Neuromodulation: Technology at the Neural Interface Received: February 10, 2014
Revised: July 1, 2014
Accepted: July 22, 2014
(onlinelibrary.wiley.com) DOI: 10.1111/ner.12237
The Use of 10-Kilohertz Spinal Cord Stimulation in a Cohort of Patients With Chronic Neuropathic Limb Pain Refractory to Medical Management Adnan Al-Kaisy, MD; Stefano Palmisani, MD; Tom Smith, MD; Stephany Harris, RN; David Pang, MD Objective: It is the purpose of this study to document our experience with the use of a 10-kHz high-frequency spinal cord stimulation (SCS) device for the relief of neuropathic pain of the upper and lower limbs. Materials and Methods: A retrospective chart review was performed of all patients treated with the 10-kHz high-frequency SCS system for neuropathic pain (upper or lower limb) refractory to conventional treatment. All patients underwent a trial with one or two eight-contact percutaneous leads using 50-Hz traditional stimulation. If ≥80% paresthesia coverage of the painful area with traditional SCS was obtained, high-frequency 10-kHz SCS was used. Patients who had a significant reduction in pain score (≥50%) at the end of the trial received a permanent implant and were then followed for up to six months. Outcome measures included a numeric rating scale for pain, the Brief Pain Inventory, health-related quality of life (EQ-5D), the Pain Catastrophizing Scale, and patient satisfaction. Results: Fifteen patients completed a trial of high-frequency 10-kHz SCS. Eleven patients proceeded to permanent implantation. Ten of the 11 patients who proceeded to full implantation had significant reductions in all of the collected outcome variables at one, three, and six months. Conclusions: In this small cohort of patients, high-frequency 10-kHz SCS reduced pain and improved quality of life. However, before we can conclude that high-frequency 10-kHz SCS for neuropathic pain of the upper and lower extremities is efficacious, a large-scale multicenter observational study should be performed to corroborate our small retrospective study. Keywords: 10-kilohertz frequency, neuropathic pain, spinal cord stimulation Conflict of Interest: Drs. Al-Kaisy and Smith have received speaker fees and travel sponsorship from Nevro Corp. Dr. Palmisani has received travel sponsorship from Nevro Corp. and Medtronic, Inc. Dr. Pang has received travel sponsorship from Medtronic, Inc. Mrs. Harris has received travel sponsorship from Nevro Corp.
INTRODUCTION
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Chronic neuropathic pain syndromes result from peripheral or central nerve lesions or neural dysfunction due either to traumatic events (e.g., amputation, spinal cord injury) or to systemic disease (e.g., diabetes, viral infection, and cancer) (1). Established pharmacological treatments for neuropathic pain achieve effective pain relief in only one-third of treated patients, and adverse events are frequent (2). This neuropathic pain is often associated with a significant disruption of quality of life, and studies show a three-fold increase in health-care costs of patients with neuropathic pain when compared with matched controls (3). For those patients who do not respond to conservative medical and rehabilitation therapy or cannot tolerate side-effects of pharmacologic management, neuromodulation therapies such as spinal cord stimulation (SCS) should be considered. SCS is an evidence-based, cost-effective treatment for chronic neuropathic pain (4), and the National Institute for Health and Clinical Excellence (NICE) of the United Kingdom recommends it for the treatment of chronic www.neuromodulationjournal.com
neuropathic pain conditions such as residual radiculopathy with failed back surgery syndrome (FBSS) and complex regional pain syndrome (CRPS) (5). With traditional SCS, electrodes are placed in the posterior epidural space so that stimulation of the dorsal columns of the spinal cord results in paresthesia (6,7). Analgesia is achieved by inducing paresthesia overlapping the anatomical site of pain. However, this paresthesia can be uncomfortable or even intolerable to some
Address correspondence to: Adnan Al-Kaisy, MD, Pain Management and Neuromodulation Centre, Guy’s and St Thomas’ Hospital, Westminster Bridge Road, London SE1 7EH, UK. Email: [email protected] Pain Management and Neuromodulation Centre, Guy’s and St Thomas’ Hospital, London, UK For more information on author guidelines, an explanation of our peer review process, and conflict of interest informed consent policies, please go to http:// www.wiley.com/bw/submit.asp?ref=1094-7159&site=1
© 2014 International Neuromodulation Society
Neuromodulation 2015; 18: 18–23
10-KHZ SCS FOR CHRONIC NEUROPATHIC LIMB PAIN patients (8). Long-term paresthesia coverage of the painful area can be difficult to achieve due to inadvertent migration of the electrode, but this risk has been reduced by the introduction of newer techniques (9–11). In contrast, the high-frequency SCS system (SENZA, Nevro Corp., Menlo Park, CA, USA) delivers stimulation frequencies up to 10 kHz and has the ability to provide pain relief without producing paresthesia. Van Buyten et al. (12) published the results of a multicenter study reporting their initial outcomes using the high-frequency system at 10 kHz for patients with primary back pain with or without leg pain. The authors reported significant improvement in pain relief and functioning. There was no paresthesia or movement-induced dysesthesia, and the patients did not experience painful stimulation. Sleep duration and quality of sleep improved. Al-Kaisy et al. (13) reported on the 24-month outcomes, demonstrating the long-term safety of this therapy and its sustained efficacy for both back and lower limb pain. We present here a retrospective chart review of our six-monthpost-implant data on SCS using the high-frequency SCS device at 10 kHz for chronic neuropathic pain of lower or upper limbs refractory to common physical and medical management. This high frequency 10-kHz SCS device is CE-marked for both 10-kHz stimulation and conventional stimulation with frequencies below 1.2 kHz.
METHODS We retrospectively reviewed the medical records of all patients who underwent a trial with high-frequency 10-kHz SCS for neuropathic pain. Under United Kingdom guidelines, this study, as an anonymous audit of outcomes, did not require ethics committee approval (14).
institution practice. We used a tunneled-trial approach for the majority of our patients, as we found that good stimulation coverage during a percutaneous trial was occasionally difficult to replicate during full implantation. Access to the epidural space was achieved using a modified Tuohy needle and loss-of-resistance technique. Either one or two eight-contact leads (Nevro Corp., Menlo Park, CA, USA) were placed into the epidural space using standard techniques under fluoroscopy. For lower extremity neuropathic pain, the lead or leads were introduced at either the L2–3 or L3–4 intervertebral space and the tip of the lead advanced rostrally to the T8–12 vertebral levels. For upper extremity neuropathic pain, the lead or leads were introduced at the T4–5 level, and the tip of the lead was advanced to C2–7 (Figs. 1 and 2). In this study, intraoperative testing was performed to help explore optimal stimulation targets for upper and lower limb pain. The large area covered by the electrodes allows us to test a variety of stimulation points and gives the patients an option of using conventional stimulation. Paresthesia overlapping the painful territory was induced through traditional constantcurrent stimulation (rate 50–60 Hz, pulse width 250–450 μs, amplitude 0.5–4.5 mA) in accordance with standard practice (17). This traditional method of lead placement was used to ensure that in case of suboptimal results with high-frequency 10-kHz stimulation, the same leads could be used for traditional SCS therapy. After placement of the trial lead or leads into the epidural space, a ≥80% paresthesia overlap of the patients’ pain was sought using 50-Hz traditional SCS. Thereafter, stimulation was changed to a bipolar configuration, and frequency was increased to 10 kHz for the duration of the trial and, if the trial was successful, during permanent stimulation. After implantation all leads were anchored either to the skin in the case of a percutaneous, trial or to the supraspinal ligament in the case of a tunneled trial and
Patient Selection In accordance with the NICE guidelines for treatment of chronic pain of neuropathic origin with SCS (5), a trial of SCS was proposed to patients referred to our tertiary pain management referral centre with a diagnosis of chronic neuropathic pain predominantly involving the upper or lower limbs. Patients were considered to have neuropathic pain when 1) a definite lesion or injury of the somatosensory system was associated with the onset of pain symptomatology; 2) the pain was confined to part of or the entire innervation territory of the affected nervous structure; 3) clinical examination revealed the presence of multiple positive and/or negative somatosensory signs (hyperalgesia, allodynia, etc.); and 4) the use of a neuropathic pain screening tool (painDETECT) suggested a strong neuropathic component (15) to the patient’s pain complaint. In those patients where a diagnosis of CRPS was suspected, the revised Budapest diagnostic criteria were applied, and patients were classified accordingly (16). All patients included in this case series had failed appropriate conventional management for neuropathic pain, including medication management with analgesic medications, tricyclic antidepressants, anticonvulsants, opioids, transcutaneous electrical nerve stimulation, and topical treatments (lidocaine plasters, capsaicin cream). Many of the patients have had pain management programmes, as well as rehabilitation based on cognitive–behavioural therapy.
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Figure 1. X-ray image of electrodes placed in the epidural space: optimal placement for lower limb neuropathic pain with leads at T10–11–12.
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Implant Technique Epidural trial lead placement was performed either percutaneously or through a small skin incision (tunneled-trial) as per our
AL-KAISY ET AL.
Table 1. Baseline Demographics (N = 11). Age (years) Sex Male Female NRS BPI PainDETECT PCS Lower limb Chronic postsurgery neuropathic pain CRPS Upper limb Chronic postsurgery neuropathic pain CRPS
46 ± 12 5 6 8.2 ± 1.7 57.6 ± 9.4 29 ± 8 33 ± 11 3 0 5 3
NRS, numeric rating scale; BPI, brief pain index; PCS, Pain Catastrophizing Scale; CRPS, complex regional pain syndrome.
Figure 2. X-ray image of electrodes placed in the epidural space: optimal placement for neuropathic pain of the upper limbs with leads from C3 to C6.
connected to an external trial system. During trial stimulation, each patient was given the opportunity to try at least three different high-frequency 10-kHz SCS programs, each one with a preset range of intensities, for a total of 7 to 10 days. In the case of a negative trial, the patients received a one-week trial with traditional SCS. Implantation of the permanent high-frequency 10-kHz SCS system in the positively responding patients who underwent a “tunneled” trial was achieved by connecting the distal end of the implanted leads to new tunneled extension cables connected to the high-frequency 10-kHz implantable pulse generator (IPG). The IPG was inserted in a surgically created subcutaneous pocket, either in the anterior abdominal wall or over the superior gluteal region. In those patients who received a percutaneous trial, the lead or leads were removed and, after a delay of three weeks, were permanently reimplanted, as performed with the “tunneled” trial. Perioperative antibiotic coverage was always administered per our standard practice as recommended by guidelines for SCS implantation (18).
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Outcome Measures Baseline measures (Table 1) were collected the week before the trial, and outcome measures were collected at the end of trial and then at one, three, and six months after implantation of a permanent system. Pain scores were assessed by a numeric rating scale (NRS) (19) ranging from 0 (no pain) to 10 (worst imaginable pain). The Brief Pain Inventory (BPI) questionnaire was used to measure both the intensity and impact of pain on the patient’s life (20); the Pain Catastrophizing Scale (PCS) was used to measure catastrophic thinking related to pain (21); the EQ-5D was used for health-related quality of life measurements (22); and the www.neuromodulationjournal.com
painDETECT questionnaire was used as a baseline screening tool to establish whether the reported pain was neuropathic in nature or not (14). At the six-month follow-up visit, patients were asked to what extent they were satisfied with the treatment and its results and if they would recommend this type of treatment to others. Statistics Descriptive analysis was performed, and data are presented as means and standard deviations from the means (SD) or median and interquartile range (IQR) as appropriate. Differences from baseline were compared for continuous variables using the independentsample Student’s t-test. A p-value of ≤0.05 was considered to indicate statistical significance.
RESULTS Fifteen patients with chronic neuropathic pain completed a trial of high-frequency 10-kHz SCS. Demographic data are presented in Table 1. Thirteen of 15 patients had a baseline painDETECT score of greater than 19 (mean 28.9 ± 8.4), indicating a strong neuropathic component to their chronic pain complaint. Nine of 15 patients were diagnosed with either upper limb neuropathic pain (N = 6) or hand CRPS (N = 3), while six patients had a diagnosis of postsurgery knee or foot neuropathic pain (N = 3) or foot CRPS (N = 3). Eleven of 15 patients (73%) reported at least 50% pain relief from the trial and proceeded to full implantation. The data reported hereunder are relative to the 11 patients with permanent implantation. Anatomical level of stimulation and amplitudes of stimulation are reported in Table 2, along with pain relief at six months post-IPG implantation. In four patients, the high-frequency 10-kHz SCS trial phase did not result in adequate pain relief, and they also failed an additional week of traditional SCS despite adequate paresthesia coverage of the affected area. Of note, none of the patients with foot CRPS had a positive high-frequency 10-kHz SCS trial phase, whereas the three patients suffering from CRPS of the hand responded. The mean NRS pain score decreased from 8.2 ± 1.7 at baseline to 2.5 ± 0.9 at one-month follow-up, 2.9 ± 1.8 at three months, and 3.3 ± 1.7 at six months (p < 0.05)—NRS reductions of 68%, 65%, and 59% respectively (Fig. 3).
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10-KHZ SCS FOR CHRONIC NEUROPATHIC LIMB PAIN
Table 2. Eleven Patients Who Underwent Permanent High-Frequency 10-kHz SCS.
1 2 3 4 5 6 7 8 9 10 11
Location
Level of stimulation
10 -kHz amplitude (mA)
10-kHz paresthesia threshold (mA)
Relief (%)
Patient satisfaction
Hand Knee Knee Hand Hand Upper limb Upper limb Hand Foot and leg Upper limbs Hand
C2/3 disk T11/12 disk T10/11 disk C3/4 disk C2/3 disk Top C6 C4 body C2 body Bottom T9 C2 body C3/C4 disk
1–3 0.5–3.5 1–3 1–2.5 0.5–3.0 1–3.5 1.5–3 0.5–3 0.5–3.5 1.5–2.2 0.5–2.5
>7 >7 >7 4 >7 >7 >7 >7 >5 >4.5 2.7
55 50 55 30 >90 65 90
Good Excellent Good Good Excellent Excellent Not satisfied Good Good Excellent Excellent
DISCUSSION
Figure 3. Numeric rating scale at baseline and at one month, three months, and six months after permanent implantation of the 10-kHz-frequency spinal cord stimulation system.
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Safety of High-Frequency 10-kHz SCS Both the European multicenter study at two years (13) and the Tiede et al. multicenter trial in the USA (24) were without neurologic adverse events related to the use of high-frequency 10-kHz SCS. Preclinical work has also confirmed the safety of continuous highfrequency 10-kHz SCS in an animal model (25). Our study is, to our knowledge, the first to report clinical results in patients implanted with cervical leads using high-frequency 10-kHz SCS, and confirms the safety of its use.
Efficacy of High-Frequency 10-kHz SCS More than 50% pain relief was achieved in 11 out of 15 trialed patients in our audit and case series. This matches or exceeds the results seen with traditional SCS systems used in similar settings (26–28). In fact, despite high-frequency 10-kHz SCS being a paresthesia-free system, we noted that most patients reported significant relief only when stimulated in a specific area of the spinal cord; see Table 2. The placement of the tip of the lead at C3–C4 for high-frequency 10-kHz SCS was found to be the ideal area for neuropathic pain of the upper limb/hand and placement at T8–T12 to be best for the lower limb. Also observed, in line with other studies (12,24), was that pain relief developed only after a latent period of some hours. The importance of localizing the site of stimulation without the aid of immediate sensory feedback (paresthesia) from the patient led us to develop a therapy algorithm to maximize pain relief. This algorithm included post-implant x-rays to detect any lead migration and testing at traditional frequencies (50 Hz) for paresthesia location to
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The mean BPI at baseline was 57.56 ± 9.42 for all patients. For nine of 11 patients, the mean BPI at one month was 27 ± 11, and at three months it was 22.4 ± 15.32. For 10 of 11 patients, the mean BPI at six months was 29.4 ± 14.5 (it should be noted that one patient was an outlier at six months with a BPI value of 2). A reduction in the PCS was observed at each follow-up period (from 33 ± 11 at baseline to 7 ± 7, 7 ± 5, and 7 ± 6, respectively). EQ-5D time trade-off score (23) increased by an average of 116% at one month, 124% at three months, and 101% at six months, underscoring an improvement in QOL after implantation of the high-frequency 10-kHz SCS device. With only one exception, all patients rated the therapy with high-frequency 10 kHz SCS as excellent or good and would recommend the procedure to other patients. One patient with good pain relief during the tunneled percutaneous trial developed an infection of the implant site, requiring removal of the leads and planned permanent reimplantation of the High frequency system six months later. Two patients required surgical revision of the system due to lead migration, with one patient regaining earlier pain relief levels following the revision. The other patient, after a fall, failed to respond to programming and both high-frequency and conventional SCS revision. Three patients complained of transient pain at the site of the IPG. No adverse neurologic events related to high-frequency 10-kHz SCS were observed. During the high-frequency 10-kHz SCS phase of the trials, none of the patients perceived paresthesia.
This retrospective case series is the first of its kind to report the use of high-frequency 10-kHz SCS for the treatment of chronic neuropathic limb pain. To date, reports on the same technology have focused primarily on FBSS with or without leg pain. These initial studies show paresthesia-free pain relief with associated improvements in disability and sleep (12,13,24). In our series, highfrequency 10-kHz SCS was effective in reducing neuropathic pain affecting the upper or lower limbs, increasing patients’ quality of life, and reducing patients’ catastrophic thinking related to their pain experience.
AL-KAISY ET AL. help explore optimal stimulation locations for high-frequency 10-kHz SCS therapy. In some cases, pain relief was lost despite no documented lead migration (x-rays and 50-Hz paresthesia testing), but we were able to reachieve the previous pain relief by stimulating at a different vertebral level. Paresthesia Traditional spinal cord stimulation at rates lower than 1.2 kHz requires perceived paresthesia within the area of pain to be clinically effective (6,7,17). As a consequence, traditional SCS analgesia demands achieving optimum paresthesia coverage intraoperatively and maintaining it over time. The intraoperative phase of placing traditional SCS systems can be time-consuming (7) and unpleasant to patients, and the accuracy of stimulation can be affected by sedation. These steps are minimized with experienced operators, but if they can be removed, the whole procedure can be simplified. A further problem with the paresthesia required for efficacy of traditional SCS is that up to 71% of traditional SCS users find stimulation to be uncomfortable at times (8). The discomfort, for instance movement-related dysesthesia, requires many patients to adjust their stimulation level based on posture and may prevent them benefiting from the system at night during sleep or driving. High-frequency 10-kHz SCS has previously been shown to be a paresthesia-free SCS system (12,24), which is corroborated by our retrospective study. Removal of unnecessary intraoperative testing will simplify the whole implantation process. This was seen in patients enrolled in the back pain trial of Van Buyten et al. (12), where the investigators already knew which spinal cord segments were likely to yield positive response to high-frequency 10-kHz SCS. However, when we performed our first high-frequency 10-kHz SCS implantation, there was no information regarding optimal spinal cord levels for the use of this system for neuropathic pain of the upper or lower extremities. Despite the small numbers of patients in this case series, we were able to identify optimal vertebral stimulation levels for both cervical and thoracic high-frequency 10-kHz SCS (spinal cord mapping for high-frequency 10-kHz SCS for neuropathic pain); see Table 2. Also of interest is that when stimulated with appropriate traditional-frequency SCS settings, most of the areas determined to be optimal for high-frequency 10-kHz SCS produce a paresthesia-like sensation that partially overlaps the patients’ painful regions.
CONCLUSION In our case series, high-frequency 10-kHz SCS was shown to be a paresthesia-free and effective option for the treatment of upper and lower limb neuropathic pain. We also believe that our small, retrospective chart review analysis must be corroborated by either prospective randomized controlled studies or large-scale multicenter observational studies in this population of patients with neuropathic pain before it can be concluded that high-frequency 10-kHz SCS is both safe and effective in this population.
Acknowledgements
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Eric Bulogne from Nevro Corporation provided assistance in writing this manuscript. We received editorial support from Dr. Elliot Krames, who is a paid consultant of Nevro Corporation. The patients were all seen at the Pain Management and Neuromodulation Centre, Guy’s and St Thomas’ Hospital, London, UK. www.neuromodulationjournal.com
Authorship Statements All authors contributed to the design, data collection, recruitment, analysis, and writing of the manuscript. All authors have reviewed the final version and consented to publication.
How to Cite this Article: Al-Kaisy A., Palmisani S., Smith T., Harris S., Pang D. 2015. The Use of 10-Kilohertz Spinal Cord Stimulation in a Cohort of Patients With Chronic Neuropathic Limb Pain Refractory to Medical Management. Neuromodulation 2015; 18: 18–23
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10-KHZ SCS FOR CHRONIC NEUROPATHIC LIMB PAIN 24. Tiede J, Brown L, Gekht G, Vallejo R, Yearwood T, Morgan D. Novel spinal cord stimulation parameters in patients with predominant back pain. Neuromodulation 2013;16:370–375. 25. Butt M, Alataris K, Walker A, Tiede J. Histological findings using novel stimulation parameters in a caprine model. Eur J Pain Suppl 2011;5:188–189. 26. Kemler MA, Barendse GA, van Kleef M et al. Spinal cord stimulation in patients with chronic reflex sympathetic dystrophy. N Engl J Med 2000;343:618–624. 27. Pluijms WA, Slangen R, Bakkers M et al. Pain relief and quality-of-life improvement after spinal cord stimulation in painful diabetic polyneuropathy: a pilot study. Br J Anaesth 2012;109:623–629. 28. Kumar K, Taylor RS, Jacques L et al. Spinal cord stimulation versus conventional medical management for neuropathic pain: a multicentre randomised controlled trial in patients with failed back surgery syndrome. Pain 2007;132:179– 188.
COMMENT The authors of this paper present and important, albeit very preliminary, small and short-term, experience with high frequency spinal cord stimulation (HF SCS) in treatment of pain in extremities. Currently, HF SCS is considered primarily for lower back pain—and the main reason for this indication has been low efficacy of conventional SCS and other approaches. For pain in extremities, on the other hand, conventional
SCS does work, and I am somewhat skeptical, in absence of prospective comparative study, about moving to paresthesia-free stimulation for extremity pain syndromes. Moreover, the authors’ approach in using conventional stimulation to define optimal location or HF SCS electrodes contradicts all previous research that postulated existence of alternative pathways and targets that produce pain relief without paresthesias. Nevertheless, I feel that the testing approach described here may be tried even for low back pain in order to define better contact location and better long-term responders. Perhaps with better understanding of correlation between two approaches to stimulation (paresthesia-based and paresthesia-free) we will be able to determine better indications for each. It is also possible that a combination of different paradigms will be more effective for particularly complex patients and pain patterns. Konstantin V. Slavin, MD Chicago, IL, USA
Comments not included in the Early View version of this paper.
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© 2014 International Neuromodulation Society
Neuromodulation 2015; 18: 18–23
Revised: July 1, 2014
Accepted: July 22, 2014
(onlinelibrary.wiley.com) DOI: 10.1111/ner.12237
The Use of 10-Kilohertz Spinal Cord Stimulation in a Cohort of Patients With Chronic Neuropathic Limb Pain Refractory to Medical Management Adnan Al-Kaisy, MD; Stefano Palmisani, MD; Tom Smith, MD; Stephany Harris, RN; David Pang, MD Objective: It is the purpose of this study to document our experience with the use of a 10-kHz high-frequency spinal cord stimulation (SCS) device for the relief of neuropathic pain of the upper and lower limbs. Materials and Methods: A retrospective chart review was performed of all patients treated with the 10-kHz high-frequency SCS system for neuropathic pain (upper or lower limb) refractory to conventional treatment. All patients underwent a trial with one or two eight-contact percutaneous leads using 50-Hz traditional stimulation. If ≥80% paresthesia coverage of the painful area with traditional SCS was obtained, high-frequency 10-kHz SCS was used. Patients who had a significant reduction in pain score (≥50%) at the end of the trial received a permanent implant and were then followed for up to six months. Outcome measures included a numeric rating scale for pain, the Brief Pain Inventory, health-related quality of life (EQ-5D), the Pain Catastrophizing Scale, and patient satisfaction. Results: Fifteen patients completed a trial of high-frequency 10-kHz SCS. Eleven patients proceeded to permanent implantation. Ten of the 11 patients who proceeded to full implantation had significant reductions in all of the collected outcome variables at one, three, and six months. Conclusions: In this small cohort of patients, high-frequency 10-kHz SCS reduced pain and improved quality of life. However, before we can conclude that high-frequency 10-kHz SCS for neuropathic pain of the upper and lower extremities is efficacious, a large-scale multicenter observational study should be performed to corroborate our small retrospective study. Keywords: 10-kilohertz frequency, neuropathic pain, spinal cord stimulation Conflict of Interest: Drs. Al-Kaisy and Smith have received speaker fees and travel sponsorship from Nevro Corp. Dr. Palmisani has received travel sponsorship from Nevro Corp. and Medtronic, Inc. Dr. Pang has received travel sponsorship from Medtronic, Inc. Mrs. Harris has received travel sponsorship from Nevro Corp.
INTRODUCTION
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Chronic neuropathic pain syndromes result from peripheral or central nerve lesions or neural dysfunction due either to traumatic events (e.g., amputation, spinal cord injury) or to systemic disease (e.g., diabetes, viral infection, and cancer) (1). Established pharmacological treatments for neuropathic pain achieve effective pain relief in only one-third of treated patients, and adverse events are frequent (2). This neuropathic pain is often associated with a significant disruption of quality of life, and studies show a three-fold increase in health-care costs of patients with neuropathic pain when compared with matched controls (3). For those patients who do not respond to conservative medical and rehabilitation therapy or cannot tolerate side-effects of pharmacologic management, neuromodulation therapies such as spinal cord stimulation (SCS) should be considered. SCS is an evidence-based, cost-effective treatment for chronic neuropathic pain (4), and the National Institute for Health and Clinical Excellence (NICE) of the United Kingdom recommends it for the treatment of chronic www.neuromodulationjournal.com
neuropathic pain conditions such as residual radiculopathy with failed back surgery syndrome (FBSS) and complex regional pain syndrome (CRPS) (5). With traditional SCS, electrodes are placed in the posterior epidural space so that stimulation of the dorsal columns of the spinal cord results in paresthesia (6,7). Analgesia is achieved by inducing paresthesia overlapping the anatomical site of pain. However, this paresthesia can be uncomfortable or even intolerable to some
Address correspondence to: Adnan Al-Kaisy, MD, Pain Management and Neuromodulation Centre, Guy’s and St Thomas’ Hospital, Westminster Bridge Road, London SE1 7EH, UK. Email: [email protected] Pain Management and Neuromodulation Centre, Guy’s and St Thomas’ Hospital, London, UK For more information on author guidelines, an explanation of our peer review process, and conflict of interest informed consent policies, please go to http:// www.wiley.com/bw/submit.asp?ref=1094-7159&site=1
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10-KHZ SCS FOR CHRONIC NEUROPATHIC LIMB PAIN patients (8). Long-term paresthesia coverage of the painful area can be difficult to achieve due to inadvertent migration of the electrode, but this risk has been reduced by the introduction of newer techniques (9–11). In contrast, the high-frequency SCS system (SENZA, Nevro Corp., Menlo Park, CA, USA) delivers stimulation frequencies up to 10 kHz and has the ability to provide pain relief without producing paresthesia. Van Buyten et al. (12) published the results of a multicenter study reporting their initial outcomes using the high-frequency system at 10 kHz for patients with primary back pain with or without leg pain. The authors reported significant improvement in pain relief and functioning. There was no paresthesia or movement-induced dysesthesia, and the patients did not experience painful stimulation. Sleep duration and quality of sleep improved. Al-Kaisy et al. (13) reported on the 24-month outcomes, demonstrating the long-term safety of this therapy and its sustained efficacy for both back and lower limb pain. We present here a retrospective chart review of our six-monthpost-implant data on SCS using the high-frequency SCS device at 10 kHz for chronic neuropathic pain of lower or upper limbs refractory to common physical and medical management. This high frequency 10-kHz SCS device is CE-marked for both 10-kHz stimulation and conventional stimulation with frequencies below 1.2 kHz.
METHODS We retrospectively reviewed the medical records of all patients who underwent a trial with high-frequency 10-kHz SCS for neuropathic pain. Under United Kingdom guidelines, this study, as an anonymous audit of outcomes, did not require ethics committee approval (14).
institution practice. We used a tunneled-trial approach for the majority of our patients, as we found that good stimulation coverage during a percutaneous trial was occasionally difficult to replicate during full implantation. Access to the epidural space was achieved using a modified Tuohy needle and loss-of-resistance technique. Either one or two eight-contact leads (Nevro Corp., Menlo Park, CA, USA) were placed into the epidural space using standard techniques under fluoroscopy. For lower extremity neuropathic pain, the lead or leads were introduced at either the L2–3 or L3–4 intervertebral space and the tip of the lead advanced rostrally to the T8–12 vertebral levels. For upper extremity neuropathic pain, the lead or leads were introduced at the T4–5 level, and the tip of the lead was advanced to C2–7 (Figs. 1 and 2). In this study, intraoperative testing was performed to help explore optimal stimulation targets for upper and lower limb pain. The large area covered by the electrodes allows us to test a variety of stimulation points and gives the patients an option of using conventional stimulation. Paresthesia overlapping the painful territory was induced through traditional constantcurrent stimulation (rate 50–60 Hz, pulse width 250–450 μs, amplitude 0.5–4.5 mA) in accordance with standard practice (17). This traditional method of lead placement was used to ensure that in case of suboptimal results with high-frequency 10-kHz stimulation, the same leads could be used for traditional SCS therapy. After placement of the trial lead or leads into the epidural space, a ≥80% paresthesia overlap of the patients’ pain was sought using 50-Hz traditional SCS. Thereafter, stimulation was changed to a bipolar configuration, and frequency was increased to 10 kHz for the duration of the trial and, if the trial was successful, during permanent stimulation. After implantation all leads were anchored either to the skin in the case of a percutaneous, trial or to the supraspinal ligament in the case of a tunneled trial and
Patient Selection In accordance with the NICE guidelines for treatment of chronic pain of neuropathic origin with SCS (5), a trial of SCS was proposed to patients referred to our tertiary pain management referral centre with a diagnosis of chronic neuropathic pain predominantly involving the upper or lower limbs. Patients were considered to have neuropathic pain when 1) a definite lesion or injury of the somatosensory system was associated with the onset of pain symptomatology; 2) the pain was confined to part of or the entire innervation territory of the affected nervous structure; 3) clinical examination revealed the presence of multiple positive and/or negative somatosensory signs (hyperalgesia, allodynia, etc.); and 4) the use of a neuropathic pain screening tool (painDETECT) suggested a strong neuropathic component (15) to the patient’s pain complaint. In those patients where a diagnosis of CRPS was suspected, the revised Budapest diagnostic criteria were applied, and patients were classified accordingly (16). All patients included in this case series had failed appropriate conventional management for neuropathic pain, including medication management with analgesic medications, tricyclic antidepressants, anticonvulsants, opioids, transcutaneous electrical nerve stimulation, and topical treatments (lidocaine plasters, capsaicin cream). Many of the patients have had pain management programmes, as well as rehabilitation based on cognitive–behavioural therapy.
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Figure 1. X-ray image of electrodes placed in the epidural space: optimal placement for lower limb neuropathic pain with leads at T10–11–12.
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Implant Technique Epidural trial lead placement was performed either percutaneously or through a small skin incision (tunneled-trial) as per our
AL-KAISY ET AL.
Table 1. Baseline Demographics (N = 11). Age (years) Sex Male Female NRS BPI PainDETECT PCS Lower limb Chronic postsurgery neuropathic pain CRPS Upper limb Chronic postsurgery neuropathic pain CRPS
46 ± 12 5 6 8.2 ± 1.7 57.6 ± 9.4 29 ± 8 33 ± 11 3 0 5 3
NRS, numeric rating scale; BPI, brief pain index; PCS, Pain Catastrophizing Scale; CRPS, complex regional pain syndrome.
Figure 2. X-ray image of electrodes placed in the epidural space: optimal placement for neuropathic pain of the upper limbs with leads from C3 to C6.
connected to an external trial system. During trial stimulation, each patient was given the opportunity to try at least three different high-frequency 10-kHz SCS programs, each one with a preset range of intensities, for a total of 7 to 10 days. In the case of a negative trial, the patients received a one-week trial with traditional SCS. Implantation of the permanent high-frequency 10-kHz SCS system in the positively responding patients who underwent a “tunneled” trial was achieved by connecting the distal end of the implanted leads to new tunneled extension cables connected to the high-frequency 10-kHz implantable pulse generator (IPG). The IPG was inserted in a surgically created subcutaneous pocket, either in the anterior abdominal wall or over the superior gluteal region. In those patients who received a percutaneous trial, the lead or leads were removed and, after a delay of three weeks, were permanently reimplanted, as performed with the “tunneled” trial. Perioperative antibiotic coverage was always administered per our standard practice as recommended by guidelines for SCS implantation (18).
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Outcome Measures Baseline measures (Table 1) were collected the week before the trial, and outcome measures were collected at the end of trial and then at one, three, and six months after implantation of a permanent system. Pain scores were assessed by a numeric rating scale (NRS) (19) ranging from 0 (no pain) to 10 (worst imaginable pain). The Brief Pain Inventory (BPI) questionnaire was used to measure both the intensity and impact of pain on the patient’s life (20); the Pain Catastrophizing Scale (PCS) was used to measure catastrophic thinking related to pain (21); the EQ-5D was used for health-related quality of life measurements (22); and the www.neuromodulationjournal.com
painDETECT questionnaire was used as a baseline screening tool to establish whether the reported pain was neuropathic in nature or not (14). At the six-month follow-up visit, patients were asked to what extent they were satisfied with the treatment and its results and if they would recommend this type of treatment to others. Statistics Descriptive analysis was performed, and data are presented as means and standard deviations from the means (SD) or median and interquartile range (IQR) as appropriate. Differences from baseline were compared for continuous variables using the independentsample Student’s t-test. A p-value of ≤0.05 was considered to indicate statistical significance.
RESULTS Fifteen patients with chronic neuropathic pain completed a trial of high-frequency 10-kHz SCS. Demographic data are presented in Table 1. Thirteen of 15 patients had a baseline painDETECT score of greater than 19 (mean 28.9 ± 8.4), indicating a strong neuropathic component to their chronic pain complaint. Nine of 15 patients were diagnosed with either upper limb neuropathic pain (N = 6) or hand CRPS (N = 3), while six patients had a diagnosis of postsurgery knee or foot neuropathic pain (N = 3) or foot CRPS (N = 3). Eleven of 15 patients (73%) reported at least 50% pain relief from the trial and proceeded to full implantation. The data reported hereunder are relative to the 11 patients with permanent implantation. Anatomical level of stimulation and amplitudes of stimulation are reported in Table 2, along with pain relief at six months post-IPG implantation. In four patients, the high-frequency 10-kHz SCS trial phase did not result in adequate pain relief, and they also failed an additional week of traditional SCS despite adequate paresthesia coverage of the affected area. Of note, none of the patients with foot CRPS had a positive high-frequency 10-kHz SCS trial phase, whereas the three patients suffering from CRPS of the hand responded. The mean NRS pain score decreased from 8.2 ± 1.7 at baseline to 2.5 ± 0.9 at one-month follow-up, 2.9 ± 1.8 at three months, and 3.3 ± 1.7 at six months (p < 0.05)—NRS reductions of 68%, 65%, and 59% respectively (Fig. 3).
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10-KHZ SCS FOR CHRONIC NEUROPATHIC LIMB PAIN
Table 2. Eleven Patients Who Underwent Permanent High-Frequency 10-kHz SCS.
1 2 3 4 5 6 7 8 9 10 11
Location
Level of stimulation
10 -kHz amplitude (mA)
10-kHz paresthesia threshold (mA)
Relief (%)
Patient satisfaction
Hand Knee Knee Hand Hand Upper limb Upper limb Hand Foot and leg Upper limbs Hand
C2/3 disk T11/12 disk T10/11 disk C3/4 disk C2/3 disk Top C6 C4 body C2 body Bottom T9 C2 body C3/C4 disk
1–3 0.5–3.5 1–3 1–2.5 0.5–3.0 1–3.5 1.5–3 0.5–3 0.5–3.5 1.5–2.2 0.5–2.5
>7 >7 >7 4 >7 >7 >7 >7 >5 >4.5 2.7
55 50 55 30 >90 65 90
Good Excellent Good Good Excellent Excellent Not satisfied Good Good Excellent Excellent
DISCUSSION
Figure 3. Numeric rating scale at baseline and at one month, three months, and six months after permanent implantation of the 10-kHz-frequency spinal cord stimulation system.
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Safety of High-Frequency 10-kHz SCS Both the European multicenter study at two years (13) and the Tiede et al. multicenter trial in the USA (24) were without neurologic adverse events related to the use of high-frequency 10-kHz SCS. Preclinical work has also confirmed the safety of continuous highfrequency 10-kHz SCS in an animal model (25). Our study is, to our knowledge, the first to report clinical results in patients implanted with cervical leads using high-frequency 10-kHz SCS, and confirms the safety of its use.
Efficacy of High-Frequency 10-kHz SCS More than 50% pain relief was achieved in 11 out of 15 trialed patients in our audit and case series. This matches or exceeds the results seen with traditional SCS systems used in similar settings (26–28). In fact, despite high-frequency 10-kHz SCS being a paresthesia-free system, we noted that most patients reported significant relief only when stimulated in a specific area of the spinal cord; see Table 2. The placement of the tip of the lead at C3–C4 for high-frequency 10-kHz SCS was found to be the ideal area for neuropathic pain of the upper limb/hand and placement at T8–T12 to be best for the lower limb. Also observed, in line with other studies (12,24), was that pain relief developed only after a latent period of some hours. The importance of localizing the site of stimulation without the aid of immediate sensory feedback (paresthesia) from the patient led us to develop a therapy algorithm to maximize pain relief. This algorithm included post-implant x-rays to detect any lead migration and testing at traditional frequencies (50 Hz) for paresthesia location to
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The mean BPI at baseline was 57.56 ± 9.42 for all patients. For nine of 11 patients, the mean BPI at one month was 27 ± 11, and at three months it was 22.4 ± 15.32. For 10 of 11 patients, the mean BPI at six months was 29.4 ± 14.5 (it should be noted that one patient was an outlier at six months with a BPI value of 2). A reduction in the PCS was observed at each follow-up period (from 33 ± 11 at baseline to 7 ± 7, 7 ± 5, and 7 ± 6, respectively). EQ-5D time trade-off score (23) increased by an average of 116% at one month, 124% at three months, and 101% at six months, underscoring an improvement in QOL after implantation of the high-frequency 10-kHz SCS device. With only one exception, all patients rated the therapy with high-frequency 10 kHz SCS as excellent or good and would recommend the procedure to other patients. One patient with good pain relief during the tunneled percutaneous trial developed an infection of the implant site, requiring removal of the leads and planned permanent reimplantation of the High frequency system six months later. Two patients required surgical revision of the system due to lead migration, with one patient regaining earlier pain relief levels following the revision. The other patient, after a fall, failed to respond to programming and both high-frequency and conventional SCS revision. Three patients complained of transient pain at the site of the IPG. No adverse neurologic events related to high-frequency 10-kHz SCS were observed. During the high-frequency 10-kHz SCS phase of the trials, none of the patients perceived paresthesia.
This retrospective case series is the first of its kind to report the use of high-frequency 10-kHz SCS for the treatment of chronic neuropathic limb pain. To date, reports on the same technology have focused primarily on FBSS with or without leg pain. These initial studies show paresthesia-free pain relief with associated improvements in disability and sleep (12,13,24). In our series, highfrequency 10-kHz SCS was effective in reducing neuropathic pain affecting the upper or lower limbs, increasing patients’ quality of life, and reducing patients’ catastrophic thinking related to their pain experience.
AL-KAISY ET AL. help explore optimal stimulation locations for high-frequency 10-kHz SCS therapy. In some cases, pain relief was lost despite no documented lead migration (x-rays and 50-Hz paresthesia testing), but we were able to reachieve the previous pain relief by stimulating at a different vertebral level. Paresthesia Traditional spinal cord stimulation at rates lower than 1.2 kHz requires perceived paresthesia within the area of pain to be clinically effective (6,7,17). As a consequence, traditional SCS analgesia demands achieving optimum paresthesia coverage intraoperatively and maintaining it over time. The intraoperative phase of placing traditional SCS systems can be time-consuming (7) and unpleasant to patients, and the accuracy of stimulation can be affected by sedation. These steps are minimized with experienced operators, but if they can be removed, the whole procedure can be simplified. A further problem with the paresthesia required for efficacy of traditional SCS is that up to 71% of traditional SCS users find stimulation to be uncomfortable at times (8). The discomfort, for instance movement-related dysesthesia, requires many patients to adjust their stimulation level based on posture and may prevent them benefiting from the system at night during sleep or driving. High-frequency 10-kHz SCS has previously been shown to be a paresthesia-free SCS system (12,24), which is corroborated by our retrospective study. Removal of unnecessary intraoperative testing will simplify the whole implantation process. This was seen in patients enrolled in the back pain trial of Van Buyten et al. (12), where the investigators already knew which spinal cord segments were likely to yield positive response to high-frequency 10-kHz SCS. However, when we performed our first high-frequency 10-kHz SCS implantation, there was no information regarding optimal spinal cord levels for the use of this system for neuropathic pain of the upper or lower extremities. Despite the small numbers of patients in this case series, we were able to identify optimal vertebral stimulation levels for both cervical and thoracic high-frequency 10-kHz SCS (spinal cord mapping for high-frequency 10-kHz SCS for neuropathic pain); see Table 2. Also of interest is that when stimulated with appropriate traditional-frequency SCS settings, most of the areas determined to be optimal for high-frequency 10-kHz SCS produce a paresthesia-like sensation that partially overlaps the patients’ painful regions.
CONCLUSION In our case series, high-frequency 10-kHz SCS was shown to be a paresthesia-free and effective option for the treatment of upper and lower limb neuropathic pain. We also believe that our small, retrospective chart review analysis must be corroborated by either prospective randomized controlled studies or large-scale multicenter observational studies in this population of patients with neuropathic pain before it can be concluded that high-frequency 10-kHz SCS is both safe and effective in this population.
Acknowledgements
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Eric Bulogne from Nevro Corporation provided assistance in writing this manuscript. We received editorial support from Dr. Elliot Krames, who is a paid consultant of Nevro Corporation. The patients were all seen at the Pain Management and Neuromodulation Centre, Guy’s and St Thomas’ Hospital, London, UK. www.neuromodulationjournal.com
Authorship Statements All authors contributed to the design, data collection, recruitment, analysis, and writing of the manuscript. All authors have reviewed the final version and consented to publication.
How to Cite this Article: Al-Kaisy A., Palmisani S., Smith T., Harris S., Pang D. 2015. The Use of 10-Kilohertz Spinal Cord Stimulation in a Cohort of Patients With Chronic Neuropathic Limb Pain Refractory to Medical Management. Neuromodulation 2015; 18: 18–23
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10-KHZ SCS FOR CHRONIC NEUROPATHIC LIMB PAIN 24. Tiede J, Brown L, Gekht G, Vallejo R, Yearwood T, Morgan D. Novel spinal cord stimulation parameters in patients with predominant back pain. Neuromodulation 2013;16:370–375. 25. Butt M, Alataris K, Walker A, Tiede J. Histological findings using novel stimulation parameters in a caprine model. Eur J Pain Suppl 2011;5:188–189. 26. Kemler MA, Barendse GA, van Kleef M et al. Spinal cord stimulation in patients with chronic reflex sympathetic dystrophy. N Engl J Med 2000;343:618–624. 27. Pluijms WA, Slangen R, Bakkers M et al. Pain relief and quality-of-life improvement after spinal cord stimulation in painful diabetic polyneuropathy: a pilot study. Br J Anaesth 2012;109:623–629. 28. Kumar K, Taylor RS, Jacques L et al. Spinal cord stimulation versus conventional medical management for neuropathic pain: a multicentre randomised controlled trial in patients with failed back surgery syndrome. Pain 2007;132:179– 188.
COMMENT The authors of this paper present and important, albeit very preliminary, small and short-term, experience with high frequency spinal cord stimulation (HF SCS) in treatment of pain in extremities. Currently, HF SCS is considered primarily for lower back pain—and the main reason for this indication has been low efficacy of conventional SCS and other approaches. For pain in extremities, on the other hand, conventional
SCS does work, and I am somewhat skeptical, in absence of prospective comparative study, about moving to paresthesia-free stimulation for extremity pain syndromes. Moreover, the authors’ approach in using conventional stimulation to define optimal location or HF SCS electrodes contradicts all previous research that postulated existence of alternative pathways and targets that produce pain relief without paresthesias. Nevertheless, I feel that the testing approach described here may be tried even for low back pain in order to define better contact location and better long-term responders. Perhaps with better understanding of correlation between two approaches to stimulation (paresthesia-based and paresthesia-free) we will be able to determine better indications for each. It is also possible that a combination of different paradigms will be more effective for particularly complex patients and pain patterns. Konstantin V. Slavin, MD Chicago, IL, USA
Comments not included in the Early View version of this paper.
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