Pulsed radiofrequency effects on the lumbar ganglion of the rat dorsal root: a morphological light and transmission electron microscopy study at acute stage

Radiofrequency for chronic lumbosacral and cervical pain: Results of a consensus study using the RAND/UCLA appropriateness method

BACKGROUND

Despite the routine use of radiofrequency (RF) for the treatment of chronic pain in the lumbosacral and cervical region, there remains uncertainty on the most appropriate patient selection criteria. This study aimed to develop appropriateness criteria for RF in relation to relevant patient characteristics, considering RF ablation (RFA) for the treatment of chronic axial pain and pulsed RF (PRF) for the treatment of chronic radicular pain.

METHODS

The RAND/UCLA Appropriateness Method (RUAM) was used to explore the opinions of a multidisciplinary European panel on the appropriateness of RFA and PRF for a variety of clinical scenarios. Depending on the type of pain (axial or radicular), the expert panel rated the appropriateness of RFA and PRF for a total of 219 clinical scenarios.

RESULTS

For axial pain in the lumbosacral or cervical region, appropriateness of RFA was determined by the dominant pain trigger and location of tenderness on palpation with higher appropriateness scores if these variables were suggestive of the diagnosis of facet or sacroiliac joint pain. Although the opinions on the appropriateness of PRF for lumbosacral and cervical radicular pain were fairly dispersed, there was agreement that PRF is an appropriate option for well-selected patients with radicular pain due to herniated disc or foraminal stenosis, particularly in the absence of motor deficits. The panel outcomes were embedded in an educational e-health tool that also covers the psychosocial aspects of chronic pain, providing integrated recommendations on the appropriate use of (P)RF interventions for the treatment of chronic axial and radicular pain in the lumbosacral and cervical region.

CONCLUSIONS

A multidisciplinary European expert panel established patient-specific recommendations that may support the (pre)selection of patients with chronic axial and radicular pain in the lumbosacral and cervical region for either RFA or PRF (accessible via https://rftool.org). Future studies should validate these recommendations by determining their predictive value for the outcomes of (P)RF interventions.

Bipolar, high-voltage, long-duration pulsed radiofrequency ablation of the Gasserian ganglion for the treatment of trigeminal neuralgia in a patient with a cardiac implantable electronic device: illustrative case

BACKGROUND

One of the common methods of treating trigeminal neuralgia (TN) nowadays is radiofrequency therapy. However, it has serious limitations in patients with a cardiac pacemaker because of electromagnetic interference. Therefore, it is crucial to select optimal radiofrequency ablation parameters to make this procedure safe with favorable outcomes for such patients.

OBSERVATIONS

In this study, the authors present a case of a 70-year-old man with a history of cardiac pacemaker dependency and previous microvascular decompression with complaints of severe, constant facial pain. After reprogramming the cardiac implantable electronic device (CIED), the authors performed bipolar, high-voltage, long-duration pulsed radiofrequency therapy (PRFT) of the Gasserian ganglion under electrocardiography and pulse rate control in the pre-, intra-, and postoperative periods. There were no cardiovascular or neurological complications after PRFT. The patient reported relief of pain after the procedure, and at the 9-month follow-up, he was pain-free.

LESSONS

This clinical case demonstrates that the use of bipolar, high-voltage PRFT for TN treatment in patients with a CIED can be safe and effective, provided that the rules and pacemaker instructions are followed. It is necessary to use ablative treatment with caution and to guide the patient in collaboration with a cardiac surgeon and an anesthesiologist resuscitator.

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.

The treatment of persistent spinal pain syndrome with epidural pulsed radiofrequency: improvement of the technique

Background

In Persistent Spinal Pain Syndrome (PSPS), Pulsed Radiofrequency (PRF) is a used procedure. The results of PRF in PSPS performed with an electrode placed through the sacral hiatus were reported to be successful on pain in only 32% of patients. We have tried to improve the results by applying a new system to PRF.

Methods

Ten patients were treated with PRF application through a steerable epidural catheter with a reference electrode outside the foramen. This method was named "Optimization Current Flow" (OCF). The duty cycle of PRF was 2 × 10 msec and total exposure time was 150 s. Follow up was planned for 1, 3, and 6 months. The NRS score was considered to be the primary outcome.

Results

In the first 10 patients treatment was successful (69% of the patients) at 6 months follow-up.

Conclusion

This new modality of PRF in patients with PSPS seems to be superior to procedures done with a needle. Further prospective double-blind randomized long-term studies with a significant number of patients are required to validate this technique as there is a need to improve PRF results in PSPS.

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.

Short-pulsed micro-magnetic stimulation of the vagus nerve

Vagus nerve stimulation (VNS) is commonly used to treat drug-resistant epilepsy and depression. The therapeutic effect of VNS depends on stimulating the afferent vagal fibers. However, the vagus is a mixed nerve containing afferent and efferent fibers, and the stimulation of cardiac efferent fibers during VNS may produce a rare but severe risk of bradyarrhythmia. This side effect is challenging to mitigate since VNS, via electrical stimulation technology used in clinical practice, requires unique electrode design and pulse optimization for selective stimulation of only the afferent fibers. Here we describe a method of VNS using micro-magnetic stimulation (µMS), which may be an alternative technique to induce a focal stimulation, enabling a selective fiber stimulation. Micro-coils were implanted into the cervical vagus nerve in adult male Wistar rats. For comparison, the physiological responses were recorded continuously before, during, and after stimulation with arterial blood pressure (ABP), respiration rate (RR), and heart rate (HR). The electrical VNS caused a decrease in ABP, RR, and HR, whereas µM-VNS only caused a transient reduction in RR. The absence of an HR modulation indicated that µM-VNS might provide an alternative technology to VNS with fewer heart-related side effects, such as bradyarrhythmia. Numerical electromagnetic simulations helped estimate the optimal coil orientation with respect to the nerve to provide information on the electric field’s spatial distribution and strength. Furthermore, a transmission emission microscope provided very high-resolution images of the cervical vagus nerve in rats, which identified two different populations of nerve fibers categorized as large and small myelinated fibers.

The Mechanism of Action between Pulsed Radiofrequency and Orthobiologics: Is There a Synergistic Effect?

Radiofrequency energy is a common treatment modality for chronic pain. While there are different forms of radiofrequency-based therapeutics, the common concept is the generation of an electromagnetic field in the applied area, that can result in neuromodulation (pulsed radiofrequency—PRF) or ablation. Our specific focus relates to PRF due to the possibility of modulation that is in accordance with the mechanisms of action of orthobiologics. The proposed mechanism of action of PRF pertaining to pain relief relies on a decrease in pro-inflammatory cytokines, an increase in cytosolic calcium concentration, a general effect on the immune system, and a reduction in the formation of free radical molecules. The primary known properties of orthobiologics constitute the release of growth factors, a stimulus for endogenous repair, analgesia, and improvement of the function of the injured area. In this review, we described the mechanism of action of both treatments and pertinent scientific references to the use of the combination of PRF and orthobiologics. Our hypothesis is a synergic effect with the combination of both techniques which could benefit patients and improve the life quality.

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.

Changes in the gene expression in mouse astrocytes induced by pulsed radiofrequency: A preliminary study

Glial cells, both astrocytes and microglia, play important roles in the induction and maintenance of neuroinflammation resulting in neuropathic pain. Pulsed radiofrequency (PRF) is applied to various nerves for the treatment of pain, although the molecular mechanism underlying its effects is still unclear. We herein investigated the genomic effects of PRF on a mouse cultured astrocyte cell line. PRF was applied to the cultured astrocytes in 20-msec pulses of 480 kHz every 500 msec, delivered at the rate of 2 Hz, for 30 min. PRF increased the expression of 2,431 genes and decreased that of 209 genes. Among these genes, 435 genes were upregulated >10-fold and 89 genes >30-fold, while no genes showed a 10-fold decrease in expression. A gene ontology analysis using the list of >10-fold upregulated genes showed that PRF treatment activated immune responses. A pathway analysis using the Kyoto Encyclopedia of Gene and Genomes with the same list detected seven pathways related to neuropathic pain. These findings suggest that PRF improves neuropathic pain via neuroimmunomodulation.

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.

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.

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.

Pulsed Radiofrequency Neuromodulation Contributes to Activation of Platelet-Rich Plasma in In Vitro Conditions

OBJECTIVES

Recent years have brought new developments in interventional chronic pain management, namely regenerative orthopedics utilizing platelet-rich plasma (PRP) as well as further evolution of pulsed radiofrequency neuromodulation (PRF). Both methods have been used separately. Here, we investigated whether PRF may potentiate the activation of platelets in PRP samples when both these techniques are combined together in in vitro conditions.

MATERIALS AND METHODS

Studies were performed on concentrated PRP samples (PRPs) obtained from acid citrate dextrose-treated blood taken from 11 healthy volunteers. PRPs were divided into four groups: 1) nonactivated PRP; 2) thrombin-activated PRP as a positive control for maximal platelets activation; 3) PRF-treated PRP exposed for 20 min to PRF energy generated by neurotherm radio frequency generator at 500 kHz, with a voltage of 40 V and maximal temperature of 42°C; and 4) a combination of groups 2 and 3.

RESULTS

PRF-induced platelet activation measured by platelet factor 4 (PF4) and ATP release from PRPs was significantly higher compared to nonactivated PRPs, and similar to PF4 and ATP release from thrombin-activated PRPs. Thrombin activation did not potentiate PF4 release in PRF samples and even reduced ATP level. Additionally, PRF neither induced any platelet membrane damage measured by lactic dehydrogenase release from PRP nor modified any platelets viability or metabolism measured by MTT.

CONCLUSIONS

We confirmed that PRF may activate PRP without additional platelet activators. So, a combination of both methods PRF and PRP application may provide a more effective opportunity for tissue regeneration in dentistry, surgery, dermatology, or in orthopedics.

Pulsed radiofrequency of the median nerve under ultrasound guidance for management of intractable neuropathic pain

A median nerve injury in the forearm may lead to devastating sequelae if left untreated. Even with appropriate treatments involving microsurgical techniques and postoperative care, patients may still experience lasting neuropathic pain that significantly reduces their quality of life. Pulsed radiofrequency (PRF) is widely performed to alleviate such neuropathic pain caused by trauma.

A 47-year-old man visited our pain clinic with allodynia, hyperalgesia, paresthesia, skin color changes, and atrophy in the right forearm. In the orthopedic department, the patient was treated by neurectomy of the median nerve to manage the intractable pain. However, the effect was unsatisfactory. The fourth median nerve block performed in our pain clinic after neurectomy produced good results, and ultrasound-guided PRF of the median nerve was performed.

The patient showed 80% relief of symptoms within 5 hours after the procedure. The visual analog scale score for the forearm decreased from 8/10 to 1/10. This case suggests that ultrasound-guided PRF can be a therapeutic option for the management of refractory neuropathic pain after neurectomy in patients with a median nerve injury.

Efficacy and Safety of Computed Tomography-Guided Pulsed Radiofrequency Modulation of Thoracic Dorsal Root Ganglion on Herpes Zoster Neuralgia

OBJECTIVE

Pulsed radiofrequency (PRF) can relieve postherpetic neuralgia (PHN) caused by herpes zoster (HZ) infection. Nevertheless, its curative effect can vary and may be related to the duration of treatment period. The following study investigates the efficacy and safety of CT-guided PRF modulation on HZ neuralgia over different periods and different time points.

MATERIALS AND METHODS

A total of 150 patients with HZ/PHN were enrolled at the Pain Department, Shengjing Hospital of China Medical University between January 2013 and December 2016. According to the course of disease, the patients were randomly divided into group A, which included patients with acute stage (n = 50; course <1 m); group B, which included patients with subacute stage (n = 50; 1 m <course <3 m); and group C, which included patients with chronic stage (n = 50; course >3 m). The PRF therapy was performed in all patients by targeting thoracic dorsal root ganglion (DRG). The visual analogue scale (VAS), SF-36, total effective rate of treatment, and dosage of antiepileptic analgesic drugs were observed at different time points, before and after the surgery.

RESULTS

Compared to preoperative time, decreased VAS, improved SF-36, and the decreased dosage of antiepileptic analgesic drugs were observed at all time points, and in all groups after surgery (p < 0.05). In group A, pain relief lasted longer, and it further decreased over time. In addition, significantly lower VAS, higher SF-36, and lower dosage of antiepileptic analgesic drugs were found in group A compared to group B, and in group B compared to group C (all p < 0.05). Furthermore, the total effective rates in groups A, B, and C were 88, 72, and 52%, respectively.

CONCLUSIONS

CT-guided PRF targeting thoracic DRG for modulation of HZ neuralgia in different periods is safe and effective. It is recommended to perform early intervention therapy at the acute phase of HZ.

Transforaminal epidural steroid injection combined with pulsed radio frequency on spinal nerve root for the treatment of lumbar disc herniation

Background

Lumbar disc herniation (LDH) is a common disease in clinical practice. The symptoms recur and are aggravated by time; severe pain and long-term movement disorder cause physiological and psychological problems that affect the quality of life of patients. Therefore, relieving the pain symptoms and promoting functional recovery are the primary goals that have gained increased attention.

Objective

To assess the efficacy of CT-guided transforaminal epidural steroid injection (TFESI) combined with pulsed radio frequency (PRF) on spinal nerve root for the treatment of LDH.

Study design

Retrospective comparative study.

Setting

Shengjing Hospital of China Medical University.

Methods

A total of 135 patients with LDH were selected from the Department of Pain Management in the Shengjing Hospital of China Medical University between January 2014 and December 2016. All patients were divided into three groups according to the order of entry (n=45): TFESI (group A); PRF on spinal nerve root (group B); and TFESI combined with PRF on spinal nerve root (group C). The visual analog scale (VAS), Oswestry disability index (ODI), and global perceived effect (GPE) before treatment and at different time points after treatment were observed, and patients' satisfaction was assessed.

Results

At every point of observation, the VAS and ODI decreased significantly as compared to that before treatment in all groups (P<0.05). The VAS and ODI in group A at 3 and 6 months after treatment were significantly higher than that in the other two groups (P<0.05). At day 1, day 14, and 1 month after treatment, the VAS and ODI in group C were significantly lower than that in group B (P<0.05). The GPE in group C was high in the early days, while that at day 14 and 1 month after treatment was significantly higher than that in the other two groups (P<0.05); no significant difference was observed in GPE at 3 and 6 months after treatment between groups B and C (P>0.05).

Conclusion

TFESI combined with PRF for the treatment of LDH could effectively and rapidly relieve lumbago and radicular pain and achieve long-term remission. Although the method is widely applicable, the precise selection of patients is imperative.

Photobiomodulation of the dorsal root ganglion for the treatment of low back pain: A pilot study

BACKGROUND AND OBJECTIVE

Chronic low back pain is a worldwide public health issue with high socioeconomic impact. The aim of this study was to determine the efficacy of laser irradiation of the dorsal root ganglion of the second lumbar spinal nerve for chronic axial low back pain compared to lidocaine injection and radiofrequency treatment.

STUDY DESIGN/MATERIALS AND METHODS

Twenty-eight patients were randomly divided into three treatment groups: lidocaine injection, radiofrequency, or laser. The second intervertebral foramen between the second and third lumbar vertebrae was accessed by percutaneous needle puncture bilaterally, guided by fluoroscopy. In the local anesthetic group, injection of 1 ml lidocaine without epinephrine was applied through a 20-gauge (G20) Quincke tip spinal needle inserted in the second lumbar intervertebral foramen. In the radiofrequency group, the probe (150 mm long with a 5 mm active tip) was directed through a G20 needle placed in the second lumbar intervertebral foramen and neuromodulation was done with a radiofrequency of Cosman G4® in pulses of 20 ms with wash-out period of 480 ms, for 300 seconds at 42°C. A single treatment was used. In the laser treatment group, a continuous wave, 808 nm wavelength diode laser (Photon Lase III® DCM, Brazil), with an output power of 100 mW was used for a single treatment. An 18 gauge needle was placed in the second lumbar intervertebral foramen guided by fluoroscopy. Light was delivered through a 600 µm optical fiber placed in the G18 needle. The tip of the fiber extended 5 mm beyond the tip of the needle in the second lumbar intervertebral foramen. The beam spot size was 0.003 cm(2) , irradiance = 35W/cm(2) , exposure time = 84 seconds, energy density = 2800J/cm(2) , total energy was 8.4 J. The low back pain score was assessed by the visual analog scale (VAS) and Pain Relief Scale (PRS) pre, post procedure and in 1 month follow up. Temperature was measured using a digital thermometer.

RESULTS

All patients in the local anesthetic and laser treatment groups reported a pain reduction of at least 50% immediately post-procedure and 10 out of 11 patients in the radiofrequency group reported a pain reduction of at least 50%. At 1 month post-treatment, the laser treatment group had the greatest number of patients who reported more than 50% pain relief based on PRS (7 out of 10 patients) while only 2 out of 7 patients and 3 out of 11 patients in the lidocaine and radiofrequency treatment groups respectively reported more than a 50% pain relief.

CONCLUSION

Laser irradiation caused an immediate decrease in low back pain post-procedure similar to pain reduction caused by lidocaine injection. Both lidocaine injection and laser irradiation were more effective than radiofrequency treatment for immediate and longer term (1 month post-treatment) chronic back pain. Lasers Surg. Med. 48:653-659, 2016. © 2016 Wiley Periodicals, Inc.

Pulsed radiofrequency attenuates diabetic neuropathic pain and suppresses formalin-evoked spinal glutamate release in rats

BACKGROUND

Pulsed radiofrequency (PRF) has been used to treat chronic pain for years, but its effectiveness and mechanism in treating diabetic neuropathic pain are still unexplored. The aim of this study was to elucidate the modulation of diabetic neuropathic pain induced by streptozotocin and the release of spinal excitatory amino acids by PRF.

METHODS

Diabetes was induced by intraperitoneal administration of streptozotocin. Pulsed radiofrequency was applied to L5 and L6 dorsal roots at 42 °C for 2 min. The responses of all of the groups to thermal, mechanical and cold stimuli were measured for a period of 6 d after this process. Seven days after PRF treatment, intrathecal microdialysis was used to examine the effect of pulsed radiofrequency on the formalin-evoked spinal release of excitatory amino acids and concurrent behaviour responses from diabetic rats.

RESULTS

Three weeks after intraperitoneal streptozotocin treatment and before PRF application, mechanical, thermal and cold hypersensitivity occurred. Application of PRF significantly alleviated hyperglycaemia-induced mechanical, thermal and cold hypersensitivity and also attenuated the increase in formalin-evoked CSF glutamate concentration, compared with sham treated diabetic rats.

CONCLUSION

It may be concluded that PRF has an analgesic effect on neuropathic pain by suppressing the nociception-induced release of excitatory neurotransmitters. PRF may provide a novel promising therapeutic approach for managing diabetic neuropathic pain.

Long-Term Anti-Allodynic Effect of Immediate Pulsed Radiofrequency Modulation through Down-Regulation of Insulin-Like Growth Factor 2 in a Neuropathic Pain Model

Pulsed radiofrequency (PRF) is effective in the treatment of neuropathic pain in clinical practice. Its application to sites proximal to nerve injury can inhibit the activity of extra-cellular signal-regulated kinase (ERK) for up to 28 days. The spared nerve injury (SNI)+ immPRF group (immediate exposure to PRF for 6 min after SNI) exhibited a greater anti-allodynic effect compared with the control group (SNI alone) or the SNI + postPRF group (application of PRF for 6 min on the 14th day after SNI). Insulin-like growth factor 2 (IGF2) was selected using microarray assays and according to web-based gene ontology annotations in the SNI + immPRF group. An increase in IGF2 and activation of ERK1/2 were attenuated by the immPRF treatment compared with an SNI control group. Using immunofluorescent staining, we detected co-localized phosphorylated ERK1/2 and IGF2 in the dorsal horn regions of rats from the SNI group, where the IGF2 protein predominantly arose in CD11b- or NeuN-positive cells, whereas IGF2 immunoreactivity was not detected in the SNI + immPRF group. Taken together, these results suggest that PRF treatment immediately after nerve injury significantly inhibited the development of neuropathic pain with a lasting effect, most likely through IGF2 down-regulation and the inhibition of ERK1/2 activity primarily in microglial cells.

Association between extracellular signal-regulated kinase expression and the anti-allodynic effect in rats with spared nerve injury by applying immediate pulsed radiofrequency

BACKGROUND

The application of pulsed radiofrequency (PRF) close to the dorsal root ganglia, or peripheral nerves, has been demonstrated to be effective for the treatment of chronic neuropathic pain conditions. The goal of this study was to investigate the analgesic effect of immediate PRF treatment after nerve injury and its possible cellular alterations in the dorsal horn of the spinal cord in rats with spared nerve injury (SNI).

METHODS

Neuropathic pain was achieved in a SNI neuropathic pain model by ligating and cutting the common peroneal and tibial branches of the left sciatic nerve, leaving the sural nerve intact. Wistar rats were divided into four groups that received different treatments, i.e., SNI and PRF for 6 min at 45 V (SNI + PRF-45 V), at 60 V (SNI + PRF-60 V), SNI alone, and sham groups. After the SNI surgery, each rat was immediately given the PRF treatment (500 kHz, rate of 2 Hz, 20 ms duration, temperature below 42 °C) on the left sciatic nerve 0.3-0.4 cm proximal to the injured site. The behavioral measurements included mechanical allodynia and cold allodynia of the ipsilateral hind paw and were performed during the 28 days that followed the SNI surgery and PRF treatment. Total extracellular signal-regulated kinase 1 and 2 (ERK1/2) and phospho-ERK1/2 were measured using Western blot in the ipsilateral spinal cord from animals in the different groups.

RESULTS

The three groups of rats with nerve injuries manifested a lower paw withdrawal threshold (PWT) in the behavioral measurement of mechanical allodynia and a shorter painful-behavior duration in the cold allodynia test over 28 days. Mechanical allodynia measurement showed that both the PRF-45 V and PRF-60 V treatment groups exhibited a more prominent antiallodynic effect than did the SNI group from days 1 to 28 after surgery. Similarly, in comparison with the SNI group, both the SNI + PRF-45 V and SNI + PRF-60 V groups had significant inhibition on the cold allodynia measurement from days 1 to 28 after surgery. Furthermore, the activation of the extracellular signal-regulated kinase 1 and 2 (ERK1/2) in the ipsilateral spinal dorsal horn of SNI rats was effectively inhibited in the SNI + PRF-45 V and SNI + PRF-60 V groups for 28 days after surgery.

CONCLUSIONS

Immediate PRF application on the proximal nerve injury site provided a significant inhibition of neuropathic pain formation, accompanied by the inhibition of ERK activation.

Pulse-dose radiofrequency can reduce chronic pain in trapezio-metacarpal osteoarthritis: A mini-invasive therapeutic approach

AIM

To assess the efficiency of pulse-dose radiofrequency (PDRF) in the management of chronic pain in patients with trapezio-metacarpal osteoarthritis (OA).

METHODS

Seventy-five patients with trapezio-metacarpal OA were treated with the PDRF between October 2011 and September 2013. A 22-gauge cannula with a 5-cm length was introduced with percutaneous access in the lateral region of the affected trapezio-metacarpal joint. The PDRF procedure was performed with 1200 pulses at 45 V and 20 msec duration, followed by a 480 msec silent phase. The follow-up visits were performed at 1 month, 3 and 6 months after the PDRF procedure. All patients underwent a second treatment between 7 and 9 months after the first PDRF procedure with a new follow-up scheme at 1, 3, 6 and 9 months.

RESULTS

Mean visual analogue scale (VAS) scores before the procedures was 8.5 ± 1.1. A great reduction in pain intensity was reported at 3 months after the PDRF procedure (mean VAS scores 3.1 ± 0.9, P < 0.05). Pain intensity began to increase back to pre-procedural values after 4 months (mean VAS scores at 6 months was 7.9 ± 1.3, P < 0.05). After the second PDRF treatment the mean VAS scores decreased to 3.3 ± 0.8 at 3 months, but increased to 8.1 ± 1.6 at 9 months. (P < 0.05). No complications after the procedures were observed.

CONCLUSIONS

The PDRF may be a safe, repeatable and effective short-term pain management technique in patients with trapezio-metacarpal OA. Larger, randomized controlled studies are indicated to better clarify the efficacy and utility of the PDRF.

Could myelin damage from radiofrequency electromagnetic field exposure help explain the functional impairment electrohypersensitivity? A review of the evidence

Myelin provides the electrical insulation for the central and peripheral nervous system and develops rapidly in the first years of life, but continues into mid-life or later. Myelin integrity is vital to healthy nervous system development and functioning. This review outlines the development of myelin through life, and then considers the evidence for an association between myelin integrity and exposure to low-intensity radiofrequency electromagnetic fields (RF-EMFs) typical in the modern world. In RF-EMF peer-reviewed literature examining relevant impacts such as myelin sheath, multiple sclerosis, and other myelin-related diseases, cellular examination was included. There are surprisingly little data available in each area, but considered together a picture begins to emerge in RF-EMF-exposed cases: (1) significant morphological lesions in the myelin sheath of rats; (2) a greater risk of multiple sclerosis in a study subgroup; (3) effects in proteins related to myelin production; and (4) physical symptoms in individuals with functional impairment electrohypersensitivity, many of which are the same as if myelin were affected by RF-EMF exposure, giving rise to symptoms of demyelination. In the latter, there are exceptions; headache is common only in electrohypersensitivity, while ataxia is typical of demyelination but infrequently found in the former group. Overall, evidence from in vivo and in vitro and epidemiological studies suggests an association between RF-EMF exposure and either myelin deterioration or a direct impact on neuronal conduction, which may account for many electrohypersensitivity symptoms. The most vulnerable are likely to be those in utero through to at least mid-teen years, as well as ill and elderly individuals.

Pulsed radiofrequency reduced complete Freund's adjuvant-induced mechanical hyperalgesia via the spinal c-Jun N-terminal kinase pathway

Pulsed radiofrequency (PRF) treatment involves the pulsed application of a radiofrequency electric field to a nerve. The technology offers pain relief for patients suffering from chronic pain who do not respond well to conventional treatments. We tested whether PRF treatment attenuated complete Freund's adjuvant (CFA) induced inflammatory pain. The profile of spinal c-Jun N-terminal kinases (JNKs) phosphorylation was evaluated to elucidate the potential mechanism. Injection of CFA into the unilateral hind paw of rats induced mechanical hyperalgesia in both the ipsilateral and contralateral hind paws. We administered 500-kHz PRF treatment in 20-ms pulses, at a rate of 2 Hz (2 pulses per second) either to the sciatic nerve in the mid-thigh, or to the L4 anterior primary ramus just distal to the intervertebral foramen in both the CFA group and no-PRF group rats. Tissue samples were examined at 1, 3, 7, and 14 days following PRF treatments. Behavioral studies showed that PRF applied close to the dorsal root ganglion (DRG) significantly attenuated CFA-induced mechanical hyperalgesia compared to no-PRF group (P < .05). And western blotting revealed significant attenuation of the activation of JNK in the spinal dorsal horn compared to no-PRF group animals (P < .05). Application of PRF close to DRG provides an effective treatment for CFA-induced persistent mechanical hyperalgesia by attenuating JNK activation in the spinal dorsal horn.

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

This study investigated the reversible effects of pulsed radiofrequency (PRF) treatment at 42 °C on the ultrastructural and biological changes in nerve and collagen fibers in the progression of neuropathic pain after rat sciatic nerve injury. Assessments of morphological changes in the extracellular matrices by atomic force microscopy and hematoxylin-eosin, Masson's trichrome and picrosirius-red staining as well as the expressions of two fibril-forming collagens, types-I and -III, and two inflammatory cytokines, TNF-α and IL-6, were evaluated on day 30 after RF exposure. There were four groups for different RF thermal treatments: no treatment, no current, PRF, and continuous RF (CRF). An RF procedure similar to that used in human clinical trials was used in this study. The CRF treatment at 82 °C led to neural and collagen damage by the permanent blockage of sensory nociceptors. The PRF treatment led to excellent performance and high expandability compared to CRF, with effects including slight damage and swelling of myelinated axons, a slightly decreased amount of collagen fibers, swelling of collagen fibril diameters, decreased immunoreactivity of collagen types-I and -III, presence of newly synthesized collagen, and recovery of inflammatory protein immunoreactivity. These evidence-based findings suggest that PRF-based pain relief is responsible for the temporary blockage of nerve signals as well as the preferential destruction of pain-related principal sensory fibers like the Aδ and C fibers. This suggestion can be supported by the interaction between the PRF-induced electromagnetic field and cell membranes; therefore, PRF treatment provides pain relief while allowing retention of some tactile sensation.

Interventional management of cancer pain

PURPOSE OF REVIEW

Interventional techniques were the mainstay for cancer pain management before the WHO ladder and opioids were freely available. The three-step WHO ladder has its limitations, and cancer pain is often under treated. Advances in treatment options mean that cancer patients are living longer and pain interventions may have a role to play even early in the cancer diagnosis for better quality of analgesia. The role of high doses of opioids in pain management is also currently under scrutiny.

RECENT FINDINGS

Recent advances in intrathecal analgesia, radiofrequency techniques, both in tumour ablation and neurotomies, are being widely used for palliation. Vertebroplasty techniques have been used not only for pain relief, but also for stabilization. Improved imaging and thoracoscopic techniques have made coeliac plexus and splanchnic blockade safer and more efficacious. There has been recent interest in percutaneous cordotomy with newer techniques using computed tomography/MRI and endoscopy guidance. Percutaneous electrical nerve stimulation and 8% capsaicin patches have been successfully used for managing neuropathic pain in cancer.

SUMMARY

Interventions form an integral part in providing pain relief in complex cancer pains. Oncologists and palliative care physicians are to be educated on the usefulness and timing of interventions in the management of complex cancer pain.

A prospective study of Gasserian ganglion pulsed radiofrequency combined with continuous radiofrequency for the treatment of trigeminal neuralgia

We conducted a prospective randomized controlled study to evaluate whether continuous radiofrequency (CRF) combined with pulsed radiofrequency (PRF) to the Gasserian ganglion (GG) decreases the side effects of CRF while preserving efficacy. Sixty patients diagnosed with classic trigeminal neuralgia (TN) were treated with either 75°C CRF for 120 s to 180 s (SCRF group), 75°C CRF for 240 s to 300 s (LCRF group), or 42°C PRF for 10 minutes (min) followed by 75°C CRF for 120 s to 180 s (PCRF group). Patients were assessed for pain intensity, quality of life (QOL), and intensity of facial dysesthesia before (baseline), and at seven days, three months, six months, and 12 months after the procedure. The efficacy in pain relief was most significant on the seventh day after treatment and there were no significant differences between groups. After 12 months, >70% of patients in each group had complete pain relief, and the QOL in all three groups had increased significantly compared to baseline. The intensity of facial dysesthesia was mildest in the SCRF group and most severe in the PCRF group on the seventh day after the procedure, but most persistent in the LCRF group. Patients who receive PRF combined with CRF to the GG can achieve comparable pain relief to those who receive CRF alone, and shorter exposure of CRF could result in less destruction of the target tissue.

Long-term effect of pulsed radiofrequency on chronic cervical radicular pain refractory to repeated transforaminal epidural steroid injections

OBJECTIVE

The article aims to evaluate the long-term effectiveness and safety of pulsed radiofrequency (PRF) on the dorsal root ganglion (DRG) in patients with chronic cervical radicular pain refractory to repeated transforaminal epidural steroid injections (TFESIs).

DESIGN

This is a prospective observational study.

METHODS

We retrospectively reviewed data on 112 subjects who had received repeated TFESIs for cervical radicular pain. Twenty-nine of those 112 patients continued to complain of persistent cervical radicular pain, despite an average of three repeated TFESIs. Among 29 patients with sustained arm pain of over 4 on the numerical rating scale (NRS), a total of 21 patients were included prospectively. Those 21 patients underwent PRF on the symptomatic cervical DRG and were evaluated carefully for neurologic deficits and side effects. The clinical outcomes were measured via NRS for arm pain before treatment, and 1, 3, 6, and 12 months after treatment. Successful pain relief was defined as a 50% or more reduction in the NRS score as compared with the pretreatment score. After 12 months, patients' satisfaction levels with treatment were determined.

RESULTS

Fourteen of the 21 patients (66.7%) after cervical PRF stimulation reported pain relief of 50% or more at the 3-month and 12-month follow-up periods, respectively. Fifteen of the 21 patients (71.4%) were satisfied with their outcome at 12 months' posttreatment. No serious adverse effects were observed.

CONCLUSION

Application of PRF to the DRG appears to be an effective and relatively safe intervention technique for chronic cervical radicular pain refractory to repeated TFESIs.

Application of pulsed radiofrequency currents to rat dorsal root ganglia modulates nerve injury-induced tactile allodynia

BACKGROUND

Application of pulsed radiofrequency (PRF) currents to the dorsal root ganglia (DRG) has been reported to produce relief from certain pain states without causing thermal ablation. In this study, we examined the direct correlation between PRF application to DRG associated with spinal nerve injury and reversal of injury-induced behavioral hypersensitivity in a rat neuropathic pain model.

METHODS

Neuropathic lesioning was performed via left L5 spinal nerve ligation on male adult Sprague-Dawley rats. Once the injured rats had developed tactile allodynia, one group was then assigned to PRF treatment of the L5 DRG and another group was assigned to the sham treatment to the DRG. Behavioral testing was performed on both the control and treated paws using the von Frey filament test before the surgery and at indicated days. The resulting data were analyzed using a linear mixed model to assess the overall difference between the treatment groups and the overall difference among the study days. Cohen's d statistic was computed from paired difference-from-baseline scores for each of the 14 study days after treatment and these measures of effect size were then used to descriptively compare the recovery patterns over time for each study group.

RESULTS

Spinal nerve injury resulted in the development of behavioral hypersensitivity to von Frey filament stimulation (allodynia) in the hindpaw of the left (injury) side. Mixed linear modeling showed a significant difference between the treatment groups (P = 0.0079) and a significant change of paw withdrawal threshold means over time (P = 0.0006) for all 12 animals. Evaluation of Cohen's d (effect size) revealed that the PRF-treated animals exhibited better recovery and recorded larger effect sizes than the sham-treated animals on 10 of the 14 post-PRF treatment days and exhibited moderate-to-strong effects posttreatment at days 8 to 10 and at and beyond day 32.

CONCLUSIONS

Findings from this study support that PRF of the DRG causes reversal of nerve injury (spinal nerve ligation)-induced tactile allodynia in rats. This allodynia reversal indicates that nonablative PRF acting via modulation of the DRG can speed recovery in nerve injury-induced pain.