Spinal Cord Stimulation (SCS) in Conjunction With Peripheral Nerve Field Stimulation (PNfS) for the Treatment of Complex Pain in Failed Back Surgery Syndrome (FBSS)

Meta-analysis and review of rechargeable implantable pulse generators for spinal cord stimulation and deep brain stimulation

Introduction

Neuromodulation through deep brain stimulation (DBS) and spinal cord stimulation (SCS) has become a successful therapy for various neurological disorders, such as movement disorders and chronic pain. Implantable pulse generators (IPGs) are pivotal in these therapies, available as either rechargeable (r-IPGs) or non-rechargeable (nr-IPGs).

Research question

To perform a meta-analysis on r-IPGs.

Methods

A systematic literature search following PRISMA guidelines was conducted on PubMed, focusing on studies published from January 2005 to August 2023. Included studies comprised clinical trials, randomized controlled trials, and comparative studies involving human subjects. Data extraction focused on patient demographics, stimulation types, battery characteristics, and complications. Descriptive statistics and Pearson correlation analyses were performed using SPSS software.

Results

Nine studies involving 288 patients with rechargeable IPGs (r-IPGs) for SCS and 257 patients with r-IPGs for DBS met the inclusion criteria. r-IPGs exhibited low rates of surgical revisions and infections, with surgical revision rates of 8.87% for SCS and 5.45% for DBS, and infection rates of 2.6% for SCS and 1.56% for DBS. Charge burden was comparable with 97.34 min and 93.41 min per week for SCS and DBS respectively. Correlation analyses indicated that longer battery recharge times were associated with an increased incidence of complications, including unintentional interruptions and hardware failures.

Discussion

r-IPGs may offer substantial benefits in reducing re-operation rates and complications associated. Nonetheless, careful management of battery charging is crucial to maximize these benefits. Establishing international guidelines for the use of r-IPGs in specific patient populations and conditions is recommended to standardize and optimize outcomes.

Peripheral Nerve Stimulation for Low Back Pain: A Systematic Review

PURPOSE OF REVIEW

Low back pain (LBP) is a prevalent condition that is associated with diminished physical function, poor mental health outcomes, and reduced quality of life. Peripheral nerve stimulation (PNS) is an emerging modality that has been utilized to treat LBP. The primary objective of this systematic review is to appraise the level of evidence on the efficacy of PNS for treatment of LBP.

RECENT FINDINGS

Twenty-nine articles were included in this systematic review, consisting of 828 total participants utilizing PNS as the primary modality for LBP and 173 participants using PNS as salvage or adjunctive therapy for LBP after SCS placement. Different modalities of PNS therapy were reported across studies, including conventional PNS systems stimulating the lumbar medial branch nerves, peripheral nerve field stimulation (PNFS), and restorative neuromuscular stimulation of the multifidus muscles. All studies consistently reported positive modest to moderate improvement in pain intensity with PNS therapy when comparing baseline pain intensity to each study's respective primary follow-up period. There was a very low GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) quality of evidence supporting this finding. Inconsistency was present in some comparative studies that demonstrated no difference between PNS therapy versus control cohorts (sham or SCS therapy alone), which therefore highlighted the potential for placebo effect. This systematic review highlights that PNS, PNFS, and neuromuscular stimulation may provide modest to moderate pain relief in patients with LBP, although evidence is currently limited due to risk of bias, clinical and methodological heterogeneity, and inconsistency in data.

A novel framework for the removal of pacing artifacts from bio-electrical recordings

BACKGROUND

Electroceuticals provide clinical solutions for a range of disorders including Parkinson's disease, cardiac arrythmias and are emerging as a potential treatment option for gastrointestinal disorders. However, pre-clinical investigations are challenged by the large stimulation artifacts registered in bio-electrical recordings.

METHOD

A generalized framework capable of isolating and suppressing stimulation artifacts with minimal intervention was developed. Stimulation artifacts with different pulse-parameters in synthetic and experimental cardiac and gastrointestinal signals were detected using a Hampel filter and reconstructed using 3 methods: i) autoregression, ii) weighted mean, and iii) linear interpolation.

RESULTS

Synthetic stimulation artifacts with amplitudes of 2 mV and 4 mV and pulse-widths of 50 ms, 100 ms, and 200 ms were successfully isolated and the artifact window size remained uninfluenced by the pulse-amplitude, but was influenced by pulse-width (e.g., the autoregression method resulted in an identical Root Mean Square Error (RMSE) of 1.64 mV for artifacts with 200 ms pulse-width and both 2 mV and 4 mV amplitudes). The performance of autoregression (RMSE = 1.45 ± 0.16 mV) and linear interpolation (RMSE = 1.22 ± 0.14 mV) methods were comparable and better than weighted mean (RMSE = 5.54 ± 0.56 mV) for synthetic data. However, for experimental recordings, artifact removal by autoregression was superior to both linear interpolation and weighted mean approaches in gastric, small intestinal and cardiac recordings.

CONCLUSIONS

A novel signal processing framework enabled efficient analysis of bio-electrical recordings with stimulation artifacts. This will allow the bio-electrical events induced by stimulation protocols to be efficiently and systematically evaluated, resulting in improved stimulation therapies.

High-frequency electrical stimulation attenuates neuronal release of inflammatory mediators and ameliorates neuropathic pain

BACKGROUND

Neuroinflammation is an important driver of acute and chronic pain states. Therefore, targeting molecular mediators of neuroinflammation may present an opportunity for developing novel pain therapies. In preclinical models of neuroinflammatory pain, calcitonin gene-related peptide (CGRP), substance P and high mobility group box 1 protein (HMGB1) are molecules synthesized and released by sensory neurons which activate inflammation and pain. High-frequency electrical nerve stimulation (HFES) has achieved clinical success as an analgesic modality, but the underlying mechanism is unknown. Here, we reasoned that HFES inhibits neuroinflammatory mediator release by sensory neurons to reduce pain.

METHODS

Utilizing in vitro and in vivo assays, we assessed the modulating effects of HFES on neuroinflammatory mediator release by activated sensory neurons. Dorsal root ganglia (DRG) neurons harvested from wildtype or transgenic mice expressing channelrhodopsin-2 (ChR2) were cultured on micro-electrode arrays, and effect of HFES on optogenetic- or capsaicin-induced neuroinflammatory mediator release was determined. Additionally, the effects of HFES on local neuroinflammatory mediator release and hyperalgesia was assessed in vivo using optogenetic paw stimulation and the neuropathic pain model of chronic constriction injury (CCI) of the sciatic nerve.

RESULTS

Light- or capsaicin-evoked neuroinflammatory mediator release from cultured transgenic DRG sensory neurons was significantly reduced by concurrent HFES (10 kHz). In agreement with these findings, elevated levels of neuroinflammatory mediators were detected in the affected paw following optogenetic stimulation or CCI and were significantly attenuated using HFES (20.6 kHz for 10 min) delivered once daily for 3 days.

CONCLUSION

These studies reveal a previously unidentified mechanism for the pain-modulating effect of HFES in the setting of acute and chronic nerve injury. The results support the mechanistic insight that HFES may reset sensory neurons into a less pro-inflammatory state via inhibiting the release of neuroinflammatory mediators resulting in reduced inflammation and pain.

Efficacy of Peripheral Nerve Field Stimulation for the Management of Chronic Low Back Pain and Persistent Spinal Pain Syndrome: A Narrative Review

OBJECTIVES

Various approaches have been developed with a view to treating the back pain component in patients with chronic low back pain (CLBP) and persistent spinal pain syndrome (PSPS). Emerging evidence shows that peripheral nerve field stimulation (PNFS) may be an efficacious therapeutic modality against axial low back pain. Hence, the aim of the review was to evaluate the analgesic efficacy and safety of PNFS, when used alone or as an adjunct to spinal cord stimulation (SCS), for managing CLBP and PSPS.

MATERIALS AND METHODS

A comprehensive search for clinical studies on PNFS and PNFS + SCS used for the management of CLBP and/or PSPS was performed using PubMed, EMBASE, MEDLINE via Proquest, and Web of Science.

RESULTS

A total of 15 studies were included, of which four were randomized controlled trials (RCTs), nine were observational studies, and two were case series. For patients receiving PNFS, a significant decrease in back pain intensity and analgesic consumption, together with a significant improvement in physical functioning, was observed upon implant of the permanent system. Meanwhile, the addition of PNFS to SCS in refractory cases was associated with a significant reduction in back and leg pain, respectively.

CONCLUSIONS

This review suggests that PNFS, when used alone or in combination with SCS, appears to be effective in managing back pain. However, high-quality evidence that supports the long-term analgesic efficacy and safety is still lacking. Hence, RCTs with a larger patient population and of a longer follow-up duration are warranted.

Effects of Ultrasound-Guided Nerve Stimulation Targeting Peripheral Nerve Tissue on Pain and Function: A Scoping Review

This paper assesses the effects of percutaneous electrical nerve stimulation (PENS) on pain- and function-related outcomes by means of a scoping review of studies with single cases, case-series, quasi-experimental, and randomized or non-randomized trial designs. We consulted the PubMed, MEDLINE and EMBASE databases. Data were extracted by two reviewers. The methodological quality of studies was assessed using the Physiotherapy Evidence Database (PEDro) scale for experimental studies and the Joanna Briggs Institute (JBI) tool for case reports or cases series. Mapping of the results included: (1), description of included studies; (2), summary of results; and, (3), identification of gaps in the existing literature. Eighteen articles (five randomized controlled trials, one trial protocol, nine case series and three case reports) were included. The methodological quality of the papers was moderate to high. The conditions included in the studies were heterogeneous: chronic low back pain, lower limb pain after lumbar surgery, chronic post-amputation pain, rotator cuff repair, foot surgery, knee arthroplasty, knee pain, brachial plexus injury, elbow pain and ankle instability. In addition, one study included a healthy athletic population. Interventions were also highly heterogeneous in terms of sessions, electrical current parameters, or time of treatment. Most studies observed positive effects of PENS targeting nerve tissue against the control group; however, due to the heterogeneity in the populations, interventions, and follow-up periods, pooling analyses were not possible. Based on the available literature, PENS interventions targeting peripheral nerves might be considered as a potential therapeutic strategy for improving pain-related and functional outcomes. Nevertheless, further research considering important methodological quality issues (e.g., inclusion of control groups, larger sample sizes and comparatives between electric current parameters) are needed prior to recommending its use in clinical practice.

The Predictive Value of Transcutaneous Electrical Nerve Stimulation for Patient Selection in Peripheral Nerve Field Stimulation for Chronic Low Back Pain: A Prospective Study

OBJECTIVE

Peripheral nerve field stimulation (PNFS) is an effective alternative treatment for patients with chronic low back pain. Transcutaneous electrical nerve stimulation (TENS) is frequently used in pain therapy. Aim of this prospective study was to examine the predictive value of TENS for later PNFS treatment.

MATERIALS AND METHODS

Between 2014 and 2019, a prospective cohort study of 41 patients with chronic lumbar pain was conducted. Pain intensity (NRS) was assessed before and after TENS use, preoperatively/postoperatively and in the follow-up after three and six months, SF12v2 questionnaires with physical (PCS) and mental component summary (MCS) scores, and Oswestry disability index (ODI) questionnaire at baseline as well as three and six months after PNFS implantation. Implantation of the PNFS-system with two percutaneous leads was performed after four to seven days of positive testing. Statistical analysis was performed using depending t-test, ANOVA, and Spearman correlation.

RESULTS

The cohort consisted of 41 patients (19 females, 22 males) with a median age of 60.5 years (IQR^25-75 52-67). Two patients were lost to follow-up. After positive PNFS testing a pulse generator (IPG) was implanted in 15 patients with positive TENS effect and 15 patients without TENS effect. Leads were explanted in nine patients after negative PNFS trial phase. TENS positive patients showed significant correlation to a positive effect in the PNFS trial phase in NRS reduction (p = 0.042) indicating that TENS responders will also respond to PNFS (94% patients). After three and six months follow-up median NRS and SF12v2 (PCS) improved significantly in both cohorts, SF12v2 (MCS) and ODI only in the TENS positive cohort, respectively.

CONCLUSION

TENS can be predictive for patient selection in PNFS, as TENS positive patients showed significant correlation with a positive PNFS trial period. Therefore, TENS positive patients might be justifiable to be directly implanted with leads and IPG. TENS positive patients further tend to show a better improvement in the follow-up.

Peripheral subcutaneous field stimulation for the treatment of spinal cord injury at-level pain: case report, literature review, and 5-year follow-up

Spinal cord injury (SCI) frequently engenders chronic pain which may be classified as occurring above, at, or below the level of injury. Since patients with SCI may have a complex combination of nociceptive and neuropathic pain, pharmacological interventions often fail. Peripheral subcutaneous field stimulation (PSFS) is a novel neuromodulation surgery for pain in which subcutaneous electrodes designed for spinal cord stimulation are placed subcutaneously in a region of pain. We report the case of a 26-year-old man who was an unrestrained driver in a motor vehicle accident and suffered a complete ASIA A spinal cord injury with paraplegia due to a T4 three-column burst fracture. He underwent successful surgical fixation of the fracture (7/27/12) and developed severe at-level SCI-associated pain which failed all conservative measures. After a successful trial, two octrode leads (Abbott Medical, Plano, TX, USA) were placed for PSFS under general anesthesia and were connected to a right flank rechargeable pulse generator (11/6/13). At 60 months postoperative, the patient continues to use the peripheral field stimulation system on a daily basis and reports near complete relief of his at-level spinal cord injury pain. He noted instantaneous relief of his pain once ideal stimulation programming was achieved and has tolerated complete cessation of all narcotic use. His current programming settings are: Frequency of 50 Hz (Hz), Pulse Width of 350 μs (μsec), Amplitude of 0.00 miliamps (mA), Comf of 7.70 mA, and Perc of 4.50 mA. Chronic pain is a challenging and expensive sequela to manage in SCI patients and newer therapies are needed. Our case suggests that SCI at-level pain may respond durably to PSFS and provides the longest published follow-up on a case of PSFS. Peripheral subcutaneous field stimulation remains an investigational treatment for chronic pain syndrome and larger, long-term follow up studies are needed for the FDA and payers to approve this modality.

Crossover effects of ultrasound-guided percutaneous neuromodulation on contralateral hamstring flexibility

Background

Crossover effects refer to the responses of a non-exercised contralateral limb. There is evidence of this effect, as it relates to muscle fatigue, strength, and stretch, but not as it relates to neuromodulation.

Objectives

To compare the crossover effects of percutaneous neuromodulation (PNM) on hip range of motion (ROM), observed in a straight leg raise (SLR) test, in asymptomatic participants with bilateral reduced hamstring flexibility, versus the neurodynamic sciatic sliding technique, hamstring stretching and mechanical stimulation of the sciatic nerve using a needle (without electrical stimulation). To evaluate the tensiomyographic changes between the two lower limbs after these interventions.

Methods

80 participants with bilateral reduced hamstring flexibility were randomized into four groups: Stretching, Neurodynamic, PNM, and Needle groups. All interventions were performed on the right limb. Each participant’s leg was subjected to SLR testing and tensiomyography before and after the interventions.

Results

Each group improved their SLR values in the non-intervention limb compared to baseline values, but the PNM and Needle groups obtained higher values for the SLR test in the non-intervention limb compared with the Neurodynamic and Stretching groups. There were statistically significant differences for mean SLR measures between limbs pre- and post-intervention for all groups except the PNM group, suggesting crossover effects for PNM but not the other techniques studied. There were no differences in tensiomyographic assessments between groups or between sides, at baseline or upon completion of the study.

Conclusion

PNM produced benefits in the SLR test in the non-intervention limb and only 1.5 min was enough to obtain this effect. In addition, no technique interfered with muscle activation.

Cost-Effectiveness Analysis of Peripheral Nerve Field Stimulation as Add-On Therapy to Spinal Cord Stimulation in the Treatment of Chronic Low Back Pain in Failed Back Surgery Syndrome Patients

OBJECTIVE

Presently, there is only limited evidence about the cost-effectiveness of peripheral nerve field stimulation (PNFS) and no evidence to date on the cost-effectiveness of PNFS as an add-on therapy to spinal cord stimulation (SCS). In a multicenter randomized controlled trial, PNFS as add-on therapy to SCS demonstrated clinical effectiveness in treating chronic low back pain in failed back surgery syndrome (FBSS) patients. We report here the cost-effectiveness of PNFS as additional therapy.

MATERIALS AND METHODS

Cost-effectiveness analysis was performed from a health-care perspective using the general principles of cost-utility analysis, using empirical data from our multicenter randomized controlled trial on the effectiveness of hybrid SCS + PNFS on low back pain in FBSS patients, who were back pain non-responders to initial SCS-therapy, over a time-horizon of three months. Outcome measures were costs and quality-adjusted life-years (QALYs). Cost and QALYs were integrated using the net monetary benefit (NMB). Differences in costs, effects, and NMB were analyzed using multilevel regression. Uncertainty surrounding the NMB was presented by cost-effectiveness acceptability curves.

RESULTS

A total of 52 patients implanted with both SCS and PNFS, randomly assigned to a group with PNFS either activated or inactive, completed the controlled part of the study. With mean total costs for the SCS + active PNFS group of €1813.86 (SD €109.78) versus €1103.64 (SD €123.43) for the SCS + inactive PNFS group at three months, we found an incremental cost-utility ratio of €25.311 per QALY gained and a probability being cost-effective of more than 80% given a willingness to pay for a QALY of about €40.000.

CONCLUSIONS

From a Dutch national health-care context, when the willingness to pay threshold is up to 60.000 Euros per QALY, PNFS as an add-on therapy to SCS for the treatment of low back pain in FBSS patients has a high probability of being cost-effective.

Immediate effects of ultrasound-guided percutaneous neuromodulation versus physical exercise on performance of the flexor hallucis longus muscle in professional dancers: a randomised clinical trial

Background:

Ultrasound-guided percutaneous neuromodulation (US-guided PNM) is a minimally invasive intervention. This technique consists of the application of percutaneous electrical stimulation (PES) through an acupuncture needle-like electrode that is placed in close proximity to the nerve or motor point of the target muscle under ultrasound guidance.

Objective:

To examine the immediate effects of a stretching exercise, an eccentric exercise and US-guided PNM on the performance of the flexor hallucis longus (FHL) muscle in young dancers.

Methods:

Randomised clinical trial. A total of 45 dancers were divided into three groups: Stretching group, Eccentric group and PNM group. The following performance parameters were assessed: range of motion (ROM) of the first metatarsophalangeal joint, balance test and unilateral heel raise fatigue test.

Results:

There were no differences between these groups in baseline measurements; at the end of the study, mean balance and endurance values were only significantly higher for the PNM group compared to the Stretching (p = 0.007 and p < 0.001, respectively) and Eccentric groups (p = 0.003 and p < 0.001, respectively). The effect sizes were large for the balance (d = 0.8) and endurance (d = 1.83) tests in the PNM group. Both the Stretching and Eccentric groups exhibited improvements in ROM compared to their baseline values (p = 0.009 and p = 0.004, respectively), whereas there was no significant temporal improvement noted for the PNM group. The effect sizes with respect to ROM values were moderate for stretching (d = 0.6) and eccentric (d = 0.7) exercises.

Conclusion:

An isolated PES intervention provides a greater immediate increase in balance and muscular strength than an active stretching and eccentric exercise of the FHL muscle in young ballet dancers.

Spinal Cord Stimulation

Spinal cord stimulation (SCS) has been well established as a safe and effective treatment of pain derived from a wide variety of etiologies. Careful patient selection including a rigorous trial period and psychological evaluation are essential. When patients proceed to permanent implantation, various considerations should be made, such as the type of lead, type of anesthesia, and waveform patterns for SCS. This article discusses the common indications for SCS, patient selection criteria, and pertinent outcomes from randomized clinical trials related to common indications treated with SCS. Technical considerations, such as type of implant, anesthesia, and programming, are also discussed.

Duloxetine Improves Spinal Cord Stimulation Outcomes for Chronic Pain

OBJECTIVE

Spinal cord stimulation (SCS) has been shown to be effective in treating chronic pain in patients with varying etiologies. However, the impact of pharmacological treatment on augmenting response to SCS has not been previously studied.

METHODS

We enrolled 108 patients who had undergone SCS surgery and documented their pain preoperatively and at 12 months postoperatively using the Numeric Rating Scale (NRS), McGill Pain Questionnaire (MPQ), Beck Depression Inventory (BDI), Oswestry Disability Index (ODI), Pain Catastrophizing Scale (PCS), and Global Impression of Change (GIC). Pain outcomes were compared between patients receiving SCS alone and in addition to duloxetine.

RESULTS

At 1-year follow-up, patients receiving duloxetine and SCS (n = 41) had better pain relief in the affective component of MPQ (p < 0.05) than those receiving SCS alone (n = 71). Patients on duloxetine with SCS also were significantly more willing to receive SCS again (p < 0.01). This willingness appeared to be duloxetine dose dependent (p < 0.05). Patients receiving pregabalin or gabapentin with SCS did not have significantly more pain relief than patients receiving SCS alone.

CONCLUSION

This study shows the combination therapy to be an effective strategy to provide more holistic pain relief and further improve the quality of life of SCS patients.

Bilateral Peripheral Nerve Field Stimulation for Intractable Coccygeal Pain: A Case Study Using Dual Lead Intercommunication

Coccygeal pain is a difficult chronic pain problem with mixed response to various treatments. This is a report of a case of coccygeal pain that after failing various conservative and interventional procedures over five years was evaluated with a temporary peripheral sacral fascial lead followed by implantation of bilateral sacral paramedian leads for peripheral nerve field stimulation (PNFS). This resulted in marked pain control and resumption of full activity. The visual analog scale (VAS) pain score improved from eight pre-implant to one after implant and has remained at that level in follow-up. Peripheral nerve field stimulation has been reported for axial chronic back pain, post-laminectomy pain and sacroiliac joint pain either alone or in conjunction with epidural spinal cord stimulation. Both single and parallel leads have been used to provide wider stimulation but differences in location have not been examined. This is the first case report of the use of PNFS for treatment of intractable chronic coccygeal pain. The effectiveness of PNFS was established for this patient by using a prolonged 10-day temporary trial period followed by a 30-day interval without stimulation during which the pain returned to the pre-trial level before proceeding with permanent implantation, it was clear that in this case, PNFS was effective for pain control. Interestingly, the trial and permanent leads were both in the posterior sacral fascia but not in identical positions yet equally effective for pain control. The observation of the effectiveness of different positions may indicate that at least for peripheral field stimulation there may be significant current spread in the fascia. Two and three months after the implant, we examined the effect of different lead settings and the effect of unilateral stimulation compared with bilateral stimulation with and without interlead communication. The patient feedback in this case provides some understanding of the effect of field stimulation with different lead placements. A trial of a deep peripheral fascial lead for sacral and coccygeal field stimulation is a simple option and may be a reasonable approach to consider in the range of treatments for chronic coccygeal pain.

The Results of Treating Failed Back Surgery Syndrome by Adhesiolysis: Comparing the One- and Three-Day Protocols

Background

The optimal treatment of failed back surgery syndrome (FBSS) is controversial. Limited studies have demonstrated the satisfactory outcomes of percutaneous adhesiolysis in FBSS, which can be performed as a 1 day or 3 days procedure. In the current randomized clinical trial, we compared the clinical and functional outcomes of these 2 techniques.

Methods

In this study, 60 patients with FBSS were randomly assigned into 2 equal groups: 1 day group and 3 days group. Before and at 4 and 12 weeks after the procedure, pain intensity was measured using visual analogue scale (VAS). The Oswestry disability index (ODI) was also completed. Pain reduction of 50% or more was defined as treatment success.

Results

Significant pain relief and ODI improvement were obtained in the 2 groups with adhesiolysis (P < 0.001). However, pain intensity remained the same before and at 4 and 12 weeks after adhesiolysis. ODI score was significantly lower in 1 day group in the 1 month visit (P < 0.001). Treatment was successful in 76.7% and 83.3% of the patients in 1 day and 3 days groups, respectively (P = 0.519).

Conclusions

Adhesiolysis is an effective treatment for pain relief and functional improvement in FBSS. The results of 1 day and 3 days procedures are comparable. Based on these findings, the authors recommend using 1 day technique, which can potentially decrease the patients' discomfort, hospital stay, and cost of treatment.

Spinal Cord Stimulation in Failed Back Surgery Syndrome: Review of Clinical Use, Quality of Life and Cost-Effectiveness

Failed back surgery syndrome (FBSS) is complex and recurrent chronic pain after spinal surgery. Several important patient and surgery related risk factors play roles in development of FBSS. Inadequate selection of the candidates for the spinal surgeries is one of the most crucial causes. The guidelines suggest that conservative management featuring pharmacologic approaches and rehabilitation should be introduced first. For therapy-refractory FBSS, spinal cord stimulation (SCS) is recommended in selected patients. Treatment efficacy for FBSS has increased over the years with the majority of patients experiencing pain relief and reduced medicinal load. Improved quality of life can also be achieved using SCS. Cost-effectiveness of SCS still remains unclear. However evidence for SCS role in FBSS is controversial, SCS can be beneficial for carefully classified patients.

[SCS as a treatment option for failed back surgery syndrome]

Unfortunately, 10-40 % of patients still experience pain after spinal surgery. There are many reasons for the patients' complaints. If no identifiable cause, such as a recurrent disc herniation, is visible, this is referred to as failed back surgery syndrome. However, this definition includes a variety of possible underlying causes of the pain, which result in just as many different therapeutic approaches. In addition to pharmacological, behavioral and physical therapy, also neuromodulation techniques can be offered; the best known method is spinal cord stimulation (SCS). The following article describes evidence-based studies with regard to the beneficial treatment of failed back surgery syndrome with conventional tonic SCS and new developments in spinal cord stimulation addressing the treatment of chronic refractory back pain.

Muscle Activation During Peripheral Nerve Field Stimulation Occurs Due to Recruitment of Efferent Nerve Fibers, Not Direct Muscle Activation

BACKGROUND

Peripheral nerve field stimulation (PNFS) is a potential treatment for chronic low-back pain. Pain relief using PNFS is dependent on activation of non-nociceptive Aβ-fibers. However, PNFS may also activate muscles, causing twitches and discomfort. In this study, we developed a mathematical model, to investigate the activation of sensory and motor nerves, as well as direct muscle fiber activation.

METHODS

The extracellular field was estimated using a finite element model based on the geometry of CT scanned lumbar vertebrae. The electrode was modeled as being implanted to a depth of 10-15 mm. Three implant directions were modeled; horizontally, vertically, and diagonally. Both single electrode and "between-lead" stimulation between contralateral electrodes were modeled. The extracellular field was combined with models of sensory Aβ-nerves, motor neurons and muscle fibers to estimate their activation thresholds.

RESULTS

The model showed that sensory Aβ fibers could be activated with thresholds down to 0.563 V, and the lowest threshold for motor nerve activation was 7.19 V using between-lead stimulation with the cathode located closest to the nerves. All thresholds for direct muscle activation were above 500 V.

CONCLUSIONS

The results suggest that direct muscle activation does not occur during PNFS, and concomitant motor and sensory nerve fiber activation are only likely to occur when using between-lead configuration. Thus, it may be relevant to investigate the location of the innervation zone of the low-back muscles prior to electrode implantation to avoid muscle activation.

Interventional Therapies for Chronic Low Back Pain: A Focused Review (Efficacy and Outcomes)

CONTEXT

Lower back pain is considered to be one of the most common complaints that brings a patient to a pain specialist. Several modalities in interventional pain management are known to be helpful to a patient with chronic low back pain. Proper diagnosis is required for appropriate intervention to provide optimal benefits. From simple trigger point injections for muscular pain to a highly complex intervention such as a spinal cord stimulator are very effective if chosen properly. The aim of this article is to provide the reader with a comprehensive reading for treatment of lower back pain using interventional modalities.

EVIDENCE ACQUISITION

Extensive search for published literature was carried out online using PubMed, Cochrane database and Embase for the material used in this manuscript. This article describes the most common modalities available to an interventional pain physician along with the most relevant current and past references for the treatment of lower back pain. All the graphics and images were prepared by and belong to the author.

RESULTS

This review article describes the most common modalities available to an interventional pain physician along with the most relevant current and past references for the treatment of lower back pain. All the graphics and images belong to the author. Although it is beyond the scope of this review article to include a very detailed description of each procedure along with complete references, a sincere attempt has been made to comprehensively cover this very complex and perplexing topic.

CONCLUSION

Lower back pain is a major healthcare issue and this review article will help educate the pain practitioners about the current evidence based treatment options.

The appropriate use of neurostimulation of the spinal cord and peripheral nervous system for the treatment of chronic pain and ischemic diseases: the Neuromodulation Appropriateness Consensus Committee

INTRODUCTION

The Neuromodulation Appropriateness Consensus Committee (NACC) of the International Neuromodulation Society (INS) evaluated evidence regarding the safety and efficacy of neurostimulation to treat chronic pain, chronic critical limb ischemia, and refractory angina and recommended appropriate clinical applications.

METHODS

The NACC used literature reviews, expert opinion, clinical experience, and individual research. Authors consulted the Practice Parameters for the Use of Spinal Cord Stimulation in the Treatment of Neuropathic Pain (2006), systematic reviews (1984 to 2013), and prospective and randomized controlled trials (2005 to 2013) identified through PubMed, EMBASE, and Google Scholar.

RESULTS

Neurostimulation is relatively safe because of its minimally invasive and reversible characteristics. Comparison with medical management is difficult, as patients considered for neurostimulation have failed conservative management. Unlike alternative therapies, neurostimulation is not associated with medication-related side effects and has enduring effect. Device-related complications are not uncommon; however, the incidence is becoming less frequent as technology progresses and surgical skills improve. Randomized controlled studies support the efficacy of spinal cord stimulation in treating failed back surgery syndrome and complex regional pain syndrome. Similar studies of neurostimulation for peripheral neuropathic pain, postamputation pain, postherpetic neuralgia, and other causes of nerve injury are needed. International guidelines recommend spinal cord stimulation to treat refractory angina; other indications, such as congestive heart failure, are being investigated.

CONCLUSIONS

Appropriate neurostimulation is safe and effective in some chronic pain conditions. Technological refinements and clinical evidence will continue to expand its use. The NACC seeks to facilitate the efficacy and safety of neurostimulation.

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.

Anterograde and retrograde epidural paddle placement through a single laminotomy for the treatment of back and lower extremity pain using spinal cord stimulation: case reports and technical note

OBJECTIVE

Spinal cord stimulation can be effectively used in the treatment of low back pain and extremity pain in failed back surgery syndrome. Ideal targets for stimulation corresponding to paresthesia overlap in the low back versus the extremities may differ in cranial-caudal location.

MATERIALS AND METHODS

We present here a technical report of three cases demonstrating a technique to place anterograde and retrograde epidural paddles through a single laminotomy.

RESULTS

Using this technique we were able to cover five spinal levels in each patient, and different stimulation programs at different levels created paresthesia overlap in back versus lower extremity in those patients.

CONCLUSION

Dual paddle placement through a single laminotomy may be a reasonable option for select patients where coverage of anatomically-separated pain regions is necessary. This technique can be performed in most patients without significantly increased morbidity.

Spinal cord stimulation for neuropathic pain: current perspectives

Neuropathic pain constitutes a significant portion of chronic pain. Patients with neuropathic pain are usually more heavily burdened than patients with nociceptive pain. They suffer more often from insomnia, anxiety, and depression. Moreover, analgesic medication often has an insufficient effect on neuropathic pain. Spinal cord stimulation constitutes a therapy alternative that, to date, remains underused. In the last 10 to 15 years, it has undergone constant technical advancement. This review gives an overview of the present practice of spinal cord stimulation for chronic neuropathic pain and current developments such as high-frequency stimulation and peripheral nerve field stimulation.