A cross-sectional cohort survey in 2100 patients with painful diabetic neuropathy and postherpetic neuralgia: Differences in demographic data and sensory symptoms

Epidermal Transient Receptor Potential Vanilloid 1 innervation is increased in patients with painful diabetic polyneuropathy experiencing ongoing burning pain

ABSTRACT

Preclinical studies suggested that Transient Receptor Potential Vanilloid 1 (TRPV1) channels contribute to neuropathic pain in animal models of diabetic polyneuropathy. Patients with painful diabetic polyneuropathy commonly experience ongoing burning pain. This study aimed at evaluating the association between this specific type of pain and TRPV1 intraepidermal nerve fibers in patients with painful diabetic polyneuropathy. We consecutively enrolled 70 patients with diabetic polyneuropathy. Each patient completed the Neuropathic Pain Symptom Inventory (NPSI) to identify the various types of neuropathic pain. All patients underwent a distal leg skin biopsy, with immunostaining of skin nerve fibers using antibodies for the pan-axonal marker Protein Gene Product 9.5 (PGP9.5), TRPV1, Calcitonin Gene-Related Peptide (CGRP), and Substance P. We found that 57% of patients (n = 40) had neuropathic pain symptoms, with ongoing burning pain being the most frequently reported type of pain at the NPSI (70% of patients with pain, n = 28). Patients with ongoing burning pain had higher TRPV1 intraepidermal nerve fiber density and TRPV1/PGP9.5 ratio compared with those with painless polyneuropathy ( P = 0.014, P = 0.013) and painful polyneuropathy with other types of pain ( P < 0.0001, P = 0.024); they also had increased CGRP dermal nerve fiber density compared with patients with painless polyneuropathy ( P = 0.005). Our study showed that ongoing burning pain is associated with an increased expression of intraepidermal TRPV1 fibers, as well as an increased dermal representation of CGRP fibers. These findings suggest that TRPV1 contributes to ongoing burning pain, possibly in conjunction with elevated CGRP expression, highlighting its significance as a therapeutic target for patients with painful diabetic polyneuropathy.

Transcutaneous electrical nerve stimulation as an adjuvant treatment for thoracolumbar acute hyperesthesia in chondrodystrophic dogs: a prospective blinded controlled clinical study

Introduction

Acute paraspinal hyperesthesia in dogs can result in a combination of nociceptive and neuropathic pain, often requiring pharmacological intervention. However, non-pharmacologic approaches, such as two-channel transcutaneous electrical nerve stimulation (TENS), may also be beneficial. Evidence from human medicine suggests that conventional TENS reduces pain scores and potentially decreases the need for analgesic medication. This study aimed to evaluate the efficacy of TENS as an adjunctive treatment for thoracolumbar paraspinal hyperesthesia in dogs.

Methods

This prospective, blinded, controlled cohort study was conducted in a clinical setting. Dogs diagnosed with paraspinal hyperesthesia, classified as grade 4 or 5 on the modified Frankel scale (MFS) and with a dynamic interactive visual analog scale (DIVAS) score ≥14, were included. The subjects were randomized into two groups: the study group (SG), which received standard pharmacological protocol (PSP) plus TENS, and the control group (CG), which received PSP only. Observers blinded to treatment allocation scored video recordings of the dogs. Assessments were performed every 24 hours from T0 (admission) to T8, with evaluations in SG occurring 5 minutes before each TENS session.

Results

A total of 818 dogs were enrolled, with 605 (74%) in the SG and 213 (26%) in the CG. In the first 48 hours, SG demonstrated a faster reduction in muscle tone compared to CG. While all dogs transitioned from a hyperesthetic to a non-painful state, SG showed a significantly faster recovery from T2 (48 h) to T4. A significant difference was observed between groups in DIVAS scores (p < 0.001). Additionally, SG had a shorter mean hospital stay (2.14 days) compared to CG, which required twice as long (p < 0.001).

Discussion

These findings suggest that TENS may be an effective adjunctive therapy for managing acute thoracolumbar hyperesthesia in dogs, promoting early recovery by reducing pain, medication dependency, and hospitalization duration. However, the study's reliance on subjective assessments presents a limitation, potentially introducing bias. Further research with objective outcome measures is necessary to validate these findings and optimize the integration of TENS in veterinary pain management protocols.

Increased TRPA1 functionality in the skin of rats and cancer patients following oxaliplatin treatment

Chemotherapy-induced peripheral neuropathy is a debilitating pathology affecting a majority of patients who are being treated with specific cytostatic compounds including oxaliplatin. Various in vitro, ex vivo and in vivo preclinical experiments indicate that transient receptor potential ankyrin 1 (TRPA1) plays a crucial role in the symptomatology of chemotherapy-induced peripheral neuropathy. However, it is unclear whether oxaliplatin also modulates the TRPA1 functionality in the skin of rodents or patients. Here, we quantified the vasodilation after topical application of the TRPA1 agonist cinnamaldehyde in a rodent model of chemotherapy-induced peripheral neuropathy (male Sprague Dawley rats, aged 6 weeks) as well as on fingers of patients suffering from chronic chemotherapy-induced peripheral neuropathy after oxaliplatin treatment. Compared to vehicle-treated rats, a cumulative dose of oxaliplatin 32 mg/kg enhanced the vasodilation after cinnamaldehyde application on rat abdominal skin. Likewise, also in patients with chronic chemotherapy-induced peripheral neuropathy after oxaliplatin, the response to cinnamaldehyde was significantly higher compared to sex- and age-matched healthy controls. Thereby, this study is the first to translate the evidence of increased TRPA1 functionality in vitro or ex vivo in rodents to in vivo conditions in human. The increased TRPA1 functionality in patients with chronic chemotherapy-induced peripheral neuropathy does not only confirm the potential of TRPA1 as target to hit to provide efficacious analgesia, it also paves the way for additional patient stratification on a molecular level and possible treatment response prediction. PERSPECTIVE: The cinnamaldehyde-induced, TRPA1-mediated vasodilation was enhanced in patients with oxaliplatin-induced peripheral neuropathy versus healthy controls, confirming the potential of TRPA1 as target-to-hit for this indication.

An update on botulinum toxin treatment of painful diabetic neuropathy, post-traumatic painful neuropathy/neuralgia, post-herpetic neuralgia and occipital neuralgia

The literature in botulinum toxin treatment for painful diabetic neuropathy (PDN), post traumatic neuralgia (PTN), postherpetic neuralgia (PHN) and occipital neuralgia (ON) was reviewed up to Oct 1st, 2024. Using the efficacy criteria set forth by the Assessment and Guideline subcommittee of the American Academy of Neurology, the current levels of efficacy for these conditions could be designated as followings: PDN: B (probably effective, two class II study), PTN: A (effective, two class I studies); PHN: A (effective, two class I studies), ON: (undetermined due to lack of blinded investigations). Due to the small number of patients in these studies, proof of efficacy requires conduction of controlled and blinded studies in large cohorts of patients with longer follow ups. Future prospects of botulinum therapy for these pain disorders were discussed along with the advantages of this mode of treatment over the current modes of treatment.

Therapeutic Efficacy of Adipose Tissue-Derived Components in Neuropathic Pain: A Systematic Review

BACKGROUND

Neuropathic pain results from a defect in the somatosensory nervous system caused by a diversity of etiologies. The effect of current treat-ment with analgesics and surgery is limited. Studies report the therapeutic use of adipose tissue-derived components to treat neuropathic pain as a new treatment modality.

OBJECTIVE

The aim of this systematic review was to investigate the therapeutic clinical efficacy of adipose tissue-derived components on neuro-pathic pain.

METHODS

PubMed, Medline, Cochrane and Embase databases were searched until August 2023. Clinical studies assessing neuropathic pain after autologous fat grafting or the therapeutic use of adipose tissue-derived com-ponents were included. The outcomes of interest were neuropathic pain and quality of life.

RESULTS

In total, 433 studies were identified, of which 109 dupli-cates were removed, 324 abstracts were screened and 314 articles were excluded. In total, ten studies were included for comparison. Fat grafting and cellular stromal vascular fraction were used as treatments. Fat grafting indications were post-mastectomy pain syndrome, neuromas, post-herpetic neuropathy, neuro-pathic scar pain and trigeminal neuropathic pain. In seven studies, neuropathic pain levels decreased, and overall, quality of life did not improve.

CONCLUSIONS

The therapeutic efficacy of adipose tissue-derived components in the treatment of neuropathic pain remains unclear due to the few performed clinical trials with small sample sizes for various indications. Larger and properly designed (randomized) controlled trials are required.

Beyond pain: Using Unsupervised Machine Learning to Identify Phenotypic Clusters of Small Fiber Neuropathy

Background and Objectives

Small fiber neuropathy (SFN) is characterized by dysfunction and loss of peripheral unmyelinated and thinly myelinated nerve fibers, resulting in a phenotype that includes varying combinations of somatosensory and dysautonomia symptoms, which can be profoundly disabling and lead to decreased quality of life. Treatment aimed mainly at pain reduction, which may not target the underlying pathophysiology, is frequently ineffective. Another impediment to the effective management of SFN may be the significant between-patient heterogeneity. Accordingly, we launched this study to gain insights into the symptomatic variability of SFN and determine if SFN patients can be sub-grouped based on clinical characteristics.

Methods

To characterize the phenotype and investigate how patients with SFN differ from those with large fiber involvement, 105 patients with skin-biopsy proven SFN and 45 with mixed fiber neuropathy (MFN) were recruited. Using unsupervised machine learning, SFN patients were clustered based upon symptom concurrence and severity. Demographics, clinical data, symptoms, and skin biopsy- and laboratory findings were compared between the groups.

Results

MFN- as compared to SFN patients, were more likely to be male, older, had a lower intraepidermal nerve fiber density at the ankle and more frequent abnormal immunofixation. Beyond these differences, symptom prevalence and intensities were similar in the two cohorts. SFN patients comprised three distinct phenotypic clusters, which differed significantly in symptom severity, co-occurrence, localization, and skin biopsy findings. Only one subgroup, constituting about 20% of the patient population, was characterized by intense neuropathic pain, which was always associated with several other SFN symptoms of similarly high intensities. A pauci-symptomatic cluster comprised patients who experienced few SFN symptoms, generally of low to moderate intensity. The largest cluster was characterized by intense fatigue, myalgias and subjective weakness, but lower intensities of burning pain and paresthesia.

Discussion

This data-driven study introduces a new approach to subgrouping patients with SFN. Considering both neuropathic pain and pernicious symptoms beyond pain, we identified three clusters, which may be related to distinct pathophysiological mechanisms. Although additional validation will be required, our findings represent a step towards stratified treatment approaches and, ultimately, personalized treatment.

Advances of Schwann cells in peripheral nerve regeneration: From mechanism to cell therapy

Peripheral nerve injuries (PNIs) frequently occur due to various factors, including mechanical trauma such as accidents or tool-related incidents, as well as complications arising from diseases like tumor resection. These injuries frequently result in persistent numbness, impaired motor and sensory functions, neuropathic pain, or even paralysis, which can impose a significant financial burden on patients due to outcomes that often fall short of expectations. The most frequently employed clinical treatment for PNIs involves either direct sutures of the severed ends or bridging the proximal and distal stumps using autologous nerve grafts. However, autologous nerve transplantation may result in sensory and motor functional loss at the donor site, as well as neuroma formation and scarring. Transplantation of Schwann cells/Schwann cell-like cells has emerged as a promising cellular therapy to reconstruct the microenvironment and facilitate peripheral nerve regeneration. In this review, we summarize the role of Schwann cells and recent advances in Schwann cell therapy in peripheral nerve regeneration. We summarize current techniques used in cell therapy, including cell injection, 3D-printed scaffolds for cell delivery, cell encapsulation techniques, as well as the cell types employed in experiments, experimental models, and research findings. At the end of the paper, we summarize the challenges and advantages of various cells (including ESCs, iPSCs, and BMSCs) in clinical cell therapy. Our goal is to provide the theoretical and experimental basis for future treatments targeting peripheral nerves, highlighting the potential of cell therapy and tissue engineering as invaluable resources for promoting nerve regeneration.

Association of nociplastic and neuropathic pain components with the presence of residual symptoms in patients with axial spondyloarthritis receiving biological disease-modifying antirheumatic drugs

OBJECTIVE

To evaluate the association of nociplastic (NoP) and neuropathic pain (NP) components with residual symptoms in patients with radiographic axial spondyloarthritis (r-axSpA) receiving biological disease-modifying antirheumatic drugs (bDMARDs).

METHODS

78 patients with r-axSpA from the GErman SPondyloarthritis Inception Cohort receiving a bDMARD for at least 3 months were included in this analysis. The Widespread Pain Index (WPI) and the PainDETECT (PD) questionnaire were used to quantify the NoP and the NP components, respectively. Axial Spondyloarthritis Disease Activity Score (ASDAS) and the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) were used as measures of residual symptoms. C reactive protein (CRP) was used as a measure of systemic inflammatory activity. Univariable and multivariable regression analyses of disease activity were performed. The regions of the WPI score and items of the PD score were used for cluster analyses.

RESULTS

Linear multivariable regression analysis showed that WPI and PD were independently associated with ASDAS (b=0.1, 95% CI 0.04 to 0.17, and b=0.05, 95% CI 0.02 to 0.08, respectively) and BASDAI (b=0.24, 95% CI 0.08 to 0.39, and b=0.17, 95% CI 0.1 to 0.25, respectively) in r-axSpA patients receiving stable treatment with bDMARDs. Furthermore, WPI and PD were found to be significantly associated with the presence of relevant residual symptoms as defined by BASDAI ≥4 (OR 1.93, 95% CI 1.09 to 4.15, and OR 1.32, 95% CI 1.04 to 1.85, respectively). The effects were present also in patients with normal level of CRP. Cluster analysis revealed three distinct pain distribution profiles and four specific sensory symptom constellations allowing differentiation of different pain subtypes.

CONCLUSION

Both NoP and NP components seem to be associated with residual symptoms in patients with r-axSpA receiving treatment with bDMARDs.

The Pharmacological Treatment of Neuropathic Pain in Children

The International Association for the Study of Pain (IASP) defines neuropathic pain as pain caused by a lesion or disease of the somatosensory nervous system. It is characterized as a clinical condition in which diagnostic studies reveal an underlying cause of an abnormality in the peripheral or central nervous system. Many common causes of neuropathic pain in adults are rare in children. The purpose of this focused narrative review is, to 1) provide an overview of neuropathic pain in children, 2) highlight unique considerations related to the diagnosis and mechanisms of neuropathic pain in children, and 3) perform a comprehensive analysis of the pharmacological treatments available. We emphasize that data for routine use of pharmacological agents in children with neuropathic pain are largely inferred from adult literature with little research performed on pediatric populations, yet have clear evidence of harms to pediatric patients. Based on these findings, we propose risk mitigation strategies such as utilizing topical treatments whenever possible, assessing pain phenotyping to guide drug class choice, and considering pharmaceuticals in the broader context of the multidisciplinary treatment of pediatric pain. Furthermore, we highlight important directions for future research on pediatric neuropathic pain treatment.

Predictors of neuropathic pain and related functional disability in sciatica patients: a cross-sectional study

PURPOSE

The aim of the present paper was to assess neuropathic pain and its predictors among patients with sciatica. In addition, we sought to investigate the predictors of functional disability in sciatica patients with neuropathic pain.

METHODS

A cross-sectional study was carried out on a sample of 100 sciatica patients aged 18 years and older with a radiating pain from the lower back down to the leg below the knee. Information about socio-demographic characteristics, duration of symptoms, being treated or not, type of treatment, side of sciatica, presence of back pain, leg pain occurrence, leg pain intensity, functional disability and pain catastrophizing were collected.

RESULTS

Of the total patients, 57% had neuropathic pain. Multivariable analysis showed that leg pain intensity was higher in the neuropathic pain group as compared to the non-neuropathic pain group. Also, patients with left sciatica were less likely to have neuropathic pain than patients with right sciatica. Patients with neuropathic pain having high levels of pain catastrophizing and being on bed rest for at least one week were at a higher risk of developing functional disability as compared to their counterparts.

CONCLUSION

Low levels of pain catastrophizing and less bed rest should be considered in interventions aimed at improving the functional ability for sciatica patients with neuropathic pain.

Comprehensive quantitative sensory testing shows altered sensory function in women with chronic pelvic pain: results from the Translational Research in Pelvic Pain (TRiPP) Study

ABSTRACT

Chronic pelvic pain (CPP), despite its high prevalence, is still relatively poorly understood mechanistically. This study, as part of the Translational Research in Pelvic Pain (TRiPP) project, has used a full quantitative sensory testing (QST) paradigm to profile n = 85 women with and without CPP (endometriosis or bladder pain specifically). We used the foot as a control site and abdomen as the test site. Across 5 diagnostically determined subgroups, we found features which are common across different aetiologies, eg, gain of function in pressure pain threshold (PPT) when assessing responses from the lower abdomen or pelvis (referred pain site). However, disease-specific phenotypes were also identified, eg, greater mechanical allodynia in endometriosis, despite there being large heterogeneities within diagnostic groups. The most common QST sensory phenotype was mechanical hyperalgesia (>50% across all the groups). A "healthy' sensory phenotype was seen in <7% of CPP participants. Specific QST measures correlated with sensory symptoms assessed by the painDETECT questionnaire (pressure-evoked pain [painDETECT] and PPT [QST] [ r = 0.47, P < 0.001]; mechanical hyperalgesia (painDETECT) and mechanical pain sensitivity [MPS from QST] [ r = 0.38, P = 0.009]). The data suggest that participants with CPP are sensitive to both deep tissue and cutaneous inputs, suggesting that central mechanisms may be important in this cohort. We also see phenotypes such as thermal hyperalgesia, which may be the result of peripheral mechanisms, such as irritable nociceptors. This highlights the importance of stratifying patients into clinically meaningful phenotypes, which may have implications for the development of better therapeutic strategies for CPP.

Alzheimer's disease as a viral disease: Revisiting the infectious hypothesis

Alzheimer's disease (AD) represents the most frequent type of dementia in elderly people. Two major forms of the disease exist: sporadic - the causes of which have not yet been fully understood - and familial - inherited within families from generation to generation, with a clear autosomal dominant transmission of mutations in Presenilin 1 (PSEN1), 2 (PSEN2) or Amyloid Precursors Protein (APP) genes. The main hallmark of AD consists of extracellular deposits of amyloid-beta (Aβ) peptide and intracellular deposits of the hyperphosphorylated form of the tau protein. An ever-growing body of research supports the viral infectious hypothesis of sporadic forms of AD. In particular, it has been shown that several herpes viruses (i.e., HHV-1, HHV-2, HHV-3 or varicella zoster virus, HHV-4 or Epstein Barr virus, HHV-5 or cytomegalovirus, HHV-6A and B, HHV-7), flaviviruses (i.e., Zika virus, Dengue fever virus, Japanese encephalitis virus) as well as Human Immunodeficiency Virus (HIV), hepatitis viruses (HAV, HBV, HCV, HDV, HEV), SARS-CoV2, Ljungan virus (LV), Influenza A virus and Borna disease virus, could increase the risk of AD. Here, we summarized and discussed these results. Based on these findings, significant issues for future studies are also put forward.

Further evaluation of inflammatory and non-inflammatory aspects of pain in rheumatoid arthritis patients

Objective

A high discrepancy between the number of tender and swollen joints (e.g. ΔTSJ ≥ 7) has previously been used as an indication for the presence of changes in central mechanisms in patients with moderate-to-high disease activity. In this study, we explored whether the ΔTSJ can also be used to obtain insights into the underlying pain mechanisms in patients with on average well-controlled disease activity.

Methods

A 2 year retrospective analysis of routinely obtained 28-joint DAS (DAS28) components was performed on 45 patients with low inflammatory activity at the group level. All patients underwent pressure pain threshold (PPT) and electrical pain threshold (EPT) measurements and completed four self-report questionnaires [short-form 36 (SF-36v2); central sensitization inventory (CSI); generalized pain questionnaire (GPQ); and the pain catastrophizing scale (PCS)].

Results

Patients with a ΔTSJ ≥ 3 at least once in the past 2 years showed significantly lower EPT and PPT values and higher levels of pain and disability on the SF-36v2 compared with the ΔTSJ < 3 group. Furthermore, GPQ scores were significantly higher in those with ΔTSJ ≥ 3, while CSI and PCS scores were similar.

Conclusion

These findings suggest that in patients in the ΔTSJ ≥ 3 group, mechanisms other than inflammation (only) underlie the pain. Moreover, our findings suggest that among the multiple potential underlying psychological mechanisms, pain catastrophizing (as measured by the PCS) and psychological hypervigilance (as measured by the CSI) do not play an important role. These findings could be useful in the clinical management of the patient. Depending on the dominant mechanism underlying the (persistent) pain, patients might respond differently to treatment.

Orofacial Pain and Dentistry Management: Guidelines for a More Comprehensive Evidence-Based Approach

Orofacial pain represents one of the most common health problems that negatively affects the activities of daily living. However, the mechanisms underlying these conditions are still unclear, and their comprehensive management is often lacking. Moreover, even if pain is a common symptom in dentistry, differential diagnostic procedures are needed to exclude other pain origins. Misinterpretation of the pain origin, in fact, can lead to misdiagnosis and to subsequent mismanagement. Pain in the orofacial area is the most common reason for patients to visit the dentist, but this area is complex, and the pain could be associated with the hard and soft tissues of the head, face, oral cavity, or to a dysfunction of the nervous system. Considering that the origins of orofacial pain can be many and varied, a thorough assessment of the situation is necessary to enable the most appropriate diagnostic pathway to be followed to achieve optimal clinical and therapeutic management.

The association of self-reported symptoms of central sensitization and sleep disturbances in neuropathic pain

Introduction

Patients with neuropathic pain (NP) report a higher impairment of quality of life and sleep than patients with chronic pain without neuropathic characteristics. These include somatosensory peculiarities like allodynia, a surrogate marker for central sensitization.

Objectives

This study aimed to investigate the relation between symptoms of central sensitization and sleep disturbances in patients with NP.

Methods

Within this cross-sectional study, data sets of 3339 patients with chronic NP syndromes (painful diabetic polyneuropathy, n = 543; postherpetic neuralgia, n = 1480) or complex regional pain syndromes (CRPS, n = 1316) were analyzed. Neuropathic pain symptoms were assessed with the painDETECT questionnaire (PD-Q), depression with the Patient Health Questionnaire-9, and sleep impairment with items of the Medical Outcomes Study Sleep Scale in 4 subscales. The association of demographic/clinical data, somatosensory phenotype, depression, and pain intensity with sleep impairment was assessed by unadjusted Spearman correlation analyses and multivariable regression analyses.

Results

Sleep impairment was observed in all pain aetiologies although with some significant differences in the single sleep items. The intensity of the individual PD-Q items differed to some extent between the 3 pain entities, whereas the PD-Q sum score was similar. Thermal hyperalgesia and burning assessed by the PD-Q were significantly associated with sleep disturbance, adequacy, and quantity but not with sleep somnolence. Only depression and self-reported allodynia had a significant relation to all 4 sleep elements.

Conclusion

Beside depression, allodynia as a surrogate marker hints to a possible impact of central sensitization on the sleep disruption of patients with NP.

Multisensory sensitivity differentiates between multiple chronic pain conditions and pain-free individuals

ABSTRACT

Multisensory sensitivity (MSS) to nonpainful stimuli has been identified as a risk factor for the presence of coexisting chronic pain conditions. However, it remains unclear whether MSS can differentiate pain phenotypes involving different levels of central sensitivity. Both pain-free and those with chronic pain, particularly fibromyalgia (FM), migraine, or low back pain (LBP) were recruited, with pain comorbidities assessed. MSS was highest in FM, followed by migraine, then LBP, and lowest in pain-free individuals (adjusted between condition Cohen d = 0.32-1.2, P ≤ 0.0007). However, when secondly grouping patients by the total number of pain comorbidities reported, those with a single pain condition (but not FM) did not have significantly elevated MSS vs pain-free individuals (adj d= 0.17, P = 0.18). Elevated MSS scores produced increased odds of having 2 or more pain comorbidities; OR [95% CI] =2.0 [1.15, 3.42], without, and 5.6 [2.74, 11.28], with FM ( P ≤ 0.0001). Furthermore, those with low MSS levels were 55% to 87% less likely to have ≥ 2 pain comorbidities with or without FM (OR 0.45 [0.22, 0.88]-0.13 [0.05, 0.39]; P ≤ 0.0001). Our findings support that MSS can differentiate between pain phenotypes with different degrees of expected central mechanism involvement and also serve as a risk and resilience marker for total coexisting chronic pain conditions. This supports the use of MSS as a marker of heightened central nervous system processing and thus may serve as a clinically feasible assessment to better profile pain phenotypes with the goal of improving personalized treatment.

Precision Medicine in Neuropathic Pain

Neuropathic pain is a common chronic pain condition that is caused by a lesion or disease of the somatosensory nervous system. The multitude of sensory negative and positive sensations and associated comorbidities have a major impact on quality of life of affected patients. Current treatment options often only lead to a partial pain relief or are even completely ineffective. In addition, many clinical trials for the development of new drugs have not met the primary endpoint. Therefore, there is still an unmet clinical need in neuropathic pain syndromes. One reason for this therapeutic dilemma could be the heterogeneity of neuropathic pain with a variety of pathophysiological pain mechanisms that are expressed differently in each patient regardless of the underlying disease etiology. Reclassification of neuropathic pain syndromes therefore focuses on the underlying mechanisms of pain development rather than the disease etiology. A priori stratification of patients based on these individual mechanisms could allow the identification of potential treatment responders and thus realize the concept of a mechanism-based treatment. As no biomarkers for pain mechanisms have been discovered yet, one has to rely on surrogate markers that are thought to be closely related to these mechanisms. In this chapter, we present promising predictive biomarkers, focusing in particular on sensory symptoms and signs assessed by patient-reported outcome measures and sensory testing, and discuss how these tools might be used in clinical trials in the future.

Subgrouping patients with zoster-associated pain according to sensory symptom profiles: A cluster analysis

Background and goal of study

Patients with zoster-associated pain exhibit a variety of sensory symptoms and forms of pain and complain of different pain patterns. The purpose of this study is to subgroup patients with zoster-associated pain who visited a hospital using painDETECT sensory symptom scores, analyze their respective characteristics and pain-related data, and compare similarities and differences among the groups.

Materials and methods

The characteristics of 1,050 patients complaining of zoster-associated pain and pain-related data were reviewed retrospectively. To identify subgroups of patients with zoster-associated pain according to sensory symptom profiles, a hierarchical cluster analysis was performed based on the responses to a painDETECT questionnaire. Demographics and pain-related data were compared among all subgroups.

Results and discussion

Patients with zoster-associated pain were classified into 5 subgroups according to the distribution of sensory profiles, with each subgroup exhibiting distinct differences in the expression of sensory symptoms. Patients in cluster 1 complained of burning sensations, allodynia, and thermal sensitivity, but felt numbness less strongly. Cluster 2 and 3 patients complained of burning sensations and electric shock-like pain, respectively. Cluster 4 patients complained of most sensory symptoms at similar intensities and reported relatively strong prickling pain. Cluster 5 patients suffered from both burning and shock-like pains. Patient ages and the prevalence of cardiovascular disease were significantly lower in cluster 1. Patients in clusters 1 and 4 reported longer pain duration compared with those in clusters 2 and 3. However, no significant differences were found with respect to sex, body mass index, diabetes mellitus, mental health problems, and sleep disturbance. Pain scores, distribution of dermatomes and gabapentinoid use were also similar among the groups.

Conclusions

Five different subgroups of patients with zoster-associated pain were identified on the basis of sensory symptoms. A subgroup of younger patients with longer pain duration showed specific and distinct symptoms, such as burning sensations and allodynia. Unlike patients with acute or subacute pain, patients with chronic pain were associated with diverse sensory symptom profiles.

Effects of Neural Mobilization on Sensory Dysfunction and Peripheral Nerve Degeneration in Rats With Painful Diabetic Neuropathy

OBJECTIVE

This study aims to evaluate the effectiveness of neural mobilization (NM) in the management of sensory dysfunction and nerve degeneration related to experimental painful diabetic neuropathy (PDN).

METHODS

This is a pre-clinical animal study performed in the streptozocin-induced diabetic rat model. Three groups were included: a treatment group of rats with PDN receiving NM under anesthesia (PDN-NM, n = 10), a sham treatment group of rats with PDN that received only anesthesia (PDN-Sham, n = 9), and a vehicle control group with nondiabetic animals (Vehicle, n = 10). Rats in the PDN-NM and PDN-Sham groups received 1 treatment session on days 10, 12, and 14 after streptozocin injection, with a 48-hour rest period between sessions. Behavioral tests were performed using von Frey and Plantar tests. Evaluation for peripheral nerve degeneration was performed through measuring protein gene product 9.5-positive intra-epidermal nerve fiber density in hind-paw skin biopsies. All measurements were performed by a blinded investigator.

RESULTS

The behavioral tests showed that a single NM session could reduce hyperalgesia, which was maintained for 48 hours. The second treatment session further improved this treatment effect, and the third session maintained it. These results suggest that it requires multiple treatment sessions to produce and maintain hypoalgesic effects. Skin biopsy analysis showed that the protein gene product 9.5-positive intra-epidermal nerve fiber density was higher on the experimental side of the PDN-NM group compared with the PDN-Sham group, suggesting NM may mitigate the degeneration of peripheral nerves.

CONCLUSION

This study demonstrated that NM may be an effective method to manage experimentally induced PDN, potentially through mitigation of nerve degeneration. Further studies are needed to develop standardized protocols for clinical use.

IMPACT

These findings provide neurophysiological evidence for the use of NM in PDN and can form the basis for the development of physical therapy-based programs in clinics.

Similarities in the Neuropathy Phenotype of Cancer Survivors Who Received Different Classes of Chemotherapy Drugs

With the advent of platinum and taxane compounds used as single agents or in combination regimens, survival rates for some of the most common cancers have improved substantially. However, information on differences in the chemotherapy-induced peripheral neuropathy (CIPN) phenotype among single and combination regimens is limited. Study's purposes were to evaluate for differences in demographic and clinical characteristics; subjective and objective measures of CIPN; as well as the severity of common symptoms and quality of life among survivors who received platinum- (n = 95), taxane- (n = 200), or platinum and taxane-containing (n = 131) regimens. Patients completed self-report questionnaires (ie, duration of CIPN, pain intensity, pain qualities, pain interference) and underwent a physical examination that evaluated light touch, pain, and cold sensations and balance. For most of the subjective and objective measures of CIPN, as well as symptom severity and quality of life scores, no differences were found among the 3 chemotherapy groups. In all 3 chemotherapy treatment groups, CIPN was a painful, small fiber, and length dependent neuropathy. These findings support the hypothesis that CIPN induced by different classes of chemotherapy, as single agents or in combination, produce a similar CIPN phenotype which raises the possibility that CIPN induced by diverse chemotherapy protocols has the same underlying mechanism. PERSPECTIVE: In this study, that compared patients who received only platinum, only taxane, or both platinum and taxane containing regimens, no differences were found among the 3 groups in the CIPN phenotype. Findings raise the possibility that CIPN induced by diverse chemotherapy protocols has the same underlying mechanism.

Fire Needling Acupuncture for Adult Patients with Acute Herpes Zoster: Protocol of a Systematic Review and Meta-Analysis

Background

Acute herpes zoster (HZ) is characterized as a vesicular rash with unilateral distribution produced by the reactivation of varicella zoster virus. It can induce various comorbidities that can adversely influence the quality of life of patients. The purpose of this systematic review is to assess the effect and safety of fire needling acupuncture on acute HZ.

Methods

Three English databases (PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials) and four Chinese Databases (China National Knowledge Infrastructure, Wanfang database, Chongqing VIP database, and China Biology Medicine database) will be searched from their inceptions to July 2022. Randomized controlled trials investigating fire needling acupuncture therapy for acute HZ will be included, regardless of publication status. Two reviewers will independently conduct the study screening, data extraction, and research quality assessments. The primary outcome measures are the Pain Visual Analogue Scale and the occurrence of postherpetic neuralgia. Secondary outcomes measures are the evaluation of skin lesions, time to resolution of pain, tolerance evaluation, total effective rate, adverse events and changes in inflammatory and immune suppression markers in peripheral plasma. All included studies will be assessed for methodological quality via the Cochrane Collaboration’s bias risk assessment tool. Meta-analyses will be undertaken using Review Manager V.5.3 software. The findings will be reported as the risk ratio of the binary data and the mean difference (MD) or standardized MD of the continuous data. Subgroup analyses and sensitivity analyses will be conducted where appropriate. The Grading of Recommendations Assessment, Development, and Evaluation will be used to assess evidence certainty.

Results

From the study, we will ascertain the effects and safety of fire needling acupuncture on acute HZ.

Conclusion

This study will validate the effects and safety of fire needling acupuncture in the management of acute HZ, generating new evidence to guide acupuncture interventions for acute HZ in the future.

Registration Number

PROSPERO CRD42020199047.

Analysis of clinical phenotypes of neuropathic symptoms in patients with type 2 diabetes: A multicenter study

Aims/Introduction

We investigated the classification of diabetic peripheral neuropathy (DPN) patients by subjective symptoms, and identification of the relationship between the patterns and intensities of symptoms and the clustered groups of DPN patients.

Materials and Methods

This multicenter study analyzed epidemiological data and sensory symptoms of 649 patients with DPN. Cluster analysis was carried out to identify subgroups of patients with characteristic symptom profiles. Factor analysis was carried out to investigate the symptom patterns of the clustered groups of DPN patients.

Results

Three clusters of patients with DPN were identified: severe symptoms with decreased quality of life (cluster 1, n = 119, 18.3%), predominantly insensate symptoms with relatively good quality of life (cluster 2, n = 318, 49.0%), and moderate pain intensity and decreased quality of life (cluster 3, n = 204, 31.4%). The frequency of symptoms on each item of the Michigan Neuropathy Screening Instrument questionnaire showed a similar distribution according to pain intensities along with the three clusters.

Conclusions

Our study supports the hypothesis that diversity in sensory symptoms exists in patients with DPN. Heterogeneity in DPN patients should be taken into account for a more stratified or individualized treatment approach. Based on a multicenter study, we identified three clusters of patients with DPN. Our research supports the hypothesis that diversity in sensory symptoms exists in patients with DPN. Heterogeneity in DPN patients should be taken into account for a more stratified or individualized treatment approach.

Evidence-Based Treatment of Painful Diabetic Neuropathy: a Systematic Review

PURPOSE OF REVIEW

Painful diabetic neuropathy (PDN) manifests with pain typically in the distal lower extremities and can be challenging to treat. The authors appraised the literature for evidence on conservative, pharmacological, and neuromodulation treatment options for PDN.

RECENT FINDINGS

Intensive glycemic control with insulin in patients with type 1 diabetes may be associated with lower odds of distal symmetric polyneuropathy compared to patients who receive conventional insulin therapy. First-line pharmacologic therapy for PDN includes gabapentinoids (pregabalin and gabapentin) and duloxetine. Additional pharmacologic modalities that are approved by the Food and Drug Administration (FDA) but are considered second-line agents include tapentadol and 8% capsaicin patch, although studies have revealed modest treatment effects from these modalities. There is level I evidence on the use of dorsal column spinal cord stimulation (SCS) for treatment of PDN, delivering either a 10-kHz waveform or tonic waveform. In summary, this review provides an overview of treatment options for PDN. Furthermore, it provides updates on the level of evidence for SCS therapy in cases of PDN refractory to conventional medical therapy.

Questionnaire-based somatosensory profiling in breast cancer survivors: are we there yet? Associations between questionnaires and quantitative sensory testing

PURPOSE

Pain and sensory disturbances are common side effects of breast cancer treatment. Differential somatosensory functioning may reflect distinct pathophysiological backgrounds and therapeutic needs. Aim was to examine whether questionnaires evaluating signs and symptoms related to somatosensory functioning correlate sufficiently with quantitative sensory testing (QST) in breast cancer survivors to warrant consideration for somatosensory profiling in clinical practice.

METHODS

One year after breast cancer surgery, 147 women underwent QST and completed following questionnaires: Douleur Neuropathique en 4 questions (DN4), Central Sensitization Inventory, Margolis Pain Diagram and Visual Analog Scales (VAS). Associations between the questionnaires and QST were evaluated using Spearman correlation coefficients (rs).

RESULTS

Significant but weak (rs < 0.30) correlations were found between total DN4 score and QST results at the inner upper arm for detection of sharp stimuli (rs = 0.227), cold stimuli (rs = -0.186), and painful heat stimuli (rs = 0.179), as well as between QST evaluating conditioned pain modulation and the Margolis Pain Diagram on one hand (rs = 0.176) and minimum-maximum pain intensity differences (VAS) on the other (rs = -0.170).

CONCLUSION

Questionnaires evaluating signs and symptoms related to somatosensory functioning are insufficient for somatosensory profiling. Although somatosensory profiling may be valuable in a mechanism-based management, more research on the most appropriate clinical tools is needed.IMPLICATIONS FOR REHABILITATIONClinicians should be able to recognize that patients with persistent pain or sensory disturbances following breast cancer surgery may have a component of altered somatosensory processing as a significant contributor to their complaint in order to address it appropriately.Somatosensory profiling has yet to be implemented into clinical practice.No evidence-based recommendations can be made on the use of self-reported questionnaires to assess somatosensory processing in a breast cancer population based on the findings of this study.It is suggested to combine information on how individuals process and experience somatosensory stimulation with information from the patient interview or questionnaires to consider which biological, psychological and/or social factors may drive or sustain these neurophysiological processes.

Is There a Neuropathic-Like Component to Endometriosis-Associated Pain? Results From a Large Cohort Questionnaire Study

Background: Pain is one of the primary symptoms of endometriosis, a chronic inflammatory condition characterised by the presence of endometrial tissue outside the uterus. Endometriosis-associated pain is commonly considered as nociceptive in nature, but its clinical presentation suggests that it might have neuropathic-like properties in a subgroup of patients.

Methods: This is a cross sectional study using an online survey. The survey was distributed by patient support websites. The survey was composed of validated questionnaires assessing pain symptoms, psychological measures and questions about number of surgeries.

Main Results: We had 1,417 responses which met the inclusion criteria. Using standard painDETECT cut-off scores, we found that pain was classified as neuropathic in 40% of patients and as mixed neuropathic/nociceptive in a further 35%. In line with observations in other neuropathic conditions, the neuropathic subgroup reported higher pain intensities, greater psychological distress and cognitive impairment. Neuropathic pain was also more likely in those with more surgeries to the abdomen and a longer history of pain. As revealed by a cluster analysis, those with a neuropathic pain component could further be divided into two subgroups based on their sensory profile.

Conclusions: The data presented here indicate that endometriosis-associated pain includes a neuropathic-like component in a substantial proportion of women. Although further investigation is required, our finding challenges the current conceptualisation of endometriosis-associated pain as nociceptive and advocates for a new perspective on this type of pain, which is so debilitating to a large number of women.

Mitochondrial calcium uniporter deletion prevents painful diabetic neuropathy by restoring mitochondrial morphology and dynamics

ABSTRACT

Painful diabetic neuropathy (PDN) is an intractable complication affecting 25% of diabetic patients. Painful diabetic neuropathy is characterized by neuropathic pain accompanied by dorsal root ganglion (DRG) nociceptor hyperexcitability, resulting in calcium overload, axonal degeneration, and loss of cutaneous innervation. The molecular pathways underlying these effects are unknown. Using high-throughput and deep-proteome profiling, we found that mitochondrial fission proteins were elevated in DRG neurons from mice with PDN induced by a high-fat diet (HFD). In vivo calcium imaging revealed increased calcium signaling in DRG nociceptors from mice with PDN. Furthermore, using electron microscopy, we showed that mitochondria in DRG nociceptors had fragmented morphology as early as 2 weeks after starting HFD, preceding the onset of mechanical allodynia and small-fiber degeneration. Moreover, preventing calcium entry into the mitochondria, by selectively deleting the mitochondrial calcium uniporter from these neurons, restored normal mitochondrial morphology, prevented axonal degeneration, and reversed mechanical allodynia in the HFD mouse model of PDN. These studies suggest a molecular cascade linking neuropathic pain to axonal degeneration in PDN. In particular, nociceptor hyperexcitability and the associated increased intracellular calcium concentrations could lead to excessive calcium entry into mitochondria mediated by the mitochondrial calcium uniporter, resulting in increased calcium-dependent mitochondrial fission and ultimately contributing to small-fiber degeneration and neuropathic pain in PDN. Hence, we propose that targeting calcium entry into nociceptor mitochondria may represent a promising effective and disease-modifying therapeutic approach for this currently intractable and widespread affliction. Moreover, these results are likely to inform studies of other neurodegenerative disease involving similar underlying events.

Subgrouping of Peripheral Neuropathic Pain Patients According to Sensory Symptom Profile Using the Korean Version of the PainDETECT Questionnaire

BACKGROUND

A culturally validated Korean version of the PainDETECT Questionnaire (PD-Q) was used to identify neuropathic pain components (NeP) in patients suffering from chronic pain. The purpose of this study was to determine if the Korean PD-Q can be used to subgroup patients with peripheral NeP according to sensory symptom profiles.

METHODS

This study included 400 Korean patients with peripheral neuropathic pain diagnosed as probable or definite NeP. The total scores and subscores for each item in PD-Q were transformed into a Z-score for standardization. Hierarchical cluster analysis was performed to identify clusters of subjects by PD-Q scores.

RESULTS

The mean total PD-Q score of the study participants was 14.57 ± 6.46. A hierarchical cluster analysis identified 5 clusters with distinct pain characteristic profiles. Cluster 1 had relatively severe burning and tingling sensations. The mean total PD-Q score for cluster 2 was the lowest of the 5 clusters. Cluster 3 tended to be vulnerable to pain in response to cold/heat stimulation. Cluster 4 showed relatively severe pain induced by physical stimuli, such as light touch or slight pressure. Cluster 5 had high scores for all NeP symptoms.

CONCLUSION

This study demonstrates the ability of patients to cluster by symptoms using the Korean PD-Q. Subgrouping of peripheral neuropathic pain by sensory symptom profile may be useful in making effective drug treatment decisions.

The Treatment of Painful Diabetic Neuropathy

Painful diabetic peripheral neuropathy (painful-DPN) is a highly prevalent and disabling condition, affecting up to one-third of patients with diabetes. This condition can have a profound impact resulting in a poor quality of life, disruption of employment, impaired sleep, and poor mental health with an excess of depression and anxiety. The management of painful-DPN poses a great challenge. Unfortunately, currently there are no Food and Drug Administration (USA) approved disease-modifying treatments for diabetic peripheral neuropathy (DPN) as trials of putative pathogenetic treatments have failed at phase 3 clinical trial stage. Therefore, the focus of managing painful- DPN other than improving glycaemic control and cardiovascular risk factor modification is treating symptoms. The recommended treatments based on expert international consensus for painful- DPN have remained essentially unchanged for the last decade. Both the serotonin re-uptake inhibitor (SNRI) duloxetine and α2δ ligand pregabalin have the most robust evidence for treating painful-DPN. The weak opioids (e.g. tapentadol and tramadol, both of which have an SNRI effect), tricyclic antidepressants such as amitriptyline and α2δ ligand gabapentin are also widely recommended and prescribed agents. Opioids (except tramadol and tapentadol), should be prescribed with caution in view of the lack of definitive data surrounding efficacy, concerns surrounding addiction and adverse events. Recently, emerging therapies have gained local licenses, including the α2δ ligand mirogabalin (Japan) and the high dose 8% capsaicin patch (FDA and Europe). The management of refractory painful-DPN is difficult; specialist pain services may offer off-label therapies (e.g. botulinum toxin, intravenous lidocaine and spinal cord stimulation), although there is limited clinical trial evidence supporting their use. Additionally, despite combination therapy being commonly used clinically, there is little evidence supporting this practise. There is a need for further clinical trials to assess novel therapeutic agents, optimal combination therapy and existing agents to determine which are the most effective for the treatment of painful-DPN. This article reviews the evidence for the treatment of painful-DPN, including emerging treatment strategies such as novel compounds and stratification of patients according to individual characteristics (e.g. pain phenotype, neuroimaging and genotype) to improve treatment responses.

Cross-cultural adaptation and validation of the Persian version of the painDETECT questionnaire

OBJECTIVE

The purpose of this study was to translate and cross-culturally adapt the painDETECT questionnaire into the Persian language and assess the clinometric properties of the translated version (P-PDQ).

METHODS

This is a single-center prospective observational study. After forward and backward translations, consensus was achieved by the expert panel on the pre-final version. Semantic equivalence of this version was assessed and necessary modifications were made accordingly to achieve the final version (P-PDQ). One hundred and fifty chronic pain patients were sub-classified into neuropathic pain (NeP (n = 82)) or non-NeP (n = 68) groups by two pain specialists. P-PDQ was then administered to 50 patients twice with an interval of 5-7 days to assess relative reliability. Chronbach's α and intraclass correlation coefficient (ICC) were calculated to evaluate internal consistency and test-retest reliability of the P-PDQ, respectively. Criterion validity was assessed as the correlation of the P-PDQ and the validated Persian version of the self-report Leeds Assessment of Neuropathic Symptoms and Signs (P-sLANSS).

RESULTS

Chronbach's α and ICC of the P-PDQ were 0.76 and 0.97, respectively. The P-PDQ scores were significantly correlated with those of P-sLANSS (ρ = 0.87, p < .01). The mean overall score of P-PDQ was significantly higher in the NeP group (p < .01) which reflects discriminant validity. Sensitivity, specificity, positive and negative predicting values and Youden index were 74.70%, 98.51%, 78.04%, 98.48%, and 0.73, respectively at the cutoff value ≤17.

CONCLUSION

The P-PDQ is a reliable and valid tool to distinguish neuropathic component in chronic pain cases.

Bibliometric Analysis of Studies on Neuropathic Pain Associated With Depression or Anxiety Published From 2000 to 2020

Objective: Neuropathic pain (NP) associated with depression or anxiety is highly prevalent in clinical practice. Publications about NP associated with depression or anxiety increased exponentially from 2000 to 2020. However, studies that applied the bibliometric method in analyzing global scientific research about NP associated with depression or anxiety are rare. This work used the bibliometric method to analyze the publications on NP associated with depression or anxiety between 2000 and 2020. Method: Publications from 2000 and 2020 were identified from the Thomson Reuters Web of Science (WoS) database. We employed CiteSpace V to conduct the bibliometric study. Results: A total of 915 articles or reviews were obtained from the WoS database. The number of publications has increased over the last two decades. The USA was the most productive among countries or regions in the field. According to the burst key words, neuroinflammation, hippocampus, safety, and modulation were the hot global research issues in the domain. Conclusion: Publications about NP associated with depression or anxiety have remarkably increased from 2000 to 2020. These historical opinions about NP associated with depression or anxiety could be an important practical basis for further research into potential development trends.

Neuropathic pain modeling: Focus on synaptic and ion channel mechanisms

Animal models of pain consist of modeling a pain-like state and measuring the consequent behavior. The first animal models of neuropathic pain (NP) were developed in rodents with a total lesion of the sciatic nerve. Later, other models targeting central or peripheral branches of nerves were developed to identify novel mechanisms that contribute to persistent pain conditions in NP. Objective assessment of pain in these different animal models represents a significant challenge for pre-clinical research. Multiple behavioral approaches are used to investigate and to validate pain phenotypes including withdrawal reflex to evoked stimuli, vocalizations, spontaneous pain, but also emotional and affective behaviors. Furthermore, animal models were very useful in investigating the mechanisms of NP. This review will focus on a detailed description of rodent models of NP and provide an overview of the assessment of the sensory and emotional components of pain. A detailed inventory will be made to examine spinal mechanisms involved in NP-induced hyperexcitability and underlying the current pharmacological approaches used in clinics with the possibility to present new avenues for future treatment. The success of pre-clinical studies in this area of research depends on the choice of the relevant model and the appropriate test based on the objectives of the study.

Bedside testing for precision pain medicine

PURPOSE OF REVIEW

In recent years, the identification of therapy responders has become an increasing focus of pain research. On the basis of laboratory quantitative sensory testing, subgroups of patients were identified, which have been shown to predict treatment response. However, the high cost and time expenditure limits the use of these lab-QST protocols in clinical practice and large clinical trials.

RECENT FINDINGS

Recently, different bedside testing protocols were developed as easy-to-use alternative for lab-QST. In addition, patients can be subgrouped based on their symptoms by use of patient-reported outcome measures. First results suggest that these approaches can be used to stratify patients into pathophysiological-plausible subgroups predictive for treatment response.

SUMMARY

This review presents recently developed bedside approaches that can be implemented as stratification tools in future clinical trials to realize individualized pain medicine. Being complementary rather than replaceable, future studies should combine questionnaires and sensory testing and apply them prospectively in large clinical trials.

Postoperative Pain Treatment With Continuous Local Anesthetic Wound Infusion in Patients With Head and Neck Cancer: A Nonrandomized Clinical Trial

Importance

Up to 80% of patients with head and neck cancer undergoing ablative surgery and neck dissection develop postoperative pain with detrimental effects on quality of life that also contributes to neuropathic and chronic postoperative pain.

Objective

To investigate the association of continuous local anesthetic wound infusion with pain management after head and neck surgery.

Design, Setting, and Participants

This prospective, longitudinal, nonrandomized clinical study carried out in a single tertiary referral center (December 1, 2015, to July 1, 2017) included 2 groups of 30 patients. Patients were consecutively enrolled and presented for ablative head and neck surgery including selective neck dissection and studied from the preoperative through the fourth postoperative day.

Interventions

The control group was treated according to a standardized escalating oral treatment protocol (ibuprofen, metamizole, opioids). The intervention group was treated with an intraoperatively applied pain catheter (InfiltraLong plus FuserPump, Pajunk, ropivacaine, 0.2%, 3 mL/h) that was removed 72 hours after operating.

Main Outcomes and Measures

Average and maximum pain intensities on a numeric rating scale; quality of life using the acute version of the validated 36-Item Short Form Survey; and neuropathic pain using the validated 12-Item painDETECT questionnaire. Consumption of opioid and nonopioid analgesics and evaluation of catheter-associated complications.

Results

During postoperative days 1 through 4, patients of the intervention group (mean [SD] age, 63.2 [13.3 years; 9 [30%] women) experienced lower mean (SD) (1.6 [1.4] vs 2.7 [1.8]; η2p = 0.09 [0.01-0.21]) and maximum (2.4 [2.2] vs 4.2 [2.0]; η2p = 0.11 [0.01-0.24]) pain intensities compared with the control group (mean [SD] age, 62.5 [13.6] years; 5 [17%] women). The intervention group also reported less neuropathic pain (mean [SD], 5.4 [3.4] vs 7.6 [5.1]; η2p = 0.09 [0.004 - 0.22]) and higher quality of life regarding vitality (56.2 [21.5] vs 43.8 [20.9], r = 0.29; 95% CI, 0.01-0.52) and pain (66.8 [27.3] vs 49.5  [27.7], r = 0.31; 95% CI, 0.04-0.54). Patients from the intervention group requested nonopioid analgesics considerably less often (n = 17 [57% ]vs n = 29 [97%]; ϕ = 0.47; 95% CI, 0.30-0.67) associated with a noticeably lower need to escalate pain treatment (n = 3 [10%] vs n = 9 [30%]; mean [SD] ibuprofen dose: 500 [173] mg vs 1133 [650] mg; r = 0.64; 95% CI, 0.02-0.91). No catheter-associated complications were observed.

Conclusions and Relevance

Continuous anesthetic wound infusion is associated with reduced postoperative pain and decreased demand for analgesics. It therefore expands the treatment options for postoperative pain in head and neck cancer.

Trial Registration

German Clinical Trials Register: DRKS00009378.

Differential response to scrambler therapy by neuropathic pain phenotypes

Scrambler therapy is a noninvasive electroanalgesia technique designed to remodulate the pain system. Despite growing evidence of its efficacy in patients with neuropathic pain, little is known about the clinical factors associated with treatment outcome. We conducted a prospective, open-label, single-arm trial to assess the efficacy and safety of scrambler therapy in patients with chronic neuropathic pain of various etiologies. A post-hoc analysis was performed to investigate whether cluster analysis of the Neuropathic Pain Symptom Inventory (NPSI) profiles could identify a subgroup of patients regarding neuropathic pain phenotype and treatment outcome. Scrambler therapy resulted in a significant decrease in the pain numerical rating scale (NRS) score over 2 weeks of treatment (least squares mean of percentage change from baseline, − 15%; 95% CI − 28% to − 2.4%; p < 0.001). The mean score of Brief Pain Inventory (BPI) interference subdimension was also significantly improved (p = 0.022), while the BPI pain composite score was not. Hierarchical clustering based on the NPSI profiles partitioned the patients into 3 clusters with distinct neuropathic pain phenotypes. Linear mixed-effects model analyses revealed differential response to scrambler therapy across clusters (p = 0.003, pain NRS; p = 0.072, BPI interference subdimension). Treatment response to scrambler therapy appears different depending on the neuropathic pain phenotypes, with more favorable outcomes in patients with preferentially paroxysmal pain rather than persistent pain. Further studies are warranted to confirm that capturing neuropathic pain phenotypes can optimize the use of scrambler therapy.

Correlation between the Neuropathic PainDETECT Screening Questionnaire and Pain Intensity in Chronic Pain Patients

Background and Objectives: Pain is a multidimensional phenomenon with a wide range regarding the location, intensity and quality. Patients with chronic pain, in particular those suffering from mixed pain, often present a special challenge. The PainDETECT questionnaire (PD-Q) is a screening instrument designed to classify whether a patient has neuropathic pain (NP), often rated as more distressing compared to nociceptive pain. The objective of this study was to investigate whether the PD-Q score correlates with pain intensity, measured with the numeric rating scale (NRS), in chronic pain patients in an outpatient setting. Materials and Methods: A questionnaire-based study was conducted to identify the associations between the unidimensional NRS scale for pain intensity and the PD-Q score for screening of an NP component in an outpatient setting. Participants were asked to fill in the questionnaire themselves. Results: One hundred seventy-six participants completed the PD-Q questionnaire and rated pain on the NRS scale at the baseline visit. The PD-Q and NRS scores significantly correlated at the baseline visit and the 1-month follow-up visit in chronic pain patients. The identification of a neuropathic component in chronic pain may permit more targeted and effective pain management. Conclusions: The findings of our questionnaire suggest that a significant proportion of chronic pain patients had manifested features of NP at the first visit to the outpatient clinic. The PD-Q is a useful screening tool to alert clinicians of NP that may need further diagnostic evaluation or therapeutic intervention and may also help to predict treatment response. Further research is needed to investigate if a correlation is predictive of treatment response when pain therapy targets NP.

Stratification of patients based on the Neuropathic Pain Symptom Inventory: development and validation of a new algorithm

ABSTRACT

The personalization of neuropathic pain treatment could be improved by identifying specific sensory phenotypes (ie, specific combinations of symptoms and signs) predictive of the response to different classes of drugs. A simple and reliable phenotyping method is required for such a strategy. We investigated the utility of an algorithm for stratifying patients into clusters corresponding to specific combinations of neuropathic symptoms assessed with the Neuropathic Pain Symptom Inventory (NPSI). Consistent with previous results, we first confirmed, in a cohort of 628 patients, the existence of a structure consisting of 3 clusters of patients characterized by higher NPSI scores for: pinpointed pain (cluster 1), evoked pain (cluster 2), or deep pain (cluster 3). From these analyses, we derived a specific algorithm for assigning each patient to one of these 3 clusters. We then assessed the clinical relevance of this algorithm for predicting treatment response, through post hoc analyses of 2 previous controlled trials of the effects of subcutaneous injections of botulinum toxin A. Each of the 97 patients with neuropathic pain included in these studies was individually allocated to one cluster, by applying the algorithm to their baseline NPSI responses. We found significant effects of botulinum toxin A relative to placebo in clusters 2 and 3, but not in cluster 1, suggesting that this approach was, indeed, relevant. Finally, we developed and performed a preliminary validation of a web-based version of the NPSI and algorithm for the stratification of patients in both research and daily practice.

Painful and non-painful diabetic neuropathy, diagnostic challenges and implications for future management

Peripheral neuropathy is one of the most common complications of both type 1 and type 2 diabetes. Up to half of patients with diabetes develop neuropathy during the course of their disease, which is accompanied by neuropathic pain in 30-40% of cases. Peripheral nerve injury in diabetes can manifest as progressive distal symmetric polyneuropathy, autonomic neuropathy, radiculo-plexopathies, and mononeuropathies. The most common diabetic neuropathy is distal symmetric polyneuropathy, which we will refer to as DN, with its characteristic glove and stocking like presentation of distal sensory or motor function loss. DN or its painful counterpart, painful DN, are associated with increased mortality and morbidity; thus, early recognition and preventive measures are essential. Nevertheless, it is not easy to diagnose DN or painful DN, particularly in patients with early and mild neuropathy, and there is currently no single established diagnostic gold standard. The most common diagnostic approach in research is a hierarchical system, which combines symptoms, signs, and a series of confirmatory tests. The general lack of long-term prospective studies has limited the evaluation of the sensitivity and specificity of new morphometric and neurophysiological techniques. Thus, the best paradigm for screening DN and painful DN both in research and in clinical practice remains uncertain. Herein, we review the diagnostic challenges from both clinical and research perspectives and their implications for managing patients with DN. There is no established DN treatment, apart from improved glycaemic control, which is more effective in type 1 than in type 2 diabetes, and only symptomatic management is available for painful DN. Currently, less than one-third of patients with painful DN derive sufficient pain relief with existing pharmacotherapies. A more precise and distinct sensory profile from patients with DN and painful DN may help identify responsive patients to one treatment versus another. Detailed sensory profiles will lead to tailored treatment for patient subgroups with painful DN by matching to novel or established DN pathomechanisms and also for improved clinical trials stratification. Large randomized clinical trials are needed to identify the interventions, i.e. pharmacological, physical, cognitive, educational, etc., which lead to the best therapeutic outcomes.

Relationship of Bladder Pain With Clinical and Urinary Markers of Neuroinflammation in Women With Urinary Urgency Without Urinary Incontinence

PURPOSE

The pathogenesis of bladder pain is poorly understood. Our hypothesis is that in women with urinary urgency without incontinence, bladder pain is associated with the presence of neurogenic inflammation in the bladder wall and neuroinflammatory biomarkers in the urine.

METHODS

We conducted a prospective cross-sectional study of women with urinary urgency without incontinence. Urinary symptoms were measured using Female Genitourinary Pain Index. Neuropathic pain, a clinical biomarker of neuroinflammation, was measured using the PainDETECT questionnaire. Inflammatory neuropeptides measured in the urine included nerve growth factor (NGF), brain-derived neurotrophic factor, vascular endothelial growth factor, and osteopontin. Neuropathic pain scores and urinary neuropeptide levels were compared between patients with and without bladder pain using univariable and multivariable analyses.

RESULTS

In 101 women with urinary urgency without incontinence, 62 (61%) were in the bladder pain group (visual analog scale score, ≤ 3), whereas 39 (39%) were in the no bladder pain group. Urinary symptom scores (5.0 ± 3.1 versus 3.5 ± 2.4, P < 0.001) and neuropathic pain scores (13.3 ± 8.6 vs 5.1 ± 4.8, P < 0.001) were significantly higher for the bladder pain group than for the no bladder pain group. On multivariable analysis after controlling for age, body mass index, and severity of urinary urgency, bladder pain score was significantly associated with elevated urinary levels of vascular endothelial growth factor (P = 0.04) and osteopontin (P = 0.02), whereas the neuropathic pain score was significantly associated with an increased NGF level (P = 0.03).

CONCLUSIONS

In women with urinary urgency without incontinence, bladder pain is associated with the presence of clinical and urinary biomarkers of neuroinflammation.

Patient phenotyping in clinical trials of chronic pain treatments: IMMPACT recommendations

There is tremendous interpatient variability in the response to analgesic therapy (even for efficacious treatments), which can be the source of great frustration in clinical practice. This has led to calls for “precision medicine” or personalized pain therapeutics (ie, empirically based algorithms that determine the optimal treatments, or treatment combinations, for individual patients) that would presumably improve both the clinical care of patients with pain and the success rates for putative analgesic drugs in phase 2 and 3 clinical trials. However, before implementing this approach, the characteristics of individual patients or subgroups of patients that increase or decrease the response to a specific treatment need to be identified. The challenge is to identify the measurable phenotypic characteristics of patients that are most predictive of individual variation in analgesic treatment outcomes, and the measurement tools that are best suited to evaluate these characteristics. In this article, we present evidence on the most promising of these phenotypic characteristics for use in future research, including psychosocial factors, symptom characteristics, sleep patterns, responses to noxious stimulation, endogenous pain-modulatory processes, and response to pharmacologic challenge. We provide evidence-based recommendations for core phenotyping domains and recommend measures of each domain.

Differential involvement of myelinated and unmyelinated nerve fibers in painful diabetic polyneuropathy

BACKGROUND

We aimed at evaluating the differential involvement of large myelinated Aβ-, small myelinated Aδ-, and unmyelinated C-fibers in patients with diabetic polyneuropathy and how they contribute to neuropathic pain.

METHODS

We collected clinical and diagnostic test variables in 133 consecutive patients with diabetic polyneuropathy. All patients underwent Aβ-fiber mediated nerve conduction study, Aδ-fiber mediated laser-evoked potentials and skin biopsy mainly assessing unmyelinated C-fibers.

RESULTS

Pure large-fiber and small-fiber polyneuropathy were relatively uncommon; conversely mixed-fiber polyneuropathy was the most common type of diabetic polyneuropathy (74%). The frequency of neuropathic pain was similar in the three different polyneuropathies. Ongoing burning pain and dynamic mechanical allodynia were similarly associated with specific small-fiber related variables.

CONCLUSIONS

Diabetic polyneuropathy mainly manifests as a mixed-fiber polyneuropathy, simultaneously involving Aβ-, Aδ-, and C-fibers. In most patients, neuropathic pain is distinctly associated with small-fiber damage. The evidence that the frequency of neuropathic pain does not differ across pure large-, pure small-, and mixed-fiber polyneuropathy, raises the possibility that in patients with pure large-fiber polyneuropathy nociceptive nerve terminal involvement might be undetected by standard diagnostic techniques.

Neuropathic Pain: From Mechanisms to Treatment

Neuropathic pain caused by a lesion or disease of the somatosensory nervous system is a common chronic pain condition with major impact on quality of life. Examples include trigeminal neuralgia, painful polyneuropathy, postherpetic neuralgia, and central poststroke pain. Most patients complain of an ongoing or intermittent spontaneous pain of, for example, burning, pricking, squeezing quality, which may be accompanied by evoked pain, particular to light touch and cold. Ectopic activity in, for example, nerve-end neuroma, compressed nerves or nerve roots, dorsal root ganglia, and the thalamus may in different conditions underlie the spontaneous pain. Evoked pain may spread to neighboring areas, and the underlying pathophysiology involves peripheral and central sensitization. Maladaptive structural changes and a number of cell-cell interactions and molecular signaling underlie the sensitization of nociceptive pathways. These include alteration in ion channels, activation of immune cells, glial-derived mediators, and epigenetic regulation. The major classes of therapeutics include drugs acting on α₂δ subunits of calcium channels, sodium channels, and descending modulatory inhibitory pathways.

Psychological factors can cause false pain classification on painDETECT

Background and aims The painDETECT questionnaire (PD-Q) has been widely used as a screening tool for the identification of neuropathic pain (NeP) as well as a tool for the characterization of patients' pain profile. In contrast to other NeP screening tools, the PD-Q is the only screening tool with weighted sensory descriptors. It is possible that responses to the PD-Q sensory descriptors are influenced by psychological factors, such as catastrophizing or anxiety, which potentially might contribute to an overall higher score of PD-Q and a false positive identification of NeP. This study aimed to explore (i) the relationship between psychological factors (catastrophizing, anxiety, depression and stress) and the total PD-Q score and (ii) if psychological factors are associated with false positive identifications of NeP on the PD-Q compared to clinically diagnosed NeP. Methods The study was a retrospective review of 1,101 patients attending an outpatient pain centre. Patients were asked to complete the PD-Q, the Pain Catastrophizing Scale (PCS), the Depression, Anxiety and Stress Scale (DASS) and the Brief Pain Inventory (BPI). For patients who were identified by PD-Q as having NeP, their medical records were reviewed to establish if they had a clinical diagnosis of NeP. Results Accounting for missing data, complete datasets of 652 patients (mean age 51 (SD14) years, range 18-88; 57% females) were available for analysis. Based on PD-Q scoring, NeP was likely present in 285 (44%) patients. Depression, anxiety, stress, catastrophizing, BPI pain and BPI interference were all significantly related to each other (p < 0.0001) and patients displaying these traits were significantly more likely to have a positive PD-Q score (p < 0.0001). For patients classified by PD-Q as having NeP, only 50% of patients had a clinical diagnosis of NeP. Anxiety was significantly associated with a false positive classification of NeP on PD-Q (p = 0.0036). Conclusions Our retrospective study showed that psychological factors including catastrophizing, depression, anxiety, and stress were all influential in producing a higher score on the PD-Q. We observed a high rate of false positive NeP classification which was associated with the presence of anxiety. Implications Clinicians and researchers should be aware that a patient's psychological state may influence the responses to PD-Q and consequently the final PD-Q score and its NeP classification.

[S2k guideline for the diagnosis and therapy of zoster and post-zoster neuralgia]

Diese Leitlinie richtet sich an Dermatologen, Ophthalmologen, HNO-Ärzte, Pädiater, Neurologen, Virologen sowie Infektiologen, Anästhesisten und Allgemeinmediziner in Klinik und Praxis und dient zur Information für andere medizinische Fachrichtungen, die an der Behandlung des Zoster beteiligt sind. Darüber hinaus soll die Leitlinie Kostenträgern und politischen Entscheidungsträgern zur Orientierung dienen. Die Leitlinie wurde im formellen Konsensusverfahren (S2k) von Dermatologen, Virologen/Infektiologen, Ophthalmologen, HNO-Ärzten, Neurologen, Pädiatern und Anästhesisten/Schmerzmedizinern erstellt.

Die Leitlinie stellt einen Überblick über die klinische und molekulare Diagnostik sowie den Antigennachweis, die Antikörperkultur und Viruskultur dar. Diagnostisch besondere Situationen und komplizierte Verläufe der Erkrankung finden ebenfalls Berücksichtigung. Die antivirale Therapie des Zoster und der Postzosterneuralgie wird im Allgemeinen und für besondere Situationen dargelegt. Detaillierte Angaben zur Schmerzbehandlung finden Erwähnung und sind in einer Übersicht dargestellt. Ebenso werden die lokaltherapeutischen Maßnahmen thematisiert.

Systematic review of the effectiveness of self-initiated interventions to decrease pain and sensory disturbances associated with peripheral neuropathy

PURPOSE

A small number of studies report that patients with peripheral neuropathy (PN) who engage in activities that promote a sense of personal well-being and provide physical, emotional, or spiritual comfort have a better quality of life and higher levels of adjustment to the changes generated by their illness and accompanying symptoms. This systematic review sought to evaluate the effectiveness of self-management activities that patients with PN initiate themselves to relieve PN symptoms and improve quality of life.

METHODS

Search terms were limited to include self-management activities initiated by patients (i.e., activities with no or minimal involvement from clinicians) that aim to provide relief of PN symptoms. Outcomes included in searches were pain, numbness, and tingling, associated with PN and quality of life.

RESULTS

The database searches identified 2979 records, of which 1620 were duplicates. A total of 1322 papers were excluded on the basis of screening the abstract. An additional 21 full text articles were excluded because they did not meet the eligibility criteria. A total of 16 papers were included in the review.

CONCLUSION

This review identified that a number of self-management strategies that were initiated by patients, including heat, exercise, meditation, and transcutaneous electrical nerve stimulation (TENS) therapy, may reduce self-reported PN symptoms. As the available studies were of low quality, these strategies warrant further investigation with more homogeneous samples, using more rigorously designed trials and larger samples.

IMPLICATIONS FOR CANCER SURVIVORS

Patients experiencing PN may find a range of self-initiated strategies beneficial in reducing PN symptoms and improving quality of life. However, because of the low quality of the available studies, clinicians need to monitor patients' responses to determine the effectiveness of these interventions as adjuncts to clinician-initiated interventions.

Molecular mechanisms of cold pain

The sensation of cooling is essential for survival. Extreme cold is a noxious stimulus that drives protective behaviour and that we thus perceive as pain. However, chronic pain patients suffering from cold allodynia paradoxically experience innocuous cooling as excruciating pain. Peripheral sensory neurons that detect decreasing temperature express numerous cold-sensitive and voltage-gated ion channels that govern their response to cooling in health and disease. In this review, we discuss how these ion channels control the sense of cooling and cold pain under physiological conditions, before focusing on the molecular mechanisms by which ion channels can trigger pathological cold pain. With the ever-rising number of patients burdened by chronic pain, we end by highlighting the pressing need to define the cells and molecules involved in cold allodynia and so identify new, rational drug targets for the analgesic treatment of cold pain.

Test-Retest and Inter-Examiner Reliability of a Novel Bedside Quantitative Sensory Testing Battery in Postherpetic Neuralgia Patients

In health and disease, the somatosensory system has been interrogated with standardized research techniques, collectively referred to as quantitative sensory testing (QST). In neuropathic pain, QST has been used to characterize multiple sensory derangements. However, the use of QST outside the lab has been limited by several factors, including a lack of standardization, variability in procedural technique, and duration of testing that would be unacceptable for clinic. To address these shortcomings, the Neuropathic Pain Research Consortium designed an easy and low-cost "bedside" QST procedure. To test the hypothesis that this procedure would be clinically reliable over time and across different examiners, a multisite, blinded study was performed in subjects with postherpetic neuralgia. Generally, agreement between 2 examiners and over 2 study visits with 1 examiner was high. Additionally, intraclass correlation coefficients and Kappa statistics calculated showed that the battery of QST tests included were highly reliable. Interestingly, mechanical modalities (light brush, pinprick, pressure, and vibration) showed the highest reliability. The least reliable modalities were cool (room temperature) and warmth (38°C). These data demonstrate that the Neuropathic Pain Research Consortium beside QST protocol is reliable across examiner and over time, providing a validated QST tool for use in clinical practice and clinical trials. PERSPECTIVE: This blinded, multicenter trial in 32 patients with postherpetic neuralgia demonstrates bedside QST is reliable and suitable as a clinical trial outcome. The novel bedside battery could be used in clinical trials or in clinical practice over time given the reliability data presented in this article.

Association between pain phenotype and disease activity in rheumatoid arthritis patients: a non-interventional, longitudinal cohort study

BACKGROUND

In well-controlled rheumatoid arthritis (RA) without significant joint damage, a substantial proportion of patients complain of persistent pain. Previous studies have identified different pain phenotypes in RA, in which non-nociceptive pain phenotypes are associated with higher concurrent disease activity scores. In this longitudinal study, we explored associations between pain phenotypes and long-term disease activity outcome in RA patients. Secondly, we explored whether pain phenotype is associated with comorbid conditions.

METHODS

One hundred eighty established RA patients were classified with a nociceptive (61%) or a non-nociceptive (39%) pain phenotype, based on their responses to the painDETECT-questionnaire. Two years of clinical follow-up data on disease activity outcomes were collected. Information on comorbid diseases was derived from electronic patient files.

RESULTS

Patients with a non-nociceptive pain phenotype showed higher mean disease activity scores (DAS28, 2.57; 95% CI, 2.37-2.77 vs. 2.11; 95% CI, 1.94-2.27; p < 0.001) and a twofold lower chance of achieving sustained DAS28 remission (OR = 0.49; 95% CI, 0.26-0.92; p = 0.020). Only the tender joint count and patient global health significantly differed between the pain phenotype groups. Patients with a non-nociceptive pain phenotype had more often been diagnosed with concurrent fibromyalgia (9.9% vs. 0.9%; p = 0.007) and other pain-associated comorbid diseases (52.1% vs. 35.8%; p = 0.030) compared with patients with a nociceptive pain phenotype.

CONCLUSION

This longitudinal study showed consistently worse long-term disease activity outcomes in RA patients with a non-nociceptive pain phenotype which appeared to be mainly due to differences in the subjective components of the disease activity score.

TRIAL REGISTRATION

The DREAM cohort study is registered in the Netherlands Trial Register: NTR578.

Visualization of Brain Activity in a Neuropathic Pain Model Using Quantitative Activity-Dependent Manganese Magnetic Resonance Imaging

Human brain imaging studies have revealed several regions that are activated in patients with chronic pain. In rodent brains, functional changes due to chronic pain have not been fully elucidated, as brain imaging techniques such as functional magnetic resonance imaging and positron emission tomography (PET) require the use of anesthesia to suppress movement. Consequently, conclusions derived from existing imaging studies in rodents may not accurately reflect brain activity under awake conditions. In this study, we used quantitative activation-induced manganese-enhanced magnetic resonance imaging to directly capture the previous brain activity of awake mice. We also observed and quantified the brain activity of the spared nerve injury (SNI) neuropathic pain model during awake conditions. SNI-operated mice exhibited a robust decrease of mechanical nociceptive threshold 14 days after nerve injury. Imaging on SNI-operated mice revealed increased neural activity in the limbic system and secondary somatosensory, sensory-motor, piriform, and insular cortex. We present the first study demonstrating a direct measurement of awake neural activity in a neuropathic pain mouse model.