Internal-specific morphological analysis of sciatic nerve fibers in a radiofrequency-induced animal neuropathic pain model

Efficacy of High-Voltage Pulsed Radiofrequency in Zoster-Associated Pain: A Meta-Analysis and Systematic Review

Background

Zoster-associated pain (ZAP) is often refractory to conventional treatments and can seriously affect patients' physical and mental health. High-voltage pulsed radio frequency (H-PRF) is a new method for treating ZAP with pulse voltages above 60 V or even up to 100 V. The purpose of this paper was to conduct a systematic review and meta-analysis to evaluate the efficacy of H-PRF in the management of ZAP.

Methods

PubMed, Embase, and the Cochrane library were searched from their inception to June 2022 to identify controlled trials which evaluated the effectiveness of H-PRF compared with standard PRF and sham operations. The primary outcome was pain scores at different treatment times. The secondary outcomes included SF-36 scores, rescue analgesic dose, and side effects.

Results

We reviewed 6 randomized controlled trials involving 428 patients. There was no significant difference between the H-PRF and standard PRF pain scores at 1 week after surgery and the sham operation group at 1 month. At 1, 3, and 6 months, the H-PRF group had better pain score than the standard PRF group, and at 3 months, the pain score was better than the sham operation group. The H-PRF group showed improvement in the SF-36 score, and there were no significant complications in the H-PRF group.

Conclusions

H-PRF is an effective and safe treatment method that has better effects in relieving pain and improving the quality of life and physical and mental health. Although H-PRF provides pain relief rates comparable to those of the control group in the early stages, it remains the preferred and alternative treatment for relieving herpes zoster-related pain.

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.

The role of cannabinoid CB1 receptors in the antinociceptive and reparative actions of mesenchymal stem cells in rats with peripheral neuropathic pain

Mesenchymal stem cells (MSCs) can produce antinociceptive and reparative effects. Presumably, the MSCs-induced antinociception may be partly due to the involvement of the endocannabinoid system. The study aimed to evaluate the antinociceptive and reparative effects of adipose-derived MSCs (ADMSCs) upon pharmacological modulation of cannabinoid CB1 receptor in peripheral tissues or on ADMSCs' membranes in a rat model of peripheral neuropathy. ADMSCs were injected into the area of rat sciatic nerve injury (i) with no additional treatments, (ii) at the tissue CB1 receptor activation by endogenous agonist anandamide (AEA) or blockade with a selective AM251 antagonist; and (iii) preincubated with AEA or AM251. The evaluation of CB1 receptor activity involved analyzing nociceptive responses, gait parameters, and histology. Transplantation of ADMSCs upon activation of CB1 receptors, both on AMSCs' membranes or in the area of nerve injury, accelerated the analgesia and recovery of dynamic gait parameters, abolished static gait disturbances, and promoted the fastest nerve regeneration. Only blockade of CB1 receptors on ADMSCs shortened ADMSCs-induced analgesia and decreased the number of preserved nerve fibers. CB1 receptors on ADMSCs significantly contribute to their pain-relieving and tissue-repairing capabilities by stimulating the growth factors secretion and suppressing the release of pro-inflammatory cytokines. Peripheral CB1 receptors do not significantly influence ADMSC-induced antinociception.

Sodium phenylbutyrate inhibits Schwann cell inflammation via HDAC and NFκB to promote axonal regeneration and remyelination

Background

Epigenetic regulation by histone deacetylases (HDACs) in Schwann cells (SCs) after injury facilitates them to undergo de- and redifferentiation processes necessary to support various stages of nerve repair. Although de-differentiation activates the synthesis and secretion of inflammatory cytokines by SCs to initiate an immune response during nerve repair, changes in either the timing or duration of prolonged inflammation mediated by SCs can affect later processes associated with repair and regeneration. Limited studies have investigated the regulatory processes through which HDACs in SCs control inflammatory cytokines to provide a favorable environment for peripheral nerve regeneration.

Methods

We employed the HDAC inhibitor (HDACi) sodium phenylbutyrate (PBA) to address this question in an in vitro RT4 SC inflammation model and an in vivo sciatic nerve transection injury model to examine the effects of HDAC inhibition on the expression of pro-inflammatory cytokines. Furthermore, we assessed the outcomes of suppression of extended inflammation on the regenerative potential of nerves by assessing axonal regeneration, remyelination, and reinnervation.

Results

Significant reductions in lipopolysaccharide (LPS)-induced pro-inflammatory cytokine (tumor necrosis factor-α [TNFα]) expression and secretion were observed in vitro following PBA treatment. PBA treatment also affected the transient changes in nuclear factor κB (NFκB)-p65 phosphorylation and translocation in response to LPS induction in RT4 SCs. Similarly, PBA mediated long-term suppressive effects on HDAC3 expression and activity. PBA administration resulted in marked inhibition of pro-inflammatory cytokine secretion at the site of transection injury when compared with that in the hydrogel control group at 6-week post-injury. A conducive microenvironment for axonal regrowth and remyelination was generated by increasing expression levels of protein gene product 9.5 (PGP9.5) and myelin basic protein (MBP) in regenerating nerve tissues. PBA administration increased the relative gastrocnemius muscle weight percentage and maintained the intactness of muscle bundles when compared with those in the hydrogel control group.

Conclusions

Suppressing the lengthened state of inflammation using PBA treatment favors axonal regrowth and remyelination following nerve transection injury. PBA treatment also regulates pro-inflammatory cytokine expression by inhibiting the transcriptional activation of NFκB-p65 and HDAC3 in SCs in vitro.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02273-1.

Efficacy of High-Voltage Pulsed Radiofrequency for the Treatment of Elderly Patients with Acute Herpes Zoster Neuralgia

OBJECTIVE

The aim of this study was to evaluate the efficacy of high-voltage pulsed radiofrequency in comparison with standard-voltage pulsed radiofrequency for the treatment of elderly patients with acute herpes zoster neuralgia.

METHODS

Sixty-four elderly acute herpes zoster neuralgia patients were randomly assigned to the standard-voltage pulsed radiofrequency group (i.e., group S, 32 cases) and the high-voltage pulsed radiofrequency group (i.e., group H, 32 cases), which received the standard-voltage and high-voltage pulsed radiofrequency treatment, respectively. The doses of gabapentin and tramadol for analgesia were adjusted based on pain degree of patients. The therapeutic effectiveness were assessed using the numeric rating scale and the sleep quality scale. The doses of gabapentin and tramadol before pulsed radiofrequency and 1, 2, 4, 8, and 12 weeks after pulsed radiofrequency were measured. The incidence of clinically meaningful postherpetic neuralgia (pulsed radiofrequency) 12 weeks after pulsed radiofrequency was noted.

RESULTS

After pulsed radiofrequency, the numeric rating scale score and the doses of gabapentin and tramadol in group H were significantly lower than those in group S, respectively (p<0.05). The sleep quality scale score in group H was significantly higher than that in group S (p<0.05). The incidence of clinically meaningful pulsed radiofrequency in group H was significantly lower than that in group S (p<0.05).

CONCLUSION

For the treatment of elderly patients with acute herpes zoster neuralgia, when compared with the standard-voltage pulsed radiofrequency, the high-voltage pulsed radiofrequency can rapidly and steadily reduce the pain degree, improve the sleep quality, reduce the doses of anticonvulsants and analgesics, and decrease the incidence of clinically meaningful postherpetic neuralgia.

Physiological and functional responses of water-cooled versus traditional radiofrequency ablation of peripheral nerves in rats

BACKGROUND AND OBJECTIVES

Several clinical studies have focused on assessing the effectiveness of different radiofrequency ablation (RFA) modalities in pain management. While a direct head-to-head clinical study is needed, results from independent studies suggest that water-cooled RFA (CRFA) may result in longer lasting pain relief than traditional RFA (TRFA). The primary purpose of this study was, therefore, to investigate in a preclinical model, head-to-head differences between the two RFA technologies.

METHODS

RFA was performed in a rat sciatic nerve model (n=66) in two groups: (1) TRFA or (2) CRFA. The surgeon was not blinded to the treatment; however, all the physiological endpoints were assessed in a blinded fashion which include histological, MRI, and nerve function assessment via electromyography.

RESULTS

The energy delivered by the generator for CRFA was significantly higher compared with TRFA. Histological staining of nerves harvested immediately following CRFA exhibited extended length and multiple zones of thermal damage compared with TRFA-treated nerves. MRI scans across 4 weeks following treatment showed edematous/inflammatory zones present for longer times following CRFA. Finally, there was greater attenuation and prolonged loss of nerve function measured via electromyography in the CRFA group.

CONCLUSIONS

This study shows that CRFA has greater energy output, as well as more pronounced structural and functional changes elicited on the peripheral nerves compared with TRFA. While these preclinical data will need to be confirmed with a large clinical randomized controlled trial, we are encouraged by the direction that they may have set for those trials.

Pulsed radiofrequency for chronic pain: In vitro evidence of an electroporation mediated calcium uptake

Pulsed radiofrequency (PRF) treatments for chronic pain consist in the delivery of a train of sinusoidal electric bursts to the targeted nerve. Despite numerous clinical evidence of its efficiency, the mechanism of action of PRF remains unclear. Since most of the reported biological effects of PRF can be initiated by a calcium influx into the neurons, we hypothesized that PRF may induce a mild electroporation effect causing a calcium uptake. To test this hypothesis, HEK-293 cells were exposed to PRF bursts and cytosolic calcium and Yo-Pro-1 uptake were monitored. After a single burst, calcium peaks were observed for electric fields above 480 V/cm while the uptake of Yo-pro-1 was insignificant. After a train of 120 bursts, the electric fields required to induce a calcium and Yo-pro-1 uptake decreased to 330 V/cm and 880 V/cm respectively. Calcium peaks were not detected when cells were treated in calcium free media. The temperature increase during the treatments was lower than 5 °C in all cases. Finally, the cell response for different burst frequencies and extracellular media conductivities correlated with the induced transmembrane voltage calculated with a numerical model. Our results support the hypothesis of an electroporation mediated calcium influx.

Therapeutic exercise and radiofrequency in the rehabilitation project for hip osteoarthritis pain

BACKGROUND

Severe hip osteoarthritis is responsible for disabling pain and functional impairment of the joint. Although total hip arthroplasty (THA) is a successful treatment, some patients have multiple comorbidities that represent contraindications for THA. Conventional drug therapies are often ineffective or responsible for numerous side effects. For these patients, it is difficult to draw up an acceptable rehabilitation path, as the main limitation is intense pain. New rehabilitation strategies that relieve pain and improve articular function need to be developed. The combination of traditional treatments such as education and therapeutic exercise with innovative, minimally-invasive therapies such as continuous radiofrequency (CRF) appears to reduce hip pain by determining the neurolysis of the joint.

AIM

The aim of our study was to describe the reduction in pain and improvements in joint function when CRF is combined with the therapeutic exercise in rehabilitation of patients with severe hip osteoarthritis.

DESIGN

Case series study.

SETTING

Rehabilitation service outpatients.

POPULATION

Twenty-five patients with severe hip osteoarthritis causing disabling pain and with contraindications to THA, and for whom conventional drug therapies were ineffective or responsible for numerous side effects.

METHODS

The study design included: initial clinical-functional assessment using the Harris Hip Score (HHS), the Numeric Rating Scale (NRS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC); a pre-lesion anaesthetic block; hip neuroablation with CRF; a three-week kinesitherapy protocol (3 sessions per week); two further assessments using the same scales one month (T1) and six months (T2) after CRF.

RESULTS

Improvements at T1 and T2 follow-ups, after CRF (P=0.000) were recorded for articular pain and function. However, results at T2 were worse than those at T1 (P=0.000).

CONCLUSIONS

CRF combined with therapeutic exercise in rehabilitation of severe hip osteoarthritis is an attractive option for significant pain relief as it allows patients to carry out kinesitherapy more easily.

CLINICAL REHABILITATION IMPACT

CRF could represent a valid alternative in the rehabilitation of patients with severe hip osteoarthritis especially when other therapeutic approaches are unworkable.

Systematic Review of Radiofrequency Ablation for Management of Knee Pain

PURPOSE OF REVIEW

Chronic pain of the lower extremity remains challenging to manage. Radiofrequency ablation procedure applies heat to nerve fibers with the goal of mitigating chronic pain conditions of the knee. However, the clinical efficacy has not yet been adequately established. The goal of this review paper is to report the use of radiofrequency ablations in the treatment of osteoarthritis of the knee.

RECENT FINDINGS

PubMed and the Cochrane Controlled Trials Register were searched (final search 28 February 2018) using the MeSH terms "radiofrequency ablation," "neurolysis," "radiofrequency therapy," "pain syndrome," "analgesia," and "pain" in the English literature. Bibliographies of the published papers were screened for relevance to lower extremity radiofrequency ablation therapies. The quality of selected publications was assessed using the Cochrane risk of bias instrument. Of the 923 papers screened, 317 were further investigated for relevance. Our final search methodology yielded 19 studies that investigated the use of radiofrequency ablation at the knee. Of these 19 studies, there were four randomized control trials, two non-randomized control trials, three prospective studies, two retrospective studies, one case-control study, one technical report, and seven case reports. In summary, the data available suggests radiofrequency ablation as a promising and efficacious with all 19 studies revealing significant short- and long-term pain reductions in patients with knee pain.

A Systematic Review of Radiofrequency Treatment of the Ankle for the Management of Chronic Foot and Ankle Pain

BACKGROUND

Chronic pain of the lower extremity remains challenging to manage. Radiofrequency treatment applies heat to nerve fibers with the goal of mitigating chronic pain conditions. The clinical efficacy has not yet been adequately established for pathologies of the ankle and foot. In this review paper, we report the use and efficacy of radiofrequency treatment applied to foot and ankle pain.

RECENT FINDINGS

PubMed and the Cochrane Controlled Trials Register were searched (final search 30 March 2018) using the MeSH terms "radiofrequency ablation," "neurolysis," "radiofrequency therapy," "pain syndrome," "analgesia," "plantar heel pain," "plantar fascitis," and "chronic pain" in the English literature. Of the 23 papers screened, 18 were further investigated for relevance. Our final search methodology yielded 15 studies that investigated the use of radiofrequency treatment at the ankle. Of these 15 studies, there were three randomized control trials, four prospective studies, three retrospective studies, and five case reports. The quality of selected publications was assessed using the Cochrane risk of bias instrument. The evidence from our studies suggests that radiofrequency treatment can be used safely for the management foot and ankle pain. The technique (continuous vs pulsatile), temperature, location of treatment, and duration of administration need more thorough evaluation. Randomized control trials are needed to establish the efficacy and safety profile of radiofrequency ablation and its long-term benefits in patients with chronic pain of the foot and ankle.

CONCLUSION

The evidence from our studies suggests that radiofrequency treatment can be used safely for the management foot and ankle pain. The technique (continuous vs pulsatile), temperature, location of treatment, and duration of administration need more thorough evaluation. Randomized control trials are needed to establish the efficacy and safety profile of radiofrequency ablation and its long-term benefits in patients with chronic pain of the foot and ankle.

Label-free monitoring of inflammatory tissue conditions using a carrageenan-induced acute inflammation rat model

Although the confirmation of inflammatory changes within tissues at the onset of various diseases is critical for the early detection of disease and selection of appropriate treatment, most therapies are based on complex and time-consuming diagnostic procedures. Raman spectroscopy has the ability to provide non-invasive, real-time, chemical bonding analysis through the inelastic scattering of photons. In this study, we evaluate the feasibility of Raman spectroscopy as a new, easy, fast, and accurate diagnostic method to support diagnostic decisions. The molecular changes in carrageenan-induced acute inflammation rat tissues were assessed by Raman spectroscopy. Volumes of 0 (control), 100, 150, and 200 µL of 1% carrageenan were administered to rat hind paws to control the degree of inflammation. The prominent peaks at [1,062, 1,131] cm^-1 and [2,847, 2,881] cm^-1 were selected as characteristic measurements corresponding to the C-C stretching vibrational modes and the symmetric and asymmetric C-H (CH₂ ) stretching vibrational modes, respectively. Principal component analysis of the inflammatory Raman spectra enabled graphical representation of the degree of inflammation through principal component loading profiles of inflammatory tissues on a two-dimensional plot. Therefore, Raman spectroscopy with multivariate statistical analysis represents a promising method for detecting biomolecular responses based on different types of inflammatory tissues.