OBJECTIVE: The use of intraoperative neuromonitoring (IONM) has been adapted to address issues of safety and proper lead positioning in spinal cord stimulation. This multicenter case series seeks to incorporate the use of evoked compound action potential (ECAP) and late response (LR) recording and compare it with the results obtained with IONM, specifically electromyography (EMG), for the confirmation of lead placement. This study aimed to establish a correlation between ECAPs, LR, and EMG and publish human recordings of ECAPs and LR during their use with IONM.
METHODS: Standard neuromonitoring protocols were followed at two institutions, with two separate physicians and with seven patients, as part of a larger ongoing study registered with ClinicalTrials.gov (NCT02924129). Stimulation and recording were performed, top and bottom, on each percutaneous lead. Stimulation amplitude was increased considering ECAP, LR, and EMG thresholds.
RESULTS: ECAPs, LRs, and EMG signals were observed in all patients. The onset of LR signals on implanted electrodes and EMG signal on subdermal electrodes was well correlated (rs = 0.94, p < 0.001), with a median LR:EMG value of 1.06 (N = 21). LR:EMG for the top (mean = 0.97, N = 8) vs bottom (mean = 1.15, N = 13) of the lead was compared using a paired Wilcoxon signed rank test and an independent samples Mann-Whitney test, revealing a marginally significant and a statistically significant difference (p = 0.078 and p = 0.015, respectively). Mean LR:ECAP was >2 in all locations and approximately 3.5 overall. LR:ECAP between the top and bottom of the lead was significantly different (Wilcoxon test, p < 0.01, N = 12).
CONCLUSIONS: LR correlated with EMG; leads with bilateral (not necessarily symmetric) EMG activity showed LR:ECAP > 1.5. An LR:ECAP of <1, with LR/EMG generated before the ECAP, indicated that the lead is too lateral. The use of ECAP and LR has the potential of maintaining objective lead placement, without the need for needle placement with IONM.

BACKGROUND: Magnetic resonance imaging (MRI) conditional modes are a novel feature for certain Food and Drug Administration (FDA)-approved spinal cord stimulation (SCS) devices. However, there is a paucity of literature around the limitation of MRI-conditional modes (\"MRI safe\"), specifically in clinical scenarios where urgent MRIs may be needed. One such limitation is load impedance, referring to the circuit\'s resistance to the current being generated by the system. High impedance can limit the MRI-conditional mode capability, presenting potential harm to a patient undergoing an MRI or make an MRI unable to be completed.
METHODS: Three cases were identified, and informed consent was obtained. All information was obtained via retrospective chart review.
RESULTS: In this case series of three patients where MRI-conditional SCS systems were unable to be placed in \"MRI safe\" settings, preventing timely MRI study completion in the setting of high impedance, all three were required to undergo alternative imaging including CT scans, and two patients ultimately had the system explanted and one chose to be re-implanted after completion of scans.
CONCLUSIONS: This case series highlights the need for further investigation of impedance in SCS systems and potential limitations for future MRI usage. The review of literature of impedance in SCS shows both device- and physiologic-related etiologies for changes in impedance that warrant consideration by the implanting physician.

OBJECTIVE: Ten kilohertz spinal cord stimulation (SCS) is usually initiated in a single-bipolar configuration over the radiological reference point T9/T10 intervertebral disc space for neuropathic back and leg pain. Cascade is a duty-cycled, multi-bipolar contact configuration across an entire eight-contact lead. Potential advantages by using a broader area of SCS coverage include mitigation against minor lead migration and a reduction in the need for reprogramming. We report here the results of a retrospective case series of 114 patients using Cascade.
METHODS: Retrospective data were collected over two years. We selected patients with neuropathic back with or without/leg pain who had a trial of SCS. Pain assessments using Numerical Rating Scales (NRS) and Patient Global Impression of Change (PGIC) scores were collected at baseline, six months, and last follow-up beyond 12 months (mean 15.1 months). Patients were programmed with 10 kHz SCS using Cascade during the trial, which was continued unless reporting inadequate pain relief. Morbidity and deviations from Cascade programming were also obtained.
RESULTS: At six months, 87 of 97 (90.6%) patients with active devices were using Cascade and 58 of 72 (81%) patients at the last follow-up >12 months. There was a significant reduction in back NRS (8.3 vs. 3.9 [p < 0.0001], N = 97) and leg pain (7.53 vs. 3.83 [p < 0.0001], N = 77) at 6 months and last follow-up >12 months back (8.3 vs. 3.95 [p < 0.0001] N = 72), leg (7.53 vs. 3.534 [p < 0.0001], N = 58). The PGIC score was 6 of 7 or all of 7 in 72% of patients (70/97) at six months and in 68% (49/72) of patients at the last follow-up beyond 12 months.
CONCLUSIONS: Cascade is an effective programming methodology that may have benefits over a single-bipole configuration for 10 kHz SCS, particularly during a trial of stimulation. Results from this study suggest it is a durable program for patients with neuropathic back and leg pain.

Spinal cord stimulation (SCS) has proven to be a cost-effective treatment for failed back surgery syndrome (FBSS). However, the effect on patients\' working capability remains unclear.
To evaluate the impact of SCS on working capability and to identify the factors behind permanent disability in FBSS patients.
The study group consisted of 198 working-age patients with SCS trialed or implanted for FBSS in a single center between 1996 and 2014. For each patient, 3 living controls, matched by age, gender, and birthplace, were otherwise randomly selected by the Population Register Center. The data on working ability were obtained from the Social Insurance Institution. Patients were divided into 3 groups: SCS trial only, SCS implanted permanently, and SCS implanted but later explanted.
A rehabilitation subsidy was given to 68 patients and 8 controls for a mean of 5.2 (95% confidence interval [CI] 2.4-8.2) and 0.2 (95% CI 0.05-0.6) days per month (P < .05). At the end of follow-up, 16 (37%), 13 (33%), 25 (22%), and 27 (5%) subjects were on disability pension (DP) in the SCS trial, SCS explanted, SCS permanent, and control groups. Patients in the SCS trial-only group were significantly more often on DP than were patients with permanent SCS (odds ratio 2.6; 95% CI 1.2-5.9; P = .02).
Permanent SCS usage was associated with reduced sick leave and DP. Prospective study will be required to assess possible predictive value.

BACKGROUND: Spinal cord stimulation (SCS) is an evidence-based treatment for chronic neuropathic pain; however, there is a dearth of evidence investigating this modality in patients with tethered cord syndrome.
METHODS: We present a case of 55-year-old woman with history of lipo-myelomeningocele repair and multiple detethering surgeries who presented with chronic low back and leg pain accompanied by progressive gait dysfunction. After a successful trial, she underwent SCS paddle lead placement that resulted in decrease of her visual analog scale for pain from 9/10 to 0-2/10 as well as daily opioid intake from 90 to 199 mg morphine-equivalent doses to 40 to 60 mg morphine-equivalent doses. On last follow-up she reported 70%-85% relief of her low back and leg pain, better ambulation, and improved quality of life.
CONCLUSIONS: The literature review identified 2 other case reports of SCS in tethered cord syndrome with similar improvement in pain alleviation.

Current treatment options for bladder disorders of neurogenic etiology often leave unsatisfactory results. Therefore, new and effective treatments must be investigated. High-frequency spinal cord stimulation (HF-SCS) at 10 kHz has proven to be effective in the treatment of refractory chronic back and leg pain.
To evaluate the efficacy of HF-SCS at 10 kHz in alleviating lower urinary tract dysfunction and bladder incontinence in 5 patients with underlying neurological disease or spinal cord injury, through retrospective study.
Urodynamic parameters such as voiding frequency, residual volume, episodes of incontinence, and the patients\' subjective impression impairment of life were assessed and compared pre- and postoperatively. Reduction in pain intensity was assessed as change on the Numeric Rating Scale (NRS).
All 5 patients had significantly positive outcomes. Episodes of leakage per day improved by 83% on average. Quality of life questionnaires and subjective bother scale revealed an improvement of 36% and 57%, respectively. Individual symptoms among the patient group such as residual volume also responded to the treatment as well. Mean pain NRS of 8.6 cm was reduced to 3.9 cm (55%) at 6 mo follow-up.
HF-SCS at 10 kHz significantly alleviated symptoms of neurogenic bladder incontinence in patients suffering from neurological disease or spinal cord injury. However, larger and prospective, randomized studies are necessary to make a clear statement regarding the efficacy of this therapy in lower urinary tract dysfunction and bladder incontinence.

BACKGROUND: Intraoperative neuromonitoring for spinal cord stimulation uses electromyography (EMG) responses to determine myotomal coverage as a marker for dermatomal coverage. These responses are utilized to determine the orientation of the electrode. Somatosensory evoked potential (SSEP) collision testing can also be used in which sensory signals are decreased and/or eliminated when stimulation is activated.
METHODS: Fifteen patients were observed in the study. Each manufacturer had a minimum of three patients. Those included were Abbott BurstDR waveform, Boston Scientific burst stimulation, Medtronic high-dose stimulation, and Nevro high-frequency waveform. Efficacy of therapy was determined by a successful trial. Analysis performed during the permanent implant, included findings with traditional tonic stimulation, specific waveform and stimulation platforms, amplitude differences, and findings for both EMG responses and SSEP collision testing.
RESULTS: The Abbott BurstDR waveform produced the most findings. The amplitudes necessary to generate an observed EMG response were far lower than others, with a threshold of 10-20% of that seen in traditional tonic programming. The Medtronic high-dose programming and Nevro high-frequency waveform did not generate any observable EMG responses. Unique to Abbott BurstDR waveform was the onset of EMG activity in the distal muscle groups prior to proximal ones, as well as a hyperexcitability phenomenon acting as a primer generating signals at lower thresholds with more robust responses when returning to traditional tonic stimulation. EMG responses demonstrated propagation into one large EMG spike with BurstDR, while Boston Scientific burst stimulation had no propagation with separate spikes being consistent with traditional tonic stimulation.
CONCLUSIONS: This observational series demonstrated distinct differences between the waveforms and stimulation alluding to different mechanisms of action. Nevro high-frequency and Abbott BurstDR waveforms appear to be most different in action from traditional tonic stimulation while Abbotts BurstDR appears to be the most energy efficient generating signals at the lowest thresholds with a propagating effect that leads to a hyperexcitable or primed stimulation state.

OBJECTIVE: Spinal cord stimulation (SCS) traditionally is thought to require paresthesia, but there is evidence that paresthesia-free stimulation using high-density (HD) parameters might also be effective. The purpose of this study is to evaluate relative effectiveness of conventional, subthreshold HD, and sham stimulation on pain intensity and quality of life.
METHODS: Fifteen patients with response to conventional stimulation (60 Hz/350 μsec) were screened with a one-week trial of subthreshold HD (1200 Hz/200 μsec/amplitude 90% paresthesia threshold) and enrolled if there was at least 50% reduction on visual analog scale (VAS) for pain. Subjects were randomized into two groups and treated with four two-week periods of conventional, subthreshold HD, and sham stimulation in a randomized crossover design.
RESULTS: Four of 15 patients responded to subthreshold HD stimulation. Mean VAS during conventional, subthreshold HD, and sham stimulation was 5.32 ± 0.63, 2.29 ± 0.41, and 6.31 ± 1.22, respectively. There was a significant difference in pain scores during the blinded crossover study of subthreshold HD vs. sham stimulation (p < 0.05, Student\'s t-test). Post hoc analysis revealed that subjects reported significantly greater attention to pain during conventional stimulation compared with subthreshold HD stimulation (p < 0.05, Student\'s t-test). All subjects reported a positive impression of change for subthreshold HD stimulation compared with conventional stimulation, and there was a trend toward greater likelihood for response to subthreshold HD stimulation in comparison with sham stimulation (p = 0.07, Fisher\'s exact test). At the end of the trial, all subjects elected to continue to receive subthreshold HD stimulation rather than conventional stimulation.
CONCLUSIONS: Paresthesia are not necessary for pain relief using commercially available SCS devices, and may actually increase attention to pain. Subthreshold HD SCS represents a viable alternative to conventional stimulation among patients who are confirmed to have a clinical response to it.

OBJECTIVE: €‚ Postherniorrhaphy pain is a not uncommon, and difficult to treat, pain condition. Success with different methods of neurostimulation has been reported in the literature in the last decade. We assess the use of a new modality of neuromodulation--€”spinal-€peripheral neurostimulation (SPN).
METHODS: €‚ We report the results of treatment of a patient with bilateral, intractable postherniorrhaphy pain with SPN.
RESULTS: €‚ Significant reduction in pain and decrease in opioid consumption have been achieved.
CONCLUSIONS: €‚ SPN can be an effective treatment for postherniorrhaphy pain resistant to conservative management.