Spinal cord and peripheral nerve stimulation techniques for neuropathic pain

Retrospective Evaluation of Bipolar Peripheral Nerve Stimulation for Nociceptive and Neuropathic Pain: A Pilot Study

Purpose

This retrospective review evaluates pain and patient-defined functional goal improvement utilizing bipolar peripheral nerve stimulation (PNS) in chronic neuropathic and nociceptive pain states.

Patients and Methods

Our dataset includes 24 patients who underwent implantation of a permanent peripheral nerve stimulator from January 2018 through December 2022. A total of 29 leads were implanted amongst 24 patients, with 5 patients having leads at 2 different dermatomes. Fifteen leads were placed for primarily neuropathic pain, and 14 leads were placed for nociceptive pain. Inclusion criteria were the following: pain duration greater than 6 months, documented peri-procedural Numerical Pain Rating Scale (NPRS) and greater than 60 days follow-up post implant.

Results

Data was collected and analyzed showing that 89.6% of implants at 6 months follow-up and 70% at 12 months follow-up achieved 50% or greater pain relief. A significant reduction in NPRS scores when comparing pre-procedure pain scores (Median = 7, n = 29) to 6-month follow-up data (Median = 2, n = 29), p<0.001 with a large effect size, r = 0.61. Ninety-three percent of patients reported achieving their personal functional goal. Twelve of the fourteen (86%) leads implanted for primary nociceptive pain and fourteen of the fifteen (93%) leads implanted for neuropathic pain achieved ≥50% relief at 6 months. At twelve months, seven leads in each group provided ≥50% sustained pain relief. Of the 14 patients that were on opioids, 6 discontinued, while another 2 had a reduction in oral morphine milligram equivalents (MME) at the 12-month follow-up.

Conclusion

This retrospective review demonstrates the potential clinical application of PNS in both nociceptive and neuropathic pain states. Further prospective studies are warranted to validate the effectiveness of PNS in the treatment of refractory nociceptive and neuropathic pain states.

Mechanism of Action of Peripheral Nerve Stimulation for Chronic Pain: A Narrative Review

The use of stimulation of peripheral nerves to test or treat various medical disorders has been prevalent for a long time. Over the last few years, there has been growing evidence for the use of peripheral nerve stimulation (PNS) for treating a myriad of chronic pain conditions such as limb mononeuropathies, nerve entrapments, peripheral nerve injuries, phantom limb pain, complex regional pain syndrome, back pain, and even fibromyalgia. The ease of placement of a minimally invasive electrode via percutaneous approach in the close vicinity of the nerve and the ability to target various nerves have led to its widespread use and compliance. While most of the mechanism behind its role in neuromodulation is largely unknown, the gate control theory proposed by Melzack and Wall in the 1960s has been the mainstay for understanding its mechanism of action. In this review article, the authors performed a literature review to discuss the mechanism of action of PNS and discuss its safety and usefulness in treating chronic pain. The authors also discuss current PNS devices available in the market today.

Outcome of Surgical Treatments of Chronic Pain Caused by Trigeminal Neuropathy

BACKGROUND

Trigeminal neuropathy represents a subset of several facial pain syndromes that are difficult to diagnose and treat. Although many surgical modalities are available, outcomes remain suboptimal. The aim of this study is to present our experience in management of trigeminal neuropathy with a focus on the effectiveness and long-term efficacy of the different surgical procedures.

METHODS

A single-center retrospective cohort study was conducted from December 2012 until February 2020.

RESULTS

Twenty-eight patients (19 females, 9 males) were included in this study. They had 40 surgical interventions. At last follow-up, 1 patient (33.3%) treated by spinal cord stimulation (SCS) had no pain recurrence and 2 patients (66.6%) had their devices removed because of therapeutic failure. Median time to pain recurrence after SCS was 19.5 months (interquartile range [IQR], 29.79 months). Six patients were treated with peripheral nerve stimulation (PNS). At last follow-up, 2 patients had satisfactory pain relief, whereas half of the patients had no improvement. For the 17 patients treated with computed tomography-guided trigeminal tractotomy/nucleotomy, true failure occurred 7 times in 6 patients. Median time to pain recurrence was 5.6 months (IQR, 6.2). Of the 6 patients treated with caudalis DREZ, 3 (50%) had satisfactory pain relief for >1 year and the median time to pain recurrence was 3.9 months (IQR, 29.53).

CONCLUSIONS

Trigeminal neuropathy is a difficult to treat entity of facial pain syndromes. The long-term efficacy of available interventions does not meet patients' satisfaction. More organized prospective studies with longer follow-up are needed to define the patient population best served by each surgical modality.

American Society of Regional Anesthesia and Pain Medicine 2021 John J. Bonica Award Lecture

I am as deeply inspired and humbled to receive this prestigious award, as I am profoundly indebted to the Bonica Award selection committee and the American Society of Regional Anesthesia and Pain Medicine Board of Directors for recognizing my contributions to the development, teaching, and practice of pain medicine in the tradition of Dr John J Bonica. I would also like to recognize my parents, Aura and Tito for providing me with the support and the environment to fulfill my professional goals. Moreover, the support that I have gotten from my team at the hospital, and the Chair of my Department, Dr Mark Lema needs to be underscored.

Educational Curriculum for Peripheral Nerve Stimulation Developed by the North American Neuromodulation Society

BACKGROUND

Peripheral nerve stimulation (PNS) is an effective neuromodulation therapy for chronic neuropathic and nociceptive pain. Although the total number of PNS implantations has increased over the last decade, no curriculum exists to guide training and learning of this therapy. The goal of the North American Neuromodulation Society (NANS) education committee is to develop a series of competency-based curriculums for neuromodulation therapies. The PNS curriculum is the latest part of such series, following the curriculums for spinal cord stimulation and intrathecal drug delivery system.

MATERIALS AND METHODS

A multidisciplinary task force (anesthesiology, physical medicine and rehabilitation, neurosurgery, preventive medicine and public health, and neurology) was created by the educational committee of NANS to develop a PNS curriculum in accordance with the Accreditation Council for Graduate Medical Education (ACGME) milestones. The curriculum was created based on the best available evidence and expert knowledge (from our task force members) of available PNS systems. The final PNS curriculum was approved by the NANS board.

RESULTS

A PNS curriculum was developed by the task force. Milestones included professionalism, practice-based learning, interpersonal communication, medical knowledge, systems-based practice, procedural skills, and patient care. Each milestone was defined into three categories: early learner, advanced learner, and practitioner.

CONCLUSIONS

This manuscript provides a PNS training curriculum developed by a multidisciplinary task force of the NANS educational committee in accordance with the milestones described by ACGME for basic learners, advanced learners, and practitioners. This curriculum will help provide a structured training and evaluation process for obtaining proficiency in PNS treatment(s).

A Review of Medical and Surgical Options for the Treatment of Facial Pain

Facial pain is a common medical complaint that is easily misdiagnosed. As a result, this pain often goes mistreated. Despite this, there are a variety of pharmacologic, surgical, and neuromodulatory options for the treatment of facial pain. In this review, the authors detail the forms of facial pain and their treatment options. They discuss the common medications used in the first-line treatment of facial pain and the second-line surgical and neuromodulatory options available to patients when pharmacologic options fail.

Anchoring of a mental nerve stimulator for treatment of facial neuropathic pain: a case illustration

INTRODUCTION

Mental nerve stimulation is recognised as a treatment option for neuropathic facial pain. Historically however, lead migration across the mobile temporomandibular joint has prevented this procedures utility.

METHODS

We describe a new method of insertion and anchoring of a mental nerve stimulator for the management of refractory neuropathic pain in the distribution of the mental nerve. We anchored the stimulator lead to the mandibular body.

RESULTS

Significant analgesic effect was achieved and no lead migration had occurred at 1 year post-operatively.

CONCLUSIONS

This report describes in detail the procedure of mental nerve stimulator insertion, with a novel technique of mandibular anchoring of the lead.

Comparison of Paresthesia Mapping With Anatomic Placement in Burst Spinal Cord Stimulation: Long-Term Results of the Prospective, Multicenter, Randomized, Double-Blind, Crossover CRISP Study

OBJECTIVES

Spinal cord stimulation (SCS) is an effective therapy for chronic intractable pain. Conventional SCS involves electrode placement based on intraoperative paresthesia mapping; however, newer paradigms like burst may allow for anatomic placement of leads. Here, for the first time, we report the one-year safety and efficacy of burst SCS delivered using a lead placed with conventional, paresthesia mapping, or anatomic placement approach in subjects with chronic low back pain (CLBP).

MATERIALS AND METHODS

Subjects with CLBP were implanted with two leads. The first lead was placed to cross the T8/T9 disc and active contacts for this lead were chosen through paresthesia mapping. The second lead was placed at the T9/T10 spinal anatomic landmark. Subjects initially underwent a four-week, double-blinded, crossover trial with a two-week testing period with burst SCS delivered through each lead in a random order. At the end of trial period, subjects expressed their preference for one of the two leads. Subsequently, subjects received burst SCS with the preferred lead and were followed up at 3, 6, and 12 months. Pain intensity (visual analog scale), quality-of-life (EuroQol-5D instrument), and disability (Oswestry Disability Index) were evaluated at baseline and follow-up.

RESULTS

Forty-three subjects successfully completed the trial. Twenty-one preferred the paresthesia mapping lead and 21 preferred the anatomic placement lead. Anatomic placement lead was activated in one subject who had no preference. The pain scores (for back and leg) significantly improved from baseline for both lead placement groups at all follow-up time points, with no significant between-group differences.

CONCLUSIONS

This study demonstrated that equivalent clinical benefits could be achieved with burst SCS using either paresthesia mapping or anatomic landmark-based approaches for lead placement. Nonparesthesia-based approaches, such as anatomic landmark-based lead placement investigated here, have the potential to simplify implantation of SCS and improve current surgical practice.

Peripherally Induced Reconditioning of the Central Nervous System: A Proposed Mechanistic Theory for Sustained Relief of Chronic Pain with Percutaneous Peripheral Nerve Stimulation

Peripheral nerve stimulation (PNS) is an effective tool for the treatment of chronic pain, although its efficacy and utilization have previously been significantly limited by technology. In recent years, purpose-built percutaneous PNS devices have been developed to overcome the limitations of conventional permanently implanted neurostimulation devices. Recent clinical evidence suggests clinically significant and sustained reductions in pain can persist well beyond the PNS treatment period, outcomes that have not previously been observed with conventional permanently implanted neurostimulation devices. This narrative review summarizes mechanistic processes that contribute to chronic pain, and the potential mechanisms by which selective large diameter afferent fiber activation may reverse these changes to induce a prolonged reduction in pain. The interplay of these mechanisms, supported by data in chronic pain states that have been effectively treated with percutaneous PNS, will also be discussed in support of a new theory of pain management in neuromodulation: Peripherally Induced Reconditioning of the Central Nervous System (CNS).

Refractory neuropathic pain from a median nerve injury: spinal cord or peripheral nerve stimulation? A case report

Spinal cord stimulation (SCS) is the most frequently used neuromodulation technique even for neurogenic pain from a peripheral nerve injury although peripheral nerve stimulation (PNS) has been designed for this purpose. PNS appears less invasive than SCS or deep brain stimulation. It provides greater and specific target coverage and it could be more cost-effective than SCS because low electrical stimulation is exclusively delivered to the precise painful territory. We report a case of excellent result following median nerve stimulation at arm level after SCS failure and a 10-year history of intense pain. PNS would certainly have been considered much earlier if it was accepted and reimbursed by the Belgium National Insurance. PNS is a safe, simple, and efficient technique available for decades but it is still considered as experimental and underemployed. Belgian National Insurance fears an explosion of indications on neuromodulation if PNS was reimbursed. We consider that PNS aside SCS and other neuromodulation techniques should be made available in Belgium in case of peripheral chronic neuropathic pain.

Phrenic Nerve Blockade to Diagnose and Treat Diaphragmatic Pain After Surgical Repair of Congenital Diaphragmatic Eventration

A 46-year-old woman presented with pain in the lateral side of the left chest wall and a sensation of fullness and pulling in the epigastric region, which started 4 weeks following diaphragmatic plication for left diaphragmatic eventration. The patient was diagnosed as suffering from post-thoracotomy pain syndrome (PTPS). A diagnostic intercostal nerve block relieved the chest wall pain, but not the epigastric pain. After a detailed evaluation, the epigastric pain was postulated to be of diaphragmatic origin and hence a diagnostic phrenic nerve block was performed which relieved the epigastric pain. Combined intercostal nerve neurolysis and phrenic nerve block relieved her pain completely. The phrenic nerve may play a role in pain transmission and the genesis of chronic pain following diaphragmatic surgery. Diaphragmatic pain following surgery may contribute to the development of chronic pain. Phrenic nerve blockade provides diagnostic information regarding the etiology of pain as well as being effective in providing analgesia. The technique of phrenic nerve block is presented and its role in the diagnosis and treatment of pain following thoracic surgery is reviewed.

Effectiveness of Neurostimulation Technologies for the Management of Chronic Pain: A Systematic Review

OBJECTIVES

To describe the state of the literature for clinical effectiveness of neurostimulation used for the management of chronic pain.

METHODS

A systematic review of spinal cord stimulation (SCS), peripheral nerve stimulation (PNS), peripheral nerve field stimulation (PNFS), and supraorbital transcutaneous electrical nerve stimulation in patients with cancer and noncancer chronic pain was conducted. MEDLINE, Embase, CINAHL, and the Cochrane CENTRAL Register of Controlled Trials were searched, using terms like "electrical stimulation therapy" and "pain management." Direction of effect, consistency across studies, and strength of evidence for effects of neurostimulation on chronic pain were narratively synthesized.

RESULTS

A total of 15 randomized controlled trials (RCTs) examining SCS, 7 RCTs examining PNS/PNFS, and 1 nonrandomized trial examining supraorbital transcutaneous electrical nerve stimulation (TENS) were included. In nine SCS studies, neurostimulation had positive effects on pain. In three studies, neurostimulation did not significantly reduce pain. For PNS/PNFS, five studies found improvements in pain offered by neurostimulation; pain outcomes were not reported in two studies. In the TENS study, neurostimulation reduced headaches per month and medication consumption. Overall, 21 studies were of low or unclear risk of bias, 4 were high risk of bias, and the TENS study was not appropriate for assessment using the Cochrane Risk of Bias tool.

CONCLUSIONS

A robust body of evidence examining SCS and PNS was identified. Only one study for PNFS and TENS was identified; both reported pain reductions. Generally, neurostimulation improved pain control. Future studies should examine the effectiveness of neurostimulation offered early in the trajectory of chronic pain.

A Retrospective Case Series of a Novel Spinal Cord Stimulator Trial Technique with Less Displacement and Migration of the Trial Leads

Background

Spinal cord stimulation is an established treatment option for certain chronic pain conditions which have been previously unresponsive to conservative therapies or potentially for a subset of patients who have not improved following spine surgery. Prior to permanent lead implantation, stimulator lead trials are performed to ensure adequate patient benefit. During these trials, one of the most common complications and reasons for failure is the displacement and migration of the trial leads, resulting in lost therapeutic coverage. Other complications include infection and dislodged bulky dressings. There is a paucity of literature describing an adequate procedural method to prevent these common complications.

Objective

This study utilizes a series of 19 patients to evaluate a new technique for securing percutaneous spinal cord simulator trial leads, which may minimize dislodgement and migration complications and improve the rate of trial success.

Study Design

Retrospective case series.

Setting

New Jersey Medical School, Department of Anesthesiology, Pain Management Division.

Methods

A retrospective chart review was conducted on 19 consecutive patients undergoing placement of the percutaneous thoracic spinal cord stimulator trial leads for pain associated with lumbar spine pathology over a two-year period (2010–2012).

Results

Of the 19 patients in our cohort, there was one trial lead displacement, no lead migrations, and no site infections. Thirteen patients went on to permanent lead implantation. This improved trial lead placement technique had a high success rate with a low number of complications.

Limitations

Small sample size, retrospective case series, and no control group for comparison.

Conclusion

This case series was able to demonstrate that our described novel spinal cord stimulator trial lead placement and dressing technique can decrease the incidence of lead displacement and migration, thus improving trial success.

Scrambler therapy for the treatment of neuropathic pain related to leukemia in a pediatric patient: A case report

RATIONALE

Cancer-related neuropathic pain often responds poorly to standard pain treatments. Scrambler therapy has relieved refractory chronic pain in several uncontrolled clinical trials.

PATIENT CONCERNS

An 11-year-old female patient was suffering from left groin and medial thigh pain after irradiation to the knee. The girl was diagnosed with precursor B-cell lymphoblastic leukemia 2 years ago. Extramedullary relapse of leukemia developed 1 month ago and pain had started. She was treated with oral medications, but she was continuously complaining of severe pain.

DIAGNOSIS

Neuropathic pain caused by obturator nerve involvement in leukemia.

INTERVENTION

Scrambler therapy.

OUTCOME

Pain reduction.

LESSONS

Scrambler therapy is noninvasive, is not associated with any complications, causes minimal discomfort during treatment, and is very effective in a pediatric patient with cancer-related neuropathic pain.

Novel technique for trialing peripheral nerve stimulation: ultrasonography-guided StimuCath trial

OBJECTIVE

Peripheral nerve stimulation (PNS) has been used for the treatment of neuropathic pain for many decades. Despite the specific indications for PNS, clinicians often have difficulty screening for candidates likely to have a good or fair outcome. Given the expense of a permanent implant, most insurance companies will not pay for the implant without a successful PNS trial. And since PNS has only recently been approved by the US Food and Drug Administration, many insurance companies will not pay for a conventional trial of PNS. The objective of this study is to describe a short low-cost method for trialing and screening patients for peripheral nerve stimulator implantation. Additionally, this study demonstrates the long-term efficacy of PNS in the treatment of chronic neuropathic pain and the relative effectiveness of this novel screening method.

METHODS

The records of all patients who had undergone trialing and implantation of a PNS system for chronic refractory pain at the authors' institution over a 1-year period (August 1, 2012–July 31, 2013) were examined in this retrospective case series. The search revealed 17 patients, 13 who had undergone a novel in-office ultrasonography-guided StimuCath screening technique and 4 who had undergone a traditional week-long screening procedure. All 17 patients experienced a successful PNS trial and proceeded to permanent PNS system implantation. Patients were followed up for a mean duration of 3.0 years. Visual analog scale (VAS) pain scores were used to assess pain relief in the short-term (< 6 weeks), at 1 year, and at the last follow-up. Final outcome was also characterized as good, fair, poor, or bad.

RESULTS

Of these 17 patients, 10 were still using their stimulator at the last follow-up, with 8 of them obtaining good relief (classified as ≥ 50% pain relief, with an average 81% reduction in the VAS score) and 2 patients attaining fair relief (< 50% relief but still using stimulation therapy). Among the remaining 7 patients, the stimulator had been explanted in 4 and there had been no relief in 3. Excluding explanted cases, follow-up ranged from 14 to 46 months, with an average of 36 months. Patients with good or fair relief had experienced pain prior to implantation for an average of 5.1 years (range 1.8–15.2 years). A longer duration of pain trended toward a poorer outcome (bad outcome 7.6 years vs good outcome 4.1 years, p = 0.03). Seven (54%) of the 13 patients with the shorter trial experienced a good or fair outcome with an average 79% reduction in the VAS score; however, all 4 of the bad outcome cases came from this group. Three (75%) of the 4 patients with the longer trial experienced a good or fair outcome at the last follow-up, with an average 54% reduction in the VAS score. There was no difference between the trialing methods and the proportion of favorable (good or fair) outcomes (p = 0.71).

CONCLUSIONS

Short, ultrasonography-guided StimuCath trials were feasible in screening patients for permanent implantation of PNS, with efficacy similar to the traditional week-long screening noted at the 3-year follow-up.

Epidural spinal cord stimulation for neuropathic pain: a neurosurgical multicentric Italian data collection and analysis

BACKGROUND

Spinal cord stimulation (SCS) is a technique used worldwide to treat several types of chronic neuropathic pain refractory to any conservative treatment. The aim of this data collection is to enforce evidence of SCS effectiveness on neuropathic chronic pain reported in the literature and to speculate on the usefulness of the trial period in determining the long-term efficacy. Moreover, the very low percentage of undesired side effects and complications reported in our case series suggests that all implants should be performed by similarly well-trained and experienced professionals.

METHOD

A multicentric data collection on a common database from 11 Italian neurosurgical departments started 3 years ago. Two different types of electrodes (paddle or percutaneous leads) were used. Of 122 patients, 73 % (N = 89) were submitted to a trial period, while the remaining patients underwent the immediate permanent implant (N = 33). Statistical comparisons of continuous variables between groups were performed.

RESULTS

Most of the patients (80 %) had predominant pain to their lower limbs, while only 17 % of patients had prevalent axial pain. Significant reduction in pain, as measured by variation in visual analogue scale (VAS) score, was observed at least 1 year after implantation in 63.8 % of the cases, 59.5 % of patients who underwent a test trial and 71.4 % of patients who underwent permanent implant at once. No statistical differences were found between the lower-limb pain group and the axial pain group.

CONCLUSIONS

No relevant differences in long-term outcomes were observed in previously tested patients compared with patients implanted at once. Through this analysis we hope to recruit new centres, to give more scientific value to our results.

10-kHz High-Frequency SCS Therapy: A Clinical Summary

Objective

Chronic pain remains a serious public health problem worldwide. A spinal cord stimulation (SCS) therapy called HF10 SCS uses 10-kHz high-frequency stimulation to provide pain relief without paresthesia. In this article, we describe the therapy, device, and the methods of implant and then review the safety and effectiveness data for this therapy.

Results

HF10 SCS uses a charge-balanced stimulation waveform that has been shown to be safe in both animal and human studies. Data from a multicenter, prospective clinical trial shows that the therapy provides substantial back and leg pain relief. Numerous additional reports suggest improved pain relief in other body areas and for complex pain patterns, even for patients who have previously failed other neuromodulation therapies.

Conclusions

The clinical experience reported in this article supports the efficacy and pain relief provided by HF10 SCS therapy. Clinical studies have also concluded that HF10 SCS does not generate paresthesia nor was it necessary to provide adequate coverage for pain relief. As clinical evidence accumulates and technological innovation improves patient outcomes, neuromodulatory techniques will be sought earlier in the treatment continuum to reduce the suffering for the many with otherwise intractable chronic pain.

Introduction to neuropathic pain syndromes

Chronic pain impairs the quality of life for millions of individuals and therefore presents a serious ongoing challenge to clinicians and researchers. Debilitating chronic pain syndromes cost the US economy more than $600 billion per year. This article provides an overview of the epidemiology, clinical presentation, and treatment outcomes for craniofacial, spinal, and peripheral neurologic pain syndromes. Although the authors recognize that the diagnosis and treatment of the chronic forms of neuropathic pain syndromes represent a clinical challenge, there is an urgent need for standardized classification systems, improved epidemiologic data, and reliable treatment outcomes data.

Neuropathic pain in cancer survivors

The occurrence of pain in cancer survivors may be debilitating. These pain syndromes may be of different types, including neuropathic pain. The research related to cancer management has been done extensively in certain areas, but such research in cancer survivors is still lacking. The chronic pain in cancer survivors is not only under-reported but also under-treated. The assessment of pain in cancer survivors is multifaceted because of many domains like physical, social and psychological. Usually, the pain management may be considered similar to that for chronic noncancer pain, but with a caveat that such pain may at times be indicative of cancer recurrence. The multidisciplinary and multimodal management is essential for such neuralgic pain in cancer survivors. This may require a balanced combination of pharmacological and nonpharmacological techniques, including psychological support. The overall goal that remains in such patients for pain management is to improve the quality of life. Here we review certain pertinent aspects of neuropathic pain in cancer survivors.

Managing pain after thoracic surgery

SUMMARY It is generally accepted that thoracic surgery for lung cancer produces some of the most intense and difficult perioperative and chronic pain challenges. In the acute period of recovery, practitioners must optimize patient comfort and pulmonary function. This can be achieved through a combination of systemic treatment and regional analgesic options. Thoracic surgery also causes relatively high levels of persistent postsurgical pain. Many of the cases of persistent pain have a clear neuropathic pain mechanism, but a significant number of cases do not. While persistent pain correlates directly with the extent of operative trauma, even video-assisted thoracoscopic surgery approaches can cause chronic pain. Persistent pain is treated with medical and interventional therapies customized to an individual patient’s complaints and medication tolerance.

Scrambler therapy for patients with cancer pain - case series -

More than 80% of cancer patients experience cancer pain. Among them, more than 50% experience moderate to severe pain. To control cancer pain, a variety of methods have been used, including medications and nerve blocks. In some patients, however, it is impossible to perform nerve blocks due to caner metastasis into the epidural space, while in other patients, opioid dose escalation is impossible due to opioid side effects; thus, cancer pain management is difficult. Scrambler therapy is a novel approach for pain control that uses EKG-like pads, which are applied above and below the site of pain. Scrambler therapy synthesizes 16 different types of nerve action potentials that provide "non-pain" information via cutaneous nerves. The advantages of this treatment are that it is non-invasive and safe and has no significant side effects. In this case series, we report the treatment results of using scrambler therapy in three cancer patients with intractable pain.

Muscarinic pain pharmacology: realizing the promise of novel analgesics by overcoming old challenges

The antinociceptive and analgesic effects of muscarinic receptor ligands in human and nonhuman species have been evident for more than half a century. In this review, we describe the current understanding of the roles of different muscarinic subtypes in pain modulation and their mechanism of action along the pain signaling pathway, including peripheral nociception, spinal cord pain processing, and supraspinal analgesia. Extensive preclinical and clinical validation of these mechanisms points to the development of selective muscarinic agonists as one of the most exciting and promising avenues toward novel pain medications.

Scrambler therapy may relieve chronic neuropathic pain more effectively than guideline-based drug management: results of a pilot, randomized, controlled trial

CONTEXT

Neuropathic pain is common, disabling, and often difficult to treat.

OBJECTIVES

To compare guideline-based drug management with Scrambler therapy, a patient-specific electrocutaneous nerve stimulation device.

METHODS

A clinical trial with patients randomized to either guideline-based pharmacological treatment or Scrambler therapy for a cycle of 10 daily sessions was performed. Patients were matched by type of pain including postsurgical neuropathic pain, postherpetic neuralgia, or spinal canal stenosis. Primary outcome was change in visual analogue scale (VAS) pain scores at one month; secondary outcomes included VAS pain scores at two and three months, pain medication use, and allodynia.

RESULTS

Fifty-two patients were randomized. The mean VAS pain score before treatment was 8.1 points (control) and 8.0 points (Scrambler). At one month, the mean VAS score was reduced from 8.1 to 5.8 (-28%) in the control group, and from 8 to 0.7 points (-91%) in the Scrambler group (P<0.0001). At two and three months, the mean pain scores in the control group were 5.7 and 5.9 points, respectively, and 1.4 and 2 points in the Scrambler group, respectively (P<0.0001). More relapses were seen in polyradicular pain than monoradicular pain, but retreatment and maintenance therapy gave relief. No adverse effects were observed.

CONCLUSION

In this pilot randomized trial, Scrambler therapy appeared to relieve chronic neuropathic pain better than guideline-based drug management.

Chemotherapy-induced peripheral neuropathy: prevention and treatment

Chemotherapy-induced peripheral neuropathy (CIPN) is a common, dose-limiting side effect of many chemotherapeutic agents. Although many therapies have been investigated for the prevention and/or treatment of CIPN, there is no well-accepted proven therapy. In addition, there is no universally accepted, well-validated measure for the assessment of CIPN. The agents for which there are the strongest preliminary data regarding their potential efficacy in preventing CIPN are intravenous calcium and magnesium (Ca/Mg) infusions and glutathione. Agents with the strongest supporting evidence for efficacy in the treatment of CIPN include topical pain relievers, such as baclofen/amitriptyline/ketamine gel, and serotonin and norepinephrine reuptake inhibitors, such as venlafaxine and duloxetine. Other promising therapies are also reviewed in this paper. Cutaneous electrostimulation is a nonpharmacological therapy that appears, from an early pilot trial, to be potentially effective in the treatment of CIPN. Finally, there is a lack of evidence of effective treatments for the paclitaxel acute pain syndrome (P-APS), which appears to be caused by neurologic injury.

Managing chronic pain: results from an open-label study using MC5-A Calmare® device

BACKGROUND

Despite state-of-the-art therapeutic strategies for pain, some types of chronic pain remain difficult to treat. We evaluated the effectiveness of an innovative neuromodulative approach to the treatment of chronic pain using electrical stimulus integrated with pharmacological support.

METHODS

The MC5-A Calmare© is a new device for patient-specific cutaneous electrostimulation which, by "scrambling" pain information with "no pain" information, aims to reduce the perception of pain intensity. We prospectively treated 73 patients with cancer- (40) and non-cancer-related (33) pain whose pain management was unsatisfactory. The primary objective of the study was to assess efficacy and tolerability of the device. Pain intensity was assessed daily with a Numerical Rating Scale (NRS) for the duration of treatment (2 weeks) and then on a weekly basis for the 2 weeks of follow-up.

RESULTS

Mean pain value at T0 (pre-treatment value) was 6.2 [± 2.5 SD (standard deviation)], 1.6 (± 2.0) (p < 0.0001) at T2 (after the 10th day of treatment), and 2.9 (± 2.6) (p < 0.0001) at T4 (after the second week of follow-up, i.e., 1 month after the beginning of treatment). Response after the second week of treatment showed a clear reduction in pain for both cancer (mean absolute delta of the reduction in NRS value = 4.0) and non-cancer (mean delta = 5.2) patients. The pain score had decreased by 74% at T2. On the basis of pre-established response criteria, there were 78% of responders at T2 and 81% at T4. No side effects were reported.

CONCLUSIONS

Our preliminary results suggest that cutaneous electrostimulation with the MC5-A Calmare© can be hypothesized as part of a multimodality approach to the treatment of chronic pain. Further studies on larger numbers of patients are needed to assess its efficacy, to quantify the effects of inter-operator variability, and to compare results obtained from the active device versus those from a sham machine.

Duloxetine in the treatment of chronic pain due to fibromyalgia and diabetic neuropathy

Duloxetine is a serotonin-norepinephrine reuptake inhibitor approved by the US Food and Drug Administration for the treatment of fibromyalgia and painful diabetic neuropathy at doses of 60 mg daily. Duloxetine has been shown to significantly improve the symptoms of chronic pain associated with these disorders, as measured by the Fibromyalgia Impact Questionnaire, Brief Pain Inventory scores, the Clinical Global Impressions Scale, and other various outcome measures in several placebo-controlled, randomized, double-blind, multicenter studies. Symptom improvement generally began within the first few weeks, and continued for the duration of the study. In addition, the efficacy of duloxetine was found to be due to direct effects on pain symptoms rather than secondary to improvements in depression or anxiety. Adverse events including nausea, constipation, dry mouth, and insomnia, were mild and transient and occurred at relatively low rates. In conclusion, duloxetine, a selective inhibitor for the serotonin and norepinephrine transporters, is efficacious in the treatment of chronic pain associated with fibromyalgia or diabetic neuropathy, and has a predictable tolerability profile, with adverse events generally being mild to moderate.

Pilot trial of a patient-specific cutaneous electrostimulation device (MC5-A Calmare®) for chemotherapy-induced peripheral neuropathy

CONTEXT

Chemotherapy-induced peripheral neuropathy (CIPN) is a major dose-limiting and persistent consequence of numerous classes of antineoplastic agents, affecting up to 30%-40% of patients. To date, there is no effective prevention or therapy. An evolving hypothesis for reducing CIPN pain involves direct nerve stimulation to reduce the pain impulse.

OBJECTIVES

To evaluate the impact on CIPN associated with the MC5-A Calmare® therapy device.

METHODS

The MC5-A Calmare® therapy device is designed to generate a patient-specific cutaneous electrostimulation to reduce the abnormal pain intensity. Sixteen patients from one center received one-hour interventions daily over 10 working days.

RESULTS

Of 18 patients, 16 were evaluable. The mean age of the patients was 58.6 years-four men and 14 women-and the duration of CIPN was three months to eight years. The most common drugs were taxanes, platinums, and bortezomib (Velcade, Millenium Pharmaceuticals, Cambridge MA). At the end of the study (Day 10), a 20% reduction in numeric pain scores was achieved in 15 of 16 patients. The pain score fell 59% from 5.81±1.11 before treatment to 2.38±1.82 at the end of 10 days (P<0.0001 by paired t-test). A daily treatment benefit was seen with a strong statistically significant difference between the pre- and post-daily pain scores (P<0.001). Four patients had their CIPN reduced to zero. A repeated-measures analysis using the scores from all 10 days confirmed these results. No toxicity was seen. Some responses have been durable without maintenance.

CONCLUSION

Patient-specific cutaneous electrostimulation with the MC5-A Calmare® device appears to dramatically reduce pain in refractory CIPN patients with no toxicity. Further studies are underway to define the benefit, mechanisms of action, and optimal schedule.