Faculty Bibliography

OBJECTIVE:Dorsal root ganglion stimulation (DRG-S) is a novel therapy to treat chronic pain. It has shown efficacy when delivered intermittently, suggesting a delayed washout effect exists. To measure the washout period, and to determine whether there are differences in washout times among different types of treated pain, we measured the time for pain to return at the end of the patients' one-week DRG stimulation trials. MATERIALS AND METHODS/METHODS:Patients who completed a successful DRG-S trial were included. The times until 25% (t25) and 90% (t90) of baseline pain level returned were recorded. The patients were divided into neuropathic, nociceptive, and mixed pain groups for subgroup comparison. t25 and t90 were plotted in the entire cohort and subgroups using reverse Kaplan-Meier plots (failure curves) and compared using a log-rank test. RESULTS:In total, 29 consecutive patients were included. Median t25 and t90 times were 7.1 and 19.5 hours, respectively. Median (interquartile range) times were longest for the nociceptive pain group (n = 17) and shortest for the neuropathic pain group (n = 6), with the mixed-pain group (n = 6) in between (t25: 7.1 [1.7-19.4], 3.40 [1.4-8.4], and 5.7 [0.8-17.6]; t90, 22.0 [10.7-71.0], 7.6 [3.6-19.8], and 20.9 [14.2-31.2], respectively). t90 times differed significantly by pain type (p = 0.040). CONCLUSIONS:This study showed a prolonged washout period after cessation of DRG-S therapy. Washout times vary according to pain type. The observed effects are possibly due to long-term depression of pain signaling and could allow the implementation of alternative stimulation strategies with DRG-S. Further investigations evaluating DRG-S washout times are warranted.

INTRODUCTION/BACKGROUND:Chronic discogenic low back pain (CD-LBP) is caused by degenerated disks marked by neural and vascular ingrowth. Spinal cord stimulation (SCS) has been shown to be effective for pain relief in patients who are not responsive to conventional treatments. Previously, the pain-relieving effect of two variations of SCS has been evaluated in CD-LBP: Burst SCS and L2 dorsal root ganglion stimulation (DRGS). The aim of this study is to compare the effectivity in pain relief and pain experience of Burst SCS with that of conventional L2 DRGS in patients with CD-LBP. MATERIALS AND METHODS/METHODS:Subjects were implanted with either Burst SCS (n = 14) or L2 DRGS with conventional stimulation (n = 15). Patients completed the numeric pain rating score (NRS) for back pain and Oswestry disability index (ODI) and EuroQoL 5D (EQ-5D) questionnaires at baseline, and at three, six, and 12 months after implantation. Data were compared between time points and between groups. RESULTS:Both Burst SCS and L2 DRGS significantly decreased NRS, ODI, and EQ-5D scores as compared with baseline. L2 DRGS resulted in significantly lower NRS scores at 12 months and significantly increased EQ-5D scores at six and 12 months. CONCLUSIONS:Both L2 DRGS and Burst SCS resulted in reduction of pain and disability, and increased quality of life in patients with CD-LBP. L2 DRGS provided significantly increased pain relief and improvement in quality of life when compared with Burst SCS. CLINICAL TRIAL REGISTRATION/BACKGROUND:The clinical trial registration numbers for the study are NCT03958604 and NL54405.091.15.

BACKGROUND:Lead anchoring has previously been shown to reduce the rate of dorsal root ganglion stimulation (DRG-S) lead migration. The aim of this study was to assess longer-term follow-up and consistency of lead migration prevention with lead anchoring in a new cohort of patients. METHODS:We performed a retrospective chart review from September 2017 to November 2022 of all patients who had DRG-S implants at our institute to identify the number of lead migrations that occurred over this period. The first cohort consisted of patients reported on in a previous publication (implanted from September 2017 through September 2020) subdivided into unanchored or anchored lead groups. The second cohort consisted of patients implanted during or after October 2020 who were not previously reported on for whom leads were anchored using silastic anchoring only. RESULTS:At the November 2022 data cutoff, in the initial cohort, 8 migrations had occurred in unanchored leads over an average follow-up of 49 months, equating to a migration rate of 9.1% per lead. Patients with anchored leads in the initial cohort experienced 2 migrations over an average follow-up of 38 months (0.7% migration rate per lead). There were no new lead migrations in these groups over the extended follow-up reported here. The migration rate in the new cohort was similar, with 1 migration over an average follow-up of 13 months (0.5% migration rate per lead). CONCLUSION/CONCLUSIONS:These results underscore the necessity of anchor placement during DRG-S lead implantation to prevent lead migration.

A 67-year-old man presented with severe 9 of 10 intractable pain of the left shoulder joint after arthroplasty and revision surgeries, with associated weakness, atrophy, and limited range of motion in all directions. Dorsal root ganglion stimulation (DRG-S) at the left C4, C5, and C6 levels was used after failed conservative and interventional measures, resulting in significant improvement in pain, function, and quality of life measures through 6 months postimplantation. Larger studies should examine if DRG-S is effective in treating chronic arthritic joint pain as well as chronic postsurgical pain of the shoulder that is not predominantly neuropathic.

INTRODUCTION/BACKGROUND:Dorsal root ganglion stimulation (DRG-S) has recently emerged as a novel therapy in neuromodulation that demonstrated a higher rate of success than spinal cord stimulation (SCS) in a prospective, head-to-head randomized comparative trial to treat complex regional pain syndrome (CRPS) and causalgia. In contrast to SCS, DRG-S also shows promise in treating conditions that are not purely neuropathic such as axial low back pain, which has a prominent nociplastic pain component. It is not known to what extent the effectiveness of DRG-S for such indications is due to effective treatment of the neuropathic pain component versus effects from DRG-S on mechanical pain. Although rarely studied, reporting outcomes of DRG-S to treat predominantly mechanical/nociceptive pain may help point towards expanding the utility of this therapy. Here, we present 5 cases of refractory mechanical pain treated with DRG-S. METHODS:A retrospective analysis of all patients that underwent a successful DRG-S trial and implant between September 2017 and September 2021 at our institute was performed. Patients who had intractable joint pain without strong evidence of neuropathic pain were included in this case series. The Budapest criteria for CRPS, the Douleur Neuropathique 4 Questions (DN4) survey, or a definable nerve injury were used to determine the presence of neuropathic pain. Baseline assessments for pain (Numeric Rating Scale [NRS]), function (Oswestry Disability Index [ODI]), quality of life (EuroQol-5 Dimension [EQ-5D]), and other applicable joint surveys were extracted from pre-trial baseline and from follow-up appointments. RESULTS:Five patients were identified and included. Patient diagnoses consisted of refractory joint pain of the hip, knee, or ankle. Mean NRS pain scores improved by 74% from 9.2 at baseline to 2.4 at last follow up (mean = 28 months post-implant). From baseline to last follow-up, mean ODI scores improved by 65% from 66 to 23 and EQ-5D scores more than doubled from an average of 0.371 to 0.797. CONCLUSION/CONCLUSIONS:This clinical report illustrates the potential utility DRG-S has in treating pain that clinically presents as predominantly refractory mechanical joint pain without a significant neuropathic component. The physiological reasons for our observations may be that DRG-S is able to directly influence conduction of nociceptive signaling at the DRG and within the spinal cord. Further investigations are warranted to determine if DRG-S is a potential treatment option for chronic mechanical pain.

INTRODUCTION/BACKGROUND:Chronic discogenic low back pain (CD-LBP) is caused by degeneration of the disc due to trauma to the annulus or by unprovoked degeneration, resulting in chronic pain. Spinal cord stimulation (SCS) employing the BurstDR™ waveform has been shown to be an effective treatment in a variety of chronic pain conditions. The aim of this prospective case study was to determine the effect of BurstDR™ SCS on pain relief, disability, and patient satisfaction in a population with CD-LBP. METHODS:Seventeen subjects with CD-LBP received a SCS trial with BurstDR™ stimulation. Patients with >50% pain relief after a trial period of 2 weeks were permanently implanted (n = 15). Patients then rated LBP and leg pain using the numeric rating scale (NRS), Oswestry disability index (ODI), patient global impression of change (PGIC), EQ-5D quality of life, and painDETECT for neuropathic pain at baseline following trial, 3, 6, and 12 months after permanent implantation. RESULTS:Treatment with BurstDR™ SCS resulted in significant reduction of LBP as the NRS was reduced from 71.7 ± 7.3 at baseline to 42.5 ± 18.1 at 12 months. Average pain relief at 12 months was 42.5%. In patients with leg pain (n = 8), pain was significantly reduced from 66.9 ± 8.2 to 11.7 ± 10.4 at 12 months. PainDETECT scores for neuropathic pain significantly reduced from 18.9 ± 4.8 at baseline, and 14.8 ± 3.2 at 12 months. Baseline ODI score significantly reduced from 41.2 ± 12.8 to 25.8 ± 8.6 at 12 months. PGIC scores remained low from 2.6 ± 1.6 at 3 months, 2.5 ± 1.0 at 6 months, and 2.5 ± 1.3 at 12 months. EQ-5D-5L rates remained constant from baseline 56.10 ± 23.9 to 68.6 ± 12.9 at 12 months. CONCLUSION/CONCLUSIONS:BurstDR™ SCS resulted in significant reduction of back pain, leg pain, and quality of life in patients with CD-LBP and decreased the level of disability and generated positive patient satisfaction scores.

With continued innovations in neuromodulation comes the need for evolving reviews of best practices. Dorsal root ganglion stimulation (DRG-S) has significantly improved the treatment of complex regional pain syndrome (CRPS), and it has broad applicability across a wide range of other conditions. Through funding and organizational leadership by the American Society for Pain and Neuroscience (ASPN), this best practices consensus document has been developed for the selection, implantation, and use of DRG stimulation for the treatment of chronic pain syndromes. This document is composed of a comprehensive narrative literature review that has been performed regarding the role of the DRG in chronic pain and the clinical evidence for DRG-S as a treatment for multiple pain etiologies. Best practice recommendations encompass safety management, implantation techniques, and mitigation of the potential complications reported in the literature. Looking to the future of neuromodulation, DRG-S holds promise as a robust intervention for otherwise intractable pain.

INTRODUCTION/BACKGROUND:Dorsal root ganglion stimulation (DRG-S) is a form of neuromodulation used to treat chronic pain. A spinal cord stimulation (SCS) method with paresthesia-free waveform used in the dorsal columns, burst-SCS, recently demonstrated efficacy using intermittent stimulation, where stimulation is cycled on and off for set durations. Tonic SCS is a paresthesia-based therapy that is ineffective at sub-perception levels and when delivered in a cycled manner. DRG-S also uses a tonic waveform, yet unlike tonic SCS, it is effective at sub-perception levels. This study aimed to determine whether the cycling of stimulation at the DRG could maintain DRG-S efficacy. MATERIALS AND METHODS/METHODS:This study followed a prospective, randomized, and balanced, double-blinded (assessor) protocol. Twenty DRG-S responders were randomized to a sequence of three programs for consecutive two-week intervals: continuous stimulation; 1 minute on:1 minute off; or 1 minute on:2 minutes off. The primary outcome of this study was change in pain ratings with the cycled programs compared with continuous stimulation. Secondary outcomes included changes in function and scores for quality of life, and stimulation program preference. RESULTS:Mean scores were similar at the end of each two-week stimulation program for Numerical Rating Scale pain (continuous = 2.9 ± 0.8, 1:1 on-off = 2.6 ± 0.7, and 1:2 on-off = 2.7 ± 0.7 cm, p = 0.39), disability (p = 0.72), and general health (p = 0.95). No clinically significant differences were found from the upper boundaries of the 95% confidence intervals of the mean difference in pain, disability, and general health for each intermittent stimulation program vs the continuous program. At the end of the study, the continuous stimulation, 1:1 on-off dosing, and 1:2 on-off dosing programs were preferred by a similar number of patients. CONCLUSIONS:Intermittent DRG-S produces comparable results to continuous stimulation over a two-week period. Intermittent delivery may extend battery life and facilitate a smaller implantable pulse generator.

INTRODUCTION/BACKGROUND:Spinal cord stimulation (SCS) can provide long-term pain relief for various chronic pain conditions, but some patients have no relief with trial stimulation or lose efficacy over time. To "salvage" relief in patients who do not respond or have lost efficacy, alternative stimulation paradigms or anatomical targets can be considered. Dorsal root ganglion stimulation (DRG-S) has a different mechanism of action and anatomical target than SCS. OBJECTIVES/OBJECTIVE:We assessed DRG-S salvage therapy outcomes in patients who did not respond to SCS or had lost SCS efficacy. MATERIALS AND METHODS/METHODS:We retrospectively included consecutive patients from 2016 to 2020 who were salvaged with DRG-S after failed SCS trials (<50% pain reduction) or who had lost efficacy after permanent SCS. We compared numerical rating scale (NRS) pain, Oswestry disability index (ODI), health-related quality of life (EuroQol five-dimensions five-level), and oral morphine equivalent (OME) opioid requirements before DRG-S salvage and at patients' last follow-up. RESULTS:A total of 60 patients who had failed SCS were salvaged with DRG-S. The mean age was 56 ± 12 years, and the most common diagnoses were complex regional pain syndrome (n = 24) and failed back surgery syndrome (n = 24). The most common failed modalities included tonic (n = 32), Burst (n = 18), and high-frequency (n = 10) SCS. The median follow-up duration of salvage DRG-S was 34 months. With DRG-S, NRS decreased (8.7 ± 1.2 to 3.8 ± 2.1), and OME declined (median 23 mg to median 15 mg), whereas EuroQol 5D scores increased (0.40 ± 0.15 to 0.71 ± 0.15), and ODI improved (64 ± 14% to 31 ± 18%) (all p < 0.05). CONCLUSIONS:DRG-S can be used in patients with chronic pain who have previously failed to receive persistent benefit from SCS.