT), which are also used in the rehabilitation of CRPS to activate motor imagery and restore the cortical representation of the painful limb. The potential of these tasks to elicit motor imagery is critical to their use in therapy, yet, the influence of the body's biomechanical constraints (BMC) on HLT reaction time, supposed to index motor imagery activation, is rarely verified. Here we investigated the influence of BMC on the perception of hand postures and movements in upper-limb CRPS. Patients were slower than controls in judging hand laterality, whether or not stimuli corresponded to their painful hand. Reaction time patterns reflecting BMC were mostly absent in CRPS and controls. A second experiment therefore directly investigated the influence of implicit knowledge of BMC on hand movement judgments. Participants judged the perceived path of movement between two depicted hand positions, with only one of two proposed paths that was biomechanically plausible. While the controls mostly chose the biomechanically plausible path, patients did not. These findings show non-lateralized body representation impairments in CRPS, possibly related to difficulties in using correct knowledge of the body's biomechanics. Importantly, they demonstrate the challenge of reliably measuring motor imagery with the HLT, which has important implications for the rehabilitation with these tasks.

Comparison of clinical and biomechanical characteristics between individuals with lower limb amputation with and without lower back pain: A systematic review and meta-analysis

BACKGROUND

Lower back pain is a debilitating condition common to individuals with lower limb amputation. It is unclear what risk factors contribute to the development of back pain. This study systematically reviewed and analyzed the available evidence regarding the clinical and biomechanical differences between individuals with amputation, with and without lower back pain.

METHODS

A literature search was conducted in PubMed, Web of Science, Scopus, and CINAHL databases in November 2020 and repeated in June 2021 and June 2022. Studies were included if they reported comparisons of demographic, anthropometric, biomechanical, and other clinical variables between participants with and without LBP. Study quality and potential for reporting bias were assessed. Meta-analyses were conducted to compare the two groups.

FINDINGS

Thirteen studies were included, with aggregated data from 436 participants (239 with LBP; 197 pain free). The median reporting quality score was 37.5%. The included studies enrolled participants who were predominantly male (mean = 91.4%, range = 77.8-100%) and with trauma-related amputation. Meta-analyses showed that individuals with LBP exhibited moderate (3.4 out of 10) but significantly greater pain than those without LBP. We found no between-group differences in age, height, weight, BMI, and time since amputation (p = 0.121-0.682). No significant differences in trunk/pelvic kinematics during gait were detected (p = 0.07-0.446) between the groups.

INTERPRETATION

Demographic, anthropometric, biomechanical, and simple clinical outcome variables may be insufficient for differentiating the risk of developing back pain after amputation. Investigators should be aware of the existing gender bias in sampling and methodological limitations, as well as to consider incorporating psychosocial measures when studying LBP in this clinical population.