Management of Neuropathic Pain Associated with Spinal Cord Injury

Immersive virtual reality for chronic neuropathic pain after spinal cord injury: a pilot, randomized, controlled trial

Introduction

Neuropathic pain (NP) poses significant challenges for individuals with spinal cord injury (SCI), often inadequately managed by current interventions. Immersive virtual reality (IVR) has emerged as a promising approach for pain modulation, yet robust evidence is lacking.

Objectives

This pilot study investigated the analgesic effects of different IVR environments (scenic, somatic) compared with a control environment, and explored psychomotor properties influencing pain attenuation.

Methods

Twenty-two participants with NP caused by SCI were randomized into 3 IVR environments: somatic (n = 8), scenic (n = 7), and control (n = 8), undergoing 3 weekly sessions over 4 weeks with baseline, postintervention, and one-month follow-ups.

Results

There was a significant interaction effect between VR environment and time point on Neuropathic Pain Symptom Inventory scores (F(4,37.0) = 2.80, P = 0.04). Scenic VR participants exhibited reduced scores postintervention and at follow-up, with no significant changes in somatic VR or control environments. Similar trends were observed in secondary measures, such as Neuropathic Pain Scale and pain numeric rating scale. Enjoyment and presence were associated with decreased pain-change scores (F(1, 252) = 4.68, P = 0.03 for enjoyment; F(1, 223.342) = 7.92, P = 0.005 for presence), although not significantly influenced by VR environment or time point.

Conclusion

Both environments showed reduced pain outcomes, underscoring the need for personalized IVR pain therapies and informing further technology development for NP management.

Long-term outcome and predictors of neurological recovery in cervical spinal cord injury: a population-based cohort study

This retrospective study analyzed prognostic factors for neurological improvement and ambulation in 194 adult patients (≥ 15 years) with traumatic cervical spinal cord injuries treated at the neurological SCI unit (SCIU) at the Karolinska University Hospital Stockholm, Sweden, between 2010 and 2020. The primary outcome was American spinal injury association impairment scale (AIS) improvement, with secondary focus on ambulation restoration. Results showed 41% experienced AIS improvement, with 51% regaining ambulation over a median follow-up of 3.7 years. Significant AIS improvement (p < 0.001) and reduced bladder/bowel dysfunction (p < 0.001) were noted. Multivariable analysis identified initial AIS C-D (< 0.001), central cord syndrome (p = 0.016), and C0-C3 injury (p = 0.017) as positive AIS improvement predictors, while lower extremity motor score (LEMS) (p < 0.001) and longer ICU stays (p < 0.001) were negative predictors. Patients with initial AIS C-D (p < 0.001) and higher LEMS (p < 0.001) were more likely to regain ambulation. Finally, older age was a negative prognostic factor (p = 0.003). In conclusion, initial injury severity significantly predicted neurological improvement and ambulation. Recovery was observed even in severe cases, emphasizing the importance of tailored rehabilitation for improved outcomes.

Potentially harmful drug-drug interactions in the therapeutic regimens of persons with spinal cord injury

OBJECTIVES

Individuals with spinal cord injury deal with multiple health complications that require them to use many medications. The purpose of this paper was to find the most common potentially harmful drug-drug interactions (DDIs) in therapeutic regimens of persons with spinal cord injury, and the risk factors associated with it. We further highlight the relevance of each of the DDIs specific to spinal cord injury population.

DESIGN

Observational design and cross-sectional analysis.

SETTING

Community; Canada.

PARTICIPANTS

Individuals with spinal cord injury (n = 108).

MAIN OUTCOME MEASURES/ANALYSIS

The main outcome was the presence of one or more potential DDIs that can lead to an adverse outcome. All the reported drugs were classified as per the World Health Organization's Anatomical Therapeutic Chemical Classification system. Twenty potential DDIs were selected for the analysis based on the most common medications prescribed to people with spinal cord injury and severity of clinical consequences. The medication lists of study participants were analyzed for selected DDIs.

RESULTS

Among the 20 potential DDIs analyzed in our sample, the top 3 prevalent DDIs were Opioids + Skeletal Muscle Relaxants, Opioids + Gabapentinoids, and Benzodiazepines + ≥ 2 other central nervous system (CNS)-active drugs. Of the total sample of 108 respondents, 31 participants (29%) were identified with having at least one potential DDI. The risk of having a potential DDI was highly associated with polypharmacy, though no associations were found between the presence of a drug interaction and age, sex, level of injury, time since injury, or cause of injury among the study sample.

CONCLUSION

Almost three out of ten individuals with spinal cord injury were at risk of having a potentially harmful drug interaction. Clinical and communication tools are needed that facilitate identification and elimination of harmful drug combinations in the therapeutic regimens of patients with spinal cord injury.

Cannabis use by individuals with spinal cord injury in the UK: a call for improved patient education and physician awareness for pain and spasticity management

STUDY DESIGN

Prospective observational qualitative study.

OBJECTIVE

Cannabis is used by patients for the treatment of chronic pain, spasticity, sleep issues or mood disorders such as anxiety and depression. Since 2018, it has been authorised in the United Kingdom for medical use as an unlicensed medicine. This study aims to determine if patients are using cannabis for the management of symptoms related to spinal cord injury, and if so, whether they are using medical or illicit cannabis.

METHODS

Spinal cord injury patients from the Yorkshire Regional Spinal Injuries Centre and SPINE Community in the United Kingdom were surveyed. Participants were sent a 7-point electronic survey. All results were anonymous, and confidentiality was maintained throughout the process.

RESULTS

In total, 223 patients completed the survey. Not all patients answered every question. Of those who responded 65.35% (n = 132) were paraplegic and 34.65% (n = 70) were tetraplegic. Patients were suffering from chronic pain (longer than 3 months), spasticity, loss of/difficulty in sleeping or anxiety/depression. Almost 15% (14.93%, n = 33 out of 221) used cannabis to manage their symptoms, out of those the majority used street cannabis (79.41%, n = 27 out of 34) were using street cannabis.

CONCLUSION

This study demonstrates that there are spinal cord injury patients in the UK using cannabis to treat their symptoms. A majority appear to be using illicit cannabis. Given that cannabis can interact with other medications, and that the quality and content of illicit cannabis can be highly variable and at times dangerous, it is important for physicians to discuss cannabis use with their patients. This can inform prescribing and allow them to educate patients on the dangers of medical cannabis and potential alternatives.

Randomised, double-blind, placebo-controlled, parallel-group, multicentric, phase IIA clinical trial for evaluating the safety, tolerability, and therapeutic efficacy of daily oral administration of NFX88 to treat neuropathic pain in individuals with spinal cord injury

STUDY DESIGN

Double-blind, randomized, placebo-controlled, parallel-group multicentric phase IIA clinical trial.

OBJECTIVE

To assess the safety and tolerability of oral administration of NFX-88 in subjects with chronic spinal cord injury (SCI) and explore its efficacy in pain control.

SETTING

A total of 7 spinal cord injury rehabilitation units in Spain.

METHODS

A total of 61 adult with traumatic complete or incomplete spinal cord injury (C4-T12 level), were randomised 1:1:1:1 to a placebo, NFX88 1.05 g, 2.1 g, 4.2 g/day for up to 12 weeks. The placebo or NFX-88 was administered as add-on therapy to pre-existing pregabalin (150-300 mg per day). Safety and tolerability were evaluated, and the Visual Analogue Scale (VAS) was the primary measure to explore the efficacy of NFX-88 in pain control.

RESULTS

No severe treatment-related adverse effects were reported for any of the four study groups. 44 SCI individuals completed the study and were analysed. The data obtained from the VAS analysis and the PainDETECT Questionnaire (PD-Q) suggested that the combination of NFX88 with pregabalin is more effective than pregabalin with placebo at reducing neuropathic pain (NP) in individuals with SCI and that the dose 2.10 g/day causes the most dramatic pain relief.

CONCLUSIONS

NFX88 treatment was found to be highly safe and well tolerated, with the dose of 2.10 g/day being the most effective at causing pain relief. Thus, the promising efficacy of this first-in-class lipid mediator deserves further consideration in future clinical trials.

Relationships of self-reported opioid and benzodiazepine use with health-related quality of life among adults with spinal cord injury

BACKGROUND

There is limited understanding of the relationships between prescription opioid and benzodiazepine use and indices of health-related quality of life (HRQOL) among those with spinal cord injuries (SCI).

OBJECTIVE

To identify the relationships between self-reported prescription opioid and benzodiazepine use and two indicators of HRQOL, number of days in poor physical health and poor mental health in the past 30 days among adults with SCI.

METHODS

A cross-sectional cohort study of 918 adults with chronic (>1 year), traumatic SCI living in the Southeastern United States was conducted. Participants completed a self-report assessment (SRA).

RESULTS

In the preliminary model, both opioid and benzodiazepine use were associated with a greater number of days in poor physical health and poor mental health in the past month. After controlling for health conditions (pain intensity, spasticity, anxiety and perceived sleep insufficiency), opioid use was associated with 2.04 (CI = 0.69; 3.39) additional poor physical health days in the past 30 days, and benzodiazepine use was associated with 2.18 (CI = 0.70; 3.64) additional days of poor mental health. Age was associated with greater number of poor physical health days and fewer poor mental health days. Lower income was associated with poor mental health days. Most of the health conditions were significantly related to the number of past month poor physical and mental health days.

CONCLUSIONS

Opioid and benzodiazepine use are associated with poor physical and mental HRQOL, even after controlling for health conditions. Treatment strategies should consider potential unanticipated negative consequences of pharmacological interventions.

Choosing non-pharmacological treatments for neuropathic pain in spinal cord injury: a qualitative study

PURPOSE

The aims of this study were to explore (1) the considerations of people with spinal cord injury (SCI) in choosing to use non-pharmacological treatments (N-PTs) for neuropathic pain (NP), (2) which factors influence their decision and who is involved in this choice.

MATERIALS AND METHODS

Eleven individuals with SCI and NP were interviewed. Interviews were transcribed verbatim, transcripts were analysed through thematic coding, following an inductive content analysis approach.

RESULTS

A journey towards finding and choosing N-PTs emerged. Key phases in this journey were: motives, strategy and practical considerations. Pain and its impact on their life led participants to consider N-PTs. Motives were participants' negative attitudes towards regular medication, willingness to try everything and disappointment and frustration with the guidance from their health care provider (HCP). The search strategies often involved third parties and the internet. This led them to choose a specific N-PT. The journey was influenced by one's attitude, previous personal experience, experience of HCPs, financial considerations, availability and convenience of the treatment.

CONCLUSIONS

The journey individuals with SCI and NP go through to find N-PTs to manage pain is difficult and often lonely. Findings highlight the importance of HCPs accompanying people with SCI in finding N-PTs.

Sacral Bioneuromodulation: The Role of Bone Marrow Aspirate in Spinal Cord Injuries

Spinal cord injury (SCI) represents a severe trauma to the nervous system, leading to significant neurological damage, chronic inflammation, and persistent neuropathic pain. Current treatments, including pharmacotherapy, immobilization, physical therapy, and surgical interventions, often fall short in fully addressing the underlying pathophysiology and resultant disabilities. Emerging research in the field of regenerative medicine has introduced innovative approaches such as autologous orthobiologic therapies, with bone marrow aspirate (BMA) being particularly notable for its regenerative and anti-inflammatory properties. This review focuses on the potential of BMA to modulate inflammatory pathways, enhance tissue regeneration, and restore neurological function disrupted by SCI. We hypothesize that BMA's bioactive components may stimulate reparative processes at the cellular level, particularly when applied at strategic sites like the sacral hiatus to influence lumbar centers and higher neurological structures. By exploring the mechanisms through which BMA influences spinal repair, this review aims to establish a foundation for its application in clinical settings, potentially offering a transformative approach to SCI management that extends beyond symptomatic relief to promoting functional recovery.

Unraveling the Potential of Electroanalgesia: A Literature Review of Current Therapeutics

Neuropathic pain (NP), arising from dysfunction in the neurological system, poses a significant challenge in pain management due to its intricate origin and unpredictable response to conventional treatments. Electroanalgesia, a collection of techniques such as transcutaneous electric nerve stimulation (TENS), peripheral electrical nerve stimulation (PENS), spinal cord stimulation (SCS), deep brain stimulation (DBS), and electroacupuncture (EA), presents a potential alternative or complementary approach. This review brings together evidence from 56 studies to evaluate the effectiveness and safety of electroanalgesia in chronic NP. It discusses the mechanisms underlying NP, the indications for electroanalgesia, and the techniques utilized, emphasizing the diverse applications and potential benefits. However, despite its potential uses, electroanalgesia has its limitations, including variable effectiveness and potential adverse effects. Furthermore, the review recognizes the limitations of the methodology and the need for further research to refine treatment protocols and enhance the understanding of electroanalgesia's role in comprehensive pain management strategies.

Anxiety and Depression in Pediatric-Onset Traumatic Spinal Cord Injury: A Systematic Review

BACKGROUND

Traumatic spinal cord injury (TSCI) is a debilitating neurological condition with significant long-term consequences on the mental health and well-being of affected individuals. We aimed to investigate anxiety and depression in individuals with pediatric-onset TSCI.

METHODS

PubMed, Scopus, and Web of Science databases were searched from inception to December 20th, 2022 following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, and studies were included according to the eligibility criteria.

RESULTS

A total of 1013 articles were screened, and 18 studies with 4234 individuals were included in the final review. Of these, 1613 individuals (38.1%) had paraplegia, whereas 1658 (39.2%) had tetraplegia. A total of 1831 participants (43.2%) had complete TSCI, whereas 1024 (24.2%) had incomplete TSCI. The most common etiology of TSCI with 1545 people (36.5%) was motor vehicle accidents. The youngest mean age at the time of injury was 5.92 ± 4.92 years, whereas the oldest was 14.6 ± 2.8 years. Patient Health Questionnaire-9 was the most common psychological assessment used in 9 studies (50.0%). Various risk factors, including pain in 4 studies (22.2%), reduced sleep quality, reduced functional independence, illicit drug use, incomplete injury, hospitalization, reduced quality of life, and duration of injury in 2 (11.1%) studies, each, were associated with elevated anxiety and depression.

CONCLUSIONS

Different biopsychosocial risk factors contribute to elevated rates of anxiety and depression among individuals with pediatric-onset TSCI. Individuals at risk of developing anxiety and depression should be identified, and targeted support should be provided. Future large-scale studies with long-term follow-up are required to validate and extend these findings.

An Investigation of Manifold-Based Direct Control for a Brain-to-Body Neural Bypass

Objective: Brain-body interfaces (BBIs) have emerged as a very promising solution for restoring voluntary hand control in people with upper-limb paralysis. The BBI module decoding motor commands from brain signals should provide the user with intuitive, accurate, and stable control. Here, we present a preliminary investigation in a monkey of a brain decoding strategy based on the direct coupling between the activity of intrinsic neural ensembles and output variables, aiming at achieving ease of learning and long-term robustness. Results: We identified an intrinsic low-dimensional space (called manifold) capturing the co-variation patterns of the monkey's neural activity associated to reach-to-grasp movements. We then tested the animal's ability to directly control a computer cursor using cortical activation along the manifold axes. By daily recalibrating only scaling factors, we achieved rapid learning and stable high performance in simple, incremental 2D tasks over more than 12 weeks of experiments. Finally, we showed that this brain decoding strategy can be effectively coupled to peripheral nerve stimulation to trigger voluntary hand movements. Conclusions: These results represent a proof of concept of manifold-based direct control for BBI applications.

Self-Reported Prescription Opioid Use Among Participants with Chronic Spinal Cord Injury

Background

Individuals with spinal cord injuries (SCI) experience high rates of prescription opioid use, yet there is limited data on frequency of opioid use and specific medications being taken.

Objectives

To examine the frequency of self-reported prescription opioid use among participants with SCI and the relationship with demographic, injury, and socioeconomic characteristics.

Methods

A cohort study of 918 adults with SCI of at least 1-year duration completed a self-report assessment (SRA) that indicated frequency of specific prescription opioid use based on the National Survey on Drug Use and Health (NSDUH).

Results

Forty-seven percent of the participants used at least one prescription opioid over the last year; the most frequently used was hydrocodone (22.1%). Nearly 30% used a minimum of one opioid at least weekly. Lower odds of use of at least one opioid over the past year was observed for Veterans (odds ratio [OR] = 0.60, 95% CI = 0.38, 0.96) and those with a bachelor's degree or higher (OR = 0.63, 95% CI = 0.44, 0.91). When restricting the analysis to use of at least one substance daily or weekly, lower odds of use was observed for those with a bachelor's degree or higher and those with income ranging from $25,000 to $75,000+. None of the demographic or SCI variables were significantly related to prescription opioid use.

Conclusion

Despite the widely established risks, prescription opioids were used daily or weekly by more than 28% of the participants. Usage was only related to Veteran status and socioeconomic status indicators, which were protective of use. Alternative treatments are needed for those with the heaviest, most regular usage.

Brain Networks With Modified Connectivity in Patients With Neuropathic Pain and Spinal Cord Injury

Background. Neuropathic pain (NP) following spinal cord injury (SCI) affects the quality of life of almost 40% of the injured population. The modified brain connectivity was reported under different NP conditions. Therefore, brain connectivity was studied in the SCI population with and without NP with the aim to identify networks that are altered due to injury, pain, or both. Methods. The study cohort is classified into 3 groups, SCI patients with NP, SCI patients without NP, and able-bodied. EEG of each participant was recorded during motor imagery (MI) of paralyzed and painful, and nonparalyzed and nonpainful limbs. Phased locked value was calculated using Hilbert transform to study altered functional connectivity between different regions. Results. The posterior region connectivity with frontal, fronto-central, and temporal regions is strongly decreased mainly during MI of dominant upper limb (nonparalyzed and nonpainful limbs) in SCI no pain group. This modified connectivity is prominent in the alpha and high-frequency bands (beta and gamma). Moreover, oscillatory modified global connectivity is observed in the pain group during MI of painful and paralyzed limb which is more evident between fronto-posterior, frontocentral-posterior, and within posterior and within frontal regions in the theta and SMR frequency bands. Cluster coefficient and local efficiency values are reduced in patients with no reported pain group while increased in the PWP group. Conclusion. The altered theta band connectivity found in the fronto-parietal network along with a global increase in local efficiency is a consequence of pain only, while altered connectivity in the beta and gamma bands along with a decrease in cluster coefficient values observed in the sensory-motor network is dominantly a consequence of injury only. The outcomes of this study may be used as a potential diagnostic biomarker for the NP. Further, the expected insight holds great clinical relevance in the design of neurofeedback-based neurorehabilitation and connectivity-based brain-computer interfaces for SCI patients.

Evaluation of photobiomodulation therapy (117 and 90s) on pain, regeneration, and epigenetic factors (HDAC 2, DNMT3a) expression following spinal cord injury in a rat model

BACKGROUND

Photobiomodulation therapy (PBMT), due to its anti-inflammatory, analgesic effects, and most importantly as a non-invasive procedure, has currently gained a special setting in pain relief and the treatment of Spinal cord injuries (SCI). However, the mechanism of action of the PBM is not yet completely understood.

METHODS

In this study, SCI is induced by an aneurysm clip, and PBM therapy was applied by a continuous-wave (CW) laser with a wavelength of 660 nm. Adult male rats were divided into four groups: Control, SCI, SCI + PBMT 90s, and SCI + PBMT 117s. After 7 weeks, hyperalgesia, allodynia, and functional recovery were assessed. Fibroblasts infiltrating the spinal cord were counted after H&E staining. The expression of epigenetic factors (HDAC2, DNMT3a), protein relevant for pain (GAD65), and astrocytes marker (GFAP) after 4 weeks of daily PBMT (90 and 117s) was probed by western blotting.

RESULTS

Both PBMTs (90 and 117s) significantly improved the pain and ability to move and fibroblast invasion was reduced. SCI + PBMT 90s, increased GAD65, HDAC2, and DNMT3a expression. However, PBMT 117s decreased GFAP, HDAC2, and DNMT3a.

CONCLUSION

PBMT 90 and 117s improved the pain, and functional recovery equally. The regulation of epigenetic mechanisms appears to be a significant effect of PBMT117s, which emphasizes on impact of radiation duration and accumulative energy.

Chronic pain among Lebanese individuals with spinal cord injury: Pain interference and impact on quality of life

Background: Chronic pain is one of the most disabling consequences of spinal cord injury (SCI). Although studies have identified a link between chronic pain and decreased quality of life (QOL) among this population, few studies have looked into the experience of chronic pain in Lebanese individuals with SCI and the impact of pain characteristics on QOL. Thus, the present study evaluated the chronic pain experience and its associated factors among Lebanese individuals with SCI in order to determine the impact of pain on QOL. Methods: A cross-sectional study was conducted on 81 Lebanese individual with SCI between August 1st and October 31, 2022. The collected information included sociodemographic characteristics, SCI-related information, pain-related variables, and the 12-item Short Form Health Survey (SF-12). Factors associated with pain interference were evaluated using a linear regression model. One-way ANOVA and independent sample t-test were used to evaluate the association of different baseline and pain characteristics with QOL. Results: In the present study, 81.5% of participants reported chronic pain with the majority of them having neuropathic pain type. Employment status (P = 0.034), type of pain (P = 0.009), and pain severity (P = 0.028) were significantly associated with pain interference. Unemployed participants and those with severe chronic pain, particularly neuropathic pain, had lower QOL. Conclusion: Chronic pain was found to be highly prevalent among Lebanese patients with SCI. Pain interference and QOL were significantly affected by employment status and pain type. Therefore, targeting chronic pain and its associated factors in rehabilitation practice is warranted.

Cortical Mechanisms Underlying Immersive Interactive Virtual Walking Treatment for Amelioration of Neuropathic Pain after Spinal Cord Injury: Findings from a Preliminary Investigation of Thalamic Inhibitory Function

BACKGROUND

Neuropathic pain following spinal cord injury (SCI) affects approximately 60% of individuals with SCI. Effective pharmacological and non-pharmacological treatments remain elusive. We recently demonstrated that our immersive virtual reality walking intervention (VRWalk) may be effective for SCI NP. Additionally, we found that SCI NP may result from a decrease in thalamic γ-aminobutyric-acid (GABA), which disturbs central sensorimotor processing.

OBJECTIVE

While we identified GABAergic changes associated with SCI NP, a critical outstanding question is whether a decrease in SCI NP generated by our VRWalk intervention causes GABA content to rise.

METHOD

A subset of participants (n = 7) of our VRWalk trial underwent magnetic resonance spectroscopy pre- and post-VRWalk intervention to determine if the decrease in SCI NP is associated with an increase in thalamic GABA.

RESULTS

The findings revealed a significant increase in thalamic GABA content from pre- to post-VRWalk treatment.

CONCLUSION

While the current findings are preliminary and should be interpreted with caution, pre- to post-VRWalk reductions in SCI NP may be mediated by pre- to post-treatment increases in thalamic GABA by targeting and normalizing maladaptive sensorimotor cortex reorganization. Understanding the underlying mechanisms of pain recovery can serve to validate the efficacy of home-based VR walking treatment as a means of managing pain following SCI. Neuromodulatory interventions aimed at increasing thalamic inhibitory function may provide more effective pain relief than currently available treatments.

Misuse of gabapentinoids (pregabalin and gabapentin) in patients with neuropathic pain related to spinal cord injury

OBJECTIVE

To investigate the misuse of gabapentinoids (pregabalin and gabapentin) in patients with neuropathic pain related to spinal cord injury.

STUDY DESIGN

Cross-sectional study.

SETTING

Outpatient clinic in a physical therapy and rehabilitation hospital.

PARTICIPANTS

127 patients, aged 18-70 years, who had neuropathic pain related to spinal cord injury (SCI) and disease duration of at least 12 months.

OUTCOME MEASURES

Gabapentinoid use disorder of the patients was determined based on the DSM-5 diagnostic criteria for substance-related disorders. Patients were divided into 2 groups as those with drug misuse and those without drug misuse. Demographic and clinical information of the patients were compared between the groups. Factors associated with drug misuse were analyzed.

RESULTS

The misuse rate was 81.9% in patients using pregabalin and 69.69% in patients using gabapentin. Duration of disease and the Leeds assessment of neuropathic symptoms and signs (LANSS) score were statistically significantly higher in the drug misuse group. A statistically significant difference was found between the groups in terms of marital status, education and income level, and smoking and alcohol use. A statistically significant relationship was observed between drug misuse and duration of disease and LANSS score.

CONCLUSION

Misuse of gabapentinoids is prevalent in patients with neuropathic pain related to spinal cord injury. The duration of disease and the severity of NP are associated with misuse. Clinicians should exercise caution when prescribing gabapentinoids to patients with SCI.

Development of a pain education resource for people with spinal cord injury

Many people with spinal cord injury (SCI) develop chronic pain, including neuropathic pain. Unfortunately, current treatments for this condition are often inadequate because SCI-associated neuropathic pain is complex and depends on various underlying mechanisms and contributing factors. Multimodal treatment strategies including but not limited to pharmacological treatments, physical rehabilitation, cognitive training, and pain education may be best suited to manage pain in this population. In this study, we developed an educational resource named the SeePain based on published pain literature, and direct stakeholder input, including people living with SCI and chronic pain, their significant others, and healthcare providers with expertise in SCI. The SeePain was then 1) systematically evaluated by stakeholders regarding its content, comprehensibility, and format using qualitative interviews and thematic analysis, and 2) modified based on their perspectives. The final resource is a comprehensive guide for people with SCI and their significant others or family members that is intended to increase health literacy and facilitate communication between SCI consumers and their healthcare providers. Future work will quantitatively validate the SeePain in a large SCI sample.

Molecular Basic of Pharmacotherapy of Cytokine Imbalance as a Component of Intervertebral Disc Degeneration Treatment

Intervertebral disc degeneration (IDD) and associated conditions are an important problem in modern medicine. The onset of IDD may be in childhood and adolescence in patients with a genetic predisposition. With age, IDD progresses, leading to spondylosis, spondylarthrosis, herniated disc, spinal canal stenosis. One of the leading mechanisms in the development of IDD and chronic back pain is an imbalance between pro-inflammatory and anti-inflammatory cytokines. However, classical therapeutic strategies for correcting cytokine imbalance in IDD do not give the expected response in more than half of the cases. The purpose of this review is to update knowledge about new and promising therapeutic strategies based on the correction of the molecular mechanisms of cytokine imbalance in patients with IDD. This review demonstrates that knowledge of the molecular mechanisms of the imbalance between pro-inflammatory and anti-inflammatory cytokines may be a new key to finding more effective drugs for the treatment of IDD in the setting of acute and chronic inflammation.

Microglia polarization in nociplastic pain: mechanisms and perspectives

Nociplastic pain is the third classification of pain as described by the International Association for the Study of Pain (IASP), in addition to the neuropathic and nociceptive pain classes. The main pathophysiological mechanism for developing nociplastic pain is central sensitization (CS) in which pain amplification and hypersensitivity occur. Fibromyalgia is the prototypical nociplastic pain disorder, characterized by allodynia and hyperalgesia. Much scientific data suggest that classical activation of microglia in the spinal cord mediates neuroinflammation which plays an essential role in developing CS. In this review article, we discuss the impact of microglia activation and M1/M2 polarization on developing neuroinflammation and nociplastic pain, besides the molecular mechanisms engaged in this process. In addition, we mention the impact of microglial modulators on M1/M2 microglial polarization that offers a novel therapeutic alternative for the management of nociplastic pain disorders. Illustrating the mechanisms underlying microglia activation in central sensitization and nociplastic pain. LPS lipopolysaccharide, TNF-α tumor necrosis factor-α, INF-γ Interferon gamma, ATP adenosine triphosphate, 49 P2Y12/13R purinergic P2Y 12/13 receptor, P2X4/7R purinergic P2X 4/7 receptor, SP Substance P, NK-1R Neurokinin 1 receptor, CCL2 CC motif ligand 2, CCR2 CC motif ligand 2 receptor, CSF-1 colony-stimulating factor 1, CSF-1R colony-stimulating factor 1 receptor, CX3CL1 CX3C motif ligand 1, CX3XR1 CX3C motif ligand 1 receptor, TLR toll-like receptor, MAPK mitogen-activated protein kinases, JNK jun N-terminal kinase, ERK extracellular signal-regulated kinase, iNOS Inducible nitric oxide synthase, IL-1β interleukin-1β, IL-6 interleukin-6, BDNF brain-derived neurotrophic factor, GABA γ-Aminobutyric acid, GABAR γ-Aminobutyric acid receptor, NMDAR N-methyl-D-aspartate receptor, AMPAR α-amino-3-hydroxy-5-methyl-4-isoxazolepropi-onic acid receptor, IL-4 interleukin-4, IL-13 interleukin-13, IL-10 interleukin-10, Arg-1 Arginase 1, FGF fibroblast growth factor, GDNF glial cell-derived neurotrophic factor, IGF-1 insulin-like growth factor-1, NGF nerve growth factor, CD Cluster of differentiation.

Prescribing patterns for treating common complications of spinal cord injury

OBJECTIVE

The purpose of this study was to find the most and least commonly prescribed medications for treating secondary health complications associated with spinal cord injury (SCI); and determine overall polypharmacy rates and risk factors associated with it.

DESIGN

Observational design, cross-sectional analysis.

SETTING

Community; Canada.

PARTICIPANTS

Individuals with spinal cord injury (n = 108).

RESULTS

A total of 515 prescriptions were issued to the sample comprising 213 different medications to treat 10 SCI-related complications. Forty-five (45%) participants were prescribed >5 medications concurrently. No associations were found between the number of drugs taken and age, sex, level of injury, completeness of injury, time since injury, or cause of injury. The most commonly treated complications included pain (56.5%), muscle spasms (54%) and urinary tract infections (43%). Anti-convulsants (pregabalin, gabapentin), anti-spasmodics (baclofen, diazepam) and nitrofurantoins (Macrobid) were the most commonly prescribed medications to treat each of the three conditions, respectively. Thirty five percent of the total sample received a combination of two or more analgesics including fourth-line agents in the opiate class (hydromorphone, hydrocodone and morphine). Similarly, some participants were prescribed general muscle relaxants and cephalosporins for treatment of muscle spasms and urinary tract infections, respectively, that are generally not recommended in SCI patients. We compare these prescribing patterns with the available clinical practice guidelines and highlight areas where the prescriptions fall outside the recommended clinical practice while considering the complexity of medication management in SCI.

CONCLUSION

Medication management in SCI is complex. Tools are required that enable prescribers to choose evidence-based medical regimens and deprescribe potentially inappropriate medications for their patients with SCI.

Bridging the Gap between Nonliving Matter and Cellular Life

A cell, the fundamental unit of life, contains the requisite blueprint information necessary to survive and to build tissues, organs, and systems, eventually forming a fully functional living creature. A slight structural alteration can result in data misprinting, throwing the entire life process off balance. Advances in synthetic biology and cell engineering enable the predictable redesign of biological systems to perform novel functions. Individual functions and fundamental processes at the core of the biology of cells can be investigated by employing a synthetically constrained micro or nanoreactor. However, constructing a life-like structure from nonliving building blocks remains a considerable challenge. Chemical compartments, cascade signaling, energy generation, growth, replication, and adaptation within micro or nanoreactors must be comparable with their biological counterparts. Although these reactors currently lack the power and behavioral sophistication of their biological equivalents, their interface with biological systems enables the development of hybrid solutions for real-world applications, such as therapeutic agents, biosensors, innovative materials, and biochemical microreactors. This review discusses the latest advances in cell membrane-engineered micro or nanoreactors, as well as the limitations associated with high-throughput preparation methods and biological applications for the real-time modulation of complex pathological states.

Hydralazine plays an immunomodulation role of pro-regeneration in a mouse model of spinal cord injury

Spinal cord injury (SCI) results in severe motor and sensory dysfunction with no effective therapy. Spinal cord debris (sp) from injured spinal cord evokes secondary SCI continuously. We and other researchers have previously clarified that it is mainly bone marrow derived macrophages (BMDMs) infiltrating in the lesion epicenter to clear sp, rather than local microglia. Unfortunately, the pro-inflammatory phenotype of these infiltrating BMDMs is predominant which impairs wound healing. Hydralazine, as a potent vasodilator and scavenger of acrolein, has protective effects in many diseases. Hydralazine is also confirmed to promote motor function and hypersensitivity in SCI rats through scavenging acrolein. However, few studies have explored the effects of hydralazine on immunomodulation, as well as spontaneous pain and emotional response, the important syndromes in clinical patients. It remains unclear whether hydralazine affects infiltrating BMDMs after SCI. In this study, we targeted BMDMs to explore the influence of hydralazine on immune cells in a mouse model of SCI, and also investigated the contribution of polarized BMDMs to hydralazine-induced neurological function recovery after SCI in male mice. The adult male mice underwent T10 spinal cord compression. The results showed that in addition to improving motor function and hypersensitivity, hydralazine relieved SCI-induced spontaneous pain and emotional response, which is a newly discovered function of hydralazine. Hydralazine inhibited the recruitments of pro-inflammatory BMDMs and educated infiltrated BMDMs to a more reparative phenotype involving in multiple biological processes associated with SCI pathology, including immune/inflammation response, neurogenesis, lipid metabolism, oxidative stress, fibrosis formation, and angiogenesis, etc. As an overall effect, hydralazine-treated BMDMs loaden with sp partially rescued neurological function after SCI. It is concluded that hydralazine plays an immunomodulation role of educating pro-inflammatory BMDMs to a more reparative phenotype; and hydralazine-educated BMDMs contribute to hydralazine-induced improvement of neurological function in SCI mice, which provides support for drug and cell treatment options for SCI therapy.

A Meta-analysis of Randomized Controlled Trials Comparing the Efficacy and Safety of Pregabalin and Gabapentin in the Treatment of Postherpetic Neuralgia

OBJECTIVE

To systematically evaluate the clinical efficacy of pregabalin and gabapentin in the treatment of postherpetic neuralgia (PHN), including the difference in pain control and occurrence of adverse reactions.

METHODS

PubMed, MEDLINE, EMBASE, Cochrane Library, and Web of Science databases were searched for randomized controlled trials (RCTs) comparing the efficacy of pregabalin and gabapentin in patients with PHN. Data from studies meeting the inclusion criteria were extracted and the Cochrane Risk of Bias risk assessment tool was used to evaluate the quality of the included studies. Revman 5.3 and Stata17 were used to perform the meta-analysis and to detect publication bias.

RESULTS

A total of 14 RCTs with 3545 patients were included in this study, including 926 in the pregabalin treatment group, 1256 in the gabapentin treatment group, and 1363 in the placebo control group. Pregabalin was better than gabapentin in alleviating pain and improving the global perception of change in pain and sleep (P < 0.05). Gabapentin was associated with a lower incidence of adverse events than pregabalin (P < 0.05). Funnel plot and Begg's and Egger's tests showed no significant publication bias.

CONCLUSION

Pregabalin appears to have a better overall therapeutic effect than gabapentin for patients with PHN, but gabapentin has a lower incidence of adverse reactions and a better safety profile. Clinicians should comprehensively consider patient factors and fully evaluate the advantages and disadvantages of each treatment option to select the most suitable drugs for patient use. Considering the limited quantity and quality of the existing literature, high-quality RCTs are needed to confirm the advantages of pregabalin over gabapentin in the treatment of PHN and guide clinical decision-making.

The mechanism of human neural stem cell secretomes improves neuropathic pain and locomotor function in spinal cord injury rat models: through antioxidant, anti-inflammatory, anti-matrix degradation, and neurotrophic activities

Background

Globally, spinal cord injury (SCI) results in a big burden, including 90% suffering permanent disability, and 60%-69% experiencing neuropathic pain. The main causes are oxidative stress, inflammation, and degeneration. The efficacy of the stem cell secretome is promising, but the role of human neural stem cell (HNSC)-secretome in neuropathic pain is unclear. This study evaluated how the mechanism of HNSC-secretome improves neuropathic pain and locomotor function in SCI rat models through antioxidant, anti-inflammatory, anti-matrix degradation, and neurotrophic activities.

Methods

A proper experimental study investigated 15 Rattus norvegicus divided into normal, control, and treatment groups (30 μL HNSC-secretome, intrathecal in the level of T10, three days post-traumatic SCI). Twenty-eight days post-injury, specimens were collected, and matrix metalloproteinase (MMP)-9, F2-Isoprostanes, tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β, and brain derived neurotrophic factor (BDNF) were analyzed. Locomotor recovery was evaluated via Basso, Beattie, and Bresnahan scores. Neuropathic pain was evaluated using the Rat Grimace Scale.

Results

The HNSC-secretome could improve locomotor recovery and neuropathic pain, decrease F2-Isoprostane (antioxidant), decrease MMP-9 and TNF-α (anti-inflammatory), as well as modulate TGF-β and BDNF (neurotrophic factor). Moreover, HNSC-secretomes maintain the extracellular matrix of SCI by reducing the matrix degradation effect of MMP-9 and increasing the collagen formation effect of TGF-β as a resistor of glial scar formation.

Conclusions

The present study demonstrated the mechanism of HNSC-secretome in improving neuropathic pain and locomotor function in SCI through antioxidant, anti-inflammatory, anti-matrix degradation, and neurotrophic activities.

Prevalence and Determinants of Pain in Spinal Cord Injury During Initial Inpatient Rehabilitation: Data From the Dutch Spinal Cord Injury Database

OBJECTIVE

To describe the prevalence and characteristics of spinal cord injury (SCI)-related pain during initial inpatient rehabilitation and to investigate relationships with demographic and lesion characteristics.

DESIGN

Cohort during inpatient rehabilitation.

SETTING

Eight specialized SCI rehabilitation centers in the Netherlands.

PARTICIPANTS

Patients with newly acquired SCI admitted for inpatient rehabilitation between November 2013 and August 2019 (N=1432).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Presence of pain at admission and discharge. Logistic regression analyses were used to study the prevalence of pain related to sex, age, etiology, completeness, and level of injury.

RESULTS

Data from 1432 patients were available. Of these patients 64.6% were male, mean age was 56.8 years, 59.9% had a nontraumatic SCI, 63.9% were classified as American Spinal Cord Injury Association Impairment Scale (AIS) D and 56.5% had paraplegia. Prevalence of pain was 61.2% at admission (40.6% nociceptive pain [NocP], 30.2% neuropathic pain [NeuP], 5.4% other pain) and 51.5% at discharge (26.0% NocP, 31.4% NeuP, 5.7% other pain). Having NocP at admission was associated with traumatic SCI. AIS B had a lower risk of NocP than AIS D at admission. Having NocP at discharge was associated with female sex and traumatic SCI. AIS C had a lower risk of NocP at discharge than AIS D. Having NeuP at admission was associated with female sex. Having NeuP at discharge was associated with female sex, age younger than 65 years vs age older than 75 years and tetraplegia.

CONCLUSIONS

SCI-related pain is highly prevalent during inpatient rehabilitation. Prevalence of NocP decreased during inpatient rehabilitation, and prevalence of NeuP stayed the same. Different patient and lesion characteristics were related to the presence of SCI-related pain. Healthcare professionals should be aware of these differences in screening patients on presence and development of pain during inpatient rehabilitation.

Prescriptions pour les complications courantes des lésions de la moelle épinière

Objectif

Décrire les modèles de prescriptions dans le cas de 3 complications communes associées à une lésion de la moelle épinière (LME) et proposer aux médecins de famille des stratégies pour optimiser les soins aux patients atteints d’une LME.

Sources de l’information

Les résultats d’une enquête nationale sur l’utilisation des médicaments d’ordonnance par des personnes atteintes d’une LME au Canada et d’une étude longitudinale des complications secondaires liées aux LME.

Message principal

Les fonctions neurologiques et cardiométaboliques altérées chez les patients atteints d’une LME compliquent le choix des régimes pharmacologiques optimaux chez de tels patients. Trois problèmes courants observés en soins primaires chez des patients atteints d’une LME exigent une pharmacothérapie, soit la douleur (traitée chez 57 % des répondants à l’enquête), les spasmes musculaires (54 %) et les infections des voies urinaires récurrentes (43 %). Le contrôle de la douleur peut nécessiter plusieurs médicaments, selon la source ou la nature de la douleur. Certains médicaments d’ordonnance recommandés pour le traitement de la douleur pourraient être sous-utilisés dans cette population, comme l’amitriptyline, tandis que d’autres pourraient être surutilisés chez de tels patients, comme les antibiotiques pour les infections des voies urinaires. La spasticité est souvent liée à un problème sous-jacent, comme la douleur, et le traitement des problèmes concomitants peut donc aussi réduire la spasticité. Il a été observé que des benzodiazépines à courte durée d’action ont été prescrites pour la spasticité à des taux étonnamment élevés, même si elles ne font pas partie du paradigme thérapeutique recommandé. L’étude longitudinale sur les complications secondaires associées aux LME a mené à l’élaboration de pépites exploitables, un outil novateur de transmission des connaissances à l’intention des professionnels des soins primaires.

Conclusion

Dans le but de prodiguer un traitement optimal des patients souffrant d’une LME, les médecins de famille sont encouragés à entamer des communications franches au sujet des médicaments d’ordonnance, y compris sur les aspects liés aux coûts, à la polypharmacie et aux substituts thérapeutiques. Les médecins de famille devraient aussi explorer l’établissement d’une collaboration interprofessionnelle avec des spécialistes des LME et d’autres professionnels de la santé afin d’offrir aux patients des stratégies non pharmacologiques adaptées à leur degré d’activité et à leurs besoins nutritionnels. L’application mobile des pépites exploitables fournit aux médecins de famille des renseignements concis, pratiques et fondés sur des données probantes portant sur les 20 principales préoccupations liées à la santé causées par une LME.

Prescribing for common complications of spinal cord injury

OBJECTIVE

To describe prescribing patterns for 3 common complications associated with spinal cord injury (SCI) and to provide family doctors with strategies for optimizing the care of patients with SCI.

SOURCES OF INFORMATION

Results of a nationwide survey of prescription medication use among people with SCI in Canada and a longitudinal study of secondary complications associated with SCI.

MAIN MESSAGE

Altered neurologic and cardiometabolic function in patients with SCI make it difficult for family physicians to predict optimal medication regimens for these patients. Three common problems seen in primary care among patients with SCI that require pharmacologic treatment are pain (treated in 57% of survey respondents), muscle spasms (54%), and recurrent urinary tract infections (43%). Pain management may require multiple medications, depending on the source or nature of the pain. Some prescription medications recommended for treating pain may be underused in this population, such as amitriptyline, while others may be overused in this population, such as antibiotics for urinary tract infections. Spasticity is often related to an underlying problem such as pain, and treatment of concomitant conditions may also reduce spasticity. Short-acting benzodiazepines were found to have been prescribed for spasticity outside the recommended treatment paradigm at a surprisingly high rate. The longitudinal study of secondary complications associated with SCI led to the development of Actionable Nuggets, an innovative knowledge translation tool for primary care providers.

CONCLUSION

To provide optimal treatment to patients with SCI, family doctors are encouraged to engage in open communication with them about prescription medications, including aspects of cost, polypharmacy, and therapeutic substitutions. Family physicians should also explore interprofessional collaboration with SCI specialists and allied health providers to provide patients with nonpharmacologic strategies tailored to their activity levels and nutritional needs. The Actionable Nuggets mobile app provides family doctors with brief, actionable, evidence-based information on the top 20 health concerns associated with SCI.

Bibliometric analysis of research on gene expression in spinal cord injury

Background

Spinal cord injury (SCI) is a severe disease with motor and sensory function being destroyed, which leads to a poor prognosis and a serious financial burden. It is urgent to figure out the molecular and pathological mechanisms of SCI to develop feasible therapeutic strategies. This article aims to review documents focused on gene expression in SCI and summarize research hotspots and the development process in this field.

Methods

Publications of SCI-related studies from 2000 to 2022 were retrieved from the Web of Science Core Collection database. Biblioshiny was used to evaluate the research performance, core authors, journals and contributed countries, together with trend topics, hotspots in the field, and keyword co-occurrence analysis. Visualized images were obtained to help comprehension.

Results

Among 351 documents, it was found that the number of annual publications increased in general. The most productive country was China, followed by the United States with the highest influence and the most international cooperation. Plos One was the journal of the maximum publications, while Journal of Neuroscience was the most influential one. According to keyword co-occurrence and trend topics analysis, these articles mainly focused on molecular and pathological mechanisms as well as novel therapies for SCI. Neuropathic pain, axonal regeneration and messenger RNA are significant and promising research areas.

Conclusion

As the first bibliometric study focused on gene expression in SCI, we demonstrated the evolution of the field and provided future research directions like mechanisms and treatments of SCI with great innovativeness and clinical value. Further studies are recommended to develop more viable therapeutic methods for SCI.

Coexistence of chronic hyperalgesia and multilevel neuroinflammatory responses after experimental SCI: a systematic approach to profiling neuropathic pain

Background

People with spinal cord injury (SCI) frequently develop neuropathic pain (NP) that worsens disability and diminishes rehabilitation efficacy. Chronic NP is presently incurable due to poor understanding of underlying mechanisms. We hypothesized that multilocus neuroinflammation (NIF) might be a driver of SCI NP, and tested it by investigating whether NP coexisted with central NIF, neurotransmission (NTM), neuromodulation (NML) and neuroplasticity (NPL) changes post-SCI.

Methods

Female Sprague–Dawley rats (230–250 g) with T10 compression or laminectomy were evaluated for physical conditions, coordinated hindlimb functions, neurological reflexes, and mechanical/thermal sensitivity thresholds at 1 day post-injury (p.i.) and weekly thereafter. Eight weeks p.i., central nervous system tissues were histochemically and immunohistochemically characterized for parameters/markers of histopathology and NIF/NTM/NML/NPL. Also analyzed was the correlative relationship between levels of selected biomarkers and thermosensitivity thresholds via statistical linear regression.

Results

SCI impaired sensorimotor functions, altered reflexes, and produced spontaneous pain signs and hypersensitivity to evoked nociceptive, mechanical, and thermal inputs. Only injured spinal cords exhibited neural lesion, microglia/astrocyte activation, and abnormal expression of proinflammatory cytokines, as well as NIF/NTM/NML/NPL markers. Brains of SCI animals displayed similar pathophysiological signs in the gracile and parabrachial nuclei (GrN and PBN: sensory relay), raphe magnus nucleus and periaqueduct gray (RMN and PAG: pain modulation), basolateral amygdala (BLA: emotional-affective dimension of pain), and hippocampus (HPC: memory/mood/neurogenesis). SCI augmented sensory NTM/NPL (GrN and PBN); increased GAD67 (PAG) level; reduced serotonin (RMN) and fear-off neuronal NTR2 (BLA) expressions; and perturbed neurogenesis (HPC).

Conclusion

T10 compression caused chronic hyperalgesia that coexisted with NIF/NTM/NML/NPL responses at multilevel neuroaxis centers. The data have provided multidimensional biomarkers as new mechanistic leads to profile SCI NP for therapeutic/therapy development.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02628-2.

Pharmacological inhibition of the cGAS-STING signaling pathway suppresses microglial M1-polarization in the spinal cord and attenuates neuropathic pain

Neuroinflammation plays a vital role in the development of neuropathic pain and is mediated mainly by microglia. Suppressing microglial M1-polarization attenuates neuropathic pain. Recently, the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway has emerged as a key mediator of inflammation and shows potential in modulating microglial polarization. In this study, we evaluated whether cGAS-STING is a potential therapeutic target. Spared nerve injury (SNI) surgery was conducted in adult male rats to establish a neuropathic pain model. We showed that SNI promoted microglial M1-polarization and induced cGAS-STING pathway activation in the spinal cord. Double-label immunofluorescence assays showed that cGAS-STING activation mainly occurred in neurons and microglia but not astrocytes. We further conducted in vitro experiments using BV-2 microglial cells. The results showed that LPS-induced microglial M1-polarization was accompanied by cGAS-STING pathway activation, but cGAS-STING inhibition by antagonists suppressed LPS-induced microglial M1-polarization. In vivo, we also showed that a cGAS antagonist and a STING antagonist suppressed the microglial M1-polarization and ameliorated the mechanical allodynia induced by SNI. These findings suggested that the cGAS-STING pathway might be a potential therapeutic target for treating neuropathic pain. However, further research is warranted to verify our findings in female rodents.

A scoping review on the effect of cannabis on pain intensity in people with spinal cord injury

CONTEXT

This scoping review examines the current research on the effect of cannabis upon pain intensity in spinal cord injury (SCI) pain. Chronic pain is a significant secondary condition following SCI, and traditional treatments (e.g. opioids, NSAIDs) are often criticized for providing inadequate relief. As a result, there is increasing interest in and use of cannabis and cannabinoid-based medications as an alternative means of pain control.

OBJECTIVE

The purpose of this review was to examine the scientific evidence on the effect of cannabis/cannabinoids upon pain intensity in SCI by mapping the current literature.

METHODS

Two hundred and fifty-two studies were identified by searching electronic databases for articles published through February 2020. In addition, reviewers scanned the reference lists of identified articles and examined clinicaltrials.gov for unpublished data in this area. Title, abstract, and full-text reviews were completed by two independent reviewers. Data extraction was performed by a single reviewer and verified by a second reviewer.

RESULTS

Six articles covering five treatment studies were included. Studies yielded mixed findings likely due to large variability in methodology, including lack of standardized dosing paradigms, modes of use, and duration of trial.

CONCLUSIONS

The current quality and level of evidence is insufficient to draw reliable conclusions of the efficacy of cannabis upon SCI-related pain itensity. We identify specific limitations of past studies and present guidelines for future research.Trial registration: ClinicalTrials.gov identifier: Nct01606202..

Moving Beyond the Neck and Arm: The Pain Experience of People With Degenerative Cervical Myelopathy Who Have Pain

STUDY DESIGN

Cross-sectional internet survey of people living with degenerative cervical myelopathy.

OBJECTIVE

The purpose of this study was to quantify pain distribution, severity, and interference in persons with degenerative cervical myelopathy.

METHODS

Eighty-two participants with degenerative cervical myelopathy were recruited for this internet survey. This survey utilized the Michigan Body Map and brief pain inventory (BPI) to assess anatomical distribution and severity of pain as well as the patient derived modified Japanese Orthopedic Association scale (p-mJOA) for myelopathic severity and SF-36 for measures of health-related quality of life. Internal consistency was evaluated with Cronbach's alpha. Pearson's correlations were assessed with p-mJOA and SF-36. Multivariate analysis of variance was used to determine if history of prior surgery or concomitant pain diagnosis impacted experience of pain.

RESULTS

Michigan body map distribution and brief pain inventory severity and interference were correlated with p-mJOA and SF-36 scores (p < 0.05). Pain was moderate to severe in 78% of participants. Pain was commonly widespread. Pain scales were sufficiently internally consistent (α > 0.9). History of surgery or other pain diagnosis did not impact experience of pain in myelopathy.

CONCLUSIONS

Pain is commonly identifiable in large areas of the body, is frequently moderate to severe in intensity and impacts quality of life and severity of myelopathy in a cohort of individuals with myelopathy who have pain.

Effects of D-Serine and MK-801 on Neuropathic Pain and Functional Recovery in a Rat Model of Spinal Cord Injury

OBJECTIVE

Neuropathic pain is a common secondary complication of spinal cord injury (SCI). N-methyl-D-aspartate (NMDA) receptor activation is critical for hypersensitivity in neuropathic pain. This activation requires the binding of both glutamate and the D-serine co-agonist to the NMDA glycine site. We evaluated the effects of D-serine on neuropathic pain after SCI and explored the underlying molecular mechanisms.

METHODS

Anesthetized rats underwent T9 spinal cord contusion (130 kdyn). D-serine (500 and 1,000 mg/kg) and MK-801 hydrogen maleate (2.0 mg/kg) were injected daily for 2 weeks, starting the day after SCI. Functional outcomes were assessed according to the Basso, Beattie, and Bresnahan scale, while histological outcomes were evaluated based on lesion volume and spared tissue area. Mechanical allodynia and thermal hyperalgesia were evaluated by measuring the withdrawal threshold of a von Frey filament and hot/cold plate latency. Western blotting was performed to determine the expression levels of Trpv1, Nav1.9, calcitonin gene-related peptide (CGRP), and β-actin in damaged tissue.

RESULTS

The withdrawal threshold values and latency of the D-serine group were significantly lower than those of the noninjection group. The MK-801 group showed higher threshold values and latencies than the other groups. Western blotting showed increased Nav1.9 and Trpv1 levels and lower CGRP levels in the D-serine group, whereas the MK-801 group showed the opposite results.

CONCLUSION

D-serine increases neuropathic pain after traumatic SCI by mediating the NMDA receptor. NMDA receptor antagonists alleviate neuropathic pain after traumatic SCI.

Should Non-Pharmacological and Non-Surgical Interventions be Used to Manage Neuropathic Pain in Adults With Spinal Cord Injury? - A Systematic Review

Spinal Cord Injury (SCI) results in a permanent or temporary alteration of the motor, sensory and/or autonomic functions, frequently leading to neuropathic pain. To deal with this comorbidity, several non-pharmacological and non-surgical (NP-NS) interventions have been developed. However, their efficacy is still uncertain. The aim of this study was to systematically synthetize the available evidence assessing the efficacy of NP-NS interventions for treating neuropathic pain in people with SCI. Thus, an electronic search was conducted in five databases (Pubmed, Scopus, Cochrane Central, Web of Science and EBSCO) and trials registry databases, in addition to a manual search strategy to retrieve additional records. The review included randomized controlled trials with adults with SCI, in any stage of the condition. Data on the efficacy of the interventions was narratively synthetized. Once the research was completed, of 4853 identified references, 24 were included with a total of 653 participants with SCI and neuropathic pain, mostly male and with paraplegia. These studies investigated the effect of 13 types of NP-NS interventions with different protocols and methodological limitations. Seven different assessment scales were analyzed, with neuropathic pain being the primary outcome in 21 studies. Such high heterogeneity impaired the conduction of meta-analysis for any of the interventions. Although promising results were found regarding analgesic effect of NP-NS on neuropathic pain in people with SCI, it is not yet possible to safely state that these interventions are in fact effective. Further studies with homogeneous protocols and methodological quality are still needed. PERSPECTIVE: This article presents a review of existing studies on the effectiveness of NP-NS interventions in neuropathic pain in SCI. This synthesis could potentially alert and motivate clinicians to develop studies on this topic, so that interventions can be objectively evaluated and recommendations for an evidence-based practice be created.

Comprehensive phenotyping of cutaneous afferents reveals early-onset alterations in nociceptor response properties, release of CGRP, and hindpaw edema following spinal cord injury

Spinal cord injury (SCI) is a complex syndrome that has profound effects on patient well-being, including the development of medically-resistant chronic pain. The mechanisms underlying SCI pain have been the subject of thorough investigation but remain poorly understood. While the majority of the research has focused on changes occurring within and surrounding the site of injury in the spinal cord, there is now a consensus that alterations within the peripheral nervous system, namely sensitization of nociceptors, contribute to the development and maintenance of chronic SCI pain. Using an ex vivo skin/nerve/DRG/spinal cord preparation to characterize afferent response properties following SCI, we found that SCI increased mechanical and thermal responding, as well as the incidence of spontaneous activity (SA) and afterdischarge (AD), in below-level C-fiber nociceptors 24 hr following injury relative to naïve controls. Interestingly, the distribution of nociceptors that exhibit SA and AD are not identical, and the development of SA was observed more frequently in nociceptors with low heat thresholds, while AD was found more frequently in nociceptors with high heat thresholds. We also found that SCI resulted in hindpaw edema and elevated cutaneous calcitonin gene-related peptide (CGRP) concentration that were not observed in naïve mice. These results suggest that SCI causes a rapidly developing nociceptor sensitization and peripheral inflammation that may contribute to the early emergence and persistence of chronic SCI pain.

Modulation of Solid-State Chemical Stability of Gabapentin by Pyridinecarboxylic Acid

PURPOSE

Gabapentin (GBP) is an anticonvulsant drug with poor chemical stability that is particularly sensitive to heat and mechanical stress, which can lead to intramolecular lactamization. The purpose of this study was to enhance the chemical stability of GBP by cocrystallization with organic acids.

METHOD

Two novel multicomponent crystals, GBP-2,6-pyridinedicarboxylic acid salt (GBP-2,6PDA salt) and GBP-2,5-pyridinedicarboxylic acid cocrystal (GBP-2,5PDA cocrystal) were synthesized and characterized by various solid-state analytical techniques. The degradation behavior of GBP, GBP-2,6PDA salt and GBP-2,5PDA cocrystals were evaluated under thermal and mechanical stresses.

RESULT

Under thermal and mechanical stresses, GBP-2,5PDA cocrystals were found to undergo severer degradation than GBP-2,6PDA salt and neat GBP. GBP-2,6PDA salt exhibited superior chemical stability compared to the others. Furthermore, the crystal structure revealed that the order of atomic distance between the carboxyl group (C7) and amino group (N12) of GBP is as follows: GBP-2,5PDA cocrystal < GBP < GBP-2,6PDA salt, which is consistent with the chemical stability of GBP in different solid forms. Therefore, we believe that the distance between C7 and N12, the reaction active sites leading to dehydrative condensation of GBP, is a key factor determining the chemical stability of GBP in the solid state.

CONCLUSIONS

These results provide a potential method to improve the chemical stability of GBP during the manufacturing process and storage.

Future Treatment of Neuropathic Pain in Spinal Cord Injury: The Challenges of Nanomedicine, Supplements or Opportunities?

Neuropathic pain (NP) is a common chronic condition that severely affects patients with spinal cord injuries (SCI). It impairs the overall quality of life and is considered difficult to treat. Currently, clinical management of NP is often limited to drug therapy, primarily with opioid analgesics that have limited therapeutic efficacy. The persistence and intractability of NP following SCI and the potential health risks associated with opioids necessitate improved treatment approaches. Nanomedicine has gained increasing attention in recent years for its potential to improve therapeutic efficacy while minimizing toxicity by providing sensitive and targeted treatments that overcome the limitations of conventional pain medications. The current perspective begins with a brief discussion of the pathophysiological mechanisms underlying NP and the current pain treatment for SCI. We discuss the most frequently used nanomaterials in pain diagnosis and treatment as well as recent and ongoing efforts to effectively treat pain by proactively mediating pain signals following SCI. Although nanomedicine is a rapidly growing field, its application to NP in SCI is still limited. Therefore, additional work is required to improve the current treatment of NP following SCI.

Effectiveness of Hydrotherapy on Neuropathic Pain and Pain Catastrophization in Patients With Spinal Cord Injury: Protocol for a Pilot Trial Study

Background

Neuropathic pain (NP) is one of the most frequent spinal cord injury (SCI) complications. Pain, quality of life, and functionality are associated and can lead to pain catastrophization. Pharmacological management of patients with NP secondary to SCI is widely known and there is increasing evidence in the area. Nevertheless, nonpharmacological management is not fully elucidated since its efficacy is inconclusive.

Objective

We hypothesize that (1) hydrotherapy is effective in reducing NP secondary to SCI. Additionally, our secondary hypotheses are that (2) hydrotherapy decreases the catastrophization of NP, and that (3) hydrotherapy improves life quality and minimizes the degree of disability, when compared to physical therapy.

Methods

A sample of approximately 20 participants will be randomly assigned to either the intervention (hydrotherapy) or control group (standard physical therapy). Both interventions will be administered twice a week over a 9-week period (18 sessions in total). Primary outcomes are changes in neuropathic pain perception and pain catastrophization. Secondary outcomes are changes in disability and quality of life scores. They will be assessed at baseline and follow-up at 4 weeks after discharge. Validated Spanish language scales that will be used are the following: Numerical Pain Rating Scale, Pain Catastrophization, Health-related Quality of life, and the World Health Organization’s Disability Assessment Schedule 2.0. Generalized mixed linear models will be used for comparing baseline and postintervention means of each group and their differences, together with 95% CIs and P values. A P value of less than .05 will be considered significant.

Results

Recruitment began in April 2019, and we recruited the last participants by December 2019, with 10 individuals assigned to hydrotherapy and 8 to physical therapy (control). Results from this study will be disseminated via scientific publication, in ClinicalTrials.gov, and in national and international conferences in the latter half of 2022.

Conclusions

This trial will explore the effects of hydrotherapy on neuropathic pain, together with functionality and quality of life, in patients with SCI. Furthermore, this study aims to evaluate these therapeutic modalities, including perception variables, and mental processes, which may affect the clinical condition and rehabilitation outcomes in these patients. Hydrotherapy is likely to be a safe, efficient, and cost-effective alternative to the current standard of care for NP secondary to SCI, with comparable results between the two.

Trial Registration

ClinicalTrials.gov NCT04164810; https://clinicaltrials.gov/ct2/show/NCT04164810

International Registered Report Identifier (IRRID)

DERR1-10.2196/37255

Non-opioid pharmacologic treatment of chronic spinal cord injury-related pain

Purpose: Spinal cord injury-related pain is often a severe debilitating condition that adversely affects the patient's physical health, psychological wellbeing and quality of life. Opioid medications have historically been prescribed to this population with great frequency. As opioid abuse disorder becomes an ever-worsening public health issue, more attention must be placed upon non-opioid options. This paper reviews non-opioid medications to be considered when treating spinal cord injury-related pain. The pertinent literature is reviewed, and the advantages and pitfalls of various medication options are discussed in the complicated context of the individual with a spinal cord injury.Methods: Peer-reviewed journal articles and medication package insert data are reviewed.Results:. The non-opioid medications with the greatest evidence for efficacy in the treatment of chronic spinal cord injury-related pain are drawn from the antiepileptic drug and antidepressant categories though the specific selection must be nuanced to the particular individual patient. More research is required to understand the role of calcitonin, lithium, and marijuana in treating spinal cord injury-related pain.Conclusions: The complex clinical situation of each individual patient must be weighed against the risks and benefits of each medication, as reviewed in this paper, to determine the ideal treatment strategy for chronic spinal cord injury-related pain.

Neuroprotective effects of Alda-1 mitigate spinal cord injury in mice: involvement of Alda-1-induced ALDH2 activation-mediated suppression of reactive aldehyde mechanisms

Spinal cord injury (SCI) is associated with high production and excessive accumulation of pathological 4-hydroxy-trans-2-nonenal (4-HNE), a reactive aldehyde, formed by SCI-induced metabolic dysregulation of membrane lipids. Reactive aldehyde load causes redox alteration, neuroinflammation, neurodegeneration, pain-like behaviors, and locomotion deficits. Pharmacological scavenging of reactive aldehydes results in limited improved motor and sensory functions. In this study, we targeted the activity of mitochondrial enzyme aldehyde dehydrogenase 2 (ALDH2) to detoxify 4-HNE for accelerated functional recovery and improved pain-like behavior in a male mouse model of contusion SCI. N-(1,3-benzodioxol-5-ylmethyl)-2,6-dichlorobenzamide (Alda-1), a selective activator of ALDH2, was used as a therapeutic tool to suppress the 4-HNE load. SCI was induced by an impactor at the T9–10 vertebral level. Injured animals were initially treated with Alda-1 at 2 hours after injury, followed by once-daily treatment with Alda-1 for 30 consecutive days. Locomotor function was evaluated by the Basso Mouse Scale, and pain-like behaviors were assessed by mechanical allodynia and thermal algesia. ALDH2 activity was measured by enzymatic assay. 4-HNE protein adducts and enzyme/protein expression levels were determined by western blot analysis and histology/immunohistochemistry. SCI resulted in a sustained and prolonged overload of 4-HNE, which parallels with the decreased activity of ALDH2 and low functional recovery. Alda-1 treatment of SCI decreased 4-HNE load and enhanced the activity of ALDH2 in both the acute and the chronic phases of SCI. Furthermore, the treatment with Alda-1 reduced neuroinflammation, oxidative stress, and neuronal loss and increased adenosine 5′-triphosphate levels stimulated the neurorepair process and improved locomotor and sensory functions. Conclusively, the results provide evidence that enhancing the ALDH2 activity by Alda-1 treatment of SCI mice suppresses the 4-HNE load that attenuates neuroinflammation and neurodegeneration, promotes the neurorepair process, and improves functional outcomes. Consequently, we suggest that Alda-1 may have therapeutic potential for the treatment of human SCI. Animal procedures were approved by the Institutional Animal Care and Use Committee (IACUC) of MUSC (IACUC-2019-00864) on December 21, 2019.

Pregabalin and Gabapentin in Patients with Spinal Cord Injury-Related Neuropathic Pain: A Network Meta-Analysis

INTRODUCTION

This study was performed to explore the efficacy and safety of pregabalin and gabapentin in patients with spinal cord injury (SCI)-induced neuropathic pain to determine which treatment is most suitable for such patients.

METHODS

We searched the PubMed, MEDLINE, Embase, and Cochrane Library databases from database inception to August 31, 2020. The quality of the included studies was assessed. We selected the average pain intensity after treatment and the proportion of patients who discontinued treatment because of adverse effects as the outcome indicators for efficacy and safety, respectively. Statistical analyses were performed using Stata, v16.0, and RevMan, v5.3, software.

RESULTS

We included eight randomized controlled trials that examined four interventions (pregabalin, gabapentin, carbamazepine, and amitriptyline). Based on the average pain intensity after treatment, the efficacy order from highest to lowest was pregabalin, gabapentin, amitriptyline, carbamazepine, and placebo. Based on the proportion of patients who discontinued treatment because of adverse effects, the order from highest to lowest was pregabalin, amitriptyline, carbamazepine, gabapentin, and placebo. In addition, five studies reported the overall incidence of treatment-related adverse effects for two interventions (pregabalin and gabapentin). According to the pooled analysis of these studies, the order for the overall incidence of treatment-related adverse effects from highest to lowest was pregabalin, gabapentin, and placebo.

CONCLUSIONS

This study revealed that for patients with SCI-related neuropathic pain, pregabalin was the most effective for relieving pain, whereas gabapentin performed better in aspects associated with drug therapy-related safety.

Aging and miR-155 in mice influence survival and neuropathic pain after spinal cord injury

Spinal cord injury (SCI) elicits chronic pain in 65% of individuals. In addition, SCI afflicts an increasing number of aged individuals, and those with SCI are predisposed to shorter lifespan. Our group previously identified that deletion of the microRNA miR-155 reduced neuroinflammation and locomotor deficits after SCI. Here, we hypothesized that aged mice would be more susceptible to pain symptoms and death soon after SCI, and that miR-155 deletion would reduce pain symptoms in adult and aged mice and improve survival. Adult (2 month-old) and aged (20 month-old) female wildtype (WT) and miR-155 knockout (KO) mice received T9 contusion SCI. Aged WT mice displayed reduced survival and increased autotomy - a symptom of spontaneous pain. In contrast, aged miR-155 KO mice after SCI were less susceptible to death or spontaneous pain. Evoked pain symptoms were tested using heat (Hargreaves test) and mechanical (von Frey) stimuli. At baseline, aged mice showed heightened heat sensitivity. After SCI, adult and aged WT and miR-155 KO mice all exhibited heat and mechanical hypersensitivity at all timepoints. miR-155 deletion in adult (but not aged) mice reduced mechanical hypersensitivity at 7 and 14 d post-SCI. Therefore, aging predisposes mice to SCI-elicited spontaneous pain and expedited mortality. miR-155 deletion in adult mice reduces evoked pain symptoms, and miR-155 deletion in aged mice reduces spontaneous pain and expedited mortality post-SCI. This study highlights the importance of studying geriatric models of SCI, and that inflammatory mediators such as miR-155 are promising targets after SCI for improving pain relief and longevity.

Peripheral Immune Dysfunction: A Problem of Central Importance after Spinal Cord Injury

Simple Summary

Spinal cord injury can result in an increased vulnerability to infections, but until recently the biological mechanisms behind this observation were not well defined. Immunosuppression and concurrent sustained peripheral inflammation after spinal cord injury have been observed in preclinical and clinical studies, now termed spinal cord injury-induced immune depression syndrome. Recent research indicates a key instigator of this immune dysfunction is altered sympathetic input to lymphoid organs, such as the spleen, resulting in a wide array of secondary effects that can, in turn, exacerbate immune pathology. In this review, we discuss what we know about immune dysfunction after spinal cord injury, why it occurs, and how we might treat it.

Abstract

Individuals with spinal cord injuries (SCI) exhibit increased susceptibility to infection, with pneumonia consistently ranking as a leading cause of death. Despite this statistic, chronic inflammation and concurrent immune suppression have only recently begun to be explored mechanistically. Investigators have now identified numerous changes that occur in the peripheral immune system post-SCI, including splenic atrophy, reduced circulating lymphocytes, and impaired lymphocyte function. These effects stem from maladaptive changes in the spinal cord after injury, including plasticity within the spinal sympathetic reflex circuit that results in exaggerated sympathetic output in response to peripheral stimulation below injury level. Such pathological activity is particularly evident after a severe high-level injury above thoracic spinal cord segment 6, greatly increasing the risk of the development of sympathetic hyperreflexia and subsequent disrupted regulation of lymphoid organs. Encouragingly, studies have presented evidence for promising therapies, such as modulation of neuroimmune activity, to improve regulation of peripheral immune function. In this review, we summarize recent publications examining (1) how various immune functions and populations are affected, (2) mechanisms behind SCI-induced immune dysfunction, and (3) potential interventions to improve SCI individuals’ immunological function to strengthen resistance to potentially deadly infections.

Pain Reduction after Short Exposure to Virtual Reality Environments in People with Spinal Cord Injury

Emerging literature suggests that virtual reality (VR) may be a viable therapy for neuropathic pain (NP). This pilot study aimed to investigate the immediate effect of VR in reducing NP in people with spinal cord injury (SCI). Eight individuals with chronic NP after SCI were recruited and underwent consecutive exposure to scenery and somatic virtual environments (VE). The numeric rating scale (NRS) was used to assess pain before and after exposure to each VE. The Immersive Tendencies Questionnaire (ITQ) and Presence Questionnaire (UQO-PQ) were used to investigate the interaction between reported pain relief post-intervention with immersion and presence. There was a significant reduction in pain levels (5.1 ± 0.4, mean ± SEM) after short exposure to the scenery (3.1 ± 0.7, p = 0.04) and somatic VE (3.0 ± 0.7, p = 0.04), with no difference between intervention types (p = 0.56). There was a statistically significant negative correlation between the total ITQ score and the change in NRS after the scenery VR intervention (r_s = 0.743, p = 0.035). PQ scores showed no significant correlation with changes in pain following either intervention type. We found that short-term exposure to VR environments results in a reduction in chronic NP intensity in people with SCI.

Acute spinal cord injury: Pathophysiology and pharmacological intervention (Review)

Spinal cord injury (SCI) is one of the most debilitating of all the traumatic conditions that afflict individuals. For a number of years, extensive studies have been conducted to clarify the molecular mechanisms of SCI. Experimental and clinical studies have indicated that two phases, primary damage and secondary damage, are involved in SCI. The initial mechanical damage is caused by local impairment of the spinal cord. In addition, the fundamental mechanisms are associated with hyperflexion, hyperextension, axial loading and rotation. By contrast, secondary injury mechanisms are led by systemic and cellular factors, which may also be initiated by the primary injury. Although significant advances in supportive care have improved clinical outcomes in recent years, a number of studies continue to explore specific pharmacological therapies to minimize SCI. The present review summarized some important pathophysiologic mechanisms that are involved in SCI and focused on several pharmacological and non‑pharmacological therapies, which have either been previously investigated or have a potential in the management of this debilitating injury in the near future.

Amantadine prevented hypersensitivity and decreased oxidative stress by NMDA receptor antagonism after spinal cord injury in rats

BACKGROUND

Neuropathic pain (NP) after spinal cord injury (SCI) is a disabling condition, without an effective treatment. Hyperexcitability of N-methyl-D-aspartate (NMDA) receptors and oxidative stress have been reported to be associated with pain development. Amantadine, an NMDA receptor antagonist, has been proposed as a potential therapy for NP. However, its use has not been tested for NP after SCI.

METHODS

To produce SCI, 120 female Wistar rats were used, a contusion injury to the T10 and T12 thoracic vertebrae was performed from heights of 6.25 mm and 12.5 mm. Nociceptive behaviour, was evaluated with the use of von Frey filaments for 31 days. The final products of lipid peroxidation (LP) and concentration of reduced glutathione (GSH) in the injured tissue were quantified by fluorescence spectrophotometry. The antinociceptive effect of the acute (15 days after the injury) and chronic (once daily for three days immediately after the injury) with amantadine (6.25-50 mg/Kg. I.p.) was determined. Finally, the LP and GSH were quantified in the injured tissue.

RESULTS

Acute treatment with amantadine reduced nociceptive behaviour. Concomitantly, LP was decreased by Amantadine treatment while GSH increased in the injured tissue. Similar effects were observed with chronic treatment with amantadine.

CONCLUSIONS

Data from this study suggested that the antinociceptive effects of amantadine treatment are modulated through oxidative stress and excitotoxicity reduction associated with N-methyl-D-aspartate receptors activation.

SIGNIFICANCE

This study suggests that acute treatment with amantadine decreases hypersensitivity threshold and frequency of hypersensitivity response in a dose-dependent manner, in rats with SCI, by decreasing oxidative stress. Since amantadine is an easily accessible drug and has fewer adverse effects than current treatments for hypersensitivity threshold and frequency of hypersensitivity response, amantadine could represent a safe and effective therapy for the treatment of neuropathic pain. However, further research is required to provide evidence of the effectiveness and feasibility.

Topical Capsaicin for the Treatment of Neuropathic Pain

BACKGROUND

Neuropathic pain (NP) is an egregious problem worldwide. Due to the side-effects of oral drugs, drugs delivered directly to the affected area of pain are preferred.

OBJECTIVE

Capsaicin, a chemical compound isolated from chili peppers, is used as an analgesic in topical ointments and dermal patches to alleviate pain. Objective of the study is to review the application and functionality of topical capsaicin in treatment of neuropathic pain.

DATA SOURCES

To systematically review capsaicin's functions on NP, we retrieved articles from the PubMed database published in the last ten years.

STUDY ELIGIBILITY CRITERIA

The inclusion criteria were capsaicin and the use of capsaicin for the treatment of NP; on the other hand, articles were excluded according to the mentioned criteria such as abstracts, articles written in any language other than English, incomplete articles, and conference papers.

PARTICIPANTS AND INTERVENTIONS

Out of 265 articles, 108 articles were selected after filtering through the inclusion and exclusion criteria. The data and knowledge currently existing for capsaicin treatment in NP are summarized.

RESULTS

This review indicates that capsaicin effectively improves NP treatment without affecting the motor and large nerve fibres involved in sensory function. Transient receptor potential channel vanilloid type 1 (TRPV1) is the capsaicin receptor expressed in central and peripheral terminals of a sensitive primary nerve cell. Conclusions and implications of key findings: Topical capsaicin has a sensible safety profile and is effective in reducing NP. Therefore, studies over the last decade suggest that capsaicin might be a potential drug for NP treatment.