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Spinal cord epidural electrical stimulation (EES) has been successfully employed to treat chronic pain and to restore lost functions after spinal cord injury. Yet, the efficacy of this approach is largely challenged by the suboptimal spatial distribution of the electrode contacts across anatomical targets, limiting the spatial selectivity of stimulation. In this study, we exploited different ESS paradigms, designed as either Spatial-Selective Stimulation (SSES) or Orientation-Selective Epidural Stimulation (OSES), and compared them to Conventional Monopolar Epidural Stimulation (CMES). SSES, OSES, and CMES were delivered with a 3- or 4-contact electrode array. Amplitudes and latencies of the Spinally Evoked Motor Potentials (SEMPs) were evaluated with different EES modalities. The results demonstrate that the amplitudes of SEMPs in hindlimb muscles depend on the orientation of the electrical field and vary between stimulation modalities. These findings show that the electric field applied with SSES or OSES provides more selective control of amplitudes of the SEMPs as compared to CMES. We demonstrate that spinal cord epidural stimulation applied with SSES or OSES paradigms in the rodent model could be tailored to the functional spinal cord neuroanatomy and can be tuned to specific target fibers and their orientation, optimizing the effect of neuromodulation.

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Background: Failed back surgery syndrome (FBSS) is a common and incapacitating condition affecting patients with previous spine surgery in whom treatment approach can be challenging. This study aimed to summarize existing secondary studies and up-to-date randomized clinical trials (RCTs) that assess the effectiveness of available treatment options for FBSS. Methods: Systematic searches were carried out in five databases (PubMed, Cochrane, Scielo, Epistemonikos, and Google scholar) for all systematic reviews on the effectiveness of treatment options for FBSS published after 2012. Outcomes of interest were pain levels measured through visual analog scale or numeric rating scale, Oswestry Disability Index, and quality of life. Methodological and risk of bias assessments were performed with the AMSTAR-2 tool for systematic reviews and the Joanna Briggs Institute checklist for RCT. Prospective PROSPERO registration: CRD42022307609. Results: Fifteen studies, seven systematic reviews, and eight RCTs met the inclusion criteria and fulfilled the methodological quality assessment. Of the 15 included studies, 8 were on neurostimulation, 4 on adhesiolysis, 4 on epidural or intrathecal injections, and 3 on other treatment modalities. The risk of bias was low in seven studies, moderate in five, and high in three. Conclusions: Based on this systematic overview and the considerable heterogeneity among studies, the FBSS therapeutic approach must be individualized. FBSS treatment should start with conservative management, considering the implementation of neurostimulation, a technique with the most robust evidence of effective results, in cases of refractory axial or neuropathic pain. As the last resource, in light of the evidence found, more invasive procedures or new surgical interventions are indicated.

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Neuropathic pain occurs in people experiencing lesion or disease affecting the somatosensorial system. It is present in 7 % of the general population and may not fully respond to first- and second-line treatments in up to 40 % of cases. Neuromodulation approaches are often proposed for those not tolerating or not responding to usual pharmacological management. These approaches can be delivered surgically (invasively) or non-invasively. Invasive neuromodulation techniques were the first to be employed in neuropathic pain. Among them is spinal cord stimulation (SCS), which consists of the implantation of epidural electrodes over the spinal cord. It is recommended in some guidelines for peripheral neuropathic pain. While recent studies have called into question its efficacy, others have provided promising data, driven by advances in techniques, battery capabilities, programming algorithms and software developments. Deep brain stimulation (DBS) is another well-stablished neuromodulation therapy routinely used for movement disorders; however, its role in pain management remains limited to specific research centers. This is not only due to variable results in the literature contesting its efficacy, but also because several different brain targets have been explored in small trials, compromising comparisons between these studies. Structures such as the periaqueductal grey, posterior thalamus, anterior cingulate cortex, ventral striatum/anterior limb of the internal capsule and the insula are the main targets described to date in literature. SCS and DBS present diverse rationales for use, mechanistic backgrounds, and varying levels of support from experimental studies. The present review aims to present their methodological details, main mechanisms of action for analgesia and their place in the current body of evidence in the management of patients with neuropathic pain, as well their particularities, effectiveness, safety and limitations.

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•Chronic spinal cord stimulation effectiveness was evaluated in four PD patients.•Double blinded cross over evaluation was performed using subthreshold stimulation.•An open label evaluation with regular suprathreshold stimulation was also performed.•No statistically significant effect was produced with either stimulation.•This study highlights the lack of strong clinical evidence supporting SCS for PD.

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BACKGROUND: The authors aim to describe a new technique for implantation of a spinal cord stimulation paddle lead sized over 10 mm through an endoscopic uniportal approach. A new endoscopic cannula was developed for the passage of a paddle lead width between 10 and 13 mm. The distal portion of the cannula was designed with a larger opening, providing better visibility of the anterior portion of the adjacent structures, thus allowing a panoramic view of the electrode passage. An electrode was implanted in an 11-mm paddle. OBSERVATIONS: After searching PubMed, Cochrane, and Lilacs databases, the authors found no mention of the implantation of a paddle electrode with a width greater than 10 mm. The implantation of a paddle electrode less than 10 mm wide is possible via endoscopic access using 10-mm working channels. However, for electrodes with a width greater than 10 mm, access via endoscopy is impossible, since the working channel is only 10 mm. LESSONS: The authors concluded that it is possible to pass electrodes safely and effectively with a paddle width between 10 and 13 mm using spinal endoscopy via uniportal interlaminar access. However, it is necessary to expand studies to elucidate this technique of endoscopic implantation of electrodes for neurostimulation.

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Objectives: This review aims to analyze the last years' experience of applying spinal cord stimulation (SCS) in complex regional pain syndrome (CRPS) patients with persistent or refractory chronic pain. Methods: This is a narrative review which was executed based on the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines and was carried out through the following databases: PUBMED and Cochrane Library. Also, a search for trials in the metaRegister of controlled trials (www.clinicaltrials.gov) was performed. Results: SCS provides pain reduction and improves sensory, vasomotor and sudomotor symptoms. It can reduce opioid using, offering better life quality for the patients. Conclusions: SCS found to be an excellent therapeutic alternative for patients with CRPS. It offers immediate pain relief and allows patients to regain functionality and have a better quality of life.

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Abstract The use of advanced invasive techniques for the control of chronic pain in patients with multiple comorbidities is becoming increasingly common. Neuromodulation offers a new management alternative involving the infusion of one or more drugs into the epidural or intrathecal space through a fully implantable infusion pump. It also involves spinal stimulation, a minimally invasive technique in which electrodes are positioned in the epidural space and connected to a pulse generator that is implanted subcutaneously and generates pulses designed to suppress the noxious stimulus. This article will describe the anesthetic considerations in cases of implantable drug delivery systems, and spinal and peripheral nerve stimulation devices. Additionally, patients with electrical or drug neuromodulation devices may present to anesthetic practice for surgical indications unrelated to their chronic pain pathology. Hence the importance of being familiar with the basic components of these devices, how they work, what drugs they use and the potential associated complications in the perioperative context, in order to ensure proper management and patient safety.

Resumen Cada vez es más común el empleo de técnicas invasivas avanzadas para el control del dolor crónico en paciente con múltiples comorbilidades. La neuro-modulación ofrece una nueva alternativa de manejo, que involucra la infusión de uno o más medicamentos en el espacio epidural o intratecal a través de una bomba de infusión totalmente implantable. También incluye la estimulación espinal, una técnica mínimamente invasiva que consiste en el posicionamiento de electrodos en el espacio epidural, conectados a un generador de pulso que se implanta subcutáneo y genera pulsos que buscan suprimir el estímulo nocivo. En este artículo se hará la descripción de las consideraciones anestésicas que se deben tener con sistemas de liberación de medicamentos implantables, dispositivos de estimulación medular y de nervio periférico. Adicionalmente, pueden aparecer pacientes portadores de dispositivos de neuromodulación eléctrica o medicamentosa que deben recibir anestesia para someterse a cirugía por razones diferentes a su patología de dolor crónico y deben conocerse sus implicaciones anestésicas. Por lo anterior, es importante conocer y estar familiarizados con los componentes básicos de dichos dispositivos: funcionamiento, medicamentos que utilizan y las potenciales complicaciones que se puedan tener con estos en el contexto perioperatorio, para garantizar un manejo adecuado y la seguridad del paciente.

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BACKGROUND: Spinal cord stimulation (SCS) is traditionally performed by implanting surgical leads along the midline of the spinal cord, over the dorsal columns. Here, we present a patient who successfully underwent lateral cervical SCS to treat chronic refractory neuropathic pain. METHODS: A 46-year-old female, with a schwannoma involving the right axillary nerve, presented with a chronic refractory right upper extremity pain syndrome. The tumor was located between the fibers of the teres minor and the posterior deltoid, and measured 2.2 cm in diameter. After 8 months of analgesics, opioids, physiotherapy, and acupuncture, the patient underwent surgery; however, the tumor was unresectable (i.e., due to significant adjacent vascular/neural structures). Three months later, she had a midline C6-C7 laminectomy for placement of a right-sided epidural SCS lead (i.e., containing 16 electrode contacts). RESULTS: Within 4 days following this SCS procedure, the patient's pain completely resolved; at 10 postoperative months, she still remains pain free. CONCLUSION: Lateral SCS at the C6-C7 level provided a safe and effective option for the relief of chronic neuropathic pain attributed to an unresectable schwannoma of the right axillary nerve in a 46-year-old female.

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Abstract Introduction Neuropathic pain is present in up to 40 % of all cancer patients. A considerable number of patients fail to achieve enough pain relief with conventional treatment, which is why therapeutic alternatives such as spinal cord stimulation should be considered. Case description and results This is the case of a female patient with chronic neuropathic pain secondary to a partial femoral nerve injury sustained during resection and lymph node dissection surgery with curative intent for a large stage II cell squamous cell carcinoma T2N0M0, localized in the right popliteal fossa. The patient presented with difficult to manage chronic neuropathic pain, despite receiving multiple oral analgesics and nerve blocks. A medullary neurostimulator was implanted that relieved the patient's pain intensity in up to 80%, in addition to improved function and quality of life. Conclusions Spinal cord stimulation is considered an effective neuromodulatory intervention which has shown satisfactory results in the treatment of various types of refractory chronic pain in cancer patients, including neuropathic pain.

Resumen Introducción El dolor neuropático está presente hasta en el 40 % de los pacientes con cáncer. Un número considerable de pacientes no logran un alivio suficiente del dolor con el tratamiento convencional, por lo cual deben considerarse alternativas terapéuticas como la estimulación de la médula espinal. Descripción del caso y resultados Caso de una paciente con dolor neuropático crónico secundario a lesión parcial de nervio femoral durante cirugía de resección y vaciamiento ganglionar con objetivos curativos de carcinoma escamocelular de célula grande T2N0M0 estadio II, localizado en la fosa poplítea derecha, quien cursó con dolor neuropático crónico de difícil manejo a pesar de recibir múltiples analgésicos orales y bloqueos nerviosos. Se implantó un neuroestimulador medular con lo cual se logró un alivio hasta del 80 % en intensidad de dolor de la paciente, además de una mejoría de su funcionalidad y calidad de vida. Conclusiones La estimulación de la médula espinal se considera una intervención neuromoduladora eficaz, que ha demostrado resultados satisfactorios para tratar diversas formas de dolor crónico refractario en los pacientes con cáncer, incluido el dolor neuropático.

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INTRODUCTION: Hereditary spastic paraplegia is a heterogeneous group of genetic disorders characterized by degeneration of the corticospinal tracts, coursing with progressive weakness and spasticity of the lower limbs. To date, there are no effective treatments for progressive deficits or disease-modifying therapy for those patients. We report encouraging results for spastic paraparesis after spinal cord stimulation. METHODS: A 51-year-old woman suffering from progressive weakness and spasticity in lower limbs related to hereditary spastic paraplegia type 4 underwent spinal cord stimulation (SCS) and experienced also significant improvement in motor function. Maximum ballistic voluntary isometric contraction test, continuous passive motion test and gait analysis using a motion-capture system were performed in ON and OFF SCS conditions. Neurophysiologic assessment consisted of obtaining motor evoked potentials in both conditions. RESULTS: Presurgical Spastic Paraplegia Rating Scale (SPRS) score was 26. One month after effective SCS was initiated, SPRS went down to 15. At 12 months follow up, she experienced substantial improvement in motor function and in gait performance, with SPRS scores 23 (OFF) and down to 20 (ON). There was an increased isometric muscle strength (knee extension, OFF: 41 N m; ON: 71 N m), lower knee extension and flexion torque values in continuous passive motion test (decrease in spastic tone) and improvement in gait (for example, step length increase). CONCLUSION: Despite being a case study, our findings suggest innovative lines of research for the treatment of spastic paraplegia.

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Dopaminergic drugs partially alleviate gait problems in Parkinson's disease, but the effects are not sustained in the long-term. Particularly, the freezing of gait directly impacts patients' quality of life. Experimental epidural spinal cord stimulation (SCS) studies have suggested positive effects on locomotion among PD patients, but the effects of non-invasive stimulation have never been explored. Here, we investigated in a prospective, open-label, pilot study the efficacy and safety of non-invasive magnetic stimulation of the spinal cord in five patients with PD who experienced gait problems, including freezing of gait. A trial of transcutaneous magnetic SCS was performed at the level of the fifth thoracic vertebra. The primary outcome was the change in freezing of gait 7 days after stimulation. Secondary outcome measures included changes in gait speed and UPDRS part III. After non-invasive spinal cord stimulation, patients experienced a 22% improvement in freezing of gait (p = 0.040) and 17.4% improvement in the UPDRS part III (p = 0.042). Timed up and go times improved by 48.2%, although this did not reach statistical significance (p = 0.06). Patients' global impression of change was 'much improved' for four patients. Improvement in gait after stimulation was reversible, since it returned to baseline scores 4 weeks after stimulation. No severe side effects were recorded. This pilot study suggests that transcutaneous magnetic spinal cord stimulation is feasible and can potentially improve gait problems in PD, without severe adverse effects. Large scale phase II trials are needed to test this hypothesis.

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BACKGROUND: Current available therapies for Parkinson disease (PD) have strong limitations, and patients usually present with refractory symptoms despite all efforts. Deep brain stimulation (DBS), which has been used in PD patients for decades (since 1987), has best indications for symptoms like tremor, motor fluctuations, or dyskinesia. However, postural instability and gait disturbances (PIGD) have restricted benefits with DBS. In 2009, spinal cord stimulation (SCS), a well-established therapy for chronic pain, has emerged as a potential alternative therapy that may help control unresponsive symptoms such as bradykinesia, PIGD, and freezing of gait. METHODS: The main studies regarding SCS in PD are reviewed here from the first studies in animal models to the latest clinical trials. CONCLUSIONS: Despite promising findings, the heterogeneity of methodologies used and small samples in human studies pose a challenging problem to be addressed in order to have robust clinical evidence to support SCS as a viable PD treatment.

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Colorectal cancer is one of the most common oncological diseases. Chemotherapy is usually recommended as an adjuvant treatment for stage-II, -III, and -IV tumors. Approximately 10% of the patients develop neuropathic pain after chemotherapy, and they may remain refractory despite the administration of drugs that are commonly used to treat neuropathic pain. Spinal cord stimulation is a good treatment option for neuropathic pain of the lower limbs, and it should be trialed in patients with chemotherapy-induced peripheral neuropathy. We report the case of a patient with oxaliplatin-induced neuropathy and neuropathic pain refractory to oral medication who was successfully treated by spinal cord stimulation.

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BACKGROUND: Transcutaneous electrical nerve stimulation (TENS), manual acupuncture (MA), and spinal cord stimulation (SCS) are used to treat a variety of pain conditions. These non-pharmacological treatments are often thought to work through similar mechanisms, and thus should have similar effects for different types of pain. However, it is unclear if each of these treatments work equally well on each type of pain condition. The purpose of this study was to compared the effects of TENS, MA, and SCS on neuropathic, inflammatory, and non-inflammatory pain models. METHODS: TENS 60 Hz, 200 µs, 90% motor threshold (MT), SCS was applied at 60 Hz, an intensity of 90% MT, and a 0.25 ms pulse width. MA was performed by inserting a stainless-steel needle to a depth of about 4-5 mm at the Sanyinjiao (SP6) and Zusanli (ST36) acupoints on a spared nerve injury (SNI), knee joint inflammation (3% carrageenan), and non-inflammatory muscle pain (intramuscular pH 4.0 injections) in rats. Mechanical withdrawal thresholds of the paw, muscle, and/or joint were assessed before and after induction of the pain model, and daily before and after treatment. RESULTS: The reduced withdrawal thresholds were significantly reversed by application of either TENS or SCS (P < 0.05). MA, on the other hand, increased the withdrawal threshold in animals with SNI and joint inflammation, but not chronic muscle pain. CONCLUSIONS: TENS and SCS produce similar effects in neuropathic, inflammatory and non-inflammatory muscle pain models while MA is only effective in inflammatory and neuropathic pain models.

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Spinal cord stimulation (SCS) has been used for the treatment of chronic pain for nearly five decades. With a high degree of efficacy and a low incidence of adverse events, it is now considered to be a suitable therapeutic alternative in most guidelines. Experimental studies suggest that SCS may also be used as a therapy for motor and gait dysfunction in parkinsonian states. The most common and disabling gait dysfunction in patients with Parkinson's disease (PD) is freezing of gait (FoG). We review the evolution of SCS for gait disorders from bench to bedside and discuss potential mechanisms of action, neural substrates, and clinical outcomes.

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Spinal cord stimulation (SCS) has been described as a valuable neuromodulator procedure in the management of chronic medically untreated neuropathic pain. Although the use of this technique has been published in many papers, a question still remains regarding its applicability in pregnant patients. The goal of this paper is to discuss the risks, complications, and results as well as the prognosis of SCS in pregnant patients. We performed a systematic review from 1967 to 2018 using the databases MEDLINE, LILACS, SciELO, PubMed, and BIREME, utilizing language as selection criteria. Eighteen studies that met our criteria were found and tabulated. SCS is a reversible and adjustable surgical procedure, which results in patients that demonstrated a significant effect in the reduction of pain intensity in pregnant patients. The etiologies most frequent were complex regional pain and failed back pain syndromes, which together represented 94% of analyzed cases. The technical complications most frequent were lead migration (3%, n = 1). Regarding the risks, the authors did not show significative factors among the categorical variables that can suggest a teratogenicity, while the maternal risks have been associated to the consequences of technical complications due to, among other factors, improvement of abdominal pressure during pregnancy and delivery. Finally, although there are not significative cohorts of pregnant patients, the procedure is still an effective surgical approach of neuropathic pain associated to lower rates of complications and significative improvement in the quality of life of patients during pregnancy.

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OBJECTIVES: Previous studies demonstrated significant improvement in mean pain scores and quality of life (QOL) scales in patients with chronic pain who underwent spinal cord stimulation (SCS). However, the number of individuals who experience relevant improvements in QOL, termed the meaningful clinical improvement (MCI), is not known. The present study investigated changes in pain measurements based on MCI after SCS. MATERIALS AND METHODS: Thirty-four patients with chronic intractable pain completed scales of pain (visual analogue scale [VAS]), QOL (SF-36), and psychological dimensions during a 22-month follow-up period (mean). Patient-centered MCI of the VAS and SF-36 domain scores were determined based on the MacNab criteria of surgical global effectiveness. Independent presurgical predictors for MCI in the VAS and SF-36 domains were analyzed using multiple binary logistic regression. RESULTS: There was significant improvement of pain and QOL after the SCS (p < 0.00001). Twenty-three patients (67.6%) reached an MCI of pain, and 16 (47.7%)-23 (67.7%) reported an MCI of QOL. Predictors of MCI included ≥80% paresthesia coverage of the painful area, lower levels of anxiety and catastrophizing symptoms, shorter pain duration, female gender and no use of opioids before surgery. MCI of pain and QOL was observed in 50%-70% of patients with chronic pain after SCS. CONCLUSIONS: The identification of determinants for MCI is a challenge to improve the accuracy of prognostic models in SCS for patients with chronic pain. Our results, if confirmed in other populations with a larger sample size, have implications for patients with chronic pain who are candidates for SCS treatment.

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ABSTRACT Objective: Fail back surgery syndrome (FBSS) is a common cause of pain following spine surgery, and is associated with persistent or recurrent pain despite anatomically correct intervention. Spinal cord stimulation (SCS) is regarded as one of the most effective methods of treatment for fail back surgery syndrome. Methods: We studied 34 patients who underwent test stimulation and chronic SCS for FBSS. Results: Six months postoperatively, mean improvement by the visual analog scale (VAS) of average and maximum daily pain, and the painDETECT score, were 54.4%, 50.7% and 57.3%, respectively. This meets the criteria for effectiveness of the method, according to the literature. Most of patients reported significant improvements in life quality and less need for analgesics. Complications were seen in nine patients (26.4%) and included: intraoperative dura injury (one patient, 2.9%), wound infection (one patient, 2.9%), and electrode displacement (seven patients, 20.5%). No cases of postoperative neurological deterioration were seen. Conclusions: SCS is safe and effective for the treatment of neuropathic pain caused by FBSS. Level of Evidence IV; Case series.

RESUMO Objetivos: A síndrome da cirurgia de falência reversa (SAF) é uma causa comum de dor após cirurgia de coluna e associada a dor persistente ou recorrente, apesar da intervenção anatomicamente correta. Estimulação da medula espinhal (SCS) é considerado como um dos métodos mais eficazes de tratamento para a síndrome de cirurgia de retorno. Métodos: Foram estudados 34 pacientes submetidos a estimulação de teste e SCS crônica para FBSS. Resultados: 6 meses de pós-operatório melhora a média de dor diária média e máxima diária na escala análoga visual (VAS), bem como a pontuação do PainDetect foram de 54,4%, 50,7% e 57,3%, respectivamente. Ele atende aos critérios de eficácia do método, de acordo com a literatura. A maioria dos pacientes relatou melhora significativa da qualidade de vida e menor necessidade de analgésicos. As complicações foram observadas em nove pacientes (26,4%) e incluíram: lesão da dura-máter intraoperatória (um paciente, 2,9%), infecção da ferida (um paciente, 2,9%), deslocamento do eletrodo (sete pacientes, 20,5%). Não houve casos de deterioração neurológica no pós-operatório. Conclusões: A SCS é segura e eficaz para o tratamento da dor neuropática causada pela FBSS. Nível de Evidência IV; Séries de casos.

RESUMEN Objetivo: El síndrome de cirugía de espalda fallida (FBSS) es una razón común para el dolor después de la cirugía de la columna vertebral y se asocia con dolor persistente o recurrente a pesar de la intervención anatómicamente correcta. La estimulación de la médula espinal (SCS) se considera uno de los métodos de tratamiento más eficaces para el síndrome de cirugía de espalda fallida. Métodos: Se estudiaron 34 pacientes que se sometieron a estimulación de prueba y SCS crónica para FBSS. Resultados: A los seis meses la mejora promedio postoperatoria por la escala visual análoga (EVA) del dolor diario promedio y máximo diario, así como el puntaje de painDETECT fueron 54,4%, 50,7% y 57,3%, respectivamente. Esto cumple con los criterios de efectividad del método, según la literatura. La mayoría de los pacientes informaron una mejoría significativa de la calidad de vida y una menor necesidad de analgésicos. Las complicaciones se observaron en nueve pacientes (26,4%) e incluyeron: lesión duramadre intraoperatoria (uno paciente, 2,9%), infección de la herida (uno paciente, 2,9%), desplazamiento del electrodo (siete pacientes, 20,5%). No se observaron casos de deterioro neurológico postoperatorio. Conclusiones: SCS es seguro y efectivo para el tratamiento del dolor neuropático causado por FBSS. Nivel de Evidencia IV; Series de casos.

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