Traditional Spinal Cord Stimulation Research Articles

Spinal Cord Stimulation for Visceral Pain: Present Approaches and Future Strategies.

The introduction of successful neuromodulation strategies for managing chronic visceral pain lag behind what is now treatment of choice in refractory chronic back and extremity pain for many providers in the United States and Europe. Changes in public policy and monetary support to identify nonopioid treatments for chronic pain have sparked interest in alternative options. In this review, we discuss the scope of spinal cord stimulation (SCS) for visceral pain, its limitations, and the potential role for new intradural devices of the type that we are developing in our laboratories, which may be able to overcome existing challenges. A review of the available literature relevant to this topic was performed, with particular focus on the pertinent neuroanatomy and uses of spinal cord stimulation systems in the treatment of malignant and nonmalignant gastrointestinal, genitourinary, and chronic pelvic pain. To date, there have been multiple off-label reports testing SCS for refractory gastrointestinal and genitourinary conditions. Though some findings have been favorable for these organs and systems, there is insufficient evidence to make this practice routine. The unique configuration and layout of the pelvic pain pathways may not be ideally treated using traditional SCS implantation techniques, and intradural stimulation may be a viable alternative. Despite the prevalence of visceral pain, the application of neuromodulation therapies, a standard approach for other painful conditions, has received far too little attention, despite promising outcomes from uncontrolled trials. Detailed descriptions of visceral pain pathways may offer several clues that could be used to implement devices tailored to this unique anatomy.

The Evolving Role of High-Frequency Spinal Cord Stimulation as Salvage Therapy in Neurostimulation.

High-frequency 10-kHz spinal cord stimulation (10-kHz SCS) has shown promise in multicenter prospective trials for the management of chronic back and leg pain. Traditional spinal cord stimulation (t-SCS) has a long history of effectiveness in chronic neuropathic syndromes but not uncommonly can fail to provide long-term relief, leaving a significant group of patients with unsatisfactory outcomes. There is mounting evidence that 10-kHz SCS may offer relief in this subset of patients. The purpose of this retrospective analysis was to report a single-institution long-term experience of 10-kHz SCS in patients who did not get adequate pain relief with prior t-SCS devices. A temporary trial of 10-kHz SCS was carried out for 7days, and those experiencing an average of 50% reduction in pain intensity underwent implantation. Patients were classified as moderate responders if relief was 31% to 50% and excellent responders if pain relief exceeded 50%. Thirty-one patients who had experienced failed t-SCS primarily from poor paresthesia coverage underwent a trial of 10-kHz SCS and 29 underwent implantation. Twenty-eight patients were available for analysis, with 57.1% experiencing 30% response and 46.4% experiencing excellent response at a median follow-up of 21.2(±8.4) months. This small single-institution study suggests that a significant proportion of patients with previously failed t-SCS may achieve clinically meaningful and durable pain relief with 10-kHz SCS.

Modulation of Spinal Nociceptive Transmission by Sub-Sensory Threshold Spinal Cord Stimulation in Rats After Nerve Injury

High-frequency spinal cord stimulation (SCS) administered below the sensory threshold (subparesthetic) can inhibit pain, but the mechanisms remain obscure. We examined how different SCS paradigms applied at intensities below the threshold of Aβ-fiber activation (sub-sensory threshold) affect spinal nociceptive transmission in rats after an L5 spinal nerve ligation (SNL). Electrophysiology was used to record local field potential (LFP) at L4 spinal cord before, during, and 0-60 min after SCS in SNL rats. LFP was evoked by high-intensity paired-pulse test stimulation (5 mA, 0.2 msec, 400 msec interval) at the sciatic nerve. Epidural SCS was delivered through a miniature electrode placed at T13-L1 and L2-L3 spinal levels. Four patterns of SCS (200 Hz, 1 msec; 500 Hz, 0.5 msec; 1200 Hz; 0.2 msec; 10,000 Hz, 0.024 msec, 30 min, bipolar) were tested at 90% Aβ-threshold as a subthreshold intensity. As a positive control, traditional SCS (50 Hz, 0.2 msec) was tested at 100% Aβ-plateau as a suprathreshold intensity. Traditional suprathreshold SCS at T13-L1 level significantly reduced LFP to C-fiber inputs (C-LFP). Subthreshold SCS of 200 and 500 Hz, but not 1200 or 10,000 Hz, also reduced C-LFP, albeit to a lesser extent than did traditional SCS (n = 7-10/group). When SCS was applied at the L2-L3 level, only traditional SCS and subthreshold SCS of 200 Hz inhibited C-LFP (n = 8-10/group). Traditional suprathreshold SCS acutely inhibits spinal nociceptive transmission. Low-frequency subthreshold SCS with a long pulse width (200 Hz, 1 msec), but not higher-frequency SCS, also attenuates C-LFP.

Finding Optimal Neuromodulation for Chronic Pain: Waves, Bursts, and Beyond.

Spinal cord stimulation (SCS) has emerged as state-of-the-art evidence-based treatment for chronic intractable pain related to spinal and peripheral nerve disorders. Traditionally delivered as steady-state, paraesthesia-producing electrical stimulation, newer technology has augmented the SCS option and outcome in the last decade. To present an overview of the traditional and newer SCS waveforms. We present a short literature review of SCS waveforms in reference to newer waveforms and describing paraesthesia-free, high frequency, and burst stimulation methods as well as advances in waveform paradigms and programming modalities. Pertinent literature was reviewed, especially in the context of evolution in the waveforms of SCS and stimulation parameters. Conventional tonic SCS remains one of the most utilized and clinically validated SCS waveforms. Newer waveforms such as burst stimulation, high-frequency stimulation, and the sub-perception SCS have emerged in the last decades with favorable results with no or minimal paraesthesia, including in cases otherwise intractable to conventional tonic SCS. The recent evolution and experience of closed-loop SCS is promising and appealing. The experience and validation of the newer SCS waveforms, however, remain limited but optimistic. Advances in SCS device technology and waveforms have improved patient outcomes, leading to its increased utilization of SCS for chronic pain. These improvements and the development of closed-loop SCS have been increasingly promising development and foster a clinical translation of improved pain relief as the years of research and clinical study beyond conventional SCS waveform come to fruition.

High Frequency (HF10) Spinal Cord Stimulation for Chronic Neuropathic Pain.

Spinal cord stimulation (SCS) is well established treatment. In a prospective randomised controlled trial, novel 10-kHz High-frequency Therapy (HF10 Therapy) was superior to traditional low-frequency SCS for the treatment of chronic back and leg pain. To demonstrate the percutaneous SCS implant technique and discuss the operative nuances. During the stage 1 procedure (permanent trial), two percutaneous electrodes were placed in the midline posterior epidural space spanning T8-T10 segments straddling the T9-10 disc space. The electrodes were anchored to the fascia, tunnelled into the supragluteal incision and connected to the extensions, which were tunnelled out for the external trial. The patient reported 90% pain reduction at follow-up. Thoracic HF10 SCS is effective modality in managing chronic neuropathic pain.

Synergetic efficacy of simultaneous DRG- and traditional spinal cord stimulation

Dorsal root ganglion stimulation has established its role in chronic pain states and is commonly used as an alternative treatment to traditional spinal cord stimulation. Due to its approach, DRG stimulation is preferably used in pain conditions affecting a small area or a distinct nerve root. In selected patients, a combination of both techniques might be useful. We report a series of five patients with chronic pain treated with DRG stimulation and traditional spinal cord stimulation from 2011 to 2018. Pain was reported on the VAS scale at the baseline, before and 12months after the second procedure. All patients suffered from back and lower limb pain, four with a FBSS syndrome, one with CRPS. In all but one patient, SCS was implanted first and complemented with a DRG in the course (4-90months between procedures). An additional stimulation system was implanted because the previous stimulation failed to reach the pain area or because the patient had an altered perception of other pain component after stimulation. All but one patient had a consistent and satisfying therapeutic effect with both systems activated. The combination of dorsal root ganglion and traditional spinal cord stimulation is surgically and technically feasible. In selected patients, the combination of both methods offers an option to alleviate pain states not sufficiently or not efficiently treated with one method alone. The introduction of IPGs combining SCS and DRG stimulation paradigms might be useful to increase acceptance of this option.

Spinal cord stimulation prevents paclitaxel-induced mechanical and cold hypersensitivity and modulates spinal gene expression in rats.

Paclitaxel-induced peripheral neuropathy (PIPN) is a common dose-limiting side effect of this cancer treatment drug. Spinal cord stimulation (SCS) has demonstrated efficacy for attenuating some neuropathic pain conditions. We aim to examine the inhibitory effect of SCS on the development of PIPN pain and changes of gene expression in the spinal cord in male rats after SCS. We examined whether traditional SCS (50 Hz, 6-8 h/session daily for 14 consecutive days) administered during paclitaxel treatment (1.5 mg/kg, i.p.) attenuates PIPN-related pain behavior. After SCS treatment, we performed RNA-seq of the lumbar spinal cord to examine which genes are differentially expressed after PIPN with and without SCS. Compared to rats treated with paclitaxel alone (n = 7) or sham SCS (n = 6), SCS treatment (n = 11) significantly inhibited the development of paclitaxel-induced mechanical and cold hypersensitivity, without altering open-field exploratory behavior. RNA-seq showed that SCS induced upregulation of 836 genes and downregulation of 230 genes in the spinal cord of paclitaxel-treated rats (n = 3) as compared to sham SCS (n = 5). Spinal cord stimulation upregulated immune responses in paclitaxel-treated rats, including transcription of astrocyte- and microglial-related genes, but repressed transcription of multiple gene networks associated with synapse transmission, neuron projection development, γ-aminobutyric acid reuptake, and neuronal plasticity. Our findings suggest that traditional SCS may attenuate the development of pain-related behaviors in PIPN rats, possibly by causing aggregate inhibition of synaptic plasticity through upregulation and downregulation of gene networks in the spinal cord.

Mechanism of dorsal root ganglion stimulation for pain relief in painful diabetic polyneuropathy is not dependent on GABA release in the dorsal horn of the spinal cord.

AimsIt is hypothesized that dorsal root ganglion stimulation (DRGS), sharing some of the mechanisms of traditional spinal cord stimulation (SCS) of the dorsal columns, induces γ‐aminobutyric acid (GABA) release from interneurons in the spinal dorsal horn.MethodsWe used quantitative immunohistochemical analysis in order to investigate the effect of DRGS on intensity of intracellular GABA‐staining levels in the L4‐L6 spinal dorsal horn of painful diabetic polyneuropathy (PDPN) animals. To establish the maximal pain relieving effect, we tested for mechanical hypersensitivity to von Frey filaments and animals received 30 minutes of DRGS at day 3 after implantation of the electrode. One day later, 4 Sham‐DRGS animals and four responders‐to‐DRGS received again 30 minutes of DRGS and were perfused at the peak of DRGS‐induced pain relief.ResultsNo significant difference in GABA‐immunoreactivity was observed between DRGS and Sham‐DRGS in lamina 1‐3 of the spinal levels L4‐6 neither ipsilaterally nor contralaterally.ConclusionsDorsal root ganglion stimulation does not induce GABA release from the spinal dorsal horn cells, suggesting that the mechanisms underlying DRGS in pain relief are different from those of conventional SCS. The modulation of a GABA‐mediated “Gate Control” in the DRG itself, functioning as a prime Gate of nociception, is suggested and discussed.

Risk Factors Associated with Lead Migration Requiring Revision in Dorsal Root Ganglion Stimulation

Neuromodulation is an evolving therapy for chronic pain. Aiming to meet the limitations of traditional spinal cord stimulation, dorsal root ganglion (DRG) stimulation targets pain in a dermatomal distribution at the site of pain transmission. Despite these advantages, lead migration is a significant complication that hinders the long-term efficacy of DRG stimulation. This study aims to identify risk factors for lead migration requiring revision in DRG stimulation. We performed a retrospective review of all subjects who had DRG stimulators implanted at T10-S2 by a single physician over a 2-year period. Their history was reviewed for the following: age, sex, diagnosis, lead placement, reported symptom relief, complications, and postoperative activity. In total, 19 cases of DRG stimulator implantation were identified. All patients reported pain relief, with 84.2% (16/19) describing >50% relief. In total, 31.6% of patients (6/19) developed lead migration and 15.8% of total implanted leads (9/57) migrated. Of the migrated leads, 4% (4/9) occurred at S1 and 33.3% (3/9) occurred at L4. The underlying etiology of lead migration was clear and preventable in 66.7% of patients (4/6). All patients who developed lead migration were women. Premature activity, hardware manipulation, and female sex appear to be associated with an increased risk for lead migration. Leads on the S1 and L4 locations may be more likely to migrate. Large trials are necessary to gain a more conclusive understanding of these risk factors for lead migration.

A review of the Senza System: a novel, high frequency 10kHz (HF10), paresthesia free spinal cord stimulator.

This article reviews Nevro Corporation's(CA, USA)Senza System high-frequency spinal cord stimulator(HF10 SCS). HF10 therapy has been shown to be noninferior to traditional low-frequency spinal cord stimulation (SCS), and in some studies, has been shown to have long-term effects that are superior compared with traditional low-frequency SCS in treating both back and leg pain. In addition, safety profiles for the HF10 SCS system wereequivalent to traditional SCS. HF10 SCS is based on spinal anatomic mapping and does not require intraoperative paresthesia mapping for placement, thereby improving procedural experience for patients and reducing operating room time. HF10 SCS has altered the nature of SCS therapy in a manner that treats more individuals with chronic, refractory leg and back pain than in the past, and is widely used in the USA, Europe and Australia.

High-Frequency Spinal Cord Stimulation at 10 kHz for the Treatment of Complex Regional Pain Syndrome: A Case Series of Patients With or Without Previous Spinal Cord Stimulator Implantation.

High-frequency spinal cord stimulation at 10 kHz (HF10-SCS) has been demonstrated to provide enhanced and durable pain relief in patients with chronic back and radiating leg pain. Patients with pain related to complex regional pain syndrome (CRPS) in the chronic stages are commonly challenging to treat and often receive traditional spinal cord stimulation (SCS). Very little information is currently available about the therapeutic outcomes following application of high-frequency stimulation in this cohort of patients. The purpose of the retrospective case series was to report on the initial experience of HF10-SCS in 13 patients with CRPS, some of whom had been exposed to low-frequency SCS. A temporary trial of HF10-SCS was carried out for 1 week, and those achieving a minimum of 50% pain intensity reduction underwent implantation. Successful responders were those who achieved a 50% decrease in pain intensity on subsequent follow-up. Thirteen patients were trialed, 12 of whom went on to receive a permanent implant. Of the patients receiving permanent implants, the responder rate (50% pain relief) was 67% (95% confidence interval [CI] 0.34 to 0.90), with an average follow-up period of 12.1 ± 4.6 months. Of the 5 patients who had sympathetically independent pain, 3 were responders, and of the 7 patients who had sympathetically mediated pain, 5 were responders. There were no adverse events. This small case series suggests that HF10-SCS may be a viable option for patients with CRPS who have chronic intractable pain, including those who had suboptimal results from traditional SCS.

Long-term efficacy of 1–1.2 kHz subthreshold spinal cord stimulation following failed traditional spinal cord stimulation: a retrospective case series

Background and objectiveWe investigated whether an effective long-term pain relief could be achieved using subthreshold 1–1.2 kHz spinal cord stimulation (SCS) among patients who were initially implanted with traditional paresthesia-based...

Retrospective analysis of complications associated with dorsal root ganglion stimulation for pain relief in the FDA MAUDE database.

Dorsal root ganglion stimulation is an emerging therapy in the treatment of chronic pain. Compared with traditional spinal cord stimulation, it allows a discretely targeted stimulation profile and may act via differing mechanisms of action. Despite these advantages, little is known about the complications associated with this new modality. We queried the MAUDE (Manufacturer and User Facility Device Experience) database for all entries named 'Dorsal root ganglion stimulator for pain relief' reported between May 1, 2016 and December 31, 2017. We verified these data through the Office of the Freedom of Information Act at the US Food and Drug Administration. We then eliminated duplicate entries and categorized each complication based on the event description. A secondary analysis was performed to characterize the serious adverse events and the severity of new neurologic symptoms and infections. We identified 979 unique episodes following our process of deduplication. Almost half (47%) of entries were categorized as device-related complications, a quarter (28%) as procedural complications, with the remainder as patient complaints (12%), serious adverse events (2.4%), and 'other' complications (4.6%). The majority of complications were managed surgically with revision (n = 488; 49.8%) rather than explant (n = 161; 16.4%) events, respectively. The 'Dorsal root ganglion stimulator for pain relief' device has been publicized as a breakthrough in neuromodulation technologies. As with any new technology, we must proceed with caution and re-evaluate effectiveness as information becomes available. The MAUDE database has provided safety data unique for this device that will aid in informed consent and further refinement of this innovative therapy.

Dorsal Root Ganglion Stimulation for Chronic Pelvic Pain: A Case Series and Technical Report on a Novel Lead Configuration

Chronic pelvic pain (CPP) is an elusive and complex neuropathic condition that is notoriously recalcitrant to treatment. The term "CPP" encompasses a number of treatment-resistant conditions like pudendal neuralgia, interstitial cystitis, coccygodynia, vulvodynia. CPP has been presented neuromodulators attempting to utilize conventional spinal cord stimulation (SCS), with constant frustration and high explant rates. Contrary to SCS, dorsal root ganglion stimulation (DRGS) delivers targeted target to focal areas, does not rely on paresthesias, and is able to reliably capture body parts like the pelvis making it an ideal modality for the treatment of CPP. We present seven patients with intractable CPP, resistant to conventional treatment methods, all successfully treated with DRGS. The case series includes seven patients with severe, CPP who failed to respond to a variety interventional treatments, and in some cases SCS. All seven patients were successfully trialed with DRGS utilizing leads placed over the bilateral L1 and S2 DRG's-to our knowledge, no publications describing either this particular lead configuration, or utilizing DRG stimulation on CPP, exist. Following treatment, all seven patients experienced significant pain relief as well as reduction in opioid consumption and some cases improvement with sexual function and urination. Four of these patients have been implanted and continue to self-report sustained pain relief with high-satisfaction and functional improvement. To date no explants or instances of loss of efficacy have occurred (>1 year since implant). Like most neuropathic pain states, CPP is resilient, difficult to manage, and typically unresponsive to the traditional therapeutics and SCS. Our case series demonstrates no only that DRGS is potentially effective, long-term treatment modality for CPP, but that the L1/S2 lead placement is the configuration of choice despite distinct differences in etiologies of pain and location.

The influence of High Dose Spinal Cord Stimulation on the descending pain modulatory system in patients with failed back surgery syndrome.

The descending pain modulatory system (DPMS) comprises a network of cortical and subcortical brain and brainstem regions that can inhibit nociceptive afferent brain input (Ossipov et al., 2010; Tracey, 2010; Zhuo and Gebhart, 1997). These pathways seem to be altered in several chronic pain syndromes such as knee osteoarthritis, fibromyalgia, painful diabetic neuropathy and low back pain (Brietzke et al., 2019; da Graca-Tarrago et al., 2019; Kong et al., 2018; Segerdahl et al., 2018). The DPMS network comprises the bilateral anterior insulae (AI), the anterior cingulate cortex (ACC), bilateral middle frontal gyri (mFG), both amygdalae (AMY), the rostral ventromedial medulla (RVM) and the periaqueductal gray (PAG) (Goksan et al., 2018; Schweinhardt and Bushnell, 2010). In the past, it has been suggested that traditional, paresthesia-generating Spinal Cord Stimulation (SCS) induces several changes in modulation circuits located in the cerebrum and brainstem. An inhibitory effect of traditional SCS on somatosensory evoked potentials, and potential mediators like the thalamus and the anterior cingulate cortex (ACC), could play a role in the mechanism of action (MOA) of SCS as well (Bentley et al., 2016; De Ridder and Vanneste, 2016; Moens et al., 2013, 2012). Several studies have provided evidence of the impact of SCS on the DPMS resulting in this inhibitory supraspinal effect (Sankarasubramanian et al., 2018; Schuh-Hofer et al., 2018). More recently, researchers have hypothesized similar influences on the DPMS by other paradigms of SCS such as high frequency SCS at 10 kHz and Burst SCS, as well as by other forms of neurostimulation e.g. occipital nerve field stimulation (Ahmed et al., 2018a, 2018c). Tonic SCS at sub-sensory threshold and at 500 Hz and pulse width 500μsec, so called high density or high dose SCS (HD-SCS), is a SCS form based on the impact of electrical charge delivery to the spinal cord (Chen et al., 2018; Linderoth and Foreman, 2017; Miller et al., 2016; Sweet et al., 2016; Wille et al., 2017). After some initial case series studies, researchers are still exploring the clinical effect and impact on chronic pain of HD-SCS (De Jaeger et al., 2017; Provenzano et al., 2017; Wille et al., 2017). In the past, several researchers have investigated the supraspinal effects of SCS by examining human cerebral circuits via different neuroimaging techniques (e.g. MR Spectroscopy (MRS), single photon emission computerized tomography (SPECT), positron emission tomography (PET), electroencephalography (EEG) and, functional magnetic resonance imaging (fMRI)) to capture alterations in modulation circuits (De Ridder and Vanneste, 2016; Kishima et al., 2010; Moens et al., 2013, 2012; Nagamachi et al., 2006). fMRI is especially interesting due to the robustness and test-retest reliability of the functional connectivity (FC) method in clinical applications (Apkarian, 2015; Shehzad et al., 2009). Additionally, the introduction of MRI-conditioned SCS devices enables further exploration of MOA of SCS, not only during trial period but also on long-term implanted devices. Based on this knowledge, we hypothesized, in this study, that HD-SCS may alter the DPMS and indirectly, might generate an inhibitory supraspinal effect. This hypothesis-driven pilot study aimed to investigate the influence of HD-SCS on FC within the DPMS, measured by resting state fMRI.

Long-term quality of life improvement for chronic intractable back and leg pain patients using spinal cord stimulation: 12-month results from the SENZA-RCT

PurposeChronic axial low-back pain is a debilitating disorder that impacts all aspects of an afflicted individual’s life. Effective, durable treatments have historically been elusive. Interventional therapies, such as spinal cord stimulation (SCS), have shown limited efficacy at best. Recently, a novel treatment, 10 kHz SCS, has demonstrated superior pain relief compared with traditional SCS in a randomized controlled trial (RCT). In this manuscript, we report on the long-term improvements in quality of life (QoL) outcomes for subjects enrolled in this study.MethodsA prospective, multicenter, randomized controlled trial (SENZA-RCT) was conducted. Patients with both chronic back and leg pain were enrolled and randomized (1:1) into 10 kHz SCS or traditional SCS treatment groups. A total of 171 subjects received a permanent SCS device implant. QoL and functionality measures were collected up to 12 months. The device remote control utilization, which is an indication of patient interaction with the device for adjustments, was collected at 24-month post-implantation.ResultsAt 12 months, a higher proportion of 10 kHz SCS subjects had marked improvement of their disability (Oswestry Disability Index) to a “moderate” or “minimal” impact on their daily function versus the control group. The subjects also reported better improvement in the Global Assessment of Functioning, Clinician Global Impression of Change, Pittsburgh Sleep Quality Index, and short-form McGill Pain Questionnaire, compared to traditional SCS subjects. The 10 kHz SCS subjects also reported far higher rates of both driving and sleeping with their device turned on, as well as reduced reliance on their programmers to adjust therapy settings.ConclusionsIn addition to superior pain relief, 10 kHz SCS provides long-term improvements in quality of life and functionality for subjects with chronic low-back and leg pain. Trial registration: ClinicalTrials.gov (NCT01609972).

Selective Radiofrequency Stimulation of the Dorsal Root Ganglion (DRG) as a Method for Predicting Targets for Neuromodulation in Patients With Post Amputation Pain: A Case Series

While spinal cord stimulation (SCS) has established itself as an accepted and validated treatment for neuropathic pain, there are a number of conditions where it has experienced less, long-term success: post amputee pain (PAP) being one of them. Dorsal root ganglion (DRG) stimulation has shown great promise, particularly in conditions where traditional SCS has fallen short. One major difference between DRG stimulation and traditional SCS is the ability to provide focal stimulation over targeted areas. While this may be a contributing factor to its superiority, it can also be a limitation insofar stimulating the wrong DRG(s) can lead to failure. This is particularly relevant in conditions like PAP where neuroplastic maladaptation occurs causing the pain to deviate from expected patterns, thus creating uncertainty and variability in predicting targets for stimulation. We propose selective radiofrequency (RF) stimulation of the DRG as a method for preoperatively predicting targets for neuromodulation in patients with PAP. We present four patients with PAP of the lower extremities. RF stimulation was used to selectively stimulate individual DRG's, creating areas of paresthesias to see which most closely correlated/overlapped with the painful area(s). RF stimulation to the DRG's that resulted in the desirable paresthesia coverage in the residual or the missing limb(s) was recorded as "positive." Trial DRG leads were placed based on the positive RF stimulation findings. In each patient, stimulating one or more DRG(s) produced paresthesias patterns that were contradictory to know dermatomal patterns. Upon completion of a one-week trial all four patients reported 60-90% pain relief, with coverage over the painful areas, and opted for permanent implant. Mapping the DRG via RF stimulation appears to provide improved accuracy for determining lead placement in the setting of PAP where pain patterns are known to deviate from conventional dermatomal mapping.

Dorsal Root Ganglion Stimulation as a Salvage Treatment for Complex Regional Pain Syndrome Refractory to Dorsal Column Spinal Cord Stimulation: A Case Series

The efficacy of traditional spinal cord stimulation (t-SCS) tends to decay over time in patients with complex regional pain syndrome (CRPS). While it has been shown that dorsal root ganglion (DRG) stimulation is extremely effective in t-SCS-naïve patients with CRPS, its efficacy in patients who had previously failed t-SCS is unknown. Given that DRG-SCS and t-SCS target different spinal pathways, a failure with t-SCS should not automatically preclude a patient from attempting DRG-SCS. Two patients with lower extremity CRPS, previously implanted with t-SCS systems, experienced relapses in the pain despite exhaustive reprogramming. Both patients were offered DRG stimulation as a means to salvage treatment. Patient 1 reported 90% pain reduction with significant gait improvement during the DRG stimulation trial. The patient subsequently proceeded to implant and have the t-SCS implantable pulse generator explanted. Patient 2 was unable to undergo a trial with DRG-SCS because of health insurance constraints, so she elected to undergo a surgical revision of her existing system whereby a DRG-SCS system was added to the existing t-SCS to create a hybrid system with two implantable pulse generators. The patient reported an immediate improvement in pain because of the introduction of the DRG-SCS. Additionally, she was instructed to document her pain scores with each system on individually, as well as with both on-her pain scores were at the lowest with the DRG-SCS on by itself. At eight-month follow-up, both patients reported sustained pain improvement and retained their functional gains. Our case series demonstrates that a failure of t-SCS is not necessarily a failure of neurostimulation as a whole. The efficacy of DRG-SCS is independent of prior t-SCS therapy outcomes in these two patients and a history of t-SCS failure serves no predictive value in these two patients for future DRG stimulation success. Therefore, DRG-SCS can be considered as a reasonable next-step to salvage patients with CRPS who had failed other SCS treatments.

The Efficacy of High-Density Spinal Cord Stimulation Among Trial, Implant, and Conversion Patients: A Retrospective Case Series

Methods of energy delivery for traditional spinal cord stimulation (SCS) systems consist of adjusting programming parameters to affect the total charge delivered per unit time. One high electrical charge delivery method being considered is subthreshold high density (HD) programming. To date, there is limited clinical evidence for the efficacy and safety of paresthesia-free HD programming. The aim of this study was to examine the efficacy and safety of HD programming. A retrospective review was performed on HD-programmed SCS patients with a minimum of one year follow-up. Three HD categories were examined: trial, implant, and conversion (i.e., patients with conventional SCS who were converted to HD settings). High density amplitude settings were below paresthesia threshold. Patients were classified as responders to HD if they preferred the paresthesia-free HD setting to the conventional setting and demonstrated ≥50% pain reduction compared to baseline pain score on delivery and no-stimulation related neurological deficit. Adverse effects were documented. Seventeen patients were identified, including 11 conversion patients and six patients who had positive response to HD programming during the trial and then were implanted. For trial/implant and conversion patients, both HD and conventional programming significantly reduced the numerical pain rating scale (NRPS) compared to baseline (p ≤ 0.026). Pain scores were not significantly different between the HD and traditional programs for the trial (p = 0.060), implant (p = 0.632), and conversion categories (p = 0.658). Through at least 12 months of follow-up, eight (47%) patients continued to be HD responders. In subpopulations, HD programming may be a viable option to deliver subthreshold pain reduction. Randomized, controlled trials with extended follow-up are needed to further evaluate HD programming.

Prospective Evaluation of Patient Usage of Above and Below Threshold Waveforms With Traditional Spinal Cord Stimulation Devices

Spinal cord stimulation (SCS) is an efficacious therapy used to treat chronic pain. The type of SCS programming is important in improving patients' quality of life and overall satisfaction. In this study, 19 patients who underwent SCS with traditional devices were given between 4 and 6 programs including programs with stimulation below sensory threshold and above sensory threshold. Usage patterns and preferences were assessed. SCS patients were given 4-6 programs, some above sensory threshold and some below threshold immediately postoperatively after permanent implantation. Usage patterns of different programs were documented, including percent of time that the settings were used and preference for above threshold vs. below threshold settings during sleeping, walking, sitting, and vigorous activity. Improvements at three months in Oswestry disability index (ODI), numeric rating scale (NRS), Beck depression inventory (BDI), McGill pain questionnaire (MPQ), pain catastrophizing scale (PCS), insomnia severity index (ISI), and Epworth sleepiness scale (ESS) were evaluated. Patients were all trialed on above sensory threshold programs. Six weeks after implantation, most patients preferred above threshold stimulation (74%) vs. below threshold waveforms (21%). Patient diagnosis, type/location of lead or recharging burden played no role in patient preference. Above threshold patients had significantly better improvement in BDI scores than did below threshold patients (p < 0.05) at three-month follow-up but also had worse ESS scores (p < 0.05). Above threshold stimulation was preferred for walking and sitting (p < 0.05). Results indicate that when given the option between waveforms inducing paresthesias and those that do not, SCS patients tend to prefer waveforms that induce paresthesias. Among users of above threshold waveforms, there was preference for these settings during walking and sitting. There was a trend for below threshold preference in vigorous activity and sleeping.