Spinal cord stimulation: indications and outcomes

Clinical neurophysiology in the treatment of movement disorders: IFCN handbook chapter

In this review, different aspects of the use of clinical neurophysiology techniques for the treatment of movement disorders are addressed. First of all, these techniques can be used to guide neuromodulation techniques or to perform therapeutic neuromodulation as such. Neuromodulation includes invasive techniques based on the surgical implantation of electrodes and a pulse generator, such as deep brain stimulation (DBS) or spinal cord stimulation (SCS) on the one hand, and non-invasive techniques aimed at modulating or even lesioning neural structures by transcranial application. Movement disorders are one of the main areas of indication for the various neuromodulation techniques. This review focuses on the following techniques: DBS, repetitive transcranial magnetic stimulation (rTMS), low-intensity transcranial electrical stimulation, including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), and focused ultrasound (FUS), including high-intensity magnetic resonance-guided FUS (MRgFUS), and pulsed mode low-intensity transcranial FUS stimulation (TUS). The main clinical conditions in which neuromodulation has proven its efficacy are Parkinson's disease, dystonia, and essential tremor, mainly using DBS or MRgFUS. There is also some evidence for Tourette syndrome (DBS), Huntington's disease (DBS), cerebellar ataxia (tDCS), and axial signs (SCS) and depression (rTMS) in PD. The development of non-invasive transcranial neuromodulation techniques is limited by the short-term clinical impact of these techniques, especially rTMS, in the context of very chronic diseases. However, at-home use (tDCS) or current advances in the design of closed-loop stimulation (tACS) may open new perspectives for the application of these techniques in patients, favored by their easier use and lower rate of adverse effects compared to invasive or lesioning methods. Finally, this review summarizes the evidence for keeping the use of electromyography to optimize the identification of muscles to be treated with botulinum toxin injection, which is indicated and widely performed for the treatment of various movement disorders.

The Evolution of Surgical Technique in Spinal Cord Stimulation: A Scoping Review

Since the advent of spinal cord stimulation (SCS), its operative technique has consistently advanced. We performed a scoping review of the literature regarding SCS operative techniques to highlight key advancements. To review, summarize, and highlight key changes in SCS implantation techniques since their inception. The authors performed a MEDLINE search inclusive of articles from 1967 to June 2023 including human and modeling studies written in English examining the role of trialing, intraoperative neuromonitoring, and surgical adaptations. Using the Rayyan platform, two reviewers performed a blinded title screen. Of the 960 articles, 197 were included in the title screen, 107 were included in the abstract review, and ultimately 69 articles met inclusion criteria. We examined the utility of trialing and found that historical controls showed significant efficacy, whereas recent results are more equivocal. We discuss the significant improvement in outcomes with intraoperative neuromonitoring for asleep SCS placement. We highlight technique improvements that led to significant reductions in infection, lead migration, and inadequate pain relief. Physicians implanting SCS systems for chronic pain management must continually refine their surgical techniques to keep up with this rapidly evolving therapy. In addition, through collaborative efforts of neuromodulators and industry, SCS is safer and more effective for patients suffering from chronic pain.

Healthcare Utilization (HCU) Reduction with High-Frequency (10 kHz) Spinal Cord Stimulation (SCS) Therapy

Spinal cord stimulation (SCS) is a well-established treatment for patients with chronic pain. With increasing healthcare costs, it is important to determine the benefits of SCS in healthcare utilization (HCU). This retrospective, single-center observational study involved 160 subjects who underwent implantation of a high-frequency (10 kHz) SCS device. We focused on assessing trends in HCU by measuring opioid consumption in morphine milligram equivalents (MME), as well as monitoring emergency department (ED) and office visits for interventional pain procedures during the 12-month period preceding and following the SCS implant. Our results revealed a statistically significant reduction in HCU in all domains assessed. The mean MME was 51.05 and 26.52 pre- and post-implant, respectively. There was a 24.53 MME overall decrease and a mean of 78.2% statistically significant dose reduction (p < 0.0001). Of these, 91.5% reached a minimally clinically important difference (MCID) in opioid reduction. Similarly, we found a statistically significant (p < 0.01) decrease in ED visits, with a mean of 0.12 pre- and 0.03 post-implant, and a decrease in office visits for interventional pain procedures from a 1.39 pre- to 0.28 post-10 kHz SCS implant, representing a 1.11 statistically significant (p < 0.0001) mean reduction. Our study reports the largest cohort of real-world data published to date analyzing HCU trends with 10 kHz SCS for multiple pain etiologies. Furthermore, this is the first and only study evaluating HCU trends with 10 kHz SCS by assessing opioid use, ED visits, and outpatient visits for interventional pain procedures collectively. Preceding studies have individually investigated these outcomes, consistently yielding positive results comparable to our findings.

Wireless Battery-free and Fully Implantable Organ Interfaces

Advances in soft materials, miniaturized electronics, sensors, stimulators, radios, and battery-free power supplies are resulting in a new generation of fully implantable organ interfaces that leverage volumetric reduction and soft mechanics by eliminating electrochemical power storage. This device class offers the ability to provide high-fidelity readouts of physiological processes, enables stimulation, and allows control over organs to realize new therapeutic and diagnostic paradigms. Driven by seamless integration with connected infrastructure, these devices enable personalized digital medicine. Key to advances are carefully designed material, electrophysical, electrochemical, and electromagnetic systems that form implantables with mechanical properties closely matched to the target organ to deliver functionality that supports high-fidelity sensors and stimulators. The elimination of electrochemical power supplies enables control over device operation, anywhere from acute, to lifetimes matching the target subject with physical dimensions that supports imperceptible operation. This review provides a comprehensive overview of the basic building blocks of battery-free organ interfaces and related topics such as implantation, delivery, sterilization, and user acceptance. State of the art examples categorized by organ system and an outlook of interconnection and advanced strategies for computation leveraging the consistent power influx to elevate functionality of this device class over current battery-powered strategies is highlighted.

Fully implanted battery-free high power platform for chronic spinal and muscular functional electrical stimulation

Electrical stimulation of the neuromuscular system holds promise for both scientific and therapeutic biomedical applications. Supplying and maintaining the power necessary to drive stimulation chronically is a fundamental challenge in these applications, especially when high voltages or currents are required. Wireless systems, in which energy is supplied through near field power transfer, could eliminate complications caused by battery packs or external connections, but currently do not provide the harvested power and voltages required for applications such as muscle stimulation. Here, we introduce a passive resonator optimized power transfer design that overcomes these limitations, enabling voltage compliances of ± 20 V and power over 300 mW at device volumes of 0.2 cm2, thereby improving power transfer 500% over previous systems. We show that this improved performance enables multichannel, biphasic, current-controlled operation at clinically relevant voltage and current ranges with digital control and telemetry in freely behaving animals. Preliminary chronic results indicate that implanted devices remain operational over 6 weeks in both intact and spinal cord injured rats and are capable of producing fine control of spinal and muscle stimulation.

Incidence of Neuraxial and Non-Neuraxial Hematoma Complications From Spinal Cord Stimulator Surgery: Systematic Review and Proportional Meta-Analysis

OBJECTIVE

The goal of this meta-analysis was to estimate the incidence of total hematomas, neuraxial hematomas, and non-neuraxial hematomas in patients who underwent temporary spinal cord stimulator (SCS) lead trial placement and permanent implantation of SCS leads and internal pulse generator (IPG).

MATERIALS AND METHODS

A comprehensive search was conducted of databases of any publications before October 21, 2021. Eligible study designs included randomized control trials and prospective or retrospective observational studies with more than ten patients. The primary outcome variables were the incidences of total hematomas, neuraxial hematomas, and non-neuraxial hematomas in patients with SCS. These dichotomous categorical outcomes were abstracted from studies after Freeman-Tukey arcsine square root transformation using random-effects meta-analysis (DerSimonian and Laird method). Pooled incidence rates and 95% CIs were calculated for each outcome variable.

RESULTS

A total of 40 studies met the inclusion criteria. Included in the neuraxial and non-neuraxial hematoma analyses were 4751 patients and 3862 patients, respectively. The pooled incidence of any hematoma in patients with SCS was 0.81% (95% CI, 0.45%-1.27%). The pooled incidence of neuraxial hematoma in patients with SCS was 0.32% (95% CI, 0.18%-0.50%). This included primarily epidural hematomas (11/4751) but also comprised an intracranial hemorrhage in a patient on enoxaparin bridge therapy from warfarin and one patient not on anticoagulation with an intracranial subdural hematoma that resulted in death. The pooled incidence of non-neuraxial hematomas in patients with SCS was 0.59% (95% CI, 0.29%-1.00%).

CONCLUSION

The overall incidence of hematomas in patients with temporary SCS trial lead placement and permanent SCS/IPG implantations is less than 1%. Furthermore, the incidence of neuraxial hematomas is less than 0.5%, which is of particular interest given the potential devastating consequences of this complication. The results of this study can be used to inform patients and implanting physicians on hematoma complications from SCS and highlight that the benefits of SCS outweigh the hematoma risks if anticoagulation is appropriately managed perioperatively.

Machine Learning in Spinal Cord Stimulation for Chronic Pain

Spinal cord stimulation (SCS) is an effective treatment for chronic neuropathic pain. The success of SCS is dependent on candidate selection, response to trialing, and programming optimization. Owing to the subjective nature of these variables, machine learning (ML) offers a powerful tool to augment these processes. Here we explore what work has been done using data analytics and applications of ML in SCS. In addition, we discuss aspects of SCS which have narrowly been influenced by ML and propose the need for further exploration. ML has demonstrated a potential to complement SCS to an extent ranging from assistance with candidate selection to replacing invasive and costly aspects of the surgery. The clinical application of ML in SCS shows promise for improving patient outcomes, reducing costs of treatment, limiting invasiveness, and resulting in a better quality of life for the patient.

Spinal cord stimulation-induced gastroparesis: A case report

BACKGROUND

Spinal cord stimulation (SCS) involves the utilization of an implantable neurostimulation device, stereotypically used in the treatment of patients with chronic neuropathic pain. While these devices have been shown to have significant clinical benefits, there have also been documented potential complications, including the risk of infection, fractured electrodes, electrode migration, and lack of symptom improvement. In addition, there has been minimal documentation on gastrointestinal (GI) side effects after SCS implantation.

CASE DESCRIPTION

A 42-year-old patient with chronic axial and radicular neuropathic pain in her back and left leg status post multiple lumbar surgeries underwent implantation of an open paddle lead in the T8-T9 region. After the procedure, the patient endorsed a 50% decrease in pain at the 6-week follow-up with no further concerns. However, at the 18 months follow-up, the patient endorsed severe constipation when the SCS was turned on, leading to subsequent evaluation by gastroenterology, motility studies, and a thorough bowel regimen. Symptoms persisted, and the patient ultimately opted for the removal of the SCS implant at 21 months after the initial surgery.

CONCLUSION

While the exact mechanism behind the GI side effects endorsed in this patient is unknown, current literature postulates a variety of theories, including a SCS-induced parasympathetic blockade of the GI tract. Further, investigation is needed to determine the exact effects of SCS on the GI tract.

Pruritus and urticaria induced by neurostimulation: A case report and review of literature

BACKGROUND

Spinal cord stimulation (SCS) consists of the implantation of neuromodulatory devices in the spinal cord to treat refractory neuropathic pain. Although SCS technology has been proven of immense clinical benefit, complications remain including refractory pain, infection risk, and electrode migration or displacement. Till date, there are minimal reports of allergic side effects following SCS implantation.

CASE DESCRIPTION

In the first case, a 36-year-old male with chronic axial and radicular neuropathic pain in underwent implantation of an open paddle lead and generator. Within 1-3 h of activating the SCS, he developed diffuse raised erythematous hives. Over time, the SCS had immense clinical benefit for his pain reduction; however, he continued to experience recurrent hives and various other allergic reactions including facial flushing and photosensitivity. Four years later, he ultimately opted to retain the device for its clinical pain benefits. In the second case, a 35-year-old female with acute, intractable bilateral occipital neuralgia and a past medical history of Type 1 Chiari Malformation status-post-posterior fossa decompression underwent implantation of an occipital nerve stimulator (ONS). At 1-month follow-up, she began to experience pruritus across the back of her head and along the subcutaneous course of the lead. At 8 months, she continued to experience persistent symptoms, ultimately opting for device removal.

CONCLUSION

Although allergic reactions to implanted neurostimulation systems are rare, and mechanisms not completely understood, existing studies posit multiple theories surrounding the pathophysiology of allergic reactions to these devices, such as delayed hypersensitivity reactions or contact dermatitis. Further research is needed to elucidate the cutaneous and immunologic side effects of SCS and ONS devices.

Perioperative and anesthetic considerations for the management of neuromodulation systems

The use of neuromodulation systems is increasing for the treatment of various pathologies ranging from movement disorders to urinary incontinence to chronic pain syndromes. While the type of neuromodulation devices varies, they are largely categorized as intracranial (eg, deep brain stimulation), neuraxial (eg, spinal cord stimulation, dorsal root ganglion stimulation, and intrathecal drug delivery systems), or peripheral (eg, sacral nerve stimulation and peripheral nerve stimulation) systems. Given the increasing prevalence of these systems in the overall population, it is important for anesthesiologists, surgeons, and the perioperative healthcare team to familiarize themselves with these systems and their unique perioperative considerations. In this review, we explore and highlight the various neuromodulation systems, their general perioperative considerations, and notable special circumstances for perioperative management.

Incidence of Lead Migration With Loss of Efficacy or Paresthesia Coverage After Spinal Cord Stimulator Implantation: Systematic Review and Proportional Meta-Analysis of Prospective Studies and Randomized Clinical Trials

OBJECTIVE

The objective of this meta-analysis was to approximate the incidence of overall lead migration, clinically significant lead migration, and asymptomatic lead migration in patients who have undergone spinal cord stimulator implantation.

MATERIALS AND METHODS

A comprehensive literature search was performed for studies published before May 31, 2022. Only randomized controlled trials and prospective observational studies with more than ten patients were included. Two reviewers analyzed the articles from the literature search for final inclusion, after which, study characteristics and outcome data were extracted. The primary dichotomous categorical outcome variables were the incidence of overall lead migration, clinically significant lead migration (defined as lead migration resulting in loss of efficacy), and asymptomatic lead migration (defined as lead migration discovered incidentally on follow-up imaging) in patients with spinal cord stimulator implant. Freeman-Tukey arcsine square root transformation for meta-analysis of proportions using random effects (DerSimonian and Laird method) was used to calculate incidence rates for the outcome variables. Pooled incidence rates and 95% CIs were calculated for the outcome variables.

RESULTS

Fifty-three studies met the inclusion criteria, with a total of 2932 patients having received spinal cord stimulator implants. The pooled incidence of overall lead migration was 9.97% (95% CI of 7.62%-12.59%). Only 24 of the included studies commented on the clinical significance of reported lead migrations, of which every lead migration was clinically significant. In these 24 studies, 96% of the reported lead migrations required a revision procedure or explant. Unfortunately, no studies that reported lead migration commented on asymptomatic lead migrations; therefore, the incidence of asymptomatic lead migrations could not be defined.

CONCLUSIONS

This meta-analysis found that the rate of lead migration in patients who have received spinal cord stimulator implants is approximately one in ten patients. This likely closely approximates the incidence of clinically significant lead migration owing to the included studies not routinely performing follow-up imaging. Therefore, lead migrations were primarily discovered owing to loss of efficacy, and no included studies clearly reported asymptomatic lead migration. The results of this meta-analysis can be used to inform patients more accurately on the risks and benefits of spinal cord stimulator implantation.

Advances in Spinal Cord Stimulation

Neuromodulation, specifically spinal cord stimulation (SCS), has become a staple of chronic pain management for various conditions including failed back syndrome, chronic regional pain syndrome, refractory radiculopathy, and chronic post operative pain. Since its conceptualization, it has undergone several advances to increase safety and convenience for patients and implanting physicians. Current research and efforts are aimed towards novel programming modalities and modifications of existing hardware. Here we review the recent advances and future directions in spinal cord stimulation including a brief review of the history of SCS, SCS waveforms, new materials for SCS electrodes (including artificial skins, new materials, and injectable electrodes), closed loop systems, and neurorestorative devices.

Early Experience With a Novel Miniaturized Spinal Cord Stimulation System for the Management of Chronic Intractable Pain of the Back and Legs

INTRODUCTION

A novel, spinal cord stimulation (SCS) system with a battery-free miniaturized implantable pulse generator (IPG) was used in this feasibility study. The system uses an external power source that communicates bidirectionally with the IPG (< 1.5 cm³). Human factors, subject comfort, and effects on low back and leg pain were evaluated in this first-in-human study.

MATERIALS AND METHODS

A prospective, multicenter, open-label clinical trial was initiated to evaluate the safety and performance of a novel miniaturized stimulator in the treatment of chronic, intractable leg and low-back pain. Eligible subjects were recruited for the study and gave consent. Subjects who passed the screening/trial phase (defined as ≥ 50% decrease in pain) continued to the long-term implant phase and were followed up at predefined time points after device activation. Interim clinical and usability outcomes were captured and reported at 90 days.

RESULTS

Results of 22 subjects who chose a novel pulsed stimulation pattern therapy using the battery-free IPG (< 1.5 cm³) are described here. At 90-days follow-up, the average pain reduction was 79% in the leg (n = 22; p < 0.0001) and 76% in the low back (n = 21; p < 0.0001) compared with baseline. Responder rates (≥ 50% pain relief) at 90 days were 86% in leg pain (19/22) and 81% in low-back pain (17/21). Subjects rated the level of comfort of the external wearable power source to be 0.41 ± 0.73 at 90 days on an 11-point rating scale (0 = very comfortable, 10 = very uncomfortable).

DISCUSSION

These interim results from the ongoing study indicate the favorable efficacy and usability of a novel, externally powered, battery-free SCS IPG (< 1.5 cm³) for leg and low-back pain. Study subjects wore the external power source continuously and found it comfortable, and the system provided significant pain relief. These preliminary findings warrant further investigation.

CLINICAL TRIAL REGISTRATION

The Clinicaltrials.gov registration number for the study is ACTRN12618001862235.

Dural Puncture During Spinal Cord Stimulator Lead Insertion: Analysis of Practice Patterns

Background

Spinal cord stimulation (SCS) is an important modality for intractable pain not amenable to less conservative measures. During percutaneous SCS lead insertion, a critical step is safe access to the epidural space, which can be complicated by a dural puncture.

Objectives

In this review, we present and analyze the practices patterns in the event of a dural puncture during a SCS trial or implantation.

Methods

We conducted a survey of the practice patterns regarding spinal cord stimulation therapy. The survey was administered to members of the Spine Intervention Society and American Society of Regional Anesthesia specifically inquiring decision making in case of inadvertent dural puncture during spinal cord stimulator lead insertion.

Results

A maximum of 193 responded to a question regarding dural punctures while performing a SCS trial and 180 responded to a question regarding dural punctures while performing a SCS implantation. If performing a SCS trial and a dural puncture occurs, a majority of physicians chose to continue the procedure at a different level (56.99%), followed by abandoning the procedure (27.98%), continuing at the same level (10.36%), or choosing another option (4.66%). Similarly, if performing a permanent implantation and a dural puncture occurs, most physicians chose to continue the procedure at a different level (61.67%), followed by abandoning the procedure (21.67%), continuing at the same level (10.56%), or choosing another option (6.11%).

Conclusions

Whereas the goals of the procedure would support abandoning the trial but continuing with the permanent in case of inadvertent dural puncture, we found that decision choices were minimally influenced by whether the dural puncture occurred during the trial or the permanent implant. The majority chose to continue with the procedure at a different level while close to a quarter chose to abandon the procedure. This article sets a time stamp in practice patterns from March 20, 2020 to June 26, 2020. These results are based on contemporary SCS practices as demonstrated by this cohort, rendering the options of abandoning or continuing after dural puncture as reasonable methods. Though more data is needed to provide a consensus, providers can now see how others manage dural punctures during SCS procedures.

Burst Spinal Cord Stimulation in the Management of Chronic Pain: Current Perspectives

Over the last several decades, opioid diversion, misuse, and over-prescription have run rampant in the United States. Spinal cord stimulation (SCS) has been FDA approved for treatment for a primary indication of neuropathic limb pain that is resistant to more conservative medical therapy. The disorders qualified for treatment include neuropathic, post-surgical, post-amputation, osteodegenerative, and pain related to vascular disease. Some of the most frequently cited conditions for treatment of SCS include failed back surgery syndrome, complex regional pain syndrome (CRPS) Type I and Type II, and post-herpetic neuralgias. Developments in SCS systems have led to the differentiation between the delivered electromechanical waveform patterns, including tonic, burst, and high-frequency. Burst SCS mitigates traditional paresthesia due to expedited action potential and offers improved pain relief. Burst SCS has been shown in available studies to be non-inferior to the traditional SCS, which can cause pain paresthesia in patients who already have chronic pain. Burst SCS does not seem to cause or need the paresthesia seen in traditional SCS, making SCS not tolerable to patients. Moreover, some studies suggest that burst SCS may decrease opioid consumption in patients with chronic pain. This can make burst SCS an extremely useful tool in the battle against chronic pain and the raging opioid epidemic. As of now, more research needs to be performed to further delineate the effectiveness and long-term safety of this device.

Progress in the efficacy and mechanism of spinal cord stimulation in neuropathological pain

Neuropathic pain (NP) is a long-term recurrent disease caused by somatosensory nervous system injury, with spontaneous pain, hyperalgesia, ectopic pain, and paresthesia as the main clinical manifestations. It adversely affects patients' quality of life. NP treatments often include medication, physical therapy, and invasive therapy; the first two therapies are generally ineffective for some NP patients. These patients sometimes rely on invasive therapy to alleviate pain. Spinal cord stimulation (SCS) is a very effective therapeutic method. SCS is a neuroregulatory method that involves placing the electrodes on the corresponding painful spinal cords. Pain is greatly alleviated after SCS. SCS has been proven to be an effective therapeutic method for the treatment of neurological pain. Furthermore, SCS provides a feasible approach for patients with unsuccessful drug treatment. This paper reviews the relevant literature of spinal cord electrical stimulation, focusing on the mechanism of action, clinical application, clinical efficacy and technical progress of spinal cord electrical stimulation. SCS is widely used in the treatment of NP diseases such as postherpetic neuralgia, back surgery failure syndrome, and phantom limb pain. With advancements in science and technology, tremendous progress has also been made in the spinal cord electrical stimulation method and good momentum has been maintained.

Case report: Favorable outcomes of spinal cord stimulation in complex regional pain syndrome Type II consistent with thermography findings

Background:

Complex regional pain syndrome (CRPS) is a chronic pain disorder that develops as a consequence of trauma to one or more limbs. Despite the availability of multiple modalities to diagnose CRPS, a gold standard technique for definitive diagnosis is lacking. Moreover, there are limited reports describing the use of spinal cord stimulation (SCS) to treat CRPS Type II, given the low prevalence of this condition. Herein, we present the case of a patient with CRPS Type II with novel thermography findings who underwent SCS for pain management after an Achilles tendon repair surgery.

Case Description:

A 38-year-old woman was referred to our institute because of chronic left leg pain after Achilles tendon rupture repair surgery. Her case was diagnosed as CRPS Type II based on the International Association for the Study of Pain diagnostic criteria. After an epidural block, thermography showed a significant increase in the body surface temperature of the foot on the observed side. She was subsequently treated with SCS, following which her pain ameliorated. She reported no pain flare-ups or new neurological deficits over 2 years of postoperative follow-up assessments.

Conclusion:

SCS could be a useful surgical treatment for medication refractory CRPS Type II as supported by our thermography findings. We may refine surgical indication for permanent implantation of SCS with the presented method.

Percutaneous Spinal Cord Stimulation Lead Placement Under Deep Sedation and General Anesthesia

INTRODUCTION

Spinal cord stimulation (SCS) is a commonly utilized therapy for the treatment of neuropathic pain conditions. The Neurostimulation Appropriateness Consensus Committee (NACC) has recommended that the placement of percutaneous SCS leads be performed in an awake patient capable of providing feedback. It is not currently known how commonly this recommendation is adhered to by physicians in clinical practice. This article presents the findings of a survey designed to answer this important question.

METHODS

We conducted a survey of the active membership of the American Society of Regional Anesthesia and Pain Medicine (ASRA) and the Spine Intervention Society (SIS) regarding practice patterns with SCS therapy. We analyzed the percent of respondents who indicated that they use deep sedation and general anesthesia during SCS placement as well as any reported complications.

RESULTS

Many practitioners frequently utilize deep sedation as well as general anesthesia when performing SCS implants. Our findings demonstrate that 77% of physicians reported that they utilize deep sedation for permanent SCS implants at times, and 45% of physicians reported the use of general anesthesia for 10 kHz implants. Additionally, 94% of physicians reported that they have never had a complication related to the use of general anesthesia for a spinal cord stimulator placement.

CONCLUSIONS

This survey provides initial data on SCS practices among a large cohort of clinicians who utilize SCS. SCS lead placement under deep sedation and general anesthesia appears to be common practice for many physicians who perform implants. This survey should stimulate further research on this topic, given that the current safety guidelines and the rate of physicians reporting the use of deep sedation and general anesthesia for spinal cord stimulator placement remain at odds.

A Call to Action Toward Optimizing the Electrical Dose Received by Neural Targets in Spinal Cord Stimulation Therapy for Neuropathic Pain

Spinal cord stimulation has seen unprecedented growth in new technology in the 50 years since the first subdural implant. As we continue to grow our understanding of spinal cord stimulation and relevant mechanisms of action, novel questions arise as to electrical dosing optimization. Programming adjustment — dose titration — is often a process of trial and error that can be time-consuming and frustrating for both patient and clinician. In this report, we review the current preclinical and clinical knowledge base in order to provide insights that may be helpful in developing more rational approaches to spinal cord stimulation dosing. We also provide key conclusions that may help in directing future research into electrical dosing, given the advent of newer waveforms outside traditional programming parameters.

Invasive Treatments for Low Back Disorders

OBJECTIVE

This abbreviated version of the American College of Occupational and Environmental Medicine's Low Back Disorders guideline reviews the evidence and recommendations developed for invasive treatments used to manage low back disorders.

METHODS

Comprehensive systematic literature reviews were accomplished with article abstraction, critiquing, grading, evidence table compilation, and guideline finalization by a multidisciplinary expert panel and extensive peer-review to develop evidence-based guidance. Consensus recommendations were formulated when evidence was lacking and often relied on analogy to other disorders for which evidence exists. A total of 47 high-quality and 321 moderate-quality trials were identified for invasive management of low back disorders.

RESULTS

Guidance has been developed for the invasive management of acute, subacute, and chronic low back disorders and rehabilitation. This includes 49 specific recommendations.

CONCLUSION

Quality evidence should guide invasive treatment for all phases of managing low back disorders.

3D patient-specific spinal cord computational model for SCS management: potential clinical applications

BACKGROUND AND OBJECTIVE

Although Spinal Cord Stimulation (SCS) is an established therapy for treating neuropathic chronic pain, in tonic stimulation, postural changes, electrode migration or badly-positioned electrodes can produce annoying stimulation (intercostal neuralgia) in about 35% of the patients. SCS models are used to study the effect of electrical stimulation to better manage the stimulation parameters and electrode position. The goal of this work was to develop a realistic 3D patient-specific spinal cord model from a real patient and develop a future clinical application that would help physicians to optimize paresthesia coverage in SCS therapy.

METHODS

We developed two 3D patient-specific models from a high-resolution MRI of two patients undergoing SCS treatment. The model consisted of a finite element model of the spinal cord and a sensory myelinated nerve fiber model. The same simulations were performed with a generalized spinal cord model and we compared the results with the clinical data to evaluate the advantages of a patient-specific model. To identify the geometrical parameters that most influence the stimulation predictions, a sensitivity analysis was conducted. We used the patient-specific model to perform a clinical application involving the pre-implantation selection of electrode polarity and study the effect of electrode offset.

RESULTS

The patient-specific model correlated better with clinical data than the generalized model. Electrode-dura mater distance, dorsal CSF thickness, and CSF diameter are the geometrical parameters that caused significant changes in the stimulation predictions. Electrode polarity could be planned and optimized to stimulate the patient's painful dermatomes. The addition of offset in parallel electrodes would not have been beneficial for one of the patients of this study because they reduce neural activation displacement.

CONCLUSIONS

This is the first study to relate the activation area model prediction in dorsal columns with the clinical effect on paresthesia coverage. The outcomes show that 3D patient-specific models would help physicians to choose the best stimulation parameters to optimize neural activation and SCS therapy in tonic stimulation.

Neuromodulation for Medically Refractory Neuropathic Pain: Spinal Cord Stimulation, Deep Brain Stimulation, Motor Cortex Stimulation, and Posterior Insula Stimulation

BACKGROUND

The treatment of neuropathic pain (NP) continues to be controversial as well as an economic health issue and a challenge to health care. Neurosurgery can offer different methods of neuromodulation that may improve patients' condition, including deep brain stimulation (DBS), motor cortex stimulation (MCS), spinal cord stimulation (SCS), and posterior insula stimulation (PIS). There is no consensus of opinion as to the final effects of these procedures, which stimulation parameters to select, the correct timing, or how to select the patients who will best benefit from these procedures.

OBJECTIVE

To review the evidence available regarding these 4 procedures and the management of NP.

METHODS

We conducted a PubMed, Embase, and Cochrane Library database search from 1990 to 2020. The strategy of the search concentrated on the following keywords: "neuropathic pain," "chronic pain," "deep brain stimulation," "motor cortex stimulation," "spinal cord stimulation," "insula stimulation," and "neuromodulation." Studies that provided data regarding the immediate and long-term effectiveness of the procedure, anatomic stimulation target, percentage of pain control, and cause of the NP were included.

RESULTS

The most frequent causes of NP were phantom limb pain and central poststroke pain in the MCS group; central poststroke pain, phantom limb pain, and spinal cord injury (SCI) in the DBS group; and complex regional pain syndrome and failed back surgery syndrome in the SCS group. Pain improvement varied between 35% and 80% in the MCS group and 50% and 60% in the DBS group. In the SCS group, successful rates varied between 38% and 89%.

CONCLUSIONS

This systematic review highlights the literature supporting SCS, DBS, MCS, and PIS methods for the treatment of NP. We found consistent evidence supporting MCS, DBS, and SCS as possible treatments for NP; however, we were not able to define which procedure should be indicated for each cause. Furthermore, we did not find enough evidence to justify the routine use of PIS. We conclude that unanswered points need to be discussed in this controversial field and emphasize that new research must be developed to treat patients with NP, to improve their quality of life.

Socioeconomic Disparities in the Utilization of Spinal Cord Stimulation Therapy in Patients with Chronic Pain

OBJECTIVES

Spinal cord stimulation (SCS) therapies are used in the management of patients with complex regional pain syndrome I (CRPS I) and failed back surgery syndrome (FBSS). The purpose of this study was to investigate the racial and health insurance inequalities with SCS therapy in patients with chronic pain who had CRPS I and FBSS.

METHODS

Patients with chronic pain who had a discharge diagnosis of FBSS and CRPS I were identified using the National Inpatient Sample database. Our primary outcome was defined as the history of SCS utilization by race/ethnicity, income quartile, and insurance status. Multivariable logistic regression was used to determine the variables associated with utilization of SCS therapy.

RESULTS

Between 2011 and 2015, 40,858 patients who were hospitalized with a primary diagnosis of FBSS and/or CRPS I were identified. Of these patients, 1,082 (2.7%) had a history of SCS therapy. Multivariable regression analysis revealed that compared to White patients, Black and Hispanic patients had higher odds of having SCS therapy (Black patients: odds ratio [OR] = 1.41; 95% confidence interval [CI], 1.12 to 1.77; P = 0.003; Hispanic patients: OR = 1.41; 95% CI, 1.10 to 1.81; P = 0.007). Patients with private insurance had significantly higher odds of having SCS therapy compared with those with Medicare (OR = 1.24; 95% CI, 1.08 to 1.43; P = 0.003). Compared to patients with Medicare, Medicaid patients had lower odds of having SCS therapy (OR = 0.50; 95% CI, 0.36 to 0.70; P < 0.001).

CONCLUSIONS

Our study suggests that socioeconomic disparities may exist in the utilization of SCS among hospitalized patients with CRPS I and FBSS the United States. However, confirming these data from other administrative databases, in the outpatient setting, may shed more insight.

Treatment of a Large Cohort of Veterans Experiencing Musculoskeletal Disorders with Spinal Cord Stimulation in the Veterans Health Administration: Veteran Characteristics and Outcomes

OBJECTIVE

Spinal cord stimulator (SCS) implantation is used to treat chronic pain, including painful musculoskeletal disorders (MSDs). This study examined the characteristics and outcomes of veterans receiving SCSs in Veterans Health Administration (VHA) facilities.

METHODS

The sample was drawn from the MSD Cohort and limited to three MSDs with the highest number of implants (N=815,475). There were 1490 veterans with these conditions who received SCS implants from 2000 to 2012, of which 95% (n=1414) had pain intensity numeric rating scale (NRS) data both pre- and post-implant.

RESULTS

Veterans who were 35-44 years old, White, and married reported higher pain NRS ratings, had comorbid inclusion diagnoses, had no medical comorbidities, had a BMI 25-29.9, or had a depressive disorder diagnosis were more likely to receive an SCS. Veterans 55+ years old or with an alcohol or substance use disorder were less likely to receive an SCS. Over 90% of those receiving an SCS were prescribed opioids in the year prior to implant. Veterans who had a presurgical pain score ≥4 had a clinically meaningful decrease in their pain score in the year following their 90-day recovery period (Day 91-456) greater than expected by chance alone. Similarly, there was a significant decrease in the percent of veterans receiving opioid therapy (92.4% vs 86.6%, p<0.0001) and a significant overall decrease in opioid dose [morphine equivalent dose per day (MEDD) =26.48 vs MEDD=22.59, p<0.0003].

CONCLUSION

Results offer evidence of benefit for some veterans with the examined conditions. Given known risks of opioid therapy, the reduction is an important potential benefit of SCS implants.

Long-Term Outcome of Spinal Cord Stimulation in Failed Back Surgery Syndrome: 20 Years of Experience With 224 Consecutive Patients

BACKGROUND

Failed back surgery syndrome (FBSS) is a challenging condition that lacks a curative treatment. In selected patients, spinal cord stimulation (SCS) has provided a satisfactory outcome.

OBJECTIVE

To evaluate the long-term outcome of SCS in FBSS, as measured by (1) the explantation rate, (2) complications, and (3) patient satisfaction with the global perceived effect (GPE).

METHODS

We studied 224 consecutive FBSS patients who underwent an SCS trial with surgically implanted leads at our hospital between January 1996 and December 2014. The patients' satisfaction with the GPE of treatment was measured through a postal questionnaire at the end of follow-up.

RESULTS

Based on a 1-wk trial, permanent SCS was implanted in 175 (78%) patients. Out of these patients, 153 (87%) reported satisfactory outcomes after 2 mo. During the mean follow-up of 6 yr, 34 (19%) of SCS devices were permanently explanted due to inadequate pain relief, and 11 (6%) were explanted for other reasons.Electrode revision due to inadequate pain relief was done for 22 patients. In total, 26 complications were reported due to: 7 deep infections, 11 hardware malfunctions, 1 subcutaneous hematoma, 4 instances of discomfort due to the pulse generator, and 3 electrode migrations.One hundred thirty patients (74%) continued with SCS until the end of follow-up. Of them, 61 (47%) returned the questionnaire, and 42 (69%) reported substantially improved or better GPE.

CONCLUSION

SCS can provide a good outcome in the treatment of FBSS. Patient selection could be further improved by developing novel predictive biomarkers.

Spinal cord stimulation failure: evaluation of factors underlying hardware explantation

OBJECTIVE

Spinal cord stimulation has been shown to improve pain relief and reduce narcotic analgesic use in cases of complex refractory pain syndromes. However, a subset of patients ultimately undergoes removal of the spinal cord stimulator (SCS) system, presumably because of surgical complications or poor efficacy. This retrospective study addresses the paucity of evidence regarding risk factors and underlying causes of spinal cord stimulation failures that necessitate this explantation.

METHODS

In this retrospective single-center review, 129 patients underwent explantation of SCS hardware during a 9-year period (2005-2013) following initial placement at the authors' institution or elsewhere. Medical history, including indication of implantation, device characteristics, revision history, and reported reasons for removal of hardware, were reviewed.

RESULTS

The 74 (57%) women and 55 (43%) men were a median of 49 years old (IQR 41-61 years) at explantation; the median time to explantation was 20 months (IQR 7.5-45.5 months). Thoracic or upper lumbar leads were placed in 89.9% of patients primarily for the diagnosis of postsurgical failed-back surgery syndrome (70.5%), chronic regional pain syndrome (14.7%), and neuropathic pain (8.5%). More than half of patients were legally disabled. Initial postoperative reduction in pain was reported in 81% of patients, and 37.8% returned to work. Among 15 patients with acute postsurgical complications (12 infections, 2 hemorrhages, 1 immediate paraplegia), the median time to removal was 2 months. Primary reasons for hardware removal were lack of stimulation efficacy (81%), electrode failure due to migration (14%), and allergic reactions to implanted hardware in 2 patients. The 72 patients who underwent formal psychiatric evaluation before implantation were affected by high rates of major depression (64%), anxiety (34%), posttraumatic stress disorder (PTSD) (12%), drug or alcohol abuse (12%), and physical or sexual abuse (22%).

CONCLUSIONS

The authors' findings provide insight regarding the mechanisms of spinal cord stimulation failure that resulted in total removal of the implanted system. The relationship between spinal cord stimulation failure and certain psychiatric disorders, such as PTSD, depression, and anxiety, is highlighted. Ultimately, this work may shed light on potential avenues to reduce morbidity and improve patient outcomes.

Evolving Techniques and Indications in Peripheral Nerve Stimulation for Pain

Peripheral nerve stimulation is the direct electrical stimulation of named nerves outside the central neuraxis to alleviate pain in the distribution of the targeted peripheral nerve. These treatments have shown efficacy in treating a variety of neuropathic, musculoskeletal, and visceral refractory pain pathologies; although not first line, these therapies are an important part of the treatment repertoire for chronic pain. With careful patient selection and judicious choice of stimulation technique, excellent results can be achieved for a variety of pain etiologies and distributions. This article reviews current and past practices of peripheral nerve stimulation and upcoming advancements in the field.

Spinal Cord Stimulation for Neuropathic Pain: Current Trends and Future Applications

The origin and the neural pathways involved in chronic neuropathic pain are still not extensively understood. For this reason, despite the wide variety of pain medications available on the market, neuropathic pain is challenging to treat. The present therapeutic alternative considered as the gold standard for many kinds of chronic neuropathic pain is epidural spinal cord stimulation (SCS). Despite its proved efficacy, the favourable cost-effectiveness when compared to the long-term use of poorly effective drugs and the expanding array of indications and technical improvements, SCS is still worldwide largely neglected by general practitioners, neurologists, neurosurgeons and pain therapists, often bringing to a large delay in considering as a therapeutic option for patients affected by neuropathic chronic pain. The present state of the art of SCS in the treatment of chronic neuropathic pain is here overviewed and speculations on whether to use a trial period or direct implant, to choose between percutaneous leads or paddle electrodes and on the pros and cons of the different patterns of stimulation presently available on the market (tonic stim, high-frequency stim and burst stim) are described.

Spinal cord stimulation for cancer-related pain in adults

BACKGROUND

This is an update of a review first published in The Cochrane Library in Issue 3, 2013. Cancer-related pain places a heavy burden on public health with related high expenditure. Severe pain is associated with a decreased quality of life in patients with cancer. A significant proportion of patients with cancer-related pain are under-treated. There is a need for more effective control of cancer-related pain. Spinal cord stimulation (SCS) may have a role in pain management. The effectiveness and safety of SCS for patients with cancer-related pain is currently unknown.

OBJECTIVES

This systematic review evaluated the effectiveness of SCS for cancer-related pain compared with standard care using conventional analgesic medication. We also appraised risk and potential adverse events associated with the use of SCS.

SEARCH METHODS

This is an update of a review first published in The Cochrane Library in Issue 3, 2013. The search strategy for the update was the same as in the original review. We searched the following bibliographic databases in order to identify relevant studies: the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library; MEDLINE; EMBASE; and CBM (Chinese Biomedical Database) in October 2014. We also handsearched relevant journals. There were no language restrictions.

SELECTION CRITERIA

We planned to include randomised controlled trials (RCTs) that directly compared SCS with other interventions with regards to the effectiveness of pain management. We also planned to include cross-over trials that compared SCS with another treatment. We planned to identify non-randomised controlled trials but these would only be included if no RCTs could be found.

DATA COLLECTION AND ANALYSIS

The literature search for the update of this review found 121 potentially eligible articles. The initial search strategy yielded 430 articles. By scrutinising titles and abstracts, we found 412 articles irrelevant to the analytical purpose of this systematic review due to different scopes of diseases or different methods of intervention (intrathecal infusion system; oral medication) or aims other than pain control (spinal cord function monitoring, bladder function restoration or amelioration of organ metabolism). The remaining 18 trials were reviewed as full manuscripts. No RCTs were identified. Fourteen sporadic case reports and review articles were excluded and four before-and-after case series studies (92 participants) were included. Two review authors independently selected the studies to be included in the review according to the prespecified eligibility criteria. A checklist for methodological quality of non-randomised controlled trials was used (STROBE checklist) and all review authors discussed and agreed on the inclusion of trials and the results of the quality assessment.

MAIN RESULTS

No new studies were identified for inclusion in this update of the review. Four before-and-after case series studies (a total of 92 participants) met our criteria for inclusion in the previous version of the review. All included trials adopted a visual analogue scale (VAS) to evaluate pain relief. Heterogeneity existed in terms of baseline characteristics, electrode and stimulator parameters, level of implantation and route of implantation; each trial reported data differently. In two trials, pain relief was achieved in 76% (48/63) of participants at the end of the follow-up period. In the third trial, pre-procedure VAS was 6 to 9 (mean 7.43 ); the one-month post-implant VAS was 2 to 4 (mean 3.07); the 12-month post-implant VAS was 1 to 3 (mean 2.67). In the fourth trial, the pre-procedure VAS was 6 to 9 (mean 7.07); 1 to 4 (mean 2.67) at one-month; 1 to 4 (mean 1.87) at 12 months. Analgesic use was largely reduced. The main adverse events were infection of sites of implantation, cerebrospinal fluid (CSF) leakage, pain at the sites of electrodes, dislodgement of the electrodes, and system failure; however, the incidence in participants with cancer could not be calculated. Since all trials were small, non-randomised controlled trials, they carried high or unclear risk of all types of bias.

AUTHORS' CONCLUSIONS

Since the first publication of this review, no new studies were identified. Current evidence is insufficient to establish the role of SCS in treating refractory cancer-related pain. Future randomised studies should focus on the implantation of SCS in participants with cancer-related pain.

Spinal cord stimulation is safe and feasible in patients with advanced heart failure: early clinical experience

AIMS

Pre-clinical work suggests that upper thoracic spinal cord stimulation (SCS) may have therapeutic effects in the treatment of heart failure (HF). We therefore aim to assess the safety and feasibility of SCS in HF patients.

METHODS AND RESULTS

A prospective, randomized, double-blind, crossover pilot study was conducted in symptomatic HF patients receiving optimal medical therapy. Patients were implanted with an SCS system and randomized to an SCS-ACTIVE, delivered at 90% paraesthesia threshold, or an SCS-INACTIVE phase for 3 months, followed by a 1-month washout period and crossover to the alternative phase. The safety of SCS therapy was assessed by death and cardiac events. Implantable cardioverter defibrillator (ICD) function in the presence of SCS was tested by defibrillation testing during SCS system implant and review of real-time and stored electrograms during follow-up. The efficacy of SCS therapy was assessed by changes in patient symptoms, LV function, and BNP level. Nine patients were investigated. In all cases, ICD sensing, detection, and therapy delivery were unaffected by SCS. During follow-up, one patient died and one was hospitalized for HF while in the SCS-INACTIVE phase, and two patients had HF hospitalizations during the SCS-ACTIVE phase. Symptoms were improved in the majority of patients with SCS, while markers of cardiac structure and function were, in aggregate, unchanged.

CONCLUSION

This study shows that an SCS system can be safely implanted in patients with advanced HF and that the SCS system does not interfere with ICD function.

Peripheral nerve field stimulation (PNFS) in chronic low back pain: a prospective multicenter study

OBJECTIVES

The goal of this study was to evaluate the long-term efficacy and safety of peripheral nerve field stimulation (PNFS) for chronic low back pain (cLBP).

MATERIALS AND METHODS

In this prospective, multicenter observational study, 118 patients were admitted to 11 centers throughout Austria and Switzerland. After a screening visit, all patients underwent a trial stimulation period of at least seven days before implantation of the permanent system. Leads were placed in the subcutaneous tissues of the lower back directly in the region of greatest pain. One hundred five patients were implanted with a permanent stimulating system. Patients' evaluation of pain and functional levels were completed before implantation and one, three, and six months after implantation. Adverse events, medication usage, and coverage of the painful area and predictive value of transcutaneous electrical nerve stimulation (TENS) were monitored.

RESULTS

All pain and quality-of-life measures showed statistically significant improvement during the treatment period. These included the average pain visual analog scale, the Oswestry Disability Questionnaire, the Becks Depression Inventory, and the Short Form-12 item Health survey. Additionally, medication usage with opioids, nonsteroidal anti-inflammatory drugs, and anti-convulsants showed a highly significant reduction. Complications requiring surgical intervention were reported in 9.6% of the patients. The degree of coverage of painful areas seems to be an important criterion for efficacy of PNFS, whereas TENS is presumably no predictor.

CONCLUSIONS

This prospective, multicenter study confirms that PNFS is an effective therapy for the management of cLBP. Significant improvements in many aspects of the pain condition were measured, and complications were minimal.

Spinal cord stimulation for cancer-related pain in adults

BACKGROUND

Cancer-related pain places a heavy burden on public health with related high expenditure. Severe pain is associated with a decreased quality of life in patients with cancer. A significant proportion of patients with cancer-related pain are under-treated.There is a need for more effective control of cancer-related pain. Spinal cord stimulation (SCS) may have a role in pain management. The effectiveness and safety of SCS for patients with cancer-related pain is currently unknown.

OBJECTIVES

This systematic review evaluated the effectiveness of SCS for cancer-related pain compared with standard care using conventional analgesic medication. We also appraised risk and potential adverse events associated with the use of SCS.

SEARCH METHODS

We searched the following bibliographic databases in order to identify relevant studies: the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Libary (from inception to 2012, Issue 6); MEDLINE; EMBASE; and CBM (Chinese Biomedical Database) (from inception to July, 2012). We also handsearched relevant journals.

SELECTION CRITERIA

We planned to include randomised controlled trials (RCTs) that directly compared SCS with other interventions with regards to the effectiveness of pain management. We also planned to include cross-over trials that compared SCS with another treatment. We planned to identify non-randomised controlled trials but these would only be included if no RCTs could be found.

DATA COLLECTION AND ANALYSIS

The initial search strategy yielded 430 articles. By scrutinising titles and abstracts, we found 412 articles irrelevant to the analytical purpose of this systematic review due to different scopes of diseases or different methods of intervention (intrathecal infusion system; oral medication) or aims other than pain control (spinal cord function monitoring, bladder function restoration or amelioration of organ metabolism). The remaining 18 trials were reviewed as full manuscripts. No RCTs were identified. Fourteen sporadic case reports and review articles were excluded and four before-and-after case series studies (92 participants) were included. Two review authors independently selected the studies to be included in the review according to the pre-specified eligibility criteria. A checklist for methodological quality of non-randomised controlled trials was used (STROBE checklist) and all review authors discussed and agreed on the inclusion of trials and the results of the quality assessment.

MAIN RESULTS

Four before-and-after case series studies (a total of 92 participants) met our criteria for inclusion. All included trials adopted a visual analogue scale (VAS) to evaluate pain relief. Heterogeneity existed in terms of baseline characteristics, electrode and stimulator parameters, level of implantation and route of implantation; data reporting was different among all trials. In two trials, pain relief was achieved in 76% (48/63) of patients at the end of the follow-up period. In the third trial, pre-procedure VAS was 6 to 9 (mean 7.43 ); the one-month post-implant VAS was 2 to 4 (mean 3.07); the 12-month post-implant VAS was 1 to 3 (mean 2.67). In the fourth trial, the pre-procedure VAS was 6 to 9 (mean 7.07); 1 to 4 (mean 2.67) at one-month; 1 to 4 (mean 1.87) at 12 months. Analgesic use was largely reduced. The main adverse events were infection of sites of implantation, cerebrospinal fluid (CSF) leakage, pain at the sites of electrodes, dislodgement of the electrodes and system failure, however, the incidence in patients with cancer could not be calculated. Since all trials were non-randomised controlled trials, they carried risk of all types of bias.

AUTHORS' CONCLUSIONS

Current evidence is insufficient to establish the role of SCS in treating refractory cancer-related pain. Future randomised studies should focus on the implantation of SCS in patients with cancer-related pain.

The use of intraoperative electrophysiology for the placement of spinal cord stimulator paddle leads under general anesthesia

BACKGROUND

Placement of spinal cord stimulating paddle leads has traditionally been performed under local anesthesia with intravenous sedation to allow intraoperative confirmation of appropriate placement. It may be difficult to maintain appropriate sedation in certain patients because of medical comorbidities. Furthermore, patients undergoing lead revision frequently have extensive epidural scarring, requiring multilevel laminectomies to place the electrode appropriately.

OBJECTIVE

To report our technique of neurophysiologic monitoring that allows these procedures to be performed under general anesthesia.

METHODS

Data from 78 patients who underwent electromyography during laminectomy for paddle lead placement were retrospectively reviewed. Seventy patients presented for first-time permanent system placement after a successful trial, and 8 were referred for revision or replacement of previously functioning systems. Surgeries were performed under general anesthesia with fluoroscopic guidance. Electromyography was used to help define the physiological midline of the spinal cord and to guide appropriate lead placement. Somatosensory evoked potentials were used as an adjunct to minimize the possibility of neural injury.

RESULTS

Immediately postoperatively, 75 of 78 patients reported that the paresthesia coverage was as good as (or better than) that of the spinal cord stimulation trial. At the long-term follow-up, 1 system was removed for infection, and 6 systems were explanted for lack of efficacy. A total of 64 of the 78 implanted patients reported continued pain relief with stimulator use. Revision surgery was performed in 9 patients.

CONCLUSION

The use of intraoperative electrophysiology for the placement of spinal cord stimulation paddle leads under general anesthesia is a safe and efficacious alternative to awake surgery.

A voltage-controlled capacitive discharge method for electrical activation of peripheral nerves

OBJECTIVES

A voltage-controlled capacitive discharge (VCCD) method was investigated as an alternative to rectangular stimulus pulses currently used in peripheral nerve stimulation therapies.

METHODS AND MATERIALS

 In two anesthetized Gottingen mini pigs, the threshold (total charge per phase) for evoking a compound nerve action potential (CNAP) was compared between constant current (CC) and VCCD methods. Electrical pulses were applied to the tibial and posterior cutaneous femoralis nerves using standard and modified versions of the Medtronic 3778 Octad.

RESULTS

 In contrast to CC stimulation, the combined application of VCCD pulses with a modified Octad resulted in a marked decrease (-73 ± 7.4%) in the stimulation threshold for evoking a CNAP. This was consistent for different myelinated fiber types and locations of stimulation.

CONCLUSIONS

 The VCCD method provides a highly charge-efficient means of activating myelinated fibers that could potentially be used within a wireless peripheral nerve stimulator system.

Can the human lumbar posterior columns be stimulated by transcutaneous spinal cord stimulation? A modeling study

Stimulation of different spinal cord segments in humans is a widely developed clinical practice for modification of pain, altered sensation, and movement. The human lumbar cord has become a target for modification of motor control by epidural and, more recently, by transcutaneous spinal cord stimulation. Posterior columns of the lumbar spinal cord represent a vertical system of axons and when activated can add other inputs to the motor control of the spinal cord than stimulated posterior roots. We used a detailed three-dimensional volume conductor model of the torso and the McIntyre-Richard-Grill axon model to calculate the thresholds of axons within the posterior columns in response to transcutaneous lumbar spinal cord stimulation. Superficially located large-diameter posterior column fibers with multiple collaterals have a threshold of 45.4 V, three times higher than posterior root fibers (14.1 V). With the stimulation strength needed to activate posterior column axons, posterior root fibers of large and small diameters as well as anterior root fibers are coactivated. The reported results inform on these threshold differences, when stimulation is applied to the posterior structures of the lumbar cord at intensities above the threshold of large-diameter posterior root fibers.

What's new in the diagnosis and treatment of peripheral nerve entrapment neuropathies

Entrapment neuropathies can be common conditions with the potential to cause significant disability. Correct diagnosis is essential for proper management. This article is a review of recent developments related to diagnosis and treatment of various common and uncommon nerve entrapment disorders. When combined with classical peripheral nerve examination techniques, innovations in imaging modalities have led to more reliable diagnoses. Moreover, innovations in conservative and surgical techniques have been controversial as to their effects on patient outcome, but randomized controlled trials have provided important information regarding common operative techniques. Treatment strategies for painful peripheral neuropathies are also reviewed.

Case report: successful epiradicular peripheral nerve stimulation of the C2 dorsal root ganglion for postherpetic neuralgia

BACKGROUND

Postherpetic neuralgia (PHN) is the most common complication following an acute varicella zoster virus infection. PHN often results in a chronic severe pain condition refractory to conservative pain management treatments. Peripheral nerve stimulation over the affected spinal nerve root may be an effective treatment option for patients with intractable PHN.

OBJECTIVE

To describe a successful case of peripheral nerve stimulation of the second cervical dorsal root ganglion for the treatment of intractable PHN.

CASE REPORT

An 80-year-old man with a 15-month history of severe PHN was referred to our clinic for pain management. His pain was localized to the left side in the distribution of the C2 dermatome. The patient's pain was unresponsive to comprehensive conventional treatments for PHN including physical therapy, membrane stabilizing medications, opioids, anti-inflammatories, cervical epidural steroid injections, cervical facet joint injections, and dorsal root ganglion blockade with pulsed radiofrequency. After failing to respond to conservative and interventional therapies, a peripheral nerve stimulator trial was conducted for a period of seven days. The lead was placed within the epidural space over the atlanto-axial joint under fluoroscopy to stimulate the left C2 nerve root. This trial resulted in a significant decrease of the patient's pain, and discontinuation of all pain medications.

CONCLUSION

We describe a case of successful electrode placement at the C2 spinal level for the treatment of refractory PHN.