Spinal cord stimulation in chronic neuropathic pain: mechanisms of action, new locations, new paradigms

Diabetic peripheral neuropathy and neuromodulation techniques: a systematic review of progress and prospects

Neuromodulation for diabetic peripheral neuropathy represents a significant area of interest in the management of chronic pain associated with this condition. Diabetic peripheral neuropathy, a common complication of diabetes, is characterized by nerve damage due to high blood sugar levels that lead to symptoms, such as pain, tingling, and numbness, primarily in the hands and feet. The aim of this systematic review was to evaluate the efficacy of neuromodulatory techniques as potential therapeutic interventions for patients with diabetic peripheral neuropathy, while also examining recent developments in this domain. The investigation encompassed an array of neuromodulation methods, including frequency rhythmic electrical modulated systems, dorsal root ganglion stimulation, and spinal cord stimulation. This systematic review suggests that neuromodulatory techniques may be useful in the treatment of diabetic peripheral neuropathy. Understanding the advantages of these treatments will enable physicians and other healthcare providers to offer additional options for patients with symptoms refractory to standard pharmacologic treatments. Through these efforts, we may improve quality of life and increase functional capacity in patients suffering from complications related to diabetic neuropathy.

Spatiotemporal activation of lumbar sensorimotor networks

Spinal cord injury (SCI) research is primarily conducted using rodent models, which has resulted in significant advances, including novel treatment strategies that promote recovery. Unfortunately, many of these treatments do not have the same efficacy once translated to human clinical trials. Large animal models, such as Yucatan miniature pigs (minipigs), may provide a superior alternative to translating findings to human clinical trials due to their anatomical similarities to humans. However, porcine models are not widely used, which may be due in part to our inadequate understanding of the functional architecture of neural networks in the minipig spinal cord. This study utilized a clinical-grade epidural paddle array implanted over the lumbosacral enlargement of four minipigs. We then mapped the topographical distribution of spinally evoked motor potentials recorded in hindlimb muscles and cord dorsum potentials evoked by sub-motor threshold tibial nerve stimulation. Spatial correlation analysis suggests the motor networks and sensory networks innervated by the tibial nerve are distinct and separate within the minipig lumbosacral spinal cord. Our findings provide foundational knowledge on sensorimotor networks that are functionally diffused among the lumbar enlargement and possess distinct spatiotemporal patterns of activation along the cord for control of motor output and the processing of sensory input. The results reveal critical insights about the variability of electrophysiological measures across animals, offering a foundation for more individualized approaches in future studies. Furthermore, we demonstrate that using an epidural paddle array to map motor responses is a clinically feasible method, though our results highlight the subject-specific nature of these maps and their sensitivity to paddle location and orientation.

Spinal cord stimulation using time-dynamic pulses achieves longer reversal of allodynia compared to tonic pulses in a rat model of neuropathic pain

Background

Spinal cord stimulation (SCS) utilizing time-dynamic pulses (TDPs) is an emergent field of neuromodulation that continuously and automatically modulates pulse parameters. We previously demonstrated that TDPs delivered for 60 min at paresthesia-free or minimal paresthesia amplitudes significantly reversed allodynia in a rat model of neuropathic pain. Because the anti-allodynic effect was observed to persist post-stimulation, we hypothesized that the anti-nociceptive effects of TDPs may persist longer than those of tonic stimulation.

Methods

We extended SCS stimulation period up to 90 min and investigated the temporal dynamics of SCS-induced analgesia through PWT analysis of the aggregated data from both cohorts.

Results

Both TDPs and tonic stimulation reversed paw withdrawal thresholds (PWT) to near pre-neuropathic levels within 30 min. Most TDPs exhibited significantly slower ramp-up slope (analgesia 'wash-in' rates) as compared to tonic stimulation. All TDPs showed slower wind-down slopes (analgesia 'wash-out' rates) compared to tonic, with pulse width modulation reaching significance. Extending SCS from 60 to 90 min revealed that all TDPs maintained analgesic efficacy longer than tonic stimulation, which showed significant decrease at both 75 and 90 min.

Discussion

Although TDPs and tonic stimulation comparably mitigated allodynia, TDPs exhibited slower rate of wash-out, suggesting longer-lasting analgesic effects and potentially different mechanisms of action.

Chronic, Battery-Free, Fully Implantable Multimodal Spinal Cord Stimulator for Pain Modulation in Small Animal Models

Spinal cord stimulation (SCS) for chronic pain management is an invasive therapy involving surgical implantation of electrodes into spinal epidural space. While the clinical value and mechanistic action of the therapy is debated considerably in recent years, preclinical chronic studies employing rodent models can provide invaluable insights regarding the balance between efficacy and complications as well as mechanistic understanding of SCS therapy. However, current rodent compatible devices require tethered power delivery or bulky batteries, severely limiting the ability to probe long-term efficacy of SCS therapy. This work introduces a tether-free, small-footprint, fully implantable, battery-free SCS device compatible with rodent models, capable of delivering electrical stimulation to the spinal cord at a wide range of frequency, amplitude, and period via wireless communication adjustable on-demand without direct interaction with the animal. The presented device features capabilities of clinical SCS devices, with materials and processes amendable to scalable fabrication at a cost suitable for one-time use enabling high N studies. In this proof of concept, the implantable device serves to assess therapeutic efficacy of various clinically relevant SCS paradigms in alleviating neuropathic pain. This technology offers chronic stability and the potential to serve as the foundation for future research into the development of SCS therapeutic systems.

Evaluating the anti-neuropathic effects of the thymol-loaded nanofibrous scaffold in a rat model of spinal cord injury

Background

Spinal cord injury (SCI) is a debilitating condition characterized by partial or complete loss of motor and sensory function caused by mechanical trauma to the spinal cord. Novel therapeutic approaches are continuously explored to enhance spinal cord regeneration and functional recovery.

Purpose

In this study, we investigated the efficacy of the poly(vinyl alcohol) and chitosan (PVA/CS) scaffold loaded with different thymol concentrations (5, 10, and 15 wt%) in a rat compression model for SCI treatment compare to other (e.g., thymol and scaffold) control groups.

Results and discussion

The thymol-loaded scaffold exhibited a smooth surface and a three-dimensional nanofibrous structure with nanoscale diameter. The conducted analyses verified the successful incorporation of thymol into the scaffold and its high water absorption, porosity, and wettability attributes. Behavioral assessment of functional recovery showed improving sensory and locomotor impairment. Furthermore, histopathological examinations indicated the regenerative potential of the thymol-loaded nanofiber scaffold, by neuronal survival.

Conclusion

Therefore, these findings suggest that the thymol-loaded nanofibrous scaffolds have promising pharmacological activities for alleviating neuropathic pain and addressing complications induced by SCI.

Low intensity trans-spinal focused ultrasound reduces mechanical sensitivity and suppresses spinal microglia activation in rats with chronic constriction injury

Low intensity, trans-spinal focused ultrasound (tsFUS) is a noninvasive neuromodulation approach that has been shown to modulate spinal circuit excitability in healthy rats. Here, we evaluated the potential of tsFUS for alleviating neuropathic pain by testing it in a chronic constriction injury (CCI) model. Male rats underwent CCI of the left sciatic nerve and then received tsFUS (2 kHz pulse repetition frequency; 40% duty cycle) or sham stimulation, targeted at spinal segment level L5 for 3 min daily over three days. As expected, CCI causes significant reduction of von Frey Threshold (vFT), a measure of mechanical sensitivity. We found that tsFUS treatment is associated with increased vFT compared to sham; this increase persists beyond the duration of treatment, through days 4 to 23 post-CCI. In spinal cords of tsFUS-treated animals, counts of spinal microglia (Iba1 + cells) and of activated, pro-inflammatory microglia (Iba1 + /CD86 + cells), are reduced compared to sham-treated animals. This reduction in microglia counts is limited to the insonified side of the spinal cord, ipsilateral to CCI. These findings suggest that tsFUS may be a promising approach for treatment of neuropathic pain at early stages, possibly by attenuating the development of microglial-driven inflammation.

Focus on P2X7R in microglia: its mechanism of action and therapeutic prospects in various neuropathic pain models

Neuropathic pain (NP) is a common symptom of many diseases and is caused by direct or indirect damage to the nervous system. Tricyclic antidepressants and serotonin-norepinephrine reuptake inhibitors are typical drugs used in clinical practice to suppress pain. However, these drugs have drawbacks, including a short duration of action, a limited analgesic effect, and possible dependence and side effects. Therefore, developing more effective NP treatment strategies has become a priority in medical research and has attracted much research attention. P2X7 receptor (P2X7R) is a non-selective cation channel activated by adenosine triphosphate and is mainly expressed in microglia in the central nervous system. Microglial P2X7R plays an important role in pain regulation, suggesting that it could be a potential target for drug development. This review comprehensively and objectively discussed the latest research progress of P2X7R, including its structural characteristics, functional properties, relationship with microglial activation and polarization, mechanism of action, and potential therapeutic strategies in multiple NP models. This study aimed to provide in-depth insights into the association between P2X7R and NP and explore the mechanism of action of P2X7R in the pathological process of NP and the translational potential and clinical application prospects of P2X7R antagonists in pain treatment, providing a scientific basis for the precise treatment of NP.

Progress on Direct Regulation of Systemic Immunity by the Central Nervous System

This article reviews the research progress on the direct regulation of the immune system by the central nervous system (CNS). The traditional "neuro-endocrine-immune" network model has confirmed the close connection between the CNS and the immune system. However, due to the complex mediating role of the endocrine system, its application in clinical treatment is limited. In recent years, the direct regulation of the peripheral immune system through the CNS has provided new methods for the clinical treatment of neuroimmune-related diseases. This article analyzes the changes in the peripheral immune system after CNS injury and summarizes the effects of various stimulation methods, including transcranial magnetic stimulation, transcranial electrical stimulation, deep brain stimulation, spinal cord stimulation, and vagus nerve stimulation, on the peripheral immune system. Additionally, it explores the clinical research progress and future development directions of these stimulation methods. It is proposed that these neural regulation techniques exhibit positive effects in reducing peripheral inflammation, protecting immune cells and organ functions, and improving immunosuppressive states, providing new perspectives and therapeutic potential for the treatment of immune-related diseases.

Prophylactic Fibrin Glue Application for Immediate Management of Dural Puncture during Spinal Cord Stimulation Lead Placement: a Simple and Effective Technique

BACKGROUND

Accidental dural puncture during epidural lead insertion for Spinal Cord Stimulation (SCS) is a recognized surgical complication that may lead to cerebrospinal fluid (CSF) leakage and subsequent postdural puncture headache (PDPH). The optimal technical approach to prevent CSF leakage remains controversial. This study aimed to evaluate a simple and efficient intraoperative technique for managing accidental dural puncture during SCS lead placement.

MATERIALS AND METHODS

A retrospective review was conducted of the medical records and imaging studies of all patients who underwent SCS procedures between January 2020 and April 2024. Signs or symptoms associated with dural puncture were recorded, including subcutaneous fluid collections, pseudomeningocele formation, PDPH, wound infection, and meningitis.

RESULTS

Among 107 patients who underwent SCS implantation, involving a total of 194 lead insertions, 4 cases (3.7%) of intraoperative CSF leakage due to iatrogenic dural puncture were identified. Each case was managed by injecting fibrin glue through the introducer needle into the epidural space, directly over the dural lesion.

CONCLUSIONS

Prophylactic application of fibrin glue following dural puncture appears to be highly effective in sealing the damage and preventing CSF leakage. This technique offers a valuable intraoperative solution for surgeons to immediately address dural injuries during SCS lead placement, potentially minimizing postoperative complications and improving patient outcomes.

Twelve-Month Clinical Trial Results of a Novel, Dorsal Horn Dendrite Stimulation Waveform for Chronic Neuropathic Low Back Pain

OBJECTIVES

The aim of this study was to evaluate the effectiveness and safety of a novel subperception spinal cord stimulation (SCS) waveform paradigm designed to target the dorsal horn dendrites for treating chronic neuropathic low back pain (LBP). The final 12-month results are reported here.

MATERIALS AND METHODS

Twenty-seven participants were implanted with a commercial SCS system. Devices were programmed to deliver the waveform (frequency 100 Hz, pulse width 1000 μsec, T9-T10 disk bipole) at decreasing stimulation perception threshold amplitudes (80%, 60%, then 40%) over a 14-week period. Participants were blinded to the program settings. Participants then received their preferred program for further evaluation at 26 and 52 weeks after activation. Outcome measures included back pain score (visual analogue scale [VAS]), Brief Pain Inventory (BPI), EuroQol 5-Dimension 5-Level (EQ-5D-5L), 36-Item Short Form Health Survey (SF-36), treatment satisfaction, and clinician global impression of change (CGIC).

RESULTS

At 52 weeks (n = 24), the responder rate (≥50% pain relief) was 65.6%, and the high-responder rate (≥80% pain relief) was 56.5%. The mean change from baseline in pain VAS was -43.94 mm (95% CI -57.89, -30.00; p < 0.001) and mean pain relief was 64.69% ± 39.43%. BPI and SF-36 scores remained significantly improved (p ≤ 0.001). EQ-5D-5L index and EuroQoL-VAS further improved, and 87.0% of participants met the minimum clinically important difference for the EQ-5D-5L index. Treatment satisfaction was 83%, and 91% of participants had a CGIC rating of "much improved" or above. No serious study-related adverse events were reported.

CONCLUSIONS

The 12-month trial results show sustained improvements in pain, quality of life, and health-related outcomes. This novel subperception dorsal horn dendrite SCS approach seems a safe and promising treatment option for patients with chronic neuropathic LBP. The open-source availability of this waveform on commercial SCS platforms allows widespread patient access. Further evaluation seems warranted.

CLINICAL TRIAL REGISTRATION

The Clinicaltrials.gov registration number for the study is ACTRN12618000647235 (anzctr.org.au).

Establishing an Electrophysiological Recording Platform for Epidural Spinal Cord Stimulation in Neuropathic Pain Rats

Purpose

Spinal cord stimulation (SCS) is pivotal in treating chronic intractable pain. To elucidate the mechanism of action among conventional and current novel types of SCSs, a stable and reliable electrophysiology model in the consensus animals to mimic human SCS treatment is essential. We have recently developed a new in vivo implantable pulsed-ultrahigh-frequency (pUHF) SCS platform for conducting behavioral and electrophysiological studies in rats. However, some technical details were not fully understood. This study comprehensively analyzed methodology and technical challenges and pitfalls encountered during the development and implementation of this model.

Materials and Methods

Employing a newly developed pUHF-SCS (±3 V, 2 Hz pulses with 500-kHz biphasic radiofrequency sinewaves), we assessed analgesic effect and changes of evoked local field potentials (eLFPs) in the bilateral primary somatosensory and anterior cingulate cortices in the rats with or without spared nerve injury (SNI) using the platform. The placement of stimulating needle electrodes in the hind paw was examined and optimized for functionality.

Results

SNI enhanced the C component of eLFPs in bilateral cortexes elicited by stimulating the contralateral but not the ipsilateral lateral aspect of the hind paw. Repeated pUHF-SCS significantly reversed SNI-induced paw hypersensitivity and reduced C-component enhancement. An impedance test can determine an optimal SCS electrode function: an SCS discharge threshold of 100-400 μA for cortical activation or a motor threshold of 150-600 μA for the hind limbs. Impedance increased due to growth of fibrotic tissue but stabilized after post-implantation day 12.

Conclusion

We presented a reliable electrophysiological platform for SCS application in rat neuropathic pain model and demonstrated potent analgesic effects of pUHF-SCS. All device implantations or pUHF-SCS per se did not cause evident spinal cord damage. This safe and stable platform provides an in vivo rat model for SCS investigation of mechanisms of action and device innovation.

Effects of Spinal Cord Stimulation in Patients with Small Fiber and Associated Comorbidities from Neuropathy After Multiple Etiologies

Objectives: The aim of this study was to evaluate the effects of spinal cord stimulation (SCS) on pain, neuropathic symptoms, and other health-related metrics in patients with chronic painful peripheral neuropathy (PN) from multiple etiologies. Methods: A prospective single center observational longitudinal cohort study assessed SCS efficacy from April 2023 to May 2024, with follow-ups at 2, 4, 6, and 12 months in 19 patients suffering from the painful polyneuropathy of diverse etiologies: diabetic (DPN), idiopathic (CIAP), chemotherapy-induced (CIPN), and others. Patients were implanted with a neurostimulator (WaveWriter AlphaTM, Boston Scientific Corporation, Valencia, CA, USA) and percutaneous leads targeting the lower limbs (T10-T11) and, if necessary, the upper limbs (C4-C7). Stimulation programming was individualized based on patient preference and best response. Assessments were performed before and after implantation and included pain intensity (VAS and DN4), neuropathic pain symptoms (NPSI and SF-MPQ-2), autonomic symptoms (SFN-SIQ and SAS), sensory and small fiber nerve injury (UENS), functionality (GAF), sleep (CPSI), global impression of change (CGI and PGI), and quality of life (EQ-VAS and EQ-5D). Intra-epidermal nerve fiber density (IENFD) via skin biopsy was also performed at baseline (diagnostic) and after 12 months to assess potential small fiber re-growth. Statistical analyses were conducted to determine the evolution of treatment success. Results: To date, 19 patients have undergone implantation and completed follow-up. SCS produced a significant consistent and sustained improvement in pain intensity by 49% in DN4 and 76% in VAS, in neuropathic pain symptoms by 73%, in autonomic symptoms by 26-30%, in the sensorimotor physical exam by 8%, in functionality by 44%, in sleep by 74%, and in quality of life (69% for EQ-VAS and 134% EQ-5D). Both clinicians and patients had a meaningful global impression of change, at 1.1 and 1.3, respectively. Distal intra-epidermal nerve fiber density improved by 22% at 12 months while proximal intra-epidermal nerve fiber density decreased by 18%. Conclusions: SCS is an effective therapy for managing various types of PN.

A novel approach to completely alleviate peripheral neuropathic pain in human patients: insights from preclinical data

Neuropathic pain is a pervasive health concern worldwide, posing significant challenges to both clinicians and neuroscientists. While acute pain serves as a warning signal for potential tissue damage, neuropathic pain represents a chronic pathological condition resulting from injury or disease affecting sensory pathways of the nervous system. Neuropathic pain is characterized by long-lasting ipsilateral hyperalgesia (increased sensitivity to pain), allodynia (pain sensation in response to stimuli that are not normally painful), and spontaneous unprovoked pain. Current treatments for neuropathic pain are generally inadequate, and prevention remains elusive. In this review, we provide an overview of current treatments, their limitations, and a discussion on the potential of capsaicin and its analog, resiniferatoxin (RTX), for complete alleviation of nerve injury-induced neuropathic pain. In an animal model of neuropathic pain where the fifth lumbar (L5) spinal nerve is unilaterally ligated and cut, resulting in ipsilateral hyperalgesia, allodynia, and spontaneous pain akin to human neuropathic pain. The application of capsaicin or RTX to the adjacent uninjured L3 and L4 nerves completely alleviated and prevented mechanical and thermal hyperalgesia following the L5 nerve injury. The effects of this treatment were specific to unmyelinated fibers (responsible for pain sensation), while thick myelinated nerve fibers (responsible for touch and mechanoreceptor sensations) remained intact. Here, we propose to translate these promising preclinical results into effective therapeutic interventions in humans by direct application of capsaicin or RTX to adjacent uninjured nerves in patients who suffer from neuropathic pain due to peripheral nerve injury, following surgical interventions, diabetic neuropathy, trauma, vertebral disc herniation, nerve entrapment, ischemia, postherpetic lesion, and spinal cord injury.

Comparative outcomes of microsurgical dorsal root entry zone lesioning (DREZotomy) for intractable neuropathic pain in spinal cord and cauda equina injuries

Treatment of neuropathic pain in patients with spinal cord injury (SCI) and cauda equina injury (CEI) remains challenging. Dorsal root entry zone lesioning (DREZL) or DREZotomy is a viable surgical option for refractory cases. This study aimed to compare DREZL surgical outcomes between patients with SCI and those with CEI and to identify predictors of postoperative pain relief. We retrospectively analyzed 12 patients (6 with SCI and 6 with CEI) with intractable neuropathic pain who underwent DREZL. The data collected were demographic characteristics, pain distribution, and outcomes assessed by numeric pain rating scores. Variables and percentages of pain improvement at 1 year and long-term were statistically compared between the SCI and CEI groups. The demographic characteristics and percentage of patients who experienced pain improvement at 1 year postoperatively did not differ between the groups. Compared with the SCI group, the CEI group presented significantly better long-term pain reduction (p = 0.020) and favorable operative outcomes (p = 0.015). Patients with border zone pain had significantly better long-term pain relief and outcomes than did those with diffuse pain (p = 0.008 and p = 0.010, respectively). Recurrent pain after DREZL occurred in the SCI group but not in the CEI group. DREZL provided superior pain relief in patients with CEI. The presence of border zone pain predicted favorable outcomes. CEI patients or SCI patients with border zone pain are good surgical candidates for DREZL, whereas SCI patients with below-injury diffuse pain are poor candidates.

A Flexible, Implantable, Bioelectronic Electroporation Device for Targeted Ablation of Seizure Foci in the Mouse Brain

The primary method of treatment for patients suffering from drug-resistant focal-onset epilepsy is resective surgery, which adversely impacts neurocognitive function. Radio frequency (RF) ablation and laser ablation are the methods with the most promise, achieving seizure-free rates similar to resection but with less negative impact on neurocognitive function. However, there remains a number of concerns and open technical questions about these two methods of thermal ablation, with the primary ones: (1) heating; (2) hemorrhage and bleeding; and (3) poor directionality. Irreversible electroporation (IRE) is a proven method of focal ablation, which circumvents all three of the primary concerns regarding focal RF and laser ablation. Here, we demonstrate the in vivo application of a flexible implant with organic electrodes for focal ablation of epilepsy foci using high-frequency IRE (H-FIRE) in mice. Our results show that local, targeted ablation is possible in the close neighborhood of the electrode, paving the way for the clinical application in the treatment of focal epilepsy.

Clinical study of short-term spinal cord stimulation for herpes zoster-associated pain

BACKGROUND

Zoster-associated neuralgia refers to neuropathic pain from herpes zoster, which can persist as postherpetic neuralgia (PHN). Preventing the progression to chronic PHN is crucial, yet optimal interventions is still not clear.

OBJECTIVES

This study evaluates the efficacy of short-term spinal cord stimulation (tSCS) in patients with subacute and chronic PHN.

METHODS

A clinical study involved 135 patients with herpes zoster-associated pain (HZAP), divided into two groups: Experimental group which received short-term spinal cord stimulation therapy, and Control group which received conventional medical treatment and nerve block therapy. Pain intensity, sleep quality, anxiety and depression and quality of life were assessed at baseline and at 2 weeks, 1-, 3-, 6-, and 12-month post-treatment. Univariate and multivariate analyses identified factors associated with treatment efficacy.

RESULTS

At 1-month follow-up, the experimental group showed significantly higher efficacy in pain reduction (P < 0.01). Higher Pittsburgh Sleep Quality Index (β = 0.093, P = 0.004) and PHQ-9 scores (β = 0.065, P = 0.031) before treatment were associated with better outcomes. At 3 months, longer disease duration (β = 0.103, P = 0.008) and higher Pittsburgh Sleep Quality Index scores (β = 0.114, P = 0.002) correlated with better efficacy, while higher Patient Health Questionnaire-9 scores were negatively correlated (β = - 0.023, P = 0.036). Although as follow-up time increases, the significant superiority of efficacy gradually shrinks compared with nerve block therapy at 6-12 months, the tSCS group still had better effects in improving sleep quality, anxiety and depression symptoms, and quality of life.

CONCLUSIONS

Short-term spinal cord stimulation is a safe and effective short-term treatment for HZAP, offering faster and more effective pain relief and quality of life improvement compared to nerve block therapy. However, there are challenges in maintaining the long-term effects of tSCS. Further studies with larger samples are needed to confirm these findings.

Spinal Cord Stimulation Paradigms and Alleviation of Neuropathic Pain Behavior in Experimental Painful Diabetic Polyneuropathy

OBJECTIVES

Spinal cord stimulation (SCS) is an alternative treatment option for painful diabetic polyneuropathy (PDPN). Differential target multiplexed (DTM)-SCS is proposed to be more effective than conventional (Con)-SCS. Animal studies are essential for understanding SCS mechanisms in PDPN pain relief. Although the Von Frey (VF) test is the gold standard for preclinical pain research, it has limitations. Operant testing using the conditioned place preference (CPP) test provides insights into spontaneous neuropathic pain relief and enhances the translatability of findings. This study aims to 1) use the CPP test to evaluate Con- and DTM-SCS effects on spontaneous neuropathic pain relief in PDPN animals and 2) investigate the correlation between mechanical hypersensitivity alleviation and spontaneous neuropathic pain relief.

MATERIAL AND METHODS

Diabetes was induced through streptozotocin injection in 32 rats; 16 animals developed PDPN and were implanted with a quadripolar lead. Rats were conditioned for Con-SCS (n = 8) or DTM-SCS (n = 7), and a preference score compared with sham was determined. After conditioning, a 30-minute SCS protocol was conducted. Mechanical sensitivity was assessed using VF before, during, and after SCS.

RESULTS

There were no significant chamber preference changes for DTM-SCS (p = 0.3449) or Con-SCS (p = 0.3632). Subgroups of responders and nonresponders were identified with significant increases in preference score for responders for both DTM-SCS (-266.6 to 119.8; p = 0.0238; n = 4) and Con-SCS (-350.7 to 88.46; p = 0.0148; n = 3). No strong correlation between SCS-induced spontaneous neuropathic pain relief and effects on mechanical hypersensitivity in PDPN animals is noted.

CONCLUSIONS

The CPP test is a valuable tool to test the efficacy of the pain-relieving potential of various SCS paradigms in PDPN animals. The results of this study show no differences in spontaneous neuropathic pain relief between DTM- and Con-SCS in PDPN animals. Furthermore, there is no correlation between the effect of SCS in spontaneous pain relief and hind paw mechanical hypersensitivity.

The Effect of Spinal Cord Stimulation on Spinal Dorsal Horn Lipid Expression in Experimental Painful Diabetic Polyneuropathy: A Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry Imaging Study

OBJECTIVES

Diabetes-induced peripheral nerve fiber damage can cause painful diabetic polyneuropathy (PDPN), induced by central sensitization through proinflammatory processes in the spinal dorsal horn. Disturbances in spinal dorsal horn lipid metabolism play a major role in proinflammatory regulation. Conventional (Con)-spinal cord stimulation (SCS) is an alternative treatment for pain relief in PDPN, whereas differential target multiplexed (DTM)-SCS could be more effective than Con-SCS, specifically targeting the spinal inflammatory response. We hypothesize that Con- and DTM-SCS differentially affect lipid metabolism in the spinal cord of PDPN animals. To study pain relief mechanisms, we analyzed lipid expression in the spinal dorsal horn using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry imaging (MSI).

MATERIAL AND METHODS

Diabetes was induced through streptozotocin (STZ) injection in 28 rats, of which 12 developed PDPN. These and four nondiabetic animals (sham STZ) were implanted with a quadripolar lead and stimulated with Con-, DTM-, or Sham-SCS for 48 hours. Mechanical sensitivity was assessed using Von Frey filaments after 24 and 48 hours. After 48 hours of SCS, the spinal cord was collected, and lipids were analyzed using MALDI-TOF MSI.

RESULTS

STZ-induced hypersensitivity in the hind paws was reduced by Con- and DTM-SCS. PDPN induction decreased the expression of a glycosphingolipid in laminae 3 of the spinal dorsal horn. After 48 hours of Con- and DTM-SCS, expression levels of several lipids in the spinal dorsal horn decreased, including (HexCer 36:1;O, 40:1;O3), diacylglycerophosphocholines (PC 36:1, 38:6, 40:5), and diacylglycerophosphoserines (PS 36:4).

CONCLUSIONS

Both Con- and DTM-SCS provide pain relief and decrease spinal dorsal horn lipid expression of PDPN animals, highlighting the complex effects of SCS on the spinal cord physiology. STZ-induced PDPN has a limited effect on lipid expression in the spinal dorsal horn.

Pathophysiology of Pain and Mechanisms of Neuromodulation: A Narrative Review (A Neuron Project)

Pain serves as a vital innate defense mechanism that can significantly impact an individual's quality of life. Understanding the physiological effects of pain well plays an important role in developing novel pain treatments. Nociceptor neurons play a key role in pain and inflammation. Interactions between nociceptors and the immune system occur both at the site of injury and within the central nervous system. Modulating chemical mediators and nociceptor activity offers promising new approaches to pain management. Essentially, the sensory nervous system is essential for modulating the body's protective response, making it critical to understand these interactions to discover new pain treatment strategies. New innovations in neuromodulation have led to alternatives to opioids individuals with chronic pain with consequent improvement in disease-based treatment and nerve targeting. New neural targets from cellular and structural perspectives have revolutionized the field of neuromodulation. This narrative review aims to elucidate the mechanisms of pain transmission and processing, examine the characteristics and properties of nociceptors, and explore how the immune system influences pain perception. It further provides an updated overview of the physiology of pain and neuromodulatory mechanisms essential for managing acute and chronic pain. We assess the current understanding of different pain types, focusing on key molecules involved in each type and their physiological effects. Additionally, we compare painful and painless neuropathies and discuss the neuroimmune interactions involved in pain manifestation.

Structural changes in the nociceptive system induced by long-term conventional spinal cord stimulation in experimental painful diabetic polyneuropathy

BACKGROUND

Clinical studies suggest that long-term conventional spinal cord stimulation (LT-SCS) for painful diabetic peripheral neuropathy (PDPN) is initially effective but may decline in efficacy over time. Preclinical studies indicate that LT-SCS alleviates mechanical hypersensitivity and enhances hind paw blood flow in PDPN rats, suggesting nociceptive system plasticity. This study hypothesized that LT-SCS induces peripheral hind paw small-fiber sprouting and reduces central protein expression of glial and P2X4 brain-derived neurotrophic factor (BDNF) pathway markers.

METHODS

Diabetes was induced via Streptozotocin injection in 32 rats, with 16 developing PDPN and receiving a quadrupolar lead implant. LT-SCS was applied for 4 weeks, 12 hours per day. Pain behavior was assessed using the Von Frey test for mechanical hypersensitivity and the mechanical conflict avoidance system for motivational aspects of pain. Fiber sprouting was assessed via immunohistochemical analysis of nerve fibers in the hind paw skin. Protein expression in the spinal cord was assessed using western blotting.

RESULTS

LT-SCS increased the baseline threshold of mechanical hypersensitivity in PDPN animals, consistent with previous findings, but showed no effects on motivational aspects of pain. Hind paw tissue analysis revealed significantly increased intraepidermal nerve fiber density of PGP9.5 fibers in LT-SCS animals compared with Sham-SCS animals. Protein analysis showed significantly decreased pro-BDNF expression in LT-SCS animals compared with Sham-SCS animals.

CONCLUSION

LT-SCS induces structural changes in both peripheral and central components of the nociceptive system in PDPN animals. These changes may contribute to observed behavioral modifications, elucidating mechanisms underlying LT-SCS efficacy in PDPN management.

Progress in treatment of pathological neuropathic pain after spinal cord injury

Pathological neuropathic pain is a common complication following spinal cord injury. Due to its high incidence, prolonged duration, tenacity, and limited therapeutic efficacy, it has garnered increasing attention from both basic researchers and clinicians. The pathogenesis of neuropathic pain after spinal cord injury is multifaceted, involving factors such as structural and functional alterations of the central nervous system, pain signal transduction, and inflammatory effects, posing significant challenges to clinical management. Currently, drugs commonly employed in treating spinal cord injury induced neuropathic pain include analgesics, anticonvulsants, antidepressants, and antiepileptics. However, a subset of patients often experiences suboptimal therapeutic responses or severe adverse reactions. Therefore, emerging treatments are emphasizing a combination of pharmacological and non-pharmacological approaches to enhance neuropathic pain management. We provide a comprehensive review of past literature, which aims to aim both the mechanisms and clinical interventions for pathological neuropathic pain following spinal cord injury, offering novel insights for basic science research and clinical practice in spinal cord injury treatment.

Sensors and Devices Guided by Artificial Intelligence for Personalized Pain Medicine

Personalized pain medicine aims to tailor pain treatment strategies for the specific needs and characteristics of an individual patient, holding the potential for improving treatment outcomes, reducing side effects, and enhancing patient satisfaction. Despite existing pain markers and treatments, challenges remain in understanding, detecting, and treating complex pain conditions. Here, we review recent engineering efforts in developing various sensors and devices for addressing challenges in the personalized treatment of pain. We summarize the basics of pain pathology and introduce various sensors and devices for pain monitoring, assessment, and relief. We also discuss advancements taking advantage of rapidly developing medical artificial intelligence (AI), such as AI-based analgesia devices, wearable sensors, and healthcare systems. We believe that these innovative technologies may lead to more precise and responsive personalized medicine, greatly improved patient quality of life, increased efficiency of medical systems, and reducing the incidence of addiction and substance use disorders.

Optimizing Pain Management in Emergency Departments: A Comprehensive Review of Current Analgesic Practices

Effective pain management in Emergency Departments (EDs) is vital for improving patient comfort and clinical outcomes. This review provides a comprehensive analysis of current pain management practices in ED settings, focusing on the challenges and opportunities for optimization. The review examines pharmacologic and non-pharmacologic pain management strategies, evaluating their effectiveness and identifying inconsistencies and gaps in current practices. Key challenges in the ED environment include time constraints, variability in clinical protocols, and the need to address diverse patient needs, including those of paediatric, geriatric, and chronic pain patients. The review highlights the importance of standardized pain assessment tools and protocols to improve consistency in pain management. Innovations, such as technological advances and multimodal approaches, are explored for their potential to enhance pain management practices. Recommendations address identified challenges, including improved training for ED staff, the development of evidence-based protocols, and the integration of multimodal pain management strategies. By addressing these areas, the review aims to contribute to the development of more effective and uniform pain management practices in emergency care, ultimately leading to better patient outcomes and experiences. This review emphasizes the need for ongoing research and adaptation of best practices to meet the evolving needs of patients in emergency settings.

Spinal Cord Stimulation for Intractable Chronic Limb Ischemia: A Narrative Review

Critical limb ischemia (CLI) is the most severe form of peripheral arterial disease, significantly impacting quality of life, morbidity and mortality. Common complications include severe limb pain, walking difficulties, ulcerations and limb amputations. For cases of CLI where surgical or endovascular reconstruction is not possible or fails, spinal cord stimulation (SCS) may be a treatment option. Currently, SCS is primarily prescribed as a symptomatic treatment for painful symptoms. It is used to treat intractable pain arising from various disorders, such as neuropathic pain secondary to persistent spinal pain syndrome (PSPS) and painful diabetic neuropathy. Data regarding the effect of SCS in treating CLI are varied, with the mechanism of action of vasodilatation in the peripheral microcirculatory system not yet fully understood. This review focuses on the surgical technique, new modalities of SCS, the mechanisms of action of SCS in vascular diseases and the parameters for selecting CLI patients, along with the clinical outcomes and complications. SCS is a safe and effective surgical option in selected patients with CLI, where surgical or endovascular revascularization is not feasible.

Comparative Analysis of the Efficacy of Spinal Cord Stimulation and Traditional Debridement Care in the Treatment of Ischemic Diabetic Foot Ulcers: A Retrospective Cohort Study

BACKGROUND AND OBJECTIVES

Spinal cord stimulation (SCS) is an effective treatment for diabetic peripheral neuropathy. The purpose of this study was to investigate the effectiveness of SCS in the treatment of ischemic diabetic foot ulcers.

METHODS

In this retrospective study, the SCS group comprised 102 patients with ischemic diabetic foot who were treated with SCS for foot ulcers and nonhealing wounds due to severe lower limb ischemia. The traditional debridement care (TDC) group comprised 104 patients with ischemic diabetic foot who received only TDC. Strict screening criteria were applied. The assignment of patients to either group depended solely on their willingness to be treated with SCS. Secondary end points were transcutaneous partial pressure of oxygen (PtcO 2 ), ankle-brachial index (ABI), and color Doppler of the lower limb arteries in the feet at 6 months and 12 months after treatment. The primary end point was the amputation.

RESULTS

The dorsal foot PtcO 2 and ABI of the patients in the SCS group were significantly improved at 6 months and 12 months postoperation ( P < .05). The therapeutic efficacy was significantly better than that of the TDC group over the same period of time ( P < .05). The degree of vasodilation of the lower limb arteries (ie, femoral, popliteal, posterior tibial, and dorsalis pedis arteries) on color Doppler was higher in the SCS group than in the TDC group ( P < .05). The odds ratios for total amputation at 6 and 12 months postoperatively in the SCS group were 0.45 (95% CI, 0.19-1.08) and 0.17 (95% CI, 0.08-0.37), respectively, compared with the TDC group.

CONCLUSION

SCS improved symptoms of lower limb ischemia in ischemic diabetic feet and reduced the rate of toe amputation by increasing PtcO 2 , ABI, and arterial vasodilation in the lower limbs.

Burst Stimulation Evokes Increased Bladder and Urethral Pressure in Patients With Sacral Neuromodulation, Indicating Potential Activation of the Autonomic Nervous System: A Pilot Study

OBJECTIVES

Currently, sacral neuromodulation (SNM) outcomes are often suboptimal, and changing stimulation parameters might improve SNM efficacy. Burst stimulation mimics physiological burst firing of the nervous system and might therefore benefit patients treated with SNM. The purpose of the present pilot study was to evaluate the effect of various Burst SNM paradigms on bladder and urethral pressure in patients with overactive bladder (OAB) or nonobstructive urinary retention (NOUR).

MATERIALS AND METHODS

The bladder was filled to 50% of its capacity under general anesthesia in six patients with an implanted sacral lead for SNM purposes. Bladder pressure, and mid- and proximal urethral pressure were measured using conventional (Con-) SNM and various Burst SNM paradigms (10-20-40 Hz interburst frequency) with increasing amplitudes up to 5 mA for Con-SNM and 4 mA for Burst SNM.

RESULTS

Burst SNM caused a substantial increase in both bladder and urethral pressure. In contrast, Con-SNM caused a milder increase in urethral pressure, and only one patient showed a modest increase in bladder pressure. Furthermore, the pressure increase was higher in the proximal urethra than in the midurethra using Burst-SNM, whereas Con-SNM caused comparable increases in proximal and midurethra pressure.

CONCLUSIONS

Burst SNM induces bladder contraction compared with Con-SNM and induces higher pressure increases in bladder and proximal urethra than does Con-SNM in patients with OAB or NOUR, indicating a higher degree of autonomic nervous system stimulation. The observed responses could not be fully explained by the total charge of the Burst SNM paradigms, which suggests the importance of individual Burst SNM parameters, such as frequency and amplitude. Future studies should assess the feasibility and efficacy of Burst SNM in awake patients.

Research hotspots and trends of spinal cord stimulation for neuropathic pain: a bibliometric analysis from 2004 to 2023

The purpose of this study is to systematically analyze the development trend, research hotspots, and future development direction on the treatment of neuropathic pain (NP) with spinal cord stimulation through bibliometric method. We extracted the literature related to the treatment of NP with spinal cord stimulation from January 2004 to December 2023 from the Web of Science database. As a result, a total of 264 articles were retrieved. By analyzing the annual published articles, authors, countries, institutions, journals, co-cited literature, and keywords, we found that the count of publication in this field has been experiencing an overall growth, and the publications within the past 5 years accounted for 42% of the total output. Experts from the United States and the UK have made significant contributions in this field and established a stable collaborative team, initially establishing an international cooperation network. Pain is the frequently cited journal in this field. The study on spinal cord stimulation therapy for NP especially the study on spinal cord stimulation therapy for back surgery failure syndrome (FBSS) and its potential mechanisms are the research hotspots in this field, while the study on novel paradigms such as high-frequency spinal cord stimulation and spinal cord burst stimulation represents the future development directions. In short, spinal cord stimulation has been an effective treatment method for NP. The novel paradigms of spinal cord stimulation are the key point of future research in this field.

Examining the Duration of Carryover Effect in Patients With Chronic Pain Treated With Spinal Cord Stimulation (EChO Study): An Open, Interventional, Investigator-Initiated, International Multicenter Study

OBJECTIVES

Spinal cord stimulation (SCS) is a surgical treatment for severe, chronic, neuropathic pain. It is based on one to two lead(s) implanted in the epidural space, stimulating the dorsal column. It has long been assumed that when deactivating SCS, there is a variable interval before the patient perceives the return of the pain, a phenomenon often termed echo or carryover effect. Although the carryover effect has been problematized as a source of error in crossover studies, no experimental investigation of the effect has been published. This open, prospective, international multicenter study aimed to systematically document, quantify, and investigate the carryover effect in SCS.

MATERIALS AND METHODS

Eligible patients with a beneficial effect from their SCS treatment were instructed to deactivate their SCS device in a home setting and to reactivate it when their pain returned. The primary outcome was duration of carryover time defined as the time interval from deactivation to reactivation. Central clinical parameters (age, sex, indication for SCS, SCS treatment details, pain score) were registered and correlated with carryover time using nonparametric tests (Mann-Whitney/Kruskal-Wallis) for categorical data and linear regression for continuous data.

RESULTS

In total, 158 patients were included in the analyses. A median carryover time of five hours was found (interquartile range 2.5;21 hours). Back pain as primary indication for SCS, high-frequency stimulation, and higher pain score at the time of deactivation were correlated with longer carryover time.

CONCLUSIONS

This study confirms the existence of the carryover effect and indicates a remarkably high degree of interindividual variation. The results suggest that the magnitude of carryover may be correlated to the nature of the pain condition and possibly stimulation paradigms.

CLINICAL TRIAL REGISTRATION

The Clinicaltrials.gov registration number for the study is NCT03386058.

Cervical Spinal Cord Stimulation for Failed Neck Surgery Syndrome

PURPOSE OF REVIEW

Cervical spine pain with or without radicular symptoms is a common condition leading to high utilization of the healthcare system with over 10 million medical visits per year. Many patients undergo surgical interventions and unfortunately are still left with neck and upper extremity pain, sometimes referred to as "Failed Neck Surgery Syndrome." When these options fail, cervical spinal cord stimulation can be a useful tool to decrease pain and suffering as well as reduce prescription medication use.

RECENT FINDINGS

Spinal cord stimulation is a well-established therapy for chronic back and leg pain and is becoming more popular for neck and upper extremity pain. Recent studies have explored cervical spinal cord stimulation with successful outcomes regarding improved pain scores, functional outcomes, and reduction of prescription medication use. Continued research into cervical spinal cord stimulation is essential for maximizing its therapeutic potential for patients with chronic neck and upper extremity pain. This review highlights the importance of cervical spinal cord stimulation as an option for patients with failed neck surgery syndrome.

A Narrative Review of the Dorsal Root Ganglia and Spinal Cord Mechanisms of Action of Neuromodulation Therapies in Neuropathic Pain

Neuropathic pain arises from injuries to the nervous system in diseases such as diabetes, infections, toxicity, and traumas. The underlying mechanism of neuropathic pain involves peripheral and central pathological modifications. Peripheral mechanisms entail nerve damage, leading to neuronal hypersensitivity and ectopic action potentials. Central sensitization involves a neuropathological process with increased responsiveness of the nociceptive neurons in the central nervous system (CNS) to their normal or subthreshold input due to persistent stimuli, leading to sustained electrical discharge, synaptic plasticity, and aberrant processing in the CNS. Current treatments, both pharmacological and non-pharmacological, aim to alleviate symptoms but often face challenges due to the complexity of neuropathic pain. Neuromodulation is emerging as an important therapeutic approach for the treatment of neuropathic pain in patients unresponsive to common therapies, by promoting the normalization of neuronal and/or glial activity and by targeting cerebral cortical regions, spinal cord, dorsal root ganglia, and nerve endings. Having a better understanding of the efficacy, adverse events and applicability of neuromodulation through pre-clinical studies is of great importance. Unveiling the mechanisms and characteristics of neuromodulation to manage neuropathic pain is essential to understand how to use it. In the present article, we review the current understanding supporting dorsal root ganglia and spinal cord neuromodulation as a therapeutic approach for neuropathic pain.

Acupoint Stimulation for Pain Control in Enhanced Recovery After Surgery: Systematic Review and Meta-Analysis

Introduction: Postoperative pain control is a challenge in enhanced recovery after surgery (ERAS). The current study reviewed the efficacy and safety of incorporating acupoint stimulation for postoperative pain control in ERAS. Methods: Ten databases for relevant randomized controlled trials (RCTs) published in English or Mandarin Chinese were searched from 1997 to 2022. The quality of each article was appraised using the Cochrane Collaboration Risk of Bias Criteria and the modified Jadad Scale. The primary outcome was pain control, measured using the visual analog scale 24 h after surgery. Results: Eleven trials met the eligibility criteria and were included in the study. Acupoint stimulation was found more effective than control treatments in terms of pain intensity (standardized mean difference [SMD] -0.94; 95% confidence interval [CI] -1.35 to -0.53), analgesic drug consumption (SMD -1.87; 95% CI -2.98 to -0.75), postoperative nausea (PON; SMD 0.31; 95% CI 0.13 to 0.73), postoperative vomiting (POV; SMD 0.57; 95% CI 0.11 to 2.92), and PON and POV (PONV; SMD 0.29; 95% CI 0.16 to 0.53). The Zusanli (ST36) and Neiguan (PC6) were the most-used acupoints in the included trials (8/11). The reported adverse reaction was only one case of bruising. Discussion: Acupoint stimulation improved pain control in patients undergoing ERAS more than control treatments. The findings provide an evidence-based premise for incorporating acupoint stimulation into ERAS strategies. More rigorous RCTs are needed in the future.

Unintentionally intentional: unintended effects of spinal stimulation as a platform for multi-modal neurorehabilitation after spinal cord injury

Electrical stimulation of spinal neurons has emerged as a valuable tool to enhance rehabilitation after spinal cord injury. In separate parameterizations, it has shown promise for improving voluntary movement, reducing symptoms of autonomic dysreflexia, improving functions mediated by muscles of the pelvic floor (e.g., bowel, bladder, and sexual function), reducing spasms and spasticity, and decreasing neuropathic pain, among others. This diverse set of actions is related both to the density of sensorimotor neural networks in the spinal cord and to the intrinsic ability of electrical stimulation to modulate neural transmission in multiple spinal networks simultaneously. It also suggests that certain spinal stimulation parameterizations may be capable of providing multi-modal therapeutic benefits, which would directly address the complex, multi-faceted rehabilitation goals of people living with spinal cord injury. This review is intended to identify and characterize reports of spinal stimulation-based therapies specifically designed to provide multi-modal benefits and those that report relevant unintended effects of spinal stimulation paradigms parameterized to enhance a single consequence of spinal cord injury.

High-Frequency Spinal Stimulation Suppresses Microglial Kaiso-P2X7 Receptor Axis-Induced Inflammation to Alleviate Neuropathic Pain in Rats

OBJECTIVE

Neuropathic pain poses a persistent challenge in clinical management. Neuromodulation has emerged as a last-resort therapy. Conventional spinal cord stimulation (Con SCS) often causes abnormal sensations and provides short analgesia, whereas high-frequency spinal cord stimulation (HF SCS) is a newer therapy that effectively alleviates pain without paresthesia. However, the modes of action of 10kHz HF SCS (HF10 SCS) in pain relief remain unclear. To bridge this knowledge gap, we employed preclinical models that mimic certain features of clinical SCS to explore the underlying mechanisms of HF10 SCS. Addressing these issues would provide the scientific basis for improving and evaluating the effectiveness, reliability, and practicality of different frequency SCS in clinical settings.

METHODS

We established a preclinical SCS model to examine its effects in a neuropathic pain rat model. We conducted bulk and single-cell RNA sequencing in the spinal dorsal horn (SDH) to examine cellular and molecular changes under different treatments. We employed genetic manipulations through intrathecal injection of a lentiviral system to explore the SCS-mediated signaling axis in pain. Various behavioral tests were performed to evaluate pain conditions under different treatments.

RESULTS

We found that HF10 SCS significantly reduces immune responses in the SDH by inactivating the Kaiso-P2X7R pathological axis in microglia, promoting long-lasting pain relief. Targeting Kaiso-P2X7R in microglia dramatically improved efficacy of Con SCS treatment, leading to reduced neuroinflammation and long-lasting pain relief.

INTERPRETATION

HF10 SCS could improve the immunopathologic state in the SDH, extending its benefits beyond symptom relief. Targeting the Kaiso-P2X7R axis may enhance Con SCS therapy and offer a new strategy for pain management. ANN NEUROL 2024;95:966-983.

Comparison of the efficacy of spinal cord stimulation and dorsal root ganglion stimulation in the treatment of painful diabetic peripheral neuropathy: a prospective, cohort-controlled study

Objective

The aim of this study was to compare the clinical outcomes of spinal cord stimulation (SCS) and dorsal root ganglion stimulation (DRG-S) in the treatment of painful diabetic peripheral neuropathy (PDPN).

Methods

In this prospective cohort study, 55 patients received dorsal column spinal cord stimulation (SCS group) and 51 patients received dorsal root spinal cord stimulation (DRG-S group). The primary outcome was a Numerical Rating Scale (NRS) remission rate of ≥50%, and secondary outcomes included the effects of SCS and DRG-S on quality of life scores (EQ-5D-3L), nerve conduction velocity, and HbA1c, respectively.

Results

The percentage of NRS remission rate ≥ 50% at 6 months was 80.43 vs. 79.55%, OR (95% CI): 1.06 (0.38-2.97) in the SCS and DRG-S groups, respectively, and the percentage of VAS remission rate ≥ 50% at 12 months was 79.07 vs. 80.95%, OR (95% CI): 0.89 (0.31-2.58). Compared with baseline, there were significant improvements in EQ-5D and EQ-VAS at 6 and 12 months (p < 0.05), but there was no difference in improvement between the SCS and DRG-S groups (p > 0.05). Nerve conduction velocities of the common peroneal, peroneal, superficial peroneal, and tibial nerves were significantly improved at 6 and 12 months compared with the preoperative period in both the SCS and PND groups (p < 0.05). However, at 6 and 12 months, there was no difference in HbA1c between the two groups (p > 0.05).

Conclusion

Both SCS and DRG-S significantly improved pain, quality of life, and lower extremity nerve conduction velocity in patients with PDPN, and there was no difference between the two treatments at 12 months.

1. Lumbosacral radicular pain

INTRODUCTION

Patients suffering lumbosacral radicular pain report radiating pain in one or more lumbar or sacral dermatomes. In the general population, low back pain with leg pain extending below the knee has an annual prevalence that varies from 9.9% to 25%.

METHODS

The literature on the diagnosis and treatment of lumbosacral radicular pain was reviewed and summarized.

RESULTS

Although a patient's history, the pain distribution pattern, and clinical examination may yield a presumptive diagnosis of lumbosacral radicular pain, additional clinical tests may be required. Medical imaging studies can demonstrate or exclude specific underlying pathologies and identify nerve root irritation, while selective diagnostic nerve root blocks can be used to confirm the affected level(s). In subacute lumbosacral radicular pain, transforaminal corticosteroid administration provides short-term pain relief and improves mobility. In chronic lumbosacral radicular pain, pulsed radiofrequency (PRF) treatment adjacent to the spinal ganglion (DRG) can provide pain relief for a longer period in well-selected patients. In cases of refractory pain, epidural adhesiolysis and spinal cord stimulation can be considered in experienced centers.

CONCLUSIONS

The diagnosis of lumbosacral radicular pain is based on a combination of history, clinical examination, and additional investigations. Epidural steroids can be considered for subacute lumbosacral radicular pain. In chronic lumbosacral radicular pain, PRF adjacent to the DRG is recommended. SCS and epidural adhesiolysis can be considered for cases of refractory pain in specialized centers.

Neuromodulation Techniques in Chronic Refractory Coccydynia: A Narrative Review

Refractory coccydynia is a condition characterized by severe coccygeal pain and poses a challenging management dilemma for clinicians. Advancements in neuromodulation (NM) technology have provided benefits to people experiencing chronic pain that is resistant to standard treatments. This review aims to summarize the spectrum of current NM techniques employed in the treatment of refractory coccydynia along with their effectiveness. A review of studies in the scientific literature from 2012 to 2023 was conducted, revealing a limited number of case reports. Although the available evidence at this time suggests significant pain relief with the utilization of NM techniques, the limited scope and nature of the studies reviewed emphasize the need for large-scale, rigorous, high-level research in this domain in order to establish a comprehensive understanding of the role of NM and its effectiveness in the management of intractable coccydynia.

Evoked compound action potential (ECAP)-controlled closed-loop spinal cord stimulation in an experimental model of neuropathic pain in rats

BACKGROUND

Preclinical models of spinal cord stimulation (SCS) are lacking objective measurements to inform translationally applicable SCS parameters. The evoked compound action potential (ECAP) represents a measure of dorsal column fiber activation. This measure approximates the onset of SCS-induced sensations in humans and provides effective analgesia when used with ECAP-controlled closed-loop (CL)-SCS systems. Therefore, ECAPs may provide an objective surrogate for SCS dose in preclinical models that may support better understanding of SCS mechanisms and further translations to the clinics. This study assessed, for the first time, the feasibility of recording ECAPs and applying ECAP-controlled CL-SCS in freely behaving rats subjected to an experimental model of neuropathic pain.

METHODS

Adult male Sprague-Dawley rats (200-300 g) were subjected to spared nerve injury (SNI). A custom-made six-contact lead was implanted epidurally covering T11-L3, as confirmed by computed tomography or X-ray. A specially designed multi-channel system was used to record ECAPs and to apply ECAP-controlled CL-SCS for 30 min at 50 Hz 200 µs. The responses of dorsal column fibers to SCS were characterized and sensitivity towards mechanical and cold stimuli were assessed to determine analgesic effects from ECAP-controlled CL-SCS. Comparisons between SNI rats and their controls as well as between stimulation parameters were made using omnibus analysis of variance (ANOVA) tests and t-tests.

RESULTS

The recorded ECAPs showed the characteristic triphasic morphology and the ECAP amplitude (mV) increased as higher currents (mA) were applied in both SNI animals and controls (SNI SCS-ON and sham SCS-ON). Importantly, the use of ECAP-based SCS dose, implemented in ECAP-controlled CL-SCS, significantly reduced mechanical and cold hypersensitivity in SNI SCS-ON animals through the constant and controlled activation of dorsal column fibers. An analysis of conduction velocities of the evoked signals confirmed the involvement of large, myelinated fibers.

CONCLUSIONS

The use of ECAP-based SCS dose implemented in ECAP-controlled CL-SCS produced analgesia in animals subjected to an experimental model of neuropathic pain. This approach may offer a better method for translating SCS parameters between species that will improve understanding of the mechanisms of SCS action to further advance future clinical applications.

Burst Spinal Cord Stimulation as Compared With L2 Dorsal Root Ganglion Stimulation in Pain Relief for Nonoperated Discogenic Low Back Pain: Analysis of Two Prospective Studies

INTRODUCTION

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

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

The clinical trial registration numbers for the study are NCT03958604 and NL54405.091.15.

Exploring Patient Satisfaction and Other Outcome Measures With Pain Relief in Spinal Cord Stimulation: A Single-Site, Cohort Audit

Context Spinal cord stimulation (SCS) is an approved treatment for chronic pain of neuropathic origin. Initial research suggests a close relationship between pain relief and patient satisfaction with SCS. Objectives To see whether similar patterns were observed in our center and to identify areas of improvement, this single-site, cohort audit explored the association between pain relief and satisfaction as well as specific factors that influence satisfaction at follow-up in patients with fully implanted SCS. Methods Age, gender, pain condition, SCS system, average pain (numerical rating scale, NRS), and worst pain (NRS) scores at baseline and the most recent follow-up visit were collected. Percentage change in average pain was calculated, and the patients were allocated to one of three pain improvement groups: <30%, 30%-50%, or >50%. A telephone survey explored patient outcomes including patient satisfaction, sleep, fatigue, quality of life (QoL), walking ability, and medication use. Chi-square tests of independence were performed. Results The final sample comprised 87 patients (<30%: n = 26; 30%-50%: n = 29; >50%: n = 32). The pain improvement group was significantly associated with satisfaction (p = 0.010): all patients in the >50% improvement group reported being either very satisfied or somewhat satisfied with SCS. The pain improvement group was also significantly associated with change in sleep (p < 0.001), fatigue (p = 0.001), QoL (p = 0.003), and opioid consumption (p = 0.010). Improvements were most frequently reported in the >50% improvement group. Conclusion Findings point to an association between pain relief and patient satisfaction with SCS. Other factors, including sleep, fatigue, QoL, and opioid consumption, may influence this association and deserve further exploration.

Novel Pulsed Ultrahigh-frequency Spinal Cord Stimulation Inhibits Mechanical Hypersensitivity and Brain Neuronal Activity in Rats after Nerve Injury

BACKGROUND

Spinal cord stimulation (SCS) is an important pain treatment modality. This study hypothesized that a novel pulsed ultrahigh-frequency spinal cord stimulation (pUHF-SCS) could safely and effectively inhibit spared nerve injury-induced neuropathic pain in rats.

METHODS

Epidural pUHF-SCS (± 3V, 2-Hz pulses comprising 500-kHz biphasic sinewaves) was implanted at the thoracic vertebrae (T9 to T11). Local field brain potentials after hind paw stimulation were recorded. Analgesia was evaluated by von Frey-evoked allodynia and acetone-induced cold allodynia.

RESULTS

The mechanical withdrawal threshold of the injured paw was 0.91 ± 0.28 g lower than that of the sham surgery (24.9 ± 1.2 g). Applying 5-, 10-, or 20-min pUHF-SCS five times every 2 days significantly increased the paw withdrawal threshold to 13.3 ± 6.5, 18.5 ± 3.6, and 21.0 ± 2.8 g at 5 h post-SCS, respectively (P = 0.0002, < 0.0001, and < 0.0001; n = 6 per group) and to 6.1 ± 2.5, 8.2 ± 2.7, and 14.3 ± 5.9 g on the second day, respectively (P = 0.123, 0.013, and < 0.0001). Acetone-induced paw response numbers decreased from pre-SCS (41 ± 12) to 24 ± 12 and 28 ± 10 (P = 0.006 and 0.027; n = 9) at 1 and 5 h after three rounds of 20-min pUHF-SCS, respectively. The areas under the curve from the C component of the evoked potentials at the left primary somatosensory and anterior cingulate cortices were significantly decreased from pre-SCS (101.3 ± 58.3 and 86.9 ± 25.5, respectively) to 39.7 ± 40.3 and 36.3 ± 20.7 (P = 0.021, and 0.003; n = 5) at 60 min post-SCS, respectively. The intensity thresholds for pUHF-SCS to induce brain and sciatic nerve activations were much higher than the therapeutic intensities and thresholds of conventional low-frequency SCS.

CONCLUSIONS

Pulsed ultrahigh-frequency spinal cord stimulation inhibited neuropathic pain-related behavior and paw stimulation evoked brain activation through mechanisms distinct from low-frequency SCS.

EDITOR’S PERSPECTIVE

A Novel, Paresthesia-Free Spinal Cord Stimulation Waveform for Chronic Neuropathic Low Back Pain: Six-Month Results of a Prospective, Single-Arm, Dose-Response Study

OBJECTIVES

The aim of this prospective, single-blinded, dose-response study was to evaluate the safety and efficacy of a novel, paresthesia-free (subperception) spinal cord stimulation (SCS) waveform designed to target dorsal horn dendrites for the treatment of chronic neuropathic low back pain (LBP).

MATERIALS AND METHODS

Twenty-seven participants with chronic neuropathic LBP were implanted with a commercial SCS system after a successful trial of SCS therapy. Devices were programmed to deliver the investigative waveform (100 Hz, 1000 μs, T9/T10 bipole) at descending stimulation perception threshold amplitudes (80%, 60%, 40%). Programs were evaluated at six, ten, and 14 weeks, after which participants selected their preferred program, with more follow-up at 26 weeks (primary outcomes). Participants were blinded to the nature of the programming. Pain score (visual analog scale [VAS]), Brief Pain Inventory (BPI), quality of life (EQ-5D-5L), and health status (36-Item Short Form [SF-36]) were measured at baseline and follow-ups. Responder rate, treatment satisfaction, clinician global impression of change, and adverse events (AEs) also were evaluated.

RESULTS

Mean (± SD) baseline VAS was 72.5 ± 11.2 mm. At 26 weeks (n = 26), mean change from baseline in VAS was -51.7 mm (95% CI, -60.7 to -42.7; p < 0.001), with 76.9% of participants reporting ≥50% VAS reduction, and 46.2% reporting ≥80% VAS reduction. BPI, EQ-5D-5L, and SF-36 scores were all statistically significantly improved at 26 weeks (p < 0.001), and 100% of participants were satisfied with their treatment. There were no unanticipated AEs related to the study intervention, device, or procedures.

CONCLUSIONS

This novel, paresthesia-free stimulation waveform may be a safe and effective option for patients with chronic neuropathic LBP eligible for SCS therapy and is deliverable by all current commercial SCS systems.

CLINICAL TRIAL REGISTRATION

This study is registered on anzctr.org.au with identifier ACTRN12618000647235.

Effect of Conventional Spinal Cord Stimulation on Serum Protein Profile in Patients With Persistent Spinal Pain Syndrome: A Case-Control Study

BACKGROUND

Spinal cord stimulation (SCS) provides pain relief for most patients with persistent spinal pain syndrome type 2 (PSPS 2). Evidence is mounting on molecular changes induced by SCS as one of the mechanisms to explain pain improvement. We report the SCS effect on serum protein expression in vivo in patients with PSPS 2.

MATERIALS AND METHODS

Serum proteins were identified and quantified using mass spectrometry. Proteins with significantly different expression among patients with PSPS 2 relative to controls, responders, and nonresponders to SCS, or significantly modulated by SCS relative to baseline, were identified. Those most correlated with the presence and time course of pain were selected using multivariate discriminant analysis. Bioinformatic tools were used to identify related biological processes.

RESULTS

Thirty patients with PSPS 2, of whom 23 responded to SCS, were evaluated, together with 14 controls with no pain who also had undergone lumbar spinal surgery. A significant improvement in pain intensity, disability, and quality of life was recorded among responders. Five proteins differed significantly at baseline between patients with PSPS 2 and controls, with three proteins, mostly involved in immune processes and inflammation, being downregulated and two, mostly involved in vitamin metabolism, synaptic transmission, and restorative processes, being upregulated. In addition, four proteins, mostly related to immune processes and inflammation, decreased significantly, and three, mostly related to iron metabolism and containment of synaptic sprouting, increased significantly during SCS.

CONCLUSION

This study identifies various biological processes that may underlie PSPS 2 pain and SCS therapeutic effects, including the modulation of neuroimmune response and inflammation, synaptic sprouting, vitamin and iron metabolism, and restorative processes.

Comparison Between the Efficacy of Spinal Cord Stimulation and of Endovascular Revascularization in the Treatment of Diabetic Foot Ulcers: A Retrospective Observational Study

OBJECTIVE

We aimed to compare the effects of spinal cord stimulation (SCS) with those of endovascular revascularization on the treatment of diabetic foot ulcers.

MATERIALS AND METHODS

A total of 104 patients with diabetic foot ulcers who met the inclusion criteria were retrospectively analyzed and classified to the SCS treatment group (n = 46) and endovascular revascularization treatment group (n = 46). The quality-of-life scores (Quality of Life Scale for Patients with Liver Cancer v2.0), visual pain analog scale score, lower limb skin temperature, lower limb arterial ultrasound results, and lower extremity electromyography results were analyzed to compare the efficacy of the two treatments for diabetic foot ulcers in the two groups before surgery and six months after surgery.

RESULTS

A total of 92 patients (men: 73.9%, mean age: 66.51 ± 11.67 years) completed the six-month postoperative follow-up period. The patients in the SCS treatment group had a higher quality-of-life score (25.54% vs 13.77%, p < 0.05), a larger reduction in pain scores (69.18% vs 37.21%, p < 0.05), and a larger reduction in foot temperature (18.56% vs 7.24%, p < 0.05) than those of the endovascular revascularization treatment group at six months after surgery. The degree of vasodilation in the lower limbs on color Doppler arterial ultrasound and the nerve conduction velocity were higher in the SCS treatment group than in the endovascular revascularization treatment group at six months after surgery (p < 0.05).

CONCLUSION

SCS was more effective than endovascular revascularization in improving quality of life, relieving pain, improving lower limb skin temperature, increasing lower limb blood flow, and improving nerve conduction in patients with diabetic foot ulcers at six months after surgery.

A prospective study of BurstDR™ spinal cord stimulation for non-operated discogenic low back pain

INTRODUCTION

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

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.

Conventional, high frequency and differential targeted multiplexed spinal cord stimulation in experimental painful diabetic peripheral neuropathy: Pain behavior and role of the central inflammatory balance

Spinal cord stimulation (SCS) is a last resort treatment for pain relief in painful diabetic peripheral neuropathy (PDPN) patients. However, the effectivity of SCS in PDPN is limited. New SCS paradigms such as high frequency (HF) and differential target multiplexed (DTM) might improve responder rates and efficacy of SCS-induced analgesia in PDPN patients, and are suggested to modulate the inflammatory balance and glial response in the spinal dorsal horn. The aim of this study was to research the effects of Con-, HF- and DTM-SCS on pain behavior and the spinal inflammatory balance in an animal model of PDPN. Streptozotocin-induced PDPN animals were stimulated for 48 hours with either Con-SCS (50Hz), HF-SCS (1200Hz) or DTM-SCS (combination of Con- and HF-SCS). Mechanical hypersensitivity was assessed using Von Frey (VF) test and the motivational aspects of pain were assessed using the mechanical conflict avoidance system (MCAS). The inflammatory balance and glial response were analyzed in the dorsal spinal cord based on RNA expression of pro- and anti-inflammatory cytokines (Tnf-α, Il-1ß, Il-4, Il-10), a microglia marker (Itgam), an astrocyte marker (Gfap), a T-cell marker (Cd3d), microglia proliferation markers (Irf8, Adgre1) and P2X4, p13-MAPK, BDNF signaling markers (P2x4, Mapk14, Bdnf). The results show that Con-, HF-, and DTM-SCS significantly decreased hypersensitivity after 48 hours of stimulation compared to Sham-SCS in PDPN animals, but at the same time did not affect escape latency in the MCAS. At the molecular level, Con-SCS resulted in a significant increase in spinal pro-inflammatory cytokine Tnf-α after 48 hours compared to DTM-SCS and Sham-SCS. In summary, Con-SCS showed a shift of the inflammatory balance towards a pro-inflammatory state whilst HF- and DTM-SCS shifted the balance towards an anti-inflammatory state. These findings suggest that the underlying mechanism of Con-SCS induced pain relief in PDPN differs from that induced by HF- and DTM-SCS.

Spinal Cord Stimulation Paradigms and Pain Relief: A Preclinical Systematic Review on Modulation of the Central Inflammatory Response in Neuropathic Pain

OBJECTIVES

Spinal cord stimulation (SCS) is a last-resort treatment for patients with chronic neuropathic pain. The mechanism underlying SCS and pain relief is not yet fully understood. Because the inflammatory balance between pro- and anti-inflammatory molecules in the spinal nociceptive network is pivotal in the development and maintenance of neuropathic pain, the working mechanism of SCS is suggested to be related to the modulation of this balance. The aim of this systematic review is to summarize and understand the effects of different SCS paradigms on the central inflammatory balance in the spinal cord.

MATERIALS AND METHODS

A systematic literature search was conducted using MEDLINE, Embase, and PubMed. All articles studying the effects of SCS on inflammatory or glial markers in neuropathic pain models were included. A quality assessment was performed on predetermined entities of bias.

RESULTS

A total of 11 articles were eligible for this systematic review. In general, induction of neuropathic pain in rats results in a proinflammatory state and at the same time an increased activity/expression of microglial and astroglial cells in the spinal cord dorsal horn. Conventional SCS seems to further enhance this proinflammatory state and increase the messenger RNA expression of microglial markers, but it also results in a decrease in microglial protein marker levels. High-frequency and especially differential targeted multiplexed SCS can not only restore the balance between pro- and anti-inflammatory molecules but also minimize the overexpression/activation of glial cells. Quality assessment and risk of bias analysis of the studies included make it clear that the results of these preclinical studies must be interpreted with caution.

CONCLUSIONS

In summary, the preclinical findings tend to indicate that there is a distinct SCS paradigm-related effect in the modulation of the central inflammatory balance of the spinal dorsal horn.