Severe Postherpetic Neuralgia Research Articles

Development of a Prediction Model and Corresponding Scoring Table for Postherpetic Neuralgia Using Six Machine Learning Algorithms: A Retrospective Study.

Postherpetic neuralgia (PHN), a complication of herpes zoster, significantly impacts the quality of life of affected patients. Research indicates that early intervention for pain can reduce the occurrence or severity of PHN. This study aims to develop a predictive model and scoring table to identify patients at risk of developing PHN following acute herpetic neuralgia, facilitating informed clinical decision-making. We conducted a retrospective review of 524 hospitalized patients with herpes zoster at The First Affiliated Hospital of Zhejiang Chinese Medical University from December 2020 to December 2023 and classified them according to whether they had PHN, collecting a comprehensive set of 30 patient characteristics and disease-related indicators, 5 comorbidity indicators, 2 disease score values, and 10 serological indicators. Relevant features associated with PHN were identified using the least absolute shrinkage and selection operator (LASSO). Then, the patients were divided into a training set and a test set in a 4:1 ratio, with comparability tested using univariate analysis. Six models were established in the training set using machine learning methods: support vector machines, logistic regression, random forest, k-nearest neighbor, gradient boosting, and neural network. The performance of these models was evaluated in the test set, and a nomogram based on logistic regression was used to create a PHN prediction score table. Eight non-zero characteristic variables selected from the LASSO regression results were included in the model, including age [area under the curve (AUC)=0.812, p<0.001], Numerical Rating Scale (NRS) (AUC=0.792, p<0.001), receiving treatment time (AUC=0.612, p<0.001), rash recovery time (AUC=0.680, p<0.001), history of malignant tumor (AUC=0.539, p<0.001), history of diabetes (AUC=0.638, p<0.001), varicella-zoster virus immunoglobulin M (AUC=0.620, p<0.001), and serum nerve-specific enolase (AUC=0.659, p<0,001). The gradient boosting model outperformed other classifier models on the test set with an AUC of 0.931, 95% confidence interval (CI) (0.882-0.980), accuracy of 0.886 (95% CI 0.809-0.940). In the test set, our predictive scoring table achieved an AUC of 0.820 (95% CI 0.869-0.970) with accuracy of 0.790 (95% CI 0.700-0.864). This study presents a methodology for predicting the development of postherpetic neuralgia in shingles patients by analyzing historical case data, employing various machine learning techniques, and selecting the optimal model through comparative analysis. In addition, a logistic regression model has been used to create a scoring table for predicting the postherpetic neuralgia.

Trigeminal Ganglion Electrical Stimulation for Trigeminal Nerve Postherpetic Neuralgia: A Retrospective Study.

To investigate the clinical outcome of trigeminal ganglion electrical stimulation for the treatment of trigeminal postherpetic neuralgia (TPHN). A retrospective analysis of clinical data was performed on six patients who suffered from severe postherpetic neuralgia involving the trigeminal nerve maxillary and mandibular branch. They were admitted under the Pain Management Department of the First Hospital of Shanxi Medical University from July 2022 to February 2023 and underwent trigeminal ganglion electrical stimulation therapy. Visual analogue scale (VAS) scores, pregabalin dosage, pittsburgh sleep quality index (PSQI), self-rating anxiety scale (SAS), and self-rating depression scale (SDS) were recorded before treatment, as well as after treatment at 1, 4, 8, 12, and 24-week. Adverse reactions related to the treatment were also documented. After trigeminal ganglion electrical stimulation therapy, the VAS scores, PSQI scores, anxiety scores, depression scores, and pregabalin dosage of six patients showed significant reductions at 1, 4, 8, 12, and 24 weeks. (P < 0.05). No serious adverse reactions occurred in any of the patients. Trigeminal ganglion electrical stimulation effectively relieved postherpetic neuralgia in the distribution areas of the trigeminal nerve 2 and 3 branches, reduced the dosage of analgesics, improved the quality of sleep, and alleviated anxiety and depression symptoms in patients. Our data suggested that It was a safe and effective clinical.

Postherpetic Neuralgia Induced Asystole - A Deadly Consequence of a Common Disease

Postherpetic neuralgia is a well-studied and somewhat common sequala of herpes zoster leading to intense pain episodes. Pain-induced vasovagal episodes can rarely lead to asystole, which is a fatal potential complication. It is crucial to have a high clinical suspicion of asystole when a patient presents with severe herpetic neuralgia leading to syncope. This is a unique cause of a 67-year-old Caucasian female who presented with syncope caused by severe postherpetic neuralgia with the eventual finding of pain-induced asystole episodes. J MEDICINE 2023; 24(2): 162-165

Laser speckle contrast imaging to predict the effect of temporary spinal cord stimulation in postherpetic neuralgia patients: A prospective observational study

Temporary spinal cord stimulation (tSCS) can effectively reduce the pain and severity of postherpetic neuralgia (PHN). However, there are no effective and objective methods for predicting the effects of tSCS on PHN. Laser speckle contrast imaging (LSCI) is frequently used in neurology to evaluate the effectiveness of treatment. To assess the accuracy of LSCI in predicting the impact of tSCS on PHN, 14 adult patients receiving tSCS treatments for spinal nerve-innervated (C6-T2) PHN participated in this observational study. Visual analog scale (VAS) assessments and LSCI blood flow images of the fingers were recorded after the tSCS procedure. The results showed that the VAS scores of all patients decreased significantly. Moreover, the blood flow index (BFI) values were significantly higher than they were before the procedure. Increased blood flow and pain alleviation were positively correlated. The findings indicated that spinal nerve PHN (C6-T2) was significantly reduced by tSCS. Pain alleviation by tSCS was positively correlated with increased blood flow in the hand. The effect of tSCS on PHN may thus be predicted using an independent and consistent indicator such as LSCI.

Correlation between pain catastrophizing in acute herpes zoster and postherpetic neuralgia: a retrospective analysis.

The objective of this study was to examine the association between pain catastrophizing in acute phase herpes zoster and the development of postherpetic neuralgia. The medical records of all patients diagnosed with herpes zoster between February 2016 and December 2021 were retrieved. Inclusion criteria were patients aged > 50years who visited our pain center within 60days after rash onset and reported a pain intensity of ≥ 3 in a numerical rating scale. Patients with a score of 30 or more in the pain catastrophizing scale at baseline were assigned to the catastrophizer group, and those with a score < 30 were assigned to the non-catastrophizer group. We defined patients with "postherpetic neuralgia" and "severe postherpetic neuralgia" as those with a numerical rating scale score of 3 or more and 7 or more at 3months after baseline, respectively. Data of 189 patients were available for complete analysis. Age, baseline numerical rating scale, and prevalence of anxiety and depression were significantly higher in the catastrophizer than those in the non-catastrophizer group. Incidence of postherpetic neuralgia did not differ significantly between the groups (p = 0.26). Multiple logistic regression analysis showed that age, severe pain at baseline, and immunosuppressive state were the factors which were independently associated with developing postherpetic neuralgia. Severe pain at baseline was the only factor related to developing severe postherpetic neuralgia. Pain catastrophizing in the acute phase of herpes zoster may not be related to the development of postherpetic neuralgia.

Serum interleukin-6 levels are increased in post-herpetic neuralgia: a single-center retrospective study

BackgroundStudies have shown that the overall incidence rate of herpeszoster (HZ) in China is 6.64 cases per 1000 people, despite such harms brought by postherpetic neuralgia (PHN), the mechanism of the disease remains unclear in China. Currently, effective biomarkers to predict PHN remain unavailable, which makes it difficult to prevent and successfully treat PHN. ObjectiveThe aim of the study was to determine the serum interleukin-6 level in PHN. MethodsThe serum levels of interleukin 6 (IL-6) were measured by multi-antibody sandwich ELISA. The likert scale was used to represent the degree of neuralgia in the patients. Patients with PHN were divided into a mild PHN group and a severe PHN group according to the Likert scale. ROC curve was performed for evaluating the diagnostic efficiency of IL6 for PHN. The correlation between the IL6 level and the Likert scale before and after treatment with gabapentin and mecobalamin was analyzed. ResultsIL6 levels in PHN patients resulted higher compared to volunteers. Patients in the severe PHN group had a higher serum IL6 level than in the mild PHN group. The Likert scale score was related to the serum IL6 levels and the frequency of IL6 levels above the cutoff value (4.95 pg/mL) in PNH groups before and after treatment (p < 0.05). Study limitationsPain is subjective. Some mental states, such as anxiety and depression, greatly influence an individual’s perception of pain, and pain tolerance can vary between people. Therefore, pain scores can be affected by different individual factors. ConclusionsThe serum IL6 levels may be used as a biochemical indicator of the severity of PNH.

A retrospective study of the correlation between herpes zoster neuralgia and the serum neuron-specific enolase level in the largest dermatological hospital in Zhejiang province, China.

We studied the changes and clinical significance of the serum neuron-specific enolase (NSE) level in peripheral blood of patients with post-herpetic neuralgia (PHN).Material and methodsPatients with PHN were divided into a mild PHN group and a severe PHN group according to their scores on a 100-point Likert scale representing the degree of neuralgia. NSE levels in neuralgia patients and healthy volunteers were then compared by t-test. Receiver operating characteristic curve analysis was performed to evaluate the diagnostic efficiency of NSE for PHN. The correlation between NSE level and Likert scale score after treatment was analyzed.ResultsNSE levels in PHN patients were higher than those in the healthy volunteers. Patients in the severe PHN group had higher NSE levels than those in the mild PHN group. NSE level at admission was associated with the Likert scale score recorded on the 14th day of treatment (136.1 ± 32.81 vs. 87.53 ± 16.23 pg/mL) (P < 0.05). The ROC curve of NSE levels for PHN is shown that the area was 0.8713 (95% confidence interval, 0.7861–0.9564; p < 0.0001).ConclusionsThere was a correlation between NSE and PHN, in that the NSE level positively correlated with the short-term prognosis of patients with PHN.

Associations of OPRM1 A118G Gene Polymorphism with Pain Sensitivity and Opioid Dosage of Patients with Postherpetic Neuralgia

This study aimed to explore the associations of OPRM1 A118G gene polymorphism with pain sensitivity and opioid dosage of patients with postherpetic neuralgia (PHN). According to the 3-month follow-up results, 103 PNH patients were enrolled as a PHN group, and 112 without PHN after herpes zoster were included as a non-PHN group. The factors affecting PHN occurrence were subjected to one-way analysis of variance and multivariate logistic regression analysis. The frequency distribution of GG, AG and AA genotypes in both PHN and non-PHN groups conformed to the Hardy-Weinberg equilibrium law (P&gt;0.05). Initial treatment duration of more than 72 hours, severe acute pain and genotype GG were independent risk factors for PHN. Genotype GG exhibited significantly increased distribution frequency in mild, moderate and severe PHN groups. The 48-hour opioid dosage was highest in the patients with genotype GG (P&lt;0.05). OPRM1 A118G gene polymorphism causes individual differences in the pharmacodynamics of opioids in PHN patients.

The Safety and Effect of Local Botulinumtoxin A Injections for Long-Term Management of Chronic Pain in Post-Herpetic Neuralgia: Literature Review and Cases Report Treated with Incobotulinumtoxin A.

There are few reports on the safety and effectiveness of long-term botulinumtoxin A (BoNT A) therapy in severe chronic pain of post-herpetic neuralgia (PHN). The literature was searched with the term “neuropathic pain” and “botulinum” on PubMed (up to 29 February 2020). Pain was assessed with the Visual Analogue Scale (VAS) before and after BoNT A therapy. A total of 10 clinical trials and six case reports including 251 patients with PHN were presented. They showed that BoNT A therapy had significant pain reduction (up to 30–50%) and improvement in quality of life. The effect duration seems to be correlated with BoNT A doses injected per injection site. Intervals between BoNT A injections were 10–14 weeks. No adverse events were reported in cases and clinical studies, even in the two pregnant women, whose babies were healthy. The repeated (≥6 times) intra/subcutaneous injections of incobotulinumtoxin A (Xeomin®, Merz Pharmaceuticals, Germany) over the two years of our three cases showed marked pain reduction and no adverse events. Adjunctive local BoNT A injection is a promising option for severe PHN, as a safe and effective therapy in long-term management for chronic neuropathic pain. Its effect size and -duration seem to be depended on the dose of BoNT A injected per each point.

Experience of Management of Intractable Postherpetic Neuralgia on Perineum: A Case Report

Herpes zoster is a transient disease caused by the reactivation of latent varicella zoster virus. Approximately one in every three people develops herpes zoster during their life time. Postherpetic neuralgia is the most common complication associated with herpes zoster, and it often persists for several years and even for a lifetime despite the pharmacological treatment. A 74-year-old woman experienced severe postherpetic neuralgia on the coccyx and the vulva for 18 months. Authors performed six times of fluoroscopy-guided nerve blocks including pudendal nerve block, ganglion impar block, and L1 transforaminal epidural block. With repeated nerve blocks, her numeric rating scale decreased from 8 to 4, and after 5 months, her pain was controlled only with oral medication. Postherpetic neuralgia might be treated with nerve blocks regardless of its duration.

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

BackgroundPostherpetic 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.MethodsA 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.ResultsAt 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.ConclusionsOur results indicate that subcutaneous injection of methylprednisolone acetate and lidocaine can be an effective and safe treatment for PHN.

Effect of ultrasound-guided continuous erector spinae plane block on severe post-herpetic neuralgia in adolescent without skin rash.

Effect of ultrasound-guided continuous erector spinae plane block on severe post-herpetic neuralgia in adolescent without skin rash.

Long standing post-herpetic neuralgia resistant to standard anti-neuropathy medication showing quick dramatic improvement following treatment with sympathomimetic amines

Purpose: To determine if treatment with dextroamphetamine sulfate can alleviate severe chronic post-herpetic neuralgia that failed to respond to standard drugs typically used for neuropathy. Materials and Methods: An 88-year-old man with a five-year history of severe post-herpetic neuralgia pain who had failed to respond to pregabalin, and duloxetine was offered 15 mg of amphetamine salts extended release capsules. Eventually he was increased to 30 mg extended release capsules. Results: Within the first month of treatment there was significant relief of his pain with just 15 mg extended release capsule. After two months the dosage was increased to 30 mg extended release capsules and he has had at least a 90% reduction in pain which has lasted now five years. Discussion: Not only had this patient failed to respond to standard therapies for neuropathies, but he gained only marginal relief from lidocane patches, hydrocodone, oxydodone (all of which caused nausea), acupuncture, and TENS units. He has had no adverse side effects from the dextroamphetamine sulfate. Though the exact mechanism of action is not known for sure, the main hypothesis for the etiology of the sympathetic neural hyperalgesia syndrome is that the sympathetic nervous system controls cellular permeability, and a sensitive tissue already showing signs of increased permeability allows chemicals and toxic elements to permeate these tissues resulting in inflammation. The permeability problem is further compromised by sympathetic hypofunction. Dextroamphetamine sulfate is thought to stimulate the neurotransmitter dopamine which corrects the problem.

Efficacy of low level laser therapy in the treatment of postherpetic neuralgia

Background: Postherpetic neuralgia (PHN) is the most common complication of herpes zoster (HZ) and defined as pain that persists for more than 90 days after the onset of HZ rash. The chronic pain of PHN is debilitating and often associated with significant morbidity. It is a neuropathic pain and manifests as allodynia, hyperalgesia, or spontaneous pain. Although it is not considered to be life-threatening, sometime HZ is inadequately treated and may result in more severe PHN. Various treatment protocols for PHN are available; however, the result remains unsatisfactorily. The use of low level laser therapy (LLLT) in pain management is relatively new and is used with increasing frequency in the management of chronic pain. Aim: To assess the efficacy of low level laser therapy in the treatment of postherpetic neuralgia. Methods: Articles were searched through Pubmed/ MEDLINE, Cochrane, and Google scholar. Two randomized-controlled trials by Kemmotsu et al. and Moore et al. were obtained and critically appraised. Results: Based on the appraisal, studies by Kemmotsu et al. and Moore et al. are considered valid, important, and applicable. The results demonstrated a significant reduction in PHN intensity following a course of LLLT (p< 0.05). Conclusion: There is a statistically significant difference between the involvement of LLLT in PHN patients and without involvement of LLLT. LLLT is a noninvasive, painless, and safe method of treatment and may be recommended as an early intervention for pain therapy of PHN. Keywords: low level laser therapy, herpes zoster, pain, postherpetic neuralgia, treatment

Combination of local Botulinum toxin A injections and standard oral drug treatment allows improvement of long-term pain management in severe post-herpetic neuralgia: A case report

Combination of local Botulinum toxin A injections and standard oral drug treatment allows improvement of long-term pain management in severe post-herpetic neuralgia: A case report

The Case Files

The Case Files

Management and Prevention of Herpes Zoster Ocular Disease.

Herpes zoster (HZ) is caused by reactivation of latent varicella zoster virus (VZV) in people who have had chicken pox, usually resulting in a painful, unilateral, dermatomal, vesicular rash. Herpes zoster ophthalmicus occurs when the first division of cranial nerve V is involved. HZ is common, with approximately 1 million new cases per year in the United States, and occurs in 1 in 3 persons. Although the rate of HZ increases with age, over half of all cases occur under the age of 60 years. Complications of herpes zoster ophthalmicus include eye disease, postherpetic neuralgia (PHN), and strokes. VZV has also been found in temporal arteritis biopsies. There is growing evidence that HZ is followed by chronic active VZV infection contributing to these complications. In view of this, and the efficacy of suppressive antiviral treatment in reducing recurrent herpes simplex keratitis, a randomized controlled trial of suppressive valacyclovir to reduce new or worsening anterior segment disease and/or PHN is needed. The zoster vaccine (ZV) is safe and effective in reducing the burden of illness, severity of PHN, and incidence of HZ. It is Centers for Disease Control and Prevention recommended for persons aged 60 years and above without impaired cellular immunity, and Food and Drug Administration approved for those aged 50 and older. It is most effective in preventing HZ in recipients in their 50s. Because of underusage of the ZV, it has not impacted the epidemiology of the disease. Barriers to its use include cost, variable reimbursement, frozen storage, and lack of a strong recommendation by doctors.

Risk Factor and Prevention of Postherpetic Neuralgia.

Herpes zoster (HZ) and postherpetic neuralgia (PHN) are common diseases in a pain clinic. In Korea, the rate of clinical visits due to the incidence of herpes zoster was 7.93-12.54/1000 annually [1]. PHN is a painful neuropathy and the most common complication of HZ. A complete recovery from PHN is difficult for doctors despite of proper HZ treatment. In spite of the treatment, some patients suffered from severe PHN for several years. Therefore, the most important aspects are the risk factor of PHN and the method of prevention of PHN. In this issue of the Korean Journal of Pain (KJP), Jung et al. [2] reported the incidence of HZ in Cheonan, Korea. The results show that patients 50 years and older have a higher incidence of HZ, and the most common site of HZ was the thoracic nerve (47.9%), followed by the trigeminal nerve (21.4%). The incidence rate was similar to the affected site of PHN (thoracic area: 52.9%, trigeminal area: 15.6%) in Korea [3]. In patients who suffer from HZ, the risk factors of PHN are old age, presence of a painful prodrome, severe pain of HZ, severe rash, and immuno-compromised status [4,5,6]. In patients with HZ over 60 years, up to 25% progressed to PHN [7]. The proportion of PHN increases steadily from young ages up to 80-84 years [8]. Therefore, patients who are elderly and possess the risk factor with HZ must undergo more intensive treatment. The main treatment of HZ is medication and interventional therapy. Taking antiviral medication beginning within 72 hrs of rash onset is usually recommended [7,9,10]. Two meta-analyses suggest that the antiviral medication can reduce the overall duration of pain and incidence of PHN [11,12]. Epidural injection with a steroid within 2 months of HZ development is also recommended for the prevention of PHN [13]. In the previous survey of Korea, epidural injection was the most commonly performed interventional treatment in PHN patients [3]. Other interventions such as paravertebral block, peripheral block and sympathetic block are clinically effective for the treatment of HZ and PHN. For evidence-based medicine of interventional treatment of HZ and PHN, the investigations of randomized controlled trials regarding the interventions will be necessary. In this issue, Jeon et al. [10] described the prevention and treatment of HZ and PHN. They mention that vaccination against varicella zoster virus (VZV) can be the first line for the prevention of HZ and PHN. A previous review article reported that vaccination of VZV reduced morbidity from HZ and PHN [14]. Vaccination of VZV reduced the occurrence of herpes zoster by approximately 70% in individuals aged 50-59 years old [15]. In persons 60 years or older, the vaccination reduced the burden of illness from HZ by 61.1% and the risk of PHN by 66.5% [16]. Therefore, the vaccination of patients over 50 years old can be effective for the prevention of HZ and PHN. Although PHN is difficult to treat, early and intensive treatment of patients with HZ can reduce the occurrence of PHN. In healthy elderly people, a vaccination of VZV can also decrease the incidence of HZ and PHN.

Topical lidocaine for neuropathic pain in adults.

Lidocaine is a local anaesthetic that is sometimes used on the skin to treat neuropathic pain. To assess the analgesic efficacy of topical lidocaine for chronic neuropathic pain in adults, and to assess the associated adverse events. We searched CENTRAL, MEDLINE, and EMBASE from inception to 1 July 2014, together with the reference lists of retrieved papers and other reviews. We also searched ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) search portal to identify additional published or unpublished data. We included randomised, double-blind studies of at least two weeks' duration comparing any formulation of topical lidocaine with placebo or another active treatment in chronic neuropathic pain. Participants were adults aged 18 and over. We included only full journal publication articles. Two review authors independently extracted efficacy and adverse event data, and examined issues of study quality. We performed analysis using three tiers of evidence. First tier evidence derived from data meeting current best standards and subject to minimal risk of bias (outcome equivalent to substantial pain intensity reduction, intention-to-treat analysis without imputation for dropouts; at least 200 participants in the comparison, 8 to 12 weeks' duration, parallel design); second tier evidence from data that failed to meet one or more of these criteria and that we considered at some risk of bias but with adequate numbers in the comparison; and third tier evidence from data involving small numbers of participants that we considered very likely to be biased or used outcomes of limited clinical utility, or both. We included 12 studies (508 participants) in comparisons with placebo or an active control. Six studies enrolled participants with moderate or severe postherpetic neuralgia, and the remaining studies enrolled different, or mixed, neuropathic pain conditions, including trigeminal neuralgia and postsurgical or post-traumatic neuralgia. Four different formulations were used: 5% medicated patch, 5% cream, 5% gel, and 8% spray. Most studies used a cross-over design, and two used a parallel-group design. Two studies used enriched enrolment with randomised withdrawal. Seven studies used multiple doses, with one to four-week treatment periods, and five used single applications. We judged all of the studies at high risk of bias because of small size or incomplete outcome assessment, or both.There was no first or second tier evidence, and no pooling of data was possible for efficacy outcomes. Only one multiple-dose study reported our primary outcome of participants with ≥ 50% or ≥ 30% pain intensity reduction. Three single-dose studies reported participants who were pain-free at a particular time point, or had a 2-point (of 10) reduction in pain intensity. The two enriched enrolment, randomised withdrawal studies reported time to loss of efficacy. In all but one study, third tier (very low quality) evidence indicated that lidocaine was better than placebo for some measure of pain relief. Pooling multiple-dose studies across conditions demonstrated no clear evidence of an effect of lidocaine on the incidence of adverse events or withdrawals, but there were few events and the withdrawal phase of enriched enrolment designs is not suitable to assess the true impact of adverse events (very low quality evidence). This review found no evidence from good quality randomised controlled studies to support the use of topical lidocaine to treat neuropathic pain, although individual studies indicated that it was effective for relief of pain. Clinical experience also supports efficacy in some patients. Several large ongoing studies, of adequate duration, with clinically useful outcomes should provide more robust conclusions about both efficacy and harm.

Treat herpes zoster with systemic antivirals and post-herpetic neuralgia with various agents depending on its severity

Systemic antivirals are the mainstay treatment option for herpes zoster, although adequate pain relief should also be provided. For post-herpetic neuralgia (PHN), first-line treatment options include topical lidocaine or capsaicin for mild symptoms and systemic anticonvulsants (gabapentin and pregabalin) for more severe PHN. Other systemic agents, such as tricyclic antidepressants and opioids, can also provide benefit. Preventative measures, particularly vaccination, should be considered.