Human Cervical Epidural Spinal Electrogram Topographically Maps Distinct Volitional Movements.

Little is known about the electrophysiologic activity of the intact human spinal cord during volitional movement. We analyzed epidural spinal recordings from a total of five human subjects of both sexes during a variety of upper extremity movements and found that these spinal epidural electrograms contain spectral information distinguishing periods of movement, rest, and sensation. Cervical epidural electrograms also contained spectral changes time-locked with movement. We found that these changes were primarily associated with increased power in the theta (4-8 Hz) band and feature increased theta phase to gamma amplitude coupling, and this increase in theta power can be used to topographically map distinct upper extremity movements onto the cervical spinal cord in accordance with established myotome maps of the upper extremity. Our findings have implications for the development of neurostimulation protocols and devices focused on motor rehabilitation for the upper extremity, and the approach presented here may facilitate spatiotemporal mapping of naturalistic movements.

Modulation of sensory input to the spinal cord: Contribution of focal epidural polarization and of GABA released by interneurons and glial cells.

Modulation of input from primary afferent fibres has long been examined at the level of the first relays of these fibres. However, recent studies reveal that input to the spinal cord may also be modulated at the level of the very entry of afferent fibres to the spinal grey matter before action potentials in intraspinal collaterals of afferent fibres reach their target neurons. Such modulation greatly depends on the actions of GABA via extrasynaptic membrane receptors. In the reported study we hypothesized that the increase in excitability of afferent fibres following epidural polarization close to the site where collaterals of afferent fibres leave the dorsal columns is due to the release of GABA from two sources: not only GABAergic interneurons but also glial cells. We present evidence, primo, that GABA released from both these sources contributes to a long-lasting increase in the excitability and a shortening of the refractory period of epidurally stimulated afferent fibres and, secondo, that effects of epidural polarization on the release of GABA are more critical for these changes than direct effects of DC on the stimulated fibres. The experiments were carried out in deeply anaesthetized rats in which changes in compound action potentials evoked in hindlimb peripheral nerves by dorsal column stimulation were used as a measure of the excitability of afferent fibres. The study throws new light on the modulation of input to spinal networks but also on mechanisms underlying the restoration of spinal functions.

Predictors of Skip Laminotomy for Placement of Paddle Leads for Spinal Cord Stimulation.

OBJECTIVES: Placement of a standard paddle lead for spinal cord stimulation (SCS) requires a laminotomy for positioning of the lead within the epidural space. During initial placement, an additional laminotomy or laminectomy, termed a "skip" laminotomy, may be necessary at a higher level to pass the lead to the appropriate midline position. Patient and radiographic factors that predict the need for a skip laminotomy have yet to be identified. MATERIALS AND METHODS: Participants who underwent SCS paddle placement at Albany Medical Center between 2016 and 2017 were identified. Operative reports were reviewed to identify the paddle type, level of initial laminotomy, target level, and skip laminotomy level. Preoperative thoracic magnetic resonance images (MRIs) were reviewed, and spinal canal diameter, interpedicular distance, and dorsal cerebral spinal fluid thickness were measured for each participant when available. RESULTS: A total of 106 participants underwent thoracic SCS placement. Of these, 97 had thoracic MRIs available for review. Thirty-eight participants required a skip laminotomy for placement of the paddle compared with 68 participants who did not. There was no significant difference in demographic features including age, sex, body mass index, and surgical history. Univariate analyses that suggested trends were selected for further analysis using binary logistic regression. Level of initial laminotomy (odds ratio [OR] = 1.51, p = 0.028), spinal canal diameter (OR = 0.71, p = 0.015), and dorsal cerebrospinal fluid thickness (OR = 0.61, p = 0.011) were correlated with skip laminotomy. Target level (OR = 1.27, p = 0.138) and time from trial (1.01, p = 0.117) suggested potential association. The multivariate regression was statistically significant, X2(10) = 28.02, p = 0.002. The model explained 38.3% of the variance (Nagelkerke R2) and predicted skip laminectomy correctly in 73.3% of cases. However, for the multivariate regression, only a decrease in spinal canal diameter (OR = 0.59, p = 0.041) was associated with a greater odds of skip laminotomy. CONCLUSIONS: This study aims to characterize the patient and radiographic factors that may predict the need to perform a skip laminotomy during the initial placement of SCS paddles. Here, we show that radiographic and anatomic variables, primarily spinal canal diameter, play an important role in predicting the need for a skip laminotomy. Furthermore, we suggest that target level for placement and level of initial laminotomy also may contribute. Further investigation of the predictive factors for performing a skip laminotomy would help optimize surgical planning and preoperative patient selection and counseling.

Activity of Spinal Interneurons during Forward and Backward Locomotion.

Higher vertebrates are capable not only of forward but also backward and sideways locomotion. Also, single steps in different directions are generated for postural corrections. While the networks responsible for the control of forward walking (FW) have been studied in considerable detail, the networks controlling steps in other directions are mostly unknown. Here, to characterize the operation of the spinal locomotor network during FW and backward walking (BW), we recorded the activity of individual spinal interneurons from L4 to L6 during both FW and BW evoked by epidural stimulation (ES) of the spinal cord at L5-L6 in decerebrate cats of either sex. Three groups of neurons were revealed. Group 1 (45%) had a similar phase of modulation during both FW and BW. Group 2 (27%) changed the phase of modulation in the locomotor cycle depending on the direction of locomotion. Group 3 neurons were modulated during FW only (Group 3a, 21%) or during BW only (Group 3b, 7%). We suggest that Group 1 neurons belong to the network generating the vertical component of steps (the limb elevation and lowering) because it should operate similarly during locomotion in any direction, while Groups 2 and 3 neurons belong to the networks controlling the direction of stepping. Results of this study provide new insights into the organization of the spinal locomotor circuits, advance our understanding of ES therapeutic effects, and can potentially be used for the development of novel strategies for recuperation of impaired balance control, which requires the generation of corrective steps in different directions.SIGNIFICANCE STATEMENT Animals and humans can perform locomotion in different directions in relation to the body axis (forward, backward, sideways). While the networks that control forward walking have been studied in considerable detail, the networks controlling steps in other directions are unknown. Here, by recording the activity of the same spinal neurons during forward and backward walking, we revealed three groups of neurons forming, respectively, the network operating similarly during stepping in different directions, the network changing its operation with a change in the direction of stepping, and the network operating only during locomotion in a specific direction. These networks presumably control different aspects of the step. The obtained results provide new insights into the organization of the spinal locomotor networks.

Differences in backward and forward treadmill locomotion in decerebrated cats.

Locomotion in different directions is vital for animal life and requires fine-adjusted neural activity of spinal networks. To compare the levels of recruitability of the locomotor circuitry responsible for forward and backward stepping, several electromyographic and kinematic characteristics of the two locomotor modes were analysed in decerebrated cats. Electrical epidural spinal cord stimulation was used to evoke forward and backward locomotion on a treadmill belt. The functional state of the bilateral spinal networks was tuned by symmetrical and asymmetrical epidural stimulation. A significant deficit in the backward but not forward stepping was observed when laterally shifted epidural stimulation was used but was not observed with central stimulation: only half of the cats were able to perform bilateral stepping, but all the cats performed forward stepping. This difference was in accordance with the features of stepping during central epidural stimulation. Both the recruitability and stability of the EMG signals as well as inter-limb coordination during backward stepping were significantly decreased compared with those during forward stepping. The possible underlying neural mechanisms of the obtained functional differences of backward and forward locomotion (spinal network organisation, commissural communication and supraspinal influence) are discussed.

Revision and Replacement of Spinal Cord Stimulator Paddle Leads.

OBJECTIVES: Paddle leads for spinal cord stimulation (SCS) offer more efficient energy delivery and advantages in some patients. However, there is concern for how safely SCS paddles can be replaced once previously implanted because of scar tissue and the relative vulnerability of the thoracic cord. In this study, we share our experience on SCS paddle replacement. MATERIALS AND METHODS: Participants who underwent SCS replacement at Albany Medical Center between 2011 and 2020 were identified. The medical records were reviewed for demographic data and information regarding initial complications, reason for removal or revision, subsequent complications of replacement surgery and its timing, and whether the implant was ultimately removed. Percutaneous lead replacement cases performed over the same period were used as a comparison group. RESULTS: A total of 1265 patients were identified to have had an SCS-related procedure based on billing codes. Of these, 73 involved replacement of epidural leads (51 paddles, 22 percutaneous). Most paddles (48/51) were replaced at the time of removal. A total of 30 of the 51 paddle replacements required additional lamina removal. Re-operations that occurred more than one year after initial implant were significantly more likely to require additional bone removal (p < 0.001). Paddle re-operations lasted in general 1.7 ± 0.2 hours and had 35 ± 5 mL of blood loss, whereas percutaneous operations lasted 1.3 ± 0.2 hours and had 12.5 ± 2 mL of blood loss. Despite the invasive nature of paddle replacement, there was no difference in complications (p = 0.23) compared with that in percutaneous leads. CONCLUSIONS: This study characterizes the safety profile of SCS paddle replacement surgeries. Here, we demonstrate that the replacement of paddle leads at the time of removal, with additional lamina removal if needed because of scar, is associated with low rates of complications. This validates the feasibility and low-risk profile of replacing paddle leads when clinically indicated for experienced surgeons with specialization in SCS.

The plasticity of nerve fibers: the prolonged effects of polarization of afferent fibers.

The review surveys various aspects of the plasticity of nerve fibers, in particular the prolonged increase in their excitability evoked by polarization, focusing on a long-lasting increase in the excitability of myelinated afferent fibers traversing the dorsal columns of the spinal cord. We review the evidence that increased axonal excitability 1) follows epidurally applied direct current (DC) as well as relatively short (5 or 10 ms) current pulses and synaptically evoked intrinsic field potentials; 2) critically depends on the polarization of branching regions of afferent fibers at the sites where they bifurcate and give off axon collaterals entering the spinal gray matter in conjunction with actions of extrasynaptic GABAA membrane receptors; and 3) shares the feature of being activity-independent with the short-lasting effects of polarization of peripheral nerve fibers. A comparison between the polarization evoked sustained increase in the excitability of dorsal column fibers and spinal motoneurons (plateau potentials) indicates the possibility that they are mediated by partly similar membrane channels (including noninactivating type L Cav++ 1.3 but not Na+ channels) and partly different mechanisms. We finally consider under which conditions transspinally applied DC (tsDCS) might reproduce the effects of epidural polarization on dorsal column fibers and the possible advantages of increased excitability of afferent fibers for the rehabilitation of motor and sensory functions after spinal cord injuries.NEW & NOTEWORTHY This review supplements previous reviews of properties of nerve fibers by surveying recent experimental evidence for their long-term plasticity. It also extends recent descriptions of spinal effects of DC by reviewing effects of polarization of afferent nerve fibers within the dorsal columns, the mechanisms most likely underlying the long-lasting increase in their excitability and possible clinical implications.

Complications of epidural spinal stimulation: lessons from the past and alternatives for the future.

STUDY DESIGN: Systematic review. OBJECTIVES: Over the past decade, an increasing number of studies have demonstrated that epidural spinal cord stimulation (SCS) can successfully assist with neurorehabilitation following spinal cord injury (SCI). This approach is quickly garnering the attention of clinicians. Therefore, the potential benefits of individuals undergoing epidural SCS therapy to regain sensorimotor and autonomic control, must be considered along with the lessons learned from other studies on the risks associated with implantable systems. METHODS: Systematic analysis of literature, as well as preclinical and clinical reports. RESULTS: The use of SCS for neuropathic pain management has revealed that epidural electrodes can lose their therapeutic effects over time and lead to complications, such as electrode migration, infection, foreign body reactions, and even SCI. Several authors have also described the formation of a mass composed of glia, collagen, and fibrosis around epidural electrodes. Clinically, this mass can cause myelopathy and spinal compression, and it is only treatable by surgically removing both the electrode and scar tissue. CONCLUSIONS: In order to reduce the risk of encapsulation, many innovative efforts focus on technological improvements of electrode biocompatibility; however, they require time and resources to develop and confirm safety and efficiency. Alternatively, some studies have demonstrated similar outcomes of non-invasive, transcutaneous SCS following SCI to those seen with epidural SCS, without the complications associated with implanted electrodes. Thus, transcutaneous SCS can be proposed as a promising candidate for a safer and more accessible SCS modality for some individuals with SCI.

Distribution of Spinal Neuronal Networks Controlling Forward and Backward Locomotion.

Higher vertebrates, including humans, are capable not only of forward (FW) locomotion but also of walking in other directions relative to the body axis [backward (BW), sideways, etc.]. Although the neural mechanisms responsible for controlling FW locomotion have been studied in considerable detail, the mechanisms controlling steps in other directions are mostly unknown. The aim of the present study was to investigate the distribution of spinal neuronal networks controlling FW and BW locomotion. First, we applied electrical epidural stimulation (ES) to different segments of the spinal cord from L2 to S2 to reveal zones triggering FW and BW locomotion in decerebrate cats of either sex. Second, to determine the location of spinal neurons activated during FW and BW locomotion, we used c-Fos immunostaining. We found that the neuronal networks responsible for FW locomotion were distributed broadly in the lumbosacral spinal cord and could be activated by ES of any segment from L3 to S2. By contrast, networks generating BW locomotion were activated by ES of a limited zone from the caudal part of L5 to the caudal part of L7. In the intermediate part of the gray matter within this zone, a significantly higher number of c-Fos-positive interneurons was revealed in BW-stepping cats compared with FW-stepping cats. We suggest that this region of the spinal cord contains the network that determines the BW direction of locomotion.SIGNIFICANCE STATEMENT Sequential and single steps in various directions relative to the body axis [forward (FW), backward (BW), sideways, etc.] are used during locomotion and to correct for perturbations, respectively. The mechanisms controlling step direction are unknown. In the present study, for the first time we compared the distributions of spinal neuronal networks controlling FW and BW locomotion. Using a marker to visualize active neurons, we demonstrated that in the intermediate part of the gray matter within L6 and L7 spinal segments, significantly more neurons were activated during BW locomotion than during FW locomotion. We suggest that the network determining the BW direction of stepping is located in this area.

Emergence of Epidural Electrical Stimulation to Facilitate Sensorimotor Network Functionality After Spinal Cord Injury.

BACKGROUND: Traumatic spinal cord injury (SCI) disrupts signaling pathways between the brain and spinal networks below the level of injury. In cases of severe SCI, permanent loss of sensorimotor and autonomic function can occur. The standard of care for severe SCI uses compensation strategies to maximize independence during activities of daily living while living with chronic SCI-related dysfunctions. Over the past several years, the research field of spinal neuromodulation has generated promising results that hold potential to enable recovery of functions via epidural electrical stimulation (EES). METHODS: This review provides a historical account of the translational research efforts that led to the emergence of EES of the spinal cord to enable intentional control of motor functions that were lost after SCI. We also highlight the major limitations associated with EES after SCI and propose future directions of spinal neuromodulation research. RESULTS: Multiple, independent studies have demonstrated return of motor function via EES in individuals with chronic SCI. These enabled motor functions include intentional, controlled movement of previously paralyzed extremities, independent standing and stepping, and increased grip strength. In addition, improvements in cardiovascular health, respiratory function, body composition, and urologic function have been reported. CONCLUSIONS: EES holds promise to enable functions thought to be permanently lost due to SCI. However, EES is currently restricted to scientific investigation in humans with SCI and requires further validation of factors such as safety and efficacy before clinical translation.

Femoral vascular conductance and peroneal muscle sympathetic nerve activity responses to acute epidural spinal cord stimulation in humans.

NEW FINDINGS: What is the central question of this research? Does acute spinal cord stimulation increase vascular conductance and decrease muscle sympathetic nerve activity in the lower limbs of humans? What is the main finding and its importance? Acute spinal cord stimulation led to a rapid rise in femoral vascular conductance, and peroneal muscle sympathetic nerve activity demonstrated a delayed reduction that was not associated with the initial increase in femoral vascular conductance. These findings suggest that neural mechanisms in addition to attenuated muscle sympathetic nerve activity might be involved in the initial increase in femoral vascular conductance during acute spinal cord stimulation. ABSTRACT: Clinical cases have indicated an increase in peripheral blood flow after continuous epidural spinal cord stimulation (SCS) and that reduced muscle sympathetic nerve activity (MSNA) might be a potential mechanism. However, no studies in humans have directly examined the effects of acute SCS (<60 min) on vascular conductance and MSNA. In study 1, we tested the hypothesis that acute SCS (<60 min) of the thoracic spine would lead to increased common femoral vascular conductance, but not brachial vascular conductance, in 11 patients who previously underwent surgical SCS implantation for management of neuropathic pain. Throughout 60 min of SCS, common femoral artery conductance was elevated and significantly different from brachial artery conductance [in millilitres per minute: 15 min, change (Δ) 26 ± 37 versus Δ-2 ± 19%; 30 min, Δ28 ± 45 versus Δ0 ± 26%; 45 min, Δ48 ± 43 versus Δ2 ± 21%; 60 min, Δ36 ± 61 versus Δ1 ± 24%; and 15 min post-SCS, Δ51 ± 64 versus Δ6 ± 33%; P = 0.013]. A similar examination in a patient with cervical SCS revealed minimal changes in vascular conductance. In study 2, we examined whether acute SCS reduces peroneal MSNA in a subset of SCS patients (n = 5). The MSNA burst incidence in response to acute SCS gradually declined and was significantly reduced at 45 and 60 min of SCS (in bursts per 100 heart beats: 15 min, Δ-1 ± 12%; 30 min, Δ-14 ± 12%; 45 min, Δ-19 ± 16%; 60 min, Δ-24 ± 18%; and 15 min post-SCS: Δ-11 ± 7%; P = 0.015). These data demonstrate that acute SCS rapidly increases femoral vascular conductance and reduces peroneal MSNA. The gradual reduction in peroneal MSNA observed during acute SCS suggests that neural mechanisms in addition to attenuated MSNA might be involved in the acute increase in femoral vascular conductance.

Epidural Space Identification With Loss of Resistance Technique for Epidural Analgesia During Labor: A Randomized Controlled Study Using Air or Saline-New Arguments for an Old Controversy.

BACKGROUND: The best technique to identify the epidural space for labor analgesia is still unclear despite the publication of various randomized controlled studies and meta-analyses. Our aim was to assess the superiority of the saline loss of resistance (SLOR) technique over the air loss of resistance (ALOR) technique with respect to the quality of the block. METHODS: Consenting parturients admitted to our obstetric suite for spontaneous or induced labor were randomized to receive epidural analgesia using either the ALOR or SLOR technique. Our primary outcome was to compare the impact of the SLOR and ALOR technique on pain score improvement measured 30 minutes after administration of epidural block. Our secondary outcomes included the density of motor blockade and analgesic efficacy measured at 30 minutes. Primary and secondary outcomes were compared using the Student t test and Mann-Whitney U test. Statistical significance was set at P < .017 for primary and secondary outcomes, considering Bonferroni correction for multiple comparisons. Other comparisons were considered exploratory. RESULTS: Four hundred parturients were included; 24 were excluded from the final analysis. After 30 minutes, pain score reduction (ALOR, 4.7 ± 2.9/10; SLOR, 4.9 ± 3.0/10; P = .49), motor block (ALOR, 1.4 ± 0.8; SLOR, 1.3 ± 0.8; P = .27), and efficacy of the block (ALOR, 1.0 ± 0.7; SLOR, 1.0 ± 0.6; P = .87) did not differ significantly between groups. CONCLUSIONS: Pain score reduction after 30 minutes and onset of the block were not affected by the technique used to locate the epidural space.

Optimizing Stimulation in a Case of Facial Pain Through "Cross-Talk" of Peripheral and Central Leads: A Case Report.

OBJECTIVES: To describe inter-lead (cross-talk) stimulation between a trigeminal nerve lead and a cervical epidural lead for the treatment of facial pain in a 69-year-old patient with empty nose syndrome. MATERIALS AND METHODS: A trial implant was performed with a peripheral V2 trigeminal lead and a C1-C2 lead in cross-talk configuration. During permanent implant, the V2 lead was placed uneventfully while the central lead could only be advanced to C3-C4. RESULTS: During the trial, pain decreased by 70%. One month after permanent implant, the patient still experienced a 60-70% reduction in pain levels and a decrease from ten to two weekly pain episodes. Nine months post implant, the patient reported complete pain relief (0/10 on a numeric rating scale ranging from 0 to 10) and medications were discontinued. Infrequent exacerbations (3/10) were controlled by increasing stimulation. Three years post implant, the patient continued to have no baseline pain and could easily control exacerbations. CONCLUSION: Cross-talk configuration between a peripheral and a central lead created a more efficient stimulation technique. The resulting paresthesia was superior to that obtained from either lead alone and exceeded the paresthesia obtained from the combination of the two leads when used simultaneously, without an inter-lead configuration.

Clinical Practice of Epidural Puncture in Dogs and Cats Assisted by a Commercial Acoustic Puncture Assist Device-Epidural Locator: Preliminary Results.

The objective of this study was to compare an Acoustic Puncture Assist Device-Epidural Locator (APAD-EL) with the "pop sensation" (POP) and "lack of resistance" (LOR) commonly used to confirm penetration of the ligamentum flavum and to ensure correct epidural placement in dogs and cats. We recruited 38 dogs and cats undergoing surgery and receiving epidural analgesia. Two anesthetists performed epidural puncture using the POP and LOR signs. Simultaneously, APAD-EL was used to collect visual and acoustic confirmation during advancement and placement of the needle tip for post hoc evaluation. A positive APAD-EL sign consists of a sudden pressure drop at the needle tip visible on a display and a concomitant pitch change of an acoustic signal. Failure to record a sudden pressure drop is considered a negative APAD sign. Descriptive statistics were used. In 32 patients with positive POP and LOR, the APAD was also positive. In one patient, POP was positive with a negative LOR and APAD result. Five patients had negative POP but positive LOR. Four patients had APAD positive and one (a dog) APAD negative. The study results showed that the APAD-EL information supports the subjective signs of correct needle placement suggested by positive POP and LOR experienced by trained anesthetists. The technique can be useful to assist difficult epidural puncture and as a training and teaching tool.

Epidural spinal cord stimulation for neuropathic pain: a neurosurgical multicentric Italian data collection and analysis.

BACKGROUND: Spinal cord stimulation (SCS) is a technique used worldwide to treat several types of chronic neuropathic pain refractory to any conservative treatment. The aim of this data collection is to enforce evidence of SCS effectiveness on neuropathic chronic pain reported in the literature and to speculate on the usefulness of the trial period in determining the long-term efficacy. Moreover, the very low percentage of undesired side effects and complications reported in our case series suggests that all implants should be performed by similarly well-trained and experienced professionals. METHOD: A multicentric data collection on a common database from 11 Italian neurosurgical departments started 3 years ago. Two different types of electrodes (paddle or percutaneous leads) were used. Of 122 patients, 73 % (N = 89) were submitted to a trial period, while the remaining patients underwent the immediate permanent implant (N = 33). Statistical comparisons of continuous variables between groups were performed. RESULTS: Most of the patients (80 %) had predominant pain to their lower limbs, while only 17 % of patients had prevalent axial pain. Significant reduction in pain, as measured by variation in visual analogue scale (VAS) score, was observed at least 1 year after implantation in 63.8 % of the cases, 59.5 % of patients who underwent a test trial and 71.4 % of patients who underwent permanent implant at once. No statistical differences were found between the lower-limb pain group and the axial pain group. CONCLUSIONS: No relevant differences in long-term outcomes were observed in previously tested patients compared with patients implanted at once. Through this analysis we hope to recruit new centres, to give more scientific value to our results.

[NEW TECHNIQUE OF SPINAL ANESTHESIA WITH EPIDURAL VOLUME EXTENSION FOR CAESAREN SECTION IN PREGNANT WOMEN WITH CONCOMITANT CARDIAC PATHOLOGY].

BACKGROUND: Spinal anesthesia with the epidural volume extension provides the possibility of using small doses of local anesthetics and the low frequency of hypotension. However, the dose of the local anesthetic and the volume of normal saline for administration into the epidural space, remain unclear. OBJECTIVE: To study the influence of new techniques of spinal anesthesia with the epidural volume extension at the level of sensory block and hemodynamic in pregnant with concomitant cardiac pathology during cesarean section. METHODS: In an observational study were included 24 pregnant women with cardiac pathology. Women were divided into 3 groups, depending on the value of intra-abdominal pressure (lAP). Expansion of the epidural space was performed before spinal anesthesia. For spinal anesthesia we used heavy bupivacaine 0.5% (5.5 ± 0.1 mg). The volume of saline for administration into the epidural space depends on the level of lAP RESULTS: The average upper level of sensory block did not difer significantly in groups and amounted Th 2.1 ± 0.5, 95% C.I. 1.6-4.0 (p = 0.001). The only one woman in group 3 (4.1%) developed hypotension. The maximum level of motor block (Bromage score) among the groups was similar and amounted to 1.5 ± 0.2, 95% C.I. 1.0-2.0 (p < 0.001). CONCLUSIONS: The new technique of spinal anesthesia with the epidural extension provides qualitative analgesia and stable hemodynamics in pregnant women with concomitant cardiac pathology

A computational model for epidural electrical stimulation of spinal sensorimotor circuits.

Epidural electrical stimulation (EES) of lumbosacral segments can restore a range of movements after spinal cord injury. However, the mechanisms and neural structures through which EES facilitates movement execution remain unclear. Here, we designed a computational model and performed in vivo experiments to investigate the type of fibers, neurons, and circuits recruited in response to EES. We first developed a realistic finite element computer model of rat lumbosacral segments to identify the currents generated by EES. To evaluate the impact of these currents on sensorimotor circuits, we coupled this model with an anatomically realistic axon-cable model of motoneurons, interneurons, and myelinated afferent fibers for antagonistic ankle muscles. Comparisons between computer simulations and experiments revealed the ability of the model to predict EES-evoked motor responses over multiple intensities and locations. Analysis of the recruited neural structures revealed the lack of direct influence of EES on motoneurons and interneurons. Simulations and pharmacological experiments demonstrated that EES engages spinal circuits trans-synaptically through the recruitment of myelinated afferent fibers. The model also predicted the capacity of spatially distinct EES to modulate side-specific limb movements and, to a lesser extent, extension versus flexion. These predictions were confirmed during standing and walking enabled by EES in spinal rats. These combined results provide a mechanistic framework for the design of spinal neuroprosthetic systems to improve standing and walking after neurological disorders.

Anterograde and retrograde epidural paddle placement through a single laminotomy for the treatment of back and lower extremity pain using spinal cord stimulation: case reports and technical note.

OBJECTIVE: Spinal cord stimulation can be effectively used in the treatment of low back pain and extremity pain in failed back surgery syndrome. Ideal targets for stimulation corresponding to paresthesia overlap in the low back versus the extremities may differ in cranial-caudal location. MATERIALS AND METHODS: We present here a technical report of three cases demonstrating a technique to place anterograde and retrograde epidural paddles through a single laminotomy. RESULTS: Using this technique we were able to cover five spinal levels in each patient, and different stimulation programs at different levels created paresthesia overlap in back versus lower extremity in those patients. CONCLUSION: Dual paddle placement through a single laminotomy may be a reasonable option for select patients where coverage of anatomically-separated pain regions is necessary. This technique can be performed in most patients without significantly increased morbidity.

New technique for open placement of paddle-type spinal cord stimulator electrode in presence of epidural scar tissue.

OBJECTIVES: The objective of this study is to present a novel surgical technique for safe placement of paddle-type spinal cord stimulation (SCS) electrode in the presence of epidural scar tissue. MATERIALS AND METHODS: We developed a new surgical technique for placement of paddle-type SCS electrode in presence of epidural scar tissue when conventional placement methods had failed. The technique involves creating a laminotomy trough to provide an adequate window for dissection of scar tissue to ensure safe placement of the electrode. We have applied this technique in eight patients. RESULTS: Safe placement of SCS electrode was achieved in all eight patients without any complications. All electrodes were placed between T8 and T10 levels, and we were able to place the electrodes in the midline and achieve adequate coverage in all cases. CONCLUSION: SCS is a widely accepted treatment modality for chronic neuropathic pain. Placement of paddle electrode can be challenging, usually because of the presence of epidural scar tissue. There have been reported cases of spinal cord injury related to paddle electrode placement. We present a novel technique that allows for safe placement of a paddle-type SCS electrode in more challenging surgical circumstances, including the presence of epidural scar tissue.

Use of a newly developed delivery device for percutaneous introduction of multiple lead configurations for spinal cord stimulation.

OBJECTIVE: The Epiducer lead delivery system is a novel lead delivery device that can be used to percutaneously implant S-Series paddle leads (St. Jude Medical, Plano, TX, USA) as well as multiple percutaneous leads obviating the need for laminectomy and/or multiple needle sticks, respectively. This study evaluates the safety and usage of the Epiducer lead delivery system. METHODS: An Institutional Review Board-approved observational data collection study was conducted to evaluate usage patterns of the Epiducer system. In addition to the number and frequency of different lead configurations, the following procedural aspects of the surgery were recorded during the evaluation: angle of entry, distance from entry to final lead placement, and physician feedback. Descriptive statistics on adverse events, procedural aspects, and patient outcomes were compiled. RESULTS: Data were collected from 163 patients across 25 investigational sites. Physicians successfully implanted patients using the Epiducer during 89% of the procedures. Seven possible lead configurations were implanted. There were 96% and 92% of physicians "satisfied" or "very satisfied" with accessing the epidural space and placing multiple leads with the Epiducer delivery system, respectfully. Eighty-nine percent of physicians were "satisfied" or "very satisfied" with implanting an S-Series paddle lead using the Epiducer delivery system. Ninety-five percent of physicians were "satisfied" or "very satisfied" with the Epiducer delivery system overall. Ten patients (6%) experienced adverse events. CONCLUSION: Results suggest that the Epiducer delivery system allows for the safe and successful percutaneous implantation of paddle leads and/or multiple lead configurations. Furthermore, physicians are satisfied with the Epiducer delivery system.