The IASP classification of chronic pain for ICD-11: chronic neuropathic pain

Optogenetic Activation of Peripheral Somatosensory Neurons in Transgenic Mice as a Neuropathic Pain Model for Assessing the Therapeutic Efficacy of Analgesics

Optogenetics is a novel biotechnology widely used to precisely manipulate a specific peripheral sensory neuron or neural circuit. However, the use of optogenetics to assess the therapeutic efficacy of analgesics is elusive. In this study, we generated a transgenic mouse stain in which all primary somatosensory neurons can be optogenetically activated to mimic neuronal hyperactivation in the neuropathic pain state for the assessment of analgesic effects of drugs. A transgenic mouse was generated using the advillin-Cre line mated with the Ai32 strain, in which channelrhodopsin-2 fused to enhanced yellow fluorescence protein (ChR2-EYFP) was conditionally expressed in all types of primary somatosensory neurons (advillincre/ChR2+/+). Immunofluorescence and transdermal photostimulation on the hindpaws were used to verify the transgenic mice. Optical stimulation to evoke pain-like paw withdrawal latency was used to assess the analgesic effects of a series of drugs. Injury- and pain-related molecular biomarkers were investigated with immunohistofluorescence. We found that the expression of ChR2-EYFP was observed in many primary afferents of paw skin and sciatic nerves and in primary sensory neurons and laminae I and II of the spinal dorsal horns in advillincre/ChR2+/+ mice. Transdermal blue light stimulation of the transgenic mouse hindpaw evoked nocifensive paw withdrawal behavior. Treatment with gabapentin, some channel blockers, and local anesthetics, but not opioids or COX-1/2 inhibitors, prolonged the paw withdrawal latency in the transgenic mice. The analgesic effect of gabapentin was also verified by the decreased expression of injury- and pain-related molecular biomarkers. These optogenetic mice provide a promising model for assessing the therapeutic efficacy of analgesics in neuropathic pain.

Right posterior insular epidural stimulation in rats with neuropathic pain induces a frequency-dependent and opioid system-mediated reduction of pain and its comorbid anxiety and depression

Neuropathic pain (NP) is a sensory, emotional, and persistent disturbing experience caused by a lesion or disease of the somatosensory system which can lead when chronic to comorbidities such as anxiety and depression. Available treatments (pharmacotherapy, neurostimulation) have partial and unpredictable response; therefore, it seems necessary to find a new therapeutical approach that could alleviate most related symptoms and improve patients 'emotional state'. Posterior Insula seems to be a potential target of neurostimulation for pain relief. However, its effects on pain-related anxiety and depression remain unknown. Using rats with spared nerve injury (SNI), this study aims to elucidate the correlation between NP and anxio-depressive disorders, evaluate potential analgesic, anxiolytic, and antidepressant effects of right posterior insula stimulation (IS) using low (LF-IS, 50 Hz) or high (HF-IS, 150 Hz) frequency and assess endogenous opioid involvement in these effects. Results showed positive correlation between NP, anxiety, and depression. LF-IS reversed anhedonia and despair-like behavior through pain alleviation, whereas HF-IS only reduced anhedonia, all effects involving endogenous opioids. These findings support the link between NP and anxio-depressive disorders. Moreover, IS appears to have analgesic, anxiolytic and antidepressant effects mediated by the endogenous opioid system, making it a promising target for neurostimulation.

Non-pharmacological management of neuropathic pain in older adults: a systematic review

INTRODUCTION

Neuropathic pain encompasses multiple diagnoses with detrimental impacts on quality of life and overall health. In older adults, pharmacological management is limited by adverse effects and drug interactions, while surgical management involves perioperative risk. Prior reviews addressing non-pharmacological interventions for neuropathic pain have not focused on this demographic. Therefore, this systematic review synthesizes the evidence regarding the effectiveness of non-pharmacological interventions in reducing neuropathic pain severity in older adults.

METHODS

PubMed, CINAHL, Web of Science, and PsycInfo were searched using key terms, with inclusion criteria of age ≥ 65, neuropathic pain, non-pharmacological intervention, pain severity measurement, English language, peer-reviewed, and either randomized controlled trial (RCT) or quasi-experimental design. In total, 2759 records were identified, with an additional 28 records identified by review of reference lists. After removal of duplicates, 2288 records were screened by title and abstract, 404 full-text articles were assessed, and 19 articles were critically reviewed and synthesized.

RESULTS

Of the 14 RCTs and 5 quasi-experimental studies included in the review, the most common intervention was electric and/or magnetic therapy, followed by acupuncture, mindfulness meditation, exercise, and light therapy. Several studies revealed both statistical and clinical significance, but conclusions were limited by small sample sizes and methodological shortcomings. The interventions were generally safe and acceptable.

CONCLUSIONS

Results should be interpreted with consideration of clinical vs statistical significance, mediators of pain severity, and individual variations in effectiveness. Further research should address multimodal and novel interventions, newer models of care, and technology-based interventions.

Incidence of Different Characters of Neuropathic Pain in Cancer Patients Coming to Tertiary Care Centre in North India Over A Period of 1 Year - An Observational Study

Objectives

Pain is classified as nociceptive, neuropathic, or nociplastic. Neuropathic pain presents as variable phenotypes (characters) based on specific aetiology and pathophysiology. This study aimed to find out among cancer patients the incidence of different phenotypes of neuropathic pain and form specific phenotypic clusters based on the underlying neurophysiology and association of sensory profile with various organ systems - A prospective observational study.

Materials and methods

The Institutional Ethical Committee clearance (IEC code: 2020-49-MD-EXP-15) https://ctri.nic.in/Clinicaltrials/showallp.php?mid1=44886&EncHid=88651.15716&userName=CTRI/2020/09/027964 approval was obtained. After written and informed consent, patients of age group 18-80 years, registering in the pain and palliative outpatient department or radiotherapy department with complaints of pain and not taking any anti-neuropathic pain medications, were enrolled. They were assessed using Leeds assessment of neuropathic symptoms and signs (LANSS) pain score, and a score of >12 was eligible for assessment of neuropathic pain phenotypes.

Results

Out of 210 cancer patients complaining of pain, a neuropathic component with LANSS >12 was found in 73 (34.76%). The most predominant phenotypes, allodynia> tingling> pricking = burning, were found in 72.60%, 56.16%, and 43.84% of patients, respectively. Phenotypes were clustered into Nodes 1 and 2 based on clinically significant separation of phenotypes. Node 1 had neuropathic pain of spontaneous origin found predominantly in gastrointestinal tract (GIT) and genitourinary tract (GUT) cancers. Node 2 had stimulus-evoked negative and positive characters which occurred in head and neck, thoracic, and spinal metastatic cancers.

Conclusion

Careful patient assessment reveals the incidence of neuropathic pain in 34.76%; allodynia and tingling astable the most prominent phenotypes. Broadly, sensory characters were clustered into spontaneous and stimulus-evoked sensations with GIT and GUT cancers presenting with Node 1 symptoms.

Exercise, Spinal Microglia and Neuropathic Pain: Potential Molecular Mechanisms

As one of the most common neuropathic disorders, neuropathic pain often has a negative impact on patients with persistent pain, mood disorders and sleep disturbances. Currently, neuropathic pain is not treated with any specific drug, instead, drugs for other diseases are used as replacements in clinics, but most have adverse effects. In recent years, the role of spinal cord microglia in the pathogenesis of neuropathic pain has been widely recognized, and they are being explored as potential therapeutic targets. Spinal microglia are known to be involved in the pathogenic mechanisms of neuropathic pain through purine signaling, fractalkine signaling, and p38 MAPK signaling. Exercise is a safe and effective treatment, and numerous studies have demonstrated its effectiveness in improving neurological symptoms. Nevertheless, it remains unclear what the exact molecular mechanism is. This review summarized the specific molecular mechanisms of exercise in alleviating neuropathic pain by mediating the activity of spinal microglia and maintaining the phenotypic homeostasis of spinal microglia through purine signaling, fractalkine signaling and p38 MAPK signaling. In addition, it has been proposed that different intensities and types of exercise affect the regulation of the above-mentioned signaling pathways differently, providing a theoretical basis for the improvement of neuropathic pain through exercise.

Newly discovered functions of miRNAs in neuropathic pain: Transitioning from recent discoveries to innovative underlying mechanisms

Neuropathic pain is a widespread clinical issue caused by somatosensory nervous system damage, affecting numerous individuals. It poses considerable economic and public health challenges, and managing it can be challenging due to unclear underlying mechanisms. Nevertheless, emerging evidence suggests that neurogenic inflammation and neuroinflammation play a role in developing pain patterns. Emerging evidence suggests that neurogenic inflammation and neuroinflammation play significant roles in developing neuropathic pain within the nervous system. Increased/decreased miRNA expression patterns could affect the progression of neuropathic and inflammatory pain by controlling nerve regeneration, neuroinflammation, and the expression of abnormal ion channels. However, our limited knowledge of miRNA targets hinders a complete grasp of miRNA's functions. Meanwhile, exploring exosomal miRNA, a recently uncovered role, has significantly advanced our comprehension of neuropathic pain's pathophysiology in recent times. In this review, we present a comprehensive overview of the latest miRNA studies and explore the possible ways miRNAs might play a role in the development of neuropathic pain.

The Predicted Outcome of Spinal Cord Stimulation in Patients With a Psychopathological Disorder and Persistent Spinal Pain Syndrome Type 2: A Systematic Review From 2009 to 2021

OBJECTIVES

Psychologic screening is often included as a mandatory component of evaluation of the impact of psychopathology disorders on the predicted outcome of spinal cord stimulation (SCS) for patients with chronic pain due to persistent spinal pain syndrome type 2 (PSPS type 2). The conclusion of such screenings can influence the decision to offer SCS therapy to a patient. However, evidence on the impact of psychopathology on SCS outcomes is still scarce.

MATERIALS AND METHODS

To address this knowledge gap, we systematically reviewed the literature from 2009 to 2021 to explore the correlation between the presence of a psychopathological disorder and the predicted outcome of SCS in patients with PSPS type 2. The literature search was conducted using various online data bases with "failed back surgery syndrome," "psychopathology," and "spinal cord stimulation" used as essential keywords. The identified studies were organized in a Rayyan AI data base, and the quality was analyzed with the Critical Appraisal Skills Program tool.

RESULTS

Our search generated the identification of 468 original articles, of which two prospective and four retrospective studies met our inclusion criteria. These studies reported pain relief, a reduction of symptoms of anxiety and depression, and an improvement in rumination on the Pain Catastrophizing Scale in patients with PSPS type 2 after SCS therapy. The studies also found contradictory outcomes measured using the Oswestry Disability Index, and in terms of the impact of psychopathological disorder on the clinical outcome and revision rate of the SCS system.

CONCLUSION

In this systematic review, we found no convincing evidence that the presence of a psychopathological disorder affects the predicted outcome of SCS therapy in patients with PSPS type 2.

Association of Risk Factors and Comorbidities With Chronic Pain in the Elderly Population

INTRODUCTION/OBJECTIVE

Chronic pain disorders affect about 20% of adults in the United States, and it disproportionately affects individuals living in the neighborhoods of extreme socioeconomic disadvantage. In many instances, chronic pain has been noted to arise from an aggregation of multiple risk factors and events. Therefore, it is of importance to recognize the modifiable risk factors. The aim of this study was to investigate the comorbid medical conditions and risk factors associated with chronic pain disorders in patients aged 65 years and older.

METHODS

Our team retrospectively reviewed medical records of elderly patients (65 years and older) who were evaluated in our outpatient medicine office between July 1, 2020 and June 30, 2021 for acute problems, management of chronic medical problems, or well visits. We divided our patients into a group who suffered from chronic pain disorder, and another group who did not have chronic pain disorder. The association of variables were compared between those groups.

RESULTS

Of the 2431 patients, 493 (20.3%) had a chronic pain disorder. A higher frequency of females in the group with chronic pain disorder was found compared to the group without a chronic pain disorder (60.6% vs 55.2%; P = .033). The mean ages between the two groups were similar in the group with a chronic pain disorder compared to the group without (76.35 ± 7.5 year vs 76.81 ± 7.59 year; P = .228). There were significant associations of certain comorbidities in the group with a chronic pain disorder compared to the group without a chronic pain disorder, such as depression (21.9% vs 15.2%; P < .001), anxiety (27.0% vs 17.1%; P < .001), chronic obstructive pulmonary disease (8.7% vs 6.1%; P = .036), obstructive sleep apnea (16.8% vs 11.6%; P = .002), gastroesophageal reflux disease (40.8% vs 29.0%; P < .001), osteoarthritis (49.3% vs 26.1%; P < .001), other rheumatologic diseases (24.9% vs 19.4%; P = .006), and peripheral neuropathy (14.4% vs 5.3%; P < .001).

CONCLUSION

Female sex, depression, anxiety, chronic obstructive pulmonary disease, obstructive sleep apnea, gastroesophageal reflux disease, osteoarthritis, other rheumatologic diseases, and peripheral neuropathy were significantly associated with chronic pain disorder in elderly patients, while BMI was not associated with chronic pain disorder.

Exercise Training for Chronic Pain: Available Evidence, Current Recommendations, and Potential Mechanisms

Chronic pain conditions pose a significant global burden of disability, with epidemiological data indicating a rising incidence. Exercise training is commonly recommended as a standalone or complementary approach for managing various chronic pain conditions like low back pain, osteoarthritis, rheumatoid arthritis, fibromyalgia syndrome, and neuropathic pain. Regardless of the specific condition or underlying cause (e.g., autoimmune disease, chronic inflammation), exercise training consistently leads to moderate to large reductions in pain. Moreover, exercise yields numerous benefits beyond pain alleviation, including small-to-moderate improvements in disability, quality of life, and physical function. Despite its efficacy, there is a lack of comprehensive research delineating the optimal intensity, duration, and type of exercise for maximal benefits; however, evidence suggests that sustained engagement in regular exercise or physical activity is necessary to achieve and maintain reductions in both clinical pain intensity ratings and the level that pain interferes with activities of daily living. Additionally, the precise mechanisms through which exercise mitigates pain remain poorly understood and likely vary based on the pathophysiological mechanisms underlying each condition.

Knowledge and experience of dentists with patients with trigeminal neuralgia: A prospective, cross-sectional survey study

OBJECTIVE

Trigeminal neuralgia (TN) and orofacial pain (OFP) patients frequently refer to dentists. It is often confused with odontogenic pain and dental procedures are performed. In this study, the authors aimed to reveal the knowledge and experience of dentists about TN.

METHODS

This is a cross-sectional study that includes dentists who participate in volunteering via an online questionnaire. The questionnaire form contains demographic data, TN treatment, and diagnosis consisting of 18 questions.

RESULTS

The data of 229 dentists were examined. Almost 82% of the participants reportedly knew the diagnostic criteria of TN and 61.6% reported that they had previously referred patients with TN. The most frequently confused diagnosis was odontogenic pains (45.9%).

CONCLUSION

TN diagnostic criteria should be included more often in the education of dentists. Thus, it is possible to prevent unnecessary dental procedures. There is a need to increase knowledge on this subject with further studies involving dental students.

IUPHAR review- Preclinical models of neuropathic pain: Evaluating multifunctional properties of natural cannabinoid receptors ligands

Neuropathic pain remains prevalent and challenging to manage and is often comorbid with depression and anxiety. The new approach that simultaneously targets neuropathic pain and the associated comorbidities, such as depression and anxiety, is timely and critical, given the high prevalence and severity of neuropathic pain and the lack of effective analgesics. In this review, we focus on the animal models of neuropathic pain that researchers have used to investigate the analgesic effects of cannabidiol (CBD) and Beta-Caryophyllene (BCP) individually and in combination while addressing the impact of these compounds on the major comorbidity (e.g., depression, anxiety) associated with neuropathic pain. We also addressed the potential targets/mechanisms by which CBD and BCP produce analgesic effects in neuropathic pain models. The preclinical studies examined in this review support CBD and BCP individually and combined as potential alternative analgesics for neuropathic pain while showing beneficial effects on depression and anxiety.

[Current state of algology - pain medicine - in the Russian Federation]

OBJECTIVE

To analyze the structure of care for patients with pain syndromes in the Russian Federation and possible improvement of these approaches.

MATERIAL AND METHODS

A detailed questionnaire was sent to 60 pain clinics. We received responses from 40 hospitals. Other information was obtained from annual statistical reports for 2021-2023. Fifteen clinics and departments in different regions were inspected.

RESULTS

A total of 3871 implantations of test electrodes and 2317 systems for permanent neurostimulation were performed in the Russian Federation in 2021-2023. There were 30-110 annual implantations in Moscow and St. Petersburg clinics, as well as 5-30 procedures in other hospitals. The indications for stimulation system implantation were persistent back pain syndrome (58%), complex regional pain syndrome (12.5%), spasticity (9%), chronic pelvic pain (7.5%), critical lower limb ischemia (6%), peripheral neuropathies (5%), refractory angina (1%), etc. (1%). About 3700 patients seek treatment in pain departments and clinics annually. Of these, 49% were referred for interventional treatment (blockades, radiofrequency ablation), 7% - for neuromodulation.

DISCUSSION

Extrapolation of the International Association for the Study of Pain (IASP) data suggests that 548.000 people in the Russian Federation suffer from neuropathic pain refractory to drug therapy. The need for pain surgery is 27.400 interventions per year. In the Russian Federation, there is no multiple-level medical care for severe pain syndromes. It is difficult to realize a comprehensive interdisciplinary approach to diagnosis, treatment and rehabilitation of patients who suffer and often become disabled only because of severe chronic pain.

CONCLUSION

It is necessary to distinguish algology as a separate specialty and contribute to development of this extremely important area of medicine.

Osteoporosis treatment and pain relief: A scoping review

BACKGROUND AND OBJECTIVE

Anti-osteoporosis (OP) drugs have been suggested to contribute to pain reduction during OP management. This scoping review aimed at mapping the literature on pain relief with anti-OP drugs in OP treatment.

DATABASES AND DATA TREATMENT

Medline, Pubmed and Cochrane databases were searched by two reviewers with keywords combinations. Randomized controlled and real-life English studies, pain as an endpoint, antiosteoporosis drugs were inclusion criteria. Case reports, surveys, comment letters, conference abstracts, animal studies and grey literature were excluded. Predetermined data were extracted by two reviewers and disagreement solved through discussion.

RESULTS

A total of 130 articles were identified, 31 publications were included, 12 randomized clinical trials and 19 observational studies. Pain reduction was assessed by different tools: Visual Analogue Scale, Verbal Rating Scale, Facial Scale or as a domain of quality of life questionnaires including Short form 8, 36, mini-OP, Japanese OP, Qualeffo, Roland Morris Disability questionnaires. Collective data show that anti-OP drugs may display an analgesic effect that may be linked to the local mode of action of drugs on bone and consecutive modulation of pain sensitization. The methodology of the studies showed a heterogeneity of endpoints, comparators, statistical approaches and follow-up duration.

CONCLUSION

Considering the limitations of the literature, there is a need for more rigorous trials and larger real-life studies taking into account the recommendations published for research in rheumatology and in pain medicine. The identification of responders, patient subtypes, and of analgesic-effect doses would allow optimization and individualization for pain relief in patients with OP.

SIGNIFICANCE STATEMENT

This scoping review shows that anti-OP drugs may improve pain and quality of life of patients with OP. The heterogeneity in design, choice of endpoints, methodology, comparators and follow-up duration of included randomized clinical trials and real-life studies does not allow so far to identify a predominant antiosteoporosis drug or an optimal dosage for pain relief. These gaps need to be addressed and warrant further research in the future for optimizing pain improvement in the course of OP drug treatment.

Central neuropathic pain

Central neuropathic pain arises from a lesion or disease of the central somatosensory nervous system such as brain injury, spinal cord injury, stroke, multiple sclerosis or related neuroinflammatory conditions. The incidence of central neuropathic pain differs based on its underlying cause. Individuals with spinal cord injury are at the highest risk; however, central post-stroke pain is the most prevalent form of central neuropathic pain worldwide. The mechanisms that underlie central neuropathic pain are not fully understood, but the pathophysiology likely involves intricate interactions and maladaptive plasticity within spinal circuits and brain circuits associated with nociception and antinociception coupled with neuronal hyperexcitability. Modulation of neuronal activity, neuron-glia and neuro-immune interactions and targeting pain-related alterations in brain connectivity, represent potential therapeutic approaches. Current evidence-based pharmacological treatments include antidepressants and gabapentinoids as first-line options. Non-pharmacological pain management options include self-management strategies, exercise and neuromodulation. A comprehensive pain history and clinical examination form the foundation of central neuropathic pain classification, identification of potential risk factors and stratification of patients for clinical trials. Advanced neurophysiological and neuroimaging techniques hold promise to improve the understanding of mechanisms that underlie central neuropathic pain and as predictive biomarkers of treatment outcome.

Clinical Diagnosis and Treatment of Chronic Pain

More than 600 million people globally are estimated to be living with chronic pain. It is one of the most common complaints seen in an outpatient setting, with over half of patients complaining of pain during a visit. Failure to properly diagnose and manage chronic pain is associated with substantial morbidity and mortality, especially when opioids are involved. Furthermore, it is a tremendous financial strain on the healthcare system, as over USD 100 billion is spent yearly in the United States on healthcare costs related to pain management and opioids. This exceeds the costs of diabetes, heart disease, and cancer-related care combined. Being able to properly diagnose, manage, and treat chronic pain conditions can substantially lower morbidity, mortality, and healthcare costs in the United States. This review will outline the current definitions, biopsychosocial model, subclassifications, somatosensory assessments, imaging, clinical prediction models, and treatment modalities associated with chronic pain.

Combination Drug Therapy for the Management of Chronic Neuropathic Pain

Chronic neuropathic pain (NP) is an increasingly prevalent disease and leading cause of disability which is challenging to treat. Several distinct classes of drugs are currently used for the treatment of chronic NP, but each drug targets only narrow components of the underlying pathophysiological mechanisms, bears limited efficacy, and comes with dose-limiting side effects. Multimodal therapies have been increasingly proposed as potential therapeutic approaches to target the multiple mechanisms underlying nociceptive transmission and modulation. However, while preclinical studies with combination therapies showed promise to improve efficacy over monotherapy, clinical trial data on their efficacy in specific populations are lacking and increased risk for adverse effects should be carefully considered. Drug-drug co-crystallization has emerged as an innovative pharmacological approach which can combine two or more different active pharmaceutical ingredients in a single crystal, optimizing pharmacokinetic and physicochemical characteristics of the native molecules, thus potentially capitalizing on the synergistic efficacy between classes of drugs while simplifying adherence and minimizing the risk of side effects by reducing the doses. In this work, we review the current pharmacological options for the treatment of chronic NP, focusing on combination therapies and their ongoing developing programs and highlighting the potential of co-crystals as novel approaches to chronic NP management.

Evaluation of Neuropathic Pain after Total Knee Arthroplasty: Do Yellow Flags Matter?

Up to 20% of total knee arthroplasty (TKA) patients continue to experience chronic postsurgical pain. Various factors have been identified as potential contributors, including so-called "yellow flags", encompassing symptoms of depression, anxiety, and catastrophizing, which were examined in this study to assess their predictive value concerning functional outcomes after TKA.

METHODS

Fifty TKA patients were categorized into high-risk and low-risk groups based on clinical assessment, demographic data, medication, and patient-reported outcome measures (DN4, SF-36, WOMAC, NRS, Fibromyalgia Survey Questionnaire, Pain Catastrophizing Scale, and Hospital Anxiety and Depression Scale). Postoperative outcomes within six months after TKA were then compared.

RESULTS

Both groups exhibited significant (p < 0.001) improvements in all WOMAC and NRS subscales, as well as in the physical function, role physical, pain, and energy/fatigue subdomains of the SF-36 after six months, while the high-risk group showed lower WOMAC scores regarding stiffness (19.0 ± 18.3 vs. 27.2 ± 20.7, p < 0.001) and pain (13.5 ± 13.3 vs. 15.1 ± 16.3, p = 0.029). The high-risk group showed significantly worse preoperative DN4 scores (1.8 ± 1.3 vs. 3.0 ± 1.1, p = 0.002) than the low-risk group, which persisted for one day (2.3 ± 1.2 vs. 3.5 ± 1.5, p = 0.005) and six weeks (2.2 ± 1.9 vs. 3.6 ± 2.3, p = 0.041) postoperatively.

CONCLUSIONS

Our results indicate that pre-existing yellow flags contribute to a more challenging early postoperative phase, underscoring the importance of considering individual patient characteristics and psychological factors to optimize TKA outcomes.

Is the Straight Leg Raise Suitable for the Diagnosis of Radiculopathy? Analysis of Diagnostic Accuracy in a Phase III Study

The straight leg raise test (SLR) has been proposed to detect increased nerve mechanosensitivity of the lower limbs in individuals with low back pain. However, its validity in the diagnosis of lumbosacral radiculopathy shows very variable results. The aim of this study was to analyse the diagnostic validity of the SLR including well-defined diagnostic criteria (a change in symptoms with the structural differentiation manoeuvre and the reproduction of the patient's symptoms during the test or the asymmetries in the range of motion or symptoms location between limbs) in a sample of participants in phase III with suspicion of lumbar radiculopathy using the electrodiagnostic studies (EDX) as the reference standard. A phase III diagnostic accuracy study was designed. In total, 142 individuals with suspected lumbosacral radiculopathy referred for EDX participated in the study. Each participant was tested with EDX and SLR. SLR was considered positive using three diagnostic criteria. The sensitivity of the SLR for Criterion 3 was 89.02% (CI 81.65-96.40), the specificity was 25.00% (CI 13.21-36.79), and the positive and negative likelihood ratios were 1.19 (CI 1.01-1.40) and 0.44 (0.21-0.94), respectively. SLR showed limited validity in the diagnosis of lumbosacral radiculopathy. The incorporation of more objective diagnostic criteria (asymmetry in range of motion or localisation of symptoms) improved the diagnostic validity but the imprecision of the confidence intervals limited the interpretation of the results.

Advancements in Understanding and Classifying Chronic Orofacial Pain: Key Insights from Biopsychosocial Models and International Classifications (ICHD-3, ICD-11, ICOP)

In exploring chronic orofacial pain (COFP), this review highlights its global impact on life quality and critiques current diagnostic systems, including the ICD-11, ICOP, and ICHD-3, for their limitations in addressing COFP's complexity. Firstly, this study outlines the global burden of chronic pain and the importance of distinguishing between different pain types for effective treatment. It then delves into the specific challenges of diagnosing COFP, emphasizing the need for a more nuanced approach that incorporates the biopsychosocial model. This review critically examines existing classification systems, highlighting their limitations in fully capturing COFP's multifaceted nature. It advocates for the integration of these systems with the DSM-5's Somatic Symptom Disorder code, proposing a unified, multidisciplinary diagnostic approach. This recommendation aims to improve chronic pain coding standardization and acknowledge the complex interplay of biological, psychological, and social factors in COFP. In conclusion, here, we highlight the need for a comprehensive, universally applicable classification system for COFP. Such a system would enable accurate diagnosis, streamline treatment strategies, and enhance communication among healthcare professionals. This advancement holds potential for significant contributions to research and patient care in this challenging field, offering a broader perspective for scientists across disciplines.

Similarities between explaining dizziness and explaining pain? Exploring common patient experiences, theoretical models, treatment approaches and potential therapeutic narratives for persistent dizziness or pain

Pain and dizziness are common experiences throughout the lifespan. However, nearly a quarter of those with acute pain or dizziness experience persistence, which is associated with disability, social isolation, psychological distress, decreased independence, and poorer quality of life. Thus, persistent pain or dizziness impacts peoples' lives in similarly negative ways. Conceptual models of pain and dizziness also have many similarities. Many of these models are more expansive than explaining mere symptoms; rather they describe pain or dizziness as holistic experiences that are influenced by biopsychosocial and contextual factors. These experiences also appear to be associated with multi-modal bodily responses related to evaluation of safety, threat detection and anticipation, as influenced by expectations, and predictions anticipation, not simply a reflection of tissue injury or pathology. Conceptual models also characterize the body as adaptable and therefore capable of recovery. These concepts may provide useful therapeutic narratives to facilitate understanding, dethreaten the experience, and provide hope for patients. In addition, therapeutic alliance, promoting an active movement-based approach, building self-efficacy, and condition-specific approaches can help optimize outcomes. In conclusion, there are significant overlaps in the patient experience, theoretical models and potential therapeutic narratives that guide care for people suffering with persistent pain or dizziness.

"I did not expect the doctor to treat a ghost": a systematic review of published reports regarding chronic postamputation pain in British First World War veterans

Limb trauma remains the most prevalent survivable major combat injury. In the First World War, more than 700,000 British soldiers received limb wounds and more than 41,000 underwent an amputation, creating one of the largest amputee cohorts in history. Postamputation pain affects up to 85% of military amputees, suggesting that up to 33,000 British First World War veterans potentially reported postamputation pain. This qualitative systematic review explores the professional medical conversation around clinical management of chronic postamputation pain in this patient cohort, its development over the 20th century, and how this information was disseminated among medical professionals. We searched The Lancet and British Medical Journal archives (1914-1985) for reports referring to postamputation pain, its prevalence, mechanisms, descriptors, or clinical management. Participants were First World War veterans with a limb amputation, excluding civilians and veterans of all other conflicts. The search identified 9809 potentially relevant texts, of which 101 met the inclusion criteria. Reports emerged as early as 1914 and the discussion continued over the next 4 decades. Unexpected findings included early advocacy of multidisciplinary pain management, concerns over addiction, and the effect of chronic pain on mental health emerging decades earlier than previously thought. Chronic postamputation pain is still a significant issue for military rehabilitation. Similarities between injury patterns in the First World War and recent Iraq and Afghanistan conflicts mean that these historical aspects remain relevant to today's military personnel, clinicians, researchers, and policymakers.

The role of micro-RNAs in neuropathic pain-a scoping review

Neuropathic pain can be caused by a lesion or disease of the somatosensory system characterised by pathological neuro-immune alterations. At a molecular level, microRNAs (miRNAs) act as regulators of gene expression orchestrating both immune and neuronal processes. Thus, miRNAs may act as essential modulators of processes for the establishment and maintenance of neuropathic pain. The objective/aims of this scoping review was to explore and chart the literature to identify miRNAs that are dysregulated in neuropathic pain. The following databases were searched from inception to March 2023: PubMed, EBSCO, CINAHL, Cochrane Library, and SCOPUS. Two independent reviewers screened, extracted data, and independently assessed the risk of bias in included studies. The JBI critical appraisal checklist was used for critical appraisal. A narrative synthesis was used to summarise the evidence. Seven studies (total of 384 participants) that met our eligibility criteria were included in this scoping review. Our review has identified different miRNAs that are commonly involved in the chronic neuropathic pain conditions including miR-132, miR-101, and miR-199a. Our review findings further suggest that expression of miRNAs to be significantly associated with increased diabetic disease duration, HbA1C levels, and fibrinogen levels. Our review findings suggest that there is clear association between miRNA expression and chronic neuropathic pain conditions. Therefore, increasing the specificity by selecting a candidate miRNA and identifying its target mRNA is an area of future research.

A second dimension of somatosensory system injury? Thalamic volume loss and neuropathic pain in adults with cerebral palsy and periventricular white matter injury

Objectives

Lemniscal (motor-related) and spinothalamic (neuropathic pain-related) somatosensory abnormalities affect different subsets of adults with cerebral palsy (CP). Lemniscal/motor abnormalities are associated with posterior thalamic radiation white matter disruption in individuals with CP and white matter injury. We tested the hypothesis that neuropathic pain symptoms in this population are rather associated with injury of the somatosensory (posterior group nuclei) thalamus.

Methods

In this cross-sectional study, communicative adults with CP and bilateral white matter injury and neurotypical control participants volunteered to self-report pain symptoms and undergo research MRI. Posterior group thalamic nuclei volume was computed and correlated against neuropathic pain scores.

Results

Participants with CP (n=6) had, on average, 24% smaller posterior group thalamic volumes (95% CI [10-39%]; corrected p=0.01) than control participants. More severe volume loss was correlated with more severe neuropathic pain scores (ρ=-0.87 [-0.99,-0.20]; p=0.02).

Discussion

Association with thalamic volume loss suggests that neuropathic pain in adults with CP may frequently be central neuropathic pain. Complementing assessments of white matter microstructure, regional brain volumes hold promise as diagnostic biomarkers for central neuropathic pain in individuals with structural brain disorders.

Integration of microbiota and metabolomics reveals the analgesic mechanisms of emodin against neuropathic pain

BACKGROUND AND OBJECTIVE

Neuropathic pain (NeP) induced dysbiosis of intestinal microbiota in chronic constriction injury (CCI) rats. Emodin has analgesic effect but the detailed mechanism is not clear at the present time. This study aims to explore the underling mechanism of action of emodin against NeP with in CCI model.

METHODS

Male SD rats (180-220 g) were randomly divided into three groups: sham group, CCI group, and emodin group. Behavioral tests were performed to evaluate the therapeutic effects of emodin on CCI model. Feces and spinal cords of all rats were collected 15 days after surgery. 16S rDNA sequencing, untargeted metabolomics, qPCR and ELISA were performed.

RESULTS

Mechanical withdrawal thresholds (MWT), thermal withdrawal latency (TWL) and Sciatic functional index (SFI) in emodin group were significantly higher than CCI group (P < 0.05). Emodin not only inhibited the expression of pro-inflammatory cytokines in the spinal cords and colonic tissue, but also increased the expression of tight junction protein in colonic tissue. 16S rDNA sequencing showed that emodin treatment changed the community structure of intestinal microbiota in CCI rats. Untargeted metabolomics analysis showed that 33 differential metabolites were screened out between CCI group and emodin group. After verification, we found that emodin increased the level of S-adenosylmethionine (SAM) and Histamine in the spinal cord of CCI rats.

CONCLUSION

Emodin was effective in relieving neuropathic pain, which is linked to inhibition inflammatory response, increasing the proportion of beneficial bacteria and beneficial metabolites.

Do baseline patient reported outcome measures predict changes in self-reported function, following a chronic pain rehabilitation programme?

Background

Interdisciplinary pain management programmes, based on cognitive-behavioural principles, aim to improve physical and psychological functioning and enhance self-management in people living with chronic pain. Currently there is insufficient evidence about whether psychological, biological or social factors are predictive of positive outcomes following pain rehabilitation. This study aims to evaluate predictors of change in Brief Pain Inventory - pain interference score (BPI) in a clinical data set to determine whether age, sex and baseline outcome measures are predictive of improvement in pain interference following pain rehabilitation.

Methods

A retrospective, pragmatic observational analysis of routinely collected clinical data in two pain rehabilitation programmes, Balanced Life Programme (BLP) and Get Back Active (GBA) was conducted. Standard regression and hierarchical regression analyses were used to identify predictors of change to assess temporal changes in BPI. Responder analysis was also conducted.

Results

Standard regression analyses of 208 (BLP) and 310 (GBA) patients showed that higher baseline BPI and better physical performance measures predicted better improvement in BPI across both programmes. Hierarchical regression showed that age and sex accounted for 2.7% (BLP) and 0.002% (GBA) of the variance in change in BPI. After controlling for age and sex, the other measures explained an additional 23% (BLP) and 19% (GBA) of the variance, p = < .001 where BPI and physical performance measures were consistently statistically significant predictors, p < .05. Responder analysis also showed that pain interference and physical performance were significantly associated with improvement (p = < .0005).

Conclusions

The combination of high self-reported pain interference and better physical performance measures may be a useful indicator of who would benefit from interdisciplinary rehabilitation. Further validation of the results is required.

Application of PainDETECT in pediatric chronic pain: how well does it identify neuropathic pain and its characteristics?

Introduction

Neuropathic pain (NP) arises from nerve damage or disease, and when not defined, it can impair function and quality of life. Early detection allows for interventions that can enhance outcomes. Diagnosis of NP can be difficult if not properly evaluated. PainDETECT is a NP screening tool developed and successfully used in adults.

Objectives

We evaluated the validity of painDETECT in a pediatric population.

Methods

Adolescents and young adults (10-19 years old) completed painDETECT and quantitative sensory testing (QST), which assessed mechanical allodynia and hyperalgesia, common symptoms of NP. Pain diagnoses, including neuropathic pain (n = 10), were collected through documentation in the medical chart. Descriptive statistics were used to examine age, gender, pain diagnoses, and painDETECT scores. Kruskal-Wallis H tests were conducted to examine differences in QST results across painDETECT categorizations.

Results

Youth with chronic pain (N = 110, Mage = 15.08 ± 2.4 years, Nfemale = 88) and peers without pain (N = 55, Mage = 15.84 ± 3.9 years, Nfemale = 39) completed the painDETECT. The painDETECT scores for youth with pain (M = 12.7 ± 6.76) were significantly higher than those for peers without pain (M = 2.05 ± 2.41). PainDETECT demonstrated 80% sensitivity and 33% specificity in a pediatric population. Individuals who screened positively on the PainDETECT had significantly higher mechanical allodynia (M = 0.640 ± 0.994) compared with those who screened negatively (M = 0.186 ± 0.499; P = 0.016).

Conclusion

PainDETECT demonstrated the ability to screen for NP, and QST mechanical allodynia results were consistent with a positive NP screen. Results of the study offer preliminary support for the ongoing assessment of the painDETECT as a brief, inexpensive, and simple-to-use screening tool for pediatric patients with primary pain complaints.

Temporary Peripheral Nerve Stimulation as Treatment for Chronic Pain

INTRODUCTION

Chronic pain is a growing problem across the world, and in the midst of an opioid epidemic, it is imperative that alternative treatment measures are identified to help alleviate the pain experienced by these patients. Chronic pain greatly affects ones quality of life and many patients do not experience adequate relief with conventional treatment measures. The purpose of this retrospective analysis is to assess the efficacy of peripheral nerve stimulation (PNS) therapy in adult patients suffering from chronic pain refractory to conventional treatment measures who underwent therapy on various anatomical locations.

METHODS

This retrospective analysis consisted of data collected from electronic health records for n = 89 patients who underwent PNS therapy. Data collected relates to patient age, sex, weight, height, body mass index (BMI), diagnosis, targeted nerves, follow-up encounters, pain scores from before and after PNS therapy, and duration of improvement. Statistical analysis used SPSS software, version 26 (IBM), using a paired t test to assess significance between pre and post PNS therapy pain scores. P values were significant if found to be ≤ 0.05. Further analysis assessed the correlation between age and BMI with visual analog scale (VAS) pain improvement and subjective percentage pain relief.

RESULTS

The mean pre-operative (pre-op) pain score before PNS therapy was 6.36 (standard deviation (SD) = 2.18, SEM = 0.23) and the mean post-operative (post-op) pain score after PNS therapy was 4.19 (SD = 2.70, SEM = 0.29). The mean patient-reported percent improvement in pain following PNS therapy was 49.04% (SD = 34.79). The improvement in pain scores between pre-op and post-op was statistically significant (M = 2.17, SD = 2.82, SEM = 0.30, t(88) = 7.26, p < .001), 95% confidence interval (CI) [1.57, 2.76]. The mean duration of improvement for patients was 123 days after therapy initiation (min = 6, max = 683, SD = 126).

CONCLUSIONS

This study demonstrated the potential role for PNS therapy in improving patient-reported pain levels for various neuropathies, targeting various nerves. With PNS therapy's use as a chronic pain treatment and available research being limited, further study needs to be done on the efficacy of PNS therapy for pain management and complications associated with PNS device placements at various locations.

Anomalies in the review process and interpretation of the evidence in the NICE guideline for chronic fatigue syndrome and myalgic encephalomyelitis

Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is a disabling long-term condition of unknown cause. The National Institute for Health and Care Excellence (NICE) published a guideline in 2021 that highlighted the seriousness of the condition, but also recommended that graded exercise therapy (GET) should not be used and cognitive-behavioural therapy should only be used to manage symptoms and reduce distress, not to aid recovery. This U-turn in recommendations from the previous 2007 guideline is controversial.We suggest that the controversy stems from anomalies in both processing and interpretation of the evidence by the NICE committee. The committee: (1) created a new definition of CFS/ME, which 'downgraded' the certainty of trial evidence; (2) omitted data from standard trial end points used to assess efficacy; (3) discounted trial data when assessing treatment harm in favour of lower quality surveys and qualitative studies; (4) minimised the importance of fatigue as an outcome; (5) did not use accepted practices to synthesise trial evidence adequately using GRADE (Grading of Recommendations, Assessment, Development and Evaluations trial evidence); (6) interpreted GET as mandating fixed increments of change when trials defined it as collaborative, negotiated and symptom dependent; (7) deviated from NICE recommendations of rehabilitation for related conditions, such as chronic primary pain and (8) recommended an energy management approach in the absence of supportive research evidence.We conclude that the dissonance between this and the previous guideline was the result of deviating from usual scientific standards of the NICE process. The consequences of this are that patients may be denied helpful treatments and therefore risk persistent ill health and disability.

The pathogenesis of painful diabetic neuropathy and clinical presentation

Diabetic neuropathy is a common complication of diabetes that affects up to 50% of patients during the course of the disease; 20-30% of the patients also develop neuropathic pain. The mechanisms underlying neuropathy are not known in detail, but both metabolic and vascular factors may contribute to the development of neuropathy. The development of the most common type of neuropathy is insidious, often starting distally in the toes and feet and gradually ascending up the leg and later also involving fingers and hands. The symptoms are mainly sensory with either sensory loss or positive symptoms with different types of paresthesia or painful sensations. In more advanced cases motor dysfunction may occur, causing gait disturbances and falls. The diagnosis of neuropathy is based on history and a careful examination, which includes a sensory examination of both large and small sensory nerve fiber function, as well as an examination of motor function and deep tendon reflexes of the lower limbs. Attention needs to be paid to the feet including examination of the skin, joints, and vascular supply. Nerve conduction studies are rarely needed to make a diagnosis of neuropathy. In patients with clear motor deficit or with an asymmetrical presentation, additional electrophysiological examination may be necessary. Early detection of diabetic neuropathy is important to avoid further irreversible injury to the peripheral nerves.

Aerobic Exercise and Neuropathic Pain: Insights from Animal Models and Implications for Human Therapy

This narrative review explores the complex relationship between aerobic exercise (AE) and neuropathic pain (NP), particularly focusing on peripheral neuropathies of mechanical origin. Pain, a multifaceted phenomenon, significantly impacts functionality and distress. The International Association for the Study of Pain's definition highlights pain's biopsychosocial nature, emphasizing the importance of patient articulation. Neuropathic pain, arising from various underlying processes, presents unique challenges in diagnosis and treatment. Our methodology involved a comprehensive literature search in the PubMed and SCOPUS databases, focusing on studies relating AE to NP, specifically in peripheral neuropathies caused by mechanical forces. The search yielded 28 articles and 1 book, primarily animal model studies, providing insights into the efficacy of AE in NP management. Results from animal models demonstrate that AE, particularly in forms like no-incline treadmill and swimming, effectively reduces mechanical allodynia and thermal hypersensitivity associated with NP. AE influences neurophysiological mechanisms underlying NP, modulating neurotrophins, cytokines, and glial cell activity. These findings suggest AE's potential in attenuating neurophysiological alterations in NP. However, human model studies are scarce, limiting the direct extrapolation of these findings to human neuropathic conditions. The few available studies indicate AE's potential benefits in peripheral NP, but a lack of specificity in these studies necessitates further research. In conclusion, while animal models show promising results regarding AE's role in mitigating NP symptoms and influencing underlying neurophysiological mechanisms, more human-centric research is required. This review underscores the need for targeted clinical trials to fully understand and harness AE's therapeutic potential in human neuropathic pain, especially of mechanical origin.

The impact of time from injury to surgery on the risk of neuropathic pain after traumatic spinal cord injury

Traumatic spinal cord injury (SCI) is a devastating neurological disorder often accompanied by neuropathic pain (NeP), significantly affecting patients' quality of life. This retrospective study aimed to investigate the impact of the time from injury to surgery on the development of NeP following traumatic SCI. Medical records of patients with traumatic SCI who underwent surgical intervention between January 2017 and January 2021 at two specialized centers were reviewed. Variables associated with NeP including demographics, injury profiles, medical history, surgical details, and pain assessments were investigated. Independent risk factors related to NeP were identified using multivariate logistic regression analysis. A total of 320 patients met the inclusion criteria, with 245 (76.6%) being male and a mean age of 56.5 ± 13.2 years. NeP was identified in 48.4% of patients (155 of 320). The multivariate analysis identifies age at injury, Injury Severity Score, and the neurological level of injury as independent risk factors for the development of NeP in both AIS A and AIS B, C, and D subgroups. Additionally, a significant association between the time from injury to surgery and NeP was observed in AIS B, C, and D patients, while no such association was found in AIS A patients. This study highlights the benefits of early and ultra-early surgical intervention in preventing NeP in patients with incomplete traumatic SCI (AIS B, C, and D), underscoring the importance of optimizing surgical timing to improve patient outcomes. Prospective studies are warranted to establish evidence-based surgical guidelines for managing traumatic SCI and preventing NeP effectively.

The relationship between neuropathic pain and the outcomes of minimally invasive pain management in rotator cuff ruptures

This study aimed to investigate how the presence of neuropathic pain related to partial rotator cuff tears affects the short-term results of subacromial injection and suprascapular nerve blockade therapy in patients with chronic shoulder pain. In this prospective observational study, shoulder pain via verbal numeric pain rating (VNPR, 0-10) and functional status through simple shoulder test (SST) were evaluated before and second week after procedure. After dividing as neuropathic pain and non-neuropathic pain groups, pre-procedural and follow-up scores concerning pain intensity, functional status, and whether there were those of patients with minimal clinically important change (MCIC) in areas of pain and function were evaluated. Between the groups including 140 patients, while there was no statistical difference in baseline pain intensity and functional status (P = .14,.11, respectively), outcomes of those without neuropathic pain were favored at the follow-up (P = .02,.01, respectively). Given baseline pain scores, the reduction (%) was significantly lower in neuropathic pain group (P = .03). There was no significant difference in patients with MCIC in pain intensity and functional status between the groups (P = .08,.59, respectively). An improvement was determined in pain intensity and functional status at the follow-up in both groups (P < .001). The improvement in pain intensity and functional status is poorer in patients with partial rotator cuff rupture-related neuropathic pain than in those without neuropathic pain. However neuropathic pain has no negative effect on the response to treatment.

Some suggestions for pain physicians working in real-world clinical settings

Musculoskeletal pain is a common reason for patients visiting hospitals or clinics. Various therapeutic tools including oral medications, physical modalities, and procedures have been used to alleviate musculoskeletal pain. Numerous clinical trials have been conducted to demonstrate the therapeutic effect of each treatment and compare the efficacy of different protocols. These trials were conducted under controlled conditions with specific endpoints and timeframes, and the individual constraints of each patient were not considered. We believe that the findings of such studies may not accurately reflect clinical reality in real-world settings. In this article, we propose treatment principles for patients in pain clinics. We propose two principles for pain treatment: first, "Healing, in the end, is not healing." and second, "The patient's job is not a patient." The main role of pain physicians is to quickly and actively reduce pain and help patients focus on their work and lives.

Educational initiatives and achievements of the International Association for the Study of Pain

ABSTRACT

This article summarizes the many initiatives and achievements of the International Association for the Study of Pain (IASP) in pain education worldwide since 1973. These range from major events such as the World Congress on Pain that attracts thousands of attendees to the more intimate and focused Pain Schools and Pain Camps. The article describes how education has been a key focus of IASP since its inception and how IASP has responded to its members' desire for access to the latest knowledge about pain and evidence-based pain treatments. The unique contribution of IASP to the study of pain is reflected in its consistent focus on a biopsychosocial approach to pain, the promotion of interactions between basic scientists and clinicians, as well as multidisciplinary and interdisciplinary collaborations. Details of these rich offerings can be found on the IASP web site, and this article provides a guide for those seeking to access them.

Neuropathy in prediabetes

Diabetic neuropathies are the most frequent complications of diabetes, contributing to high morbidity, excess mortality, reduced quality of life, and increased healthcare costs. Prediabetes is characterised by glucose levels within an intermediate range above normoglycaemia yet below the diagnostic threshold for diabetes. In 2021, 10.6% and 6.2% of adults worldwide were estimated to have impaired glucose tolerance and impaired fasting glucose, respectively, the majority of whom are unaware of having prediabetes. Evidence has accumulated suggesting that prediabetes is a predictor of cardiovascular disease (CVD) and increased mortality. The past 2 decades have witnessed an extensive debate, particularly among diabetologists and neurologists, as to whether prediabetes is associated with peripheral neuropathy. In this review, we elaborate on the current evidence, particularly from population-based studies supporting an increased risk of distal sensorimotor polyneuropathy (DSPN) and cardiovascular autonomic neuropathy (CAN) in people with prediabetes. Moreover, we discuss whether lifestyle interventions showing efficacy in preventing or delaying the transition from prediabetes to diabetes in persons with prediabetes may also exert favourable effects on the development and progression of DSPN and CAN. This review should help in raising the awareness of and translating the current knowledge on neuropathies in people with prediabetes into clinical practice and public health. The current recommendation that adults who are overweight or obese should be screened for prediabetes and referred to or offered preventive interventions should ultimately culminate in preventing not only CVD but also prediabetic neuropathy.

Neuropathic pain: From actual pharmacological treatments to new therapeutic horizons

Neuropathic pain, caused by a lesion or disease affecting the somatosensory system, affects between 3 and 17% of the general population. The treatment of neuropathic pain is challenging due to its heterogeneous etiologies, lack of objective diagnostic tools and resistance to classical analgesic drugs. First-line treatments recommended by the Special Interest Group on Neuropathic Pain (NeuPSIG) and European Federation of Neurological Societies (EFNS) include gabapentinoids, tricyclic antidepressants (TCAs) and selective serotonin noradrenaline reuptake inhibitors (SNRIs). Nevertheless these treatments have modest efficacy or dose limiting side effects. There is therefore a growing number of preclinical and clinical studies aim at developing new treatment strategies to treat neuropathic pain with better efficacy, selectivity, and less side effects. In this review, after a brief description of the mechanisms of action, efficacy, and limitations of current therapeutic drugs, we reviewed new preclinical and clinical targets currently under investigation, as well as promising non-pharmacological alternatives and their potential co-use with pharmacological treatments.

Association of concomitant continuous pain in trigeminal neuralgia with a narrow foramen ovale

Background

The pathogenesis of concomitant continuous pain remains unclear and is worthy of further study. In this clinical study, we aimed to explore the potential role of a narrow foramen ovale in the development of concomitant continuous pain.

Methods

A total of 108 patients with classical trigeminal neuralgia affecting the third branch of the trigeminal nerve and 46 healthy individuals were enrolled in this study. Three-dimensional reconstructed computerized tomography images of all participants were collected, and the morphometric features of the foramen ovale were examined by two investigators who were blinded to the clinical data of the patients.

Results

In this cohort, patients with concomitant continuous pain suffered from more sensory abnormalities (18.4% vs. 2.9%, p = 0.015) and responded more poorly to medication (74.3% vs. 91.9%, p = 0.018) than patients without concomitant continuous pain. While no significant differences regarding the mean length (5.02 mm vs. 5.36 mm, p > 0.05) and area (22.14 mm2 vs. 23.80 mm2, p > 0.05) were observed between patients with and without concomitant continuous pain, the mean width of the foramen ovale on the affected side in patients with concomitant continuous pain was significantly narrower than that in patients without concomitant continuous pain (2.01 mm vs. 2.48 mm, p = 0.003).

Conclusion

This neuroimaging and clinical study demonstrated that the development of concomitant continuous pain was caused by the compression of the trigeminal nerve owing to a narrow foramen ovale rather than responsible vessels in classical trigeminal neuralgia.

Serum Inflammatory Cytokine Levels in Herpes Zoster Patients and Their Association with Postherpetic Neuralgia: A Prospective Study

BACKGROUND This study aimed to investigate the serum levels of inflammatory cytokines in patients with herpes zoster (HZ) and to assess their correlation with the development of postherpetic neuralgia (PHN). Understanding this relationship may offer insight into the mechanisms of PHN and provide avenues for targeted treatment. MATERIAL AND METHODS We selected 169 patients diagnosed with HZ and 43 healthy controls (HCs) for the study. Serum levels of inflammatory cytokines were measured in all participants. Pain severity was evaluated using the visual analog scale (VAS). Based on follow-up data, the 169 HZ patients were categorized into 2 groups: those who developed PHN (HZ-PHN) and those who did not (HZ-Con). We then analyzed the differences in cytokine levels and their correlation with PHN development. RESULTS Compared to the HCs group, HZ patients exhibited a significant decrease in TNF-a levels and an increase in IL-10 levels (P<0.05, P<0.01). The VAS score was negatively correlated with TNF-alpha levels and positively correlated with IL-10 levels in HZ patients (r=-0.3081, P<0.01; r=0.5619, P<0.01). Distinctive levels of TNF-alpha, IL-6, IL-8, and IL-10 were observed among different pain groups (P<0.05, P<0.01). The HZ-PHN group showed lower TNF-alpha and higher IL-10 levels compared to the HZ-Con group (P<0.05, P<0.01). IL-10 level was identified as an independent risk factor for PHN, with a sensitivity and specificity of 76.4% and 54.3%, respectively. CONCLUSIONS Abnormal levels of inflammatory cytokines are present in HZ patients, and the IL-10 level may serve as a valuable indicator for predicting the risk of developing PHN.

GFAP-NpHR mediated optogenetic inhibition of trigeminal nucleus caudalis attenuates hypersensitive behaviors and thalamic discharge attributed to infraorbital nerve constriction injury

The significance of hyperactive astrocytes in neuropathic pain is crucial. However, the association between medullary astrocytes and trigeminal neuralgia (TN)-related pain processing is unclear. Here, we examined how optogenetic inhibition of medullary astrocytes in the trigeminal nucleus caudalis (TNC) regulates pain hypersensitivity in an infraorbital nerve (ION) constricted TN model. We used adult Sprague Dawley rats subjected to infraorbital nerve (ION) constriction to mimic TN symptoms, with naive and sham rats serving as controls. For in vivo optogenetic manipulations, rats stereotaxically received AAV8-GFAP-eNpHR3.0-mCherry or AAV8-GFAP-mCherry at the trigeminal nucleus caudalis (TNC). Open field, von Frey, air puff, and acetone tests measured pain behavioral flexibility. In vivo thalamic recordings were obtained simultaneously with optogenetic manipulation in the TNC. Orofacial hyperalgesia and thalamic hyperexcitability were both accompanied by medullary astrocyte hyperactivity, marked by upregulated GFAP. The yellow laser-driven inhibition of TNC astrocytes markedly improved behavioral responses and regulated thalamic neuronal responses. Halorhodopsin-mediated inhibition in medullary astrocytes may modify the nociceptive input transmitted through the trigeminothalamic tract and pain perception. Taken together, these findings imply that this subpopulation in the TNC and its thalamic connections play a significant role in regulating the trigeminal pain circuitry, which might aid in the identification of new therapeutic measures in TN management.

Chronic pain among Lebanese individuals with spinal cord injury: Pain interference and impact on quality of life

Background: Chronic pain is one of the most disabling consequences of spinal cord injury (SCI). Although studies have identified a link between chronic pain and decreased quality of life (QOL) among this population, few studies have looked into the experience of chronic pain in Lebanese individuals with SCI and the impact of pain characteristics on QOL. Thus, the present study evaluated the chronic pain experience and its associated factors among Lebanese individuals with SCI in order to determine the impact of pain on QOL. Methods: A cross-sectional study was conducted on 81 Lebanese individual with SCI between August 1st and October 31, 2022. The collected information included sociodemographic characteristics, SCI-related information, pain-related variables, and the 12-item Short Form Health Survey (SF-12). Factors associated with pain interference were evaluated using a linear regression model. One-way ANOVA and independent sample t-test were used to evaluate the association of different baseline and pain characteristics with QOL. Results: In the present study, 81.5% of participants reported chronic pain with the majority of them having neuropathic pain type. Employment status (P = 0.034), type of pain (P = 0.009), and pain severity (P = 0.028) were significantly associated with pain interference. Unemployed participants and those with severe chronic pain, particularly neuropathic pain, had lower QOL. Conclusion: Chronic pain was found to be highly prevalent among Lebanese patients with SCI. Pain interference and QOL were significantly affected by employment status and pain type. Therefore, targeting chronic pain and its associated factors in rehabilitation practice is warranted.

Patients with Chronic Pain: Are Mindfulness Traits Protective Against Distress, Anxiety and Depression?

OBJECTIVE

To investigate mindfulness traits/attitudes as protective factors against chronic pain related distress, depression and anxiety.

METHOD

Fifty patients (25 with chronic non-oncologic pain-NOP; 25 with chronic oncologic pain-COP) were administered with the following scales: Visual Analogue Scale (VAS), Pain Disability Index (PDI), Italian Questionnaire for Pain (QUID), Perceived Stress Scale (PSS), State and Trait Anxiety Scale (STAY-y1 module), Beck Depression Inventory II (BDI-II), Pittsburgh Sleep Quality Index (PSQI), Psychological General Well Being Index (PGWBI), Mindful Attention Awareness Scale (MAAS).

RESULTS

MAAS value ≥ 4.38 was adopted as cut-off to compare 'high level of mindfulness' (HM) vs. 'normal level of mindfulness' (NM) attitudes. Twenty-six patients (52%) scored ≥4.38, with no different distribution between NOP and COP. HM patients scored significantly lower than NM patients on PDI 'family/home responsibilities' domain (4.5±3.2 vs. 6.4±2.8; p<.037), and on PSS (17.8±2.6 vs. 20.9±2.5; p<.0001), STAY-y1 (9.4±1.8 vs. 10.3±2.1; p<.0001), BDI-II (7.8±5.0 vs. 17.6±8.6; p<.0001) total scores. HM scored significantly higher than NM patients in all PGWBI domains. A multiple regression analysis was carried out to analyze the predictor variables of PGWB. The most complete model considered the variables MAAS, STAIy and VAS (F=42.21; p<.0001), that accounted for the 71.6% of PGWB variance. MAAS score was the only variable positively predicting for PGWB; STAIy and VAS scores predicted negatively.

CONCLUSIONS

Chronic pain patients with high levels of mindfulness attitudes experienced less distress, anxiety, depressive symptoms, and more physical and general wellbeing than patients with low levels of mindfulness attitudes.

Dorsal Root Entry Zone Lesioning Following Unresponsive Spinal Cord Stimulation for Post-Traumatic Neuropathic Pain

OBJECTIVE

Spinal cord stimulation (SCS) and dorsal root entry zone (DREZ) lesioning are important therapeutic options for intractable post-traumatic neuropathic pain (PNP). However, surgical choice is controversial due to the need to maximize pain relief and reduce complications. This study aims to retrospectively analyze the effect and complications of DREZ lesioning for patients with PNP who were unresponsive to SCS and provide a surgical reference.

METHODS

Demographic data and surgical characteristics of patients with PNP who underwent DREZ lesioning after an unresponsive SCS were reviewed. Long-term outcomes including numeric rating scale, global impression of change, and long-term complications were assessed. Kaplan-Meier analysis was used to evaluate pain-free survival.

RESULTS

Of 19 patients with PNP, 8 had brachial plexus injury (BPI), 7 had spinal cord injury, 2 had cauda equina injury, 1 had intercostal nerve injury, and 1 had lumbosacral plexus injury. All patients were unresponsive or had a recurrence of pain after SCS, with an average pain-relief rate of 9.3%. After DREZ lesioning, the mean numeric rating scale scores significantly decreased from 7.6 ± 1.5 to 1.8 ± 1.7, with an average pain-relief rate of 75.3%. Seven patients (36.8%) experienced worsened neurologic dysfunction at the last follow-up. Patients with BPI had a significantly better outcome than other pathologies (P < 0.001) after DREZ lesioning.

CONCLUSIONS

DREZ lesioning is an effective alternative procedure to SCS for patients with PNP who have lost limb function. Particularly for those with BPI, DREZ lesioning has shown good efficacy and can be considered a preferred surgical option.

Electroacupuncture Alleviates Neuropathic Pain by Suppressing Ferroptosis in Dorsal Root Ganglion via SAT1/ALOX15 Signaling

Neuropathic pain affects globally about 7-10% of the general population. Electroacupuncture (EA) effectively relieves neuropathic pain symptoms without causing any side effects; however, the underlying molecular mechanisms remain unclear. We established a chronic constriction injury (CCI)-induced rat model of neuropathic pain. RNA sequencing was used to screen for differentially expressed genes in the dorsal root ganglion after CCI and EA treatment. We identified gene markers of ferroptosis spermidine/spermine N1-acetyltransferase 1 (Sat1) and arachidonate 15-lipoxygenase (Alox15) to be dysregulated in the CCI-induced neuropathic pain model. Furthermore, EA relieved CCI-induced pain as well as ferroptosis-related symptoms in the dorsal root ganglion, including lipid peroxidation and iron overload. Finally, SAT1 knockdown also alleviated mechanical and thermal pain hypersensitivity and reversed ferroptosis damage. In conclusion, we showed that EA inhibited ferroptosis by regulating the SAT1/ALOX15 pathway to treat neuropathic pain. Our findings provide insight into the mechanisms of EA and suggest a novel therapeutic target for neuropathic pain.

Precision management of post-COVID pain: An evidence and clinical-based approach

Background Pain after a SARS-CoV-2 acute infection (post-COVID pain) is becoming a new healthcare emergency but remains underestimated and most likely undertreated due to a lack of recognition of the phenomenon and knowledge of the underlying pain mechanisms. Evidence supporting any particular treatment approach for the management of post-COVID pain is lacking. Large variability in the patient response to any standard pain treatments is clinically observed, which has led to calls for a personalized, tailored approach to treating patients with chronic post-COVID pain (i.e. 'precision pain medicine'). Applying the global concerted action towards precision medicine to post-COVID pain could help guide clinical decision-making and aid in more effective treatments. Methods The current position paper discusses factors to be considered by clinicians for managing post-COVID pain ranging from identification of the pain phenotype to genetic consideration. Results The ability of clinicians to phenotype post-COVID pain into nociceptive, neuropathic, nociplastic or mixed type is suggested as the first step to better planification of a treatment programme. Further, the consideration of other factors, such as gender, comorbidities, treatments received at the acute phase of infection for onset-associated COVID-19 symptoms, factors during hospitalization or the presence of emotional disturbances should be implemented into a treatment programme. Conclusions Accordingly, considering these factors, management of post-COVID pain should include multimodal pharmacological and non-pharmacological modalities targeting emotional/cognitive aspects (i.e. psychological and/or coping strategies), central sensitization-associated mechanisms (i.e. pain neuroscience education), exercise programmes as well as lifestyle interventions (e.g. nutritional support and sleep management). SIGNIFICANCE: This position paper presents an evidence-based clinical reasoning approach for precision management of post-COVID pain.

Pain-motor integration in chronic pain: A neurophysiological study

OBJECTIVE

Chronic pain may lead to functional changes in several brain regions, including the primary motor cortex (M1). Our neurophysiological study aimed to probe M1 plasticity, through a non-invasive transcranial magnetic stimulation protocol, in a cohort of patients with chronic pain.

METHODS

Twenty patients with chronic pain (age ± SD: 62.9 ± 9.9) and 20 age- and sex-matched healthy controls (age ± SD: 59.6 ± 15.8) were recruited. Standardized scales were used for the evaluation of pain severity. Neurophysiological measures included laser-evoked potentials (LEPs) and motor-evoked potentials (MEPs) collected at baseline and over 60 minutes following a standardized Laser-paired associative stimulation (Laser-PAS) protocol.

RESULTS

LEPs and MEPs were comparable in patients with chronic pain and controls. The pain threshold was lower in patients than in controls. Laser-PAS elicited decreased responses in patients with chronic pain. The response to Laser-PAS was similar in subgroups of patients with different chronic pain phenotypes.

CONCLUSIONS

M1 plasticity, as tested by Laser-PAS, is altered in patients with chronic pain, possibly reflecting abnormal pain-motor integration processes.

SIGNIFICANCE

Chronic pain is associated with a disorder of M1 plasticity raising from abnormal pain-motor integration.

Repetitive transcranial magnetic stimulation in central post-stroke pain: current status and future perspective

Central post-stroke pain (CPSP) is an incapacitating disorder that impacts a substantial proportion of stroke survivors and can diminish their quality of life. Conventional therapies for CPSP, including tricyclic antidepressants, anticonvulsants, and opioids, are frequently ineffective, necessitating the investigation of alternative therapeutic strategies. Repetitive transcranial magnetic stimulation (rTMS) is now recognized as a promising noninvasive pain management method for CPSP. rTMS modulates neural activity through the administration of magnetic pulses to specific cortical regions. Trials analyzing the effects of rTMS on CPSP have generated various outcomes, but the evidence suggests possible analgesic benefits. In CPSP and other neuropathic pain conditions, high-frequency rTMS targeting the primary motor cortex (M1) with figure-eight coils has demonstrated significant pain alleviation. Due to its associaton with analgesic benefits, M1 is the most frequently targeted area. The duration and frequency of rTMS sessions, as well as the stimulation intensity, have been studied in an effort to optimize treatment outcomes. The short-term pain relief effects of rTMS have been observed, but the long-term effects (> 3 months) require further investigation. Aspects such as stimulation frequency, location, and treatment period can influence the efficacy of rTMS and ought to be considered while planning the procedure. Standardized guidelines for using rTMS in CPSP would optimize therapy protocols and improve patient outcomes. This review article provides an up-to-date overview of the incidence, clinical characteristics, outcome of rTMS in CPSP patients, and future perspective in the field.

Muscimol as a treatment for nerve injury-related neuropathic pain: a systematic review and meta-analysis of preclinical studies

Background

: Muscimol's quick onset and GABAergic properties make it a promising candidate for the treatment of pain. This systematic review and meta-analysis of preclinical studies aimed at summarizing the evidence regarding the efficacy of muscimol administration in the amelioration of nerve injury-related neuropathic pain.

Methods

: Two independent researchers performed the screening process in Medline, Embase, Scopus and Web of Science extracting data were extracted into a checklist designed according to the PRISMA guideline. A standardized mean difference (SMD [95% confidence interval]) was calculated for each. To assess the heterogeneity between studies, I2 and chi-square tests were utilized. In the case of heterogeneity, meta-regression and subgroup analyses were performed to identify the potential source.

Results

: Twenty-two articles met the inclusion criteria. Pooled data analysis showed that the administration of muscimol during the peak effect causes a significant reduction in mechanical allodynia (SMD = 1.78 [1.45-2.11]; P < 0.0001; I2 = 72.70%), mechanical hyperalgesia (SMD = 1.62 [1.28-1.96]; P < 0.0001; I2 = 40.66%), and thermal hyperalgesia (SMD = 2.59 [1.79-3.39]; P < 0.0001; I2 = 80.33%). This significant amendment of pain was observed at a declining rate from 15 minutes to at least 180 minutes post-treatment in mechanical allodynia and mechanical hyperalgesia, and up to 30 minutes in thermal hyperalgesia (P < 0 .0001).

Conclusions

: Muscimol is effective in the amelioration of mechanical allodynia, mechanical hyperalgesia, and thermal hyperalgesia, exerting its analgesic effects 15 minutes after administration for up to at least 3 hours.

Making chronic pain count: empirical support for the ICD-11 classification of chronic pain

PURPOSE OF REVIEW

The purpose is to review the evidence that has been collected with regard to the new classification of chronic pain. In 2022, the World Health Assembly endorsed the 11 th revision of the International Classification of Diseases and Related Health Problems (ICD-11), and with it a new classification of chronic pain.

RECENT FINDINGS

The evidence from the formative field testing indicated that the categories were clearly delineated and the coverage of chronic pain excellent (<3% in remainder categories). Official WHO field tests showed that the classification works well within the technical parameters WHO classifications must conform to and outperformed the ICD-10 diagnoses in all respects. International field tests, in which clinicians diagnosed consecutive patients in settings of medium and high resources, showed substantial interrater reliability (κ = 0.596 to κ = 0.783) for the diagnoses and the clinicians rated their clinical utility as very high. Studies using complete hospital records demonstrated that with the information they contain, retrospective coding of the new diagnoses is possible and provides much more meaningful information than the ICD-10 diagnoses.

SUMMARY

The evidence supports the use of the new classification and highlights its informational gains - using it will contribute to making chronic pain count in many contexts.