Prospective Six-Month Analysis of Multiarea Burst Spinal Cord Stimulation: Correlating Intraoperative Neuromonitoring With Postoperative Programming and Clinical Outcomes.

INTRODUCTION: DeRidder burst spinal cord stimulation (SCS) has shown superior relief from overall pain to traditional tonic neurostimulation therapies and a reduction in back and leg pain. However, nearly 80% of patients have two or more noncontiguous pain areas. This affects the ability to effectively program stimulation and deliver long-term efficacy of the therapy. Multiple DeRidder burst region programming is an option to treat multisite pain by interleaving stimulation at multiple areas along the spinal cord. Previous intraoperative neuromonitoring studies have shown that DeRidder burst stimulation provides broader myotomal coverage at a lower recruitment threshold. The goal of this study is to correlate intraoperative electromyogram (EMG) threshold and postsynaptic excitability with postoperative paresthesia thresholds and optimal burst stimulation programming. MATERIALS AND METHODS: Neuromonitoring was performed during permanent implant of SCS leads in ten patients diagnosed with chronic intractable back and/or leg pain. Each patient underwent the surgical placement of a Penta Paddle electrode through laminectomy at the T8-T11 spinal levels. Subdermal electrode needles were placed into lower extremity muscle groups, in addition to the rectus abdominis muscles, for EMG recording. Evoked responses were compared across multiple trials of burst stimulation in which the number of independent burst areas was varied. After intraoperative data collection, all patients were programmed with single- and multiarea DeRidder burst. Intermittent dosing was delivered at 30:90, 120:360, 120:720, and 120:1440 (seconds ON/OFF) intervals. Numerical rating scale (NRS) and Patient Global Impression of Change scores were evaluated at one, two, three, four, and six months after permanent implant. RESULTS: The thresholds for EMG recruitment after DeRidder burst differed across all patients owing to anatomical and physiological variations. After a 30-second dose of stimulation, the average decrease in thresholds was 1.25 mA for two-area and 0.9 mA for four-area DeRidder burst. Furthermore, a 30-second dose of multisite DeRidder burst produced a 0.25 mA reduction in the postoperative paresthesia thresholds. Across all patients, the baseline NRS score was 6.5 ± 0.5, and the NRS score after single or multiarea DeRidder burst therapy was 2.87 ± 1.50. Eight of ten patients reported a ≥50% decrease in their pain scores through the six-month follow-up visit. Pain outcomes using intermittent multiarea stimulation with longer OFF times (120:360, 120:720, 120:1440) were comparable to those using single-area DeRidder burst at 30:90 up to six months after implant with patient preference being two-area DeRidder burst. CONCLUSIONS: This study aims to evaluate the use of intraoperative neuromonitoring to optimize stimulation programming for multisite pain and correlate it with postoperative programming and efficacy. These results suggest that multisite programming can be used to further customize DeRidder burst stimulation to each individual patient and improve outcomes and quality of life for patients receiving SCS therapy for multisite pain.

Incidence and Risk Factors for Spinal Cord Stimulator Lead Migration With or Without Loss of Efficacy: A Retrospective Review of 91 Consecutive Thoracic Lead Implants.

OBJECTIVE: Lead migration after spinal cord stimulator (SCS) implant is a commonly reported complication and the most common reason for revision surgery in cases of loss of efficacy. The primary aims of this study are to describe the incidence and degree of lead migration in the subacute postoperative period after SCS implant and to report potential risk factors for lead migration. MATERIALS AND METHODS: We performed a retrospective chart review of all patients at a single academic center who received an SCS implant from January 1, 2020, to December 31, 2020. Information on patient (age, sex, weight, and height) and operative factors (device manufacturer, epidural access level and method, and implantable pulse generator location) were extracted from medical records. Intraoperative imaging was compared to subacute follow-up imaging obtained less than 20 days postimplant to measure lead migration distance. Regression models were fitted to determine associations between lead migration distance and potential clinical risk factors. RESULTS: A total of 91 cases (182 leads) were included in the study. Within 20 days of implantation, 88.5% of leads had migrated (86.3% caudal and 2.2% cephalad). Mean migration distance for leads with caudal migration only was 12.34 ± 12.19 mm based on anteroposterior radiographs and 16.95 ± 15.68 mm on lateral radiographs. There was an association of greater caudal lead migration as patient body mass index increased (ß-coefficient 0.07 [95% confidence interval 0.01-0.13], p = 0.031). Within the entire cohort, one patient (1.1%) required lead revision for loss of efficacy. CONCLUSIONS: In the subacute postoperative period after SCS implant, the majority of SCS leads migrated caudally with an average of two lead contacts. Knowledge of this expected migration and risk factors can better inform implanting physicians intraoperatively when deciding final lead placement location. The finding of high likelihood of caudal lead migration in the subacute postoperative period brings the need for a well-designed prospective study to the forefront of our field. This will allow implanting providers to make well-informed decisions for intraoperative lead placement.

Effects of Lower Thoracic Spinal Cord Stimulation on Bowel Management in Individuals With Spinal Cord Injury.

OBJECTIVE: To systematically determine whether use of the spinal cord stimulation (SCS) system to restore cough may improve bowel management (BM) in individuals with spinal cord injury (SCI). DESIGN: Experimental studies (clinical trial). SETTING: Inpatient hospital setting for electrode insertion; outpatient setting for measurement of respiratory pressures; home setting for application of SCS. PARTICIPANTS: Participants (N=5) with cervical SCI. INTERVENTION: A fully implantable SCS cough system was surgically placed in each subject. SCS was applied at home, 2-3 times/d, on a chronic basis, every time bowel regimen was performed and as needed for secretion management. Stimulus parameters were set at values resulting in near maximum airway pressure generation, which was used as an index of expiratory muscle strength. Participants also used SCS during their bowel routine. MAIN OUTCOME MEASURES: Airway pressure generation achieved with SCS. Weekly completion of Bowel Routine Log including BM time, mechanical measures, and medications used. RESULTS: Mean pressure during spontaneous efforts was 30±8 cmH2O. After a period of reconditioning, SCS resulted in pressure of 146±21 cmH2O. The time required for BM routines was reduced from 118±34 minutes to 18±2 minutes (P<.05) and was directly related to the magnitude of pressure development during SCS. Mechanical methods for BM were completely eliminated in 4 patients. No patients experienced fecal incontinence as result of SCS. Each participant also reported marked overall improvement associated with BM. CONCLUSIONS: Our results of this pilot study suggest that SCS to restore cough may be a useful method to improve BM and life quality for both patients with SCI and their caregivers. Our results indicate that the improvement in BM is secondary to restoration of intra-abdominal pressure development.

Electroceutical Targeting of the Autonomic Nervous System.

Autonomic nerves are attractive targets for medical therapies using electroceutical devices because of the potential for selective control and few side effects. These devices use novel materials, electrode configurations, stimulation patterns, and closed-loop control to treat heart failure, hypertension, gastrointestinal and bladder diseases, obesity/diabetes, and inflammatory disorders. Critical to progress is a mechanistic understanding of multi-level controls of target organs, disease adaptation, and impact of neuromodulation to restore organ function.

Bipolar transcutaneous spinal stimulation evokes short-latency reflex responses in human lower limbs alike standard unipolar electrode configuration.

Noninvasive electrical stimulation targeting the posterior lumbosacral roots has been applied recently in reflexes studies and as a neuromodulation intervention for modifying spinal cord circuitry after an injury. Here, we characterized short-latency responses evoked by four bipolar electrode configurations placed longitudinally over the spinal column at different vertebral levels from L1 to T9. They were compared with the responses evoked by the standard unipolar (aka monopolar) electrode configuration (cathode at T11/12, anode over the abdominal wall). Short-latency responses were recorded in the rectus femoris, medial hamstrings, tibialis anterior, and soleus muscles, bilaterally, in 11 neurologically intact participants. The response recruitment characteristics (maximal amplitude, motor threshold) and amplitude-matched onset latencies and paired-pulse suppression (35-ms interstimulus interval) were assessed with 1-ms current-controlled pulses at intensities up to 100 mA. The results showed that short-latency responses can be elicited with all bipolar electrode configurations. However, only with the cathode at T11/12 and the anode 10 cm cranially (∼T9), the maximum response amplitudes were statistical equivalent (P < 0.05) in the medial hamstrings, tibialis anterior, and soleus but not the rectus femoris, whereas motor thresholds were not significantly different across all muscles. The onset latency and paired-pulse suppression were also not significantly different across the tested electrode configurations, thereby confirming the reflex nature of the bipolar short-latency responses. We conclude that the bipolar configuration (cathode T11/12, anode ∼T9) produces reflex responses that are ostensibly similar to those evoked by the standard unipolar configuration. This provides an alternative approach for neuromodulation intervention.NEW & NOTEWORTHY Transcutaneous spinal stimulation with the identified bipolar electrode configuration may offer several advantages for neuromodulation interventions over commonly used unipolar configurations: there are no associated abdominal contractions, which improves the participant's comfort; additional dermatomes are not stimulated as when the anode is over the abdominal wall or iliac crest, which may have unwanted effects; and, due to a more localized electrical field, the bipolar configuration offers the possibility of targeting cord segments more selectively.

Evaluation of MRI Issues for a New Wirelessly Powered, Spinal Cord Stimulation Lead With Receiver.

OBJECTIVE. MRI is an imaging modality frequently ordered for patients with neuromodulation systems implanted for spinal cord stimulation. The purpose of this investigation was to evaluate MRI safety issues (magnetic field interactions, MRI-related heating, functional disturbances, and artifacts) for a new wirelessly powered lead with receiver used for SCS. MATERIALS AND METHODS. Lead samples underwent in vitro evaluation for MRI safety issues using standardized techniques. Magnetic field interactions (i.e., translational attraction and torque) and artifacts were tested at 3 T. MRI-related heating was performed at 1.5 T/64 MHz and 3 T/128 MHz using two different methods: numerical simulations with analytical modeling and physical testing. Possible functional disturbances were evaluated under exposures to 1.5-T/64-MHz and 3-T/128-MHz MRI conditions. RESULTS. The lead exhibited minor magnetic field interactions (22° deflection angle, no torque) at 3 T. The highest temperature change recorded at 1.5 T/64 MHz and 3 T/128 MHz was 3.8°C and 11.3°C, respectively. Exposures to MRI conditions did not damage or alter the functional aspects of the leads. The maximum artifact size seen on a gradient-echo pulse sequence extended approximately 10 mm relative to the size of the lead. CONCLUSION. The MRI tests performed on patients with the new lead with receiver revealed no substantial concerns with respect to the conditions that we provide in the safety guidelines that were based on the results of this investigation. Therefore, MRI examinations will result in acceptable heating when conducted at appropriate whole-body-averaged specific absorption rate levels (i.e., 2.0 W/kg at 1.5 T/64 MHz and 0.3 W/kg at 3 T/128 MHz, corresponding to adjusted temperature rises of 3.6°C and 1.2°C, respectively). Therefore, patients with this wirelessly powered lead and receiver implanted can safely undergo MRI examinations under specific conditions.

Spinal Cord Stimulation with Surgical Lead Improves Pain and Gait in Parkinson's Disease after a Dislocation of Percutaneous Lead: A Case Report.

Spinal cord stimulation (SCS) is receiving increasing interests for treating pain and gait disorders in patients with Parkinson's disease (PD). In an SCS study, it is hard to apply a double-blind approach, especially at low frequencies, as the stimulation normally induces paresthesia which can be perceived by the patient. We herein demonstrate a case treated with SCS in which a blinding design was accomplished by an accidental dislocation of a stimulation lead. A 73-year-old man with PD was admitted to our hospital because of relapsed low back pain. This was due to the dislocation of a previously implanted SCS lead, which caused a decrease in its effectiveness in alleviating pain (from 81 to 43% measured by King's Parkinson's Disease Pain Scale) and improving gait (from 35 to 28% measured by the timed up and go test). A second SCS surgery using a paddle lead solved this problem, with improvements in pain and gait rebounded to 81 and 45%. In this case, the paresthesia induced by SCS (using either a paddle lead or percutaneous leads) was below the threshold of perception when the patient was sitting and standing, and a dislocation of one previously implanted percutaneous lead did not cause evident changes in his sensation of paresthesia. At last follow-up, the patient's quality of life had improved by 40% as measured by the 8-item Parkinson's Disease questionnaire (PDQ-8). This study could serve partly as a proof that low-frequency SCS is effective in improving pain as well as gait problems in PD patients, which was unlikely a result of a placebo effect.

Focused Ultrasound Thalamotomy with Dentato-Rubro-Thalamic Tractography in Patients with Spinal Cord Stimulators and Cardiac Pacemakers.

Magnetic resonance image-guided high-intensity focused ultrasound (MRgFUS)-based thermal ablation of the ventral intermediate nucleus of the thalamus (VIM) is a minimally invasive treatment modality for essential tremor (ET). Dentato-rubro-thalamic tractography (DRTT) is becoming increasingly popular for direct targeting of the presumed VIM ablation focus. It is currently unclear if patients with implanted pulse generators (IPGs) can safely undergo MRgFUS ablation and reliably acquire DRTT suitable for direct targeting. We present an 80-year-old male with a spinal cord stimulator (SCS) and an 88-year-old male with a cardiac pacemaker who both underwent MRgFUS for medically refractory ET. Clinical outcomes were measured using the Clinical Rating Scale for Tremor (CRST). DRTT was successfully created and imaging parameter adjustments did not result in any delay in procedural time in either case. In the first case, 7 therapeutic sonications were delivered. The patient improved immediately and durably with a 90% CRST-disability improvement at 6-week follow-up. In our second case, 6 therapeutic sonications were delivered with durable, 75% CRST-disability improvement at 6 weeks. These are the first cases of MRgFUS thalamotomy in patients with IPGs. DRTT targeting and MRgFUS-based thermal ablation can be safely performed in these patients using a 1.5-T MRI.

Anatomic Lead Placement Without Paresthesia Mapping Provides Effective and Predictable Therapy During the Trial Evaluation Period: Results From the Prospective, Multicenter, Randomized, DELIVERY Study.

OBJECTIVE: The purpose of this study was to compare the trial success rate between anatomic lead placement (AP) and paresthesia-mapped (PM) lead placement techniques for spinal cord stimulation (SCS) using a nonlinear burst stimulation pattern. MATERIALS AND METHODS: Eligible patients with back and/or leg pain with a Numeric Rating Scale (NRS) score of ≥6 who had not undergone previous SCS were enrolled in the study. A total of 270 patients were randomized in a 1:1 ratio to each treatment arm. In the AP group, one lead tip was placed at the mid-body of T8, and the other at the superior endplate of T9. In the PM group, physicians confirmed coverage of the patient's primary pain location. Trial success was a composite of the following: ≥50% patient-reported pain relief at the end of the minimum three-day trial period, physician's recommendation, and patient's interest in a permanent implant. RESULTS: Trial success for AP vs. PM groups was equivalent to 84.4% and 82.3%, respectively. Physicians who performed both techniques preferred AP technique (70% vs. 30%). Procedure times for placement of two leads were 31% shorter in the AP group (p < 0.0001). Decrease in the mean NRS pain score was similar between groups (53.2%, AP group; 53.8%, PM group, p = 0.79). Trial success for patients who went on to an extended trial with tonic stimulation was 50% (5/10) vs. 79% (11/14) for AP group and PM group, respectively (p = 0.2). A total of 13 adverse events were observed (4.5%), most commonly lead migrations and pain around implant site, with no difference between groups. CONCLUSIONS: When using a nonlinear burst stimulation pattern, anatomic or PM lead placement technique may be used. Nonresponders to subthreshold stimulation had a higher conversion rate when a PM technique was used. AP resulted in shorter procedure times with a similar safety profile and was strongly preferred by trialing physicians.

Analysis of S1 DRG Programming to Determine Location of the DRG and Ideal Anatomic Positioning of the Electrode.

INTRODUCTION: Dorsal root ganglion (DRG) stimulation has been established as a therapy in the treatment of chronic pain. Ideal electrode placement is guided by proper identification of the location of the DRG. The location of the S1 DRG is not well delineated and can be variable making ideal location of the electrode placement difficult based on fluoroscopic imaging. METHODS: This is a retrospective analysis of postoperative programming of S1 DRG leading across two centers. There were 34 lead placements in 24 patients included in this study. Programming parameters and contacts used were evaluated based on the position of the electrode in reference to the sacral border. RESULTS: The majority of the patient programming parameters were recorded at six weeks following the implant. Most commonly, the programming used a simple continuous bipole configuration. Of the 34 leads programmed, 17 (50%) had programming on the sacral border, 14 (41%) were considered posterior, and 3 (9%) were anterior to the sacral border. CONCLUSION: This analysis of S1 DRG programming demonstrates that ideal positioning of the majority of the contacts for the electrode should be posterior and along the sacral border on fluoroscopic imaging. These findings also suggest that the S1 DRG may be located most reproducibly at the border of the intraforaminal and intracanalicular region.

The Importance of the Location of Dorsal Root Ganglion Stimulator Electrodes Within the Nerve Root Exit Foramen.

OBJECTIVE: To quantify the relationship between the electrical power requirement to achieve pain relief and the position of the active electrode of dorsal root ganglion stimulators within the spinal nerve root exit foramen. MATERIALS AND METHODS: Retrospective analysis of prospectively collected data of 92 consecutive patients undergoing dorsal root ganglion stimulation (DRGS) for chronic pain in a single center. Cervical and sacral cases, and failed trials/explanted DRGS were excluded, so we report on 57 patients with 78 implanted leads. Anteroposterior and lateral fluoroscopic images of the lead in the exit foramen were examined, and the active electrode positions were put into categories depending on their location relative to fixed anatomical landmarks. The clinical outcome and the power requirements for each of these groups of electrodes were then analyzed. Overall pain outcome was assessed by numeric pain rating scale score pre-operatively and post-operatively. RESULTS: There was no significant relationship between power requirements and mediolateral electrode position, although the lowest average was observed with electrode positions directly below the center of the pedicle. On lateral x-ray, the lowest power requirements were observed in the electrodes positioned superodorsally or dorsally within the foramen. Importantly, power requirements in this location were consistently low, while the power requirements in other locations were not only higher but also much more variable. Electrodes in the superodorsal position required a median output power almost four times lower than electrodes in other positions (p = 0.002). Clinical outcome was not significantly related to power requirement or foraminal position. CONCLUSION: Aiming for a superodorsal electrode position on lateral intraoperative fluoroscopy is desirable, since siting leads in this location reduces the required stimulator output power very substantially and thus will extend battery life. Position within the foramen does not determine clinical outcome, and so the implanter can safely aim for the low power site without detriment to the analgesic efficacy of the system.

Redefining Spinal Cord Stimulation "Trials": A Randomized Controlled Trial Using Single-Stage Wireless Permanent Implantable Devices.

BACKGROUND: "Traditional" spinal cord stimulation (SCS) trials with percutaneous electrodes externalized to a pulse generator (PG) are typically limited in duration due to risk of infection. Newer miniaturized wireless SCS technology eliminates the percutaneous extension (as well as PGs implanted for chronic use), thus facilitating a single-stage implantation after which the device can remain indefinitely. OBJECTIVE: To evaluate fully implanted wireless SCS devices during a 30-day screening trial in subjects with chronic low back pain and leg pain and a history of lumbosacral spine surgery. METHODS: In a randomized controlled trial of single-stage wireless SCS using a wireless percutaneous system, 99 subjects received either 10 kHz high frequency stimulation (HFS) or lower frequency stimulation (LFS) below 1500 Hz (Bolash R, Creamer M, Rauck R, et al. Wireless high frequency spinal cord stimulation (10 kHz) compared to multi-waveform low frequency spinal cord stimulation in the management of chronic pain in failed back surgery syndrome subjects: preliminary results of a multicenter, prospective, randomized controlled study. Pain Med 2019, https://doi.org/10.1093/pm/pnz019). In this report, we assess the 30-day trial success rate (≥50% pain relief from baseline) and complications. RESULTS: The overall trial success rate was 88% (87/99): 92% (46/50) for HFS and 84% (41/49) for LFS (NS). The trial success rate in the 64 subjects with predominant low back pain was 92% (59/64) vs. 80% (28/35) in those with leg pain ≥ low back pain (NS). During the screening trial, one infection occurred (1%) and one subject withdrew and was explanted (1%). Electrode migrations were seen on routine follow-up x-rays in 10 cases (10%). CONCLUSION: Using wireless SCS devices that allow for an extended trial period and evaluation of various waveforms, we observed a high rate trial success rate with both HFS and LFS waveforms, with minimal incidence of infection. Long-term follow-up will address the cost-effectiveness and morbidity associated with this technology, which facilitates single-stage treatment.

Percutaneously Inserted Unilateral Lead Migration Salvaged with a Paddle Electrode.

INTRODUCTION: Lead migration has been regarded as a frequent complication after percutaneous spinal cord stimulation (SCS). Thus far, repeated reinsertion of leads or replacement of paddle electrodes after removing percutaneous leads has been performed, but a salvage surgical technique using the remaining electrode has not been reported. Here, we describe a case in which unilateral lead migration was successfully treated with the insertion of a paddle electrode. CASE SUMMARY: A 44-year-old male paraplegic patient with chronic neuropathic pain in the right leg and low back for 7 years underwent a percutaneous spinal cord stimulation procedure 5 times over 2 years because of repeated unilateral lead migration. The left lead underwent repeated migration and was difficult to reinsert due to epidural adhesion. After confirming the position and stimulation area of the remaining lead, we decided to insert another paddle electrode beside the remaining lead. We performed a T10 laminotomy and inserted a paddle electrode on the right side, using it in combination with the previous left lead. After surgery, the patient was satisfied with a wide coverage area. DISCUSSION: We recommend salvage additional paddle electrode insertion rather than removing both leads during revision SCS. This surgical method increases the possibility of covering the dorsal column (DC) of the spinal cord, is cost effective, and decreases the possibility of failing to cover dorsal column using the paddle electrode during open surgery because the remaining lead's position and stimulation area guide the insertion of the additional paddle lead.

Longevity and Utilization Cost of Rechargeable and Non-Rechargeable Spinal Cord Stimulation Implants: A Comparative Study.

INTRODUCTION: Despite major advancements in features and capabilities of the implantable pulse generator (IPG), real-life longevity and cost-effectiveness studies to guide pain specialists to make the appropriate choice between rechargeable and non-rechargeable IPG are limited. Our study aimed to compare the longevity and cost effectiveness of rechargeable vs. non-rechargeable IPG and SCS systems. METHODS: Data were collected for all SCS implantations performed between 1994 and 2018. The primary goal was to determine IPG longevity, defined as the time interval between IPG implantation and elective replacement due to IPG end of life (EOL). On the other hand, SCS system longevity was defined as the time between SCS implantation and its removal or revision for any reason other than IPG EOL. Kaplan-Meier and log-rank tests were used to assess IPG and SCS system longevities. Cost analysis was performed for cost effectiveness. RESULTS: The median IPG longevity was significantly higher for rechargeable SCS devices than for non-rechargeable SCS devices (7.20 years and 3.68 years, respectively). The median cost per day was similar for both IPGs, $13.90 and $13.81 for non-rechargeable and rechargeable, respectively. The median cost for SCS systems was higher for the rechargeable group ($60.70) compared with the non-rechargeable group ($31.38). CONCLUSIONS: Rechargeable IPG had increased longevity compared to their non-rechargeable counterparts, yet there was no significant difference in the actual longevity due to premature revisions or explantations between both SCS systems. Furthermore, non-rechargeable SCS systems were found to be the more cost-effective option when compared with rechargeable SCS systems.

Cervical Spinal Cord Stimulator Lead Migration and Transection Adjacent to the Foramen Magnum: A Case Report.

BACKGROUND: Spinal cord stimulation (SCS) is a relatively safe therapy for the treatment of pain but has the potential for several complications, including lead migration and breakage. While instances of lead breakage and electrode shearing have been described, there are no reported cases of stimulator lead transection and migration to the foramen magnum. AIMS: We describe the case of a 53-year-old woman who reported that her cervical spinal cord stimulator was no longer functioning after a traumatic fall. CASE: Fluoroscopy of the neck revealed that one of the MRI conditional leads had migrated cephalad, and the distal aspect appeared to be transected. This was confirmed by computerized tomography, which showed a transected portion of the lead in the epidural space, just inferior to the posterior aspect of the foramen magnum. An SCS device revision was performed to replace the lead, but the distal transected tip was left in place in the epidural space adjacent to the foramen magnum to avoid complications of retrieval. DISCUSSION/CONCLUSION: Given the location of the transected portion of the lead, we recommended avoiding MRI imaging. In addition, we advised the patient that a repeat x-ray may be necessary if she has increased neck pain or any other concerning symptoms. In this report, we discuss the known complications with SCS, as well as management of a retained lead fragment.

Peri-procedural Management of Implanted Spinal Cord Stimulators in Patients Undergoing Radiofrequency Ablation: A Case Report and Manufacturer-Specific Recommendations.

INTRODUCTION: Radiofrequency ablation (RFA) and spinal cord stimulation (SCS) are 2 common modalities used in management of various pain conditions. RFA generates heat and an electromagnetic field that can theoretically interfere with the functionality and longevity of the SCS device. This is problematic for patients who need RFA and have previously undergone implantation of an SCS device. CASE DESCRIPTION: We present a case highlighting the safe use of bipolar RFA in a patient who had previously undergone implantation of a cervical SCS device. DISCUSSION: We also present device-specific industry guidelines and recommendations for performing RFA in patients following SCS device implantation.

Managing acute cancer pain.

Cancer-related pain is an ongoing concern for patients and families. Clinicians should include pain management or palliative care specialists who have advanced knowledge in pharmacotherapy and who have the ability to perform interventional procedures to help alleviate patients' pain and reduce opioid use. This article discusses available interventions for patients with cancer pain.

Assessment of axonal recruitment using model-guided preclinical spinal cord stimulation in the ex vivo adult mouse spinal cord.

Spinal cord stimulation (SCS) is used clinically to limit chronic pain, but fundamental questions remain on the identity of axonal populations recruited. We developed an ex vivo adult mouse spinal cord preparation to assess recruitment following delivery of clinically analogous stimuli determined by downscaling a finite element model of clinical SCS. Analogous electric field distributions were generated with 300-µm × 300-µm electrodes positioned 200 µm above the dorsal column (DC) with stimulation between 50 and 200 µA. We compared axonal recruitment using electrodes of comparable size and stimulus amplitudes when contacting the caudal thoracic DC and at 200 or 600 µm above. Antidromic responses recorded distally from the DC, the adjacent Lissauer tract (LT), and in dorsal roots (DRs) were found to be amplitude and site dependent. Responses in the DC included a unique component not seen in DRs, having the lowest SCS recruitment amplitude and fastest conduction velocity. At 200 µm above, mean cathodic SCS recruitment threshold for axons in DRs and LT were 2.6 and 4.4 times higher, respectively, than DC threshold. SCS recruited primary afferents in all (up to 8) caudal segments sampled. Whereas A and C fibers could be recruited at nearby segments, only A fiber recruitment and synaptically mediated dorsal root reflexes were observed in more distant (lumbar) segments. In sum, clinically analogous SCS led to multisegmental recruitment of several somatosensory-encoding axonal populations. Most striking is the possibility that the lowest threshold recruitment of a nonprimary afferent population in the DC are postsynaptic dorsal column tract cells (PSDCs) projecting to gracile nuclei.NEW & NOTEWORTHY Spinal cord stimulation (SCS) is used clinically to control pain. To identify axonal populations recruited, finite element modeling identified scaling parameters to deliver clinically analogous SCS in an ex vivo adult mouse spinal cord preparation. Results showed that SCS first recruited an axonal population in the dorsal column at a threshold severalfold lower than primary afferents. These putative postsynaptic dorsal column tract cells may represent a previously unconsidered population responsible for SCS-induced paresthesias necessary for analgesia.

Safety and Utility of Spinal Magnetic Resonance Imaging in Patients with High-Frequency Spinal Cord Stimulators: A Prospective Single-Centre Study.

BACKGROUND: Implanted high-frequency spinal cord stimulators at 10 kHz (HF-SCS) have recently acquired conditional approval for magnetic resonance imaging (MRI), including retrospective application to previously implanted devices. Under certain conditions, there are greater specific absorption rate (SAR) scanning restrictions compared to some conventional alternatives. This poses technical challenges to obtain diagnostic quality imaging. OBJECTIVES: To describe our experience with 9 such scans, demonstrating that safe and diagnostically useful images can be obtained despite these restrictions. METHODS: We report a prospective single-centre series of 9 scans within a tertiary neuroscience centre, all obtained within the required SAR limit of ≤0.4 W/kg, and describe the scanning protocol we have developed. We further illustrate this with 2 representative patient cases. RESULTS: The imaging studies were well tolerated without complication. In all cases, the imaging quality was sufficient for the reporting neuroradiologist to answer the clinical question posed. CONCLUSION: Despite technical challenges, MRI is feasible, safe and diagnostically useful in HF-SCS-implanted patients. We would invite other centres that implant these devices to consider the development of their own scanning protocols to avoid the morbidity and inconvenience of explantation or computed tomography myelography. To our knowledge, this is the first reported study of MRI in HF-SCS-implanted patients achieving the requisite SAR limit of ≤0.4 W/kg.

Pilot study of feasibility and effect of anodal transcutaneous spinal direct current stimulation on chronic neuropathic pain after spinal cord injury.

STUDY DESIGN: A single-blind crossover study. OBJECTIVES: This study aimed to evaluate neuropathic pain in persons with spinal cord injury (SCI) after the application of transcutaneous spinal direct current stimulation (tsDCS). SETTING: Outpatient Clinic of the Rehabilitation Department, Seoul National University Hospital. METHODS: The effect of single sessions of both anodal and sham tsDCS (2 mA, 20 min) on chronic neuropathic pain in ten volunteers with complete motor cervical SCI was assessed. The active electrode was placed over the spinal process of the tenth thoracic vertebra and the reference electrode, at the top of the head. Pre- to post-tsDCS intervention changes in pain intensity (numeric rating scale, NRS), patient global assessment, and present pain intensity (PPI) were assessed before and after the tsDCS session (immediately post stimulation, and at 1 and 2 h post stimulation). RESULTS: All participants underwent the stimulation procedure without dropout. Our results showed no significant pre- to post-treatment difference in pain intensity between the active and sham tsDCS groups. Only in the sham tsDCS stimulation, NRS and PPI scores were reduced after the stimulation session. Furthermore, in the mixed effect model analysis, the response in the second period appeared to be more favorable. CONCLUSION: The results suggest that a single session of anodal tsDCS with the montage used in this study is feasible but does not have a significant analgesic effect in individuals with chronic cervical SCI. SPONSORSHIP: The study was funded by Seoul National University Hospital (No. 0420160470) and Korea Workers' Compensation & Welfare Service.