Dorsal column stimulator applications

A single-center real-world review of 10 kHz high-frequency spinal cord stimulation outcomes for treatment of chronic pain

Objective

To compare pragmatic real-world 10-kHz high-frequency spinal cord stimulation (HF-SCS) outcomes at a single academic center to the industry-sponsored SENZA-RCT and Stauss et al. study.

Methods

This single-center retrospective study included patients with refractory back or limb pain trialed and/or permanently implanted with the Nevro HF-SCS system from 2016 to 2021. Demographic and outcome data were obtained from the electronic medical record (EMR) and real-world global database maintained by Nevro Corp. Data obtained from the global database were confirmed using the EMR. Main outcome measures included positive responder status (≥50% patient-reported percentage pain reduction (PRPPR)), improvement in function, improvement in sleep, and reduction in pain medication usage. Comparison groups included patient outcomes from the SENZA-RCT and Stauss et al. study.

Results

Patients (N = 147) trialed with HF-SCS were reviewed, with data available for 137. Positive trialed patient responder rate (≥50% PRPPR) was 77% (106/137, 95CI 70-84%) vs. 87% (1393/1607, 95CI 85-89%) Stauss et al. vs. 93% (90/97, 95CI 88-98%) SENZA-RCT HF-SCS. At the last available follow-up, positive implanted patient responder rate was 73% (58/80, 95CI 63-82%) vs. 78% (254/326, 95CI 73-82%) Stauss et al. vs. 79% (71/90, 95CI 70-87%) SENZA-RCT HF-SCS. Sixty-seven percent (59/88, 95CI 57-77%) reported improved function vs. 72% (787/1088, 95CI 70-75%) Stauss et al.; 45% (31/69, 95CI 33-57%) reported improved sleep vs. 68% (693/1020, 95CI 65-71%) Stauss et al. and 16% (9/56, 95CI 6-26%) reported decrease in medication use vs. 32% (342/1070, 95CI 29-35%) Stauss et al.

Conclusion

Patient responder rates in this retrospective pragmatic real-world study of HF-SCS are consistent with previous industry-sponsored studies. However, improvements in quality-of-life measures and reduction in medication usage were not as robust as reported in industry-sponsored studies. The findings of this non-industry-sponsored, independent study of HF-SCS complement those of previously published studies by reporting patient outcomes collected in the absence of industry sponsorship.

Effects of short-term spinal cord stimulation on patients with prolonged disorder of consciousness: A pilot study

Background

Spinal cord stimulation (SCS) can improve the level of awareness of prolonged disorder of consciousness (pDOC), but its application is restricted due to damage of invasive operation. Short-term spinal cord stimulation (st-SCS) in a minimally invasive manner will better balance the benefits and risks.

Objectives

This study focuses on the safety and efficacy of st-SCS for pDOC and reveals the modulation characteristics of different frequencies of SCS.

Methods

31 patients received 2-week st-SCS treatment and 3-months follow-up. All patients were divided into two types of frequency treatment groups of 5 Hz and 70 Hz according to the postoperative electroencephalography (EEG) test. The efficacy was assessed based on the revised coma recovery scale (CRS-R).

Results

The results showed a significant increase in CRS-R scores after treatment (Z = −3.668, p < 0.001) without significant adverse effects. Univariate analysis showed that the minimally conscious state minus (MCS–) benefits most from treatment. Furthermore, two frequency have a difference in the time-point of the CRS-R score increase. 5 Hz mainly showed a significant increase in CRS-R score at 2 weeks of treatment (p = 0.027), and 70 Hz additionally showed a delayed effect of a continued significant increase at 1 week after treatment (p = 0.004).

Conclusion

st-SCS was safe and effective in improving patients with pDOC levels of consciousness, and was most effective for MCS–. Both 5 Hz and 70 Hz st-SCS can promote consciousness recovery, with 70 Hz showing a delayed effect in particular.

Long-term functional prognosis and related factors of spinal cord stimulation in patients with disorders of consciousness

INTRODUCTION

The treatment of patients with disorders of consciousness (DoC) remains a challenging issue, and spinal cord stimulation (SCS) has been reported to be a promising treatment for DoC in some studies.

AIMS

This study explores the efficiency of SCS in treating patients with DoC at different consciousness levels, including the vegetative state/unresponsive wakefulness syndrome (VS/UWS) and the minimally conscious state (MCS) and summarizes and analyzes the long-term effect and related factors of SCS in patients with DoC.

RESULTS

An overall positive outcome was reached in 35 of 110 patients (31.8%). Among patients with positive outcomes, the MCS group improved 45.53% more than VS/UWS group, and this difference was statistically significant. In terms of the recommendation standard, positive outcomes occurred in 33 patients (94.3%) in the highly recommended group and 2 patients (5.7%) in the weakly recommended group (p < 0.001). After adjustment for potential covariables, young age (age ≤ 19 years old) (p = 0.045) and MCS (p < 0.001) were significantly correlated with positive outcome. A nomogram based on age, state of consciousness, and pathogeny showed good predictive performance, with a c-index of 0.794. The Hosmer-Lemeshow goodness-of-fit test showed that the model was well calibrated (χ²  = 3.846, p = 0.871).

CONCLUSIONS

SCS is one of the most feasible treatments for patients with DoC, especially for patients with MCS. Younger age is significantly associated with better outcomes and could therefore serve as a basis for preoperative screening. However, more evidence-based randomized controlled trials are needed to confirm the efficacy of the treatment.

Pre-Operative Assessment of Patients Undergoing Spinal Cord Stimulation for Refractory Angina Pectoris

Spinal cord stimulation (SCS) is used to treat a variety of chronic pain conditions refractory to more conservative management including refractory angina pectoris. We identified 31 patients who underwent SCS implantation for the indication of refractory angina at a single institution from 2003 through 2018. Sixteen patients were male, and 15 were female. Average age was 53.9 years. Prior to SCS implantation, all patients had at least one coronary angiogram. Ten (32.3%) patients had undergone percutaneous coronary intervention, and four (12.9%) had undergone coronary artery bypass grafting. Thirty patients (96.7%) were currently using anti-angina medications. Twenty-six patients (83.9%) were on antiplatelet or anticoagulant agents at the time of SCS evaluation. Spinal cord stimulation implanters must perform a comprehensive evaluation incorporating appropriate multidisciplinary care particularly in patients with refractory angina given their cardiovascular comorbidities. It is important to have baseline data (e.g., pain scores, nitroglycerin consumption, frequency of angina episodes, and a questionnaire, such as the Seattle Angina Questionnaire) to compare with follow-up data to help define treatment success. We report a single institution's pre-operative experience for patients undergoing SCS for refractory angina to illustrate unique pre-operative SCS considerations in this chronic pain population.

Neuro-Immune Modulation Effects of Sacral Nerve Stimulation for Visceral Hypersensitivity in Rats

Background: Visceral hypersensitivity (VH) is one of the underlying pathophysiologies of irritable bowel syndrome. Mast cell overactivation has been found to be one of the main causes of VH. We investigated the effects and mechanisms of actions of sacral nerve stimulation (SNS) on visceral pain in a rodent model of VH.

Methods: The VH was established by an intrarectal infusion of AA in 10-day-old pups. Rats were chronically implanted with electrodes for SNS and recording electromyogram (EMG) and electrocardiogram. The acute study was performed in 2-randomized sessions with SNS (14 Hz, 330 μs, 40% motor threshold or MT, 30 min) or sham-SNS. Later on, rats were randomized into SNS/sham-SNS groups and a chronic study was performed with 2 h-daily SNS or sham-SNS for 21 days. Visceromotor reflexes were assessed by abdominal EMG and withdrawal reflex (AWR). Colon tissues were collected to study colonic acetylcholine (ACh), the enteric neurons (ChAT, nNOS, and PGP9.5), mast cells activity [Tryptase, prostaglandins E2 (PGE2), and cyclooxygenases-2 (COX2)] and pain markers [nerve growth factor (NGF) and Sub-P].

Key Results: Sacral nerve stimulation significantly improved visceromotor reflexes assessed by the EMG and AWR, compared with sham-SNS. SNS normalized the protein expressions of ChAT and nNOS and regulated mast cells activity by downregulating Tryptase, COX2, and PGE2. Neonatal AA administration upregulated NGF and Sub-P; chronic SNS significantly decreased these pain biomarkers. Concurrently, chronic SNS increased ACh in colon tissues and vagal efferent activity.

Conclusions: Sacral nerve stimulation reduces VH in rats and this ameliorating effect might be attributed to the suppression of mast cell overactivation in the colon tissue via the modulation of autonomic nervous system functions.

On the Right Track to Treat Movement Disorders: Promising Therapeutic Approaches for Parkinson's and Huntington's Disease

Movement disorders are neurological conditions in which patients manifest a diverse range of movement impairments. Distinct structures within the basal ganglia of the brain, an area involved in movement regulation, are differentially affected for every disease. Among the most studied movement disorder conditions are Parkinson's (PD) and Huntington's disease (HD), in which the deregulation of the movement circuitry due to the loss of specific neuronal populations in basal ganglia is the underlying cause of motor symptoms. These symptoms are due to the loss principally of dopaminergic neurons of the substantia nigra (SN) par compacta and the GABAergic neurons of the striatum in PD and HD, respectively. Although these diseases were described in the 19th century, no effective treatment can slow down, reverse, or stop disease progression. Available pharmacological therapies have been focused on preventing or alleviating motor symptoms to improve the quality of life of patients, but these drugs are not able to mitigate the progressive neurodegeneration. Currently, considerable therapeutic advances have been achieved seeking a more efficacious and durable therapeutic effect. Here, we will focus on the new advances of several therapeutic approaches for PD and HD, starting with the available pharmacological treatments to alleviate the motor symptoms in both diseases. Then, we describe therapeutic strategies that aim to restore specific neuronal populations or their activity. Among the discussed strategies, the use of Neurotrophic factors (NTFs) and genetic approaches to prevent the neuronal loss in these diseases will be described. We will highlight strategies that have been evaluated in both Parkinson's and Huntington's patients, and also the ones with strong preclinical evidence. These current therapeutic techniques represent the most promising tools for the safe treatment of both diseases, specifically those aimed to avoid neuronal loss during disease progression.

Sacral nerve stimulation with optimized parameters improves visceral hypersensitivity in rats mediated via the autonomic pathway

The purpose of this study was to determine effects and mechanisms of sacral nerve stimulation (SNS) on visceral hypersensitivity in rodent models of colonic hypersensitivity. SNS was performed with different sets of parameters for 30 min in six regular rats. Visceral sensitivity was assessed by the measurement of electromyogram and abdominal withdrawal reflex before and after SNS. Real/sham SNS with optimized parameters was performed in 8 restraint stress-induced visceral hypersensitivity rats and 10 neonatal acetic acid-treated colonic hypersensitivity rats; acute effect of SNS was assessed by comparing electromyogram and heart rate variability. Neonatal acetic acid-treated rats were treated by SNS (n = 10) or sham-SNS (n = 10) daily for seven days for the assessment of the chronic effect of SNS. (1) When the stimulation amplitude was reduced from 90% of motor threshold to 65% or 40% motor threshold, SNS with certain parameters showed an inhibitory effect on abdominal withdrawal reflex. The best stimulation parameters for SNS were “14 Hz, 330 µs, and 40% motor threshold.” (2) SNS significantly reduced visceral hypersensitivity and improved autonomic function in restraint stress-induced rats. The inhibitory effect was blocked by naloxone. (3)Acute and chronic SNS significantly reduced visceral hypersensitivity and improved autonomic function in acetic acid-treated rats. SNS with reduced stimulation strength may be used to treat colonic hypersensitivity and the best stimulation parameters seem to be “14 Hz, 330 µs and 40% motor threshold”. SNS with optimized parameters improved visceral hypersensitivity in rodent models of colonic hypersensitivity mediated via the autonomic and opioid mechanisms.

Long-Range Temporal Correlations of Patients in Minimally Conscious State Modulated by Spinal Cord Stimulation

Spinal cord stimulation (SCS) has been shown to improve the consciousness levels of patients with disorder of consciousness (DOC). However, the underlying mechanisms of SCS remain poorly understood. This study recorded resting-state electroencephalograms (EEG) from 16 patients with minimally conscious state (MCS), before and after SCS, and investigated the mechanisms of SCS on the neuronal dynamics in MCS patients. Detrended fluctuation analysis (DFA), combined with surrogate data method, was employed to measure the long-range temporal correlations (LRTCs) of the EEG signals. A surrogate data method was utilized to acquire the genuine DFA exponents (GDFAE) reflecting the genuine LRTCs of brain activity. We analyzed the GDFAE in four brain regions (frontal, central, posterior, and occipital) at five EEG frequency bands [delta (1-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), beta (13-30 Hz), and gamma (30-45 Hz)]. The GDFAE values ranged from 0.5 to 1, and showed temporal and spatial variation between the pre-SCS and the post-SCS states. We found that the channels with GDFAE spread wider after SCS. This phenomenon may indicate that more cortical areas were engaged in the information integration after SCS. In addition, the GDFAE values increased significantly in the frontal area at delta, theta, and alpha bands after SCS. At the theta band, a significant increase in GDFAE was observed in the occipital area. No significant change was found at beta or gamma bands in any brain region. These findings show that the enhanced LRTCs after SCS occurred primarily at low-frequency bands in the frontal and occipital regions. As the LRTCs reflect the long-range temporal integration of EEG signals, our results indicate that information integration became more "complex" after SCS. We concluded that the brain activities at low-frequency oscillations, particularly in the frontal and occipital regions, were improved by SCS.

Current Status of Neuromodulatory Therapies for Disorders of Consciousness

Treatment for disorders of consciousness (DOCs) is still a Gordian knot. Evidence-based guidelines on the treatment of DOC patients are not currently available, while neuromodulation techniques are seen as a potential treatment. Multiple neuromodulation therapies have been applied. This article reviews the most relevant studies in the literature in order to describe a clear picture of the current state of neuromodulation therapies that could be used to treat DOC patients. Both invasive and non-invasive brain stimulation is discussed. Significant behavioral improvements in prolonged DOCs under neuromodulation therapies are rare. The efficacy of various such therapies remains a matter of debate. Further clinical investigations of existing techniques in larger samples properly controlling for spontaneous recovery are needed, and new approaches are awaited.

Spinal Cord Stimulator Electrode Dislodging into the Ligamentum Flavum: A Case Report

To date, no case studies specifically reporting an electrode dislodging from its lead wire have been reported. Here we describe a case involving an electrode shearing from the spinal cord stimulator lead, and lodging into the ligamentum flavum during implantation. In this case, an experienced board certified interventional pain management specialist was performing the implantation procedure of a magnetic resonance imaging (MRI) compatible spinal cord stimulator with MR conditional leads. After successful placement of the first lead, the epidural space was accessed via a T11/12 interlaminar approach using loss of resistance technique. When the lead would not advance past the tip of the needle, it was removed in order to reposition the needle slightly. Upon removal of the lead, it was discovered that the first electrode was no longer attached to the wire. Subsequent fluoroscopic imaging revealed that the electrode had lodged within the ligamentum flavum. Upon discussion with the medical director of the device company, it was agreed upon that the electrode should be left in place. The decision was made to proceed with only one lead in place and the remainder of the procedure was completed uneventfully. The patient followed up two weeks later in clinic, and no adverse effect related to the dislodged electrode was reported. The indications and common complications associated with spinal cord stimulation are discussed, followed by factors to consider to help guide decision making in the event of a retained foreign body during a procedure.

Influence of inter-stimulus interval of spinal cord stimulation in patients with disorders of consciousness: A preliminary functional near-infrared spectroscopy study

Spinal cord stimulation (SCS) is a promising treatment for disorders of consciousness (DOC), but the underlying mechanism and most effective procedures remain uncertain. To optimize the protocol, previous studies evaluated the frequency-specific effects of SCS on neurophysiological activities. However, whether and how the inter-stimulus interval (ISI) parameter affects the SCS neuromodulation in DOC remains unknown. We enrolled nine DOC patients who had implanted SCS devices and conducted three different durations of ISIs. Using functional near-infrared spectroscopy (fNIRS), we monitored the blood volume fluctuations in the prefrontal and occipital cortices during the SCS. The results showed that short stimuli (30 s) induced significant cerebral blood volume changes, especially in the prefrontal cortex, an important area in the consciousness system. By comparing the mean value of the responses from the first and the last block in each session, a shorter ISI was found to improve the blood volume in the prefrontal cortex. This phenomenon was more significant for the subgroup of patients with a favorable prognosis. These preliminary results imply that the ISI may be an important factor for SCS. The research paradigm proposed here also provides insights for further quantitative evaluations of the therapeutic effects of neuromodulation.

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Spinal cord stimulation rapidly evokes activity in consciousness-related brain areas.

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Inter-stimulus interval of neuromodulation is important for treating disorders of consciousness.

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Shorter inter-stimulus interval can better improve the blood volume in frontal area.

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Near-infrared spectroscopy is feasible for evaluating neuromodulation effects.

Frontal Connectivity in EEG Gamma (30-45 Hz) Respond to Spinal Cord Stimulation in Minimally Conscious State Patients

Spinal cord stimulation (SCS) has become a valuable brain-intervention technique used to rehabilitate patients with disorders of consciousness (DOC). To explore how the SCS affects the cerebral cortex and what possible electrophysiological mechanism of SCS effects on the cortex, the present study investigated the functional connectivity and network properties during SCS in minimally conscious state (MCS) patients. MCS patients received both SCS and sham sessions. Functional connectivity of the phase lock value (PLV) in the gamma band (30-45 Hz) was investigated at the pre-, on- and post-SCS stages. In addition, to evaluate global network properties, complex network parameters, including average path length, cluster coefficient and small-world, were measured. When SCS was turned on, significantly decreased connectivity was noted in the local scale of the frontal-frontal region and in the large scales of the frontal-parietal and frontal-occipital regions. The global network showed fewer small-world properties, average path lengths increased and cluster coefficients decreased. When SCS was turned off, the large-scale connectivity and global network returned to its pre-SCS level, but the local scale of frontal-frontal connectivity remained significantly lower than its pre-SCS level. Sham sessions produced no significant changes in either functional connectivity or network. The findings directly showed that SCS could effectively intervene cortical gamma activity, and the intervention included immediate global effects (large scale connectivity and network alteration only occurred in stimulation period) and long-lasting local effects (local scale connectivity alteration persist beyond stimulation period). Moreover, considering the mechanism and propagation of gamma activity, it indicates that the frontal cortex plays a crucial role in the SCS effects on the cerebral cortex.

Dorsal Column Stimulation vs. Dorsal Root Ganglion Stimulation for Complex Regional Pain Syndrome Confined to the Knee: Patients' Preference Following the Trial Period

BACKGROUND AND OBJECTIVES

Patients with complex regional pain syndrome (CRPS) confined to the knee are often therapy resistant. Neurostimulation is an accepted treatment for CRPS. Although results with dorsal column (DC) stimulation in patients with CRPS confined to the knee are often disappointing, the availability of dorsal root ganglion (DRG) stimulation may provide new opportunities for this complaint. Therefore, this study explores patients' preference for DC stimulation vs. DRG stimulation in treating chronic pain due to CRPS confined to the knee.

METHODS

A prospective, observational crossover cohort study was conducted comparing 2 methods of neurostimulation, in randomized order, in patients with CRPS confined to the knee. After receiving DC and DRG stimulation during a trial period of 16 days, patients were asked which of the 2 methods they preferred. Patients with a successful trial period with one or both stimulation methods received a fully implantable system.

RESULTS

Twelve patients were included. After finishing the trial period, 10 patients (83.3%) preferred DRG stimulation and 2 (16.7%) preferred DC stimulation (P = 0.04).

CONCLUSION

To our knowledge, this is the first study to compare these 2 neurostimulation methods in patients with CRPS confined to the knee. Results show that the probability of the preference for either neurostimulation treatment significantly deviates from chance in favor of DRG stimulation.

Spinal cord stimulation modulates frontal delta and gamma in patients of minimally consciousness state

Spinal cord stimulation (SCS) has been suggested as a therapeutic technique for treating patients with disorder of consciousness (DOC). Although studies have reported its benefits for patients, the underlying pathophysiological mechanisms remain unclear. The aim of this study was to measure the effects of SCS on the EEG of patients in a minimally conscious state (MCS), which would allow us to explore the possible workings underpinning of the approach. Resting state EEG was recorded before and immediately after SCS, using various frequencies (5Hz, 20Hz, 50Hz, 70Hz and 100Hz), for 11 patients in MCS. Relative power, coherence, S-estimator and bicoherence were calculated to assess the EEG changes. Five frequency bands (delta, theta, alpha, beta and gamma) and three regions (frontal, central and posterior) were divided in the calculation. The main findings of this study were that: (1) significantly altered relative power and synchronisation was found in delta and gamma bands after one SCS stimulation using 5Hz, 70Hz or 100Hz; (2) bicoherence showed that coupling within delta was significantly decreased after stimulation using 70Hz, while reduction of coupling between delta and gamma was found when using 5Hz and 100Hz. However, SCS of 20Hz, 50Hz and sham stimulation did not induce changes in any frequency band at any region. This study showed EEG evidence that SCS can modulate the brain function of MCS patients, speculatively by activating the formation-thalamus-cortex network.

Intraoperative electrophysiological monitoring for C1-2 spinal cord stimulation

OBJECTIVE This study is a retrospective case series involving C1-2 spinal cord stimulation in patients with complex regional pain syndrome (CRPS) under general endotracheal anesthesia. Currently, C1-2 paddle lead placement is an accepted practice, which provides effective cervical stimulation to ameliorate upper-extremity and sometimes lower-extremity symptoms experienced by patients with CRPS. However, this technique must be performed under general endotracheal anesthesia rather than in an awake or semiconscious state due to intraoperative safety concerns and patient comfort. The authors aim to provide additional data to support the following novel technique: the use of somatosensory evoked potential (SSEP) diminution data to assist with proper midline placement of C1-2 leads under general anesthesia. METHODS SSEP median nerve (MN) and posterior tibial nerve (PTN) data were collected from 6 patients undergoing placement of C1-2 leads under general anesthesia. Fluoroscopy was used as an initial guide for proper anatomical midline placement. This was followed by the activation of the spinal cord stimulator and simultaneous collection of primarily MN SSEPs as well as PTN SSEPs for physiological midline placement. Unilateral and bilateral reductions in SSEPs assisted with the correct lateralization of the lead to ensure effective postoperative coverage according to the patient's individual preoperative symptoms. RESULTS Six patients were monitored using SSEPs and repeatable, reliable MN and PTN baseline responses were obtained from all. A reduction in amplitude ranging from 5% to 87% was observed, confirming inhibition of dorsal column conduction, and an average pain relief of 63% at short-term and 64% at long-term follow-up was recorded with 6 of 6 and 5 of 6 patients responding, respectively. CONCLUSIONS Intraoperative SSEP collision study testing appears to be a safe technique to monitor placement of C1-2 paddle leads intraoperatively under general anesthesia.

Spinal cord stimulation: a review of the safety literature and proposal for perioperative evaluation and management

BACKGROUND CONTEXT

There is currently no consensus on appropriate perioperative management of patients with spinal cord stimulator implants. Magnetic resonance imaging (MRI) is considered safe under strict labeling conditions. Electrocautery is generally not recommended in these patients but sometimes used despite known risks.

PURPOSE

The aim was to discuss the perioperative evaluation and management of patients with spinal cord stimulator implants.

STUDY DESIGN

A literature review, summary of device labeling, and editorial were performed, regarding the safety of spinal cord stimulator devices in the perioperative setting.

METHODS

A literature review was performed, and the labeling of each Food and Drug Administration (FDA)-approved spinal cord stimulation system was reviewed. The literature review was performed using PubMed and the FDA website (www.fda.gov).

RESULTS

Magnetic resonance imaging safety recommendations vary between the models. Certain systems allow for MRI of the brain to be performed, and only one system allows for MRI of the body to be performed, both under strict labeling conditions. Before an MRI is performed, it is imperative to ascertain that the system is intact, without any lead breaks or low impedances, as these can result in heating of the spinal cord stimulation (SCS) and injury to the patient. Monopolar electrocautery is generally not recommended for patients with SCS; however, in some circumstances, it is used when deemed required by the surgeon. When cautery is necessary, bipolar electrocautery is recommended. Modern electrocautery units are to be used with caution as there remains a risk of thermal injury to the tissue in contact with the SCS. As with MRI, electrocautery usage in patients with SCS systems with suspected breaks or abnormal impedances is unsafe and may cause injury to the patient.

CONCLUSIONS

Spinal cord stimulation is increasingly used in patients with pain of spinal origin, particularly to manage postlaminectomy syndrome. Knowledge of the safety concerns of SCS and appropriate perioperative evaluation and management of the SCS system can reduce risks and improve surgical planning.

Spinal stimulator peri-electrode masses: case report

The authors describe a case of delayed spastic quadriparesis caused by a peri-electrode mass following the implantation of a minimally invasive percutaneous spinal cord stimulator (SCS). Prior reports with paddle-type electrodes are reviewed, and a detailed histological and pathophysiological comparison with the present case is made. The patient developed tolerance to a cervical percutaneous SCS 4 months after implantation, followed by the onset of spastic quadriparesis 9 months after implantation. The stimulator was removed, and contrast-enhanced MRI revealed an enhancing epidural mass where the system had been placed, with severe spinal cord compression. Decompression was carried out, and the patient experienced neurological improvement. Pathological examination revealed fibrotic tissue with granulomatous and multinucleated giant cell reactions. No evidence of infection or hemorrhage was found. Professionals treating patients with SCSs or contemplating their insertion should be aware of this delayed complication and associated risk factors.

[The use of neuromodulation for the treatment of tremor]

BACKGROUND

Tremor may be a disabling disorder and pharmacologic treatment is the first-line therapy for these patients. Nevertheless, this treatment may lead to a satisfactory tremor reduction in only 50% of patients with essential tremor. Thalamotomy was the treatment of choice for tremor refractory to medical therapy until deep brain stimulation (DBS) of the ventral intermedius nucleus (Vim) of the thalamus has started being used. Nowadays, thalamotomy is rarely performed.

METHODS

This article is a non-systematic review of the indications, results, programming parameters and surgical technique of DBS of the Vim for the treatment of tremor.

RESULTS

In spite of the fact that it is possible to achieve similar clinical results using thalamotomy or DBS of the Vim, the former causes more adverse effects than the latter. Furthermore, DBS can be used bilaterally, whereas thalamotomy has a high risk of causing disartria when it is performed in both sides. DBS of the Vim achieved an adequate tremor improvement in several series of patients with tremor caused by essential tremor, Parkinson's disease or multiple sclerosis. Besides the Vim, there are other targets, which are being used by some authors, such as the zona incerta and the prelemniscal radiations.

CONCLUSION

DBS of the Vim is a useful treatment for disabling tremor refractory to medical therapy. It is essential to carry out an accurate patient selection as well as to use a proper surgical technique. The best stereotactic target for tremor is still unknown, although the Vim is the most used one.

Neural stimulators: a guide to imaging and postoperative appearances

Implantable neural stimulators have been developed to aid patients with debilitating neurological conditions that are not amenable to other therapies. The aim of this article is to improve understanding of correct anatomical placement as well as the relevant imaging methods used to assess these devices. Potential complications following their insertion and an overview of the current indications and potential mechanism of action of these devices is provided.

Mechanism of dorsal column stimulation to treat neuropathic but not nociceptive pain: analysis with a computational model

OBJECTIVE

Stimulation of axons within the dorsal columns of the human spinal cord has become a widely used therapy to treat refractory neuropathic pain. The mechanisms have yet to be fully elucidated and may even be contrary to standard "gate control theory." Our hypothesis is that a computational model provides a plausible description of the mechanism by which dorsal column stimulation (DCS) inhibits wide dynamic range (WDR) cell output in a neuropathic model but not in a nociceptive pain model.

MATERIALS AND METHODS

We created a computational model of the human spinal cord involving approximately 360,000 individual neurons and dendritic processing of some 60 million synapses--the most elaborate dynamic computational model of the human spinal cord to date. Neuropathic and nociceptive "pain" signals were created by activating topographically isolated regions of excitatory interneurons and high-threshold nociceptive fiber inputs, driving analogous regions of WDR neurons. Dorsal column fiber activity was then added at clinically relevant levels (e.g., Aβ firing rate between 0 and 110 Hz by using a 210-μsec pulse width, 50-150 Hz frequency, at 1-3 V amplitude).

RESULTS

Analysis of the nociceptive pain, neuropathic pain, and modulated circuits shows that, in contradiction to gate control theory, 1) nociceptive and neuropathic pain signaling must be distinct, and 2) DCS neuromodulation predominantly affects the neuropathic signal only, inhibiting centrally sensitized pathological neuron groups and ultimately the WDR pain transmission cells.

CONCLUSION

We offer a different set of necessary premises than gate control theory to explain neuropathic pain inhibition and the relative lack of nociceptive pain inhibition by using retrograde DCS. Hypotheses regarding not only the pain relief mechanisms of DCS were made but also regarding the circuitry of pain itself, both nociceptive and neuropathic. These hypotheses and further use of the model may lead to novel stimulation paradigms.

Anatomic connections of the diaphragm: influence of respiration on the body system

The article explains the scientific reasons for the diaphragm muscle being an important crossroads for information involving the entire body. The diaphragm muscle extends from the trigeminal system to the pelvic floor, passing from the thoracic diaphragm to the floor of the mouth. Like many structures in the human body, the diaphragm muscle has more than one function, and has links throughout the body, and provides the network necessary for breathing. To assess and treat this muscle effectively, it is necessary to be aware of its anatomic, fascial, and neurologic complexity in the control of breathing. The patient is never a symptom localized, but a system that adapts to a corporeal dysfunction.