Human dorsal root ganglion pulsed radiofrequency treatment modulates cerebrospinal fluid lymphocytes and neuroinflammatory markers in chronic radicular pain

Dorsal root ganglion-pulsed neuromodulation radiofrequency treatment has significant clinical efficacy in chronic spinal-origin pain, bringing noticeable improvement in symptoms and sleep quality for patients

BACKGROUND

Chronic spinal-origin pain poses a substantial clinical challenge, prompting the investigation of novel treatment modalities. This study aims to evaluate the potential application of spinal nerve dorsal root ganglion (DRG) radiofrequency treatment in addressing chronic spinal-origin pain.

METHODS

The study encompassed patients undergoing treatment for chronic spinal-origin pain, with a particular focus on those experiencing pain localized in specific regions. Inclusion criteria comprised patients with conditions such as a herniated intervertebral disc or foraminal stenosis leading to compression of descending or exiting nerve roots, accompanied by reported radicular pain in the lower limb.

RESULTS

There was no significant difference in comparability between the two groups (p > 0.05). The clinical effective rate in the study group was significantly higher than that in the control group (p < 0.05). The VAS scores of the study group at 2 weeks and 1 month after treatment were significantly lower than those of the control group (p < 0.05). The PSQI index of the study group after treatment was significantly lower than that of the control group (p < 0.05). There was no significant difference in the incidence of complications between the two groups (p > 0.05).

CONCLUSION

Spinal nerve DRG radiofrequency treatment has significant clinical efficacy in chronic spinal-origin pain, bringing noticeable improvement in symptoms and sleep quality for patients. The occurrence of complications is relatively low, and it can be reduced through strict operational standards and preoperative and postoperative management. However, caution should be exercised in its widespread application, but it is worthy of broad clinical use.

Pulsed radiofrequency on DRG inhibits hippocampal neuroinflammation by regulating spinal GRK2/p38 expression and enhances spinal autophagy to reduce pain and depression in male rats with spared nerve injury

Evidence indicates that microglial G protein-coupled receptor kinase 2 (GRK2) is a key regulator of the transition from acute to chronic pain mediated by microglial products via the p38 mitogen-activated protein kinase (MAPK) pathway in the spinal cord dorsal horn (SCDH). Increasing studies have shown that autophagic dysfunction in the SCDH and neuroinflammation in the hippocampus underlie NeP. However, whether GRK2/p38MAPK and autophagic flux in the SCDH and hippocampal neuroinflammation are involved in NeP and depression comorbidity has not been determined. Here, we explored the effects of high-voltage pulsed radiofrequency (PRF) (85 V-PRF; HV-PRF) to the dorsal root ganglion (DRG) on pain phenotypes in Wistar male rats with spared nerve injury (SNI) and the underlying mechanisms. The exacerbation of pain phenotypes was markedly relieved by PRF-DRG. The SNI-induced reduction in GRK2 expression, elevation of p-p38 MAPK levels in the SCDH, and increase in IL-1β and TNF-α levels in the hippocampus were reversed by PRF, which was accompanied by an increase in autophagic flux in spinal microglia. The beneficial effect of 85 V-PRF was superior to that of 45 V-PRF. In addition, the improvements elicited by 85 V-PRF were reversed by intrathecal injection of GRK2 antisense oligonucleotide, and these changes were accompanied by GRK2 downregulation and p-p38 upregulation in the SCDH, increased pro-inflammatory factor levels in the hippocampus, and excessive autophagy in spinal microglia. In conclusion, our data indicate that the application of HV-PRF to the DRG could serve as an excellent therapeutic technique for regulating neuroimmunity and neuroinflammation to relieve pain phenotypes.

Pulsed Radiofrequency 2 Hz Preserves the Dorsal Root Ganglion Neuron Physiological Ca2+ Influx, Cytosolic ATP Level, Δψm, and pERK Compared to 4 Hz: An Insight on the Safety of Pulsed Radiofrequency in Pain Management

Background

Pulsed radiofrequency (PRF) is beneficial for radicular pain and is commonly administered at pulse frequencies of 2 or 4 Hz. However, its effects on healthy neurons have not yet been widely studied. This study aims to determine the effect of PRF at 2 Hz and 4 Hz on the physiology of healthy dorsal root ganglion (DRG) neurons.

Methods

An in vitro experimental study was conducted using DRG neuron cultures divided into three groups. Control cells received no treatment, one cell group received 20 ms 2 Hz PRF for 360 s, and one cell group received a 4 Hz PRF 10 ms pulse for 360 s with similar energy. Ca2+ influx, mitochondrial membrane potential (Δψm), cytosolic Adenosine triphosphate (ATP), and phosphorylated extracellular signal-regulated kinase (pERK) levels were measured. The data were analyzed using the One-Way ANOVA variance with α=5%.

Results

DRG neurons exposed to PRF 2 Hz did not experience a significant change in Ca2+ influx, whereas PRF 4 Hz caused a significant decrease in Ca2+ influx compared to the basal level. PRF at 2 Hz did not cause a change in Δψm, whereas PRF at 4 Hz caused a significant decrease in Δψm (p<0.05). Both 2 and 4 Hz PRF resulted in a significant elevation in cytosolic ATP concentration, but the 2 Hz PRF had a higher cytosolic ATP than the 4 Hz group (p<0.05). Both 2 and 4 Hz did not show a significant difference in pERK intensity with respect to the control (p>0.05), indicating that there was no significant neuron activation.

Conclusion

Both frequencies did not significantly activate DRG neurons, but with similar energy delivery, PRF 2 Hz preserved the physiological properties of healthy neurons better than PRF 4 Hz did. A 2 Hz PRF is the preferred frequency in clinical applications for neuron-targeted therapy.

Elucidating the Mechanisms of Pulsed Radiofrequency for Pain Treatment

Pulsed radiofrequency is a well-documented treatment option for multiple painful conditions where pulses of energy are delivered close to neural elements. Since its earliest adoption, this technique has gained increasing acceptance as a minimally invasive procedure, and new applications are evolving. Studies have shown microscopic and biochemical changes that reflect beneficial effects; however, the exact mechanism of action is not yet completely understood. To redress this paucity, 11,476 articles of scientific relevance published between 1980 and November 2022 were mined through a search of the PubMed database, arriving at 49 studies both in animals and humans. In general, the experimental studies examined have shown that pulsed radiofrequency induces multiple changes with antinociceptive and neuromodulatory effects. These modifications include changes in neural and glial cells, synaptic transmission, and perineural space. Studies also reveal that pulsed radiofrequency regulates inflammatory responses, cellular signaling proteins, and the expression of genes related to pain transmission, acting in biological processes in structures such as myelin, mitochondria, axons, glial cells, connective tissue, regulation of proteins, ion channels, and neurotransmitters.

Pain-resolving immune mechanisms in neuropathic pain

Interactions between the immune and nervous systems are of central importance in neuropathic pain, a common and debilitating form of chronic pain caused by a lesion or disease affecting the somatosensory system. Our understanding of neuroimmune interactions in pain research has advanced considerably. Initially considered as passive bystanders, then as culprits in the pathogenesis of neuropathic pain, immune responses in the nervous system are now established to underpin not only the initiation and progression of pain but also its resolution. Indeed, immune cells and their mediators are well-established promoters of neuroinflammation at each level of the neural pain pathway that contributes to pain hypersensitivity. However, emerging evidence indicates that specific subtypes of immune cells (including antinociceptive macrophages, pain-resolving microglia and T regulatory cells) as well as immunoresolvent molecules and modulators of the gut microbiota-immune system axis can reduce the pain experience and contribute to the resolution of neuropathic pain. This Review provides an overview of the immune mechanisms responsible for the resolution of neuropathic pain, including those involved in innate, adaptive and meningeal immunity as well as interactions with the gut microbiome. Specialized pro-resolving mediators and therapeutic approaches that target these neuroimmune mechanisms are also discussed.

Involvement of interferon gamma signaling in spinal trigeminal caudal subnucleus astrocyte in orofacial neuropathic pain in rats with infraorbital nerve injury

Background: Trigeminal nerve injury causes orofacial pain that can interfere with activities of daily life. However, the underlying mechanism remains unknown, and the appropriate treatment has not been established yet. This study aimed to examine the involvement of interferon gamma (IFN-γ) signaling in the spinal trigeminal caudal subnucleus (Vc) in orofacial neuropathic pain. Methods: Infraorbital nerve (ION) injury (IONI) was performed in rats by partial ION ligation. The head-withdrawal reflex threshold (HWT) to mechanical stimulation of the whisker pad skin was measured in IONI or sham rats, as well as following a continuous intracisterna magna administration of IFN-γ and a mixture of IFN-γ and fluorocitrate (inhibitor of astrocytes activation) in naïve rats, or an IFN-γ antagonist in IONI rats. The IFN-γ receptor immunohistochemistry and IFN-γ Western blotting were analyzed in the Vc after IONI or sham treatment. The glial fibrillary acid protein (GFAP) immunohistochemistry and Western blotting were also analyzed after administration of IFN-γ and the mixture of IFN-γ and fluorocitrate. Moreover, the change in single neuronal activity in the Vc was examined in the IONI, sham, and IONI group administered IFN-γ antagonist. Results: The HWT decreased after IONI. The IFN-γ and IFN-γ receptor were upregulated after IONI, and the IFN-γ receptor was expressed in Vc astrocytes. IFN-γ administration decreased the HWT, whereas the mixture of IFN-γ and fluorocitrate recovered the decrement of HWT. IFN-γ administration upregulated GFAP expression, while the mixture of IFN-γ and fluorocitrate recovered the upregulation of GFAP expression. IONI significantly enhanced the neuronal activity of the mechanical-evoked responses, and administration of an IFN-γ antagonist significantly inhibited these enhancements. Conclusions: IFN-γ signaling through the receptor in astrocytes is a key mechanism underlying orofacial neuropathic pain associated with trigeminal nerve injury. These findings will aid in the development of therapeutics for orofacial neuropathic pain.

Propensity score matching comparing short-term nerve electrical stimulation to pulsed radiofrequency for herpes zoster-associated pain: A retrospective study

BACKGROUND

Zoster-associated pain (ZAP) is notoriously difficult to treat. Pulsed radiofrequency (PRF) and short-term nerve electrical stimulation (st-NES) have been proven effective treatments for ZAP. However, it is still unclear which technique provides improved analgesia in ZAP. This study is based on a large-scale, long-term follow-up to evaluate the efficacy and safety between st-NES and PRF.

MATERIALS AND METHODS

All eligible ZAP patients treated with st-NES or PRF in our department were enrolled. Cohorts were divided into the st-NES group and the PRF group. A 1:1 ratio propensity score matching (PSM) was used to balance the baseline characteristics. The PS-matched cohort was adopted to investigate the efficacy and safety of the two treatments. The ordinal regression analysis was performed to determine the variables affecting the treatment effect of ZAP.

RESULTS

A total of 226 patients were included after PSM. The numerical rating scale (NRS) scores in st-NES and PRF groups considerably reduced compared to baseline levels after treatment. The NRS scores in the st-NES group were obviously lower than those in the PRF group at discharge, 1, 3, 6, 12, and 24 months. During the follow-up period, the NRS reduction rate remained higher in the st-NES group than in the PRF group (P < 0.01). The dosage of medication, Pittsburgh Sleep Quality Index (PSQI) score, and the number of patients with aggravated pain after discharge in the st-NES group were significantly less than in the PRF group after treatment.

CONCLUSION

Short-term nerve electrical stimulation has been shown to be more advantageous than PRF for pain relief and quality of life improvement for ZAP patients.

Unbiased immune profiling reveals a natural killer cell-peripheral nerve axis in fibromyalgia

ABSTRACT

The pathophysiology of fibromyalgia syndrome (FMS) remains elusive, leading to a lack of objective diagnostic criteria and targeted treatment. We globally evaluated immune system changes in FMS by conducting multiparametric flow cytometry analyses of peripheral blood mononuclear cells and identified a natural killer (NK) cell decrease in patients with FMS. Circulating NK cells in FMS were exhausted yet activated, evidenced by lower surface expression of CD16, CD96, and CD226 and more CD107a and TIGIT. These NK cells were hyperresponsive, with increased CCL4 production and expression of CD107a when co-cultured with human leukocyte antigen null target cells. Genetic and transcriptomic pathway analyses identified significant enrichment of cell activation pathways in FMS driven by NK cells. Skin biopsies showed increased expression of NK activation ligand, unique long 16-binding protein, on subepidermal nerves of patients FMS and the presence of NK cells near peripheral nerves. Collectively, our results suggest that chronic activation and redistribution of circulating NK cells to the peripheral nerves contribute to the immunopathology associated with FMS.

Radiofrequency Ablation in Cooled Monopolar or Conventional Bipolar Modality Yields More Beneficial Short-Term Clinical Outcomes Versus Other Treatments for Knee Osteoarthritis: A Systematic Review and Network Meta-Analysis of Randomized Controlled Trials

PURPOSE

To evaluate various radiofrequency ablation (RFA) treatments for knee osteoarthritis (OA) and determine the best modality, target, number of electrodes, and image guidance for improving knee pain and function.

METHODS

Electronic databases were searched for randomized controlled trials (RCTs) comparing the efficacy of RFA treatments for knee OA from inception up to September 30, 2021. The primary outcome was the visual analog scale (VAS), and the secondary outcome was the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Bayesian network meta-analysis was performed to synthesize the mean difference (MD) and rank the comparative effectiveness of treatments.

RESULTS

A total of 21 eligible RCTs (from 2011 to 2021, involving 1,818 patients) with 8 RFA treatments, 6 intra-articular injections, NSAIDS, exercise, and placebo were assessed. Conventional bipolar genicular nerve RFA (GNRFA) had the greatest net benefit on the VAS at 6 months (MD, -5.5; 95% confidence interval [CI], -4.3 to -6.7; SUCRA, .98). And cooled monopolar GNRFA had the greatest net benefit on the WOMAC at 6 months (MD, -33; 95% CI, -37 to -29; SUCRA, .99). In conventional and pulsed modalities, bipolar RFA was associated with a significant decrease in VAS and WOMAC than monopolar RFA. Combining pulsed intra-articular RFA and platelet-rich plasma injection had no additional positive effects on VAS or WOMAC at 3 months.

CONCLUSIONS

RFA is effective in improving both knee pain and function in patients with OA, at least in the short term (6 months). Patients respond better to the cooled modality than the conventional and pulsed modalities. Bipolar is more effective than monopolar for improving pain and function in conventional and pulsed modalities. Fluoroscopy and ultrasound guidance showed no differences in improving pain and function. The effectiveness of RFA in cooled modality using bipolar or in combination with various intra-articular injections remains to be compared.

LEVEL OF EVIDENCE

II, systematic review and meta-analysis of Level I and II studies.

Safety of Conventional and Pulsed Radiofrequency Lesions of the Dorsal Root Entry Zone Complex (DREZC) for Interventional Pain Management: A Systematic Review

Study Design

Systematic literature review.

Objective

The goal of this systematic review is to assess the clinical safety and potential complications of conventional and pulsed radiofrequency ablations targeting dorsal root entry zone complex (DREZC) components in the treatment of chronic pain.

Background

There is a growing popularity for the use of radiofrequency ablation (RFA) techniques targeting DREZC components by pain management physicians for an increasing variety of indications. To date, we lack a systematic review to describe the safety and the type of complications associated with these procedures.

Methods

This was a systematic literature review. This systematic search was limited to peer-reviewed literature using “radiofrequency ablation” as a search keyword using PubMed’s database for manuscripts published between inception and December 2020. Abstracts that involved the application of radiofrequency currents, of any modality, to DREZC components for the treatment of pain were included for full-text review. Search was limited to original data describing clinical outcomes following RFA performed for pain indications only, involving the DREZC components outlined above, in human subjects, and written in English. The primary outcomes were complications associated with conventional RFA and pulsed radiofrequency ablation (PRF). Complications were categorized as type 1 (persistent neurological deficits or other serious adverse events, defined as any event that resulted in permanent of prolonged injury; type 2 (transient neuritis or neurological deficits, or other non-neurological non-minor adverse event); type 3 (minor adverse events (e.g., headache, soreness, bruising, etc.).

Results

Of the 62 selected manuscripts totaling 3157 patients, there were zero serious adverse events or persistent neurological deficits reported. A total of 36 (1.14%) transient neurological deficits, cases of transient neuritis, or non-minor adverse events like uncomplicated pneumothorax were reported. A total of 113 (3.58%) minor adverse events were reported (bruising, transient site soreness, headache).

Conclusions

This systematic review indicates that the use of RFA lesion of the DREZC for interventional pain management is very safe. There were no serious adverse effects with a sizable sample of randomized controlled trial (RCT), prospective observational, and retrospective studies.

The role of T-lymphocytes in neuropathic pain initiation, development of chronicity and treatment

Ongoing research has strongly suggested the role the immune system plays in the pathogenesis of neuropathic pain. T cells appear to be one of the main regulators of the immune system with many mediators appearing to promote or suppress pain resolution. Limited effective therapies are available for treatment of neuropathic pain. Treatments available appear to modulate specific T cell with altered ratios present 3 months post treatment and parallels clinical improvement. This further supports the neuro-immune basis for neuropathic pain chronicity. Identification of novel immune mediators involved in pain development may suggest new target areas in treatment.

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Neuroimmunity plays a significant role in neuropathic pain pathogenesis neuropathic pain.

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Immune mediators contribute to promotion, suppression or resolution of neuropathic pain.

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Clinical studies in humans are lacking, most research available is pre-clinical or animal-based.

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Evidence-based therapies for treatment of neuropathic pain demonstrate alteration in T cell phenotype and behavior post therapy.

Regulatory T-cells inhibit microglia-induced pain hypersensitivity in female mice

Peripheral nerve injury-induced neuropathic pain is a chronic and debilitating condition characterized by mechanical hypersensitivity. We previously identified microglial activation via release of colony-stimulating factor 1 (CSF1) from injured sensory neurons as a mechanism contributing to nerve injury-induced pain. Here, we show that intrathecal administration of CSF1, even in the absence of injury, is sufficient to induce pain behavior, but only in male mice. Transcriptional profiling and morphologic analyses after intrathecal CSF1 showed robust immune activation in male but not female microglia. CSF1 also induced marked expansion of lymphocytes within the spinal cord meninges, with preferential expansion of regulatory T-cells (Tregs) in female mice. Consistent with the hypothesis that Tregs actively suppress microglial activation in females, Treg deficient (Foxp3^DTR) female mice showed increased CSF1-induced microglial activation and pain hypersensitivity equivalent to males. We conclude that sexual dimorphism in the contribution of microglia to pain results from Treg-mediated suppression of microglial activation and pain hypersensitivity in female mice.

Mechanistic Insight into the Effects of Curcumin on Neuroinflammation-Driven Chronic Pain

Chronic pain is a persistent and unremitting condition that has immense effects on patients' quality of life. Studies have shown that neuroinflammation is associated with the induction and progression of chronic pain. The activation of microglia and astrocytes is the major hallmark of spinal neuroinflammation leading to neuronal excitability in the projection neurons. Excessive activation of microglia and astrocytes is one of the major contributing factors to the exacerbation of pain. However, the current chronic pain treatments, mainly by targeting the neuronal cells, remain ineffective and unable to meet the patients' needs. Curcumin, a natural plant product found in the Curcuma genus, improves chronic pain by diminishing the release of inflammatory mediators from the spinal glia. This review details the role of curcumin in microglia and astrocytes both in vitro and in vivo and how it improves pain. We also describe the mechanism of curcumin by highlighting the major glia-mediated cascades in pain. Moreover, the role of curcumin on inflammasome and epigenetic regulation is discussed. Furthermore, we discuss the strategies used to improve the efficacy of curcumin. This review illustrates that curcumin modulating microglia and astrocytes could assure the treatment of chronic pain by suppressing spinal neuroinflammation.

Alpha lipoic acid with pulsed radiofrequency in treatment of chronic lumbosacral radicular pain: A prospective, randomized study

BACKGROUND

The effect of adding alpha lipoic acid (ALA) to pulsed radiofrequency (PRF) for treatment of lumbar-sacral pain was evaluated.

OBJECTIVE

to evaluate the effect of using ALA as an adjuvant therapy with PRF for treatment of chronic lumbosacral radicular pain caused by herniated disc.

METHODS

One hundred twenty patients with lumbo-sacral radicular pain allocated into 2 groups. Group I: treated with PRF at 42°C for 120 seconds. Group II: treated as in group I, plus oral ALA 600 mg (Thiotacid 600 mg, EVA PHARMA, Egypt) three times per day (1800 mg/day) for 3 weeks then 600 mg once daily for 2 weeks. The lumbo-sacral radicular pain evaluated using the numerical rating pain score and Oswestry Disability Index.

RESULTS

Success rate was significantly higher in group II at 3 and 6 months after intervention. The median values of the numerical rating pain score and the Oswestry Disability Index were significantly lower in group II with no significant difference in Epworth Sleepiness Scale. No major complications were reported in both groups.

CONCLUSION

The current study supports the use of ALA with PRF on the dorsal root ganglion for treating lumbosacral radicular pain.

Efficacy and Safety of Pulsed Radiofrequency as a Method of Dorsal Root Ganglia Stimulation in Patients with Neuropathic Pain: A Systematic Review

OBJECTIVE

Pulsed radiofrequency (PRF) is a nonablative pain treatment that uses radiofrequency current in short high-voltage bursts, resulting in interruption of nociceptive afferent pathways. We conducted a systematic review with the aim to create a synthesis of evidence about the efficacy and safety of PRF applied to the dorsal root ganglion (DRG) for the treatment of neuropathic pain.

METHODS

We searched MEDLINE, CINAHL, Embase, and PsycINFO through January 8, 2019, as well as ClinicalTrials.gov and the clinical trial register of the World Health Organization. All study designs were eligible. We assessed risk of bias using the Cochrane tool for randomized controlled trials and the Risk Of Bias In Non-Randomized Studies of Interventions (ROBINS-I). We assessed level of evidence using the Oxford tool and quality of evidence with GRADE.

RESULTS

We included 28 studies with participants suffering from lumbosacral, cervical, or thoracic radicular pain, post-herpetic neuralgia, neuropathicbone pain in cancer patients, or carpal tunnel syndrome. Only five studies were randomized controlled trials (RCTs), while others were of nonrandomized designs, predominantly before and after comparisons. A total of 991 participants were included, with a median number (range) of 31 (1-101) participants. Only 204 participants were included in the RCTs, with a median number (range) of 38 (23-62) participants. The overall quality of evidence was low, as the majority of the included studies were rated as evidence level 4 or 5. The quality of evidence was very low.

CONCLUSIONS

Evidence about the efficacy and safety of PRF of the DRG for the treatment of neuropathic pain is based mainly on results from very small studies with low evidence quality. Current research results about the benefits of PRF of the DRG for the treatment of neuropathic pain should be considered preliminary and confirmed in high-quality RCTs with sufficient numbers of participants.

Examination and characterisation of the effect of amitriptyline therapy for chronic neuropathic pain on neuropeptide and proteomic constituents of human cerebrospinal fluid

INTRODUCTION

Amitriptyline is prescribed to reduce the intensity of chronic neuropathic pain. There is a paucity of validated in vivo evidence in humans regarding amitriptyline's mechanism of action. We examined the effect of amitriptyline therapy on cerebrospinal fluid (CSF) neuropeptides and proteome in patients with chronic neuropathic pain to identify potential mechanisms of action of amitriptyline.

METHODS

Patients with lumbar radicular neuropathic pain were selected for inclusion with clinical and radiological signs and a >50% reduction in pain in response to a selective nerve root block. Baseline (pre-treatment) and 8-week (post-treatment) pain scores with demographics were recorded. CSF samples were taken at baseline (pre-treatment) and 8 weeks after amitriptyline treatment (post-treatment). Proteome analysis was performed using mass spectrometry and secreted cytokines, chemokines and neurotrophins were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

A total of 9/16 patients experienced a >30% reduction in pain after treatment with amitriptyline and GO analysis demonstrated that the greatest modulatory effect was on immune system processes. KEGG analysis also identified a reduction in PI3K-Akt and MAPK signalling pathways in responders but not in non-responders. There was also a significant decrease in the chemokine eotaxin-1 (p ​= ​0.02) and a significant increase in the neurotrophin VEGF-A (p ​= ​0.04) in responders.

CONCLUSION

The CSF secretome and proteome was modulated in responders to amitriptyline verifying many pre-clinical and in vitro models. The predominant features were immunomodulation with a reduction in pro-inflammatory pathways of neuronal-glia communications and evidence of a neurotrophic effect.

IFN-γ Correlations with Pain Assessment, Radiological Findings, and Clinical Intercourse in Patient after Lumbar Microdiscectomy: Preliminary Study

Objectives

We investigated the influence of pain decrease after lumbar microdiscectomy on the interferon gamma (IFN-γ) serum level in patients with lumbar disc herniations. The study challenges the mechanism of sciatica pain and the role of IFN-γ in radicular pain development. Material and Methods. We performed clinical and immunoenzymatic assessment in a group of 27 patients with lumbar radicular pain due to disc herniations before and 3 months after surgery. Clinical status was assessed with the use of the Numeric Rating Scale (NRS), the Pain Rating Index and Pain Intensity Index of McGill Pain Questionnaire (SF-MPQ), the Oswestry Disability Index (ODI), and Beck Depression Inventory (BDI). The plasma concentrations of IFN-γ were ascertained by an immunoenzymatic method.

Results

We observe significant correlations between the results of the pain in the back region assessment NRS back scale after the surgery with the level of IFN-γ before the procedure (r_s = 0.528; p = 0.008) and after the procedure (r_s = 0.455; p = 0.025). These are moderate and positive correlations—the decrease in pain is correlated with the lower IFN-γ level. Additionally, there are significant correlations between the results of the PRI scale and the IFN-γ level. The PRI score before surgery correlates positively with IFN-γ after surgery (r_s = 0.462; p = 0.023), and the PRI score after surgery correlates positively with IFN before surgery (r_s = 0.529; p = 0.005) and after surgery (r_s = 0.549; p = 0.003). All correlations are moderate in severity—severe pain before surgery correlates with a higher level of IFN-γ after surgery and also higher IFN-γ before surgery. There were significant differences in the IFN-γ level before (Z = −2.733; p = 0.006) and after (Z = −2.391; p = 0.017) surgery in the groups of patients with and without nerve compression. In the group of patients with nerve compression, the level of IFN-γ before and after surgery was lower.

Conclusions

Less pain ratio after operation correlates with the level of IFN-γ. In the group of patients without significant nerve compression confirmed by MRI scans, the level of IFN-γ before and after surgery was higher than that in the group with nerve root compression.

Characterisation of the effects of pulsed radio frequency treatment of the dorsal root ganglion on cerebrospinal fluid cellular and peptide constituents in patients with chronic radicular pain: A randomised, triple-blinded, controlled trial

INTRODUCTION

Chronic radicular neuropathic pain is a major clinical problem with a life time prevalence of more than 50%. Pulsed radiofrequency (PRF) treatment is a recognised therapy. However, the pathophysiology of chronic neuropathic pain (CNP) and the mechanism of action of PRF remains ill-defined. Improving our knowledge of the mechanisms of CNP and PRF action will enhance our ability to treat patients with this common debilitating problem more effectively. This study aims to characterise the CSF cellular and peptide constituents in patients with CNP and the effect of pulsed radiofrequency (PRF) on these constituents and reported pain.

MATERIALS AND METHODS

Prospective randomised tripled-blinded control trial of patients receiving PRF treatment versus sham for radicular pain. All patients received local anaesthetic to the appropriate dermatome to confirm diagnosis. Clinical assessment using standard clinical assessment tools and examination of CSF using flow cytometry and ELISA for cellular and peptide constituents was carried out before and 3 months after treatment.

RESULTS

Ten patients were randomised to PRF (n = 5) or Sham (n = 5) treatment. PRF resulted in a significant reduction in pain score (NRS) at 3 months (6.8 to 2.6, p < .05). PRF reduced the TNF-α concentration and CD3+ count in CSF. CD4/CD8 ratio of patients with CNP was lower than historical controls (1.4 versus 3.0-4.2). The majority of CD3+ cells in the CNP patients were activated effector memory cells (80%) versus the surveillance central memory cells (85%) seen in healthy controls.

CONCLUSIONS

PRF is superior to local anaesthetic administration for the management of radicular pain and is associated with CSF constituent modulation in vivo. Patients with CNP have lymphocyte characteristics which suggest immune activation.

Genicular Nerve Pulsed Dose Radiofrequency (PDRF) Compared to Intra-Articular and Genicular Nerve PDRF in Knee Osteoarthritis Pain: A Propensity Score-Matched Analysis

Background

Chronic knee osteoarthritic (OA) pain is a common and debilitating complaint in elderly patients. Despite numerous pharmaceutical options, the majority of patients still experience long-term pain. Genicular nerve (GN) radiofrequency has become increasingly popular as a treatment for knee pain. This retrospective study aimed to evaluate the effects of pulse dose radiofrequency (PDRF) in patients with chronic knee OA pain.

Patients and Methods

Propensity score matching analysis was performed in a retrospective cohort of 78 patients with moderate-severe knee OA pain unresponsive to conservative treatment who underwent PDRF GN or intra-articular (IA) and PDRF GN. Pain relief was measured using the numeric rating scale (NRS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Patient Global Impression of Change (PGIC) at 3 and 6 months post-intervention.

Results

A significant reduction in NRS scores was reported at 3 (p<0.001) and 6 months (p<0.001) after PDRF in both groups. NRS was lower in PDRF IA + GN than PDRF GN (p<0.0001). WOMAC pain was significantly reduced at 3 months in PDRF IA + GN group (baseline: 10.12±3.14, 3 months: 6.25±2.44, p=0.0001). WOMAC stiffness and function were improved only at 3 months in PDRF IA + GN compared to baseline (p=0.007 and p=0.006, respectively). A longer period of pain relief was reported after PDRF IA + GN (6.75±2.42 months) compared to PDRF GN (4.31±2.85 months, p<0.001) in association with higher PGIC scores.

Conclusion

This is the first study that compared two different PDRF techniques. PDRF GN and PDRF IA + GN were both effective in reducing pain at 3 and 6 months follow-up. However, only PDRF IA + GN was able to improve WOMAC scores at 3 months after the treatment with a longer period of efficacy compared to PDRF GN alone.

Neuroimmune Interactions in Pain and Stress: An Interdisciplinary Approach

Mounting evidence indicates that disruptions in bidirectional communication pathways between the central nervous system (CNS) and peripheral immune system underlie the etiology of pathologic pain conditions. The purpose of this review is to focus on the cross-talk between these two systems in mediating nociceptive circuitry under various conditions, including nervous system disorders. Elevated and prolonged proinflammatory signaling in the CNS is argued to play a role in psychiatric illnesses and chronic pain states. Here we review current research on the dynamic interplay between altered nociceptive mechanisms, both peripheral and central, and physiological and behavioral changes associated with CNS disorders.

Examination and characterisation of burst spinal cord stimulation on cerebrospinal fluid cellular and protein constituents in patient responders with chronic neuropathic pain - A Pilot Study

INTRODUCTION

Patients with neuropathic pain have altered proteomic and neuropeptide constituents in cerebrospinal fluid (CSF) compared to controls. Tonic spinal cord stimulation (SCS) has demonstrated differential expression of neuropeptides in CSF before and after treatment suggesting potential mechanisms of action. Burst-SCS is an evidence-based paraesthesia free waveform utilised for neuropathic pain with a potentially different mechanistic action to tonic SCS. This study examines the dynamic biological changes of CSF at a cellular and proteome level after Burst-SCS.

METHODS

Patients with neuropathic pain selected for SCS had CSF sampled prior to implant of SCS and following 8 weeks of continuous Burst-SCS. Baseline and 8-week pain scores with demographics were recorded. T cell frequencies were analysed by flow cytometry, proteome analysis was performed using mass spectrometry and secreted cytokines, chemokines and neurotrophins were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

4 patients (2 females, 2 males) with a mean age of 51 years (+/-SEM 2.74, SD 5.48) achieved a reduction in pain of >50% following 8 weeks of Burst-SCS. Analysis of the CSF proteome indicated a significant alteration in protein expression most related to synapse assembly and immune regulators. There was significantly lower expression of the proteins: growth hormone A1 (PRL), somatostatin (SST), nucleobindin-2 (NUCB2), Calbindin (CALB1), acyl-CoA binding protein (DBI), proSAAS (PCSK1N), endothelin-3 (END3) and cholecystokinin (CCK) after Burst-SCS. The concentrations of secreted chemokines and cytokines and the frequencies of T cells were not significantly changed following Burst-SCS.

CONCLUSION

This study characterised the alteration in the CSF proteome in response to burst SCS in vivo. Functional analysis indicated that the alterations in the CSF proteome is predominately linked to synapse assembly and immune effectors. Individual protein analysis also suggests potential supraspinal mechanisms.

Cytotoxic Immunity in Peripheral Nerve Injury and Pain

Cytotoxicity and consequent cell death pathways are a critical component of the immune response to infection, disease or injury. While numerous examples of inflammation causing neuronal sensitization and pain have been described, there is a growing appreciation of the role of cytotoxic immunity in response to painful nerve injury. In this review we highlight the functions of cytotoxic immune effector cells, focusing in particular on natural killer (NK) cells, and describe the consequent action of these cells in the injured nerve as well as other chronic pain conditions and peripheral neuropathies. We describe how targeted delivery of cytotoxic factors via the immune synapse operates alongside Wallerian degeneration to allow local axon degeneration in the absence of cell death and is well-placed to support the restoration of homeostasis within the nerve. We also summarize the evidence for the expression of endogenous ligands and receptors on injured nerve targets and infiltrating immune cells that facilitate direct neuro-immune interactions, as well as modulation of the surrounding immune milieu. A number of chronic pain and peripheral neuropathies appear comorbid with a loss of function of cellular cytotoxicity suggesting such mechanisms may actually help to resolve neuropathic pain. Thus while the immune response to peripheral nerve injury is a major driver of maladaptive pain, it is simultaneously capable of directing resolution of injury in part through the pathways of cellular cytotoxicity. Our growing knowledge in tuning immune function away from inflammation toward recovery from nerve injury therefore holds promise for interventions aimed at preventing the transition from acute to chronic pain.

The effect of needle tip position on the analgesic efficacy of pulsed radiofrequency treatment in patients with chronic lumbar radicular pain: a retrospective observational study

Background

Pulsed radiofrequency (PRF) is a treatment modality that alleviates radicular pain by intermittently applying high-frequency currents adjacent to the dorsal root ganglion. There has been no comparative study on analgesic effect according to the position of the needle tip in PRF treatment. The objective of this study is to evaluate the clinical outcomes of PRF according to the needle tip position.

Methods

Patients were classified into 2 groups (group IP [group inside of pedicle] and group OP [group outside of pedicle]) based on needle tip position in the anteroposterior view of fluoroscopy. In the anteroposterior view, the needle tip was advanced medially further than the lateral aspect of the corresponding pedicle in group IP; however, in group OP, the needle tip was not advanced. The treatment outcomes and pain scores were evaluated at 4, 8, and 12 weeks after applying PRF.

Results

At 4, 8, and 12 weeks, there were no significant differences between the successful response rate and numerical rating scale score ratio.

Conclusions

The analgesic efficacy of PRF treatment did not differ with the needle tip position.

Dorsal root ganglion pulsed radiofrequency treatment for chronic cervical radicular pain: a retrospective review of outcomes in fifty-nine cases

Pulsed radiofrequency treatment adjacent to the cervical dorsal root ganglion is used to treat persistent cervical radicular pain that has not responded to conservative therapies. This technique has gained popularity in years for both cervical and lumbosacral radicular pain. The evidence to support its use is still evolving.

METHODS

We performed a retrospective review of outcomes in 59 patients who underwent this therapy over a 3-year period in our institution. We evaluated a reduction in pain, duration of pain relief, reduction in use of analgesics and progression to surgery.

RESULTS

Our results demonstrated 49 patients experienced some relief. Forty patients of the 59 experienced an improvement in pain of 50% or more. The mean duration of relief in this group was 37 weeks. Seven patients experienced complete resolution of their pain. In this group, the mean duration of relief was 39 weeks. Regarding the 53 patients who were taking medication for pain prior to the procedure, 37 patients reduced or discontinued their usage after the procedure.

CONCLUSION

Despite the limitations of a retrospective study, we feel our study adds to the growing evidence base that pulsed radiofrequency treatment adjacent to the cervical dorsal root ganglion has a role in the treatment of chronic cervical radicular pain.

CT-Guided Stellate Ganglion Pulsed Radiofrequency Stimulation for Facial and Upper Limb Postherpetic Neuralgia

Objective: Postherpetic neuralgia (PHN) is the most common complication of herpes zoster, manifesting as a persistent, spontaneous, knife-like pain or paroxysmal burning that seriously affects a patient’s quality of life. An effective treatment of PHN is lacking. This retrospective study examined the efficacy and safety of stellate ganglion (SG) pulsed radiofrequency (PRF) on facial and upper limb PHN.

Methods: Eighty-four patients with PHN on the face or upper limbs were enrolled for the study. Patients were randomly divided into two surgical groups according to the order of enrollment; one group underwent SG block (SG-B group, n = 42) and the other underwent SG pulsed radiofrequency (SG-P group, n = 42). After surgery, patients were followed at 1 week, 2 weeks, 1 month, 3 months, and 6 months. Observation at each follow-up included basic patient characteristics, visual analog scale (VAS), quality of life (QOL) using Physical Component Summary (PCS), and Mental Component Summary (MCS) to assess, total effective rate, complications and side effects.

Results: Compared with preoperative values, VAS decreased in both groups after surgery (P < 0.05). In the SG-B group, VAS increased after 1 month, while in the SG-P group, VAS gradually decreased at later follow-up time points. VAS decreased more significantly in the SG-P group after 1 month (P < 0.05). PCS and MCS increased in both groups after the operation, and the difference was significant compared with preoperative values (P < 0.05). The total effective rates of the SG-B and SG-P groups were 64.3 and 83.3%, respectively. The total effective rate of the SG-P group was higher than that of the SG-B group (P < 0.05). The incidence of complications and side effects in the SG-B group was higher than that in the SG-P group (P < 0.05).

Conclusion: SG pulsed radiofrequency treatment of facial and upper limb PHN is safe and effective. It is a treatment method worth promoting.