Peripheral neuropathic pain: a mechanism-related organizing principle based on sensory profiles

Preclinical Animal Models to Investigate the Role of Nav1.7 Ion Channels in Pain

Chronic pain is a maladaptive neurological disease that remains a major global healthcare problem. Voltage-gated sodium channels (Navs) are major drivers of the excitability of sensory neurons, and the Nav subtype 1.7 (Nav1.7) has been shown to be critical for the transmission of pain-related signaling. This is highlighted by demonstrations that gain-of-function mutations in the Nav1.7 gene SCN9A result in various pain pathologies, whereas loss-of-function mutations cause complete insensitivity to pain. A substantial body of evidence demonstrates that chronic neuropathy and inflammation result in an upregulation of Nav1.7, suggesting that this channel contributes to pain transmission and sensation. As such, Nav1.7 is an attractive human-validated target for the treatment of pain. Nonetheless, a lack of subtype selectivity, insufficient efficacy, and adverse reactions are some of the issues that have hindered Nav1.7-targeted drug development. This review summarizes the pain behavior profiles mediated by Nav1.7 reported in multiple preclinical models, outlining the current knowledge of the biophysical, physiological, and distribution properties required for a Nav1.7 inhibitor to produce analgesia.

Somatosensory profiling to differentiate distinct painful diseases of the pancreas-a quantitative sensory testing case-control study

ABSTRACT

Mechanisms of pancreatic pain are insufficiently understood, and quantitative sensory testing (QST) may help to identify the underlying mechanisms. Accordingly, this study assessed comprehensive somatosensory profiles encompassing nociceptive and nonnociceptive parameters in 70 patients with distinct pancreatic diseases, namely acute (n = 23), chronic (n = 20), or autoimmune pancreatitis (n = 10) and pancreatic cancer (n = 17) and compared it with 30 healthy control subjects by standardized QST (protocol of the German research network on neuropathic pain). Patients with pancreatic diseases presented significant somatosensory deficits in all thermal and tactile detection and pain thresholds in the pancreatic viscerotome (Th10), when compared with a remote control area (dermatome C5) or reference data of matched healthy controls (P < 0.05-P < 0.0001). Unaltered vibration detection emphasizes the strictly regional character of losses. Loss of sensitivity paralleled the occurrence of paradoxical heat sensation (Th10 vs C5; P < 0.05), an indicator of thermal integration deficit. Punctate hyperalgesia or pain to light touch, the hallmark signs of spinal central sensitization were mostly absent and pain summation remained unchanged (P > 0.05). Stratification of patients revealed that somatosensory deficits were significantly more pronounced in acute compared with chronic pancreatitis (eg, cold and warm detection thresholds: -2.19 ± 1.42 vs -1.10 ± 1.23 and -1.30 ± 1.68 vs -0.11 ± 1.80 z-values; P < 0.05 each). Notably, blunt pressure hyperalgesia, the only somatosensory parameter exhibiting significant gain compared with the patients' remote C5 segment, was a frequent finding only in acute, but not in chronic pancreatitis. The somatosensory phenotype of patients with distinct pancreatic disorders was characterized by a wide array of sensory losses being most severe in acute pancreatitis.

Neuropathic Pain: A Comprehensive Bibliometric Analysis of Research Trends, Contributions, and Future Directions

BACKGROUND

Neuropathic pain represents a significant public health concern due to its complex pathophysiology and the disability it can cause. Despite advancements in understanding its underlying mechanisms and potential treatments, challenges persist in achieving effective management. This bibliometric analysis aims to offer a comprehensive overview of research trends, key contributors, and existing gaps in the literature on neuropathic pain, providing valuable insights to guide future studies and enhance clinical approaches.

METHODS

A bibliometric analysis was conducted using the Web of Science Core Collection (WoSCC) database. Key metrics, including publication trends, citation patterns, co-authorship networks, and keyword co-occurrence, were evaluated. Statistical analyses included average annual percentage change (APC) assessments and trend forecasting with an Auto Regressive Integrated Moving Average (ARIMA) model.

RESULTS

A total of 9,974 studies published between 2005 and 2024 were included. Publications peaked between 2021 and 2022 but showed a slight decline thereafter, with forecasts predicting a steady increase from 2025 to 2030. Most papers were published in high-impact Q1 journals, reflecting the quality of research. Co-authorship analysis revealed central hubs of collaboration in the USA and China, with limited integration of smaller countries into the global research network. Keyword analysis identified multiple thematic clusters, including "chronic pain," "molecular mechanisms," and "clinical management." Specific gaps were noted in understanding personalized therapeutic approaches, and non-pharmacological interventions.

CONCLUSIONS

This analysis underscores the critical need for continued research to address gaps in diagnosis, treatment, and management of neuropathic pain. Strengthening international collaborations and fostering multidisciplinary efforts will be pivotal in advancing this field.

Characterization of Pain in Lipedema: Reliability and Validity of Pain Pressure Thresholds and Hand-Held Sphygmomanometer Assessments in People with Lipedema

Background: Lipedema is a chronic condition characterized by abnormal deposition of subcutaneous adipose tissue, leading to pain. The lack of internationally recognized diagnostic criteria complicates the characterization of pain. Physiological parameters such as pain pressure threshold (PPT) represent promising prognostic markers for diagnosing lipedema, yet they remain understudied. This study aimed to evaluate the reliability and validity of two pain pressure measurements, PPT and the hand-held sphygmomanometer (HHS) in lipedema. Methods: A total of 28 adult females diagnosed with lipedema were recruited. Both PPT, using a digital algometer, and HHS, using a manual aneroid HHS, were performed to assess pain in the lower limbs. The testing was performed in a standing position with PPT and HHS placed on the calf. Intraclass correlation coefficient (ICC) and coefficient of variation (CV) were employed to assess the within session reliability, while the validity between PPT and HHS was analyzed using R2 in a linear regression model. Results: The results showed excellent reliability for both PPT and HHS, with ICC indicating high consistency (ICC = 0.93 to 0.97) and CV showing acceptable scores (CV = 3.62% to 9.06%). In addition, good validity between PPT and HHS was also observed (R2 = 0.69 to 0.74), suggesting that HHS can be a reliable alternative to PPT for pain assessment in lipedema. Conclusion: These findings have important clinical implications, as they expand the knowledge of pain characterization in people with lipedema, potentially aiding in diagnostic refinement. In addition, a cost-effective and accessible method for assessing pain was examined (i.e., HHS), showing promising findings and providing an objective method to help diagnose lipedema.

Understanding the Impact of Diabetic Peripheral Neuropathy and Neuropathic Pain on Quality of Life and Mental Health in 6,960 People With Diabetes

OBJECTIVE

Diabetic peripheral neuropathy (DPN) and neuropathic pain impacts quality of life (QoL) and mental health negatively. This cross-sectional survey study aimed to 1) elucidate the associations between painful and painless DPN and QoL, mental health, and socioeconomic factors, 2) assess the prevalence of sensory pain descriptors, and 3) evaluate the association between descriptors and the above factors.

RESEARCH DESIGN AND METHODS

Participants were grouped into people with (n = 1,601) and without (n = 5,359) DPN based on the Michigan Neuropathy Screening Instrument questionnaire. Participants with DPN were subsequently divided into people with (n = 1,085) and without (n = 516) concomitant neuropathic pain based on the modified Douleur Neuropathique en 4 Questions-interview.

RESULTS

The study showed diminished QoL (36-item Short Form Health Survey [SF-36]: 55.1 [interquartile range 36.7, 73.6], 82.2 [63.6, 90.9]) and poorer mental health (Hospital Anxiety and Depression Scale, subscale for anxiety [HADS-A]: 5.00 [2, 9], 2.00 [1, 5]; HADS-subscale for depression [HADS-D]: 4.00 [1, 8], 1.00 [0, 3]) in participants with DPN compared with participants without DPN. The addition of pain diminished QoL (SF-36: 50.7 [34.8, 69.8]) and mental health (HADS-A: 6 [3, 10], HADS-D: 4 [1, 8]) further. The most prevalent pain descriptor in participants with painful DPN were burning pain (73%), while the most prevalent sensory descriptor was pins-and-needles (93%). An interesting finding is the high prevalence of itch (44%). Weak associations with mental health and QoL were present for cold pain, electric pain, and itch.

CONCLUSIONS

An increased focus on differences in QoL, mental health, and pain phenotypes is of importance to move the field forward toward more interdisciplinary, personalized treatment.

Pharmaceutical considerations in treating neuropathic pain in athletes

Neuropathic pain is a complex and challenging condition that arises from abnormal processing of somatosensory information, often following nerve injury or dysfunction. Its diagnosis involves a detailed clinical history, sensory examination, and diagnostic tests such as electromyography, nerve conduction studies, and MRI to identify nerve damage or structural causes. In athletes, neuropathic pain can result from nerve entrapment syndromes, post-surgical complications, or peripheral nerve injuries, with unique challenges in pain assessment due to psychological factors and exercise-induced changes. Pharmacological management primarily includes anticonvulsants (e.g., gabapentin, pregabalin) and antidepressants (e.g., tricyclics, SNRIs), tailored to minimize side effects that could impair athletic performance. Effective treatment requires a careful balance to manage pain while maintaining physical capabilities. When treating athletes for neuropathic pain, healthcare providers must ensure prescribed medications comply with World Anti-Doping Agency (WADA) regulations. Narcotics (opioids) and cannabinoids are prohibited in-competition. Glucocorticoids are also banned in-competition if administered via injection, orally, or rectally, and elevated levels in urine may lead to sanctions.

Umbilical acupuncture combined with warm needle acupuncture for the treatment of residual numbness after lumbar disc herniation surgery: a protocol of a randomized controlled trial

Background

Postoperative residual numbness following lumbar disc herniation (LDH) surgery is a relatively common symptom. Existing drugs and physical therapies are not very effective. Acupuncture is effective for the treatment of LDH, but there are limited reports on its use for postoperative numbness. Based on clinical observations and literature review, we hypothesize that combining umbilical acupuncture (UA) with warm needle acupuncture(WA) may yield superior efficacy compared to electroacupuncture(EA) alone, enhancing immune function, promoting nerve recovery, and improving microcirculation through synergistic effects, thereby filling the gap in this treatment field.

Objective

This proposed trial aimed to evaluate the effectiveness and safety of UA (umbilical acupuncture) combined with WA (warm needle acupuncture) in treating residual numbness after LDH surgery. To verify the hypothesis that the combined method is superior to traditional electroacupuncture.

Methods

This proposed study is a single-center, single-blind, prospective, randomized controlled trial (RCT) involving patients with LDH who were hospitalized and underwent percutaneous endoscopic lumbar discectomy (PELD) at our hospital. Patients meeting the inclusion criteria will be randomly assigned to either the treatment group (umbilical acupuncture combined with warm needle acupuncture) or the control group (electroacupuncture). The participants will be assessed on the first day after surgery, and acupuncture treatment will begin on the second day and continue for three consecutive days, with each session lasting 30 minutes. After that, the treatment mixture was changed three times a week for four weeks. All patients received standard Western medical drug treatment. After the treatment is concluded, a six-month follow-up will be conducted. The primary efficacy indicator will be the visual analog scale (VAS) score for numbness. The secondary efficacy indicators will include the 10 g monofilament test, 40 g pressure acupuncture sensation examination, Japanese Orthopedic Association (JOA) score, lower limb electromyography (H-reflex differences, F-wave conduction velocity, and latency), VAS score, traditional Chinese medicine symptom scoring, and Short Form 36-Health Survey (SF-36) score. Any adverse events occurring during the trial will be recorded. The data will be analyzed according to a predefined statistical analysis plan.

Discussion

This trial combines UA with WA to create a new non-invasive treatment for numbness after LDH surgery, an area where current therapies are inadequate. If proven effective, this combination therapy could offer a safer and more effective alternative to drug treatment, and provide evidence for the integration acupuncture strategies.

Clinical trial registration

http://itmctr.ccebtcm.org.cn/, identifier ITMCTR2024000328.

Neuropathic pain management: a focused review of current treatments and novel data from main ongoing clinical trials

INTRODUCTION

Neuropathic pain (NP) remains a significant challenge in clinical practice, requiring a sophisticated pharmacotherapeutic strategy for effective symptom management. This review provides a comprehensive analysis of the current pharmacological treatments for NP, focusing on their efficacy, mechanism of action, and therapeutic potential. Additionally, it evaluates ongoing clinical trials investigating novel drugs and therapeutic approaches, highlighting emerging trends and future directions in NP management.

AREAS COVERED

This review examines first- to third-line therapeutic modalities for NP, critically analyzing their efficacy, safety profiles, and clinical applications. It also includes an overview of ongoing clinical trials exploring innovative pharmacological therapies. A thorough literature review was conducted using the MEDLINE database without temporal limitations, offering a detailed assessment of established and emerging treatments.

EXPERT OPINION

While current pharmacological options offer significant symptom relief, their overall effectiveness in managing NP remains limited, highlighting the need for further therapeutic advancements. Staying informed about emerging therapies and clinical trials is vital to enhancing patient care and quality of life. The future of NP management lies in optimizing individualized treatment strategies, refining therapeutic approaches, and fostering interdisciplinary collaboration. Close monitoring of outcomes and continued research are essential for advancing understanding and improving the precision of NP therapies.

Discordance between preclinical and clinical testing of Na V 1.7-selective inhibitors for pain

ABSTRACT

The voltage-gated sodium channel Na V 1.7 plays an important role in pain processing according to genetic data. Those data made Na V 1.7 a popular drug target, especially since its relatively selective expression in nociceptors promised pain relief without the adverse effects associated with broader sodium channel blockade. Despite encouraging preclinical data in rodents, Na V 1.7-selective inhibitors have not yet proven effective in clinical trials. Discrepancies between preclinical and clinical results should raise alarms. We reviewed preclinical and clinical reports on the analgesic efficacy of Na V 1.7-selective inhibitors and found critical differences in several factors. Putting aside species differences, most preclinical studies tested young male rodents with limited genetic variability, inconsistent with the clinical population. Inflammatory pain was the most common preclinical chronic pain model whereas nearly all clinical trials focused on neuropathic pain despite some evidence suggesting Na V 1.7 channels are not essential for neuropathic pain. Preclinical studies almost exclusively measured evoked pain whereas most clinical trials assessed average pain intensity without distinguishing between evoked and spontaneous pain. Nearly all preclinical studies gave a single dose of drug unlike the repeat dosing used clinically, thus precluding preclinical data from demonstrating whether tolerance or other slow processes occur. In summary, preclinical testing of Na V 1.7-selective inhibitors aligned poorly with clinical testing. Beyond issues that have already garnered widespread attention in the pain literature, our results highlight the treatment regimen and choice of pain model as areas for improvement.

Prediction of Central Post-Stroke Pain by Quantitative Sensory Testing

OBJECTIVE

Among patients with acute stroke, we aimed to identify those who will later develop central post-stroke pain (CPSP) versus those who will not (non-pain sensory stroke [NPSS]) by assessing potential differences in somatosensory profile patterns and evaluating their potential as predictors of CPSP.

METHODS

In a prospective longitudinal study on 75 acute stroke patients with somatosensory symptoms, we performed quantitative somatosensory testing (QST) in the acute/subacute phase (within 10 days) and on follow-up visits for 12 months. Based on previous QST studies, we hypothesized that QST values of cold detection threshold (CDT) and dynamic mechanical allodynia (DMA) would differ between CPSP and NPSS patients before the onset of pain. Mann-Whitney U-tests and mixed analysis of variances with Bonferroni corrections were performed to compare z-normalized QST scores between both groups.

RESULTS

In total, 26 patients (34.7%) developed CPSP. In the acute phase, CPSP patients showed contralesional cold hypoesthesia compared to NPSS patients (p = 0.04), but no DMA differences. Additional exploratory analysis showed NPSS patients exhibit cold hyperalgesia on the contralesional side compared to the ipsilesional side, not seen in CPSP patients (p = 0.011). A gradient-boosting approach to predicting CPSP from QST patterns before pain onset had an overall accuracy of 84.6%, with a recall and precision of 75%. Notably, both in the acute and the chronic phase, approximately 80% of CPSP and NPSS patients showed bilateral QST abnormalities.

INTERPRETATION

Cold perception differences between CPSP and NPSS patients appear early post stroke before pain onset. Prediction of CPSP through QST patterns seems feasible. ANN NEUROL 2025;97:507-520.

Pain profiles and variability in temporal summation of pain and conditioned pain modulation in pain-free individuals and patients with low back pain, osteoarthritis, and fibromyalgia

BACKGROUND

Pain profiles (e.g. pro- and anti-nociceptive) can be developed using quantitative sensory testing (QST) but substantial variability exists. This study describes the variability in temporal summation of pain (TSP) and conditioned pain modulation (CPM) in chronic musculoskeletal pain patients, proposes cut-off values, and explores the association with clinical pain intensity.

METHODS

This is a secondary analysis in which TSP and CPM were assessed using cuff algometry in pain-free subjects (n = 69), and patients with chronic low back pain (cLBP, n = 267), osteoarthritis (n = 134), and fibromyalgia (n = 101). Using TSP and CPM from the pain-free subjects as a reference, four distinct pain profiles TSP (low/high) and CPM (low/high) were created, and differences in clinical pain between pain profiles were explored.

RESULTS

Individual data revealed large inter-person variability. High TSP and low CPM were found in fibromyalgia (p < 0.01) and osteoarthritis (p < 0.01) but not cLBP when compared to pain-free subjects. The proportion of patients classified into the distinct pain profiles was significantly different (p < 0.001) with the largest proportion in the high TSP and low CPM group in fibromyalgia (52.5%) and osteoarthritis (41.4%). Clinical pain was not significantly different comparing the pain profiles, and no significant correlations were observed between clinical pain and TSP or CPM.

CONCLUSION

These results demonstrated substantial inter-person variability in TSP and CPM in patients with different chronic pain conditions and pain-free subjects. The proportion of patients with a pro-nociceptive profile appears larger in fibromyalgia and osteoarthritis, but we found no association to clinical pain.

SIGNIFICANT STATEMENT

This analysis shows that there is variability when assessing TSP and CPM in both pain-free subjects and patients with chronic pain. A cut-off for determining when a person is pain-sensitive is proposed, and data based on this cut-off approach suggest that significantly more patients with osteoarthritis and fibromyalgia are pain-sensitive (i.e. higher TSP and lower CPM) compared to pain-free subjects. This analysis does not find an association between pain sensitivity and clinical pain.

Perineuromal hydrodissection for acute postamputation pain? An observational study in a time of war

INTRODUCTION

This exploratory study investigates the potential of perineuromal hydrodissection as an adjunct to opioid therapy for postamputation pain, specifically focusing on residual limb and phantom limb pain (PLP). Given the correlations between acute pain and the development of chronic pain, the primary aims were to estimate the effect size of early hydrodissection of scar tissue around residual limb neuroma(s) and to identify the best time frame for treatment.

METHODS

Seventy-four patients with war-related limb amputations and painful neuromas were included in this observational analysis. Thirty-eight Ukrainian patients with war-related limb amputation and a painful neuroma(s) who underwent hydrodissection and opioid therapy within 6 months of amputation were compared with 36 patients who received opioids alone. Co-primary outcome measures were median reduction from baseline in average residual limb and PLP at 12 weeks. The composite positive outcome was designated as a ≥2-point decrease or 30% reduction in average residual limb and PLP, satisfaction with treatment, and not requiring an increase in analgesics.

RESULTS

Hydrodissection as an add-on to opioids resulted in a greater reduction in average residual limb pain at 12 weeks (-2.00±1.00 vs -1.00±1.00; p<0.001) and earlier time periods, but PLP only through 4 weeks. At 12 weeks, Hospital Anxiety and Depression Scale anxiety (10.00±2.00 vs 11.00±1.00; p<0.001) but not depression score was lower in the hydrodissection group. Opioid use in the hydrodissection group significantly declined from 41.32±9.63 to 33.42±8.78 morphine equivalents per day (p=0.001) over the study, but not in the opioid-only group (p=0.20). Differences in 12-week satisfaction rates were not significant.

CONCLUSIONS

This exploratory study suggests perineuromal hydrodissection may improve residual limb pain and to a lesser degree phantom limb pain, particularly when implemented early in the course of postamputation pain. The study provides preliminary effect size estimates and identifies acute pain as a potential characteristic of patients who may respond more favorably to this intervention. Randomized controlled trials are needed to confirm these findings and control for the confounding variables identified.

Metabolomics in Pathogenic Pathways and Targeted Therapies for Diabetic Neuropathy: A Comprehensive Review

INTRODUCTION AND OBJECTIVE

This literature review aims to provide an overview of the progress in metabolomic assessment in animal and cell models and in humans with diabetic neuropathy (DN).

METHODS

Metabolomics has emerged as an important approach for investigating, identifying, and describing biomarkers related to DN. None has yet been validated for use in clinical practice.

RESULTS

DN induced significant alterations in energy metabolism and carbohydrates, lipids, amino acids, peptides, and proteins. Several treatments for DN, evaluated using metabolomics, were proved to have promising results.

CONCLUSIONS

The ideal metabolite or set of metabolites that could be used as biomarkers should identify patients with diabetes prone to develop DN or those prone to progress to severe forms of sensory loss, associated with risk of ulcerations and amputation. Another potential use of a metabolite might be as an indicator of treatment response in clinical trials using agents with potential disease-modifying properties.

The Evolving Landscape of Small Fiber Neuropathy

Small fiber neuropathy (SFN) belongs to a heterogeneous group of disorders in which thinly myelinated Aδ and unmyelinated C-fibers are primarily affected, leading to neuropathic pain and autonomic symptoms. SFN can be associated with systemic conditions such as diabetes, autoimmune diseases, exposure to drugs and toxins, and infection, with the list of associated diseases continuing to expand. Variants in the SCN9A, SCN10A, and SCN11A genes encoding Nav 1.7, Nav 1.8, and Nav 1.9 sodium channel subunits, as well as in the TRPA1 gene, have been found in SFN patients, expanding the spectrum of underlying conditions and enhancing our understanding of pathophysiological mechanisms. There is also growing interest in immune-mediated forms that could help identify potentially treatable subgroups. According to international criteria, diagnosis is established through clinical examination, the assessment of intraepidermal nerve fiber density, and/or quantitative sensory testing. Autonomic functional tests allow for a better characterization of dysautonomia in SFN, which can be subclinical. Other tests can support the diagnosis. Currently, the management of SFN prioritizes treating the underlying condition, if identified, within a multidisciplinary approach that combines symptomatic pain therapy, lifestyle changes, and biopsychological interventions. Emerging insights from the molecular characterization of SFN channelopathies hold promise for improving diagnosis, potentially leading to the discovery of new drugs and refining trial designs in the future. This article reviews the clinical presentation, diagnostic workup, and advancing knowledge of associated conditions and interventional management of SFN.

Evidence-Based Umbrella Review of Non-Invasive Neuromodulation in Chronic Neuropathic Pain

BACKGROUND AND OBJECTIVE

Non-invasive neuromodulation techniques (NIN), such as transcranial Direct Current Stimulation (tDCS) and repetitive Transcranial Magnetic Stimulation (rTMS), have been extensively researched for their potential to alleviate pain by reversing neuroplastic changes associated with neuropathic pain (NP), a prevalent and complex condition. However, treating NP remains challenging due to the numerous variables involved, such as different techniques, dosages and aetiologies. It is necessary to provide insights for clinicians and public healthcare managers to support clinical decision-making. This umbrella review aims to consolidate existing evidence on the effectiveness of various NIN in managing chronic NP.

DATABASES AND DATA TREATMENT

A systematic search was conducted in the PubMed/MEDLINE database, including meta-analyses of controlled trials comparing NIN techniques with sham interventions for NP treatment. The quality of included studies was assessed using the AMSTAR-2 tool and the GRADE system, with effect sizes adjusted to the standard mean difference (SMD).

RESULTS

The review included 22 meta-analyses comprising 8151 participants from 214 controlled trials. The most investigated NIN techniques were tDCS and rTMS, with primary targets being the motor cortex and dorsolateral prefrontal cortex. The findings suggest that excitatory protocols, particularly high-frequency rTMS and anodal tDCS, are effective in reducing pain intensity in individuals with NP. However, the overall quality of evidence was rated low, primarily due to heterogeneity among studies and small sample sizes.

CONCLUSION

NIN techniques show promise in managing NP, with potential benefits in pain reduction. However, further high-quality research is needed to establish optimal protocols and long-term effects.

SIGNIFICANCE STATEMENT

This paper consolidates the evidence regarding non-invasive neuromodulation for the treatment of neuropathic pain, including differentiating the most effective techniques based on the aetiology of pain, and provides clinicians with easy access to this critical information. It also highlights key aspects that require further research in the field of non-invasive neuromodulation and neuropathic pain.

Explorative sensory profile evaluation in central neuropathic pain following spinal cord injury

BACKGROUND

Sensory profiling in neuropathic pain using quantitative sensory testing (QST) has not been extended to central neuropathic pain due to spinal cord injury (SCI). This study aims to fill this gap by evaluating sensory profiles in patients with neuropathic SCI pain.

METHOD

We retrospectively analysed consecutive QST data from 62 patients with neuropathic spinal cord injury pain (SCIP), following the German Research Network on Neuropathic Pain protocol. The study included at-level and below-level SCIP due to a spinal cord lesion, and at-level SCIP following a cauda equina lesion. QST parameters were compared between diagnostic groups. QST profiles of below-level SCIP (central neuropathic pain) were manually assigned to sensory phenotypes based on literature and expert opinion.

RESULTS

No statistical difference in QST parameters between pain diagnoses was found. For central neuropathic pain (below-level SCIP), three phenotypes were descriptively observed: loss of function (59%), thermal and mechanical hyperalgesia combination (16%), and mechanical hyperalgesia (19%). The remaining 5% of patients did not fit a common pattern. There was no statistical difference in clinical and psychological variables between phenotypes. In a subgroup analysis, the loss of function phenotype weakly correlated with older age, longer time since injury, and longer pain duration.

CONCLUSIONS

Here, we capture sensory phenotypes of central neuropathic pain following SCI. The limited sample size, high rate of missing values, and the retrospective nature of the study mean that results should be seen as strictly exploratory. Further research should replicate these findings and explore the significance of phenotypes.

SIGNIFICANCE STATEMENT

The evaluation of sensory phenotypes by quantitative sensory testing in central neuropathic pain due to SCI adds a new perspective on sensory phenotypes in comparison to peripheral neuropathic pain. The described thermal and mechanical hyperalgesia combination might represent involvement of the spinothalamic tract. In addition, there was a trend towards older age and longer time since injury in patients with loss of function.

Photobiomodulation therapy in diabetes: Benefits for pain relief, quality of life, and wound healing

Globally, 537 million people suffer from diabetes mellitus (DM), a condition often associated with sensory disturbances, wound development, and chronic pain, which significantly affects the quality of life and imposes a substantial economic burden. This study evaluated the effects of photobiomodulation (PBM) therapy on nociceptive and sensory changes in diabetic patients to understand pain manifestations and explore PBM's molecular mechanisms on wound healing. Twenty patients with type 2 DM underwent clinical assessments, completed pain and quality of life questionnaires, and had their pain sensitivity evaluated using the quantitative sensory test (QST). A 5 mm skin biopsy was taken for fibroblast culture. PBM therapy, using 660 nm red light, was administered twice weekly for 7 weeks on lower limb wounds. Results indicated that DM patients faced significant sensory impairments, impacting their quality of life. PBM therapy improved pain scores, alleviated neuropathic pain, and enhanced sensory function, leading to better quality of life and reduced anxiety and depression. It also accelerated wound healing, enhancing mobility and autonomy. In vitro studies showed PBM therapy increased cell proliferation through the ERK signaling pathway and modulation of matrix metalloproteinases (MMP-1/8 and 2) and tissue inhibitors of metalloproteinases (TIMP).

Development and validation of a home quantitative sensory testing tool-kit to assess changes in sensory and pain processing: a study in healthy young adults

ABSTRACT

Quantitative sensory testing (QST) is a set of methods for quantifying somatosensory functioning. Limitations of laboratory-based QST (LQST) include high cost, complexity in training, lack of portability, and time requirements for testing. Translating QST to a home setting could facilitate future research and clinical care. The objective of this study was to develop a home QST (HQST) tool-kit that is cost-effective, easy to use, and detects changes in sensory and pain processing. Thirty-two young healthy adults underwent sensory testing on their nondominant forearm using standard in-person LQST, followed by "simulated HQST" using video guidance in a separate room from the investigator before and after application of either a lidocaine or capsaicin cream. We observed good agreement between HQST and LQST scores, with significant correlations observed between the pinprick, pressure, cold and heat measures (|ρ| range = 0.36-0.54). The participants rated the HQST protocol as highly acceptable and safe but can be improved in future implementations. Home QST was able to detect hypoesthesia to vibration after lidocaine cream application ( P = 0.024, d = 0.502) and could detect hypoalgesia and hyperalgesia to pressure and heat pain sensitivity tests after application of lidocaine and capsaicin creams, respectively ( P -value range = <0.001-0.036, d -value range = 0.563-0.901). Despite limitations, HQST tool-kits may become a cost-effective, convenient, and scalable approach for improving sensory profiling in clinical care and clinical research.

From breast cancer diagnosis to survivorship: Analyzing perioperative biopsychosocial phenotypes and their relationship to pain on long term

Persistent breast cancer treatment-related pain affects up to 40% of patients, decreasing their quality of life (QoL). While current research typically utilizes correlation and regression analysis to identify biopsychosocial phenotypes contributing to this pain, this study employs cluster analysis to identify qualitatively different phenotypes based on somatosensory and psychosocial characteristics both before and one week post-breast cancer surgery. Further, it investigates how these phenotypes are related to pain intensity one year post-surgery and examines the evolution of phenotype membership from pre- to post-surgery. Somatosensory and psychosocial functioning was evaluated pre- and post-surgery in 184 women undergoing unilateral breast cancer surgery. Eight different quantitative sensory testing (QST) methods including mechanical detection and pain thresholds, pressure pain thresholds, thermal detection and pain thresholds, and conditioned pain modulation were performed at the surgical area (trunk, arm, major pectoral muscle) and a distant location (quadriceps muscle). Psychosocial functioning was assessed using the Central Sensitization Inventory, Pain Catastrophizing Scale, Depression Anxiety Stress Scale-21, and the McGill Quality of Life Questionnaire. Pain intensity was evaluated one year post-breast cancer surgery using the Visual Analogue Scale. Latent class analysis identified five distinct phenotypes before and post-surgery, characterized by differences in mechanical and pain thresholds alongside psychosocial factors. Moreover, higher psychosocial distress and lower QoL correlated with elevated pain intensity one year post-surgery. These findings underscore the importance of addressing breast cancer patients' mental health perioperatively. Therefore, future research should explore whether psychological interventions perioperatively can reduce long-term pain intensity. PERSPECTIVE: This secondary analysis, utilizing cluster analysis, reveals five distinct phenotype based on somatosensory and psychosocial characteristics both before and post-breast cancer surgery. Higher psychosocial distress and lower quality of life correlated with elevated pain intensity one year post-surgery, emphasizing the need to address patients' mental health perioperatively. TRIAL REGISTRATION: clinicaltrials.gov (NCT03351075).

The relationship between changes in inflammation and locomotor function in sensory phenotypes of central neuropathic pain after spinal cord injury

Introduction

Central neuropathic pain (CNP) commonly develops in patients after spinal cord injury (SCI), causing debilitating symptoms and sensory abnormalities to mechanical and thermal stimuli. The biological variability of pain phenotypes in individuals has limited the number of positive outcomes. Thus, it is necessary to investigate the physiological processes contributing to sensory changes that develop over time.

Objective

To investigate the physiological processes contributing to neuropathic pain sensory changes and locomotor impairments with sensory phenotypes that develop over time.

Methods

Using the tail flick and von Frey tests, we performed hierarchical clustering to determine the subpopulation of rats that developed thermal and mechanical sensory abnormalities. To measure inflammation as a potential mediator of CNP phenotypes, we used flow cytometry and immunohistochemistry. Finally, to assess the secondary effects on locomotor recovery, up to 8 weeks after injury, we used the CatWalk test to assess multiple parameters of gait.

Results

The von Frey test showed a subpopulation of SCI rats that were hyposensitive to mechanical stimuli from 6 to 8 weeks after injury. The tail flick test showed a subpopulation of SCI rats that were hypersensitive to thermal stimuli at 1 week and 3 to 8 weeks after injury. Although there were no differences in inflammatory cells between subpopulations, we did see significant changes in locomotor recovery between rats with and without sensory abnormalities.

Conclusion

The myeloid cell population at large is not affected by mechanical or thermal phenotypes of pain in this model; however, locomotor recovery is impaired depending on the pain phenotype present. Further investigation into acute inflammatory cells may be insightful for predicting the development of pain phenotypes.

What is associated with painful polyneuropathy? A cross-sectional analysis of symptoms and signs in patients with painful and painless polyneuropathy

ABSTRACT

It is still unclear how and why some patients develop painful and others painless polyneuropathy. The aim of this study was to identify multiple factors associated with painful polyneuropathies (NeuP). A total of 1181 patients of the multicenter DOLORISK database with painful (probable or definite NeuP) or painless (unlikely NeuP) probable or confirmed neuropathy were investigated clinically, with questionnaires and quantitative sensory testing. Multivariate logistic regression including all variables (demographics, medical history, psychological symptoms, personality items, pain-related worrying, life-style factors, as well as results from clinical examination and quantitative sensory testing) and machine learning was used for the identification of predictors and final risk prediction of painful neuropathy. Multivariate logistic regression demonstrated that severity and idiopathic etiology of neuropathy, presence of chronic pain in family, Patient-Reported Outcomes Measurement Information System Fatigue and Depression T-Score, as well as Pain Catastrophizing Scale total score are the most important features associated with the presence of pain in neuropathy. Machine learning (random forest) identified the same variables. Multivariate logistic regression archived an accuracy above 78%, random forest of 76%; thus, almost 4 out of 5 subjects can be classified correctly. This multicenter analysis shows that pain-related worrying, emotional well-being, and clinical phenotype are factors associated with painful (vs painless) neuropathy. Results may help in the future to identify patients at risk of developing painful neuropathy and identify consequences of pain in longitudinal studies.

Phenotyping peripheral neuropathies with and without pruritus: a cross-sectional multicenter study

ABSTRACT

Pruritus often escapes physicians' attention in patients with peripheral neuropathy (PNP). Here we aimed to characterize neuropathic pruritus in a cohort of 191 patients with PNP (large, mixed, or small fiber) and 57 control subjects with deep phenotyping in a multicenter cross-sectional observational study at 3 German sites. All participants underwent thorough neurological examination, nerve conduction studies, quantitative sensory testing, and skin biopsies to assess intraepidermal nerve fiber density. Patients filled in a set of questionnaires assessing the characteristics of pruritus and pain, the presence of depression and anxiety, and quality of life. Based on the severity of pruritus and pain, patients were grouped into 4 groups: "pruritus," "pain," "pruritus and pain," and "no pruritus/no pain." Although 11% (21/191) of patients reported pruritus as their only symptom, further 34.6% (66/191) reported pruritus and pain. Patients with pain (with or without pruritus) were more affected by anxiety, depression, and reduced quality of life than control subjects. Patients with pruritus (with and without pain) had increases in cold detection threshold, showing Aδ-fiber dysfunction. The pruritus group had lower intraepidermal nerve fiber density at the thigh, concomitant with a more proximal distribution of symptoms compared with the other PNP groups. Stratification of patients with PNP by using cross-sectional datasets and multinominal logistic regression analysis revealed distinct patterns for the patient groups. Together, our study sheds light on the presence of neuropathic pruritus in patients with PNP and its relationship with neuropathic pain, outlines the sensory and structural abnormalities associated with neuropathic pruritus, and highlights its impact on anxiety levels.

A Meta-analysis Exploring the Efficacy of Neuropathic Pain Medication for Low Back Pain or Spine-Related Leg Pain: Is Efficacy Dependent on the Presence of Neuropathic Pain?

BACKGROUND AND OBJECTIVE

Highly variable pain mechanisms in people with low back pain or spine-related leg pain might contribute to inefficacy of neuropathic pain medication. This meta-analysis aimed to determine how neuropathic pain is identified in clinical trials for people taking neuropathic pain medication for low back pain or spine-related leg pain and whether subgrouping based on the presence of neuropathic pain influences efficacy.

METHODS

EMBASE, MEDLINE, Cochrane Central, CINAHL [EBSCO], APA PsycINFO, ClinicalTrials.gov, and the World Health Organization International Clinical Trials Registry were searched from inception to 14 May, 2024. Randomized and crossover trials comparing first-line neuropathic pain medication for people with low back pain or spine-related leg pain to placebo or usual care were included. Two independent authors extracted data. Random-effects meta-analyses of all studies combined, and pre-planned subgroup meta-analyses based on the certainty of neuropathic pain (according to the neuropathic pain Special Interest Group [NeuPSIG] neuropathic pain grading criteria) were completed. Certainty of evidence was judged using the grading of recommendations assessment development and evaluation [GRADE] framework.

RESULTS

Twenty-seven included studies reported on 3619 participants. Overall, 33% of studies were judged unlikely to include people with neuropathic pain, 26% remained unclear. Only 41% identified people with possible, probable, or definite neuropathic pain. For pain, general analyses revealed only small effects at short term (mean difference [MD] - 9.30 [95% confidence interval [CI] - 13.71, - 4.88], I2 = 87%) and medium term (MD - 5.49 [95% CI - 7.24, - 3.74], I2 = 0%). Subgrouping at short term revealed studies including people with definite or probable neuropathic pain showed larger effects on pain (definite; MD - 16.65 [95% CI - 35.95, 2.65], I2 = 84%; probable; MD - 10.45 [95% CI - 14.79, - 6.12], I2 = 20%) than studies including people with possible (MD - 5.50 [95% CI - 20.52, 9.52], I2 = 78%), unlikely (MD - 6.67 [95% CI - 10.58, 2.76], I2 = 0%), or unclear neuropathic pain (MD - 8.93 [95% CI - 20.57, 2.71], I2 = 96%). Similarly, general analyses revealed negligible effects on disability at short term (MD - 3.35 [95% CI - 9.00, 2.29], I2 = 93%) and medium term (MD - 4.06 [95% CI - 5.63, - 2.48], I2 = 0%). Sub-grouping at short term revealed larger effects in studies including people with definite/probable neuropathic pain (MD - 9.25 [95% CI - 12.59, - 5.90], I2 = 2%) compared with those with possible/unclear/unlikely neuropathic pain (MD -1.57 [95% CI - 8.96, 5.82] I2 = 95%). Medium-term outcomes showed a similar trend, but were limited by low numbers of studies. Certainty of evidence was low to very low for all outcomes.

CONCLUSIONS

Most studies using neuropathic pain medication for low back pain or spine-related leg pain fail to adequately consider the presence of neuropathic pain. Meta-analyses suggest neuropathic pain medication may be most effective in people with low back pain or spine-related leg pain with a definite/probable neuropathic pain component. However, the low to very low certainty of evidence and poor identification of neuropathic pain in most studies prevent firm recommendations.

Is there a role for capsaicin in cancer pain management?

PURPOSE OF REVIEW

Advances in oncological therapies have resulted in an increase in the number of patients living with and beyond cancer. The personal and societal impact of chronic pain in the survivor population represents an area of significant unmet need. Capsaicin (a TRPV1 agonist) may provide analgesia with limited systemic side effects. This review looks to summarise the most recent evidence regarding the use of capsaicin in the management of cancer pain.

RECENT FINDINGS

Various international guidelines have recently endorsed the use of high concentration capsaicin patches in the treatment of chronic painful chemotherapy induced peripheral neuropathy. Numerous studies support the use of capsaicin in the treatment of peripheral neuropathic pain. This promising data is predominantly yielded from pain secondary to herpes zoster and diabetic neuropathy, with an expanding but small evidence base for its utility in other neuropathic pains. Emerging data suggests that treatments are better tolerated and provide analgesia more rapidly when compared with systemic treatments.

SUMMARY

Whilst randomised controlled trial data in the treatment of cancer pain are lacking, recent large cohort studies, and international guidelines, support the use of high concentration capsaicin patches in a wide variety of neuropathic pain secondary to cancer treatments.

Clinical pharmacology of neuropathic pain

This chapter aims to review the current pharmacological options for neuropathic pain treatment, their mechanisms of action, and future directions for clinical practice. Achieving pain relief in neuropathic pain conditions remains a challenge in clinical practice. The field of pharmacotherapy for neuropathic pain has encountered significant difficulties in translating substantial advances in our understanding of the underlying pathophysiological mechanisms into clinically effective therapies. This chapter presents the drugs recommended for the pharmacotherapy of neuropathic pain, based on the widely accepted treatment guidelines formulated by the Neuropathic Pain Special Interest Group of the International Association for the Study of Pain. In addition to discussing how the evidence base is created as part of international consortia, the drugs are also examined in terms of their putative molecular mechanisms as well as pharmacological pleiotropy, i.e., their potential unspecific and multi-target effects resulting in modulation of neuronal hyperexcitability. The chapter closes with a discussion of potential future developments in the field.

A Systematic Review and Meta-Analysis of Conditioned Pain Modulation in Children and Young People with Chronic Pain

BACKGROUND/OBJECTIVES

Conditioned pain modulation (CPM) is a psychophysical experimental measure of the endogenous pain inhibitory pathway in humans, wherein one pain stimulus (the conditioning stimulus) is used to inhibit an individual's perception of a second painful (test) stimulus. Research provides evidence of impaired endogenous inhibitory pain responses in adults with chronic pain. CPM is now increasingly applied in paediatric research and clinical practice. The primary aim of this systematic review was to examine the efficacy of CPM in paediatric chronic pain populations (6-24-year-olds) compared to pain-free children and young people (CYP).

METHODS

The protocol was registered on PROSPERO (CRD42020221927). A systematic search of seven databases was conducted from database inception to 20th June 2024. Study inclusion criteria were as follows: (i) recruited a sample of CYP aged 6 to 24 (inclusive) with chronic pain or who were pain-free; and (ii) applied a CPM paradigm comprising both a painful test and conditioning stimuli that were sufficiently detailed to allow for replication,(iii) adhered to a study design of randomised control trial, case control or cohort study, including cross-sectional or longitudinal; (iv) available in the English language. Study exclusion criteria were: (i) The CPM paradigm used a non-painful test or conditioning stimulus only; and (ii) was only available as an abstract, letter, poster, editorial, case report, or review with or without meta-analyses. Risk of bias was assessed using the Appraisal Tool for Cross Sectional Studies (AXIS). Meta-analyses were conducted in Comprehensive Meta Analysis 3.0 using random effects models to compare the overall CPM responses in CYP with chronic pain conditions to healthy control CYP.

RESULTS

Thirty-two studies were eligible for inclusion, six of which were included in one or more meta-analysis (n = 407 chronic pain, n = 205 control). Meta-analysis revealed significantly weaker CPM responses in CYP with a variety of chronic pain conditions compared to healthy controls (standardized mean difference (SMD) = 0.352), and significantly weaker CPM responses in CYP with abdominal pain conditions compared to healthy controls (SMD = 0.685). No significant difference in CPM response was found between CYP with migraine and healthy controls (SMD = -0.201).

CONCLUSIONS

Variable results were found across individual studies, and the meta-analysis of the small number of eligible studies provides tentative evidence for impaired CPM in CYP with chronic pain compared to healthy controls. Further research is clearly needed. In particular, studies should present CPM results separately for different age groups, ethnic groups, and sexes, as these variables shape clinical pain responses.

Quantitative Sensory Testing - From bench to bedside

The methodology of Quantitative Sensory Testing (QST) comprises standardized testing procedures, which provide information of the integrity of the somatosensory nervous system. Over the years, different protocols have been established, which utilize similar but distinct testing procedures. They pursue the same overall objective to identify loss or gain of function of the respective sensory parameter to better understand the degree of abnormal nervous function and thereby improve patient care in the long-term. Laboratory-based QST protocols, which apply highly standardized testing procedures in pre-defined order and body regions, are considered as the gold standard in sensory testing. However, those protocols often require specifically trained personal, high equipment investment, and are time consuming. Thus, in recent years several attempts have been made to simplify testing protocols as well as reduce high costs of testing equipment such as thermal probe systems. These attempts have culminated in an array of sensory bedside testing protocols subserving the need for protocols that are easy to implement in and provide a standardized assessment within clinical trials. While laboratory and bedside QST that focus on static responses of single stimuli, protocols for testing dynamic QST focus on the functional response to pain also exist. Conditioned pain modulation (CPM) is often applied, which offers the ability to study endogenous inhibition of pain. All of these mentioned methodologies are considered as psychophysical measures and thus rely heavily on the cooperation of the patient or participant. In this chapter we provide an overview of QST along three main lines: (i) laboratory QST, (ii) bedside QST and (iii) dynamic QST. In addition, we discuss advantages and pitfalls of each modality. While we discuss along these lines, it should be noted that methodologies are overlapping: some bedside tests are similar or identical to lab-QST, many lab-QST protocols include a dynamic component, and assessment of dynamic QST requires to start with static assessments.

Topically applied novel TRPV1 receptor antagonist, ACD440 Gel, reduces evoked pain in healthy volunteers, a randomized, double-blind, placebo-controlled, crossover study

BACKGROUND

The TRPV1 receptor is a key molecule in pain generation. Previous development of oral TRPV1-antagonists was halted due to systemic heat insensitivity and body temperature alterations. The present Phase 1b study investigated the efficacy, safety and plasma exposure of a topically administered TRPV1-antagonist (ACD440 Gel) in healthy subjects.

METHODS

The study comprised two parts. In part 1, 24 healthy subjects were included in this randomized double-blind, placebo-controlled, crossover trial. ACD440 Gel or Placebo was applied once daily and wiped off after 1 h, for 5 consecutive days. Assessments were done in normal skin, skin optimized for penetration (by stripping and occlusive gel application) and UVB-irradiated skin. Pain induced by thermo-nociceptive CO2 laser impulses generated laser-evoked potentials (LEPs), with readouts of peak-to-peak (PtP) amplitude in vertex-EEG and pain assessments by VAS (0-100). Endpoints include effects at 1 hour post-dose, AUC(Days 1-5) and AUC(0-24, Day 4). In UVB-irradiated skin, also pain on pinprick and skin redness were assessed. Part 2 explored the plasma pharmacokinetics of ACD440.

RESULTS

ACD440 Gel reduced LEP PtP amplitude and VAS pain, p < 0.001, in all skin conditions, versus placebo. In UVB-irradiated skin, pinprick pain was also reduced, p = 0.047. Effects were significant after 1 h, maintaining for at least 9 h. There were no adverse events or drug-induced erythema. Plasma exposures of ACD440 were too low to establish an elimination half-life of ACD400.

CONCLUSIONS

Topical ACD440 Gel demonstrated a significant analgesic effect on LEP, VAS score and pinprick pain, with low systemic exposures, supporting further clinical development.

SIGNIFICANCE

This study demonstrates that the topical administration of a TRPV1-antagonist, ACD440 Gel, has potential as a new treatment for painful conditions affecting the skin, such as chronic peripheral neuropathic pain, without any local or systemic side effects.

Improving neuropathic pain treatment - by rigorous stratification from bench to bedside

Chronic pain is a constantly recurring and persistent illness, presenting a formidable healthcare challenge for patients and physicians alike. Current first-line analgesics offer only low-modest efficacy when averaged across populations, further contributing to this debilitating disease burden. Moreover, many recent trials for novel analgesics have not met primary efficacy endpoints, which is particularly striking considering the pharmacological advances have provided a range of highly relevant new drug targets. Heterogeneity within chronic pain cohorts is increasingly understood to play a critical role in these failures of treatment and drug discovery, with some patients deriving substantial benefits from a given intervention while it has little-to-no effect on others. As such, current treatment failures may not result from a true lack of efficacy, but rather a failure to target individuals whose pain is driven by mechanisms which it therapeutically modulates. This necessitates a move towards phenotypical stratification of patients to delineate responders and non-responders in a mechanistically driven manner. In this article, we outline a bench-to-bedside roadmap for this transition to mechanistically informed personalised pain medicine. We emphasise how the successful identification of novel analgesics is dependent on rigorous experimental design as well as the validity of models and translatability of outcome measures between the animal model and patients. Subsequently, we discuss general and specific aspects of human trial design to address heterogeneity in patient populations to increase the chance of identifying effective analgesics. Finally, we show how stratification approaches can be brought into clinical routine to the benefit of patients.

Genetic associations of neuropathic pain and sensory profile in a deeply phenotyped neuropathy cohort

ABSTRACT

We aimed to investigate the genetic associations of neuropathic pain in a deeply phenotyped cohort. Participants with neuropathic pain were cases and compared with those exposed to injury or disease but without neuropathic pain as control subjects. Diabetic polyneuropathy was the most common aetiology of neuropathic pain. A standardised quantitative sensory testing protocol was used to categorize participants based on sensory profile. We performed genome-wide association study, and in a subset of participants, we undertook whole-exome sequencing targeting analyses of 45 known pain-related genes. In the genome-wide association study of diabetic neuropathy (N = 1541), a top significant association was found at the KCNT2 locus linked with pain intensity (rs114159097, P = 3.55 × 10-8). Gene-based analysis revealed significant associations between LHX8 and TCF7L2 and neuropathic pain. Polygenic risk score for depression was associated with neuropathic pain in all participants. Polygenic risk score for C-reactive protein showed a positive association, while that for fasting insulin showed a negative association with neuropathic pain, in individuals with diabetic polyneuropathy. Gene burden analysis of candidate pain genes supported significant associations between rare variants in SCN9A and OPRM1 and neuropathic pain. Comparison of individuals with the "irritable" nociceptor profile to those with a "nonirritable" nociceptor profile identified a significantly associated variant (rs72669682, P = 4.39 × 10-8) within the ANK2 gene. Our study on a deeply phenotyped cohort with neuropathic pain has confirmed genetic associations with the known pain-related genes KCNT2, OPRM1, and SCN9A and identified novel associations with LHX8 and ANK2, genes not previously linked to pain and sensory profiles, respectively.

8. Herpes zoster and post herpetic neuralgia

INTRODUCTION

Patients suffering from postherpetic neuralgia (PHN) report unilateral chronic pain in one or more dermatomes after an acute herpes zoster (HZ) infection. The incidence of acute HZ ranges between three and five patients per 1000 person-years. In one out of four patients, acute HZ-related pain will transition into PHN. PHN can be very disabling for patients and reduce quality of life. Additionally, the treatment of PHN is characterized by high failure rates. The aim of this review is to give an update on the previous practical guideline published in 2011 and revised in 2015 (published in 2019) and to provide an overview of current interventional treatment options for HZ infection and PHN.

METHODS

The literature on the diagnosis and treatment of HZ and PHN was systematically reviewed and summarized.

RESULTS

The most important treatment for acute HZ-related pain is antiviral therapy within 72 h of symptom onset. Additional symptomatic treatment options are analgesic drugs according to the WHO pain ladder, tricyclic antidepressants (eg, nortriptyline), and antiepileptic drugs (eg, gabapentin). If pain is not sufficiently reduced, interventional treatment such as an epidural injection with local anesthetics and corticosteroids or pulsed radiofrequency of the dorsal root ganglion (DRG) are options. Treatment for PHN is preferably transdermal capsaicin, lidocaine, or oral drugs such as antidepressants or antiepileptics.

CONCLUSIONS

Treatment of acute HZ-related pain especially PHN is challenging. Besides the conventional treatment for PHN, interventional management is considered a new treatment option. PRF of DRG seems to be the most promising interventional management.

Diabetic Peripheral Neuropathy: Emerging Treatments of Neuropathic Pain and Novel Diagnostic Methods

BACKGROUND

Diabetic peripheral neuropathy (DPN) is a prevalent and debilitating complication of diabetes, often leading to severe neuropathic pain. Although other diabetes-related complications have witnessed a surge of emerging treatments in recent years, DPN has seen minimal progression. This stagnation stems from various factors, including insensitive diagnostic methods and inadequate treatment options for neuropathic pain.

METHODS

In this comprehensive review, we highlight promising novel diagnostic techniques for assessing DPN, elucidating their development, strengths, and limitations, and assessing their potential as future reliable clinical biomarkers and endpoints. In addition, we delve into the most promising emerging pharmacological and mechanistic treatments for managing neuropathic pain, an area currently characterized by inadequate pain relief and a notable burden of side effects.

RESULTS

Skin biopsies, corneal confocal microscopy, transcutaneous electrical stimulation, blood-derived biomarkers, and multi-omics emerge as some of the most promising new techniques, while low-dose naltrexone, selective sodium-channel blockers, calcitonin gene-related peptide antibodies, and angiotensin type 2 receptor antagonists emerge as some of the most promising new drug candidates.

CONCLUSION

Our review concludes that although several promising diagnostic modalities and emerging treatments exist, an ongoing need persists for the further development of sensitive diagnostic tools and mechanism-based, personalized treatment approaches.

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

OBJECTIVE

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

DESIGN

Cross-sectional study.

SETTING

Community-dwelling cohort.

PARTICIPANTS

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

RESULTS

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

CONCLUSION

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

Radiofrequency stimulation of the dorsal root ganglion as a diagnostic tool for radicular pain syndromes: six representative cases

BACKGROUND

We discuss the diagnostic benefit of pulsed radiofrequency (PRF) of the dorsal root ganglion (DRG) in a case series of patients with different pathologies. We expand the diagnostic potential of DRG stimulation beyond paresthesia mapping by using DRG stimulation to help determine the role of the DRG in the patient's pain and narrow down the etiology. In some cases, DRG stimulation was also part of the treatment plan.

METHODS

Six patients underwent DRG radiofrequency as a diagnostic/therapeutic step before considering implantation of a DRG neurostimulator. First, patients underwent a basic bedside neurological evaluation. Next, an electrode was placed in the epidural space through the sacral hiatus or between vertebral laminae. Then, sensory stimulation was applied at 50 Hz and gradually increased from 0.1 V until the patient reported paresthesia or until a maximum intensity of 2 V was reached. Patients were asked to describe where the stimulation was felt and outline the anatomical area the paresthesia covered. Then a motor stimulation was applied at 2 Hz until muscle twitching was reported by the patient or observed by the physician.

RESULTS

The information obtained helped diagnose the type of lesion as principally preganglionic, ganglionic, or postganglionic. This information guided patient management.

CONCLUSION

PRF of the DRG can provide valuable diagnostic information and is a useful step before ganglionic electrode implantation. In all cases, PRF of the DRG provided valuable diagnostic information and guided management options.

Reliability of a clinical sensory test battery in patients with spine-related leg and arm pain

BACKGROUND

The current standard to evaluate the presence of somatosensory dysfunctions is quantitative sensory testing, but its clinical utility remains limited. Low-cost and time-efficient clinical sensory testing (CST) batteries have thus been developed. Recent studies show moderate to substantial reliability in populations with neuropathic pain. This study evaluates the inter- and intra-tester reliability of people with spine-related leg and arm pain, representing mixed pain mechanisms.

METHODS

Fifty-three patients with spine-related leg (n = 41) and arm pain (n = 12) attended three CST sessions. The CST battery consisted of eleven tests, determining loss and gain of sensory nerve function. CST was performed by the same investigator twice and by an additional investigator to determine inter- and intra-tester reliability. Fleiss' (inter-tester) and Cohen's (intra-tester) kappa were calculated for dichotomized and intraclass correlation coefficients (ICC) for continuous outcomes.

RESULTS

Fleiss' kappa varied among modalities from fair to substantial (κ = 0.23-0.66). Cold, warm, and vibration detection thresholds and cold and pressure pain thresholds reached kappa >0.4 (moderate to substantial reliability). Cohen's kappa ranged from moderate to substantial (κ = 0.45-0.66). The reliability of the windup ratio was poor (ICC <0.18).

CONCLUSION

CST modalities with moderate to substantial inter-tester reliability could be of benefit as a screening tool. The moderate to substantial intra-tester reliability for all sensory modalities (except windup ratio) supports their potential use in clinical practice and research to monitor somatosensory changes over time in patients with spine-related limb pain of mixed pain mechanisms.

SIGNIFICANCE

We already know that most modalities of clinical sensory test (CST) batteries achieve moderate to substantial inter- and intra-tester reliability in populations with neuropathic pain. This study evaluates the reliability of a CST battery in populations with mixed pain mechanisms. We found inter-tester reliability varied from poor to substantial for sensory modalities, questioning the value of some CST modalities. The CST battery showed moderate to substantial intra-tester reliability, suggesting its usefulness to monitor sensory changes over time in this cohort.

Small fibre neuropathy frequently underlies the painful long-COVID syndrome

ABSTRACT

Approximately 10% to 20% of individuals with previous SARS-CoV-2 infection may develop long-COVID syndrome, characterized by various physical and mental health issues, including pain. Previous studies suggested an association between small fibre neuropathy and pain in long-COVID cases. In this case-control study, our aim was to identify small fibre neuropathy in patients experiencing painful long-COVID syndrome. Clinical data, quantitative sensory testing, and skin biopsies were collected from 26 selected patients with painful long-COVID syndrome. We also examined 100 individuals with past COVID-19 infection, selecting 33 patients with painless long-COVID syndrome, characterized mainly by symptoms such as brain fog and fatigue, and 30 asymptomatic post-COVID-19 controls. Demographic and clinical variables were compared among these groups. Among the 26 patients with painful long-COVID syndrome, 12 had skin biopsy and/or quantitative sensory testing abnormalities compatible with small fibre neuropathy. Demographic and clinical data did not differ across patients with small fibre neuropathy, patients with painless long-COVID syndrome, and asymptomatic post-COVID-19 controls. This case-control study showed that approximately 50% of patients experiencing painful long-COVID syndrome had small fibre neuropathy. However, in our patient cohort, this specific post-COVID-19 complication was unrelated to demographic and COVID-19 clinical variables. Approximately half of our sample of patients with painful long-COVID symptoms met diagnostic criteria for small fibre neuropathy.

Characterization of the neuropathic pain component contributing to myalgia in patients with myotonic dystrophy type 1 and 2

Introduction

Chronic muscle pain is common in myotonic dystrophies (DM). Little is known about its pathophysiology. We aimed to investigate the characteristics of the neuropathic pain component contributing contributes to the pathogenesis of chronic pain in DM.

Methods

Twenty-one DM1 and 32 DM2 patients completed pain questionnaires (Brief pain inventory-BPI, PAIN-DETECT, pain disability index-PDI) and underwent neurological examination, nerve conduction studies (NCS), quantitative sensory testing (QST, dorsum of the right hand and right thigh) and skin biopsy to determine the intraepidermal nerve fiber density (IENFD, distal and proximal site of lower extremity). NCS and QST results at the thigh were compared to 27 healthy controls and IENFD and QST at the dorsum of the hand to published reference values.

Results

The sensory profile of DM2 patients was characterized by a loss in thermal and mechanical detection, while DM1 patients showed reduced mechanical and heat pain thresholds and higher mechanical pain sensitivity. Both DM groups showed pressure hyperalgesia. IENFD was reduced in 63% of DM1 patients and 50% of DM2. The slightly higher pain interference and disability found in DM2 was rather due to age difference than disease.

Conclusion

Similar pain mechanisms likely occur in both DM1 and DM2, even though a tendency toward more pain sensitivity was observed in DM1 and more sensory loss in DM2. Both QST and reduced IENFD highlight the presence of peripheral nerve damage in DM. This must be considered for the best pain management strategies.

Impact of streptozotocin-induced diabetes on experimental masseter pain in rats

This study aimed to assess the influence of streptozotocin (STZ)-induced diabetes on the nociceptive behavior evoked by the injection of hypertonic saline (HS) into the masseter muscle of rats. Forty male rats were equally divided into four groups: a) isotonic saline control, which received 0.9% isotonic saline (IS), (Ctrl-IS); b) hypertonic saline control, which received 5% HS (Ctrl-HS); c) STZ-induced diabetic, which received IS, (STZ-IS); d) STZ-induced diabetic, which received HS (STZ-HS). Experimental diabetes was induced by a single intraperitoneal injection of STZ at dose of 60 mg/kg dissolved in 0.1 M citrate buffer, and 100 μL of HS or IS were injected into the left masseter to measure the nociceptive behavior. Later on, muscle RNA was extracted to measure the relative expression of the following cytokines: cyclooxygenase-2 (COX-2), tumor necrosis factor (TNF-α), and interleukins (IL)-1β, -2, -6, and -10. One-way analysis of variance (ANOVA) was applied to the data (p < 0.050). We observed a main effect of group on the nociceptive response (ANOVA: F = 11.60, p < 0.001), where the Ctrl-HS group presented the highest response (p < 0.001). However, nociceptive response was similar among the Ctrl-IS, STZ-IS, and STZ-HS group (p > 0.050). In addition, the highest relative gene expression of TNF-α and IL-6 was found in the masseter of control rats following experimental muscle pain (p < 0.050). In conclusion, the loss of somatosensory function can be observed in deep orofacial tissues of STZ-induced diabetic rats.

Referred pain is associated with greater odontogenic spontaneous pain and a heightened pain sensitivity in patients with symptomatic irreversible pulpitis

BACKGROUND

Symptomatic irreversible pulpitis often results in heightened reactions to thermal stimuli such as pain evoked by a cold stimulus, and spontaneous odontogenic pain (unprovoked pain).

OBJECTIVE

This study primarily compared the clinical manifestations of odontogenic spontaneous pain and pain provoked by cold stimulus specifically focusing on their sensory discriminative characteristics (intensity, duration and quality) between symptomatic irreversible pulpitis patients with and without referred pain.

METHODS

Twenty-three patients with symptomatic irreversible pulpitis with referred pain and 12 patients without referred pain were included in this cross-sectional study. The following outcomes were assessed: odontogenic spontaneous pain and its descriptors; pain evoked by cold stimulus and qualitative sensory testing before and after local anaesthesia; referred pain location; use of analgesic medication; complementary anaesthesia efficacy. T-test, chi-squared and McNemar tests were applied to the data (p < .50).

RESULTS

Patients with referred pain presented a greater odontogenic pain intensity (p < .05) when considered the average of the last 24 h. These patients also showed higher pain rating and pain descriptors (p < .05). Intensity and duration of the pain evoked by cold stimulus in the non-affected contralateral tooth at baseline were higher for patients with referred pain (p < .05).

CONCLUSION

Symptomatic irreversible pulpitis patients with referred pain present greater odontogenic spontaneous pain and a heightened pain sensitivity. Therefore, patients with referred pain seem more complex from a pain severity perspective, supporting the clinical utility of discriminating symptomatic irreversible pulpitis with and without referred pain.

Quantitative Sensory Testing in Spinal Cord Stimulation: A Narrative Review

OBJECTIVES

Quantitative sensory testing (QST) has been used for decades to study sensory abnormalities in multiple conditions in which the somatosensory system is compromised, including pain. It is commonly used in pharmacologic studies on chronic pain but less so in conjunction with neuromodulation. This review aims to assess the utility of QST in spinal cord stimulation (SCS) protocols.

MATERIALS AND METHODS

For this narrative review, we searched PubMed for records of studies in which sensory testing has been performed as part of a clinical study on SCS from 1975 onward until October 2023. We focused on studies in which QST has been used to explore the effect of SCS on neuropathic, neuropathic-like, or mixed pain.

RESULTS

Our search identified 22 useful studies, all small and exploratory, using heterogeneous methods. Four studies used the full battery of validated German Research Network on Neuropathic Pain QST. There is emerging evidence that assessment dynamic mechanical allodynia (eight studies), and mechanical/thermal temporal summation of pain (eight studies) may have a role in quantifying the response to various SCS waveforms. There also were sporadic reports of improvement of sensory deficits in a proportion of patients with neuropathic pain that warrant further study.

CONCLUSIONS

We recommend the adoption of QST into future clinical research protocols, using either the full QST protocol or a less time-demanding short-form QST.

Visual psychosocial profiling of Chinese temporomandibular disorder pain patients and correlations with somatosensory function

BACKGROUND

Psychosocial function of Chinese temporomandibular disorders (TMD) pain patients and the correlation with somatosensory function has not been sufficiently studied.

OBJECTIVE

The study aims at assessing the psychosocial function of Chinese TMD pain patients by visualisation method and evaluating the correlations with somatosensory function quantitatively.

METHODS

The Symptom Checklist 90 (SCL-90) questionnaire and standardised quantitative sensory testing (QST) were administered to 70 Chinese TMD pain patients and age- and gender-matched healthy controls (HCs). Of these, 40 TMD arthralgia patients received QST before and after medication. Psychosocial and somatosensory parameters were transformed into standardised scores. Differences within groups were assessed through t tests. Correlations between psychosocial and somatosensory profiles were explored through correlation analyses with Bonferroni correction for multiple comparisons.

RESULTS

100% of the Chinese TMD pain patients exhibited psychosocial distress in contrast to HCs. Anger and hostility showed negative correlation with the thermal nonnociceptive parameter (thermal sensory limen, p =.002) and nociceptive parameters (cold pain threshold and pain pressure threshold, p<.001). Correlation analysis indicated that cold detection threshold was negatively correlated with somatization and mechanical pain sensitivity had a negative correlation with anger and hostility through medical treatment (p <.001).

CONCLUSIONS

Visual psychosocial profiles provided an easy overview of psychosocial function in Chinese TMD pain patients. Anger and hostility was associated with increased thermal nonnociceptive and nociceptive sensitivity to stimuli. Psychosocial distress might be negatively associated with TMD treatment response which indicated a possible need for psychological intervention during treatment.

Mechanisms of neurodynamic treatments (MONET): a protocol for a mechanistic, randomised, single-blind controlled trial in patients with carpal tunnel syndrome

BACKGROUND

Physiotherapeutic management is the first-line intervention for patients with entrapment neuropathies such as carpal tunnel syndrome (CTS). As part of physiotherapy, neurodynamic interventions are often used to treat people with peripheral nerve involvement, but their mechanisms of action are yet to be fully understood. The MONET (mechanisms of neurodynamic treatment) study aims to investigate the mechanisms of action of neurodynamic exercise intervention on nerve structure, and function.

METHODS

This mechanistic, randomised, single-blind, controlled trial will include 78 people with electrodiagnostically confirmed mild or moderate CTS and 30 healthy participants (N = 108). Patients will be randomly assigned into (1) a 6-week progressive home-based neurodynamic exercise intervention (n = 26), (2) a steroid injection (= 26), or (3) advice (n = 26) group. The primary outcome measure is fractional anisotropy of the median nerve at the wrist using advanced magnetic resonance neuroimaging. Secondary outcome measures include neuroimaging markers at the wrist, quantitative sensory testing, electrodiagnostics, and patient reported outcome measures. Exploratory outcomes include neuroimaging markers at the cervical spine, inflammatory and axonal integrity markers in serial blood samples and biopsies of median nerve innervated skin. We will evaluate outcome measures at baseline and at the end of the 6-week intervention period. We will repeat questionnaires at 6-months. Two-way repeated measures ANCOVAs, followed by posthoc testing will be performed to identify differences in outcome measures among groups and over time.

DISCUSSION

This study will advance our understanding of the mechanisms of action underpinning neurodynamic exercises, which will ultimately help clinicians to better target these treatments to those patients who may benefit from them. The inclusion of a positive control group (steroid injection) and a negative control group (advice) will strengthen the interpretation of our results.

TRIAL REGISTRATION

NCT05859412, 20/4/2023.

Eleven neurology-related proteins measured in serum are positively correlated to the severity of diabetic neuropathy

About 20% of patients with diabetes suffer from chronic pain with neuropathic characteristics. We investigated the multivariate associations between 92 neurology-related proteins measured in serum from 190 patients with painful and painless diabetic neuropathy. Participants were recruited from the Pain in Neuropathy Study, an observational cross-sectional multicentre study in which participants underwent deep phenotyping. In the exploration cohort, two groups were defined by hierarchical cluster analyses of protein data. The proportion of painless vs painful neuropathy did not differ between the two groups, but one group had a significantly higher grade of neuropathy as measured by the Toronto Clinical Scoring System (TCSS). This finding was replicated in the replication cohort. Analyzing both groups together, we found that a group of 11 inter-correlated proteins (TNFRSF12A, SCARB2, N2DL-2, SKR3, EFNA4, LAYN, CLM-1, CD38, UNC5C, GFR-alpha-1, and JAM-B) were positively associated with TCSS values. Notably, EFNA4 and UNC5C are known to be part of axon guidance pathways. To conclude, although cluster analysis of 92 neurology-related proteins did not distinguish painful from painless diabetic neuropathy, we identified 11 proteins which positively correlated to neuropathy severity and warrant further investigation as potential biomarkers.

Anti-nociceptive and Anti-inflammatory Activities of Visnagin in Different Nociceptive and Inflammatory Mice Models

Pain management has been a severe public health issue throughout the world. Acute pain if not treated at the appropriate time can lead to chronic pain that can cause psychological and social distress. Nothing can be more rewarding than treating pain successfully for a physician. However, the use of chemical NSAIDs and opiate drugs has taken a toll on the patients with their unavoidable side effects. This study intends to explore the potential to treat pain by inhibiting nociception and inflammation with a safer, non-addictive, effective, and low-cost alternative agent from a natural source, visnagin. In vivo studies have been conducted using male Swiss albino mice as models for this research. Nociception was induced using different chemical and thermal stimuli such as acetic acid, glutamate, capsaicin, and formalin. To check for the anti-inflammatory properties, carrageenan was used to induce inflammation and the activity was assayed using peritoneal cavity leukocyte infiltration analysis and pro-inflammatory cytokine level comparison with the supplementation of visnagin at three different dosages. The findings of this study revealed that the visnagin treatment effectively attenuated the acetic acid-induced writhing response, glutamate-induced paw licking numbers, capsaicin-induced pain response, and formalin-induced biphasic licking incidences in the experimental mice models. Furthermore, the visnagin treatment remarkably suppressed the carrageenan-induced inflammation in mice, which is evident from the decreased leukocytes, mononuclear, and polymorphonuclear cell numbers in the mice. The levels of cytokines such as TNF-α, IL-1β, and IL-6 were effectively reduced by the visnagin treatment in the experimental mice. The results of open field test proved that the visnagin showed a better locomotor movement in the experimental mice. These results provided evidence for the potential activity of the visnagin against inflammatory and nociceptive responses in the mice.

Phenotypical characterization of exteroceptive sensation and pain symptoms on diabetic patients

BACKGROUD

Diabetic neuropathy (DN) is one of the most common complications of diabetes, affecting about half of individuals with the disease. Among the various symptoms of DN, the development of chronic pain stands out and manifests as exacerbated responses to sensorial stimuli. The conventional clinical treatments used for general neuropathy and associated painful symptoms, still brings uncomplete and unsatisfactory pain relief. Patients with neuropathic pain syndromes are heterogeneous. They present with a variety of sensory symptoms and pain qualities which difficult the correct diagnosis of sensory comorbidities and consequently, the appropriate chronic pain management.

AIMS

Herein, we aimed to demonstrate the existence of different sensory profiles on diabetic patients by investigating epidemiological and clinical data on the symptomatology of a group of patients with DN.

METHODS

This is a longitudinal and observational study, with a sample of 57 volunteers diagnosed with diabetes from outpatient day clinic of Hospital Universitário of the University of São Paulo-Brazil. After being invited and signed the Informed Consent Form (ICF), patients were submitted to clinical evaluation and filled out pain and quality of life questionnaires. They also performed quantitative sensory test (QST) and underwent skin biopsy for correlation with cutaneous neuropathology.

RESULTS

Data demonstrate that 70% of the studied sample presented some type of pain, manifesting in a neuropathic or nociceptive way, what has a negative impact on the life of patients with DM. We also demonstrated a positive association between pain and anxiety and depression, in addition to pain catastrophic thoughts. Three distinct profiles were identified in the sample, separated according to the symptoms of pain: (i) subjects without pain; (ii) with mild or moderate pain; (iii) subjects with severe pain. We also identified through skin biopsy that diabetic patients presented advanced sensory impairment, as a consequence of the degeneration of the myelinated and unmyelinated peripheral fibers. This study characterized the painful symptoms and exteroceptive sensation profile in these diabetic patients, associated to a considerable level of sensory degeneration, indicating, and reinforcing the importance of the long-term clinical monitoring of individuals diagnosed with DM, regarding their symptom profiles and exteroceptive sensitivity.

Quantitative sensory testing for assessment of somatosensory function in children and adolescents: a scoping review

Quantitative sensory testing (QST) refers to a group of noninvasive psychophysical tests that examine responses to a range of calibrated mechanical and thermal stimuli. Quantitative sensory testing has been used extensively in adult pain research and has more recently been applied to pediatric pain research. The aims of this scoping review were to map the current state of the field, to identify gaps in the literature, and to inform directions for future research. Comprehensive searches were run in 5 databases. Titles, abstracts, and full texts were screened by 2 reviewers. Data related to the study aims were extracted and analyzed descriptively. A total of 16,894 unique studies were identified, of which 505 were screened for eligibility. After a full-text review, 301 studies were retained for analysis. Date of publication ranged from 1966 to 2023. However, the majority of studies (61%) were published within the last decade. Studies included participants across the developmental trajectory (ie, early childhood to adolescence) and most often included a combination of school-age children and adolescents (49%). Approximately 23% of studies were conducted in healthy samples. Most studies (71%) used only one QST modality. Only 14% of studies reported using a standardized QST protocol. Quantitative sensory testing in pediatric populations is an emerging and rapidly growing area of pain research. Future work is needed using comprehensive, standardized QST protocols to harness the full potential that this procedure can offer to our understanding of pediatric pain.

Non-obese lipedema patients show a distinctly altered quantitative sensory testing profile with high diagnostic potential

Introduction and Objectives

Lipedema is a widespread severe chronic disease affecting mostly women. Characterized by painful bilateral fat accumulation in extremities sparing hands and feet, objective measurement-based diagnosis is currently missing. We tested for characteristic psychometric and/or sensory alterations including pain and for their potential for medical routine diagnosis.

Methods

Pain psychometry was assessed using the German Pain Questionnaire. Sensory sensitivity toward painful and nonpainful stimuli was characterized in non-obese lipedema patients and matched controls using the validated quantitative sensory testing (QST) protocol of the German Research Network on Neuropathic Pain.

Results

Lipedema patients showed no overt psychometric abnormalities. Pain was reported as somatic rather than psychosomatic aversive. All QST measurements were normal, but the z-score of pressure pain thresholds (PPT) was twofold reduced and the z-score of vibration detection thresholds (VDT) was two and a half times increased. Both thresholds were selectively altered at the affected thigh but not the unaffected hand. Receiver operating characteristic analysis of the combination of PPT and VDT of thigh vs hand into a PVTH score (PPT, VDT, thigh, hand-score) shows high sensitivity and specificity, categorizing correctly 95.8% of the participants as lipedema patients or healthy controls. Bayesian inference analysis corroborated the diagnostic potential of such a combined PVTH score.

Conclusion

We propose to assess PPT and VDT at the painful thigh and the pain-free hand. Combination in a PVTH score may allow a convenient lipedema diagnosis early during disease development.

Multidisciplinary strategies to treat painful mononeuropathies in the upper extremity: from lab to bedside

Neuropathic pain in the upper extremity is a serious problem, commonly involving relatively young patients. The pain causes loss of function and productivity, changes a patient's lifestyle and can progress into a chronic pain syndrome with secondary psychosocial co-morbidities. Treating patients with a painful mononeuropathy remains challenging, with a monodisciplinary approach often having limited treatment efficacy. This narrative review discusses how to deal with this challenge in the treatment of patients with peripheral nerve injury pain, addressing the four important pillars: (1) diagnosing a painful mononeuropathy; (2) clinical pain phenotyping; (3) personalized pain treatment; and (4) using a multidisciplinary team approach.