Neural Ablation and Regeneration in Pain Practice

Surgical Management of Chronic Neuropathic Burn Pain

Burn-related chronic neuropathic pain can contribute to a decreased quality of life. When medical and pharmacologic therapies prove ineffective, patients should undergo evaluation for surgical intervention, consisting of a detailed physical examination and elective diagnostic nerve block, to identify an anatomic cause of pain. Based on symptoms and physical examination findings, particularly Tinel's sign, treatments can vary, including a trial of laser therapies, fat grafting, or nerve surgeries (nerve decompression, neuroma excision, targeted muscle reinnervation, regenerative peripheral nerve interfaces, and vascularized denervated muscle targets). It is essential to counsel patients to establish appropriate expectations prior to treatment with a multidisciplinary team.

Randomized Placebo-Controlled Trial of 60-Day Percutaneous Peripheral Nerve Stimulation Treatment Indicates Relief of Persistent Postoperative Pain, and Improved Function After Knee Replacement

OBJECTIVES

Total knee arthroplasty (TKA) is an effective surgery for end-stage knee osteoarthritis, but chronic postoperative pain and reduced function affect up to 20% of patients who undergo such surgery. There are limited treatment options, but percutaneous peripheral nerve stimulation (PNS) is a promising nonopioid treatment option for chronic, persistent postoperative pain. The objective of the present study was to evaluate the effect of a 60-day percutaneous PNS treatment in a multicenter, randomized, double-blind, placebo-controlled trial for treating persistent postoperative pain after TKA.

MATERIALS AND METHODS

Patients with postoperative pain after knee replacement were screened for this postmarket, institutional review board-approved, prospectively registered (NCT04341948) trial. Subjects were randomized to receive either active PNS or placebo (sham) stimulation. Subjects and a designated evaluator were blinded to group assignments. Subjects in both groups underwent ultrasound-guided placement of percutaneous fine-wire coiled leads targeting the femoral and sciatic nerves on the leg with postoperative pain. Leads were indwelling for eight weeks, and the primary efficacy outcome compared the proportion of subjects in each group reporting ≥50% reduction in average pain relative to baseline during weeks five to eight. Functional outcomes (6-minute walk test; 6MWT and Western Ontario and McMaster Universities Osteoarthritis Index) and quality of life (Patient Global Impression of Change) also were evaluated at end of treatment (EOT).

RESULTS

A greater proportion of subjects in the PNS groups (60%; 12/20) than in the placebo (sham) group (24%; 5/21) responded with ≥50% pain relief relative to baseline (p = 0.028) during the primary endpoint (weeks 5-8). Subjects in the PNS group also walked a significantly greater distance at EOT than did those in the placebo (sham) group (6MWT; +47% vs -9% change from baseline; p = 0.048, n = 18 vs n = 20 completed the test, respectively). Prospective follow-up to 12 months is ongoing.

CONCLUSIONS

This study provides evidence that percutaneous PNS decreases persistent pain, which leads to improved functional outcomes after TKA at EOT.

Efficacy of cryoneurolysis versus intra-articular steroid in sacroiliac joint pain: A retrospective, case-control study

Background and Aims

Intra-articular steroids provide significant pain relief in sacroiliac joint pain (SIJP), but their action is short-lived. Cryoneurolysis is reported to produce prolonged pain relief in various pain conditions. However, its efficacy has not been evaluated in patients with SIJP. Thus, we compared the efficacy of cryoneurolysis with steroid injections in adult patients with SIJP.

Methods

This retrospective healthcare records review-based study involved 83 patients with SIJP. Patients were divided into two groups: cases (sacroiliac joint [SIJ] cryoneurolysis, n = 39) and controls (SIJ steroid injection, n = 44). An 11-point numeric pain rating scale (NPRS) was used to assess the pain severity at baseline and immediately, 1, 3 and 6 months post-intervention. A reduction of ≥50% in NPRS score immediately following SIJ cryoneurolysis and steroid injection was considered a successful outcome. The difference between the treatment groups was assessed with a Chi-square test, and P < 0.05 was considered statistically significant.

Results

Both cases and controls showed significantly decreased NPRS scores from baseline to immediately, 1 month, 3 months and 6 months postintervention (P < 0.001). However, compared to controls, cases had significantly lower NPRS scores at all time points (all P < 0.001). Moreover, a significantly greater proportion of cases had ≥50% decrease in NPRS score from baseline, that is, 1 month (97.44% vs. 75%, P = 0.004), 3 months (100% vs. 47.73%, P < 0.001) and 6 months (69.23% vs. 27.27%, P < 0.001).

Conclusion

Although both cryoneurolysis and intra-articular steroid injections provide significant pain relief immediately, 1, 3 and 6 months postintervention, cryoneurolysis resulted in significantly greater pain relief.

Ultrasound-guided lateral pericapsular hip desensitization of the articular branches of the cranial gluteal nerve: A canine cadaveric study and feasibility study in dogs

OBJECTIVE

To develop and assess the feasibility, as a diagnostic block, of an ultrasound-guided lateral pericapsular hip desensitization (L-PHD) technique in dogs.

STUDY DESIGN

Prospective, randomized, anatomical and feasibility study.

ANIMALS

A total of 11 canine cadavers and eight adult dogs scheduled for acetabular surgical denervation.

METHODS

After studying the ultrasound anatomy of the lateral aspect of the gluteal region and determining an acoustic window to perform an ultrasound-guided L-PHD in three canine cadavers, the right and left hemipelves of eight canine cadavers were injected in the interfascial plane located lateral (LL-PHD group) or medial (LM-PHD group) to the deep gluteal muscle, with 0.05 mL kg-1 of dye per hip on each cadaver. The staining of the pericapsular nerves was assessed by anatomical dissection. Then, the LM-PHD was performed using 2% lidocaine as a diagnostic block in dogs scheduled for acetabular surgical denervation. Positive predictive value (PPV) was calculated for those animals who had favorable outcomes after acetabular surgical denervation.

RESULTS

The ultrasound-guided LL-PHD and LM-PHD could be performed by inserting the needle lateral and medial to the deep gluteal muscle. Ultrasound-guided LL-PHD stained the cranial gluteal nerve and its muscular branches in all injections and partially stained the lumbosacral trunk in two out of eight cadavers. The LM-PHD selectively stained the articular branches of the cranial gluteal nerve in all but one cadaver. The PPV for LM-PHD successful test prediction was 85.7% (95% confidence interval: 48.6% to 98.6%).

CONCLUSIONS

and clinical significance Ultrasound-guided LM-PHD using 0.05 mL kg-1 of dye selectively stained the articular branches of the cranial gluteal nerve in canine cadavers. The LM-PHD technique is feasible and could be used as a diagnostic block before acetabular surgical denervation in dogs.

Facets of facet joint interventions

Facet joint (FJ) disease is a common cause of axial low back pain with many minimally invasive image-guided treatment options. This article discusses fluoroscopic and CT-guided intraarticular FJ injections, medial branch (MB) radiofrequency ablation (RFA), and lumbar facet synovial cyst (LFSC) aspiration, rupture, or fenestration. Additionally, the article will highlight medial branch blocks (MBBs) utilized to diagnose facet-mediated pain and to predict outcomes to RFA.

Water-circulating probes significantly modify lesion length and axon damage in cooled radiofrequency ablations when compared with similar-sized standard radiofrequency probes in rats

INTRODUCTION

Preclinical research demonstrated water-cooled radiofrequency (CRF) ablations have a significant impact on structural and functional changes compared to standard radiofrequency (SRF) ablations. Clinical procedures utilizing RF to treat chronic pain conditions also show sustained functional outcomes. We hypothesize that the design of the RF probes plays an important role in interventional procedure success, but it remains unclear which specific design features.

METHODS

RF ablations were performed in male Lewis rats (n=51) using multiple-sized probes for CRF (17 Ga/2 mm and 17Ga/4 mm) and SRF (22Ga/5 mm, 18Ga/10 mm and 16Ga/10 mm) to evaluate generator energy output, lesion length, axon damage by histology and nerve function analysis via electromyography. To exclude probe design variables beyond size and remain objective, we tested cooled probes with and without water circulation, which resulted in the CRF probe performing like an SRF probe.

RESULTS

Consistent with our previous findings in smaller probes, CRF large probes delivered more energy (p<0.01) and generated multiple zones of thermal damage in sciatic nerves. When the water-circulating feature was turned off, however, energy output (p<0.001) and lesion length (p<0.05) was significantly reduced. CRF probes with the water circulation also featured significantly more axonal disruption, than larger sized SRF probes (p<0.0001).

CONCLUSIONS

Overall, this data confirms that CRF's water-circulating technology has a greater impact on energy deposition, lesion length and axon damage compared with SRF ablations. Moreover, results suggest that the structural differences between RF modalities cannot be solely attributed to probe size, and it may shed light on its differences in clinical outcomes.

Non-Surgical Treatments of Trigeminal Neuralgia from the Perspective of a Pain Physician: A Narrative Review

Trigeminal neuralgia (TN) is a unilateral disorder characterized by electric shock-like pain, abrupt onset and termination, and limited to one or more branches of the trigeminal nerve. Various therapeutic modalities for TN have been introduced. We searched for literature indexed in PubMed, Medline, and the National Library of Medicine and reviewed all relevant articles on non-surgical treatments for TN. Published studies were reviewed with no restrictions on date; reviews, clinical trials, animal studies, retrospective studies, and cases were included. Carbamazepine and oxcarbazepine are the recommended first-line pharmacotherapies. Interventional treatments should be considered when pharmacotherapy is insufficient or withdrawn because of adverse effects.

An Analysis of the Clinical and Radiological Prognostic Factors Affecting the Outcomes of Lumbar Intradiscal Biacuplasty

Purpose: Intradiscal biacuplasty (IDB) has been proven to be effective for treating lumbar degenerative disc disease (DDD). However, there has not been a reported prognostic factor for IDB. The present study meticulously evaluates the general and radiographic features that may serve as markers for predicting the therapeutic outcome of IDB. Methods: A prospective case series study was conducted, following time-series analysis moving averages models, with forty-one patients suffering from chronic discogenic lower back pain for more than six months. These patients subsequently received lumbar cool radiofrequency IDB and were enrolled in the study. Thirty-seven patients completed follow-up questionnaires at 1, 3, 6, and 12 months. The surgical outcomes were reported using visual analogue scale (VAS), Oswestry disability index (ODI), and the consumption of nonsteroidal anti-inflammatory drugs (NSAID). Furthermore, a univariate analysis was performed to identify prognostic factors associated with pain relief from age, gender, body mass index (BMI), and pre-operative lumbar magnetic resonance imaging reading. Results: Significant reductions were found in estimated VAS and ODI at the post-operative period at 1, 3, 6, and 12 months (P < 0.001). The NSAID dosage was significantly decreased at 3-month and 1-year follow-up (P < 0.05). No procedure-related complications were detected. The prognosis of IDB was not related to disc height, Pfirrmann grading or Modic endplate change. However, disc extrusions were associated with promising outcomes (VAS improvement ≥ 50%) on pain relief (P < 0.05). Conclusion: IDB is a good alternative choice for treating lumbar DDD. Patients with a painful extrusion lumbar disc may gain some benefits after receiving IDB following a period of failed conservative treatment. These findings may also add some references for physicians in the decision making when treating lumbar DDD.

How Far Has Radiofrequency Thermocoagulation Come Along as a Treatment Procedure in Treating Trigeminal Neuralgia Patients?

Trigeminal neuralgia (TN) refers to sudden shooting pain in areas innervated by trigeminal nerves originating from the Gasserian ganglion. Physicians initially manage it by prescribing drugs, such as carbamazepine. Surgical intervention is the next best option if patients do not respond to drug treatments. These procedures include microvascular decompression, rhizotomy, balloon compression, and gamma knife surgery. However, less optimal patient outcomes, recurrences, adverse effects, and high costs have necessitated alternative surgical interventions to treat such patients. Radiofrequency thermocoagulation (RFT) has emerged as a minimally invasive, safer, and effective surgical option in treating TN patients. Despite research showing RFT's safety and effectiveness, neurosurgical healthcare providers do not frequently use it to treat TN patients. Lack of universal standardized protocol, and minimal awareness of its efficacy in specific cohorts, such as geriatric patients, may lead to RFT underutilization. Hence, this review highlights RFT's advancement as a robust alternative to traditional surgical approaches in treating TN patients. In addition, it identifies RFT's areas of improvement and its safety and effectiveness in treating elderly TN patients. We followed the Systematic Reviews and Meta-Analyses guidelines for systematic reviews and conducted a literature search between July 2022 and March 2023. Our findings indicate that RFT has evolved significantly over the last decade and a half as a minimally invasive and effective treatment procedure for TN patients. It is more effective as a combined continuous and pulsed RFT than its other subtypes in treating primary TN patients. Moreover, RFT via a transverse puncture through the supraorbital foramen results in lesser inter- and post-procedural complications. Further, there is a slightly lesser incidence of post-procedural adverse effects and complications with RFT through the foramen rotundum. Besides, RFT, performed at a lower temperature of 65 degrees Celsius and a voltage between 64.51 and 79.29 volts, effectively provides pain relief and long-term patient satisfaction. RFT is safe and effective in patients over 60 with primary TN. Interestingly, it is also safe and effective in treating patients over 70 with poor fitness standards of Class II or higher. Despite these remarkable findings, there is still a substantial gap in the literature, specifically concerning the standardized protocol for temperature, voltage, and puncture methods of RFT. Despite the sufficient evidence of combined continuous and pulsed RFT's superiority in efficacy and safety, most researchers still utilize either pulsed or continuous RFT. Studies vary in not only these aspects but also the patient cohorts. For instance, most researchers focus solely on evaluating RFT's efficacy and safety in patients with primary TN, excluding a critical patient population suffering from secondary TN. Nevertheless, sufficient clinical evidence shows that RFT has come of age in treating primary TN patients. However, more extensive studies with large sample sizes of patients with primary and secondary TN with multiple trigeminal nerve affectation will significantly help standardize RFT protocol and its inclusion in the standard clinical practice in treating TN patients.

Neurological pain relief interventional radiology procedures

Neurological interventions have taken on a significant role in interventional radiology (IR) practice. Indications fall under three main categories: (1) intraprocedural pain management, (2) cancer pain palliation, and (3) chronic non-cancer pain control. Short-term regional anaesthesia can be achieved with local anaesthetics, while longer-term pain control can be attained with radiofrequency neuromodulation (pulsed or otherwise) or thermal/chemical neurolysis. This review article summarises the therapeutic options, applications, and techniques of commonly used peripheral nerve and plexus interventions in IR.

Medial Branch Radiofrequency Treatment for Low-Back Pain in Cancer Patients: A Case Series

Cancer patients are increasing in number, with an increased lifespan and advances in cancer treatment. Palliative care physicians often encounter difficulties in caring for patients with pain. In addition to cancer-related pain, patients with cancer may suffer from various musculoskeletal diseases, resulting in significant functional limitations of physical activities of daily living. We present three cases illustrating methods to deal with nonspecific mechanical low-back pain in patients with advanced cancer. We provide our therapeutic experiences, focusing on the usefulness of radiofrequency treatment in palliative care in patients with cancer.

Post-ablation augmentation of skin sympathetic nerve activity predicts a poor outcome of idiopathic ventricular arrhythmias

BACKGROUND

The neuromodulation effect after ventricular arrhythmia (VA) ablation is unclear. The study aimed to investigate skin sympathetic nerve activity (SKNA) changes in patients receiving catheter ablations for idiopathic VA.

METHODS

Of 43 patients with drug-refractory symptomatic VA receiving ablation, SKNA was continuously recorded for 10 min during resting from electrocardiogram lead I configuration and bipolar electrodes on the right arm 1 day before and 1 day after ablation.

RESULTS

Twenty-two patients with acute procedure success and no recurrence during follow-ups were classified as sustained success group (group 1). Other 21 patients were classified as failed ablation group (group 2). Baseline SKNA showed no significant difference between the two groups. Post-ablation SKNA in group 2 was significantly higher than in group 1. In patients with ablation involved right ventricular outflow tract (RVOT), the post-ablation SKNA was also significantly higher in group 2. In contrast, there was no difference in post-ablation SKNA between groups in patients receiving non-RVOT ablation.

CONCLUSION

The neuromodulation response after RVOT ablation may correspond to the sympathetic nerve distribution at RVOT. Augmentation of sympathetic activity after VA ablation indicates an unsuccessful VA suppression, especially in patients receiving ablation of RVOT VA.

Full Recovery after Multiple Treatments with Injectable Ice Slurry

Background

Cryoneurolysis uses tissue cooling as an opioid-sparing, long-lasting treatment for peripheral nerve pain. A nerve-selective method for cryoneurolysis by local injection of ice-slurry was developed to allow cryoneurolysis to be performed with a standard needle and syringe, similar to peripheral nerve blocks. Since the treatment of patients with chronic pain may require repeated injections, we investigated the safety and tolerance of repeated treatments in a rat model.

Methods

Three repeated ice-slurry treatments, given 6 weeks apart were performed around the rat sciatic nerve. Nerve and surrounding tissues were collected up to 4 months after the third treatment for analysis. Coherent anti-Stokes Raman scattering (CARS) microscopy was used to study effects on myelin sheaths and axon structure. Immunofluorescence (IF) staining was used to study effects on axon density. Hematoxylin and Eosin (H&E) staining was used to examine histologic effects on sciatic nerve and surrounding tissue.

Results

Histologic and CARS image analysis of nerve tissue collected months after three injections demonstrated recovery of nerve structure, myelin organization and axon density to baseline levels, without any residual inflammation, scarring or neuroma formation. No inflammation or scarring was detected in surrounding skin and muscle tissues.

Conclusion

Repeated ice-slurry injections cause temporary, nerve-selective and reversible changes in the peripheral nerve. There was no histologic damage to surrounding skin and muscle tissues. Repeated treatments with injectable ice-slurry for cryoneurolysis appear to be safe and well tolerated. Clinical studies for patients with chronic pain are warranted.

Peripheral Nerve Injury After Upper-Extremity Surgery Performed Under Regional Anesthesia: A Systematic Review

Purpose

Peripheral nerve injury (PNI) is a known adverse event following upper-limb surgery performed under brachial plexus regional anesthesia (RA). When PNI is noted after surgery, patients and providers often have questions about which factors might have contributed to this complication. This systematic review evaluates the literature on hand and shoulder surgeries performed under ultrasound-guided, plexus RA to identify factors potentially associated with PNI, including the surgery location and block type. We hypothesized that shoulder surgery might be associated with an increased risk of PNI compared to hand surgery.

Methods

A systematic review of the relevant literature was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Only prospective studies on the use of ultrasound-guided, preoperative, brachial plexus RA for hand or shoulder surgery on adult patients were included. Study groups were categorized according to surgery location and block type and compared across a number of factors via univariate and multivariate analyses.

Results

A total of 3,037 abstracts were screened; 192 full-text articles were independently reviewed by 2 of the authors; and 53 studies were included in the systematic review analysis. Following hand surgery, PNI was reported at an average rate of 1.35% ± 3.21% across 836 subjects in 40 study groups; after shoulder surgery, the average rate was 0.50% ± 1.57% across 3,383 subjects in 15 study groups. There was no statistically significant correlation between the incidence of PNI and surgery location (P =.70) or any of the most common approaches for brachial plexus anesthesia in the multivariate analysis.

Conclusions

This systematic review of over 50 articles on upper-limb surgery performed under RA shows no association between the incidence of PNI and the location of surgery or type of brachial plexus block.

Type of study/level of evidence

Diagnostic II.

Nerve Injury and Regeneration after Neurolysis: Ethanol Combined with Iodine-125 Radioactive Seed versus Ethanol Alone in Rabbits

PURPOSE

This study aimed to prove the hypothesis that neurolysis based on ethanol injection in combination with iodine-125 (¹²⁵I) radioactive seed implantation could prolong nerve regeneration time compared with ethanol injection alone. Moreover, we assessed the grade of nerve injury using both methods.

MATERIALS AND METHODS

Twenty female rabbits (mean 2.8 ± 0.2 kg) were randomly assigned to group A (neurolysis of the left brachial plexus nerve based on ethanol injection in combination with ¹²⁵I radioactive seed implantation, n=10) and group B (neurolysis using ethanol injection alone, n=10). The right brachial plexus nerve was used as a blank control. Injury and regeneration of the brachial plexus nerve were analyzed using electromyography (EMG). Statistical tests were performed using the Mann-Whitney U test and repeated-measures analysis of variance. The results were verified with histopathological examinations.

RESULTS

The overall postprocedural amplitude was significantly lower in group A than in group B (P=0.01), particularly in the second month after the procedure (P=0.036). However, no statistical difference in latency was observed between the two groups (P=0.103). Histopathological examination of both groups revealed Sunderland's third-degree peripheral nerve injury (PNI), mainly characterized by axon disintegration. The degree of nerve regeneration was significantly lower in group A than in group B.

CONCLUSION

Neurolysis based on ethanol injection in combination with ¹²⁵I radioactive seed implantation can prolong the time of nerve regeneration compared to ethanol injection alone, although both methods resulted in Sunderland's third-degree PNI.

The impact of needle location on clinical outcome of radiofrequency rhizotomy for trigeminal neuralgia

BACKGROUND

Radiofrequency thermocoagulation trigeminal rhizotomy (RT-TR) through the foramen ovale is a minimally invasive treatment for trigeminal neuralgia. Navigation of magnetic resonance imaging (MRI) and CT fusion imaging is a well-established method for cannulation of the Gasserian ganglion. In this study, we use the inline measurements from fusion image to analyze the anatomical parameters between the actual and simulation trajectories and compare the short- and intermediate-term outcomes according to determinable factors.

METHODS

The study included thirty-six idiopathic neuralgia patients who had undergone RT-TR with MRI and CT fusion image as a primary modality or repeated procedures.

RESULTS

Among thirty-six treated patients, the inline length of the trigeminal cistern was longer for the simulated trajectory (8.4 ± 2.4 versus 6.5 ± 2.8 mm; p < 0.05), and the predominant structure at risk extrapolated from the inline trajectory was the brainstem, which signified a more medially directed route, in contrast with the equal weighting of temporal lobe and brainstem for the actual trajectory. The preoperative visual analogue scale (VAS) was 9.3 ± 1.0, which decreased to 2.5 ± 2.6 and 2.9 ± 3.1 at first (mean, 3 months) and second (mean, 14 months) postoperative follow-up, respectively. The postoperative VAS scores at the two follow-ups were not statistically significant without a covariate analysis. After adjustment for covariate risk factors, the second follow-up sustained therapeutic benefit was evident in patients with no prior history of related treatment, an ablation temperature greater than 70 °C, and needle location within or adjacent to the trigeminal cistern.

CONCLUSIONS

This preliminary study demonstrated that the needle location between cistern and ganglion also plays a significant role in better intermediate-term results.

Genicular Nerve Ablation Review Using Cooled-Radiofrequency Nerve Ablation

Osteoarthritis (OA) is globally the most prevalent joint disease and causes patients great pain, limited joint mobility, and psychological distress. Short- and long-term therapies like steroid injections and arthroplasty exist, respectively. Joint arthroplasty can effectively treat symptomatic end-stage OA, but most patients do not go through with surgery because they are not qualified, have comorbidities, or do not wish to undergo surgery. As a result, patients can turn to opioid agonists for pain relief, which contributes to the growing opioid epidemic that mars our communities. Cooled radiofrequency ablation (C-RFA) is an effective treatment modality that can alleviate the pain associated with moderate to severe OA, especially in patients who have tried and failed conservative therapy. This review article elucidates the benefits of C-RFA, while also walking through the technical steps to performing the procedure. For patients suffering from debilitating joint OA, especially of the knee, C-RFA is a minimally invasive procedure that ensures pain relief.

Cooled Radiofrequency Ablation for Chronic Joint Pain Secondary to Hip and Shoulder Osteoarthritis

Osteoarthritis (OA) of the shoulder and hip is a leading cause of physical disability and mental distress. Traditional nonsurgical management alone is often unable to completely address the associated chronic joint pain. Moreover, a large number of patients are not eligible for joint replacement surgery owing to comorbidities or cost. Radiofrequency ablation (RFA) of articular sensory nerve fibers can disrupt the transmission of nociceptive signals by neurolysis, thereby providing long-term pain relief. A subtype of RFA, cooled RFA (CRFA), utilizes internally cooled electrodes to generate larger ablative zones compared with standard RFA techniques. Given the complex variable innervation of large joints such as the glenohumeral and hip joints, a larger ablative treatment zone, such as that provided by CRFA, is desired to capture a greater number of afferent nociceptive fibers. The suprascapular, axillary, and lateral pectoral nerve articular sensory branches are targeted during CRFA of the glenohumeral joint. The obturator and femoral nerve articular sensory branches are targeted during CRFA of the hip. CRFA is a promising tool in the interventionalist's arsenal for management of OA-related pain and symptoms, particularly in patients who cannot undergo, have long wait times until, or have persistent pain following joint replacement surgery. An invited commentary by Tomasian is available online. ^©RSNA, 2022.

Treatment Algorithm for Cancerous Wounds: A Systematic Review

BACKGROUND

In advanced cancer stage the incidence of cancerous wounds is about 5%, and the estimated life expectancy is not more than 6 to 12 months. Without interdisciplinary and individualized treatment strategy, symptoms progress, and adversely influence quality of life.

METHODS

Authors collected different treatment algorithms for cancerous wound published by wide scale of medical expertise, and summarized surgical, oncological, radiation oncological, nursing and palliative care aspects based on radiological information.

RESULTS

Interdisciplinary approach with continuous consultation between various specialists can solve or ease the hopeless cases.

CONCLUSIONS

This distressing condition needs a comprehensive treatment solution to alleviate severe symptoms. Non-healing fungating wounds without effective therapy are severe socio-economic burden for all participants, including patients, caregivers, and health services. In this paper authors collected recommendations for further guideline that is essential in the near future.

Advances in Oncoanaesthesia and Cancer Pain

INTRODUCTION

The growing interest on how peri-‑operative interventions, especially regional anesthesia, during cancer surgery can alter oncological outcome increasing disease free survival is probably responsible for the birth of the new subspecialty called onco-anesthesia. A paradigm shift in the concept of anesthetic management has occurred recently owing to the innumerable diverse revelations from the ongoing research in this field.

DISCUSSION

Long lasting but reversible epigenetic changes can occur due to surgical stress and perioperative anesthetic medications. The exact relationship between these factors and tumor biology is being studied further. A popular topic under research now is the influence of regional anesthesia on cancer recurrence. Combining nerve blocks with total intravenous anesthesia (TIVA) brings down the requirement of opioids and volatile anesthetic agents implicated in cancer recurrence. The study of mechanism of pain at the molecular level has led to the discovery of novel modes of prevention of chronic post-surgical pain. Newer combination aggressive treatment therapies -intraoperative chemotherapy and radiotherapy, isolated limb perfusion, photodynamic therapy and robotic surgery require specialized anesthetic management. The COVID pandemic introduced new guidelines for safe management of oncosurgical patients .Use of genomic mapping to personalize pain management will be the breakthrough of the decade.

CONCLUSION

The discovery that anesthetic strategy could have significant oncological sequel is a quantum leap forward. Avoiding some anesthetic medications may decrease cancer recurrence. Comprehensive cancer care and translational research will pave the way to uncover safe anesthetic practices.

Consensus practice guidelines on interventions for cervical spine (facet) joint pain from a multispecialty international working group

BACKGROUND

The past two decades have witnessed a surge in the use of cervical spine joint procedures including joint injections, nerve blocks and radiofrequency ablation to treat chronic neck pain, yet many aspects of the procedures remain controversial.

METHODS

In August 2020, the American Society of Regional Anesthesia and Pain Medicine and the American Academy of Pain Medicine approved and charged the Cervical Joint Working Group to develop neck pain guidelines. Eighteen stakeholder societies were identified, and formal request-for-participation and member nomination letters were sent to those organizations. Participating entities selected panel members and an ad hoc steering committee selected preliminary questions, which were then revised by the full committee. Each question was assigned to a module composed of 4-5 members, who worked with the Subcommittee Lead and the Committee Chairs on preliminary versions, which were sent to the full committee after revisions. We used a modified Delphi method whereby the questions were sent to the committee en bloc and comments were returned in a non-blinded fashion to the Chairs, who incorporated the comments and sent out revised versions until consensus was reached. Before commencing, it was agreed that a recommendation would be noted with >50% agreement among committee members, but a consensus recommendation would require ≥75% agreement.

RESULTS

Twenty questions were selected, with 100% consensus achieved in committee on 17 topics. Among participating organizations, 14 of 15 that voted approved or supported the guidelines en bloc, with 14 questions being approved with no dissensions or abstentions. Specific questions addressed included the value of clinical presentation and imaging in selecting patients for procedures, whether conservative treatment should be used before injections, whether imaging is necessary for blocks, diagnostic and prognostic value of medial branch blocks and intra-articular joint injections, the effects of sedation and injectate volume on validity, whether facet blocks have therapeutic value, what the ideal cut-off value is for designating a block as positive, how many blocks should be performed before radiofrequency ablation, the orientation of electrodes, whether larger lesions translate into higher success rates, whether stimulation should be used before radiofrequency ablation, how best to mitigate complication risks, if different standards should be applied to clinical practice and trials, and the indications for repeating radiofrequency ablation.

CONCLUSIONS

Cervical medial branch radiofrequency ablation may provide benefit to well-selected individuals, with medial branch blocks being more predictive than intra-articular injections. More stringent selection criteria are likely to improve denervation outcomes, but at the expense of false-negatives (ie, lower overall success rate). Clinical trials should be tailored based on objectives, and selection criteria for some may be more stringent than what is ideal in clinical practice.

Consensus practice guidelines on interventions for cervical spine (facet) joint pain from a multispecialty international working group

Background

The past two decades have witnessed a surge in the use of cervical spine joint procedures including joint injections, nerve blocks and radiofrequency ablation to treat chronic neck pain, yet many aspects of the procedures remain controversial.

Methods

In August 2020, the American Society of Regional Anesthesia and Pain Medicine and the American Academy of Pain Medicine approved and charged the Cervical Joint Working Group to develop neck pain guidelines. Eighteen stakeholder societies were identified, and formal request-for-participation and member nomination letters were sent to those organizations. Participating entities selected panel members and an ad hoc steering committee selected preliminary questions, which were then revised by the full committee. Each question was assigned to a module composed of 4–5 members, who worked with the Subcommittee Lead and the Committee Chairs on preliminary versions, which were sent to the full committee after revisions. We used a modified Delphi method whereby the questions were sent to the committee en bloc and comments were returned in a non-blinded fashion to the Chairs, who incorporated the comments and sent out revised versions until consensus was reached. Before commencing, it was agreed that a recommendation would be noted with >50% agreement among committee members, but a consensus recommendation would require ≥75% agreement.

Results

Twenty questions were selected, with 100% consensus achieved in committee on 17 topics. Among participating organizations, 14 of 15 that voted approved or supported the guidelines en bloc, with 14 questions being approved with no dissensions or abstentions. Specific questions addressed included the value of clinical presentation and imaging in selecting patients for procedures, whether conservative treatment should be used before injections, whether imaging is necessary for blocks, diagnostic and prognostic value of medial branch blocks and intra-articular joint injections, the effects of sedation and injectate volume on validity, whether facet blocks have therapeutic value, what the ideal cut-off value is for designating a block as positive, how many blocks should be performed before radiofrequency ablation, the orientation of electrodes, whether larger lesions translate into higher success rates, whether stimulation should be used before radiofrequency ablation, how best to mitigate complication risks, if different standards should be applied to clinical practice and trials, and the indications for repeating radiofrequency ablation.

Conclusions

Cervical medial branch radiofrequency ablation may provide benefit to well-selected individuals, with medial branch blocks being more predictive than intra-articular injections. More stringent selection criteria are likely to improve denervation outcomes, but at the expense of false-negatives (ie, lower overall success rate). Clinical trials should be tailored based on objectives, and selection criteria for some may be more stringent than what is ideal in clinical practice.

Claudin 14/15 play important roles in early wallerian degeneration after rat sciatic nerve injury

PURPOSE

Wallerian degeneration (WD) is an antegrade degenerative process distal to peripheral nerve injury. Numerous genes are differentially regulated in response to the process. However, the underlying mechanism is unclear, especially the early response. We aimed at investigating the effects of sciatic nerve injury on WD via CLDN 14/15 interactions in vivo and in vitro.

METHODS

Using the methods of molecular biology and bioinformatics analysis, we investigated the molecular mechanism by which claudin 14/15 participate in WD. Our previous study showed that claudins 14 and 15 trigger the early signal flow and pathway in damaged sciatic nerves. Here, we report the effects of the interaction between claudin 14 and claudin 15 on nerve degeneration and regeneration during early WD.

RESULTS

It was found that claudin 14/15 were upregulated in the sciatic nerve in WD. Claudin 14/15 promoted Schwann cell proliferation, migration and anti-apoptosis in vitro. PKCα, NT3, NF2, and bFGF were significantly upregulated in transfected Schwann cells. Moreover, the expression levels of the β-catenin, p-AKT/AKT, p-c-jun/c-jun, and p-ERK/ERK signaling pathways were also significantly altered.

CONCLUSION

Claudin 14/15 affect Schwann cell proliferation, migration, and anti-apoptosis via the β-catenin, p-AKT/AKT, p-c-jun/c-jun, and p-ERK/ERK pathways in vitro and in vivo. The results of this study may help elucidate the molecular mechanisms of the tight junction signaling pathway underlying peripheral nerve degeneration.

Effect of the relative position of electrode and stellate ganglion during thermal radiofrequency ablation: a simulation study

PURPOSE

Stellate ganglion (SG) block by thermal radiofrequency ablation (RFA) is frequently conducted as a therapeutic intervention for sympathetic-maintained and neuropathic pain syndromes. RFA's partial lack of effectiveness could be partly due to the ablation zone (AZ) not completely covering the SG section and therefore preventing the 'cutting' of the afferent pathways. Our objective was to build a theoretical model to conduct computer simulations to assess the effect of the electrode position relative to the SG.

METHODS

A three-dimensional model was built including the SG and adjacent tissues (vertebrae C7-T1-T2, trachea, carotid artery and vertebral artery). RFA (90-s, 80 °C) was simulated considering a 22 G-5 mm electrode. The AZ was computed using the 50 °C isotherm.

RESULTS

An electrode displacement of 2 mm in any direction from the optimal position (centered on the SG) meant that the AZ did not fully cover the SG section. Likewise, SG size considerably affected the RFA effectiveness since the AZ fully covered the section of small but not large SGs.

CONCLUSIONS

The findings suggest that the currently used SG RFA settings (i.e., 22 G-5 mm electrode, 90-s, 80 °C) may not be appropriate due to their inability to achieve an AZ that fully covers the SG cross section under certain circumstances, such as a large SG and non-optimal positioning of the RF electrode with respect to the SG center.

Efficacy and Safety of Cryoneurolysis for Treatment of Chronic Head Pain Secondary to Occipital Neuralgia: A Pilot Study

Purpose

Treatment of chronic pain associated with occipital neuralgia (ON) is complex, and no consensus statement or guidelines have been published for ON management. This pilot study evaluated the efficacy and safety of cryoneurolysis for management of ON-associated chronic pain.

Patients and Methods

The study was a prospective, multicenter, nonrandomized cohort study assessing the degree and duration of clinical effect of cryoneurolysis therapy for reducing pain in patients diagnosed with unilateral or bilateral ON. The primary outcome measure was improvement in pain due to ON from baseline to day 7, measured on an 11-point numeric rating scale for pain. Secondary outcome measures included duration of treatment effects and safety events, including anticipated observations and adverse events. Treatment effect was assessed at days 7, 30, and 56 by asking the patient if they were continuing to experience a treatment effect, with potential responses of “effect,” “no effect,” or “no longer effective.” A posttreatment questionnaire evaluated patient satisfaction.

Results

Twenty-six patients (9 men, 17 women) with a mean age of 49.1 years enrolled and completed the study. A total of 64% (16/25) of participants reported a clinically important improvement of ≥2 points in numeric rating scale pain scores at day 7; similar results persisted to day 30. Treatment effects were reported by 50% (13/26) of participants at day 30, with a continued effect reported by 35% (9/26) of participants at day 56. Overall, ~70% of participants were satisfied with treatment at 7, 30, and 56 days. No serious anticipated observations, adverse events, or unanticipated adverse device effects were reported.

Conclusion

Cryoneurolysis provided significant relief from pain associated with ON ≤30 days after treatment and had an acceptable safety profile.

Radiofrequency ablation may improve the beneficial results of vertebroplasty for vertebral hemangiomas: analysis of 46 patients

OBJECTIVES

To evaluate the effect of vertebroplasty (VP) alone or combined therapy of radiofrequency ablation (RFA) with vertebroplasty on pain relief with visual analog scale (VAS) and Oswestry Disability Index (ODI) scores in vertebral hemangiomas.

METHODS

Forty-six patients with hemangiomas were evaluated retrospectively: 20 males and 26 females were included. In group 1 (n = 25) only VP was performed, while RFA+VP were performed in the same treatment session in group 2 (n = 21). Radiological diagnosis was performed with X-ray, CT-scan and MRI images in all patients. The intensity of pain was assessed with the VAS together with the assesment of life quality with the ODI. The assesments were performed before, at first day, at first month and 6 months after treatment.

RESULTS

There was no significant difference between mean preprocedural VAS and ODI scores, but a significant decrease was seen in postprocedural VAS and ODI scores between group 1 and 2, when compared with the preprocedural values. Although lack of a statistically significant difference in long term results, mean VAS score was 3.7 for group 1, while it was 1.8 for group 2, and the mean ODI score was 38 for group 1, and 22.48 for group 2 at 6th month assesment.

DISCUSSION

Although minimally invasive percutaneous techniques are indicated as other modalities are ineffective or contraindicated, combining RFA with vertebral augmentation provide prevention of mechanical loading pain, and prevention of somatic pain in patients with spinal hemangiomas.

Peripheral Nerve Focused Ultrasound Lesioning-Visualization and Assessment Using Diffusion Weighted Imaging

Objectives: Magnetic resonance-guided focused ultrasound (MRgFUS) is a non-invasive targeted tissue ablation technique that can be applied to the nervous system. Diffusion weighted imaging (DWI) can visualize and evaluate nervous system microstructure. Tractography algorithms can reconstruct fiber bundles which can be used for treatment navigation and diffusion tensor imaging (DTI) metrics permit the quantitative assessment of nerve microstructure in vivo. There is a need for imaging tools to aid in the visualization and quantitative assessment of treatment-related nerve changes in MRgFUS. We present a method of peripheral nerve tract reconstruction and use DTI metrics to evaluate the MRgFUS treatment effect. Materials and Methods: MRgFUS was applied bilaterally to the sciatic nerves in 6 piglets (12 nerves total). T1-weighted and diffusion images were acquired before and after treatment. Tensor-based and constrained spherical deconvolution (CSD) tractography algorithms were used to reconstruct the nerves. DTI metrics of fractional anisotropy (FA), and mean (MD), axial (AD), and radial diffusivities (RD) were measured to assess acute (<1-2 h) treatment effects. Temperature was measured in vivo via MR thermometry. Histological data was collected for lesion assessment. Results: The sciatic nerves were successfully reconstructed in all subjects. Tract disruption was observed after treatment using both CSD and tensor models. DTI metrics in the targeted nerve segments showed significantly decreased FA and increased MD, AD, and RD. Transducer output power was positively correlated with lesion volume and temperature and negatively correlated with MD, AD, and RD. No correlations were observed between FA and other measured parameters. Conclusions: DWI and tractography are effective tools for visualizing peripheral nerve segments for targeting in non-invasive surgical methods and for assessing the microstructural changes that occur following MRgFUS treatment.

Preoperative facet joint arthropathy does not impact long-term clinical outcomes after lumbar-stability-preserving decompression and dynesys fixation

To evaluate the impact of the preoperative severity of facet joint arthropathy on long-term functional outcomes and spinopelvic parameters in patients undergoing lumbar-stability-preserving decompression and Dynesys fixation. In this retrospective study, 88 patients undergoing combined surgery at our hospital from 2008 to 2015 were included. The patients were divided into two groups, the less and more than mean degeneration groups, based on preoperative facet joint arthropathy of the index level(s). The clinical outcomes were the Visual Analogue Scale (VAS) score, the Oswestry Disability Index (ODI) score and spinopelvic parameters. The mean follow-up durations for the less and more than mean degeneration groups were 84.83 ± 27.58 and 92.83 ± 20.45 months, respectively. The combined surgery significantly improved VAS and ODI scores, and increased sacral slope (SS) regardless of preoperative arthropathy severity. In addition, facet joint arthropathy at adjacent levels continued to worsen after surgery in both arthropathy severity groups. Preoperative facet joint arthropathy did not influence most long-term clinical outcomes in patients undergoing lumbar-stability-preserving decompression and Dynesys fixation. This combined surgery may be suitable for patients with facet joint arthropathy regardless of disease severity.

Ultrasound-guided pulsed radiofrequency of the saphenous nerve in a complex regional pain syndrome patient with lower limb pain

Complex regional pain syndrome is a painful and debilitating syndrome in which the patient presents with disabling pain, edema, and/or vasomotor or sudomotor abnormalities. The mechanism is complex and not well understood. There is no definitive treatment for the condition yet. Pulsed radiofrequency is a minimally invasive, minimal destructive, and safe intervention. It can be used for neuropathic pain. A 40-year-old man with complex regional pain syndrome complained of intractable pain of the lower limb secondary to injury to the saphenous nerve due to a third-degree burn. Conventional medications, epidural block, and sympathetic nerve block provided temporary relief. We performed pulsed radiofrequency of the saphenous nerve for the management of lower limb pain, and the symptoms remained under control at 3 months. To the best of our knowledge, this is the first application of ultrasound-guided pulsed radiofrequency of the saphenous nerve for the management of complex regional pain syndrome.

Incidence, Diagnosis, and Management of Neuromas Following Radiofrequency Ablation Treatment: a Narrative Review

OBJECTIVE

To determine the epidemiology of neuroma formation as a complication following radiofrequency ablation for chronic pain conditions as well as reviewing the diagnosis and management of neuromas.

DESIGN

Evidence-based narrative review and critical appraisal of literature.

RESULTS

A comprehensive review of the literature generated one case report describing neuroma formation following lumbar facet medial branch radiofrequency denervation. The rare incidence may be explained by neuroma pathophysiology and peripheral nerve injury produced by radiofrequency ablation, in combination with its asymptomatic nature. Diagnosis of neuromas is predominantly confirmed by clinical history and physical exam with potential for nerve blocks or imaging. Ultrasound has been suggested as a primary imaging modality with magnetic resonance imaging as a secondary option. Neuroma management ranges from conservative therapy to surgery with varying success rates.

CONCLUSIONS

Neuroma formation following radiofrequency ablation procedures is exceedingly rare and could be a hypothetical concern in clinical practice. However, the true incidence may be inaccurate given the asymptomatic nature of neuromas.

Optical signatures of radiofrequency ablation in biological tissues

Accurate monitoring of treatment is crucial in minimally-invasive radiofrequency ablation in oncology and cardiovascular disease. We investigated alterations in optical properties of ex-vivo bovine tissues of the liver, heart, muscle, and brain, undergoing the treatment. Time-domain diffuse optical spectroscopy was used, which enabled us to disentangle and quantify absorption and reduced scattering spectra. In addition to the well-known global (1) decrease in absorption, and (2) increase in reduced scattering, we uncovered new features based on sensitive detection of spectral changes. These absorption spectrum features are: (3) emergence of a peak around 840 nm, (4) redshift of the 760 nm deoxyhemoglobin peak, and (5) blueshift of the 970 nm water peak. Treatment temperatures above 100 °C led to (6) increased absorption at shorter wavelengths, and (7) further decrease in reduced scattering. This optical behavior provides new insights into tissue response to thermal treatment and sets the stage for optical monitoring of radiofrequency ablation.

Percutaneous Peripheral Nerve Stimulation of the Medial Branch Nerves for the Treatment of Chronic Axial Back Pain in Patients After Radiofrequency Ablation

OBJECTIVE

Lumbar radiofrequency ablation is a commonly used intervention for chronic back pain. However, the pain typically returns, and though retreatment may be successful, the procedure involves destruction of the medial branch nerves, which denervates the multifidus. Repeated procedures typically have diminishing returns, which can lead to opioid use, surgery, or implantation of permanent neuromodulation systems. The objective of this report is to demonstrate the potential use of percutaneous peripheral nerve stimulation (PNS) as a minimally invasive, nondestructive, motor-sparing alternative to repeat radiofrequency ablation and more invasive surgical procedures.

DESIGN

Prospective, multicenter trial.

METHODS

Individuals with a return of chronic axial pain after radiofrequency ablation underwent implantation of percutaneous PNS leads targeting the medial branch nerves. Stimulation was delivered for up to 60 days, after which the leads were removed. Participants were followed up to 5 months after the start of PNS. Outcomes included pain intensity, disability, and pain interference.

RESULTS

Highly clinically significant (≥50%) reductions in average pain intensity were reported by a majority of participants (67%, n = 10/15) after 2 months with PNS, and a majority experienced clinically significant improvements in functional outcomes, as measured by disability (87%, n = 13/15) and pain interference (80%, n = 12/15). Five months after PNS, 93% (n = 14/15) reported clinically meaningful improvement in one or more outcome measures, and a majority experienced clinically meaningful improvements in all three outcomes (i.e., pain intensity, disability, and pain interference).

CONCLUSIONS

Percutaneous PNS has the potential to shift the pain management paradigm by providing an effective, nondestructive, motor-sparing neuromodulation treatment.

Pain Management in Neurosurgery: Back and Lower Extremity Pain, Trigeminal Neuralgia

Interventional anesthetic techniques are an integral component of a biopsychosocial approach and multidisciplinary treatment. Injection techniques are often used to diagnose disorders, decrease the need for surgery, or increase the time to surgery. The role of neural blockade techniques using local anesthetics and steroids in the assessment and treatment of pain continues to be refined. With the current opioid crisis and an aging population with increasing medical comorbidities, there is an emphasis on the use of nonopioid, nonsurgical, and multimodal therapies to treat chronic pain. This article reviews indications, goals, and methods of common injection techniques.

Meralgia paresthetica treated by injection, decompression, and neurectomy: a systematic review and meta-analysis of pain and operative outcomes

OBJECTIVE

Meralgia paresthetica is caused by entrapment of the lateral femoral cutaneous nerve (LFCN) and often presents with pain. Multiple treatment options targeting the LFCN can be pursued to treat the pain should conservative measures fail, with the most common options being injection, neurolysis, and neurectomy. However, their efficacy in causing pain relief and their clinical outcomes have yet to be directly compared. The aim of this study was to interrogate the contemporary literature and quantitatively define how these options compare.

METHODS

The electronic databases Ovid Embase, PubMed, SCOPUS, and the Cochrane Library were interrogated from inception to May 2020 following the PRISMA guidelines. Candidate articles were screened against prespecified criteria. Outcome data were abstracted and pooled by random-effects meta-analysis of proportions.

RESULTS

There were 25 articles that satisfied all criteria, reporting outcomes for a total of 670 meralgia paresthetica patients, with 78 (12%) treated by injection, 496 (74%) by neurolysis, and 96 (14%) by neurectomy. The incidence of complete pain relief was 85% (95% CI 71%-96%) after neurectomy, 63% (95% CI 56%-71%) after neurolysis, and 22% (95% CI 13%-33%) after injection, which were all statistically different (p < 0.01). The incidence of revision procedures was 12% (95% CI 4%-22%) after neurolysis and 0% (95% CI 0%-2%) after neurectomy, which were significantly lower than 81% (95% CI 64%-94%) after injection (p < 0.01). The incidences of treatment complications were statistically comparable across all three treatments, ranging from 0% to 5% (p = 0.34).

CONCLUSIONS

There are multiple treatment options to target pain in meralgia paresthetica. The incidence of complete pain relief appears to be the greatest among the 3 interventions after neurectomy, accompanied by the lowest incidence of revision procedures. These findings should help inform patient preference and expectations. Greater exploration of the anatomical rationale for incomplete pain relief after surgical intervention will assist in optimizing further surgical treatment for meralgia paresthetica.

A Literature Review of Dorsal Root Entry Zone Complex (DREZC) Lesions: Integration of Translational Data for an Evolution to More Accurate Nomenclature

The purpose of this translational review was to provide evidence to support the natural evolution of the nomenclature of neuromodulatory and neuroablative radiofrequency lesions for pain management from lesions of individualized components of the linear dorsal afferent pathway to “Dorsal Root Entry Zone Complex (DREZC) lesions.” Literature review was performed to collate anatomic and procedural data and correlate these data to clinical outcomes. There is ample evidence that the individual components of the DREZC (the dorsal rami and its branches, the dorsal root ganglia, the dorsal rootlets, and the dorsal root entry zone) vary dramatically between vertebral levels and individual patients. Procedurally, fluoroscopy, the most commonly utilized technology is a 2-dimensional x-ray-based technology without the ability to accurately locate any one component of the DREZC dorsal afferent pathway, which results in clinical inaccuracies when naming each lesion. Despite the inherent anatomic variability and these procedural limitations, the expected poor clinical outcomes that might follow such nomenclature inaccuracies have not been shown to be prominent, likely because these are all lesions of the same anatomically linear sensory pathway, the DREZC, whereby a lesion in any one part of the pathway would be expected to interrupt sensory transmission of pain to all subsequent more proximal segments. Given that the common clinically available tools (fluoroscopy) are inaccurate to localize each component of the DREZC, it would be inappropriate to continue to erroneously refer to these lesions as lesions of individual components, when the more accurate “DREZC lesions” designation can be utilized. Hence, to avoid inaccuracies in nomenclature and until more accurate imaging technology is commonly utilized, the evidence herein supports the proposed change to this more sensitive and inclusive nomenclature, “DREZC lesions.”

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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.

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.

Consensus practice guidelines on interventions for lumbar facet joint pain from a multispecialty, international working group

BACKGROUND

The past two decades have witnessed a surge in the use of lumbar facet blocks and radiofrequency ablation (RFA) to treat low back pain (LBP), yet nearly all aspects of the procedures remain controversial.

METHODS

After approval by the Board of Directors of the American Society of Regional Anesthesia and Pain Medicine, letters were sent to a dozen pain societies, as well as representatives from the US Departments of Veterans Affairs and Defense. A steering committee was convened to select preliminary questions, which were revised by the full committee. Questions were assigned to 4-5 person modules, who worked with the Subcommittee Lead and Committee Chair on preliminary versions, which were sent to the full committee. We used a modified Delphi method, whereby the questions were sent to the committee en bloc and comments were returned in a non-blinded fashion to the Chair, who incorporated the comments and sent out revised versions until consensus was reached.

RESULTS

17 questions were selected for guideline development, with 100% consensus achieved by committee members on all topics. All societies except for one approved every recommendation, with one society dissenting on two questions (number of blocks and cut-off for a positive block before RFA), but approving the document. Specific questions that were addressed included the value of history and physical examination in selecting patients for blocks, the value of imaging in patient selection, whether conservative treatment should be used before injections, whether imaging is necessary for block performance, the diagnostic and prognostic value of medial branch blocks (MBB) and intra-articular (IA) injections, the effects of sedation and injectate volume on validity, whether facet blocks have therapeutic value, what the ideal cut-off value is for a prognostic block, how many blocks should be performed before RFA, how electrodes should be oriented, the evidence for larger lesions, whether stimulation should be used before RFA, ways to mitigate complications, if different standards should be applied to clinical practice and clinical trials and the evidence for repeating RFA (see table 12 for summary).

CONCLUSIONS

Lumbar medial branch RFA may provide benefit to well-selected individuals, with MBB being more predictive than IA injections. More stringent selection criteria are likely to improve denervation outcomes, but at the expense of more false-negatives. Clinical trials should be tailored based on objectives, and selection criteria for some may be more stringent than what is ideal in clinical practice.

Repeat procedures and prescription opioid use after lumbar medial branch nerve radiofrequency ablation in commercially insured patients

PURPOSE

Although the effectiveness of medial branch nerve radiofrequency ablation (RFA) for lumbosacral facet pain has been described, little is known regarding patterns of repeat RFA utilization and prescription opioid use afterward.

DESIGN

Retrospective cohort analysis.

PATIENT SAMPLE

Patients undergoing lumbosacral RFA in MarketScan from 2007 to 2016.

METHODS

The time until and number of staged RFAs (<180 days after initial RFA) and repeat RFAs (≥180 days after initial RFA), as well as opioid use at 90 and 180 days after RFA were assessed. Survival analyses were employed to estimate subsequent RFA rates, whereas subsequent RFA frequencies were estimated with inverse probability weighting. Repeated measures testing was performed comparing opioid use pre- and post-RFA.

RESULTS

Initial RFAs were identified in 44,936 patients. Staged RFAs were performed in 33.1% of patients. Repeat RFAs through 1, 3, and 7 years were performed for 14.6%, 33.5%, and 45.7% of patients, respectively. Within 3 years, 12.2% of patients underwent one repeat RFA, whereas 13.2% of patients underwent two or more. Post-RFA opioid use was examined in 128,310 patients, 32.2% of whom used opioids pre-RFA. By 180 days post-RFA, 8.1% of patients discontinued opioids and 6.7% started opioids (p<.001). Exclusively examining pre-RFA opioid users, 24.9% stopped filling opioid prescriptions 180 days after RFA.

CONCLUSIONS

This study delineates utilization rates of repeat RFA in the commerciall y insured population, with one-third undergoing repeat RFA within 3 years. Additionally, the present data indicate that lumbosacral RFA is associated with reduced filling of opioid prescriptions through 180 days.

Pulsed Radiofrequency Ablation of the C2 Dorsal Root Ganglion Using a Posterior Approach for Treating Cervicogenic Headache: A Retrospective Chart Review

OBJECTIVE

To evaluate the efficacy and complications of C2 dorsal root ganglion (DRG) pulsed radiofrequency ablation (RFA) for cervicogenic headache (CEH) and to identify factors related to the outcome of the procedure in this retrospective analysis.

BACKGROUND

Although conventional high-temperature C2 DRG RFA was effective in patients with CEH in previous studies, the effect of pulsed RFA on C2 DRG in cases of CEH has not yet been evaluated.

METHODS

We examined the electronic medical records of consecutive patients who underwent C2 DRG block for CEH from January 2012 to May 2018 at a pain center. Consequent C2 DRG pulsed RFA was performed for patients in whom the headache recurred after an initial period of relief 24 hours after the C2 DRG block. A successful outcome was defined as at least 50% pain relief at 6 months after C2 DRG pulsed RFA. We also examined variables associated with the outcome and prognostic factors of CEH.

RESULTS

Fluoroscopy-guided C2 DRG block was performed in 114 patients with CEH. Forty-five patients received C2 DRG pulsed RFA and 40.0% among them (18/45, success group) had ≥50% pain relief after 6 months. There were no post-procedure complications throughout the study period. Significantly more patients in the success group than in the failure group had a definite positive response (≥50% pain relief) to a previous C2 DRG block (P < .001).

CONCLUSION

C2 DRG pulsed RFA may be an effective treatment for patients with CEH, particularly for patients who have previously experienced definite pain reduction after C2 DRG block. However, the limitations of our study design and small number of patients preclude firm conclusions.

Radiofrequency Procedures for the Treatment of Symptomatic Knee Osteoarthritis: A Systematic Review

OBJECTIVE

To evaluate the effectiveness and safety of radiofrequency (RF) ablation and neuromodulation modalities for knee osteoarthritis (OA).

METHODS

The Pubmed, Medline, Embase, and Cochrane Library databases were searched from inception to August 2018. All comparative and noncomparative studies that reported clinical outcome measures and adverse events related to RF modalities for knee OA were included. Pain scores, physical function measures, quality of life (QOL), patient satisfaction, and adverse events for three months and beyond of postprocedure follow-up were analyzed qualitatively.

RESULTS

Thirty-three studies, including 13 randomized controlled trials (RCTs), two nonrandomized comparative studies, and 18 noncomparative cohort studies, were identified, with 1,512 patients (mean age = 64.3 years, 32.5% males). All 33 studies were considered to be of moderate or high methodological quality. All 33/33 (100%) studies reported alleviation of OA-related knee pain from baseline until three to 12 months with RF modalities, with six comparative studies reporting 194/296 (65.5%) and 29/150 (19.3%) RF and control patients achieving >50% pain relief, respectively. Three of the 33 studies reported QOL, with three of three studies (100%) achieving improvements in disease-specific QOL from baseline until three to 12 months. Twenty-eight of the 33 studies reported functional outcomes, with 27/28 (96%) studies obtaining enhanced functionality from baseline up until three to 12 months. Ten of the 33 studies reported patient satisfaction, with eight of 10 studies (80%) indicating that patients were significantly satisfied after RF procedures, and from these eight studies, four were comparative studies that indicated that 86/154 (56%) and 33/104 (32%) RF and control patients were extremely satisfied or satisfied, respectively. Regarding adverse events (AEs), 29 of the 33 studies reported AEs, with 20/29 (69%) studies indicating no AEs related to the RF modalities and the remaining nine studies only indicating minor localized AEs. Twenty-nine of the 33 studies indicated no serious knee-related AEs pertaining to RF modalities.

CONCLUSIONS

Current evidence substantiates that RF modalities for knee OA potentially improve pain, functionality, and disease-specific QOL for up to three to 12 months with minimal localized complications. This suggests that RF modalities are perhaps an effective adjunct therapy for patients with knee OA who are unresponsive to conservative therapies. Further RCTs with larger sample sizes and long-term follow-up that directly compare the three primary RF modalities are warranted to confirm the clinical efficaciousness and superiority of these RF modalities for knee OA.

Time-dependent change in pain threshold following neurolytic celiac plexus block

Aim: To determine the long-term effect of ethanol relative to the re-occurrence of pain in postneurolytic celiac plexus block (NCPB) patients. Patients & methods: A noninterventional study on 31 patients who had undergone NCPB to illustrate the average change of pain score over time. Results: All NCPB patients reported a pain score decrease of 83.8% right after the procedure. 73% of patients reported 50-66% decrease in pain 80-100 days postprocedure. The temporal threshold for the return of pain scores to average preblock level was determined to be 103 post-NCPB procedure days. Conclusion: In this study, NCPB patients demonstrate return of pain to baseline subsequent to the analgesic effects of ethanol after a mean 103 days.

Initial experience of CT-guided pulsed radiofrequency ablation of the pudendal nerve for chronic recalcitrant pelvic pain

AIM

To evaluate initial experience with computed tomography (CT)-guided pulsed radiofrequency ablation (pRFA) of the pudendal nerve in cases of recalcitrant neuropathic pelvic pain. Endpoints include technical feasibility, safety, and efficacy of therapy.

MATERIALS AND METHODS

Ten patients who underwent pRFA ablation for neuropathic pudendal nerve pain during the trial period were followed for response to treatment for 6 months. Each patient was treated with pRFA under CT-guidance with concurrent perineural injection of anaesthetic and/or corticosteroid. Pain scores were then measured using a numeric rating scale at fixed intervals up to 6 months.

RESULTS

All procedures were considered technically successful with no immediate complications. pRFA demonstrated improved duration of pain improvement compared to the most recent perineural injection (p=0.0195), but not compared to the initial injection (p=0.64). Reported pain scores were lower with pRFA than with both the first and most recent injection but this did not reach statistical significance (p=0.1094 and p=0.7539, respectively).

CONCLUSION

Overall, pRFA of the pudendal nerve using CT-guidance can be a safe and effective therapy. This technique provides direct visualisation of the nerve to maximise safety and efficacy while offering a novel form of therapy for patients with chronic, recalcitrant pelvic pain.

Histological, electrophysiological and clinical effects of thermal radiofrequency therapy of the saphenous nerve and pulsed radiofrequency therapy of the sciatic nerve in dogs

OBJECTIVE

Thermal radiofrequency (TRF) of the saphenous nerve (a sensory nerve) combined with pulsed radiofrequency (PRF) of the sciatic nerve (a sensory and motor nerve) might relieve intractable stifle osteoarthritis (OA) pain in dogs. The objective was to determine if saphenous nerve TRF induces Wallerian degeneration and if sciatic nerve PRF induces degeneration or dysfunction.

STUDY DESIGN

Blinded, controlled, randomized, preclinical study.

ANIMALS

A group of six intact, female Beagle dogs aged 14-16 months.

METHODS

In each dog, one pelvic limb was assigned randomly to the control group and the other to the treatment group. Dogs were anesthetized and, using ultrasonography, radiofrequency electrodes were positioned adjacent to saphenous and sciatic nerves bilaterally; TRF and PRF were performed only in the treatment limb. Motor nerve conduction velocity (MNCV) was measured in both sciatic nerves 2 weeks later, and the dogs were euthanized. Hematoxylin and eosin-stained sections of saphenous and sciatic nerves were examined using light microscopy. Degeneration and inflammation were scored 0 (none) to 3 (severe). A one-tailed, paired Wilcoxon signed-rank test was used to test for differences in scores and MNCV between control and treatment nerves.

RESULTS

Degeneration and inflammation scores were higher in treatment saphenous nerves in 5/6 dogs [83%; 95% confidence interval (CI), 36%, 99%]; however, after Bonferroni correction only degeneration score was higher (p = 0.0313). Degeneration, inflammation or decreased MNCV were not observed in sciatic nerves (each outcome: 0/6 nerves, 0%; 95% CI, 0%, 48%). No dogs experienced postprocedural pain or neurological deficits.

CONCLUSIONS AND CLINICAL RELEVANCE

The degeneration in TRF-treated saphenous nerves appears sufficient to impair transmission. Sciatic nerve PRF did not cause degeneration with attendant motor deficits, consistent with a proposed neuromodulatory mechanism. A clinical trial is needed to confirm the combined techniques produce analgesia without motor deficits in dogs with stifle OA.

Advances in Pain Management: Palliative Care Applications

One of the most important goals of palliative medicine and hospice care is pain relief. Although great strides have been made in veterinary analgesia, severe pain, especially at home, is still difficult to control. Pain control in the context of palliative medicine and hospice care is far more advanced in human medicine. Many modalities used in chronically or terminally ill humans might be adapted to animals to better manage severe pain. This article discusses drugs and procedures used to control pain in humans that are relatively nascent or unavailable in veterinary medicine and deserve further attention.