Treatment of Painful Diabetic Neuropathy-A Narrative Review of Pharmacological and Interventional Approaches

Diabetic peripheral neuropathy and neuromodulation techniques: a systematic review of progress and prospects

Neuromodulation for diabetic peripheral neuropathy represents a significant area of interest in the management of chronic pain associated with this condition. Diabetic peripheral neuropathy, a common complication of diabetes, is characterized by nerve damage due to high blood sugar levels that lead to symptoms, such as pain, tingling, and numbness, primarily in the hands and feet. The aim of this systematic review was to evaluate the efficacy of neuromodulatory techniques as potential therapeutic interventions for patients with diabetic peripheral neuropathy, while also examining recent developments in this domain. The investigation encompassed an array of neuromodulation methods, including frequency rhythmic electrical modulated systems, dorsal root ganglion stimulation, and spinal cord stimulation. This systematic review suggests that neuromodulatory techniques may be useful in the treatment of diabetic peripheral neuropathy. Understanding the advantages of these treatments will enable physicians and other healthcare providers to offer additional options for patients with symptoms refractory to standard pharmacologic treatments. Through these efforts, we may improve quality of life and increase functional capacity in patients suffering from complications related to diabetic neuropathy.

Efficacy of Frequency Rhythmic Electrical Modulated System (FREMS) in the treatment of diabetic neuropathy: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Painful diabetic peripheral neuropathy (DPN) is a debilitating complication of diabetes with limited treatment options. Frequency Rhythmic Electrical Modulated System (FREMS), a non-invasive electrotherapy, has shown promise in symptom management.

METHODS

Databases, including PubMed, Scopus, and Embase were searched until October 2024. Randomized controlled trials (RCTs) involving adults with DPN comparing FREMS with control were included. Data on Visual Analog Scale (VAS) scores and nerve conduction were extracted. Standardized mean differences (SMDs) with 95 % confidence intervals (CIs) were pooled using random-effects models. Risk of bias was assessed using RoB 2. Heterogeneity was quantified via I2 statistics, with sensitivity analyses and publication bias evaluation.

RESULTS

Five RCTs (333 participants) were included. Meta-analysis indicated that FREMS significantly reduced daytime VAS pain scores post-treatment (SMD -0.56, 95 % CI -0.82 to -0.29, I2 = 4 %) and at follow-up (SMD -0.47, 95 % CI -0.73 to -0.21, I2 = 0 %). Night-time VAS pain scores also improved post-treatment (SMD -0.54, 95 % CI -0.80 to -0.27, I2 = 44 %) and at follow-up (SMD -0.38, 95 % CI -0.65 to -0.12, I2 = 1 %). FREMS improved motor nerve conduction but showed no effect on sensory conduction or microvascular blood flow.

CONCLUSION

FREMS effectively reduces DPN pain with sustained benefits and a favorable safety profile. Further research should standardize treatment protocols and assess long-term outcomes for clinical integration.

Vitamin D receptor FokI polymorphism as a risk factor for painful diabetic neuropathy in type 2 diabetes mellitus patients

Painful diabetic neuropathy (PDN) is a common complication in patients with type 2 diabetes mellitus (T2DM) with disruption of vitamin D (VD) activity as one of the risk factors. Active VD exerts its biological functions through the vitamin D receptor (VDR), which polymorphisms in the VDR gene can impair. This study aims to establish VDR FokI and ApaI polymorphisms as risk factors for PDN. This case-control study used samples from T2DM patients with and without PDN. Neuropathic pain was diagnosed using the DN4 questionnaire, while FokI and ApaI polymorphisms were examined using the Polymerase Chain Reaction-Restriction Fragment Length Polymorphism method. Other factors examined included gender, hypertension, current insulin use, obesity, HbA1c levels, and dyslipidemia. A total of 64 subjects were involved in the study. The FokI polymorphism (CT+TT genotype) was a significant risk factor for PDN (OR 4.20; 95% CI [1.47-11.94]; p = 0.012). The T allele in the FokI polymorphism significantly increased the risk of PDN by 2.8 times (OR 2.78; 95% CI [1.28-6.01], p = 0.014). The ApaI polymorphism was not significantly associated with PDN. Diabetes duration ≥4.5 years and uncontrolled diabetes were other significant risk factors for PDN. Multivariate analysis identified three significant variables: FokI polymorphism (OR 5.00; 95% CI [1.37-18.24], p = 0.015), insulin use (OR 4.95; 95% CI [1.37-17.87], p = 0.015), and uncontrolled diabetes (OR 3.47; 95% CI [1.03-11.69], p = 0.045). The VDR FokI polymorphism with the T allele is a significant genetic risk factor for PDN in T2DM patients. The VDR ApaI polymorphism was not a significant risk factor for PDN.

Therapeutic Interventions for Diabetes Mellitus-associated Complications

BACKGROUND

Diabetes Mellitus (DM) is an alarming health concern, affecting approximately 537 million people worldwide. As a leading cause of morbidity and mortality, DM demands a comprehensive understanding of its diverse pathophysiological mechanisms and disease progression.

METHODS

This traditional review has consolidated literature on the pathogenesis of hyperglycemia, its progression into complications, and advances in optimal treatment strategies. The literature in the last two decades has been reviewed using several keywords, including "diabetes," "diabetes-associated complications", "novel therapeutic interventions for diabetes-associated diseases", "phyto-extracts as antidiabetic drugs", etc. in prominent databases, such as PubMed, Scopus, Google Scholar, Web of Science, and ClinicalTrials.gov.

RESULTS

We have discussed macrovascular and microvascular complications, such as atherosclerosis, cardiovascular disease, Peripheral Arterial Disease (PAD), stroke, diabetic nephropathy, retinopathy, and neuropathy, as well as various pharmacological and non-pharmacological interventions that are currently available for the management of DM. We have also focused on the potential of natural products in targeting molecular mechanisms involved in carbohydrate metabolism, insulin production, repair of pancreatic cells, and reduction of oxidative stress, thereby contributing to their antidiabetic activity. Additionally, novel therapeutic approaches, like genetic, stem cell, and immunomodulatory therapies, have been explored. We have also discussed the benefits and limitations of each intervention, emerging research and technologies, and precision medicine interventions.

CONCLUSION

This review has emphasized the need for an improved understanding of these advancements, which is essential to enhance clinicians' ability to identify the most effective therapeutic interventions.

RNA Interference Unleashed: Current Perspective of Small Interfering RNA (siRNA) Therapeutics in the Treatment of Neuropathic Pain

Neuropathic pain (NP) is one of the debilitating pain phenotypes that leads to the progressive degeneration of the central as well as peripheral nervous system. NP is often associated with hyperalgesia, allodynia, paresthesia, tingling, and burning sensations leading to disability, motor dysfunction, and compromised psychological state of the patients. Most of the conventional pharmacological agents are unable to improve the devastating conditions of pain because of their limited efficacy, undesirable side effects, and multifaceted pathophysiology of the diseased condition. A rapid rise in new cases of NP warrants further research for identifying the potential novel therapeutic modalities for treating NP. Recently, small interfering RNA (siRNA) approach has shown therapeutic potential in many disease conditions including NP. Delivery of siRNAs led to potential and selective downregulation of target mRNA and abolished the pain-related behaviors/pathophysiological pain response. The crucial role of siRNA in the treatment of NP by considering all of the pathways associated with NP that could be managed by siRNA therapeutics has been discussed. However, their therapeutic use is limited by several hurdles such as instability in systemic circulation due to their negative charge and membrane impermeability, off-target effects, immunogenicity, and inability to reach the intended site of action. This review also emphasizes several strategies and techniques to overcome these hurdles for translating these therapeutic siRNAs from bench to bedside by opening a new avenue for obtaining a potential therapeutic approach for treating NP.

Defining Short- and Long-Term Programming Requirements in Patients Treated With 10-kHz Spinal Cord Stimulation

OBJECTIVES

High-frequency spinal cord stimulation (10-kHz SCS) has been shown to be an effective treatment for refractory low back pain and neck pain with and without limb pain in clinical trial and real-world studies. However, limited information is available in the literature on the type and frequency of programming parameters required to optimize pain relief.

MATERIALS AND METHODS

Retrospective trial and postimplant clinical and system device data were analyzed from consecutive patients with neck pain and low back pain, with and without limb pain, from a single clinical site, including both thoracic and cervical lead placement. Best bipole, stimulation parameters, and outcomes, including pain relief, change in opioid medication use, sleep, and daily function, were analyzed.

RESULTS

Of the 92 patients in the trial, 70 received a permanent implant. Of these, the mean duration of follow-up was 1.8 ± 1.3 years. Pain relief of ≥50% at the last follow-up was achieved by 64% of patients implanted; in addition, 65% reduced their opioid medication use; 65% reported improved sleep, and 71% reported improved function. There was some consistency between the "best" bipole at trial and permanent implant, with 82% of patients within one bipole location, including 54% of permanent implants who were using the same best bipole as at trial. After permanent implant, device reprogramming was minimal, with ≤one reprogramming change per patient per quarter required to maintain pain outcomes.

CONCLUSIONS

In the study, 10-kHz SCS was an effective therapy for treating chronic pain, whereby a high responder rate (≥50% pain relief) was achieved with short time to pain relief in trial and maintained with limited device programming after permanent implant. The data presented here provide insight into the programming required during the trial and implant stages to obtain and maintain therapeutic efficacy.

Update on Treating Painful Diabetic Peripheral Neuropathy: A Review of Current US Guidelines with a Focus on the Most Recently Approved Management Options

Painful diabetic peripheral neuropathy (DPN) is a highly prevalent and disabling complication of diabetes that is often misdiagnosed and undertreated. The management of painful DPN involves treating its underlying cause via lifestyle modifications and intensive glucose control, targeting its pathogenesis, and providing symptomatic pain relief, thereby improving patient function and health-related quality of life. Four pharmacologic options are currently approved by the US Food and Drug Administration (FDA) to treat painful DPN. These include three oral medications (duloxetine, pregabalin, and tapentadol extended release) and one topical agent (capsaicin 8% topical system). More recently, the FDA approved several spinal cord stimulation (SCS) devices to treat refractory painful DPN. Although not FDA-approved specifically to treat painful DPN, tricyclic antidepressants, serotonin/norepinephrine reuptake inhibitors, gabapentinoids, and sodium channel blockers are common first-line oral options in clinical practice. Other strategies may be used as part of individualized comprehensive pain management plans. This article provides an overview of the most recent US guidelines for managing painful DPN, with a focus on the two most recently approved treatment options (SCS and capsaicin 8% topical system), as well as evidence for using FDA-approved and guideline-supported drugs and devices. Also discussed are unmet needs for this patient population, and evidence for potential future treatments for painful DPN, including drugs with novel mechanisms of action, electrical stimulation devices, and nutraceuticals.

Painful Diabetic Neuropathy: The Need for New Approaches

Painful diabetic neuropathy is a common vexing problem for people with diabetes and a costly problem for society. The pathophysiology is not well understood, and no safe and effective mechanistically-based treatment has been identified. Poor glycemic control is a risk factor for painful diabetic neuropathy. Excessive intraneuronal glucose in people with diabetes can be shunted away from physiological glycolysis into multiple pathological pathways associated with neuropathy and pain. The first three treatments that are traditionally offered consist of risk factor reduction, lifestyle modifications, and pharmacological therapy, which includes only three drugs that are approved for this indication by the United States Food and Drug Administration. All of these traditional treatments are often inadequate for relieving neuropathic pain, and thus, new approaches are needed. Modern devices based on neuromodulation technology, which act directly on the nervous system, have been recently cleared by the United States Food and Drug Administration for painful diabetic neuropathy and offer promise as next-in-line therapy when traditional therapies fail.

Where does spinal cord stimulation fit into the international guidelines for refractory painful diabetic neuropathy? a consensus statement

BACKGROUND

Although pharmacotherapy with anticonvulsants and/or antidepressants can be effective for many people with painful diabetic neuropathy (PDN), albeit with frequent side-effects, a critical juncture occurs when neuropathic pain no longer responds to standard first- and second-step mono- and dual therapy and becomes refractory. Subsequent to these pharmacotherapeutic approaches, third-line treatment options for PDN may include opioids (short-term), capsaicin 8% patches, and spinal cord stimulation (SCS).

AIM

This document summarizes consensus recommendations regarding appropriate treatment for refractory peripheral diabetic neuropathy (PDN), based on outcomes from an expert panel convened on December 10, 2022, as part of the Worldwide Initiative for Diabetes Education Virtual Global Summit, "Advances in the Management of Painful Diabetic Neuropathy."

PARTICIPANTS

Nine attendees, eminent physicians and academics, comprising six diabetes specialists, two pain specialists, and one health services expert.

EVIDENCE

For individuals with refractory PDN, opioids are a high-risk option that do not provide a long-term solution and should not be used. For appropriately selected individuals, SCS is an effective, safe, and durable treatment option. In particular, high-frequency (HF) SCS (10 kHz) shows strong efficacy and improves quality of life. To ensure treatment success, strict screening criteria should be used to prioritize candidates for SCS.

CONSENSUS PROCESS

Each participant voiced their opinion after reviewing available data, and a verbal consensus was reached during the meeting.

CONCLUSION

Globally, the use of opioids should rarely be recommended for refractory, severe PDN. Based on increasing clinical evidence, SCS, especially HF-SCS, should be considered as a treatment for PDN that is not responsive to first- or second-line monotherapy/dual therapy.

Repeat intramuscular transplantation of human dental pulp stromal cells is more effective in sustaining Schwann cell survival and myelination for functional recovery after onset of diabetic neuropathy

BACKGROUND AIMS

Mesenchymal stromal cell (MSC) therapy for diabetic neuropathy (DN) has been extensively researched in vitro and in pre-clinical studies; however, the clinical scenario thus far has been disappointing. Temporary recovery, a common feature of these studies, indicates that either the retention of transplanted cells deteriorates with time or recovery of supportive endogenous cells, such as bone marrow-derived MSCs (BM-MSCs), does not occur, requiring further replenishment. In DN, BM-MSCs are recognized mediators of Schwann cell regeneration, and we have earlier shown that they suffer impairment in the pre-neuropathy stage. In this study, we attempted to further elucidate the mechanisms of functional recovery by focusing on changes occurring at the cellular level in the sciatic nerve, in conjunction with the biodistribution and movement patterns of the transplanted cells, to define the interval between doses.

METHOD & RESULTS

We found that two doses of 1 × 106 dental pulp stromal cells (DPSCs) transplanted intramuscularly at an interval of 4 weeks effectively improved nerve conduction velocity (NCV) and restored motor coordination through improving sciatic nerve architecture, Schwann cell survival and myelination. Despite very minimal recovery of endogenous BM-MSCs, a temporary restoration of NCV and motor function was achieved with the first dose of DPSC transplantation. However, this did not persist, and a repeat dose was needed to consolidate functional improvement and rehabilitate the sciatic nerve architecture.

CONCLUSION

Thus, repeat intramuscular transplantation of DPSCs is more effective for maintenance of Schwann cell survival and myelination for functional recovery after onset of DN.

Understanding the role of hyperglycemia and the molecular mechanism associated with diabetic neuropathy and possible therapeutic strategies

Diabetic neuropathy is a neuro-degenerative disorder that encompasses numerous factors that impact peripheral nerves in the context of diabetes mellitus (DM). Diabetic peripheral neuropathy (DPN) is very prevalent and impacts 50% of diabetic patients. DPN is a length-dependent peripheral nerve lesion that primarily causes distal sensory loss, discomfort, and foot ulceration that may lead to amputation. The pathophysiology is yet to be fully understood, but current literature on the pathophysiology of DPN revolves around understanding various signaling cascades involving the polyol, hexosamine, protein-kinase C, AGE, oxidative stress, and poly (ADP ribose) polymerase pathways. The results of research have suggested that hyperglycemia target Schwann cells and in severe cases, demyelination resulting in central and peripheral sensitization is evident in diabetic patients. Various diagnostic approaches are available, but detection at an early stage remains a challenge. Traditional analgesics and opioids that can be used "as required" have not been the mainstay of treatment thus far. Instead, anticonvulsants and antidepressants that must be taken routinely over time have been the most common treatments. For now, prolonging life and preserving the quality of life are the ultimate goals of diabetes treatment. Furthermore, the rising prevalence of DPN has substantial consequences for occupational therapy because such therapy is necessary for supporting wellness, warding off other chronic-diseases, and avoiding the development of a disability; this is accomplished by engaging in fulfilling activities like yoga, meditation, and physical exercise. Therefore, occupational therapy, along with palliative therapy, may prove to be crucial in halting the onset of neuropathic-symptoms and in lessening those symptoms once they have occurred.

A Brief Review on the Novel Therapies for Painful Diabetic Neuropathy

PURPOSE OF REVIEW

Almost half of people diagnosed with diabetes mellitus will develop painful diabetic neuropathy (PDN), a condition greatly impacting quality of life with complicated pathology. While there are different FDA approved forms of treatment, many of the existing options are difficult to manage with comorbities and are associated with unwanted side effects. Here, we summarize the current and novel treatments for PDN.

RECENT FINDINGS

Current research is exploring alternative pain management treatments from the first line options of pregabalin, gabapentin, duloxetine, and amitriptyline which often have side effects. The use of FDA approved capsaicin and spinal cord stimulators (SCS) has been incredibly beneficial in addressing this. In addition, new treatments looking at different targets, such as NMDA receptor and the endocannabinoid system, show promising results. There are several treatment options that have been shown to be successful in helping treat PDN, but often require adjunct treatment or alterations due to side effects. While there is ample research for standard medications, treatments such as palmitoylethanolamide and endocannabinoid targets have extremely limited clinical trials. We also found that many studies did not evaluate additional variables other than pain relief, such as functional changes nor were there consistent measurement methods. Future research should continue trials comparing treatment efficacies along with more quality of life measures.

Aspirin attenuates morphine antinociceptive tolerance in rats with diabetic neuropathy by inhibiting apoptosis in the dorsal root ganglia

Morphine is a drug used in chronic pain such as diabetic neuropathy, but the development of tolerance to its antinociceptive effect is an important clinical problem. Aspirin is an analgesic and antiapoptotic drug used in combination with morphine as an adjuvant in diabetic neuropathy. Our aim in this study was to investigate the effects of aspirin on morphine-induced neuronal apoptosis and analgesic tolerance in rats with diabetic neuropathy. The antinociceptive effects of aspirin (50 mg/kg) and morphine (5 mg/kg) were evaluated by thermal pain tests. Streptozotocin (65 mg/kg) was injected intraperitoneally to induce diabetic neuropathy. To evaluate apoptosis, ELISA kits were used to measure caspase-3, Bax and Bcl-2 levels. Apoptotic cells were detected histologically by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) method. Study results indicate that prior administration of aspirin to diabetic rats significantly increased the antinociceptive efficacy of morphine compared to morphine alone. Thermal pain tests showed that aspirin significantly reduced morphine tolerance in rats with diabetic neuropathy. Biochemical analysis revealed that aspirin significantly decreased the levels of pro-apoptotic proteins, caspase-3 and Bax, while increasing the anti-apoptotic Bcl-2 in DRG neurons. Semiquantitative scoring demonstrated that aspirin provided a significant reduction in apoptotic cell counts in diabetic rats. In conclusion, these data suggested that aspirin attenuated morphine antinociceptive tolerance through anti-apoptotic activity in diabetic rat DRG neurons.

The role of protein kinases in diabetic neuropathic pain: an update review

Objectives

Diabetic neuropathic pain (DNP) is a debilitating symptom of diabetic neuropathy which seriously impairs patient's quality of life. Currently, there is no specific therapy for DNP except for duloxetine and gabapentin that show limited utility in alleviating DNP. The present review aims to discuss the central role of protein kinases in the pathogenesis of DNP and their therapeutic modulation.

Methods

Scopus, PubMed, and Google scholar were searched up to January 2022 to find relevant studies with English language in which the roles of proteins kinases in DNP were examined.

Results

DNP is associated with hyperactivity in pain sensory neurons and therapies aim to specifically suppress redundant discharges in these neurons without affecting the activity of other sensory and motor neurons. Transient receptor potential vanilloid 1 (TRPV1) and purinergic 2 × 7 receptors (P2 × 7R) are two receptor channels, highly expressed in pain sensory neurons and their blockade produces remarkable analgesic effects in DNP. The activities of receptor channels are mainly regulated by the protein kinases whose modulation provides remarkable analgesic effects in DNP models.

Conclusion

Capsaicin, TRPV1 modulator, is the only agent successfully examined in clinical trials with promising effects in patients with DNP. Current data suggest that blocking calcium calmodulin dependent protein kinase II (CaMKII) is superior to other approaches, considering its pivotal role in regulating the pain neuron potentials. By this means, DNP alleviation is achievable without affecting the activity of other sensory or motor neurons.

Spinal cord vascular degeneration impairs duloxetine penetration

Introduction

Chronic pain is a prevalent physically debilitating health-related morbidity. Frontline analgesics are inadequate, providing only partial pain relief in only a proportion of the patient cohort. Here, we explore whether alterations in spinal cord vascular perfusion are a factor in reducing the analgesic capability of the noradrenaline reuptake inhibitor, duloxetine.

Method

An established rodent model of spinal cord vascular degeneration was used. Endothelial-specific vascular endothelial growth factor receptor 2 knockout mouse was induced via hydroxytamoxifen administered via intrathecal injection. Duloxetine was administered via intraperitoneal injection, and nociceptive behavioural testing was performed in both WT and VEGFR2KO mice. LC-MS/MS was performed to explore the accumulation of duloxetine in the spinal cord in WT and VEGFR2KO mice.

Results

Spinal cord vascular degeneration leads to heat hypersensitivity and a decline in capillary perfusion. The integrity of noradrenergic projections (dopa - hydroxylase labelled) in the dorsal horn remained unaltered in WT and VEGFR2KO mice. There was an association between dorsal horn blood flow with the abundance of accumulated duloxetine in the spinal cord and analgesic capacity. In VEGFR2KO mice, the abundance of duloxetine in the lumbar spinal cord was reduced and was correlated with reduced anti-nociceptive capability of duloxetine.

Discussion

Here, we show that an impaired vascular network in the spinal cord impairs the anti-nociceptive action of duloxetine. This highlights that the spinal cord vascular network is crucial to maintaining the efficacy of analgesics to provide pain relief.

Painful Peripheral Neuropathies of the Lower Limbs and/or Lower Extremities Treated with Spinal Cord Stimulation: A Systematic Review with Narrative Synthesis

Introduction

Painful peripheral neuropathy (PPN) is a debilitating condition with varied etiologies. Spinal cord stimulation (SCS) is increasingly used when conservative treatments fail to provide adequate pain relief. Few published reviews have examined SCS outcomes in all forms of PPN.

Methods

We conducted a systematic review of SCS in PPN. The PubMed database was searched up to February 7th, 2022, for peer-reviewed studies of SCS that enrolled PPN patients with pain symptoms in their lower limbs and/or lower extremities. We assessed the quality of randomized controlled trial (RCT) evidence using the Cochrane risk of bias tool. Data were tabulated and presented narratively.

Results

Twenty eligible studies documented SCS treatment in PPN patients, including 10 kHz SCS, traditional low-frequency SCS (t-SCS), dorsal root ganglion stimulation (DRGS), and burst SCS. In total, 451 patients received a permanent implant (10 kHz SCS, n=267; t-SCS, n=147; DRGS, n=25; burst SCS, n=12). Approximately 88% of implanted patients had painful diabetic neuropathy (PDN). Overall, we found clinically meaningful pain relief (≥30%) with all SCS modalities. Among the studies, RCTs supported the use of 10 kHz SCS and t-SCS to treat PDN, with 10 kHz SCS providing a higher reduction in pain (76%) than t-SCS (38-55%). Pain relief with 10 kHz SCS and DRGS in other PPN etiologies ranged from 42-81%. In addition, 66-71% of PDN patients and 38% of nondiabetic PPN patients experienced neurological improvement with 10 kHz SCS.

Conclusion

Our review found clinically meaningful pain relief in PPN patients after SCS treatment. RCT evidence supported the use of 10 kHz SCS and t-SCS in the diabetic neuropathy subpopulation, with more robust pain relief evident with 10 kHz SCS. Outcomes in other PPN etiologies were also promising for 10 kHz SCS. In addition, a majority of PDN patients experienced neurological improvement with 10 kHz SCS, as did a notable subset of nondiabetic PPN patients.

Effects of 1-methyl-1, 2, 3, 4-tetrahydroisoquinoline on a diabetic neuropathic pain model

Background: Neuropathy is a prevalent and debilitating complication of poorly managed diabetes, contributing towards poor quality of life, amputation risk, and increased mortality. The available therapies for diabetic neuropathic pain (DPN) have limitations in terms of efficacy, tolerability and patient compliance. Dysfunction in the peripheral and central monoaminergic system has been evidenced in various types of neuropathic and acute pain. The objective of the present study was to investigate 1-methyl 1, 2, 3, 4-tetrahydroisoquinoline (1MeTIQ), an endogenous amine found in human brain with a known neuroprotective profile, in a model of streptozotocin (STZ) induced neuropathic pain. Methods: Diabetic neuropathy in male BALB/c mice was induced by intraperitoneal injection of a single dose of STZ (200 mg/kg). Upon development of DPN after 4 weeks, mice were investigated for mechanical allodynia (von Frey filament pressure test) and thermal hyperalgesia (tail immersion test). Ondansetron (1.0 mg/kg i.p.), naloxone (3.0 mg/kg i.p.) and yohimbine (2.0 mg/kg i.p.) were used to elucidate the possible mechanism involved. Postmortem frontal cortical, striatal and hippocampal tissues were dissected and evaluated for changes in levels of dopamine, noradrenaline and serotonin using High-Performance Liquid Chromatography (HPLC) with UV detection. Results: Acute administration of 1MeTIQ (15-45 mg/kg i.p.) reversed streptozotocin-induced diabetic neuropathic static mechanical allodynia (von Frey filament pressure test) and thermal hyperalgesia (tail immersion test), these outcomes being comparable to standard gabapentin. Furthermore, HPLC analysis revealed that STZ-diabetic mice expressed lower concentrations of serotonin in all three brain regions examined, while dopamine was diminished in the striatum and 1MeTIQ reversed all these neurotransmitter modifications. These findings suggest that the antihyperalgesic/antiallodynic activity of 1MeTIQ may be mediated in part via supraspinal opioidergic and monoaminergic modulation since they were naloxone, yohimbine and ondansetron reversible. Conclusion: It was also concluded that acute treatment with 1MeTIQ ameliorated STZ-induced mechanical allodynia and thermal hyperalgesia and restored brain regionally altered serotonin and dopamine concentrations which signify a potential for 1MeTIQ in the management of DPN.

Triple-nerve decompression surgery for the treatment of painful diabetic peripheral neuropathy in lower extremities: A study protocol for a randomized controlled trial

Objectives

Painful diabetic peripheral neuropathy (DPN) is often refractory to conventional medications. Triple-nerve decompression was proposed for painful DPN due to the frequent involvement of multiple nerve entrapments in diabetes. However, the role of decompressive surgery remains controversial. This trial aims to assess the efficacy of triple-nerve decompression for patients with painful DPN suggestive of nerve entrapment using a randomized controlled trial (RCT) design.

Methods and analysis

This trial is a single-center RCT and will be conducted in Shanghai Ninth People's Hospital. Enrolled subjects (n = 74) with painful DPN due to nerve compression, which can be detected by nerve conduction studies, will be randomly allocated at a 1:1 ratio into surgical and non-surgical groups. The primary outcome will be measured by 50% responder rates, which is defined as the proportion of subjects with at least 50% reduction of the mean weekly visual analog score (VAS) of pain from baseline after 6 months of treatment. Mean weekly VAS will be additionally evaluated 1 week (W1), 1 month (M1), and 3 months (M3) after treatment to monitor the changes in pain intensity. The secondary outcomes include two-point discrimination (TPD), Toronto clinical scoring system (TCSS), electrophysiological indexes, hospital anxiety and depression scale (HADS), and the medical outcome study short-form 36-item questionnaire (SF-36). A quantitative analgesic questionnaire (QAQ) will be used as a secondary outcome to quantify the analgesic medication weekly. TPD and TCSS will be conducted at W1, M1, M3, and M6 after treatment. Electrophysiological tests, HADS, and SF-36 will be performed at M3 and M6.

Ethics and dissemination

Ethics approval has been obtained from the Ethics Committee of Shanghai Ninth People's Hospital (SH9H-2-21-T323-2). It was registered on the Chinese Clinical Trial Registry website (http://www.chictr.org.cn) on 16 August 2021 with the number ChiCTR2100050049. Written informed consent will be obtained from all participants. The results of this trial will be disseminated via peer-reviewed journals, mass media, and presentations at national and international academic conferences.

High-Frequency 10-kHz Spinal Cord Stimulation Improves Health-Related Quality of Life in Patients With Refractory Painful Diabetic Neuropathy: 12-Month Results From a Randomized Controlled Trial

Objective

To evaluate high-frequency (10-kHz) spinal cord stimulation (SCS) treatment in refractory painful diabetic neuropathy.

Patients and Methods

A prospective, multicenter randomized controlled trial was conducted between Aug 28, 2017 and March 16, 2021, comparing conventional medical management (CMM) with 10-kHz SCS+CMM. The participants had hemoglobin A1c level of less than or equal to 10% and pain greater than or equal to 5 of 10 cm on visual analog scale, with painful diabetic neuropathy symptoms 12 months or more refractory to gabapentinoids and at least 1 other analgesic class. Assessments included measures of pain, neurologic function, and health-related quality of life (HRQoL) over 12 months with optional crossover at 6 months.

Results

The participants were randomized 1:1 to CMM (n=103) or 10-kHz SCS+CMM (n=113). At 6 months, 77 of 95 (81%) CMM group participants opted for crossover, whereas none of the 10-kHz SCS group participants did so. At 12 months, the mean pain relief from baseline among participants implanted with 10-kHz SCS was 74.3% (95% CI, 70.1-78.5), and 121 of 142 (85%) participants were treatment responders (≥50% pain relief). Treatment with 10-kHz SCS improved HRQoL, including a mean improvement in the EuroQol 5-dimensional questionnaire index score of 0.136 (95% CI, 0.104-0.169). The participants also reported significantly less pain interference with sleep, mood, and daily activities. At 12 months, 131 of 142 (92%) participants were "satisfied" or "very satisfied" with the 10-kHz SCS treatment.

Conclusion

The 10-kHz SCS treatment resulted in substantial pain relief and improvement in overall HRQoL 2.5- to 4.5-fold higher than the minimal clinically important difference. The outcomes were durable over 12 months and support 10-kHz SCS treatment in patients with refractory painful diabetic neuropathy.

Trial registration

clincaltrials.gov Identifier: NCT03228420.

Small Fiber Neuropathy

PURPOSE OF REVIEW

This narrative review aims to summarize advances in the field of small fiber neuropathy made over the last decade, with emphasis on novel research highlighting the distinctive features of SFN.

RECENT FINDINGS

While the management of SFNs is ideally aimed at treating the underlying cause, most patients will require pain control via multiple, concurrent therapies. Herein, we highlight the most up-to-date information for diagnosis, medication management, interventional management, and novel therapies on the horizon. Despite the prevalence of small fiber neuropathies, there is no clear consensus on guidelines specific for the treatment of SFN. Despite the lack of specific guidelines for SFN treatment, the most recent general neuropathic pain guidelines are based on Cochrane studies and randomized controlled trials (RCTs) which have individually examined therapies used for the more commonly studied SFNs, such as painful diabetic neuropathy and HIV neuropathy. The recommendations from current guidelines are based on variables such as number needed to treat (NNT), safety, ease of use, and effect on quality of life.

Antinociceptive and Antiallodynic Activity of Some 3-(3-Methylthiophen-2-yl)pyrrolidine-2,5-dione Derivatives in Mouse Models of Tonic and Neuropathic Pain

Antiseizure drugs (ASDs) are commonly used to treat a wide range of nonepileptic conditions, including pain. In this context, the analgesic effect of four pyrrolidine-2,5-dione derivatives (compounds 3, 4, 6, and 9), with previously confirmed anticonvulsant and preliminary antinociceptive activity, was assessed in established pain models. Consequently, antinociceptive activity was examined in a mouse model of tonic pain (the formalin test). In turn, antiallodynic and antihyperalgesic activity were examined in the oxaliplatin-induced model of peripheral neuropathy as well as in the streptozotocin-induced model of painful diabetic neuropathy in mice. In order to assess potential sedative properties (drug safety evaluation), the influence on locomotor activity was also investigated. As a result, three compounds, namely 3, 6, and 9, demonstrated a significant antinociceptive effect in the formalin-induced model of tonic pain. Furthermore, these substances also revealed antiallodynic properties in the model of oxaliplatin-induced peripheral neuropathy, while compound 3 attenuated tactile allodynia in the model of diabetic streptozotocin-induced peripheral neuropathy. Apart from favorable analgesic properties, the most active compound 3 did not induce any sedative effects at the active dose of 30 mg/kg after intraperitoneal (i.p.) injection.

A Real-World Analysis of High-Frequency 10 kHz Spinal Cord Stimulation for the Treatment of Painful Diabetic Peripheral Neuropathy

BACKGROUND

Diabetes is one of the most prevalent chronic health conditions and diabetic neuropathy one of its most prevalent and debilitating complications. While there are treatments available for painful diabetic peripheral neuropathy (pDPN), their effectiveness is limited.

METHOD

This retrospective, multi-center, real-world review assessed pain relief and functional improvements for consecutive patients with diabetic neuropathy aged ≥18 years of age who were permanently implanted with a high-frequency (10 kHz) spinal cord stimulation (SCS) device. Available data were extracted from a commercial database.

RESULTS

In total 89 patients consented to being included in the analysis. Sixty-one percent (54/89) of participants were male and the average age was 64.4 years (SD = 9.1). Most patients (78.7%, 70/89) identified pain primarily in their feet or legs bilaterally. At the last assessment, 79.5% (58/73) of patients were treatment responders, defined as having at least 50% patient-reported pain relief from baseline. The average time of follow-up was 21.8 months (range: 4.3 to 46.3 months). A majority of patients reported improvements in sleep and overall function relative to their baseline.

CONCLUSIONS

This real-world study in typical clinical practices found 10 kHz SCS provided meaningful pain relief for a substantial proportion of patients refractory to current pDPN management, similar to published literature. This patient population has tremendous unmet needs and this study helps demonstrate the potential for 10 kHz SCS to provide an alternative pain management approach.

Pharmacotherapy of Painful Diabetic Neuropathy: A Clinical Update

The rising prevalence of diabetes mellitus (DM) leads on to an increase in chronic diabetic complications. Diabetic peripheral neuropathies (DPNs) are common chronic complications of diabetes. Distal symmetric polyneuropathy is the most prevalent form. Most patients with DPN will remain pain-free; however, painful DPN (PDPN) occurs in 6-34% of all DM patients and is associated with reduced health-related-quality-of-life and substantial economic burden. Symptomatic treatment of PDPN and diabetic autonomic neuropathy is the key treatment goals. Using certain patient related characteristics, subjects with PDPN can be stratified and assigned targeted therapies to produce better pain outcomes. The aim of this review is to discuss the various pathogenetic mechanisms of DPN with special reference to the mechanisms leading to PDPN and the various pharmacological and non-pharmacological therapies available for its management. Recommended pharmacological therapies include anticonvulsants, antidepressants, opioid analgesics, and topical medications.

Efficacy and Safety of 10 kHz Spinal Cord Stimulation Using Cervical and Thoracic Leads: A Single-Center Retrospective Experience

INTRODUCTION

Spinal cord stimulation (SCS) with lower thoracic leads has been studied extensively. However, the evidence base for cervical SCS is less well developed, and reports of multiarea SCS lead placement are uncommon. Therefore, this single-center retrospective study evaluated outcomes from 10-kHz SCS with cervical or combined cervical and thoracic lead placement.

METHOD

All patients that underwent a 10-kHz SCS trial with either cervical or combined cervical and thoracic lead placement between 2015 and 2020 were included in our study. We reviewed patient's charts for demographic information, lead placement, and pain scores up to 48 months after implantation.

RESULTS

Of the 105 patients that underwent a 10-kHz SCS trial during the review period, 92 (88%) had back/neck or extremity pain that responded to therapy (≥ 50% pain relief from baseline) and received a permanent system. Sixty-two of these patients (67%) were implanted with combined cervical and thoracic leads, while 30 (33%) received cervical-only leads. Pain relief in both regions exceeded 60% at most visits throughout the 48-month study period. Throughout follow-up, the responder rate in both pain areas was consistently ≥ 70%. No unexpected adverse events occurred.

CONCLUSION

The 10-kHz SCS provided effective and durable pain relief with either cervical or combined cervical and thoracic leads. The efficacy and safety profile of both applications appears to be comparable to lower thoracic SCS. Our results suggest that 10-kHz SCS is a useful paresthesia-free therapeutic option for chronic neuropathic pain originating in the cervical area, as well as more complex multiarea pain presentations.

Treatment of painful diabetic neuropathy

Painful diabetic neuropathy is observed in almost half of patients with diabetes mellitus (DM) and is associated with a decrease in the quality of life, emotional disorders, sleep disorders. The achievement and maintenance of the normal level of glucose in the blood is the basis for the prevention and treatment of DM, but this often does not allow the patient from pain and other clinical manifestations of neuropathy. Drug diabetic neuropathy therapy methods are discussed, the results of randomized placebo controlled studies on the efficiency and side effects of various drugs are analyzed. It is noted that pregabalin and gabapenitin, as antidepressants duloxetin, venlafaxin and amitriptyline, are most effective as anti-epileptic agents. In our country, with painful diabetic neuropathy, the preparations of a-lipoic acid are widely used. Analyzed data on efficacy and complications of the use of transcutaneus electrical nerves stimulation and spinal cord stimulation with pain diabetic neuropathy refractory to drug therapy. It is noted that many patients with pain diabetic neuropathy have combined diseases, detection and effective treatment of which can lead to an improvement in the state of patients and reduce the manifestations of neuropathy.

Varicella-zoster virus reactivation causing herpes zoster ophthalmicus (HZO) after SARS-CoV-2 vaccination - report of three cases

Purpose

We are reporting 3 patients who presented acute zoster ophthalmicus (HZO), an activation of varicella-zoster virus, after mRNA anti-SARS-CoV-2 vaccination, seen directly or referred to our center.

Cases

A 73-year-old woman with history of ocular sarcoidosis presented HZO in the right V1 dermatome 16 days after a single booster dose of vaccination (Pfizer BioNTech). A 69-year-old woman presented HZO in her V1 left dermatome, occurring 10 days after her first dose of Pfizer BioNTech vaccine. A 72-year-old woman with no history of autoimmune pathology, candidate for cataract surgery, presented 13 days after the first dose of a Moderna mRNA vaccine with an eruption in the left V1 dermatome. All patients presented the VZV infection after their first dose of a mRNA type of vaccine. Treatment with Valacyclovir 1000 mg × 3/ day for 7–14 days was efficient in all cases.

Conclusion

Vaccines have been reported in the past to trigger different types of side effects such as viral or flu-like symptoms. It is only logical to note many different side effects for SARS-CoV-2 vaccines as the population vaccinated is exceeding any other number in history. VZV is one of the more severe side effects that can, however, be treated. It is quite obvious that, as far as mRNA vaccines are concerned, and probably also other anti-SARS-CoV-2 vaccines, that the benefit of vaccination certainly outweighs the possible but very low risk of ocular side effects that can mostly be treated.

Recommendations for Neuromodulation in Diabetic Neuropathic Pain

Over 50% of the 34 million people who suffer from diabetes mellitus (DM) are affected by diabetic neuropathy. Painful diabetic neuropathy (PDN) impacts 40–50% of that group (8.5 million patients) and is associated with a significant source of disability and economic burden. Though new neuromodulation options have been successful in recent clinical trials (NCT03228420), still there are many barriers that restrict patients from access to these therapies. We seek to examine our tertiary care center (Albany Medical Center, NY, USA) experience with PDN management by leveraging our clinical database to assess patient referral patterns and utilization of neuromodulation. We identified all patients with a diagnosis of diabetes type 1 (CODE: E10.xx) or diabetes type 2 (CODE: E11.xx) AND neuralgia/neuropathic pain (CODE: M79.2) or neuropathy (CODE: G90.09) or chronic pain (CODE: G89.4) or limb pain (CODE: M79.6) OR diabetic neuropathy (CODE: E11.4) who saw endocrinology, neurology, and/or neurosurgery from January 1, 2019, to December 31, 2019. We then determined which patients had received pain medications and/or neuromodulation to divide the cohort into three groups: no treatment, conservative treatment, and neuromodulation treatment. The cohorts were compared with chi-square or one-way ANOVA with multiple comparisons to analyze the differences. A total of 2,635 PDN patients were identified, of which 700 received no treatment for PDN, 1,906 received medication(s), and 29 received neuromodulation (intrathecal therapy, spinal cord stimulation, or dorsal root ganglion stimulation). The patients who received pain medications for PDN visited neurology more often than the pain specialists. Of the patients that received neuromodulation, 24 had seen neurology, 6 neurology pain, and 3 anesthesia pain. They averaged 2.78 pain medications prior to implant. Approximately 41% of the patients in the conservative management group were prescribed three or more medications. Of the 1,935 treated patients, only 1.5% of the patients received neuromodulation. The patients on three or more pain medications without symptomatic relief may be potential candidates for neuromodulation. An opportunity, therefore, exists to educate providers on the benefits of neuromodulation procedures.

High-frequency (10 kHz) spinal cord stimulation for the treatment of focal, chronic postsurgical neuropathic pain: results from a prospective study in Belgium

Aim: Chronic postsurgical pain (CPSP) is a common complication of surgery. This study was conducted to evaluate the efficacy and safety of paresthesia-free, 10-kHz spinal cord stimulation (SCS) as a treatment for CPSP. Patients & methods: Subjects in this prospective, single-arm study had an average pain intensity of ≥5 cm on a 10-cm visual analog scale. The subjects who had pain relief of ≥50% (response) with temporary trial stimulation were permanently implanted with 10-kHz SCS and assessed for 1 year. Results: At 12 months, 94% of subjects were responders to 10-kHz SCS, and 88% had pain remission (visual analog scale ≤2.5 cm). Conclusion: The pain relief was durable in CPSP subjects and the safety profile of 10-kHz SCS was as expected. Clinical trial registration: VT005076953 (Privacy Commission of Belgium).