A New Target

Dorsal root ganglion (DRG) stimulation is an effective treatment for chronic, refractory complex regional pain syndrome (CRPS). Routinely, the placement of a DRG stimulator lead is based on established anatomical knowledge of dermatomes. In patients with lumbosacral transitional vertebral anatomy, dermatome maps are not dependable due to dermatomal variance. This can make correct placement of stimulator leads challenging as the supposed target may not actually be responsible for sensing the painful area. We present a case of a 60-year-old woman with CRPS and lumbarization of the S1 vertebral body (presence of 6 lumbar vertebrae and 4 sacral vertebrae) who failed a DRG stimulator trial after using conventional dermatome maps to identify target DRGs assuming that the nerve exiting below L6 corresponded to the S1 dermatome. Following the failed trial, sensory stimulation of the DRG via radiofrequency stimulation was used to accurately map dermatomes leading to a successful DRG stimulation implant at a DRG level that differed from expected based on traditional dermatome maps. Thus, DRG stimulation may guide decisionmaking in regard to target stimulation in patients with abnormal vertebral anatomy. Key words: Dorsal root ganglion stimulation, dermatome mapping, radiofrequency stimulation, spinal anomaly, lumbosacral transitional vertebrae, complex regional pain syndrome, neuromodulation, dermatomal variance

Lower urinary tract (LUT) dysfunction arising from injury and disease remain a clinical challenge due to unavailability of pharmacological treatments. Neuromodulation devices developed to tackle these disorders, such as sacral stimulators, are non‐selective for a single nerve with numerous off‐target effects while also stimulating the afferent and efferent population in a nerve. Here, we investigate whether epidural spinal cord stimulation (SCS) and microstimulation of dorsal root ganglion (DRG) through penetrating microarrays, can selectively activate and control reflexes relevant to LUT function. We demonstrate that custom high‐density epidural arrays and Utah arrays in the DRG can selectively access pelvic and pudendal innervation, and can modulate LUT function.To determine the effects of stimulation on peripheral nerve recruitment, α‐chloralose anesthetized male cats (SCS: n=6, DRG: n=4) were instrumented with nerve cuffs on the pelvic nerve as well as the pudendal nerve and its branches. High‐density epidural electrodes were placed corresponding to the lumbosacral (L6 and L7 laminae) and sacral (S1 laminae) spinous processes. In separate DRG experiments, 32‐channel high‐density penetrating Utah arrays were implanted in the S1, S2 and S3 DRG. We stimulated epidurally and within the DRG while recording compound action potentials in nerve cuffs. Functional effects of stimulation were measured using intravesical and transurethral catheters to measure bladder and urethral pressures respectively across various stimulus amplitudes and frequencies.All the instrumented nerves could be selectively recruited with both DRG and SCS stimulation, although not every nerve was selectivity recruited in every animal. The stimulation amplitude to evoke functional responses was higher (SCS: 600–1000 μA, DRG: 20–45 μA) than the minimum threshold to evoke antidromic activity in nerve cuffs. SCS and DRG stimulation both evoked bladder parasympathetic contractions similar to direct stimulation of the pelvic nerve. In several trials, stimulation through the same epidural electrode during cystometry, low frequency (3 Hz) stimulation evoked a continence reflex resulting in a suppression of detrusor activity, while high frequency (33 Hz) stimulation evoked a micturition reflex resulting in high intravesical pressures. Isovolumetric and filling cystometry was performed to confirm the action of these reflexes.SCS and DRG stimulation can selectively activate pelvic and pudendal innervation, and elicit micturition and continence reflexes.Support or Funding InformationR01 NS088184 and OT2OD024908. Craig H. Neilsen Foundation Award 476681

Complex regional pain syndrome (CRPS) is a chronic debilitating multisystem neuropathic pain disorder. It is characterized by continuous pain, usually out of proportion to any known tissue injury, vasomotor changes, sudomotor or edema, and motor or trophic changes. The objective of this study is to assess the efficacy of neuromodulation, interventional, and unconventional treatments for CRPS. The primary focus is pain reduction, assessed through various scales, with secondary outcomes examining effects on autonomic, sensory, motor, and psychological aspects, and quality of life. PubMed, Cochrane Library, MDPI, and ScienceDirect databases were thoroughly searched using our detailed search strategy and relevant literature compiled. Articles were assessed using our eligibility criteria and quality appraisal tools. All types of study designs were considered. Initially, 463 articles were identified; after a thorough assessment, 23 articles comprising 2307 patients were shortlisted. Neuromodulation interventions, specifically Dorsal Root Ganglion (DRG) and Spinal Cord Stimulation (SCS) demonstrated statistically significant pain reduction (43-82% and up to 70%, respectively). Both modalities demonstrate improvement in secondary outcomes and quality of life. Interventional interventions, specifically nerve blockade ranging from sympathetic, stellate ganglion, and regional nerve blocks, all demonstrate varying levels of efficacy on measured pain and secondary outcomes. Unconventional: Botulinum toxin injections through multiple delivery systems demonstrated varying levels of efficacy in treating pain and improving secondary outcomes. In conclusion, DRG stimulation and SCS, nerve blockade, and botulinum toxin all display promise in alleviating symptoms of CRPS. Definite conclusions were not made due to a lack of clinical trial data, and longer multi-year follow-up is recommended.

BACKGROUND: The treatment of complex regional pain syndrome (CRPS) is a difficult endeavor. The advent of neuromodulation interventions has led to new therapeutic options for chronic pain syndromes. Coinciding neuromodulation devices, such as spinal cord stimulation (SCS) and dorsal root ganglion stimulation (DRGS), may have a part in refractory CRPS. CASE REPORT: The authors present a case of a 50-year-old man status post a traumatic skiing accident 3 years prior to presentation with residual CRPS symptoms after an SCS implant. Additional multilevel coverage for refractory chronic neuropathic pain was achieved with the implantation of multiple DRGS devices. DISCUSSION: This case provides support for the use of DRGS in patients needing supplementary neuropathic pain coverage. Outcomes were reflected in diminished pain scores, an enriched quality of life, and enhanced functional capacity measures. KEY WORDS: Complex regional pain syndrome, dorsal root ganglion stimulator, dorsal root ganglion stimulation, neuromodulation, spinal cord stimulator, spinal cord stimulation, chronic pain, case report

Background: Spinal cord stimulation is an intervention that has become increasingly popular due to the growing body of literature showing its effectiveness in treating pain and the reversible nature of the treatment with implant removal. It is currently approved by the FDA for chronic pain of the trunk and limbs, intractable low back pain, leg pain, and pain from failed back surgery syndrome. In Europe, it has additional approval for refractory angina pectoris and peripheral limb ischemia. Objective: This narrative review presents the current evidence supporting the use of spinal cord stimulation for the approved indications and also discusses some emerging neuromodulation technologies that may potentially address pain conditions that traditional spinal cord stimulation has difficulty addressing. Study Design: Narrative review. Results: Spinal cord stimulation has been reported to be superior to conservative medical management and reoperation when dealing with pain from failed back surgery syndrome. It has also demonstrated clinical benefit in complex regional pain syndrome, critical limb ischemia, and refractory angina pectoris. Furthermore, several cost analysis studies have demonstrated that spinal cord stimulation is cost effective for these approved conditions. Despite the lack of a comprehensive mechanism, the technology and the complexity in which spinal cord stimulation is being utilized is growing. Newer devices are targeting axial low back pain and foot pain, areas that have been reported to be more difficult to treat with traditional spinal cord stimulation. Percutaneous hybrid paddle leads, peripheral nerve field stimulation, nerve root stimulation, dorsal root ganglion, and high frequency stimulation are actively being refined to address axial low back pain and foot pain. High frequency stimulation is unique in that it provides paresthesia free analgesia by stimulating beyond the physiologic frequency range. The preliminary results have been mixed and a large randomized control trial is underway to evaluate the future of this technology. Other emerging technologies, including dorsal root ganglion stimulation and hybrid leads, also show some promising preliminary results in non-randomized observational trials. Limitation: This review is a primer and not an exhaustive review for the current evidence supporting the use of spinal cord stimulation and precursory discussion of emerging neuromodulation technologies. This review does not address peripheral nerve stimulation and focuses mainly on spinal cord stimulation and touches on peripheral nerve field stimulation. Conclusions: Spinal cord stimulation has demonstrated clinical efficacy in randomized control trials for the approved indications. In addition, several open label observational studies on peripheral nerve field stimulation, hybrid leads, dorsal root ganglion stimulation, and high frequency stimulation show some promising results. However, large randomized control trials demonstrating clear clinical benefit are needed to gain evidence based support for their use. Key words: Spinal cord stimulation, chronic pain; low back pain, high frequency stimulation, peripheral nerve field stimulation, dorsal root ganglion stimulation, failed back surgery syndrome, complex regional pain syndrome, critical limb ischemia, refractory angina pectoris

Utilization of Concurrent Dorsal Root Ganglion Stimulation and Dorsal Column Spinal Cord Stimulation in Complex Regional Pain Syndrome

Chronic pain affects millions of people in the United States and pharmacological treatments have been ineffective. Dorsal root ganglion (DRG) stimulation is a neuromodulation method that delivers electrical stimulation to the DRG to relieve pain. DRG electrodes are rigid and cylindrical. The implantation of DRG electrodes requires a technically-challenging surgery that involves steering electrodes laterally towards the DRG. The Injectrode is an injectable conductive polymer that cures in place and is capable of delivering electrical current to stimulate neural tissue. We used the Injectrode to stimulate the L6 and L7 DRG in cats, measuring neural responses evoked in the sciatic, tibial, and common peroneal nerves to measure the thresholds for activating fibers. A cylindrical stainless-steel electrode was used for comparison. Thresholds were 38% higher with the Injectrode versus stainless-steel, likely owing to its larger contact surface area with the DRG. Both Aα and Aβ sensory fibers were activated using DRG stimulation. The Injectrode has the potential to offer a new and simple method for DRG stimulation that can potentially offer more complete coverage of the DRG.

Introduction Neuropathic pain is a debilitating and often treatment-resistant condition with significant personal and societal burden. As conventional pharmacologic options frequently fall short, there is a growing need for targeted, durable solutions. Areas covered Dorsal root ganglion (DRG) stimulation has emerged as a promising neuromodulation technique offering anatomically targeted therapy for focal neuropathic syndromes. This review examines the anatomical underpinnings, mechanisms of action, clinical evidence, technological innovations, procedural techniques, and safety considerations associated with DRG stimulation, while highlighting current challenges and future directions in expanding its role within modern pain management. Literature was searched in PubMed/MEDLINE, Embase, Scopus, Web of Science, and Cochrane CENTRAL from 2010 through 2024. This narrative review synthesizes the anatomic rationale, mechanistic hypotheses, clinical evidence by indication, procedural technique, safety considerations, and emerging technological developments in DRG stimulation. Expert opinion DRG stimulation represents a significant advancement in interventional pain medicine. With its dermatomal targeting and clinical efficacy in anatomically discrete pain syndromes, it can be considered as a option in appropriately selected patients. Continued innovation, real-world outcome data, and improved access will be key to realizing its full therapeutic potential.

Dorsal Root Ganglion Stimulation for Chronic Groin Pain: A Review

Objective: Thoracic neuralgia (TN) is a chronic pain syndrome that can be refractory to pharmacologic intervention and management by pain specialists. Dorsal root ganglion (DRG) stimulation has shown promise as a targeted and effective modality compared to traditional therapies for several indications but has not yet been applied in the thoracic region. This study aims to report the outcomes of off-label thoracic DRG stimulation in patients with refractory TN.Methods: A retrospective chart review was performed at Emory University Hospital for patients who underwent thoracic DRG stimulation in a two-year period. Relevant outcomes for safety and efficacy were evaluated.Results: Six patients were identified that underwent thoracic DRG stimulation for various etiologies of TN, including post-mastectomy, post-herpetic, and post-abdominoplasty neuralgia. All patients initially underwent trial DRG stimulation with a mean pre-operative visual analogue scale (VAS) (0-10) of 6.8 ± 1.6 (range: 4-8). Four of six patients (67%) were non-responders and did not pursue permanent implantation; two experienced pain with stimulation during the trial, and two patients experienced no significant benefit. In addition, all three patients with post-herpetic neuralgia did not respond to treatment. Two of six patients (33%) responded well to stimulation, elected to receive permanent leads, and reported significant pain relief with VAS scores of 0/10 and 1/10, and 100% reduction in morphine equivalent use. Complications included lead migration and need to reset stimulator programming.Conclusions: DRG stimulation may be an effective therapy for patients experiencing chronic TN as a result of peripheral nerve injury; however, post-herpetic neuralgia may be unresponsive to this treatment. Future prospective studies are warranted to evaluate the feasibility of this procedure in patients with refractory TN.

Background: Postherpetic neuralgia (PHN) is the most common complication of shingles and can be a significant burden to patients due to pain and disability. Currently, treatment options are limited. In refractory cases, neuromodulation using spinal cord stimulation (SCS) and peripheral nerve stimulation (PNS) have been used but is considered experimental due to limited evidence. Case Report: We report 2 cases who experienced successful treatment of refractory PHN. Patients underwent dorsal root ganglion (DRG) stimulation at the thoracic level for the treatment of refractory PHN. Conclusion: Both patients showed significant improvement in pain at 24 and 36 months after a DRG stimulation trial and implantation. We report the successful use of DRG stimulation for the treatment of PHN. Key words: Knee, genicular, radiofrequency ablation, osteoarthritis, pain, block, cooled

Dorsal Root Ganglion Stimulation as a Salvage Therapy Following Failed Spinal Cord Stimulation

Crohn's disease is a chronic inflammatory bowel condition causing symptoms, notably pain, due to ongoing intestinal inflammation or complications like abscesses, strictures, and fistulas, which are common in IBD patients. Abdominal pain affects up to 60 % of IBD patients, irrespective of disease severity, prompting medical attention. Various medications like NSAIDs, antidepressants, antispasmodics, anticonvulsants, and opioids are used to manage pain, but they have limited effectiveness and potential side effects, even during remission. In this case, a 20-year-old Caucasian female college student [height 5′4″, weight 120lbs (54.4 kg)] with juvenile idiopathic arthritis and Crohn's disease experienced severe daily abdominal pain, negatively impacting her life. Despite a multimodal regimen, including gabapentin, nortriptyline, duloxetine, and acetaminophen, her pain persisted, significantly affecting her appetite, sleep, mood, activity level, and overall quality of life (QOL). To address this, dorsal root ganglion (DRG) stimulation was considered. The patient aimed for a 20 % pain reduction and improved QOL. Trial leads were placed along the T10 and T12 DRG, resulting in a 25 % pain reduction (8–6 out of 10) and substantial QOL improvement. She could eat, sleep without interruptions, walk longer distances, and be more active. The T12 lead was more effective than the T10, targeting upper abdomen stimulation. The patient and her mother were highly satisfied and opted for permanent implantation for the T11 and T12 DRG. While DRG stimulation was approved in 2016 for chronic pain, to our knowledge, this is the first reported case of its use in a patient with debilitating Crohn's disease.

ID: 200814 Open Dorsal Root Ganglion Stimulator Lead Placement in the Setting of Previous Fusion: Case Report

Management of complex regional pain syndrome of the hand