Distinguishing between nociceptive and neuropathic components in chronic low back pain using behavioural evaluation and sensory examination

Sensorimotor Integration in Chronic Low Back Pain

OBJECTIVE

Chronic low back pain (CLBP) impacts on spine movement. Altered sensorimotor integration can be involved. Afferents from the lumbo-pelvic area might be processed differently in CLBP and impact on descending motor control. This study aimed to determine whether afferents influence the corticomotor control of paravertebral muscles in CLBP. Fourteen individuals with CLBP (11 females) and 13 pain-free controls (8 females) were tested with transcranial magnetic stimulation (TMS) to measure the motor-evoked potential [MEP] amplitude of paravertebral muscles. Noxious and non-noxious electrical stimulation, and magnetic stimulation in the lumbo-sacral area were used as afferent stimuli and triggered 20 to 200 ms prior to TMS. EMG modulation elicited by afferent stimulation alone was measured to control net motoneuron excitability. MEP/EMG ratio was used as a measure of corticospinal excitability with control of net motoneuron excitability. MEP/EMG ratio was larger at 60, 80 and 100-ms intervals in CLBP compared to controls, and afferent stimulations alone reduced EMG amplitude greater in CLBP than controls at 100 ms. Our results suggest alteration in sensorimotor integration in CLBP highlighted by a greater facilitation of the descending corticospinal input to paravertebral muscles. Our results can help to optimise interventions by better targeting mechanisms.

Integrating mechanistic-based and classification-based concepts into perioperative pain management: an educational guide for acute pain physicians

Chronic pain begins with acute pain. Physicians tend to classify pain by duration (acute vs chronic) and mechanism (nociceptive, neuropathic and nociplastic). Although this taxonomy may facilitate diagnosis and documentation, such categories are to some degree arbitrary constructs, with significant overlap in terms of mechanisms and treatments. In clinical practice, there are myriad different definitions for chronic pain and a substantial portion of chronic pain involves mixed phenotypes. Classification of pain based on acuity and mechanisms informs management at all levels and constitutes a critical part of guidelines and treatment for chronic pain care. Yet specialty care is often siloed, with advances in understanding lagging years behind in some areas in which these developments should be at the forefront of clinical practice. For example, in perioperative pain management, enhanced recovery protocols are not standardized and tend to drive treatment without consideration of mechanisms, which in many cases may be incongruent with personalized medicine and mechanism-based treatment. In this educational document, we discuss mechanisms and classification of pain as it pertains to commonly performed surgical procedures. Our goal is to provide a clinical reference for the acute pain physician to facilitate pain management decision-making (both diagnosis and therapy) in the perioperative period.

Path Analysis Between Family Functioning and Mental Health in People With Neuropathic Pain: Roles of Pain Intensity, Self-Perceived Burden, Pain Catastrophizing, and Functional Status

PURPOSE

This study aimed to explore the pathways between family functioning and mental health in people with neuropathic pain, as well as to discuss the mediating role of pain intensity, self-perceived burden, pain catastrophizing, and functional status.

DESIGN

Cross-sectional design reported using the STROBE guidelines.

METHODS

A total of 277 people with neuropathic pain completed face-to-face questionnaires to evaluate family functioning, pain intensity, pain catastrophizing, self-perceived burden, functional status, and mental health. Structural equation modeling (SEM) was constructed to analyze the pathways between these variables.

RESULTS

The positive total effect between family functioning and mental health was significant and partially mediated by self-perceived burden, pain catastrophizing, and functional status. In addition, better family functioning was associated with higher pain intensity, which worsens self-perceived burden, pain catastrophizing, and functional status, masking 23.68% of the positive effects between family functioning and mental health.

CONCLUSIONS

Better family functioning was associated with better mental health, as explained by reduced self-perceived burden, reduced pain catastrophizing, and improved functional status. However, this benefit may be partially masked by the relationship that better family functioning explains higher pain intensity.

CLINICAL IMPLICATIONS

Nurses' comprehensive assessment and management of neuropathic pain from both the family and individual levels, such as family functioning, pain intensity, self-perceived burden, pain catastrophizing, and functional status, may be beneficial in promoting patients' mental health. In addition, it is necessary to identify why good family functioning is associated with higher pain intensity and intervene in this regard.

Associations between pain intensity, pain sensitivity, demographics, psychological factors, disability, physical activity, pain phenotype and COVID-19 history in low back pain: An observational study

BACKGROUND AND PURPOSE

Knowledge of the factors affecting pain intensity and pain sensitivity can inform treatment targets and strategies aimed at personalizing the intervention, conceivably increasing its positive impact on patients. Therefore, this study aimed to investigate the association between demographic factors (sex and age), body mass index (BMI), psychological factors (anxiety and depression, kinesiophobia and catastrophizing), self-reported physical activity, pain phenotype (symptoms of central sensitization, and nociceptive or neuropathic pain), history of COVID-19 and pain intensity and sensitivity in patients with chronic non-specific low back pain (LBP).

METHODS

This was a cross-sectional secondary analysis with 83 participants with chronic non-specific LBP recruited from the community between August 2021 and April 2022. BMI, pain intensity (Visual Analog Scale), pain sensitivity at the lower back and at a distant point [pressure pain threshold], catastrophizing (Pain Catastrophizing Scale), kinesiophobia (Tampa Scale for Kinesiophobia), anxiety and depression (Hospital Anxiety and Depression Scale), pain phenotype (Central Sensitization Inventory and PainDetect Questionnaire), physical activity (International Physical Activity Questionnaire), and disability (Roland Morris Disability Questionnaire) were assessed. Multiple linear regression analyses with pain intensity and sensitivity as the dependent variables were used.

RESULTS

The model for pain intensity explained 34% of its variance (Adjusted R2 = -0.343, p < 0.001), with depression and anxiety (p = 0.008) and disability (p = 0.035) reaching statistical significance. The model for pain sensitivity at the lower back, also explained 34% of its variance (Adjusted R2 = 0.344, p < 0.001) at the lower back with sex, BMI, and kinesiophobia reaching statistical significance (p < 0.05) and 15% of the variance at a distant body site (Adjusted R2 = 0.148, p = 0.018) with sex and BMI reaching statistical significance (p < 0.05).

DISCUSSION

This study found that different factors are associated with pain intensity and pain sensitivity in individuals with LBP. Increased pain intensity was associated with higher levels of anxiety and depression and disability and increased pain sensitivity was associated with being a female, higher kinesiophobia, and lower BMI.

Tactile localization accuracy at the low back

Localizing tactile stimulation is an important capability for everyday function and may be impaired in people with persistent pain. This study sought to provide a detailed description of lumbar spine tactile localization accuracy in healthy individuals. Sixty-nine healthy participants estimated where they were touched at nine different points, labelled in a 3 × 3 grid over the lumbar spine. Mislocalization between the perceived and actual stimulus was calculated in horizontal (x) and vertical (y) directions, and a derived hypotenuse (c) mislocalization was calculated to represent the direct distance between perceived and actual points. In the horizontal direction, midline sites had the smallest mislocalization. Participants exhibited greater mislocalization for left- and right-sided sites, perceiving sites more laterally than they actually were. For all vertical values, stimulated sites were perceived lower than reality. A greater inaccuracy was observed in the vertical direction. This study measured tactile localization for the low back utilizing a novel testing method. The large inaccuracies point to a possible distortion in the underlying perceptual maps informing the superficial schema; however, further testing comparing this novel method with an established tactile localization task, such as the point-to-point method, is suggested to confirm these findings.

Effect of use of NSAIDs or steroids during the acute phase of pain on the incidence of chronic pain: a systematic review and meta-analysis of randomised trials

BACKGROUND

This study is the first to summarize the evidence on how the use of anti-inflammatory drugs during acute pain has an impact on the development of chronic pain.

METHODS

Randomized controlled trials retrieved from nine databases included anti-inflammatory drugs (NSAIDs or steroids) versus non-anti-inflammatory drugs in patients with acute pain and reported the incidence of chronic pain. No specified date, age, sex, or language restrictions. Subgroup analyses were performed according to pain classification, follow-up time, and medication. The GRADE method was used to evaluate quality of evidence.

RESULTS

A total of 29 trials (5220 patients) were included. Steroids or NSAIDs did not reduce the incidence of chronic nociceptive pain. Steroid use in acute phase significantly reduced the incidence of chronic neuropathic pain. In subgroup analysis, benefits were observed for methylprednisolone and dexamethasone, with some adverse effects. Steroids or NSAIDs were statistically significant in reducing pain intensity over 1 year, but the effect size was too small, and whether the long-term effect is clinically relevant needs to be further studied.

CONCLUSION

Quality of the evidence was low to moderate. No drug can be recommended to prevent chronic nociceptive pain. Injections of steroids (methylprednisolone or dexamethasone) during the acute phase reduce the incidence of chronic neuropathic pain, but most included studies also used local anesthetics. The results are indirect and need to be interpreted with caution. The pooled data effect sizes for pain intensity were small, so the clinical relevance was unclear. Study registration PROSPERO (CRD42022367030).

Critical Appraisal of Current Acute LBP Management and the Role of a Multimodal Analgesia: A Narrative Review

Acute low back pain (LBP) stands as a leading cause of activity limitation and work absenteeism, and its associated healthcare expenditures are expected to become substantial when acute LBP develops into a chronic and even refractory condition. Therefore, early intervention is crucial to prevent progression to chronic pain, for which the management is particularly challenging and the most effective pharmacological therapy is still controversial. Current guideline treatment recommendations vary and are mostly driven by expertise with opinion differing across different interventions. Thus, it is difficult to formulate evidence-based guidance when the relatively few randomized clinical trials have explored the diagnosis and management of LBP while employing different selection criteria, statistical analyses, and outcome measurements. This narrative review aims to provide a critical appraisal of current acute LBP management by discussing the unmet needs and areas of improvement from bench-to-bedside, and proposes multimodal analgesia as the way forward to attain an effective and prolonged pain relief and functional recovery in patients with acute LBP.

Diagnosis and Management of Neuropathic Pain in Spine Diseases

Neuropathic pain is generally defined as a non-physiological pain experience caused by damage to the nervous system. It can occur spontaneously, as a reaction to a given stimulus, or independently of its action, leading to unusual pain sensations usually referred to as firing, burning or throbbing. In the course of spine disorders, pain symptoms commonly occur. According to available epidemiological studies, a neuropathic component of pain is often present in patients with spinal diseases, with a frequency ranging from 36% to 55% of patients. Distinguishing between chronic nociceptive pain and neuropathic pain very often remains a challenge. Consequently, neuropathic pain is often underdiagnosed in patients with spinal diseases. In reference to current guidelines for the treatment of neuropathic pain, gabapentin, serotonin and norepinephrine reuptake inhibitors and tricyclic antidepressants constitute first-line therapeutic agents. However, long-term pharmacologic treatment often leads to developing tolerance and resistance to used medications. Therefore, in recent years, a plethora of therapeutic methods for neuropathic pain have been developed and investigated to improve clinical outcomes. In this review, we briefly summarized current knowledge about the pathophysiology and diagnosis of neuropathic pain. Moreover, we described the most effective treatment approaches for neuropathic pain and discussed their relevance in the treatment of spinal pain.

A Review on Autophagy in Orofacial Neuropathic Pain

Orofacial neuropathic pain indicates pain caused by a lesion or diseases of the somatosensory nervous system. It is challenging for the clinician to diagnose and manage orofacial neuropathic pain conditions due to the considerable variability between individual clinical presentations and a lack of understanding of the mechanisms underlying the etiology and pathogenesis. In the last few decades, researchers have developed diagnostic criteria, questionnaires, and clinical assessment methods for the diagnosis of orofacial neuropathic pain. Recently, researchers have observed the role of autophagy in neuronal dysfunction as well as in the modulation of neuropathic pain. On this basis, in the present review, we highlight the characteristics, classification, and clinical assessment of orofacial neuropathic pain. Additionally, we introduce autophagy and its potential role in the modulation of orofacial neuropathic pain, along with a brief overview of the pathogenesis, which in future may reveal new possible targets for treating this condition.

Transcriptional and cellular signatures of cortical morphometric remodelling in chronic pain

ABSTRACT

Chronic pain is a highly debilitating and difficult to treat condition, which affects the structure of the brain. Although the development of chronic pain is moderately heritable, how disease-related alterations at the microscopic genetic architecture drive macroscopic brain abnormalities is currently largely unknown. Here, we examined alterations in morphometric similarity (MS) and applied an integrative imaging transcriptomics approach to identify transcriptional and cellular correlates of these MS changes, in 3 independent small cohorts of patients with distinct chronic pain syndromes (knee osteoarthritis, low back pain, and fibromyalgia) and age-matched and sex-matched pain-free controls. We uncover a novel pattern of cortical MS remodelling involving mostly small-to-medium MS increases in the insula and limbic cortex (none of these changes survived stringent false discovery rate correction for the number of regions tested). This pattern of changes is different from that observed in patients with major depression and cuts across the boundaries of specific pain syndromes. By leveraging transcriptomic data from Allen Human Brain Atlas, we show that cortical MS remodelling in chronic pain spatially correlates with the brain-wide expression of genes related to pain and broadly involved in the glial immune response and neuronal plasticity. Our findings bridge levels to connect genes, cell classes, and biological pathways to in vivo imaging correlates of chronic pain. Although correlational, our data suggest that cortical remodelling in chronic pain might be shaped by multiple elements of the cellular architecture of the brain and identifies several pathways that could be prioritized in future genetic association or drug development studies.

Use of the painDETECT to discriminate musculoskeletal pain phenotypes

Background

Musculoskeletal pain patients present similar pain characteristics regardless of the clinical diagnosis. PainDETECT questionnaire is useful for screening neuropathic-like symptoms in many musculoskeletal conditions. However, no previous studies compared pain phenotypes of patients with musculoskeletal pain using the painDETECT. Therefore, the current study aimed to compare the pain characteristics of patients with musculoskeletal pain classified according to the painDETECT as nociceptive pain, unclear, and neuropathic-like symptoms.

Methods

A cross-sectional study was conducted in 308 participants with musculoskeletal pain. Demographic and clinical characteristics of the participants were examined. Neuropathic-like symptoms, pain intensity, pain area, Central Sensitization-related sign and symptoms, functional limitation, and conditioned pain modulation were assessed in patients with musculoskeletal pain. Independent one-way analysis of variance (ANOVA) was used to test for between-group differences for the outcome measures with continuous variables and Pearson chi-square test verified between-group differences on the efficiency of the conditioned pain modulation.

Results

Participants had a mean age of 52.21 (±15.01) years old and 220 (71.42%) were females. One hundred seventy-three (56.16%) participants present nociceptive pain, 69 (22.40%) unclear, and 66 (21.42%) neuropathic-like symptoms. A one-way ANOVA showed differences for the pain intensity [F (2,305) = 20.097; p < .001], pain area [F (2,305) = 28.525; p < .001], Central Sensitization-related sign and symptoms [F (2,305) = 54.186; p < .001], and functional limitation [F (2,256) = 8.061; p < .001]. However, conditioned pain modulation was similarly impaired among the three groups (X² = 0.333, p = 0.847).

Conclusion

Patients with neuropathic-like symptoms revealed unfavorable pain characteristics compared to their counterparts, including pain intensity, generalized pain, Central Sensitization-related sign and symptoms, and functional limitation.

Classification of circadian pain rhythms and pain characteristics in chronic pain patients: An observational study

This study aimed to perform cluster analysis in patients with chronic pain to extract groups with similar circadian rhythms and compare neuropathic pain and psychological factors among these groups to identify differences in pain-related outcomes. A total of 63 community-dwellers with pain lasting at least 3 months and Numerical Rating Scale scores of ≥2 were recruited from 3 medical institutions. Their pain circadian rhythms were evaluated over 7 days by measuring pain intensity at 6-time points per day using a 10-cm visual analog scale. Cluster analysis was performed using 6 variables with standardized visual analog scale values at 6-time points for individual participants to extract groups with similar pain circadian rhythms. The results of the Neuropathic Pain Symptom Inventory and psychological evaluations in each group were compared using the Kruskal-Wallis test. The results revealed 3 clusters with different circadian rhythms of pain. The total and evoked pain subscale Neuropathic Pain Symptom Inventory scores differed among the 3 clusters. The results suggest that a thorough understanding of circadian pain rhythms in chronic pain patients may facilitate the performance of activities of daily living and physical exercise from the perspective of pain management.

Effectiveness of patient education focusing on circadian pain rhythms: A case report and review of literature

BACKGROUND

Neuropathic pain management should aim at improving quality of life and daily living activities of patients; therefore, emphasis should be placed on pain management including understanding the pain patterns during daily activity. Therefore, lifestyle guidance should be based on a detailed understanding of pain; however, previous studies commonly evaluated pain intensity at a single point in time. We report a case on patient education intervention based on the relationship between pain circadian rhythms and detailed physical activity during the day.

CASE SUMMARY

A man in his 60s, who suffered a brachial plexus injury in a traffic accident, presented with neuropathic pain. Early assessment of the importance of daily living activities to the patient, pain rhythmicity, and physical activity, was performed. The early assessments showed that the pain intensity was lower on days when more light-intensity physical activity (LIPA) was performed, than on days when less LIPA was performed. Consequently, patient education focused on methods to decrease the pain intensity that tended to worsen in the afternoon, and encouraged behavioral changes by suggesting the patient to take walks,” which could be used to maintain LIPA in the afternoon. On reassessment, the afternoon LIPA, which had been the focus of attention, had increased and a change was noted in the circadian rhythm of pain.

CONCLUSION

Patient education based on a composite assessment elicited positive results in relation to the pain circadian rhythm and physical activity.

Chronic pain: an update on burden, best practices, and new advances

Chronic pain exerts an enormous personal and economic burden, affecting more than 30% of people worldwide according to some studies. Unlike acute pain, which carries survival value, chronic pain might be best considered to be a disease, with treatment (eg, to be active despite the pain) and psychological (eg, pain acceptance and optimism as goals) implications. Pain can be categorised as nociceptive (from tissue injury), neuropathic (from nerve injury), or nociplastic (from a sensitised nervous system), all of which affect work-up and treatment decisions at every level; however, in practice there is considerable overlap in the different types of pain mechanisms within and between patients, so many experts consider pain classification as a continuum. The biopsychosocial model of pain presents physical symptoms as the denouement of a dynamic interaction between biological, psychological, and social factors. Although it is widely known that pain can cause psychological distress and sleep problems, many medical practitioners do not realise that these associations are bidirectional. While predisposing factors and consequences of chronic pain are well known, the flipside is that factors promoting resilience, such as emotional support systems and good health, can promote healing and reduce pain chronification. Quality of life indicators and neuroplastic changes might also be reversible with adequate pain management. Clinical trials and guidelines typically recommend a personalised multimodal, interdisciplinary treatment approach, which might include pharmacotherapy, psychotherapy, integrative treatments, and invasive procedures.

Methods to discriminate between mechanism-based categories of pain experienced in the musculoskeletal system: a systematic review

ABSTRACT

Mechanism-based classification of pain has been advocated widely to aid tailoring of interventions for individuals experiencing persistent musculoskeletal pain. Three pain mechanism categories (PMCs) are defined by the International Association for the Study of Pain: nociceptive, neuropathic, and nociplastic pain. Discrimination between them remains challenging. This study aimed to build on a framework developed to converge the diverse literature of PMCs to systematically review methods purported to discriminate between them; synthesise and thematically analyse these methods to identify the convergence and divergence of opinion; and report validation, psychometric properties, and strengths/weaknesses of these methods. The search strategy identified articles discussing methods to discriminate between mechanism-based categories of pain experienced in the musculoskeletal system. Studies that assessed the validity of methods to discriminate between categories were assessed for quality. Extraction and thematic analysis were undertaken on 184 articles. Data synthesis identified 200 methods in 5 themes: clinical examination, quantitative sensory testing, imaging, diagnostic and laboratory testing, and pain-type questionnaires. Few methods have been validated for discrimination between PMCs. There was general convergence but some disagreement regarding findings that discriminate between PMCs. A combination of features and methods, rather than a single method, was generally recommended to discriminate between PMCs. Two major limitations were identified: an overlap of findings of methods between categories due to mixed presentations and many methods considered discrimination between 2 PMCs but not others. The results of this review provide a foundation to refine methods to differentiate mechanisms for musculoskeletal pain.

Larger pain extent is associated with greater pain intensity and disability but not with general health status or psychosocial features in patients with cervical radiculopathy

Pain as a result of cervical radiculopathy (CR) can be widespread, nondermatomal and individually specific, but the association between pain extent and other clinical features has never been explored. The objective of this study is to investigate whether pain extent relates to clinical variables including pain intensity in addition to health indicators including disability, general health, depression, somatic anxiety, coping strategies or self-efficacy.An observational cohort study was conducted. Participants were recruited from 4 hospital spinal centres in Sweden. Pain extent was quantified from the pain drawings of 190 individuals with cervical disc disease, verified with magnetic resonance imaging (MRI) and compatible with clinical findings (examined by a neurosurgeon), that show cervical nerve root compression. Pain extent was evaluated in relation to neck pain, arm pain, and headache intensity. Multiple linear regression analysis were then used to verify whether pain extent was associated with other health indicators including disability, health-related quality of life, depression, somatic anxiety, coping strategies and self-efficacy.Pain extent was directly related to neck, arm and headache pain intensity (all P < .01). Multiple linear regression revealed that pain extent was significantly associated only to the level of perceived disability (P < .01).Increased pain extent in people with CR is associated with higher headache, neck and arm pain intensity, and disability but not measures of general health, depression, somatic anxiety, coping strategies or self-efficacy.

Astragalin Alleviates Neuropathic Pain by Suppressing P2X4-Mediated Signaling in the Dorsal Root Ganglia of Rats

Neurologic damage often leads to neuropathic pain, for which there are no effective treatments owing to its complex pathogenesis. The purinergic receptor P2X4 is closely associated with neuropathic pain. Astragalin (AST), a compound that is used in traditional Chinese medicine, has protective effects against allergic dermatitis and neuronal injury, but its mechanism of action is not well understood. The present study investigated whether AST can alleviate neuropathic pain in a rat model established by chronic constriction injury (CCI) to the sciatic nerve. The model rats exhibited pain behavior and showed increased expression of P2X4 and the activated satellite glial cell (SGC) marker glial fibrillary acidic protein in dorsal root ganglia (DRG). AST treatment partly abrogated the upregulation of P2X4, inhibited SGC activation, and alleviated pain behavior in CCI rats; it also suppressed ATP-activated currents in HEK293 cells overexpressing P2X4. These data demonstrate that AST relieves neuropathic pain by inhibiting P2X4 and SGC activation in DRG, highlighting its therapeutic potential for clinical pain management.

Cervical spine radiculopathy epidemiology: A systematic review

BACKGROUND AND OBJECTIVE

Cervical spine radiculopathy (CSR) is a disabling condition that has significant negative impacts on a person's mental health, physical functioning and social participation. Research has reported variable CSR incidence and prevalence among different populations. To date, no systematic review has been completed investigating the prevalence or incidence of CSR; therefore, our objective was to determine the incidence and/or prevalence of CSR in adults.

DESIGN AND METHOD

A systematic review was conducted including searches of PubMed (MEDLINE), EMBASE and CINAHL from inception to February 25, 2020. Studies including data on incidence and/or prevalence of CSR were included. Methodological quality was assessed using a modified Hayden, Cote and Bombardier appraisal checklist. Data were analysed narratively.

RESULTS

Nine low- to high-quality studies were included in the final review. Incidence ranged between 0.832 and 1.79 per 1,000 person-years from two high-quality and one low-quality study. Prevalence values ranged from 1.21 to 5.8 per 1,000 from four medium- to high-quality studies. Prevalence values of 1.14% [95% confidence interval (CI): 0.45-1.82] and 1.31% (95% CI: 0.66-1.96) for males and females, respectively, were reported from one medium-quality study. One medium-quality study reported an unadjusted prevalence value of 6.3% for males and females.

CONCLUSIONS

This is the first systematic review investigating the epidemiology of CSR in an adult population. This review reports a variable incidence rate and prevalence of CSR among specific populations; however, this was based on nine studies. There is a priority to investigate CSR epidemiology across other populations globally and standardising CSR diagnostic criteria.

When to consider "mixed pain"? The right questions can make a difference!

The term "mixed pain" is increasingly applied for specific clinical scenarios, such as low back pain, cancer pain and postsurgical pain, in which there "is a complex overlap of the different known pain types (nociceptive, neuropathic, nociplastic) in any combination, acting simultaneously and/or concurrently to cause pain in the same body area." Whether mixed pain is the manifestation of neuropathic and nociceptive mechanisms operating simultaneously or concurrently, or the result of an entirely independent pathophysiological mechanism - distinct from nociceptive, nociplastic and neuropathic pain - is currently unknown. At present, the diagnosis of mixed pain is made based on clinical judgement following detailed history-taking and thorough physical examination, rather than by formal confirmation following explicit screening or diagnostic criteria; this lack of formalized screening or diagnostic tools for mixed pain is problematic for physicians in primary care, who encounter patients with probable mixed pain states in their daily practice. This article outlines a methodical approach to clinical evaluation of patients presenting with acute, subacute or chronic pain, and to possibly identifying those who have mixed pain. The authors propose the use of nine simple key questions, which will provide the practicing clinician a framework for identifying the predominant pain mechanisms operating within the patient. A methodical, fairly rapid, and comprehensive assessment of a patient in chronic pain - particularly one suffering from pain with both nociceptive and neuropathic components - allows validation of their experience of chronic pain as a specific disease and, importantly, allows the institution of targeted treatment.

Quality of life and functional outcomes with tapentadol prolonged release in chronic musculoskeletal pain: post hoc analysis

Aims: To investigate quality of life (QOL) and functionality changes in chronic pain during tapentadol prolonged release (PR) treatment. Patients & methods: Post hoc analysis of data from three Phase III trials in patients with osteoarthritis knee pain or low back pain. QOL and functionality changes were assessed by SF-36 scores. Results: All SF-36 subdomain scores improved progressively to week 3 of tapentadol titration and were sustained during 12-week maintenance treatment. Improvements in SF-36 scores were similar between tapentadol dose groups (e.g., 200 to <300 mg vs ≥500 mg), with no greater effect from higher doses. QOL and functionality improvements were consistently greater with tapentadol PR than oxycodone controlled release. Conclusion: Tapentadol PR provides consistent, clinically relevant improvements in QOL and functionality in chronic pain.

Validation of the Questionnaire for Symptom Assessment in Pain disorders for Back pain patients (Q-SAP)

BACKGROUND

Previous studies have shown that not only pain intensity but also impairment of quality of life and functionality are important parameters for the evaluation of treatment of chronic low back pain patients. The aim of the study was to validate a specific self-questionnaire for symptom assessment and their influence on quality of life and functionality of chronic low back pain patients (Questionnaire for Symptom Assessment in Pain disorders for back pain patients, Q-SAP).

METHODS

The self-questionnaire consists of two parts (for back and if applicable leg symptoms) and was tested in 152 chronic low back pain patients with and without radiculopathy. Test-retest reliability, exploratory factor analysis, convergent validity, criterion-related validity and the sensitivity to detect patient reported changes were investigated.

RESULTS

The questionnaire showed a good to excellent test-retest reliability. In the factor analysis nociceptive and neuropathic pain components could be separated and the highest convergent validities were shown for the painDETECT, EQ-5D-3L and the FFbH-R. The criterion-related validity showed concordance of QST and the Q-SAP Back for warmth induced pain and numbness. Regarding the sensitivity to patient-reported changes, a moderate correlation was found for both parts of the questionnaire.

CONCLUSIONS

The Q-SAP was tested as a useful, valid and reliable tool. This new questionnaire records classical nociceptive and neuropathic pain symptoms of chronic low back pain patients depending on their local distribution. Furthermore, the questionnaire records the intensity of these symptoms and their influence on quality of life and functionality and can be used for the evaluation of treatment.

SIGNIFICANCE

The Q-SAP Back/Leg is a new self-questionnaire for CLBP patients with or without radiating leg pain that precisely assesses neuropathic and nociceptive symptoms. In contrast to other questionnaires, the Q-SAP Back/Leg evaluates not only symptom intensities but also their impact on the patient's quality of life and functionality. Furthermore, this questionnaire requests the symptoms depending on their anatomical distribution.

Sensory descriptors which identify neuropathic pain mechanisms in low back pain: a systematic review

OBJECTIVE

Descriptors provided by patients with neuropathic low back pain (NLBP) with or without spinally referred leg pain are frequently used by clinicians to help to identify the predominant pain mechanisms. Indeed, many neuropathic screening tools are primarily based on subjective descriptors to determine the presence of neuropathic pain. There is a need to systematically review and analyse the existing evidence to determine the validity of such descriptors in this cohort.

METHODS

Ten databases were systematically searched. The review adhered to PRISMA and CRD guidelines and included a risk of bias assessment using QUADAS-2. Studies were included if they contained symptom descriptors from a group of NLBP patients +/- leg pain. Studies had to include a reference test to identity neuropathic pain from other pain mechanisms.

RESULTS

Eight studies of 3099 NLBP patients were included. Allodynia and numbness were found to discriminate between NLBP and nociceptive LBP in four studies. Autonomic dysfunction, (changes in the colour or appearance of the skin), was also found to discriminate between the groups in two studies. Dysesthesia identified NLBP in 5/7 respectively. Results from studies were equivocal regarding pain described as hot/burning cold and paroxysmal pain in people with NLBP.

CONCLUSION

Subjectively reported allodynia and numbness would suggest a neuropathic pain mechanism in LBP. Dysesthesia would raise the suspicion of NLBP. More research is needed to determine if descriptors suggesting autonomic dysfunction can identify NLBP. There is poor consensus on whether other descriptors can identify NLBP.

The influence of nociceptive and neuropathic pain states on the processing of acute electrical nociceptive stimulation: A dynamic causal modeling study

INTRODUCTION

Despite the worldwide increase in prevalence of chronic pain and the subsequent scientific interest, researchers studying the brain and brain mechanisms in pain patients have not yet clearly identified the exact underlying mechanisms. Quantifying the neuronal interactions in electrophysiological data could help us gain insight into the complexity of chronic pain. Therefore, the aim of this study is to examine how different underlying pain states affect the processing of nociceptive information.

METHODS

Twenty healthy participants, 20 patients with non-neuropathic low back-related leg pain and 20 patients with neuropathic failed back surgery syndrome received nociceptive electrical stimulation at the right sural nerve with simultaneous electroencephalographic recordings. Dynamic Causal Modeling (DCM) was used to infer hidden neuronal states within a Bayesian framework.

RESULTS

Pain intensity ratings and stimulus intensity of the nociceptive stimuli did not differ between groups. Compared to healthy participants, both patient groups had the same winning DCM model, with an additional forward and backward connection between the somatosensory cortex and right dorsolateral prefrontal cortex.

DISCUSSION

The additional neuronal connection with the prefrontal cortex as seen in both pain patient groups could be a reflection of the higher attention towards pain in pain patients and might be explained by the higher levels of pain catastrophizing in these patients.

CONCLUSION

In contrast to the similar pain intensity ratings of an acute nociceptive electrical stimulus between pain patients and healthy participants, the brain is processing these stimuli in a different way.

Are painDETECT scores in musculoskeletal disorders associated with duration of daily pain and time elapsed since current pain onset?

Objectives:

We aimed to compare painDETECT scores in outpatients seen in a rheumatology department over a 1-month period and search for correlations between painDETECT scores and the estimated duration of daily pain and time elapsed since the onset of current pain.

Patients and Methods:

A total of 529 of 738 outpatients agreed to complete a set of questionnaires, including painDETECT.

Results:

The mean painDETECT score was 14.14 ± 7.59, and 31% of the patients had painDETECT scores of >18. Fibromyalgia ranked first (21.2 ± 6.0), followed by osteoarthritis of the lower limbs (17.8 ± 8.2), back pain and radiculopathies (16.1 ± 6.8), osteoarthritis of the upper limbs (15.7 ± 8.1), spondylarthrosis (15.1 ± 7.2), entrapment neuropathies (14.1 ± 2.4), rheumatoid arthritis (13.8 ± 7.1), miscellaneous conditions (13.8 ± 8.2), tendinitis (13.4 ± 7.9), connectivitis (11.5 ± 6.7), and osteoporosis (8.5 ± 6.9). The duration of daily pain was much longer in patients with painDETECT scores of >18 (12.41 ± 8.45 vs 6.53 ± 7.45 hours) (t = 0.0000), but very similar painDETECT scores were observed for patients suffering from pain for less than 1 week (13.7 ± 8.2; 38% > 18), for 1 month (14.5 ± 8.2; 25% > 18), several months (12.7 ± 7.3; 23% > 18), 1 year (13.8 ± 7.7; 29% > 18), or several years (14.7 ± 7.4; 33% > 18).

Conclusion:

PainDETECT scores differed little depending on the musculoskeletal condition, strongly correlated with the duration of daily pain, and appeared to be as high in patients with recent pain as in those suffering for years.

The effect of experimental pain on short-interval intracortical inhibition with multi-locus transcranial magnetic stimulation

Chronic neuropathic pain is known to alter the primary motor cortex (M1) function. Less is known about the normal, physiological effects of experimental neurogenic pain on M1. The objective of this study is to determine how short-interval intracortical inhibition (SICI) is altered in the M1 representation area of a muscle exposed to experimental pain compared to SICI of another muscle not exposed to pain. The cortical representation areas of the right abductor pollicis brevis (APB) and biceps brachii (BB) muscles of 11 subjects were stimulated with a multi-locus transcranial magnetic stimulation device while the resulting motor-evoked potentials (MEPs) were recorded with electromyography. Single- and paired-pulse TMS was administered in seven conditions, including one with the right hand placed in cold water. The stimulation intensity for the conditioning pulses in the paired-pulse examination was 80% of the resting motor threshold (RMT) of the stimulated site and 120% of RMT for both the test and single pulses. The paired-pulse MEP amplitudes were normalized with the mean amplitude of the single-pulse MEPs of the same condition and muscle. SICI was compared between conditions. After the cold pain, the normalized paired-pulse MEP amplitudes decreased in APB, but not in BB, indicating that SICI was potentially increased only in the cortical area of the muscle subjected to pain. These data suggest that SICI is increased in the M1 representation area of a hand muscle shortly after exposure to pain has ended, which implies that short-lasting pain can alter the inhibitory balance in M1.

Alterations in Temporal Summation of Pain and Conditioned Pain Modulation Across an Episode of Experimental Exercise-Induced Low Back Pain

Persistent pain conditions, including low back pain (LBP), are often accompanied by alterations in pronociceptive and antinociceptive mechanisms, as quantified by temporal summation of pain (TSP) and conditioned pain modulation (CPM). It remains unclear whether altered pain sensitivity, CPM, and/or TSP are a consequence of pain presence or determine the degree of pain development. Pressure pain sensitivity, TSP, and CPM were assessed across an episode of exercise-induced LBP maintained for several days. Thirty healthy individuals participated in 3 experimental sessions: before (day 0), 2 days after fatiguing back muscle exercise with exercise-induced LBP present (day 2), and after pain resolution (day 7). Both handheld and cuff pressure-pain thresholds, along with TSP (10-cuff pain stimuli at .5 Hz) and CPM (cuff pain detection threshold prior versus during painful pressure conditioning) were assessed, alongside questionnaires pertaining to pain, disability, mood, sleep, menstruation, physical activity, and catastrophizing. The exercise-induced LBP model produced mild pain and disability, and reductions in pressure pain thresholds over both the lumbar and distant testing sites (p < .007). No pain-related changes were observed for TSP (p > .44) or CPM (p > .17). The baseline TSP was associated with the peak pain intensity of the exercise-induced LBP (p < .003). Perspective: Pressure-pain sensitivity was impacted by the presence of exercise-induced LBP, whereas TSP seemed to be more stable and was instead associated with the intensity of pain developed. No significant pain-related changes or associations were observed for CPM, suggesting this measure may have less usefulness in mild musculoskeletal pain conditions.

Rehabilitation management of low back pain - it's time to pull it all together!

In the past, rehabilitation research initiatives for low back pain (LBP) have targeted outcome enhancement through personalized treatment approaches, namely through classification systems (CS). Although the use of CS has enhanced outcomes, common management practices have not changed, the prevalence of LBP is still high, and only selected patients meet the CS profile, namely those with a nociceptive context. Similarly, although practice guidelines propose some level of organization and occasionally a timeline of care provision, each mainly provides best practice for isolated treatment approaches. Moreover, there is no theoretical framework that has been proposed that guides the rehabilitation management process of mechanical LBP. In this commentary, we propose a model constituted of five domains (nociceptive drivers, nervous system dysfunction drivers, comorbidities drivers, cognitive–emotional drivers, and contextual drivers) grounded as mechanisms driving pain and/or disability in LBP. Each domain is linked to the International Classification of Functioning, Disability and Health, where once a patient is deemed suitable for rehabilitation, the clinician assesses elements of each domain in order to identify where the relative treatment efforts should be focused. This theoretical model is designed to provide a more comprehensive management overview, by appreciating the relative contribution of each domain driving pain and disability. Considering that the multiple domains driving pain and disability, and their interaction, requires a model that is comprehensive enough to identify and address each related issue, we consider that the proposed model has several positive implications for rehabilitation of this painful and highly prevalent musculoskeletal disorder.