Post-herpetic Neuralgia: a Review

Public health impact of herpes zoster vaccination on older adults in Singapore: a modeling study

In Singapore, population aging and rising life expectancy are increasing herpes zoster (HZ) burden, which may be reduced by vaccination. The present study modeled the public health impact of HZ vaccination in Singapore using ZOster ecoNomic Analysis (ZONA) model adapted with Singapore-specific key model inputs, where available. Base case analysis was conducted in adults ≥ 50 years of age (YOA), exploring three vaccination strategies (no vaccination, recombinant zoster vaccine [RZV], zoster vaccine live [ZVL]) under mass vaccination setting (30% coverage). Scenario and sensitivity analyses were performed. Out of 1.51 million adults in 2021 (base case population), 406,513 (27.0%) cases of HZ, 68,264 (4.5%) cases of post-herpetic neuralgia (PHN), and 54,949 (3.6%) cases of other complications were projected without vaccination. RZV was estimated to avoid 73,129 cases of HZ, 11,094 cases of PHN, and 9,205 cases of other complications over the subjects' remaining lifetime; ZVL would avoid 17,565 cases of HZ, 2,781 cases of PHN, and 1,834 cases of other complications. The number needed to vaccinate to prevent one case of HZ/PHN was lower for RZV (7/41) than ZVL (26/163). Among all five age-stratified cohorts (50-59/60-64/65-69/70-79/≥80 YOA), RZV (versus no vaccination/ZVL) avoided the largest number of cases in the youngest cohort, 50-59 YOA. Results were robust under scenario and sensitivity analyses. Mass vaccination with RZV is expected to greatly reduce the public health burden of HZ among Singapore individuals ≥ 50 YOA. Findings support value assessment and decision-making regarding public health vaccination strategies for HZ prevention in Singapore.

Clinical Predictors of Medication Compliance in Patients With Acute Herpetic Neuralgia

PURPOSE

Pain is one of the most common and harmful symptoms experienced by individuals with acute herpetic neuralgia (AHN). In this population, studies to determine the causes that affect patients taking medications compliance are rare. This study aimed to construct a predictive model for medication compliance of patients with AHN and to verify its performance.

DESIGN AND METHODS

In this prospective study of 398 patients with AHN who were discharged from a tertiary hospital with medications from July 2020 to October 2022, we used logistic regression analysis to explore the predictive factors of medication compliance of patients with AHN and to construct a nomogram. The area under the curve was used to evaluate the predictive effect of the model.

RESULTS

A predictive model of drug compliance of patients with AHN was constructed based on the following four factors: disease duration, pain severity before treatment, medication beliefs, and comorbidity of chronic diseases. The area under the curve of the model was 0.766 (95% confidence interval [0.713, 0.819]), with a maximum Youden's index of 0.431, sensitivity of 0.776, and specificity of 0.655. A linear calibration curve was found with a slope close to 1.

CONCLUSIONS

The prediction model constructed in this study had good predictive performance and provided a reference for early clinical screening of independent factors that affected the medication compliance of patients with AHN.

Herpes zoster in neuro-ophthalmology: a practical approach

Herpes Zoster (HZ) or shingles is the reactivation of the Varicella Zoster Virus (VZV), usually along a single sensory nerve, but can affect both sensory and motor cranial nerves. Major risk factors for HZ include immunosuppressed status and age older than 60 years. In the United States, the lifetime risk of HZ is approximately 30%. Worldwide, the median incidence of HZ is 4-4.5 per 1000 person-years across the Americas, Eurasia, and Australia. HZ ophthalmicus, occurring in 10-20% of patients, is an ophthalmic emergency characterized by VZV reactivation along the V1 branch of the trigeminal nerve. Approximately half of this patient subgroup will go on to develop ocular manifestations, requiring prompt diagnosis and management. While anterior segment complications are more common, neuro-ophthalmic manifestations are rarer and can also occur outside the context of overt HZ ophthalmicus. Neuro-ophthalmic manifestations include optic neuropathy, acute retinal necrosis or progressive outer retinal necrosis, cranial neuropathy (isolated or multiple), orbitopathy, and CNS manifestations. Although typically a clinical diagnosis, diagnosis may be aided by neuroimaging and laboratory (e.g., PCR and serology) studies. Early antiviral therapy is indicated as soon as a presumptive diagnosis of VZV is made and the role of corticosteroids remains debated. Generally, there is wide variation of prognosis with neuro-ophthalmic involvement. Vaccine-mediated prevention is recommended. In this review, we summarize neuro-ophthalmic manifestations of VZV.

Increased Risk of Herpes Zoster Infection in Patients with Celiac Disease 50 Years Old and Older

BACKGROUND

Celiac Disease (CD) is associated with increased susceptibility to certain bacterial and viral infections. Herpes zoster (HZ) is a viral infection that can be prevented by immunization. In the US, the vaccine is recommended for adults ≥ 50 or ≥ 19 with certain at-risk conditions, not including CD.

AIMS

We aimed to determine if adult patients aged < 50 or ≥ 50 years with CD had a higher risk of developing HZ.

METHODS

We designed a retrospective cohort study. CD was defined as patients with the ICD-10 code for CD and positive Celiac serology. Patients with negative serology and lacking CD ICD-10 codes served as controls. Patients who had HZ before CD diagnosis were excluded. We formed two sub-cohorts, those aged < 50 (cohort 1) and aged ≥ 50 years (cohort 2), and evaluated HZ infection at 10-year follow-up. To account for confounding variables, we performed 1:1 propensity score matching (PSM).

RESULTS

Following PSM, cohort 1 had 6,826 CD patients, and cohort 2 had 5,337 CD patients and respective matched controls. After ten years of follow-up, in cohort 1, 62 CD patients developed HZ versus 57 controls, RR: 1.09 (CI: 0.76-1.56, p-value = 0.64). In cohort 2, 200 CD patients developed HZ versus 159 controls, RR: 1.2 (CI: 1.02-1.54, p-value = 0.03).

CONCLUSION

There was no significant difference in the likelihood of getting HZ in CD patients < 50, although CD patients ≥ 50 had a modestly increased risk. Our findings do not support routine early vaccination for HZ in CD, and the vaccine should be offered at age 50.

Post-Viral Pain, Fatigue, and Sleep Disturbance Syndromes: Current Knowledge and Future Directions

Background

Post-viral pain syndrome, also known as post-viral syndrome, is a complex condition characterized by persistent pain, fatigue, musculoskeletal pain, neuropathic pain, neurocognitive difficulties, and sleep disturbances that can occur after an individual has recovered from a viral infection.

Aims

This narrative review provides a summary of the sequelae of post-viral syndromes, viral agents that cause it, and the pathophysiology, treatment, and future considerations for research and targeted therapies.

Methods

Medline, PubMed, and Embase databases were used to search for studies on viruses associated with post-viral syndrome.

Conclusion

Much remains unknown regarding the pathophysiology of post-viral syndromes, and few studies have provided a comprehensive summary of the condition, agents that cause it, and successful treatment modalities. With the COVID-19 pandemic continuing to affect millions of people worldwide, the need for an understanding of the etiology of post-viral illness and how to help individuals cope with the sequalae is paramount.

Gabapentin alleviated the cough hypersensitivity and neurogenic inflammation in a guinea pig model with repeated intra-esophageal acid perfusion

OBJECTIVE

The anti-tussive effect of gabapentin and its underlying neuromodulatory mechanism were investigated via a modified guinea pig model of gastroesophageal reflux-related cough (GERC).

METHODS

Intra-esophageal perfusion with hydrochloric acid (HCl) was performed every other day 12 times to establish the GERC model. High-dose gabapentin (48 mg/kg), low-dose gabapentin (8 mg/kg), or saline was orally administered for 2 weeks after modeling. Cough sensitivity, airway inflammation, lung and esophagus histology, levels of substance P (SP), and neurokinin-1 (NK1)-receptors were monitored.

RESULTS

Repeated intra-esophageal acid perfusion aggravated the cough sensitivity in guinea pigs in a time-dependent manner. The number of cough events was significantly increased after 12 times HCl perfusion, and the hypersensitivity period was maintained for 2 weeks. The SP levels in BALF, trachea, lung, distal esophagus, and vagal ganglia were increased in guinea pigs receiving HCl perfusion. The intensity of cough hypersensitivity in the GERC model was significantly correlated with increased SP expression in the airways. Both high and low doses of gabapentin administration could reduce cough hypersensitivity exposed to HCl perfusion, attenuate airway inflammatory damage, and inhibit neurogenic inflammation by reducing SP expression from the airway and vagal ganglia.

CONCLUSIONS

Gabapentin can desensitize the cough sensitivity in the GERC model of guinea pig. The anti-tussive effect is associated with the alleviated peripheral neurogenic inflammation as reflected in the decreased level of SP.

Neuropathic Pain in the Emergency Setting: Diagnosis and Management

Neuropathic pain, traditionally considered a chronic condition, is increasingly encountered in the emergency department (ED), accounting for approximately 20% of patients presenting with pain. Understanding the physiology and key clinical presentations of neuropathic pain is crucial for ED physicians to provide optimal treatment. While diagnosing neuropathic pain can be challenging, emphasis should be placed on obtaining a comprehensive medical history and conducting a thorough clinical examination. Patients often describe neuropathic pain as a burning or shock-like sensation, leading them to seek care in the ED after ineffective relief from common analgesics such as paracetamol and NSAIDs. Collaboration between emergency medicine specialists, neurologists, and pain management experts can contribute to the development of evidence-based guidelines specifically tailored for the emergency department setting. This article provides a concise overview of the common clinical manifestations of neuropathic pain that may prompt patients to seek emergency care.

Therapeutic Strategies for Postherpetic Neuralgia: Mechanisms, Treatments, and Perspectives

PURPOSE OF REVIEW

Postherpetic neuralgia is an annoying pain that mainly affects older people. In order to give patients more options, this review summarizes the pharmacological and interventional treatments for postherpetic neuralgia and updates the research on the efficacy, thereby providing doctors with more treatment options. The adverse effects and effective doses of its various treatments are also presented so that the therapy can be prescribed according to their concrete physical conditions. In a word, this review is dedicated to providing a comprehensive overview of the treatment options for postherpetic neuralgia and offering patients more choices.

RECENT FINDINGS

Combinational therapy is more excellent than monotherapy. The local anesthesia and gabapentin comprised outstanding compatibility. In addition, two therapeutic tools for PHN patients, especially for the intractable ones, electroacupuncture (EA), and osteopathic manipulative treatment (OMT), show their efficacy and become potential options to alleviate pain. In terms of treatment, guidelines recommend patients use tricyclic antidepressants (TCAs), gabapentin, pregabalin, and 5% lidocaine patches as the first-line medications, and gabapentin is investigated most, especially the gabapentin enacarbil (GEn). And drug efficacy can be limited by adverse effects and tolerated doses. Interventional treatments, with their invasiveness and operational difficulty, are usually considered for intractable patients. Combinational therapies may be used when a single therapy cannot achieve the desired effect. Therapies such as OMT and EA have also been proposed to palliate pain in some cases, and future directions of treatment may be investigated in Chinese medicine and acupuncture.

Pharmacological Management of Orofacial Pain

Orofacial pain is a category of complex disorders, including musculoskeletal, neuropathic and neurovascular disorders, that greatly affect the quality of life of the patient. These disorders are within the fields of dentistry and medicine and management can be challenging, requiring a referral to an orofacial pain specialist, essential for adequate evaluation, diagnosis, and care. Management is specific to the diagnosis and a treatment plan is developed with diverse pharmacological and non-pharmacological modalities. The pharmacological management of orofacial pain encompasses a vast array of medication classes and approaches. This includes anti-inflammatory drugs, muscle relaxants, anticonvulsants, antidepressants, and anesthetics. In addition, as adjunct therapy, different injections can be integrated into the management plan depending on the diagnosis and needs. These include trigger point injections, temporomandibular joint (TMJ) injections, and neurotoxin injections with botulinum toxin and nerve blocks. Multidisciplinary management is key for optimal care. New and safer therapeutic targets exclusively for the management of orofacial pain disorders are needed to offer better care for this patient population.

Peripheral Nerve Stimulation of the Lesser Occipital and Greater Auricular Nerve for Post Herpetic Neuralgia in a Case of Ramsay Hunt Syndrome: Case Report

Background

Post-herpetic neuralgia (PHN) is a painful condition that presents after herpes zoster reactivation in the peripheral and central nervous system. When medical treatment fails, options are limited, and patients may suffer with chronic pain indefinitely.

Case Presentation

We present the case of a gentleman with a 3-year history of PHN in the distribution of the right lesser occipital and greater auricular nerves that failed to respond to medical treatment. He underwent a trial of neuromodulation, and post-operative pain scores improved by 80%, and at 60 days post-operatively his average pain score was 0 out of 10.

Conclusions

PNS is an effective and safe option for the treatment of chronic pain, and we present a report of successful treatment of PHN in a particularly difficult anatomic distribution. PNS of the lesser occipital and greater auricular nerves is a novel treatment for PHN and shows promise as an effective, safe therapy when other treatment fails.

Investigational Drugs for the Treatment of Postherpetic Neuralgia: Systematic Review of Randomized Controlled Trials

The pharmacological treatment of postherpetic neuralgia (PHN) is unsatisfactory, and there is a clinical need for new approaches. Several drugs under advanced clinical development are addressed in this review. A systematic literature search was conducted in three electronic databases (Medline, Web of Science, Scopus) and in the ClinicalTrials.gov register from 1 January 2016 to 1 June 2023 to identify Phase II, III and IV clinical trials evaluating drugs for the treatment of PHN. A total of 18 clinical trials were selected evaluating 15 molecules with pharmacological actions on nine different molecular targets: Angiotensin Type 2 Receptor (AT2R) antagonism (olodanrigan), Voltage-Gated Calcium Channel (VGCC) α2δ subunit inhibition (crisugabalin, mirogabalin and pregabalin), Voltage-Gated Sodium Channel (VGSC) blockade (funapide and lidocaine), Cyclooxygenase-1 (COX-1) inhibition (TRK-700), Adaptor-Associated Kinase 1 (AAK1) inhibition (LX9211), Lanthionine Synthetase C-Like Protein (LANCL) activation (LAT8881), N-Methyl-D-Aspartate (NMDA) receptor antagonism (esketamine), mu opioid receptor agonism (tramadol, oxycodone and hydromorphone) and Nerve Growth Factor (NGF) inhibition (fulranumab). In brief, there are several drugs in advanced clinical development for treating PHN with some of them reporting promising results. AT2R antagonism, AAK1 inhibition, LANCL activation and NGF inhibition are considered first-in-class analgesics. Hopefully, these trials will result in a better clinical management of PHN.

Global Prevalence of Chronic Pain in Women with HIV: A Systematic Review and Meta-analysis

Chronic pain is common among people with human immunodeficiency virus (HIV) and detrimental to quality of life and overall health. It is often underdiagnosed, undertreated, and frankly dismissed in women with HIV, despite growing evidence that it is highly prevalent in this population. Thus, we conducted a systematic review and meta-analysis to estimate the global prevalence of chronic pain in women with HIV. The full protocol can be found on PROSPERO (identifier CRD42022301145). Of the 2984 references identified in our search, 36 were included in the systematic review and 35 in the meta-analysis. The prevalence of chronic pain was 31.2% (95% confidence interval [CI], 24.6%-38.7%; I2 = 98% [95% CI, 97%-99%]; P < .0001). In this global assessment, we found a high prevalence of chronic pain among women with HIV, underscoring the importance of understanding the etiology of chronic pain, identifying effective treatments, and conducting regular assessments in clinical practice.

Rodent models of postherpetic neuralgia: How far have we reached?

Background

Induced by varicella zoster virus (VZV), postherpetic neuralgia (PHN) is one of the common complications of herpes zoster (HZ) with refractory pain. Animal models play pivotal roles in disclosing the pain mechanisms and developing effective treatments. However, only a few rodent models focus on the VZV-associated pain and PHN.

Objective

To summarize the establishment and characteristics of popular PHN rodent models, thus offer bases for the selection and improvement of PHN models.

Design

In this review, we retrospect two promising PHN rodent models, VZV-induced PHN model and HSV1-induced PHN model in terms of pain-related evaluations, their contributions to PHN pathogenesis and pharmacology.

Results

Significant difference of two PHN models is the probability of virus proliferation; 2) Most commonly used pain evaluation of PHN model is mechanical allodynia, but pain-induced anxiety and other behaviours are worth noting; 3) From current PHN models, pain mechanisms involve changes in virus gene and host gene expression, neuroimmune-glia interactions and ion channels; 4) antiviral drugs and classical analgesics serve more on the acute stage of herpetic pain.

Conclusions

Different PHN models assessed by various pain evaluations combine to fulfil more comprehensive understanding of PHN.

Autologous fat grafting to the paravertebral space seems to prevent the postherpetic neuralgia-A single-arm pilot study

INTRODUCTION

Postherpetic neuralgia (PHN) is one of the most common complications of Herpes zoster (HZ), yet the mechanism and the treatment for PHN remains elusive. We first performed this feasibility study to verify the safety and efficiency of autologous fat grafting into the paravertebral space in early HZ to prevent PHN.

METHODS

Patients suffering from HZ with a rash in chest, back, or abdomen were arranged for autologous fat grafting to the paravertebral space. The primary endpoint was the incidence of PHN, which was defined as persistence pain in the affected dermal area in 12 weeks after fat grafting. Secondary endpoints including patient-reported changes in pain intensity, assessed pain threshold and the quality of life during follow-ups.

RESULTS

Eight patients accept the intervention and completed all follow-ups. Most patients report immediate pain relief after injection, one patient has a mild to moderate dizzy symptom after injection. No other short- or long-term adverse events occurred. For primary outcome, all patients have a timely reduced pain intensity, with no PHN events occurred, as all patients report pain intensity ≤3 in the VAS scale in 3 months after treatment. For electrical pain threshold, we identify that fat grafting differentially increases sensation and pain threshold in HZ area and healthy skin of patients. Besides, our results indicate significant improvement in patients' life quality decrease in analgesic consumption.

DISCUSSION

Autologous fat transplantation to the paravertebral space is a safe and feasible technique in preventing PHN from HZ in a rash. Further randomized controlled trial to investigate the actual long-term benefice of autologous fat grafting to the paravertebral space in preventing PHN is needed.

TRIAL REGISTRATION

ChiCTR, (ChiCTR1900025416); registered August 26, 2019.

Efficacy and safety of twice-daily tramadol hydrochloride bilayer sustained-release tablets with an immediate release component for postherpetic neuralgia: Results of a Phase III, randomized, double-blind, placebo-controlled, treatment-withdrawal study

BACKGROUND

We investigated the efficacy and safety of twice-daily bilayer sustained-release tramadol hydrochloride tablets (35% immediate-release; 65% sustained-release) in patients with postherpetic neuralgia.

METHODS

This was a Phase III treatment-withdrawal study with 1-4-week dose-escalation, 1-week fixed-dose, and 4-week randomized, double-blind, placebo-controlled withdrawal periods performed at 43 medical institutions in Japan. Patients aged ≥20 years, ≥3 months after the onset of herpes zoster with localized, persistent pain despite fixed-dose analgesics for ≥2 weeks before enrollment were eligible. Patients started tramadol at 100 mg/day and its dose escalated to a maximum of 400 mg/day to achieve a reduction in their Numeric Rating Scale (NRS) for pain of ≥2 points. Eligible patients were randomized to continue tramadol or switched to placebo for 4 weeks (double-blind period). Patients were withdrawn due to inadequate analgesia (NRS deteriorated on ≥2 consecutive days) or their request.

RESULTS

Overall, 252 patients started tramadol and 173 were randomized (tramadol: 85; placebo: 88). Tramadol was superior to placebo for the primary endpoint (time from randomization to an inadequate analgesic effect) with log-rank test p = 0.0005. The hazard ratio was 0.353 (95% confidence interval 0.190-0.657) in favor of tramadol and fewer patients in the tramadol group experienced inadequate analgesic effects (16.9% vs. 39.8%). Adverse events in ≥10% of patients in the open-label period were constipation (43.8%), nausea (34.9%), somnolence (18.5%), and dizziness (11.6%). The frequencies of adverse events in the double-blind period were similar in both groups.

CONCLUSION

Sustained-release tramadol tablets with an immediate-release component are effective and well tolerated for managing postherpetic neuralgia.

Analgesic Treatment Approach for Postherpetic Neuralgia: A Narrative Review

Post-herpetic neuralgia (PHN) is an entity derived from peripheral nerve damage that occurs during the reactivation of the Varicella Zoster Virus (VZV), which manifests itself through pain with neuropathic characteristics. This can prove to be very difficult to manage in the chronic stages of disease reappearance. There currently exists a multitude of treatment alternatives for PHN, however, prevention through the early initiation of antiviral regimens is vital. There are various pharmacological options available, but it is important to individualize each patient to maximize efficacy and minimize adverse effects. Interventional procedures have become a cornerstone in difficult-to-manage cases, and have shown promising outcomes when used in a multimodal approach by experienced specialists. It is necessary to make an objective diagnosis of PHN and start early treatment. Additionally there is current evidence that vouches for interventional therapies as well as individualization, with a clear establishment of therapeutic objectives according to the needs of each patient.

Ultrasound-guided percutaneous peripheral nerve stimulation for chronic refractory neuropathic pain: a unique series

During the last two decades, with the advent of recent technology, peripheral nerve stimulation has become an appealing modality at the forefront of pain management. In this case series, we document the clinical rationale and technical considerations on three of the most challenging cases, refractory to previous interventions, that were treated by our team with an ultrasound-guided percutaneous peripheral nerve stimulator targeting the musculocutaneous, bilateral greater occipital and subcostal nerves. At the 6-month follow-up, all patients experienced greater than 50% relief of baseline pain, with a near-complete resolution of pain exacerbations. Furthermore, to our knowledge, this is the first report of an ultrasound-guided percutaneous technique of a peripheral nerve stimulator targeting the musculocutaneous and subcostal nerves.

A comparative study between transcutaneous electrical nerve stimulation and pulsed electromagnetic field therapy in the management of post-herpetic neuralgia of the sciatic nerve

OBJECTIVES

To compare the efficacy of pulsed electromagnetic field therapy (PEMFT) versus transcutaneous electrical nerve stimulation (TENS) in the treatment of post-herpetic neuralgia of the sciatic nerve.

METHODS

A double-blinded randomized clinical study has included 56 patients (18 males and 38 females). Participants were randomly and equally assigned into 2 groups. Both groups received conventional physical therapy treatment. Moreover, group (A) has an additional TENS, and group (B) had PEMFT. Both modalities were applied once daily, 3 times a week for 20 minutes for 8 successive weeks. Visual analog scale (VAS) and carbamazepine intake (CMI) dose have been assessed before and after interventions.

RESULTS

There was a significant decrease in VAS and CMI post-treatment in group A and B compared with that pretreatment (P > .001). The percent decrease in VAS and CMI in group A were 72.44% and 69.47% respectively and that for group B was 68.95% and 67.94% respectively. The findings revealed a non-significant difference in VAS and CMI (P > .05) between groups. The Means of VAS and CMI were (2.4 ± 0.78, 204.5 ± 16.76 and 2.67 ± 0.9, 210.57 ± 16.5) in group A and group B respectively. The mean difference for VAS and CMI was (-0.27 and -6.07) between groups post-treatment respectively.

CONCLUSION

Both TENS and PEMFT were effective and nearly equivalent in improving the post-herpetic neuralgia of the sciatic nerve as measured by in VAS and CMI. Clinical recommendations should be highlighted to instigate the using of TENS and PEMFT in the management of post-herpetic neuralgia of the sciatic nerve.

Effect and safety of extracorporeal shockwave therapy for postherpetic neuralgia: A randomized single-blind clinical study

Objective

To evaluate the efficacy and safety of extracorporeal shockwave therapy (ESWT) for postherpetic neuralgia.

Design

Randomized single-blind clinical study.

Patients

Patients with postherpetic neuralgia.

Methods

Patients were randomly divided into the control group and the ESWT group. The control group received conventional treatment while the ESWT group received conventional treatment and ESWT. The primary outcome is pain degree as assessed by the numeric rating scale (NRS), and secondary outcomes include brief pain inventory (BPI), Self-rating Anxiety Scale (SAS), Self-rating Depression Scale (SDS), and Pittsburgh Sleep Quality Index (PSQI). Data were collected at baseline and at weeks 1, 4, and 12. Linear mixed-effects models were applied to repeated measurement data.

Results

The scores on the NRS, BPI, SAS, SDS, and PSQI decreased over time in both groups. The NRS and SDS scores of the ESWT group were statistically lower than the control group. There was no time × group interaction in the mixed model analysis. Baseline age was correlated with NRS scores and BPI scores, and invasive treatment was related to PSQI scores, with no interaction effect for baseline confounders observed. No adverse events were observed during the process of this trial.

Conclusion

Extracorporeal shockwave therapy combined with conventional treatment could relieve pain and improve the psychological state in patients with postherpetic neuralgia without serious adverse effects.

Neuromuscular Complications of SARS-CoV-2 and Other Viral Infections

In this article we review complications to the peripheral nervous system that occur as a consequence of viral infections, with a special focus on complications of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). We discuss neuromuscular complications in three broad categories; the direct consequences of viral infection, autoimmune neuromuscular disorders provoked by viral infections, and chronic neurodegenerative conditions which have been associated with viral infections. We also include discussion of neuromuscular disorders that are treated by immunomodulatory therapies, and how this affects patient susceptibility in the current context of the coronavirus disease 2019 (COVID-19) pandemic. COVID-19 is associated with direct consequences to the peripheral nervous system via presumed direct viral injury (dysgeusia/anosmia, myalgias/rhabdomyolysis, and potentially mononeuritis multiplex) and autoimmunity (Guillain Barré syndrome and variants). It has important implications for people receiving immunomodulatory therapies who may be at greater risk of severe outcomes from COVID-19. Thus far, chronic post-COVID syndromes (a.k.a: long COVID) also include possible involvement of the neuromuscular system. Whether we may observe neuromuscular degenerative conditions in the longer term will be an important question to monitor in future studies.

Methylprednisolone and local anesthetic for Long-term Postherpetic Neuralgia: a meta-analysis

OBJECTIVE

The purpose was to evaluate the efficacy of methylprednisolone combined with local anesthetics on the incidence or intensity of long-term PHN.

METHODS

We have performed comprehensive literature research in PubMed, Web of Science, Cochrane library, and China national knowledge infrastructure (CNKI) databases (inception through October 19, 2021). Relevant randomized controlled trials(RCTs) with long-term duration were included, regardless of the injection method. The indicators were the incidence of PHN and the Visual Analog Scale (VAS) scores.

RESULTS

Five randomized controlled trials with 980 patients were retrieved. Compared with standard treatment (antivirals) alone, the combination of methylprednisolone, local anesthetic and standard treatment exhibited a significant decrease in the incidence of PHN in 1 month (RR =0.38, 95%CI: 0.19 to 0.76), 3 months (RR =0.40, 95%CI: 0.19 to 0.84) and 6 months (RR =0.37, 95%CI: 0.15 to 0.94) after zoster onset. In VAS scores, there was also a significant difference between the two groups in long-term PHN (3 months: WMD=-1.57, 95%CI: -2.84 to -0.30; 6 months: WMD=-0.72, 95%CI: -1.29 to -0.16).

CONCLUSION

The combination of Methylprednisolone, local anesthetic, and standard treatment appears to be an ideal option for patients with PHN. Further investigation is needed for the safety of this therapy.

Clinical Efficacy of Pulsed Radiofrequency Combined with Intravenous Lidocaine Infusion in the Treatment of Subacute Herpes Zoster Neuralgia

Objective

Under the guidance of a digital subtraction angiography (DSA) machine, via fluoroscopic imaging techniques, patients diagnosed with herpes zoster neuralgia at the subacute stage, where self-reported pain lasts between 30 and 90 days, were treated with nerve pulsed radiofrequency surgery combined with intravenous lidocaine infusion or saline infusion as control. This study explores the clinical efficacy, safety, and clinical value of the combined treatment compared with nerve pulsed radiofrequency surgery alone.

Methods

In this study, 72 patients diagnosed with herpes zoster neuralgia at the subacute stage were randomly divided into two groups with matched gender, age, and clinical symptoms. Both groups received pulsed radiofrequency surgery for the affected nerve segments under DSA fluoroscopy. Five days after the operation, 0.9% saline was administered daily for five consecutive days (50 ml per day, intravenous infusion) to group A (n = 36), and lidocaine was administered daily for five consecutive days (3 mg per kg per day, intravenous infusion) to group B (n = 36). Patients with poor pain control during the treatment were given 10 mg morphine tablets for pain relief to reach visual analog scale (VAS) ≤4 points. Data of the following categories were collected: VAS score, self-rating anxiety scale (SAS) score, depression self-rating scale (SDS) score, Pittsburgh sleep quality score (PSQI), 45 body area rating scale score, skin temperature measurement using infrared thermography, analgesic drug use before and after treatment at six different time points: before surgery (T₀), one day after surgery (T₁), three days after surgery (T₂), five days after surgery (T₃), one month after surgery (T₄), and two months after surgery (T₅). Blood was collected from all patients in the morning before surgery and right after the last intravenous infusion of lidocaine at T₃. Serum inflammatory indexes including white blood cell count, lymphocyte count, neutrophils count, erythrocyte sedimentation rate count, C-reactive protein (CRP) level, calcitonin gene-related peptide (CGRP) level, and interleukin-6(IL-6) level were determined. Lastly, the incidence of complications and adverse reactions throughout the study was recorded.

Results

In total, 64 out of 72 patients completed the whole study. Two patients met the exclusion criteria in group A, one patient refused to participate, and one was lost to follow-up. Two patients met the exclusion criteria in group B, and two were lost to follow-up. Three patients in group B experienced vomiting during lidocaine treatment. The adverse symptom was relieved after symptomatic treatment. No patients in the two groups had severe complications such as hematoma at the puncture site, pneumothorax, and nerve injury. Compared with before treatment, the mean of VAS score, SAS score, SDS score, PSQI score, and skin temperature of both groups at each time point after interventional surgery were all significantly reduced. Furthermore, at each time point after surgery, the above indicators of group B patients were significantly lower than those of group A patients. After treatment, the consumption of analgesics in both groups was significantly lower than before treatment. Compared with group A, the consumption of analgesics was also significantly lower in group B. In addition, serum inflammatory indexes at the T₃ time point of the two groups of patients were lower than T₀. Among them, the erythrocyte sedimentation rate, CRP level, CGRP level, and interleukin-6 level of group B were significantly lower than those of group A. The incidence of postherpetic neuralgia (PHN) in group B patients (6.25%) was also lower than that in group A patients (25%).

Conclusion

DSA-guided nerve pulse radiofrequency surgery combined with intravenous lidocaine infusion can effectively relieve pain in patients diagnosed with herpes zoster nerves at the subacute stage, reduce the number of analgesic drugs used in patients, reduce postherpetic neuralgia incidence rate, and improve sleep and quality of life.

Acupuncture therapies for postherpetic neuralgia: a protocol for a systematic review and Bayesian network meta-analysis

INTRODUCTION

Postherpetic neuralgia (PHN) is the most common sequela of herpes zoster, and it is often refractory to guideline-recommended treatments. Acupuncture therapy, a wildly applied complementary-alternative treatment, may help in the management of PHN. Diverse types of acupuncture therapy for PHN have been proposed, however, their comparative efficacies remain unclear. This study protocol plans to compare the efficacy and safety of different acupuncture therapies for PHN.

METHODS AND ANALYSIS

Databases including MEDLINE, Embase, Cochrane Library, Web of Science, Chinese Biomedical Database, China National Knowledge Infrastructure, VIP Database, Wanfang Database, WHO International Clinical Trials Registry Platform, ClinicalTrials.gov, Chinese Clinical Trial Register and OpenGrey will be searched from their inception to January 2022. Randomised controlled trials (RCTs) assessing the effectiveness of acupuncture therapy on the management of PHN will be selected. The primary outcome is pain intensity. Secondary outcomes include negative emotions, sleep condition, quality of life and adverse events. Reviewers will conduct study selection, data extraction and risk of bias assessment procedures. Then, standard pair-wised meta-analysis and Bayesian network meta-analysis will be performed (if applicable). The Confidence in Network Meta-Analysis application will be used to assess the confidence in the evidence for the primary outcome.

ETHICS AND DISSEMINATION

All data used for this study will be extracted from published RCTs, thus, no ethical approval will be required. The results of this systematic review will be disseminated through peer-reviewed journal and conference presentation.

PROSPERO REGISTRATION NUMBER

CRD42020219576.

A new susceptibility index to predict the risk of severe herpes zoster-associated pain: A Japanese regional population-based cohort study, the Shizuoka study

BACKGROUND

Approximately 7-20% of patients with herpes zoster (HZ) develop zoster-associated pain (ZAP). ZAP not only impairs quality of life and psychological well-being, but also can reduce work effectiveness, which has negative economic effects. Reports of ZAP risk factors are inconsistent.

OBJECTIVE

To confirm risk factors for the development of severe ZAP in HZ patients in Japan using a large-scale database, the Shizuoka Kokuho Database.

METHODS

A population-based cohort study using the Shizuoka Kokuho Database was conducted. Of 792,647 patients, 7491 (0.95%) experienced "severe ZAP" (as defined in this study). We developed a ZAP risk prediction scoring system by identifying risk factors using logistic regression analysis of several candidate risk factors for severe ZAP: age, sex, seasonality, and presence of comorbidities (using the Charlson comorbidity index), excluding HIV/AIDS.

RESULTS

We identified peripheral vascular disease and the onset from October to December as novel risk factors for severe ZAP, in addition to the previously reported risk factors of age and comorbidities (cerebral vascular disease, chronic pulmonary disease, rheumatic disease, peptic ulcer, liver disease, diabetes, and malignant neoplasms with/without metastasis). In contrast, dementia was found to reduce ZAP risk. We developed a susceptibility index to predict the risk of ZAP.

CONCLUSION

We newly demonstrated that peripheral vascular disease and the onset from October to December are ZAP risk factors. Our comorbidity findings support previous observations. The susceptibility index proposed here provides a new approach to the prevention of ZAP using early intervention for high-risk patients.

Scalp dysesthesia: a neuropathic phenomenon

Scalp dysesthesia is an abnormal sensation of the scalp in the absence of cutaneous disease. It is characterized by a burning and/or itching sensation and can be related to a variety of neurogenic or psychogenic causes. This condition is extremely bothersome and is also common- especially amongst the geriatric population, in women, in patients with diabetes mellitus and patients with psychiatric history. However, despite its prevalence in many populations, there is limited data about its causes and characteristics. Given its limited cutaneous manifestations it is also easily misdiagnosed and an underrecognized cause of scalp pruritus in the dermatological community. Therefore, education on scalp dysesthesia is paramount to helping physicians identify and provide appropriate treatment for these patients. This review focuses predominately on the neurogenic causes (with a brief review of psychogenic itch) of scalp dysesthesia and the therapeutics that have been found to be effective for this condition. Neurogenic causes of scalp dysesthesia occur with damage to the central or peripheral pathways of itch sensation, resulting in modification and heightened sensitivity of nerves that result in abnormal sensations in the absence of or out of proportion to external stimuli. A comprehensive review of etiologies is provided here, ranging from lesions to the central nervous system caused by cervical spine disease, trigeminal trophic syndrome, tumor, stroke, and multiple sclerosis, to small fiber neuropathies caused by diabetes, brow lifts, keloid and burn scarring. Recently, there have also been reports of scalp dysesthesias associated with post-infectious COVID-19. Treatment options tailored towards disease severity and different causes of disease will also be discussed. By elucidating the different mechanisms and therapeutic treatments of scalp dysesthesia, we hope to provide clinicians with the tools to identify and treat this condition as well as encourage further research into its etiologies and therapeutics.

Acupuncture (superficial dry-needling) as a treatment for chronic postherpetic neuralgia - a randomized clinical trial

BACKGROUND

Postherpetic neuralgia is a painful condition where finding sufficient treatment poses a great challenge. Acupuncture is often used as an alternative treatment for these pains, yet no randomized trials, using a sham-placebo have been performed to confirm its effect. Our objective was to investigate the efficacy of acupuncture compared to sham-acupuncture when treating chronic postherpetic dermal pain.

METHODS

We performed a sham-controlled double-blinded randomized clinical trial (RCT) with two arms. The intervention group received superficial dry-needling, and the control group received sham acupuncture using blunted needles. Twenty-six patients received two treatments. They filled out questionnaires at baseline and 1 month after treatment: (1) average and maximum pain (Numeric Rating Scale), (2) neuropathic pain (Neuropathic Pain Scale Inventory) and (3) Quality of Life (QoL) (Short-form 36).

RESULTS

Thirteen patients were allocated to the intervention group and 15 to the control group. We did not detect any significant changes in levels of pain and neuropathic pain. One QoL parameter, regarding emotional problems, reached a level of statistical significance. The sham-blinding was successful. This is the first RCT on the effect of acupuncture (superficial dry-needling) on postherpetic neuralgia (PHN), using a sham procedure as control. We observed no significant changes or tendencies in the measured levels of pain. One QoL parameter had significant improvement in the intervention group compared to the control group.

CONCLUSION

In conclusion, acupuncture was not superior to treatment with sham acupuncture. Though individual patients may experience some pain relief from acupuncture, our results do not support the routine use of this type of acupuncture to treat PHN.

Development of a Model for Predicting the Effectiveness of Pulsed Radiofrequency on Zoster-Associated Pain

Introduction

Zoster-associated pain (ZAP), which may cause anxiety, depression, and sleep disorders and reduce quality of life, is often refractory to current standard treatments. Studies have shown that pulsed radiofrequency (PRF) can alleviate ZAP and reduce the incidence of postherpetic neuralgia (PHN). This study aimed to explore the clinical characteristics associated with PRF responsiveness, develop a model for identifying risk factors of inadequate PRF management, and help clinicians make better decisions.

Methods

Patients who underwent PRF for ZAP between January 2017 and October 2020 in our hospital were included in this study. Patients were evaluated using the numerical rating scale (NRS), Insomnia Severity Index, Patient Health Questionnaire-9, and 36-Item Short Form Health Survey (SF-36) before and 3 months after the procedure. Patient demographic data and blood test results were also collected. We defined the effectiveness of PRF for ZAP as relief of > 50% in NRS scores compared to pre-PRF. Least absolute shrinkage and selection operator (LASSO) regression analyses were subsequently performed to identify factors related to the therapeutic effect of PRF in patients with ZAP. The performance of the prediction model was assessed by the area under the receiver operating characteristic curve (AUC).

Results

The effectiveness of PRF in patients with ZAP was 69.6% (total 313 patients) after 3 months. LASSO regression analysis extracted the seven most powerful features in the developed prediction model: sex, stage of herpes zoster (HZ), pregabalin dose, bodily pain indicators of SF-36, lymphocyte count, and low-density lipoprotein cholesterol (LDLC) and complement C4 in peripheral blood. Model = 1.586 + 0.148 × lymphocyte + (−0.001) × bodily pain indicators of SF-36 + (−0.001) × pregabalin dose + 0.028 × LDLC + 0.001 × C4 + (−0.508) × sex + (−0.128) × stage of HZ. We generated the ROC curve for the prediction model, and the final AUC was 0.701. The sensitivity, specificity, and overall accuracy of the model were 90%, 33%, and 73%, respectively.

Conclusions

Seven factors were significantly associated with poor PRF outcome: male sex, advanced stage of HZ, higher pregabalin dose, higher bodily pain indicators of SF-36, and lower lymphocyte count, LDLC, and complement C4 in the peripheral blood. PRF should be applied to patients with ZAP as early as possible to achieve satisfactory outcomes.

Mirogabalin as a Novel Gabapentinoid for the Treatment of Chronic Pain Conditions: An Analysis of Current Evidence

: Neuropathic pain is a challenge for physicians to treat and often requires a multimodal approach with both pharmacologic and lifestyle interventions. Mirogabalin, a potent, selective ligand of the α2δ-1 and α2δ-2 subunits of voltage-gated calcium channels (VGCCs), provides analgesia by inhibiting neurotransmitter release at the presynaptic end of the neuron. Mirogabalin offers more sustained analgesia than its gabapentinoid counterparts in addition to a wider safety margin for adverse events. Recent clinical trials of mirogabalin have demonstrated both efficacy and tolerability of the drug for the treatment of diabetic peripheral neuropathic pain and postherpetic neuralgia, leading to its approval in Japan. While still not yet FDA approved, mirogabalin is still in its infancy and offers potential into the treatment of neuropathic pain and its associated comorbidities.

Trigeminal Neuralgia: Current Approaches and Emerging Interventions

Trigeminal neuralgia (TN) has been described in the literature as one of the most debilitating presentations of orofacial pain. This review summarizes over 150 years of collective clinical experience in the medical and surgical treatment of TN. Fundamentally, TN remains a clinical diagnosis that must be distinguished from other types of trigeminal neuropathic pain and/or facial pain associated with other neuralgias or headache syndromes. What is increasingly clear is that there is no catch-all medical or surgical intervention that is effective for all patients with trigeminal neuralgia, likely reflective of the fact that TN is likely a heterogenous group of disorders that jointly manifests in facial pain. The first-line treatment for TN remains anticonvulsant medical therapy. Patients who fail this have a range of surgical options available to them. In general, microvascular decompression is a safe and effective procedure with immediate and durable outcomes. Patients who are unable to tolerate general anesthesia or whose medical comorbidities preclude a suboccipital craniectomy may benefit from percutaneous methodologies including glycerol or radiofrequency ablation, or both. For patients with bleeding diathesis due to blood thinning medications who are ineligible for invasive procedures, or for those who are unwilling to undergo open surgical procedures, radiosurgery may be an excellent option-provided the patient understands that maximum pain relief will take on the order of months to achieve. Finally, peripheral neurectomies continue to provide an inexpensive and resource-sparing alternative to pain relief for patients in locations with limited economic and medical resources. Ultimately, elucidation of the molecular mechanisms underlying trigeminal neuralgia will pave the way for novel, more effective and less invasive therapies.

Application of 5% Lidocaine Adhesive Patch in Painful Surgical Scars: Clinical Trial

Objective  The present paper aims to evaluate the use of a 5% lidocaine patch to treat neuropathic pain after orthopedic procedures in comparison with therapeutic massage over surgical incisions. Methods  This is a prospective, randomized clinical trial with 37 patients who underwent orthopedic surgery from January 2015 to February 2017. The study included subjects aged 13 to 70 years old who underwent foot and ankle orthopedic surgery and presented neuropathic pain or hypersensitivity at the surgical incision site for at least 90 days after the procedure. All patients were assessed for pain (using the visual analog scale [VAS]) and quality of life (with the SF-36 questionnaire) at the beginning of the treatment and after 30, 60, and 90 days. Results  Although the treatment improved pain in both groups, subjects using the lidocaine patch presented greater pain reduction over time. There were no statistically significant differences in the SF-36 questionnaire, with no significant evidence regarding functional capacity, physical aspects, vitality, emotional aspects, social aspects, general health condition, and mental health. The great advantage of the patch was the degree of personal satisfaction of the patients, with statistical relevance, probably due to the easy application and psychological effect of a drug therapy. Conclusion  Lidocaine patches and massages are effective treatment methods for reducing scar tissue pain, with similar outcomes. The patches improved the degree of patient satisfaction. Level of Evidence 1. Prospective randomized clinical trial.

Immunological mechanism of postherpetic neuralgia and effect of pregabalin treatment on the mechanism: a prospective single-arm observational study

BACKGROUND

Although neuropathic pain is a severe and common pain, its pathophysiology has not been elucidated yet. Studies in recent years have focused on the immune system's role in the pathogenesis of neuropathic pain. The aim of this study was to investigate the role of immunological mechanisms in neuropathic pain and the effect of pregabalin by measuring immunological marker levels in peripheral blood before and after pregabalin treatment in postherpetic neuralgia (PHN) patients with neuropathic pain.

METHODS

Forty patients diagnosed with PHN were included in the study. CD4, T follicular cells (Tfh: CD4+CXCR5+PD1+), Th17 (CD4+CCR6+ and CD4+IL17A+), regulatory T cells (Treg: CD4+ CD25+foxp3+), Th1 (CD4+ CXCR3+ and CD4+ IFN-γ+) and Th2 (CD4+ IL-4+) cell ratios were measured in peripheral blood samples before treatment and after 3 months of treatment.

RESULTS

When immunological marker and inflammation parameter levels were compared before and after treatment, the helper T cell ratio (CD3+, CD4+) was 30.28 ± 12.27% before treatment and 34.93 ± 11.70% after treatment, so there was a statistically significant increase (P = 0.028). Th17 was 4.75 ± 5.02% before treatment and 5.80 ± 3.13% after treatment, and there was a statistically significant increase (P = 0.036).

CONCLUSIONS

Immunological mechanisms play an essential role in the pathogenesis of neuropathic pain, immunologically based treatment approach will be the critical point of treatment.

Modulation of mRNA expression of IL-6andmTORC1 and efficacy and feasibility of an integrated approach encompassing cognitive behavioral therapy along with Pregabalin for management of neuropathic pain in Postherpetic Neuralgia: A Pilot Study

OBJECTIVE

This study was designed to explore the efficacy and feasibility of cognitive behavioural therapy(CBT) along with pregabalin and compare it with pregabalin monotherapy for the management of neuropathic pain in post-herpetic neuralgia (PHN) patients and to explore the modulation of mRNA expression of interleukin (IL)-6 and mammalian target of rapamycin-1 (mTORC1) genes in these patients.

DESIGN

Randomized controlled pilot study.

METHODS

The patients aged >18 years of age with an established diagnosis of PHN with evident allodynia and hyperalgesia who had pain for at least 3 months after healing of rash with pain intensity ≥4/10 on NRS-Pain Scale were enrolled. The trial was registered with the Clinical Trials Registry-India (CTRI/2019/03/018014). A detailed baseline assessment regarding type and duration of pain and disability using pain-relevant self-report questionnaires was done. Two ml venous blood samples were collected for gene expression studies at base line and at end of 12 weeks of treatment. Patients were randomized into one of the two groups. Group PR received pregabalin and Group CP received CBT along with pregabalin. The pain intensity was measured using numeric rating scale (NRS)-Pain scale, neuropathic component of the pain by using Neuropathic Pain Symptom Inventory (NPSI) and Pain Detect Questionnaire (PDQ), sleep interference by NRS-Sleep, pain-related catastrophic thoughts by using Pain Catastrophizing Scale (PCS), depression and quality of life using Beck Depression Inventory-II (BDI-II) and Short Form-12 (SF-12), respectively. The research funding was supported by the intramural grant from the institution.

RESULTS

A total of 40 patients with 20 in each group were included. Following integrated approach encompassing CBT and Pregabalin, group CP had significant downregulation of mRNA expression of IL-6; however, no such correlation was observed with mTOR expression. A significant decline in the intensity of pain, NPSI scoring for burning, allodynia, and pain-related catastrophizing were observed; also a significant improvement in depressive symptoms and quality of life were observed with the use of CBT.

CONCLUSIONS

A significant downregulation of mRNA expression of IL-6 was observed; however, no significant correlation was observed between NRS pain score and ΔCt values of mRNA expression of both mTORC1 gene and IL-6 gene at baseline and at the end of 12th week. In addition, we note a significant decrease in pain intensity, depressive symptoms, and pain-related catastrophizing while improving QOL was observed with the use of CBT as a clinical adjunct along with pregabalin in PHN patients.

The effect of subcutaneous injection of methylprednisolone acetate and lidocaine for refractory postherpetic neuralgia: a prospective, observational study

BACKGROUND

Postherpetic neuralgia (PHN) is the most common and bearable complication of herpes zoster (HZ). This pain may have negative impact on the patient's all aspects of daily life and health-related quality of life (HRQOL). Despite numerous advances in treatment, many patients remain resistant to the current therapy options. It is the first time subcutaneous injection of methylprednisolone acetate and lidocaine has been used to treat refractory PHN. We report the results of this treatment evaluating pain relief and HRQOL improvement in this disorder.

METHODS

A total of 43 patients with refractory PHN was enrolled in the observational study. All patients received daily subcutaneous injection of methylprednisolone acetate and lidocaine for 10 consecutive days. The severity of pain was assessed by using Visual Analog Scale (VAS), and 36-Item Short Form Survey (SF-36) was applied to evaluate HRQOL. Assessment of the pain and HRQOL was carried out at baseline and posttreatment at 4 weeks as well as 6 and 12 months.

RESULTS

At baseline, all patients experienced severe PHN with average VAS scores of 8.44 ± 0.85 (minimum 7; maximum 10). At 4 weeks, 6 months, and 12 months after treatment, the pain had significantly decreased (P < .001), and all subjects showed significant improvement in all eight domains of HRQOL. No major adverse events associated with the subcutaneous injection were observed.

CONCLUSIONS

Our results indicate that subcutaneous injection of methylprednisolone acetate and lidocaine can be an effective and safe treatment for PHN.

Dorsal root ganglion stimulation for refractory post-herpetic neuralgia

Post-herpetic neuralgia is a chronic neuropathic pain disorder that is the sequela of the varicella zoster virus reactivation in the dorsal root ganglion. A variety of treatment modalities have been implemented, but pharmacologic treatments are often limited due to side effects and interventional procedures have yielded mixed results without promising long-term benefits being consistently seen. A dorsal root ganglion stimulator for treatment of post-herpetic neuralgia is a novel treatment option as it is able to specifically target the area affected. We present 3 patients who underwent implantation of permanent dorsal root ganglion stimulators and had a greater than 50% decrease in scoring on numerical rating scale (NRS) up to 18 months post-procedure and significantly reduced analgesic requirements.

Cutaneous Neuroimmune Interactions in Peripheral Neuropathic Pain States

Bidirectional interplay between the peripheral immune and nervous systems plays a crucial role in maintaining homeostasis and responding to noxious stimuli. This crosstalk is facilitated by a variety of cytokines, inflammatory mediators and neuropeptides. Dysregulation of this delicate physiological balance is implicated in the pathological mechanisms of various skin disorders and peripheral neuropathies. The skin is a highly complex biological structure within which peripheral sensory nerve terminals and immune cells colocalise. Herein, we provide an overview of the sensory innervation of the skin and immune cells resident to the skin. We discuss modulation of cutaneous immune response by sensory neurons and their mediators (e.g., nociceptor-derived neuropeptides), and sensory neuron regulation by cutaneous immune cells (e.g., nociceptor sensitization by immune-derived mediators). In particular, we discuss recent findings concerning neuroimmune communication in skin infections, psoriasis, allergic contact dermatitis and atopic dermatitis. We then summarize evidence of neuroimmune mechanisms in the skin in the context of peripheral neuropathic pain states, including chemotherapy-induced peripheral neuropathy, diabetic polyneuropathy, post-herpetic neuralgia, HIV-induced neuropathy, as well as entrapment and traumatic neuropathies. Finally, we highlight the future promise of emerging therapies associated with skin neuroimmune crosstalk in neuropathic pain.

Systematic Review and Meta-analysis of Herpes Zoster Vaccine in Patients With CKD

Introduction

Chronic kidney disease (CKD) is a risk factor for herpes zoster (HZ) infection. Few studies have examined HZ vaccine (HZV) in this population. We conducted a systematic review and meta-analysis investigating the efficacy and safety of HZV in patients with renal disease (CKD, dialysis, and transplant).

Methods

MEDLINE, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) databases (up to May 2020) were searched for randomized controlled trials and nonrandomized controlled studies evaluating HZV in patients with CKD for effectiveness and adverse event risks. Studies without a control group (placebo or no vaccine) were excluded. Extraction of prespecified data and risk of bias assessments using the Newcastle-Ottawa scale for cohort studies and the Cochrane Risk of Bias Tool for randomized controlled trials were done by 3 authors. Random-effects meta-analysis was used to generate pooled treatment effects and 95% confidence intervals.

Results

Included were 404,561 individuals from 8 studies (3 randomized controlled trials and 5 nonrandomized). All 8 studies examined HZ as an outcome, with 3 reporting adverse events. Risk of HZ was lower in patients who received HZV compared with controls (hazard ratio, 0.55; 95% confidence interval, 0.37–0.82; P < 0.01); however, heterogeneity was high (I² = 88%, P < 0.01). There was no significant difference in adverse events associated with HZV (hazard ratio, 1.03; 95% confidence interval, 0.54–1.28; P = 0.8).

Conclusions

HZV compared with control significantly lowers the risk of HZ without an increase in adverse events in CKD patients. However, significant heterogeneity was present. HZV should be actively considered in CKD patients because the prevalence of HZ is higher in this population.

Open-Label Adhesion Performance Studies of a New Lidocaine Topical System 1.8% versus Lidocaine Patches 5% and Lidocaine Medicated Plaster 5% in Healthy Subjects

Purpose

The primary objective was to evaluate adhesion performance of the lidocaine topical system 1.8% for 12 hours in healthy human subjects in three studies: as a single product (Study 1) and versus other lidocaine topical products (lidocaine patch 5% and lidocaine medicated plaster 5% [Study 2] and generic lidocaine patch 5% [Study 3]). Safety of the lidocaine topical system 1.8%, with a skin irritation focus, was a secondary objective.

Patients and Methods

All three studies were open-label, randomized, Phase 1 adhesion performance studies in healthy adult volunteers (N=125). Lidocaine topical products were applied for 12 hours per test, per study arm. Adhesion of all test products was scored at 0, 3, 6, 9, and 12 hours post-application. Skin irritation was scored after product removal or when a product detached.

Results

Overall, the majority (≥75%) of subjects treated with the lidocaine topical system 1.8% demonstrated ≥90% adhesion (FDA adhesion score 0) throughout the 12-hour administration period versus 13.6% of subjects treated with lidocaine patch 5%, 15.9% of subjects treated with lidocaine medicated plaster 5%, and 0% of subjects treated with the generic lidocaine patch 5%. There were no complete detachments with the lidocaine topical system 1.8%, whereas 4.5% of lidocaine patch 5% and lidocaine medicated plaster 5% detached, and 29% of generic lidocaine patch 5% detached. Minimal skin irritation was observed with each lidocaine topical product.

Conclusion

Across three studies, lidocaine topical system 1.8% demonstrated superior adhesion performance versus the three other products tested. Skin irritation was minimal across products and studies.

Clinicaltrials.gov

NCT04312750, NCT04320173, NCT04319926.

Intravenous Administration of Vitamin C in the Treatment of Herpes Zoster-Associated Pain: Two Case Reports and Literature Review

Background

Herpes zoster (HZ) is an acute inflammatory neurocutaneous disease caused by the reactivation of varicella-zoster virus. It is estimated that the incidence of postherpetic neuralgia following HZ is 10–20%. The leading risk factors of the prognosis are aging and immunity dysfunction. Vitamin C plays a pivoted role in enhancing white blood cell function. Epidemiological evidence and clinical studies have indicated an association between pain and suboptimal vitamin C status. At present, vitamin C has been used as an additional option in the treatment of HZ-associated pain. Despite the current controversy, case reports and randomized controlled studies have indicated that both acute- and postherpetic neuralgia can be dramatically alleviated following intravenous vitamin C infusions. Case Presentation. Two patients (male aged 72 and female 78 years) with HZ did not respond well to antiviral therapy and analgesics. Skin lesions in the right groin and front thigh healed after early antiviral therapy, but the outbreak of pain persisted in the male patient. The female patient presented to our clinic with clusters of rashes in the right forehead with severe edema of her right upper eyelid. Because nerve blockade could not be conducted for both patients, intravenous infusion of vitamin C was applied and resulted in an immediate remission of the breakthrough pain in the male patient and cutaneous lesions in the female patient.

Conclusions

The use of vitamin C appears to be an emerging treatment alternative for attenuating HZ and PHN pain. Hence, we recommend the addition of concomitant use of intravenously administered vitamin C into therapeutic strategies in the treatment of HZ-associated pain, especially for therapy-resistant cases. Furthermore, animal studies are required to determine analgesic mechanisms of vitamin C, and more randomized clinical trials are essential to further determine the optimal dose and timing of administration of vitamin C.

External therapy of Chinese medicine for postherpetic neuralgia: A protocol for systematic review and meta-analysis

BACKGROUND

Postherpetic neuralgia (PHN), the most common complication of herpes zoster, brings about a health-care burden at both the individual and societal levels. External therapy of Chinese medicine (ETCM) is an effective treatment of PHN generally available in China, yet there is incomplete evidence to evaluate the efficacy and safety of it.

METHODS

This protocol is based on the previous reporting items. We will search 3 English databases (PubMed, EMBASE, and the Cochrane Library) and 3 Chinese databases (CNKI, CBM, and Wan Fang Database) until January 2020. RCTs to evaluate the efficacy and safety of external therapy of Chinese medicine for postherpetic neuralgia will be included. The primary outcome will be assessed by VAS or NRS. We will use the criteria provided by Cochrane Handbook 5.3.0 for quality evaluation and risk assessment, and use the Revman 5.3 software for meta-analysis.

ETHICS AND DISSEMINATION

Ethical approval is not required for systematic review and meta- analysis. The results of this review will be disseminated in a peer-review journal.

PROSPERO REGISTRATION NUMBER

CRD42020163511.

Effectiveness and safety of lidocaine patch 5% to treat herpes zoster acute neuralgia and to prevent postherpetic neuralgia

Herpes zoster is often associated to acute neuralgia and postherpetic neuralgia (PHN). Their therapeutic management is still challenging: among therapeutic options, lidocaine patch 5% was rarely used in acute neuralgia on lesional skin, and its efficacy to prevent PHN was never studied. The efficacy and tolerability of lidocaine patch 5% was evaluated in 38 patients with acute neuralgia (19) and PHN (19). Pain intensity was investigated using DN4 questionnaire and NRS-11 scale at baseline and at week 2, 4, and 8. The use of rescue therapy was also evaluated. A significant reduction of DN4 and NRS-11 was observed already at W2, with further improvement at W4 and W8. A complete response to treatment (DN4 and NRS-11 = 0) at week 8 was higher in patients with acute neuralgia (63.2%) than PHN (31.6%). Rescue therapy gradually decreased in acute neuralgia patients from week 2 (57.9%) to week 8 (10.5%), with only two patients needing neuroleptics. In PHN patients rescue therapy remained stable (68.4%). According to our results, lidocaine patch 5% applied on lesional skin was well tolerated and ensured a rapid pain relief in acute neuralgia; if early used, it prevented PHN in almost all patients.

LncRNA KCNA2-AS regulates spinal astrocyte activation through STAT3 to affect postherpetic neuralgia

Objectives

Postherpetic neuralgia (PHN) is the most common complication of herpes zoster, but the mechanism of PHN is still unclear. Activation of spinal astrocytes is involved in PHN. Our study aims to explore whether lncRNA KCNA2 antisense RNA (KCNA2-AS) regulates spinal astrocytes in PHN through signal transducers and activators of transcription 3 (STAT3).

Methods

Varicella zoster virus (VZV)-infected CV-1 cells were injected into rats to construct a PHN model. Primary spinal cord astrocytes were activated using S-Nitrosoglutathione (GSNO). Glial fibrillary acidic protein (GFAP; marker of astrocyte activation), phosphorylated STAT3 (pSTAT3), and KCNA2-AS were analyzed by immunofluorescence and RNA fluorescence in situ hybridization. RNA pull-down and RNA immunoprecipitation were used to detect binding of KCNA2-AS to pSTAT3.

Results

KCNA2-AS was highly expressed in the spinal cord tissue of PHN model rats, and was positively correlated with GFAP expression. GFAP was significantly increased in GSNO-induced cells, but the knockdown of KCNA2-AS reversed this result. Meanwhile, pSTAT3 was significantly increased in GSNO-induced cells, but knockdown of KCNA2-AS reduced pSTAT3 within the nucleus while the total pSTAT3 did not change significantly. pSTAT3 bound to KCNA2-AS and this binding increased with GSNO treatment. Furthermore, knockdown of KCNA2-AS in PHN model rats relieved mechanical allodynia.

Conclusion

Down-regulation of KCNA2-AS alleviates PHN partly by reducing the translocation of pSTAT3 cytoplasm to the nucleus and then inhibiting the activation of spinal astrocytes.

Autologous fat grafting seems to alleviate postherpetic neuralgia - a feasibility study investigating patient-reported levels of pain

BACKGROUND

Postherpetic neuralgia (PHN) is a relatively common side effect after an outbreak of herpes zoster (HZ), characterized by chronic neuropathic dermal pain. No effective treatment exists today. Fat grafting has shown promise in alleviating neuropathic pain, yet the exact mechanism of action, at a biological level, is not yet known. We report on the first human study using autologous fat grafting for treating PHN. Our hypothesis was that fat grafting can alleviate pain and improve the quality of life (QoL) in patients suffering from PHN. If successful, this could be a safe, cost-effective alternative to analgesics. This safety and feasibility study aimed to investigate the possible pain-relieving effect of autologous fat grafting on PHN.

METHODS

Ten adult patients suffering from PHN underwent autologous fat grafting to a dermal area of neuralgia, with a 12-week follow up. The primary endpoint was patient-reported pain. Secondary endpoints were patient-reported changes in QoL, and the degree and quality of the neuropathic pain.

RESULTS

The pain was measured by using a visual analog scale (range: 0-10). We observed improvements in both the average and maximum level of pain with a reduction of (-4.0 ± 3.1) and (-5.1 ± 3.9), respectively, (Δ mean ± SD), P<0.05. All parameters investigating neuropathic pain were significantly reduced. No improvement was seen in the QoL. The average amount of fat grafted was 208 ml. We observed no serious adverse effects.

CONCLUSION

This study suggests that autologous fat grafting can relieve chronic pain resulting from HZ. The next step toward routine clinical translation is to perform a randomized, blinded, placebo-controlled trial with a more extended follow-up period.

Mirogabalin in Japanese Patients with Renal Impairment and Pain Associated with Diabetic Peripheral Neuropathy or Post-Herpetic Neuralgia: A Phase III, Open-Label, 14-Week Study

Purpose

Mirogabalin was recently approved in Japan for the treatment of peripheral neuropathic pain, based on data from clinical trials in diabetic peripheral neuropathic pain (DPNP) and post-herpetic neuralgia (PHN), common clinical conditions which cause intense distress for patients. We characterized the safety and tolerability of mirogabalin in Japanese patients with renal impairment.

Patients and Methods

This multicenter, open-label study (ClinicalTrials.gov identifier NCT02607280) enrolled renally impaired individuals aged ≥20 years diagnosed with DPNP or PHN, and with an average daily pain score (ADPS) of ≥4 over the 7 days prior to treatment initiation. Mirogabalin dosage was titrated for 2 weeks, followed by a fixed dose for 12 weeks according to degree of renal impairment: 7.5 mg twice daily for moderate impairment and 7.5 mg once daily for severe impairment. The primary endpoint was safety and tolerability of mirogabalin, evaluated via treatment-emergent adverse events (TEAEs). Secondary efficacy endpoints included change in ADPS from baseline to Week 14.

Results

Overall, 35 patients were enrolled (30 with moderate and 5 with severe renal impairment). Most TEAEs were mild or moderate in severity; the most commonly reported were nasopharyngitis (22.9%) and somnolence (11.4%). Only 4 patients (11.4%) discontinued treatment due to TEAEs. Mirogabalin significantly decreased ADPS from baseline in patients with renal impairment; least squares mean change from baseline at Week 14 was −1.9 (95% confidence interval: −2.8, −1.0).

Conclusion

Mirogabalin was well tolerated and significantly reduced pain levels when used to treat DPNP/PHN at a fixed dose of 7.5 mg once or twice daily in patients with renal impairment.

Postherpetic neuralgia and recalcitrant cystic lesions following herpes zoster: A case report and review of treatment options

Acute herpes zoster lesions in most cases are self-limited except in older and immunocompromised patients, wherein the pain can cause significant suffering. Postherpetic neuralgia is a painful situation for patients that can compromise the quality of life. Here, we report a 30-year-old healthy young man who developed treatment-resistant postherpetic neuralgia after herpes zoster (fourth/fifth thoracic segment) without any underlying immunocompromised state. He also developed some cystic lesions, which were removed by aspiration and surgery. The skin lesions improved 2 weeks after the surgery and postherpetic neuralgia was completely cured after 5 months, however cystic lesions recurred multiple times and were excised completely during each visit. Postherpetic neuralgia has a significant impact on the health-care cost borne by the society and affected individual, hence, it is essential to select appropriate treatment to manage the pain of postherpetic neuralgia.

Efficacy and safety of the extracorporeal shockwave therapy in patients with postherpetic neuralgia: study protocol of a randomized controlled trial

Background

Postherpetic neuralgia (PHN) is one of the most common types of chronic neuropathic pain, which seriously affects quality of the life because of pain severity and poor response to the currently available treatments. The main strategies for PHN management are medication and invasive interventional therapies; however, these approaches have many adverse effects, so it is important to find another effective and safe treatment for PHN.

Methods

A single-center, single-blind randomized clinical trial will evaluate 98 study participants randomized in a 1:1 ratio into control and experimental groups. The control group will receive conventional treatment including medication therapy and invasive interventional therapy. The experimental group will receive extracorporeal shockwave therapy (ESWT) in addition to conventional therapy. The primary outcome is pain intensity assessed on a visual analogue scale (VAS); the secondary outcomes are the following: quality of life assessed by the 36-Item Short-Form Health Survey (SF-36), psychological state for anxiety and depression measured by the Self-Rating Anxiety Scale (SAS) and Self-Rating Depression Scale (SDS), and sleep quality measured by the Pittsburgh Sleep Quality Index (PSQI). Assessors blinded to the randomization will collect data during the intervention period at baseline and weeks 1, 4, and 12. The plasma levels of tumor necrosis factor-α and interleukin-6 will be assessed before and after ESWT to explore the biochemical mechanisms of ESWT in the treatment of PHN.

Discussion

This randomized controlled trial will evaluate the effectiveness and safety of ESWT in patients with PHN and thus will provide clinical evidence for its use in the management of PHN and explore the potential biochemical mechanisms of this treatment.

Trial registration

www.ChiCTR.org.cn, identifier: ChiCTR1900025828. Registered on 10 September 2019

A Randomized, Open-Label, Bioequivalence Study of Lidocaine Topical System 1.8% and Lidocaine Patch 5% in Healthy Subjects

Purpose

This study was designed to characterize drug delivery with lidocaine topical system 1.8% vs lidocaine patch 5% through 2 PK studies.

Patients and Methods

Two Phase 1, single-center, open-label, randomized PK studies were performed in healthy adults. In Study 1, 56 subjects received a single intravenous bolus of 0.7 mg/kg of lidocaine as a lead-in to allow for the accurate determination of apparent dose of both products. After a 7-day washout period, subjects were randomized to receive either lidocaine topical system 1.8% or lidocaine patch 5% for 12 hours followed by another 7-day washout period, after which subjects crossed over to receive the other treatment for 12 hours. In Study 2, 54 subjects were randomized to receive either lidocaine topical system 1.8% or lidocaine patch 5% for 12 hours. After a 7-day washout period, subjects crossed over to receive the other treatment. Adhesion and skin irritation assessments were performed after application of the products in Study 2. In both studies, serial blood samples were collected to measure the plasma concentration of lidocaine after product application. Safety assessments and adverse events were monitored in both studies.

Results

The comparative PK analysis demonstrated that the two products, despite their difference in drug load and strength, are bioequivalent. Both products were well tolerated. In Study 2, dermal response scores (skin tolerability after removal) were similar between lidocaine topical system 1.8% and lidocaine patch 5%, with a mean irritation score per patch <1 (barely perceptible erythema), which is not considered to be clinically significant.

Conclusion

Bioequivalence was demonstrated between lidocaine topical system 1.8% and lidocaine patch 5%. A comparison of the single-time adhesion scores at 12 hours in Study 2 favored lidocaine topical system 1.8% over lidocaine patch 5%. Both products were well tolerated as a single application in healthy adult human subjects.

ClinicalTrialsgov

NCT04144192, NCT04149938.

Zoster sine herpete: a review

Zoster sine herpete (ZSH) is one of the atypical clinical manifestations of herpes zoster (HZ), which stems from infection and reactivation of the varicella-zoster virus (VZV) in the cranial nerve, spinal nerve, viscera, or autonomic nerve. Patients with ZSH display variable symptoms, such as neuralgia, however, different from HZ, ZSH show no zoster, which makes clinical diagnosis difficult. ZSH not only causes initial symptoms, such as neuropathic pain in the affected nerve, Bell palsy, and Ramsay Hunt syndrome, but also postherpetic neuralgia and fatal complications such as VZV encephalitis and stroke. The misdiagnosis of ZSH and tardy antiviral treatment may lead to severe ZSH sequelae. We review the publications related to ZSH, especially its diagnosis with VZV DNA and/or anti-VZV immunoglobulin (IgG and IgM). More work about ZSH, especially ZSH epidemiological survey and guidelines for its diagnosis and treatment, are needed because most of the present studies are case reports.