Skin matters: identifying pain mechanisms and predicting treatment outcomes

Endoplasmic reticulum stress: The underlying mechanism of chronic pain

Chronic pain (CP) affects over 30 % of the global population, imposing significant financial burdens on individuals and society. However, existing treatments for CP offer limited efficacy and troublesome side effects, primarily owing to a lack of knowledge of its precise underlying mechanism. Pathological stimuli disrupt the intricate process of protein folding and endoplasmic reticulum (ER) homeostasis. This disruption leads to the accumulation of misfolded or unfolded proteins in the ER, generating a condition termed ER stress. Emerging data have indicated that ER stress, occurring in the peripheral and central nervous systems, contributes to the development and maintenance of CP. This review aimed to comprehensively explore the intersection of ER stress and CP within the lower and upper nervous systems and highlight the cell-specific contributions of the unfolded protein response in different CP types. We provide a comprehensive synthesis of evidence from animal models, examining neuronal and non-neuronal mechanisms and discuss the damaging ER stress-linked inflammation, autophagy, oxidative stress, and apoptosis, which collectively drive disease progression and contribute to a neurotoxic environment. However, the mechanisms through which ER stress influences the most advanced centre-of-pain projections in the brain remain unclear. Further investigation in this area is crucial to elucidate the relationship between ER stress and CP and facilitate the development of novel therapeutic drugs for this intractable dilemma.

Cutaneous targets for topical pain medications in patients with neuropathic pain: individual differential expression of biomarkers supports the need for personalized medicine

Introduction

Numerous potential cutaneous targets exist for treating chronic pain with topically applied active pharmaceutical ingredients. This preliminary human skin tissue investigation was undertaken to characterize several key biomarkers in keratinocytes and provide proof-of-principle data to support clinical development of topical compounded formulations for peripheral neuropathic pain syndromes, such as postherpetic neuralgia (PHN).

Objectives

The study intended to identify objective biomarkers in PHN skin on a patient-by-patient personalized medicine platform. The totality of biopsy biomarker data can provide a tissue basis for directing individualized compounded topical preparations to optimize treatment efficacy.

Methods

Referencing 5 of the most common actives used in topical pain relief formulations (ketamine, gabapentin, clonidine, baclofen, and lidocaine), and 3 well-established cutaneous mediators (ie, neuropeptides, cannabinoids, and vanilloids), comprehensive immunolabeling was used to quantify receptor biomarkers in skin biopsy samples taken from ipsilateral (pain) and contralateral (nonpain) dermatomes of patients with PHN.

Results

Epidermal keratinocyte labeling patterns were significantly different among the cohort for each biomarker, consistent with potential mechanisms of action among keratinocytes. Importantly, the total biomarker panel indicates that the enriched PHN cohort contains distinct subgroups.

Conclusion

The heterogeneity of the cohort differences may explain studies that have not shown statistical group benefit from topically administered compounded therapies. Rather, the essential need for individual tissue biomarker evaluations is evident, particularly as a means to direct a more accurately targeted topical personalized medicine approach and generate positive clinical results.

Integrative miRNA-mRNA profiling of human epidermis: unique signature of SCN9A painful neuropathy

Personalized management of neuropathic pain is an unmet clinical need due to heterogeneity of the underlying aetiologies, incompletely understood pathophysiological mechanisms and limited efficacy of existing treatments. Recent studies on microRNA in pain preclinical models have begun to yield insights into pain-related mechanisms, identifying nociception-related species differences and pinpointing potential drug candidates. With the aim of bridging the translational gap towards the clinic, we generated a human pain-related integrative miRNA and mRNA molecular profile of the epidermis, the tissue hosting small nerve fibres, in a deeply phenotyped cohort of patients with sodium channel-related painful neuropathy not responding to currently available therapies. We identified four miRNAs strongly discriminating patients from healthy individuals, confirming their effect on differentially expressed gene targets driving peripheral sensory transduction, transmission, modulation and post-transcriptional modifications, with strong effects on gene targets including NEDD4. We identified a complex epidermal miRNA-mRNA network based on tissue-specific experimental data suggesting a cross-talk between epidermal cells and axons in neuropathy pain. Using immunofluorescence assay and confocal microscopy, we observed that Nav1.7 signal intensity in keratinocytes strongly inversely correlated with NEDD4 expression that was downregulated by miR-30 family, suggesting post-transcriptional fine tuning of pain-related protein expression. Our targeted molecular profiling advances the understanding of specific neuropathic pain fine signatures and may accelerate process towards personalized medicine in patients with neuropathic pain.

Radiotherapy skin marking with lancets versus electric marking pen - Comfort, satisfaction, effectiveness and cosmesis results from the randomized, double-blind COMFORTATTOO trial

INTRODUCTION

Set-up skin markings are performed, in several centers, for radiotherapy (RT) treatments. This study aimed to compare two permanent methods: lancets and an electric marking pen, the Comfort Marker 2.0® (CM).

METHODS

This was a prospective, unicentric, randomized study. Patients aged 18 years or older referred to our department to receive RT were recruited. Patients were randomly assigned, in a 1:1 ratio, to receive set-up markings using lancets or CM. The markings arrangement followed our departmental protocols. The coprimary endpoints were patients' comfort and effectiveness. Secondary endpoints included radiation therapists (RTTs) satisfaction and cosmesis.

RESULTS

Between October 2021 and January 2022, 100 patients were enrolled (50 received lancets and 50 CM) and assessed for the comfort and satisfaction outcomes. CM was significantly less painful than the lancets, with 44% and 16% of the patients, respectively, considering the tattooing process painless (RR = 2.75; 95% IC: 1.36 - 5.58). On the RTT-reported satisfaction, CM had significantly easier processes than lancets (98.0% vs. 78.0%, respectively; RR = 1.26; 95% CI: 1.08 - 1.46). For effectiveness and cosmesis assessment, 98 patients were analyzed (48 received lancets and 50 CM). Patients receiving CM had a significantly higher proportion of markings graded as good and excellent compared to those receiving lancets (98.0% and 50.0%, respectively, had ≥75% of the tattoos assessed as good/excellent, RR = 1.96; 95% CI: 1.47 - 2.61). On the cosmetic evaluation, patients receiving CM had significantly better cosmetic markings, with a median score of 4.4 (vs. 3.5 for lancets, p <0.001).

CONCLUSION

The trial results demonstrated that tattooing with the CM is significantly less painful, more effective, easier to apply, and cosmetically superior to tattooing with lancets.

IMPLICATIONS FOR PRACTICE

Tattooing with CM allows for better results regarding pain, quality, ease and cosmesis.

Global analyses of mRNA expression in human sensory neurons reveal eIF5A as a conserved target for inflammatory pain

Nociceptors are a type of sensory neuron that are integral to most forms of pain. Targeted disruption of nociceptor sensitization affords unique opportunities to prevent pain. An emerging model for nociceptors are sensory neurons derived from human stem cells. Here, we subjected five groups to high-throughput sequencing: human induced pluripotent stem cells (hiPSCs) prior to differentiation, mature hiPSC-derived sensory neurons, mature co-cultures containing hiPSC-derived astrocytes and sensory neurons, mouse dorsal root ganglion (DRG) tissues, and mouse DRG cultures. Co-culture of nociceptors and astrocytes promotes expression of transcripts enriched in DRG tissues. Comparisons of the hiPSC models to tissue samples reveal that many key transcripts linked to pain are present. Markers indicative of a range of neuronal subtypes present in the DRG were detected in mature hiPSCs. Intriguingly, translation factors were maintained at consistently high expression levels across species and culture systems. As a proof of concept for the utility of this resource, we validated expression of eukaryotic initiation factor 5A (eIF5A) in DRG tissues and hiPSC samples. eIF5A is subject to a unique posttranslational hypusine modification required for its activity. Inhibition of hypusine biosynthesis prevented hyperalgesic priming by inflammatory mediators in vivo and diminished hiPSC activity in vitro. Collectively, our results illuminate the transcriptomes of hiPSC sensory neuron models. We provide a demonstration for this resource through our investigation of eIF5A. Our findings reveal hypusine as a potential target for inflammation associated pain in males.

Piezo2 mechanosensitive ion channel is located to sensory neurons and nonneuronal cells in rat peripheral sensory pathway: implications in pain

ABSTRACT

Piezo2 mechanotransduction channel is a crucial mediator of sensory neurons for sensing and transducing touch, vibration, and proprioception. We here characterized Piezo2 expression and cell specificity in rat peripheral sensory pathway using a validated Piezo2 antibody. Immunohistochemistry using this antibody revealed Piezo2 expression in pan primary sensory neurons of dorsal root ganglia in naïve rats, which was actively transported along afferent axons to both central presynaptic terminals innervating the spinal dorsal horn (DH) and peripheral afferent terminals in the skin. Piezo2 immunoreactivity (IR) was also detected in the postsynaptic neurons of the DH and in the motor neurons of the ventral horn, but not in spinal glial fibrillary acidic protein-positive and Iba1-positive glia. Notably, Piezo2-IR was clearly identified in peripheral nonneuronal cells, including perineuronal glia, Schwann cells in the sciatic nerve and surrounding cutaneous afferent endings, as well as in skin epidermal Merkel cells and melanocytes. Immunoblots showed increased Piezo2 in dorsal root ganglia ipsilateral to plantar injection of complete Freund's adjuvant, and immunostaining revealed increased Piezo2-IR intensity in the DH ipsilateral to complete Freund's adjuvant injection. This elevation of DH Piezo2-IR was also evident in various neuropathic pain models and monosodium iodoacetate knee osteoarthritis pain model, compared with controls. We conclude that (1) the pan neuronal profile of Piezo2 expression suggests that Piezo2 may function extend beyond simply touch or proprioception mediated by large-sized low-threshold mechanosensitive primary sensory neurons; (2) Piezo2 may have functional roles involving sensory processing in the spinal cord, Schwann cells, and skin melanocytes; and (3) aberrant Piezo2 expression may contribute pain pathogenesis.

Cutaneous innervation in impaired diabetic wound healing

Type 2 diabetes is associated with several potential comorbidities, among them impaired wound healing, chronic ulcerations, and the requirement for lower extremity amputation. Disease-associated abnormal cellular responses, infection, immunological and microvascular dysfunction, and peripheral neuropathy are implicated in the pathogenesis of the wound healing impairment and the diabetic foot ulcer. The skin houses a dense network of sensory nerve afferents and nerve-derived modulators, which communicate with epidermal keratinocytes and dermal fibroblasts bidirectionally to effect normal wound healing after trauma. However, the mechanisms through which cutaneous innervation modulates wound healing are poorly understood, especially in humans. Better understanding of these mechanisms may provide the basis for targeted treatments for chronic diabetic wounds. This review provides an overview of wound healing pathophysiology with a focus on neural involvement in normal and diabetic wound healing, as well as future therapeutic perspectives to address the unmet needs of diabetic patients with chronic wounds.

Topical Treatments and Their Molecular/Cellular Mechanisms in Patients with Peripheral Neuropathic Pain-Narrative Review

Neuropathic pain in humans results from an injury or disease of the somatosensory nervous system at the peripheral or central level. Despite the considerable progress in pain management methods made to date, peripheral neuropathic pain significantly impacts patients' quality of life, as pharmacological and non-pharmacological methods often fail or induce side effects. Topical treatments are gaining popularity in the management of peripheral neuropathic pain, due to excellent safety profiles and preferences. Moreover, topical treatments applied locally may target the underlying mechanisms of peripheral sensitization and pain. Recent studies showed that peripheral sensitization results from interactions between neuronal and non-neuronal cells, with numerous signaling molecules and molecular/cellular targets involved. This narrative review discusses the molecular/cellular mechanisms of drugs available in topical formulations utilized in clinical practice and their effectiveness in clinical studies in patients with peripheral neuropathic pain. We searched PubMed for papers published from 1 January 1995 to 30 November 2020. The key search phrases for identifying potentially relevant articles were "topical AND pain", "topical AND neuropathic", "topical AND treatment", "topical AND mechanism", "peripheral neuropathic", and "mechanism". The result of our search was 23 randomized controlled trials (RCT), 9 open-label studies, 16 retrospective studies, 20 case (series) reports, 8 systematic reviews, 66 narrative reviews, and 140 experimental studies. The data from preclinical studies revealed that active compounds of topical treatments exert multiple mechanisms of action, directly or indirectly modulating ion channels, receptors, proteins, and enzymes expressed by neuronal and non-neuronal cells, and thus contributing to antinociception. However, which mechanisms and the extent to which the mechanisms contribute to pain relief observed in humans remain unclear. The evidence from RCTs and reviews supports 5% lidocaine patches, 8% capsaicin patches, and botulinum toxin A injections as effective treatments in patients with peripheral neuropathic pain. In turn, single RCTs support evidence of doxepin, funapide, diclofenac, baclofen, clonidine, loperamide, and cannabidiol in neuropathic pain states. Topical administration of phenytoin, ambroxol, and prazosin is supported by observational clinical studies. For topical amitriptyline, menthol, and gabapentin, evidence comes from case reports and case series. For topical ketamine and baclofen, data supporting their effectiveness are provided by both single RCTs and case series. The discussed data from clinical studies and observations support the usefulness of topical treatments in neuropathic pain management. This review may help clinicians in making decisions regarding whether and which topical treatment may be a beneficial option, particularly in frail patients not tolerating systemic pharmacotherapy.

Peripheral Mechanisms of Neuropathic Pain-the Role of Neuronal and Non-Neuronal Interactions and Their Implications for Topical Treatment of Neuropathic Pain

Neuropathic pain in humans arises as a consequence of injury or disease of somatosensory nervous system at peripheral or central level. Peripheral neuropathic pain is more common than central neuropathic pain, and is supposed to result from peripheral mechanisms, following nerve injury. The animal models of neuropathic pain show extensive functional and structural changes occurring in neuronal and non-neuronal cells in response to peripheral nerve injury. These pathological changes following damage lead to peripheral sensitization development, and subsequently to central sensitization initiation with spinal and supraspinal mechanism involved. The aim of this narrative review paper is to discuss the mechanisms engaged in peripheral neuropathic pain generation and maintenance, with special focus on the role of glial, immune, and epithelial cells in peripheral nociception. Based on the preclinical and clinical studies, interactions between neuronal and non-neuronal cells have been described, pointing out at the molecular/cellular underlying mechanisms of neuropathic pain, which might be potentially targeted by topical treatments in clinical practice. The modulation of the complex neuro-immuno-cutaneous interactions in the periphery represents a strategy for the development of new topical analgesics and their utilization in clinical settings.

Brachial Plexus Injuries in Sport Medicine: Clinical Evaluation, Diagnostic Approaches, Treatment Options, and Rehabilitative Interventions

The brachial plexus represents a complex anatomical structure in the upper limb. This "network" of peripheral nerves permits the rearrangement of motor efferent fibers, coming from different spinal nerves, in several terminal branches directed to upper limb muscles. Moreover, afferent information coming from different cutaneous regions in upper limb are sorted in different spinal nerves through the brachial plexus. Severe brachial plexus injuries are a rare clinical condition in the general population and in sport medicine, but with dramatic consequences on the motor and sensory functions of the upper limb. In some sports, like martial arts, milder injuries of the brachial plexus can occur, with transient symptoms and with a full recovery. Clinical evaluation represents the cornerstone in the assessment of the athletes with brachial plexus injuries. Electrodiagnostic studies and imaging techniques, like magnetic resonance and high-frequency ultrasound, could be useful to localize the lesion and to define an appropriate treatment and a functional prognosis. Several conservative and surgical techniques could be applied, and multidisciplinary rehabilitative programs could be performed to guide the athlete toward the recovery of the highest functional level, according to the type of injury.

Compounded Topical Amitriptyline for Neuropathic Pain: In Vitro Release from Compounding Bases and Potential Correlation with Clinical Efficacy

BACKGROUND

Topical amitriptyline has been described as having mixed clinical efficacy for neuropathic pain. A few case reports using higher concentrations of this compound found clinical benefit, but many of these studies did not describe the components used in formulating the amitriptyline preparations.

OBJECTIVE

To generate reproducible clinical measures of the characteristics of amitriptyline diffusion from selected compounding bases, to support a scientific approach to base selection when compounding this drug for neuropathic pain.

METHODS

Amitriptyline hydrochloride (1%, 5%, and 10%) was compounded with 3 proprietary compounding bases: Lipoderm base, Emollient Cream, and Mediflo 30 pluronic lecithin organogel (PLO) gel. In vitro release of the drug from each base and subsequent permeation across artificial human skin were investigated with the Franz diffusion system. Amitriptyline release mechanisms were determined with kinetic models. How quickly and to what extent the drug leaves each base to diffuse through the skin were characterized by determining steady-state flux, cumulative permeation, and lag times.

RESULTS

Release of amitriptyline was significantly higher from the Mediflo PLO gel than from the Lipoderm base or Emollient Cream (p < 0.05). Mean cumulative drug release after 24 h, from the 10% formulation, was 23.9% (standard deviation [SD] 4.1%) for Lipoderm base, 41.8% (SD 3.1%) for Emollient Cream, and 53.2% (SD 7.7%) for Mediflo PLO gel. A high percentage of amitriptyline was retained in all 3 bases. Although amitriptyline release was highest with Mediflo PLO gel, this base resulted in significantly lower cumulative permeation relative to Lipoderm base and Emollient Cream (p < 0.05). There was a strong overall correlation between amitriptyline concentration, lag time, and flux. Higher concentrations were associated with significantly lower lag times and increased flux. The highest lag time and flux were observed for Mediflo PLO gel.

CONCLUSION

These data indicate that the therapeutic effectiveness of compounded amitriptyline for neuropathic pain depends on its diffusion out of the compounding bases and penetration through the skin.

Cross cultural adaptation and refinement of an English version of a Dutch patient-reported questionnaire for hand sensitivity: The Radboud Evaluation of Sensitivity

STUDY DESIGN

Longitudinal clinical measurement.

INTRODUCTION

Sensory alterations in the hand can present as both decreased sensation or numbness, and hyperesthesia, including mechanical allodynia and cold intolerance. However, few patient-reported outcomes have been developed and validated for evaluation, particularly for increased sensitivity. The Radboud Evaluation of Sensitivity was developed in the Netherlands for patient-reported evaluation of hand sensitivity in complex regional pain syndrome.

PURPOSE OF THE STUDY

The purpose of this study was to translate into English and culturally validate the Radboud Evaluation of Sensitivity for the North American context.

METHODS

Forward and backward translation, followed by a psychometric evaluation of the synthesized version of the translated tool, was undertaken in a heterogeneous group of persons after hand injury, including nerve injuries, hand trauma, and complex regional pain syndrome.

RESULTS

Thirty-six persons completed test-retest reliability testing, yielding an intraclass correlation coefficient of 0.92 (95% CI 0.85 to 0.96) for single measures. Internal consistency was also high at α = 0.96 in a larger sample (n = 56). Although some support for construct validity was generated, several validity hypotheses were not confirmed. Of interest, there appeared to be significant differences in the scores between persons with hypoesthesia as compared with those with hyperesthesia.

CONCLUSIONS

The Radboud Evaluation of Sensitivity, English version appears to be a reliable tool for the self-reported evaluation of sensory alterations in the hand, including both hypoesthesia and hyperesthesia. More research is needed to add to the extent of and confidence in the validity and responsiveness of this assessment.

LEVEL OF EVIDENCE

Level II.

Somatosensory rehabilitation for allodynia in complex regional pain syndrome of the upper limb: A retrospective cohort study

STUDY DESIGN

Retrospective cohort study.

INTRODUCTION

Somatosensory rehabilitation is a standardized method of evaluation and conservative treatment of painful disorders of vibrotactile sensation, including the mechanical allodynia and burning pain of complex regional pain syndrome (CRPS).

PURPOSE OF THE STUDY

The purpose of this study was to examine the effectiveness of somatosensory rehabilitation for reducing allodynia in persons with CRPS of 1 upper limb in a retrospective consecutive cohort of patients.

METHODS

An independent chart review of all client records (May 2004-August 2015) in the Somatosensory Rehabilitation Centre (Fribourg, Switzerland) identified 48 persons meeting the Budapest criteria for CRPS of 1 limb who had undergone assessment and treatment. Outcomes of interest were the French version of the McGill Pain Questionnaire (Questionnaire de la Douleur St-Antoine [QDSA]), total area of allodynia as recorded by mapping the area of skin where a 15-g monofilament was perceived as painful, and the allodynia threshold (minimum pressure required to elicit pain within the allodynic territory).

RESULTS

This cohort was primarily women (70%), with a mean age of 45 years (range: 18-74). Mean duration of burning pain was 31 months (range: 1 week-27.5 years), and baseline QDSA core was 48. The average primary area of allodynia was 66 cm² (range: 2.6-320), and the most common allodynia threshold was 4.0 g. The average duration of treatment was 81 days. At cessation of treatment, the average QDSA score was 20 (effect size Cohen's d = 1.64). Allodynia completely resolved in 27 persons (56% of the total sample where only 58% completed treatment).

DISCUSSION

This uncontrolled retrospective study suggests that somatosensory rehabilitation may be an effective treatment with a large effect size for reducing the allodynia and painful sensations associated with CRPS of the upper limb. More work is in progress to provide estimates of reliability and validity for the measurement tools for allodynia employed by this method.

LEVEL OF EVIDENCE

2c.

PIEZO1 Is Selectively Expressed in Small Diameter Mouse DRG Neurons Distinct From Neurons Strongly Expressing TRPV1

Using a high resolution in situ hybridization technique we have measured PIEZO1, PIEZO2, and TRPV1 transcripts in mouse dorsal root ganglion (DRG) neurons. Consistent with previous studies, PIEZO2 transcripts were highly expressed in DRG neurons of all sizes, including most notably the largest diameter neurons implicated in mediating touch and proprioception. In contrast, PIEZO1 transcripts were selectively expressed in smaller DRG neurons, which are implicated in mediating nociception. Moreover, the small neurons expressing PIEZO1 were mostly distinct from those neurons that strongly expressed TRPV1, one of the channels implicated in heat-nociception. Interestingly, while PIEZO1- and TRPV1- expressing neurons form essentially non-overlapping populations, PIEZO2 showed co-expression in both populations. Using an in vivo functional test for the selective expression, we found that Yoda1, a PIEZO1-specific agonist, induced a mechanical hyperalgesia that displayed a significantly prolonged time course compared with that induced by capsaicin, a TRPV1-specific agonist. Taken together, our results indicate that PIEZO1 should be considered a potential candidate in forming the long sought channel mediating mechano-nociception.

Content validation of the Patient-Reported Hamilton Inventory for Complex Regional Pain Syndrome: Validité de contenu du Hamilton Inventory for Complex Regional Pain Syndrome, une mesure des résultats déclarés par le patient

BACKGROUND

Complex regional pain syndrome (CRPS) is a perplexing neurological condition, and persons with CRPS experience substantial loss of daily roles and activities. A condition-specific measure is being developed to evaluate CRPS.

PURPOSE

We describe the use of cognitive interviews to examine content validity of this patient-reported outcome measure for CRPS.

METHOD

Interviews with 44 persons with CRPS were analyzed to identify problems with wording and support content validation. Item-total correlations were calculated for proposed subscales, and scores were plotted to consider floor/ceiling effects.

FINDINGS

Interviews identified questions where respondents considered factors unrelated to the construct of interest or were underaddressed by the questionnaire, including depression and skin temperature. The symptoms, daily function, and coping/social impact scales demonstrated satisfactory correlations (Cronbach's alpha 0.76-0.86). Despite a sampling bias of severity, no frank floor/ceiling effects were noted.

IMPLICATIONS

This study builds a foundation for continuing development and evaluation of the measurement properties of the Patient-Reported Hamilton Inventory for CRPS. It makes explicit the iterative decisions involved in rigorous instrument development.

Skin matters! The role of keratinocytes in nociception: a rational argument for the development of topical analgesics

Treatment of neuropathic pain using topical formulations is still in its infancy. Only few topical analgesic formulations have become available for clinical use, and among these, analgesic creams are still rare. This is unfortunate because analgesic creams offer a number of advantages over patches, such as convenience, ease of adapting the frequency of application, and dose, and “rubbing cream where it hurts” involves the patient much more in the therapeutic process compared to patches and other localized treatment modalities. Although the literature supporting the efficacy and safety of analgesic creams (mostly compounded) is growing since the last decade, most pain physicians have not yet noticed and appreciated the therapeutic potential and clinical value of these creams. This is most probably due to a prejudice that topical application should need to act transdermally, more or less as a slow-release formulation, such as in patches delivering opioids. We will discuss this prejudice and show that there are multiple important targets in the skin to be reached by topical analgesic or anti-inflammatory compounds, and that the keratinocyte is one of those targets. By specifically targeting the keratinocyte, analgesia seems possible, effective, and safe, and thus topical analgesic creams may hold promise as a novel treatment modality for neuropathic pain.

New topical treatment of vulvodynia based on the pathogenetic role of cross talk between nociceptors, immunocompetent cells, and epithelial cells

Topical treatments of localized neuropathic pain syndromes in general are mostly neglected, mainly due to the fact that most pain physicians expect that a topical formulation needs to result in a transdermal delivery of the active compounds. On the basis of the practical experience, this study brings forth a new, somewhat neglected element of the vulvodynia pathogenesis: the cross talk between the nerve endings of nociceptors, the adjacent immunocompetent cells, and vaginal epithelial cells. Insight into this cross talk during a pathogenic condition supports the treatment of vulvodynia with topical (compounded) creams. Vulvodynia was successfully treated with an analgesic cream consisting of baclofen 5% together with the autacoid palmitoylethanolamide 1%, an endogenous anti-inflammatory compound. In this review, data is presented to substantiate the rationale behind developing and prescribing topical products for localized pain states such as vulvodynia. Most chronic inflammatory disorders are based on a network pathogenesis, and monotherapeutic inroads into the treatment of such disorders are obsolete.

Pain in cancer survivors

Cancer and its treatment exert a heavy psychological and physical toll. Of the myriad symptoms which result, pain is common, encountered in between 30% and 60% of cancer survivors. Pain in cancer survivors is a major and growing problem, impeding the recovery and rehabilitation of patients who have beaten cancer and negatively impacting on cancer patients' quality of life, work prospects and mental health. Persistent pain in cancer survivors remains challenging to treat successfully. Pain can arise both due to the underlying disease and the various treatments the patient has been subjected to. Chemotherapy causes painful chemotherapy-induced peripheral neuropathy (CIPN), radiotherapy can produce late effect radiation toxicity and surgery may lead to the development of persistent post-surgical pain syndromes. This review explores a selection of the common causes of persistent pain in cancer survivors, detailing our current understanding of the pathophysiology and outlining both the clinical manifestations of individual pain states and the treatment options available.

Pressure pain threshold of the cervico-facial muscles in healthy elderly people: the role of gender, age and dominance

OBJECTIVE

The aim of this study was to assess the impact of age on pressure pain threshold (PPT) of cervico-facial muscles in healthy geriatric subjects and to investigate the role of gender and dominance on nociception.

BACKGROUND

Musculo-skeletal pain is common in the elderly, but being subjective, it risks to be underdiagnosed and undertreated. A useful method for assessment of local pain is determining PPT through pressure algometry. Ageing process seems to increase PPTs, but reference values for the assessment of pain in geriatric subjects are lacking.

METHODS

In this study, PPTs in temporal muscle, masseter, sternocleidomastoid, occipital and splenius capitis of 97 healthy elderly subjects were measured using Fischer algometer. Participants were divided by age in four classes (years 65-69; 70-74; 75-79; ≥80).

RESULTS

Women had lower PPTs in all muscles compared with men. Comparing PPTs obtained from the right and the left side, no significant differences were recorded neither in men nor in women. When dividing subjects by age class and education, in both genders no significant differences were observed in PPTs among the groups, neither in the right nor in the left sides.

CONCLUSION

In conclusion, the present study reports reference PPT values for the cervico-facial muscles that can be applied to a population of healthy elderly subjects. After 65 years of age, further ageing does not influence PPTs in cervico-facial muscles whereas female gender has lower PPTs.