A Comprehensive Outcome-Specific Review of the Use of Spinal Cord Stimulation for Complex Regional Pain Syndrome

A brief review of complex regional pain syndrome and current management

Complex regional pain syndrome (CRPS) is a debilitating chronic pain condition that, although exceedingly rare, carries a significant burden for the affected patient population. The complex and ambiguous pathophysiology of this condition further complicates clinical management and therapeutic interventions. Furthermore, being a diagnosis of exclusion requires a diligent workup to ensure an accurate diagnosis and subsequent targeted management. The development of the Budapest diagnostic criteria helped to consolidate existing definitions of CRPS but extensive work remains in identifying the underlying pathways. Currently, two distinct types are identified by the presence (CRPS type 1) or absence (CRPS type 2) of neuronal injury. Current management directed at this disease is broad and growing, ranging from non-invasive modalities such as physical and psychological therapy to more invasive techniques such as dorsal root ganglion stimulation and potentially amputation. Ideal therapeutic interventions are multimodal in nature to address the likely multifactorial pathological development of CRPS. Regardless, a significant need remains for continued studies to elucidate the pathways involved in developing CRPS as well as more robust clinical trials for various treatment modalities.

Does Spinal Cord Stimulation Improve Sleep Disturbances Independently of Pain Relief in Patients With Chronic Pain? An Explorative, Observational Study

OBJECTIVES

Chronic pain poses a significant health challenge worldwide and is associated with both disability and reduced quality of life. Sleep disturbances are reported in 67% to 88% of patients with chronic pain. Pain and sleep affect each other reciprocally; we aimed to study this bidirectional relationship in patients treated with spinal cord stimulation (SCS) for chronic pain. Specifically, we investigated whether sleep improves after treatment with SCS and whether this improvement may be mediated by pain reduction.

MATERIALS AND METHODS

An observational cohort study was conducted in patients with chronic neuropathic pain treated with SCS at a single neurosurgical department in Denmark. Outcomes were assessed preoperatively and at three, six, and 12 months postoperatively, and thereafter annually. Primary outcomes were pain intensity (numeric rating scale) and insomnia at first follow-up (Insomnia Severity Index). The association between sleep and pain was investigated using linear regression and mediation analysis.

RESULTS

Forty-three patients were included in the study. The mean insomnia score was reduced by 25% from 18.1 (SD 6.0) to 13.5 (SD 6.6) (p = 0.0001). Pain intensity was reduced 38% from 7.4 (SD 1.6) to 4.6 (SD 2.1) at the first follow-up (p ≤ 0.0001). Changes in pain and changes in insomnia scores were significantly but weakly associated (regression coefficient = 1.3, 95% CI [0.3; 2.2], p = 0.008, r2 = 15.7%); and changes in pain score were not found to mediate changes in sleep score (β = -0.02, 95% CI [-0.15; 0.11], p = 0.76).

CONCLUSIONS

We found that patients treated with SCS showed significant improvements in both insomnia and pain intensity at first follow-up. Improvements in insomnia and pain intensity were significantly but weakly associated, and improvements in pain intensity score did not mediate improvements in insomnia score. Thus, improvements in self-reported insomnia in patients treated with SCS for chronic pain may predominantly be caused by other factors than reduced pain intensity.

Improvement in Health-Related Quality of Life With Spinal Cord Stimulation in Complex Regional Pain Syndrome: A Single-Center, Retrospective Study

BACKGROUND

Complex regional pain syndrome (CRPS) can profoundly affect many aspects of everyday life. Spinal cord stimulation (SCS) is a potential therapeutic option. This retrospective, single-site evaluation explored health-related quality of life (HRQoL) in individuals with CRPS treated with SCS in our Pain Service.

MATERIALS AND METHODS

All patients aged ≥18 years with fully implanted SCS for CRPS between June 2013 and January 2023 were identified from hospital records. The following data were collected: sex, age, chronic pain diagnosis, CRPS type (I or II), location of CRPS (upper or lower limb), years of CRPS before first SCS implant, SCS system, preimplant and follow-up scores for HRQoL (euroqol 5 dimensions 3 levels [EQ-5D-3L] index score), average pain, worst pain and the influence of pain on aspects of everyday life (all numerical rating scale [NRS]), patient and clinician global impression of change at follow-up, and the occurrence and reasons for revisions and explants. An intention-to-treat approach was used and data statistically analyzed.

RESULTS

The final cohort comprised 83 patients (46 women), with a median (minimum, maximum) follow-up duration of 29 months (seven, 72). There were statistically and clinically significant improvements in HRQoL, despite relatively low pain response rates. The pain response rate was 34% (reduction of ≥30% in average pain NRS); the pain remission rate was 13% (average pain score ≤3 NRS), and all patients had preimplant EQ-5D-3L index values below the population norm of 0.82. However, 60% of patients reported EQ-5D-3L index scores greater than the published minimally important difference of 0.074, and scores were better at follow-up than at preimplant (p < 0.001); 44% of patients and 41% of clinicians reported improved symptoms at the most recent follow-up. Explants occurred in eight of 83 patients (10%).

CONCLUSIONS

Patients had meaningful improvements in HRQoL, which is a key outcome in ascertaining the overall outcome of SCS in CRPS. Randomized controlled clinical trials should build on the findings to improve understanding of the benefits and risks of treating CRPS with SCS.

Ventral Column Spinal Cord Stimulation for Postlumbar Laminectomy Syndrome

ABSTRACT

Spinal cord stimulation is an increasingly used treatment for a number of chronic pain states. Dorsal column stimulation is historically and currently the anatomical target of choice for most chronic pain conditions, including postlaminectomy syndrome and radicular pain. However, early studies suggested that stimulation of an alternative target, the ventral columns that carry pain fibers in the anterior and lateral spinothalamic tracts, may offer comparable or superior pain relief. A patient undergoing standard-of-care spinal cord stimulation trial had an additional lead placed on the right ventrolateral aspect of the spinal cord. After the usual 7-day trial of dorsal column stimulation, the dorsal leads were removed and ventrolateral column stimulation was applied through the retained ventral lead for a period of 3 days. The Brief Pain Index Short Form and Numeric Rating Scale were recorded for both dorsal and ventral stimulation. Ventrolateral spinal cord stimulation provided comparable outcomes compared with dorsal column stimulation using nonparesthesia-based stimulation. The results suggest further investigation into spinal cord stimulation anatomical placement and mechanism of action is warranted.

Biplane fluoroscopy-guided percutaneous spinal cord stimulation

OBJECTIVE

Fluoroscopy is useful for spinal cord stimulation (SCS) lead placement. We employed biplane fluoroscopy for SCS lead placement. In this study, we sought to confirm the validity of using biplane fluoroscopy for SCS lead placement and to establish whether biplane fluoroscopy safely reduces the duration of surgery.

METHODS

Clinical data were retrospectively collected from the medical records of patients who underwent SCS lead placement under local anesthesia from 2015 to 2022. The duration of the surgical phase and the total radiation exposure time per case were recorded.

RESULTS

Forty-six patients underwent percutaneous SCS lead implantation. Recording was completed in 41 cases: one lead was placed in 13 cases and two leads were placed in 28 cases. Monoplane and biplane fluoroscopy was used in 15 and 26 patients, respectively. Although the type of fluoroscopy did not significantly affect the mean duration of the surgical phase in patients in which one lead was placed, biplane fluoroscopy was associated with a significant reduction in the mean duration of the surgical phase in patients that underwent placement of two leads (P=0.002). No significant differences in the total radiation exposure time were observed between patients in the monoplane and biplane fluoroscopy groups that were implanted with one (P=0.21) or two leads (P=0.62).

CONCLUSIONS

The use of biplane fluoroscopy reduced the duration of surgery necessary for the placement of two SCS leads. Biplane fluoroscopy represents a practical and safe adjustment to the current practice of SCS lead implantation.

Long-term analgesic effect of trans-spinal direct current stimulation compared to non-invasive motor cortex stimulation in complex regional pain syndrome

The aim of the present study was to compare the analgesic effect of motor cortex stimulation using high-frequency repetitive transcranial magnetic stimulation or transcranial direct current stimulation and transcutaneous spinal direct current stimulation in patients with complex regional pain syndrome. Thirty-three patients with complex regional pain syndrome were randomized to one of the three treatment groups (repetitive transcranial magnetic stimulation, n = 11; transcranial direct current stimulation, n = 10; transcutaneous spinal direct current stimulation, n = 12) and received a series of 12 sessions of stimulation for 3 weeks (induction phase) and 11 sessions for 4 months (maintenance therapy). The primary end-point was the mean pain intensity assessed weekly with a visual numerical scale during the month prior to treatment (baseline), the 5-month stimulation period and 1 month after the treatment. The weekly visual numerical scale pain score was significantly reduced at all time points compared to baseline in the transcutaneous spinal direct current stimulation group, at the last two time points in the repetitive transcranial magnetic stimulation group (end of the 5-month stimulation period and 1 month later), but at no time point in the transcranial direct current stimulation group. A significant pain relief was observed at the end of induction phase using transcutaneous spinal direct current stimulation compared to repetitive transcranial magnetic stimulation (P = 0.008) and to transcranial direct current stimulation (P = 0.003). In this trial, transcutaneous spinal direct current stimulation was more efficient to relieve pain in patients with complex regional pain syndrome compared to motor cortex stimulation techniques (repetitive transcranial magnetic stimulation, transcranial direct current stimulation). This efficacy was found during the induction phase and was maintained thereafter. This study warrants further investigation to confirm the potentiality of transcutaneous spinal direct current stimulation as a therapeutic option in complex regional pain syndrome.

Interventions for treating pain and disability in adults with complex regional pain syndrome- an overview of systematic reviews

BACKGROUND

Complex regional pain syndrome (CRPS) is a chronic pain condition that usually occurs in a limb following trauma or surgery. It is characterised by persisting pain that is disproportionate in magnitude or duration to the typical course of pain after similar injury. There is currently no consensus regarding the optimal management of CRPS, although a broad range of interventions have been described and are commonly used. This is the first update of the original Cochrane review published in Issue 4, 2013.

OBJECTIVES

To summarise the evidence from Cochrane and non-Cochrane systematic reviews of the efficacy, effectiveness, and safety of any intervention used to reduce pain, disability, or both, in adults with CRPS.

METHODS

We identified Cochrane reviews and non-Cochrane reviews through a systematic search of Ovid MEDLINE, Ovid Embase, Cochrane Database of Systematic Reviews, CINAHL, PEDro, LILACS and Epistemonikos from inception to October 2022, with no language restrictions. We included systematic reviews of randomised controlled trials that included adults (≥18 years) diagnosed with CRPS, using any diagnostic criteria.  Two overview authors independently assessed eligibility, extracted data, and assessed the quality of the reviews and certainty of the evidence using the AMSTAR 2 and GRADE tools respectively. We extracted data for the primary outcomes pain, disability and adverse events, and the secondary outcomes quality of life, emotional well-being, and participants' ratings of satisfaction or improvement with treatment.  MAIN RESULTS: We included six Cochrane and 13 non-Cochrane systematic reviews in the previous version of this overview and five Cochrane and 12 non-Cochrane reviews in the current version. Using the AMSTAR 2 tool, we judged Cochrane reviews to have higher methodological quality than non-Cochrane reviews. The studies in the included reviews were typically small and mostly at high risk of bias or of low methodological quality. We found no high-certainty evidence for any comparison.  There was low-certainty evidence that bisphosphonates may reduce pain intensity post-intervention (standardised mean difference (SMD) -2.6, 95% confidence interval (CI) -1.8 to -3.4, P = 0.001; I2 = 81%; 4 trials, n = 181) and moderate-certainty evidence that they are probably associated with increased adverse events of any nature (risk ratio (RR) 2.10, 95% CI 1.27 to 3.47; number needed to treat for an additional harmful outcome (NNTH) 4.6, 95% CI 2.4 to 168.0; 4 trials, n = 181).  There was moderate-certainty evidence that lidocaine local anaesthetic sympathetic blockade probably does not reduce pain intensity compared with placebo, and low-certainty evidence that it may not reduce pain intensity compared with ultrasound of the stellate ganglion. No effect size was reported for either comparison. There was low-certainty evidence that topical dimethyl sulfoxide may not reduce pain intensity compared with oral N-acetylcysteine, but no effect size was reported. There was low-certainty evidence that continuous bupivacaine brachial plexus block may reduce pain intensity compared with continuous bupivacaine stellate ganglion block, but no effect size was reported. For a wide range of other commonly used interventions, the certainty in the evidence was very low and provides insufficient evidence to either support or refute their use. Comparisons with low- and very low-certainty evidence should be treated with substantial caution. We did not identify any RCT evidence for routinely used pharmacological interventions for CRPS such as tricyclic antidepressants or opioids.

AUTHORS' CONCLUSIONS

Despite a considerable increase in included evidence compared with the previous version of this overview, we identified no high-certainty evidence for the effectiveness of any therapy for CRPS. Until larger, high-quality trials are undertaken, formulating an evidence-based approach to managing CRPS will remain difficult. Current non-Cochrane systematic reviews of interventions for CRPS are of low methodological quality and should not be relied upon to provide an accurate and comprehensive summary of the evidence.

Identification of Potential Inflammation-Related Genes and Key Pathways Associated with Complex Regional Pain Syndrome

Complex regional pain syndrome (CRPS) is a chronic pain that affects the extremities after a trauma or nerve injury with no definite established treatment. The mechanisms mediating CRPS are not completely elucidated. Thus, we conducted a bioinformatics analysis to identify hub genes and key pathways to determine strategies for more effective treatments of CRPS. Finally, there is only one expression profile of GSE47063 in terms of homo sapiens-based CRPS from the Gene Expression Omnibus (GEO) database, which included four patients and five controls. We explored the differentially expressed genes (DEGs) in the dataset and conducted Gene Ontology (GO) functional and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of the potential hub genes. A protein-protein interaction (PPI) network was also established; then, according to the score of each hub genes, we used R software to draw the nomogram model to predict the rate of CRPS. Furthermore, GSEA analysis was estimated and assessed by the normalized enrichment score (NES). From the GO and KEGG analysis, we identified the top five hub genes (MMP9, PTGS2, CXCL8, OSM, TLN1); all of the selected DEGs were mainly enriched in their inflammatory response. In addition, the GSEA analysis showed complement and coagulation cascades also play an important role in CRPS. This study, to our knowledge, is the first to conduct further PPI network and GSEA analyses. Thus, targeting excessive inflammation could offer new therapeutic methods for CRPS and related physical and psychiatric disorders.

Role of patient selection and trial stimulation for spinal cord stimulation therapy for chronic non-cancer pain: a comprehensive narrative review

Background/importance

Patient selection for spinal cord stimulation (SCS) therapy is crucial and is traditionally performed with clinical selection followed by a screening trial. The factors influencing patient selection and the importance of trialing have not been systematically evaluated.

Objective

We report a narrative review conducted to synthesize evidence regarding patient selection and the role of SCS trials.

Evidence review

Medline, EMBASE and Cochrane databases were searched for reports (any design) of SCS in adult patients, from their inception until March 30, 2022. Study selection and data extraction were carried out using DistillerSR. Data were organized into tables and narrative summaries, categorized by study design. Importance of patient variables and trialing was considered by looking at their influence on the long-term therapy success.

Findings

Among 7321 citations, 201 reports consisting of 60 systematic reviews, 36 randomized controlled trials (RCTs), 41 observational studies (OSs), 51 registry-based reports, and 13 case reports on complications during trialing were included. Based on RCTs and OSs, the median trial success rate was 72% and 82%, and therapy success was 65% and 61% at 12 months, respectively. Although several psychological and non-psychological determinants have been investigated, studies do not report a consistent approach to patient selection. Among psychological factors, untreated depression was associated with poor long-term outcomes, but the effect of others was inconsistent. Most RCTs except for chronic angina involved trialing and only one RCT compared patient selection with or without trial. The median (range) trial duration was 10 (0–30) and 7 (0–56) days among RCTs and OSs, respectively.

Conclusions

Due to lack of a consistent approach to identify responders for SCS therapy, trialing complements patient selection to exclude patients who do not find the therapy helpful and/or intolerant of the SCS system. However, more rigorous and large studies are necessary to better evaluate its role.

Short- and long-term effects of conventional spinal cord stimulation on chronic pain and health perceptions: A longitudinal controlled trial

BACKGROUND

The effectiveness and long-term outcomes of spinal cord stimulation (SCS) are not fully established, especially considering that data from patients who withdrew from the trial are rarely analysed, which may lead to overestimation of SCS efficacy. We evaluated short- and long-term effects of SCS on chronic pain and perceived health, beyond natural variability in these outcomes.

METHODS

In a prospective design, 176 chronic pain patients referred to SCS were evaluated five times (baseline; retest ~6 weeks later; post-SCS trial; 8 and 28 weeks post-permanent implantation). Patients whose SCS trial failed (Temp group) were followed up and compared to those who underwent permanent SCS (Perm group).

RESULTS

Analyses revealed a non-linear (U-shaped) trend significantly different between the two groups. In the Perm group, a significant improvement occurred post-SCS implantation in pain severity, pain interference, health-related quality of life and self-rated health, which was followed by gradual worsening and return to baseline values at end of follow-up. In the Temp group, only minor changes occurred in these outcomes over time. On average, baseline and end of follow-up values in the Perm and Temp groups were similar: ~40% in each group exhibited an increase in pain severity over time and 38% and 33%, respectively, exhibited reductions in pain severity over time.

CONCLUSIONS

Since the greatest improvement in the outcome measures occurred from baseline to post-SCS trial (T1-T3) followed by a gradual decline in the effect, it appears that SCS may not be effective for the majority of chronic pain patients.

SIGNIFICANCE

This longitudinal study evaluated short and long term effects of spinal cord stimulation (SCS) on chronic pain outcome measures, beyond their natural variation in time. Despite significant short term improvements, by the end of the seven months' follow-up, the outcomes in the treatment group (people who received the permanent implantation) were similar to those of the control group (people whose SCS trial failed and did not continue to permanent implantation) suggesting SCS may not be cost-effective for chronic pain patients.

Neuromodulation for Management of Chronic Pelvic Pain: A Comprehensive Review

INTRODUCTION

Chronic pelvic pain (CPP) is a symptom that derives from a complex group of heterogeneous pathologies of the pelvic organs. The aim of this study was to review the available evidence on efficacy of neuromodulatory modalities including sacral neuromodulation, dorsal root ganglion stimulation, dorsal column neuromodulation, and pudendal nerve stimulation.

METHODS

This narrative review focuses on updated information on neuromodulation for management of chronic pelvic pain. In 2022, we searched English-language studies on neuromodulation, pelvic pain, and chronic pain in a comprehensive search. We searched the following databases: PubMed, Medline, SciHub, Cochrane Database of Systematic Reviews, and Google Scholar. We used the following combinations of keywords: neuromodulation, pelvic pain, chronic pain, chronic pelvic pain, pelvic pain treatment. We tried to include as many recent manuscripts as possible (within the last 3 years) but also included papers older than 3 years if they were particularly relevant to our topic. We also attempted to search for, use, and cite primary manuscripts whenever possible.

RESULTS

CPP is a challenging entity to treat because of diagnostic inconsistencies and limited evidence for therapeutic modalities. Our review found evidence suggestive of benefit for all modalities reviewed but the data was of overall low quality with numerous limitations. The literature highlights a lack of randomized controlled trials for neuromodulatory therapies but suggests a growing role for such techniques in treating refractory chronic pelvic pain syndrome (CPPS).

CONCLUSIONS

This review explores the available evidence on efficacy of neuromodulatory modalities for CPPS and contextualizes the results with information about the type of neuromodulation, lead location and waveform, pain outcomes and assessment timepoints, and reported adverse effects.

Spinal cord stimulation: Beyond pain management

INTRODUCTION

The gate control theory of pain was the starting point of the development of spinal cord stimulation (SCS). We describe the indications for the treatment in pain management and other uses not related to pain.

DEVELOPMENT

There are currently several paradigms for SCS: tonic, burst, and high frequency. The main difference lies in the presence of paraesthesias. SCS is most beneficial for treating neuropathic pain. Patients with failed back surgery syndrome show the best response rates, although a considerable reduction in pain is also observed in patients with complex regional pain syndrome, diabetic neuropathy, radiculopathy, and low back pain without previous surgery. Phantom pain or pain related to cardiovascular or peripheral vascular disease may improve, although there is a lack of robust evidence supporting generalisation of its use. SCS also improves cancer-related pain, although research on this issue is scarce. Non-pain-related indications for SCS are movement disorders, spasticity, and sequelae of spinal cord injury. The main limiting factors for the use of SCS are mechanical complications and the cost of the treatment.

CONCLUSION

In its 50-year history, SCS has progressed enormously. The perfection of hardware and software may improve its effectiveness and reduce the rate of complications. Indications for SCS could include other diseases, and its use could be expanded, if the costs of the technology are reduced.

Efficacy of 10 kHz spinal cord stimulation in complex regional pain syndrome: A retrospective analysis

INTRODUCTION

We examine the clinical efficacy of High Frequency 10 kHz (HF10) spinal cord stimulation (SCS) CRPS patients.

MATERIALS AND METHODS

This is a retrospective cohort study of SCS-naïve patients with CRPS treated with HF10-SCS after a successful trial. Patients were evaluated at 2 weeks, 6 weeks, 3 months, and 6 months post-operatively. Outcomes included mean numeric pain rating scale (NRS), mean NRS reduction, NRS percentage improvement (PI), patient reported subjective pain PI (Pain PI), and patients reporting > 50% benefit in symptoms. Pre and post-operative NRS were compared by ordinal regression analysis accounting for the patient's response to the SCS trial.

RESULTS

20 patients met inclusion criteria. 75% were female. Mean age 51 years. Baseline mean NRS was 6.1 for the cohort (1.7). Post-operatively, mean NRS decreased to 4.5 at 2 weeks (p = 0.077), 3.8 at 6 weeks (p = 0.034), 3.7 at 3 months (p = 0.307), and 4.4 at 6 months (p = 0.832). Mean NRS reduction and NRS PI is reported within. Pain PI was 25% at 2 weeks, 55% at 6 weeks, 54% at 3 months, and 53% at 6 months. Greater than 50% reduction in symptoms was reported in 25% of patients at 2 weeks, 85% at 6 weeks, 87% at 3 months, and 64% at 6 months.

CONCLUSIONS

HF10 SCS may represent an effective treatment option for reducing objective and subjective symptoms in CRPS that warrants further study.

Spinal Cord Stimulation as an Alternative to Opioid for Axial Neck and Back Pain: A Case Series

Introduction

Spinal cord stimulation is emerging as a minimally invasive technique for treatment of persistent spinal pain syndrome (PSPS).

Methods

We describe a case series of 25 individuals with PSPS who underwent implantation of a spinal cord stimulator device between 2017 and 2021.

Results

There was a significant reduction in mean visual analog scale pain scores in the immediate postoperative phase, (8.61 vs. 2.3, p &lt; 0.001). There were twelve patients who consumed pre-operative opioid, and 75% showed reduction of use with a significantly lower average daily dose (66.8 vs. 26.9 meq/D, p &lt; 0.05). There was a significant reduction in the Oswestry Disability Index during postoperative follow-up visits (p &lt; 0.001). There were no major perioperative or long-term complications from the procedure in follow-up.

Conclusion

The analysis of this cohort suggests successful long-term treatment of a diverse set of patients with PSPS who underwent spinal cord stimulation (SCS) and had meaningful improvement in quality of life and reduction in opioid consumption.

Senso-Immunologic Prospects for Complex Regional Pain Syndrome Treatment

Complex regional pain syndrome (CRPS) is a chronic pain syndrome that occurs in tissue injuries as the result of surgery, trauma, or ischemia. The clinical features of this severely painful condition include redness and swelling of the affected skin. Intriguingly, it was recently suggested that transient receptor potential ankyrin 1 (TRPA1) is involved in chronic post-ischemia pain, a CRPS model. TRPA1 is a non-selective cation channel expressed in calcitonin gene-related peptide (CGRP)-positive primary nociceptors that becomes highly activated in ischemic conditions, leading to the generation of pain. In this review, we summarize the history of TRPA1 and its involvement in pain sensation, inflammation, and CRPS. Furthermore, bone atrophy is also thought to be a characteristic clinical sign of CRPS. The altered bone microstructure of CRPS patients is thought to be caused by aggravated bone resorption via enhanced osteoclast differentiation and activation. Although TRPA1 could be a target for pain treatment in CRPS patients, we also discuss the paradoxical situation in this review. Nociceptor activation decreases the risk of bone destruction via CGRP secretion from free nerve endings. Thus, TRPA1 inhibition could cause severe bone atrophy. However, the suitable therapeutic strategy is controversial because the pathologic mechanisms of bone atrophy in CRPS are unclear. Therefore, we propose focusing on the remission of abnormal bone turnover observed in CRPS using a recently developed concept: senso-immunology.

High frequency dorsal column spinal cord stimulation for management of erythromelalgia

Erythromelalgia is a rare hereditary channelopathy affecting the Nav1.7 sodium channel. Patients afflicted with this condition suffer from pain in their hands and feet, with vasomotor changes including flushing and redness to the distal upper and lower extremities. Current treatment modalities for this condition include pharmacological therapies (neuropathic medications), behavioural interventions, lumbar epidural infusions with local anaesthetics and sympathetic nerve blocks. Despite these treatments, many patients may have refractory pain. In these situations, there may be a role for dorsal column spinal cord stimulation for management of their pain. Here, we present the case of a 21-year-old man with 9-year history of refractory erythromelalgia successfully treated with paresthesia-free dorsal column spinal cord stimulation.

Spinal cord stimulation in severe cases of complex regional pain syndrome: A retrospective cohort study with long-term follow-up

BACKGROUND

Complex regional pain syndrome (CRPS) is a debilitating pain condition often resistant to standard treatment modalities. In these cases, spinal cord stimulation (SCS) can be an option, but the effect on CRPS remains disputed. We aimed to assess the long-term effect of SCS on CRPS.

METHODS

We retrospectively analysed 51 CRPS patients implanted with an SCS system at the University Hospitals in Aarhus or Odense, Denmark, with a median follow-up time of 4.4 years. Primary outcomes were pain intensity on a numeric rating scale (NRS) and the Patients' Global Impression of Change (PGIC). Secondary outcomes were patient satisfaction, work status, consumption of pain medication, the Major Depression Inventory (MDI), Pain Catastrophizing Scale (PCS) and quality of life (QoL) measured using the Short-Form Health Survey (SF-36). For each outcome measure, baseline data were compared to the latest collected data point.

RESULTS

A significant pain relief was found with a mean reduction in NRS score of 2.4 (95% CI: 1.7-3.0, p < 0.0001). 68.8% reported 'much improved' or 'very much improved' on the PGIC scale. 87.5% would choose SCS again for the same outcome. A significant beneficial impact was found on MDI score, PCS, SF-36 summary scores and consumption of tricyclic antidepressants, antiepileptic drugs and opioids. No statistical effect was found on work status.

CONCLUSION

Pain intensity, depression, pain catastrophizing, pain medication use and QoL were significantly improved after SCS implantation, with high patient satisfaction rates in CRPS patients. This study supports the continued use of SCS in the treatment of severe CRPS.

SIGNIFICANCE

This study presents detailed data from a large, well-characterized cohort of Danish CRPS patients treated with SCS, analyzing several outcome measures. The results serve to document SCS as an effective treatment for severe CRPS and expands the cumulative level of evidence in favor of its use. Additionally, analysis of preoperative patient characteristics suggests that SCS treatment should not be withheld in patients with a high degree of psychological distress or high consumption of analgesics.

Interventional Modalities to Treat Complex Regional Pain Syndrome

PURPOSE OF REVIEW

Complex regional pain syndrome (CRPS) is a debilitating pain condition that often requires a multidisciplinary approach including medication, physical therapy, occupational therapy, psychological therapy, and interventional procedures to restore the patient's quality of life. This article reviews the interventional treatments for pain resulting from CRPS.

RECENT FINDINGS

Sympathetic nerve blocks (stellate ganglion and lumbar sympathetic) are the first-line interventional treatment options for patients with CRPS of the upper and lower extremities, respectively. Fluoroscopic techniques for lumbar sympathetic blocks have not significantly changed throughout the years. However, both novel fluoroscopic and ultrasound approaches to stellate ganglion blockade have arisen. In addition, novel neuromodulation therapies to treat CRPS have been developed to include new waveforms with dorsal column stimulation and entirely new nerve targets such as dorsal root ganglion stimulation. This paper will review the latest interventional treatment options available for the treatment of CRPS.

Poststroke Pain

Pain is common but often underrecognized after stroke. Poststroke pain (PSP) hinders recovery, impairs quality of life, and is associated with the psychological state of patients with stroke. The most common subtypes of PSP include central PSP, complex regional pain syndrome, shoulder pain, spasticity-related pain, and headache. The pathophysiologies of these PSP subtypes are not yet clearly understood, and PSP is refractory to conventional treatment in many patients. However, recent studies have proposed potential pathophysiologies of PSP subtypes, which may help prioritize therapies that target specific mechanisms.

Complex regional pain syndrome - Autoimmune or functional neurologic syndrome

Complex regional pain syndrome (CRPS) purports to explain extremity pain accompanied by a variety of subjective complaints, including sensitivity to touch, fatigue, burning sensations, allodynia and signs consistent with voluntary immobilization, including skin changes, edema and trophic changes. By its own definition, CRPS pain is disproportionate to any inciting event or underlying pathology, which means that the syndrome describes non-anatomic and exaggerated symptoms. Although CRPS was coined in the early 1990s, physicians have described unexplained exaggerated pain for centuries. Before a small group of researchers assigned this historical phenomenon with the name CRPS, other physicians in various subspecialties investigated the existence of a common pathophysiologic mechanism but found none. The literature was searched for evidence of a reproducible pathologic mechanism for CRPS. Although some have suggested that CRPS is an autoimmune disease, there is a paucity of evidence to support this. While cytokines such as IL-1β, IL-6 and TNF-α have been detected during the early phases of CRPS, this cannot lead to the conclusion that CRPS is an autoimmune disease, nor that it is an autoinflammatory disorder. Moreover, intravenous immunoglobulin has showed inconsistent results in the treatment of CRPS. On the other hand, CRPS has been found to meet at least three out of four criteria of malingering, which was previously a DSM-IV diagnosis; and its diagnostic criteria are virtually identical to current DSM-5 Functional Neurological Disorder ("FND"), and proposed ICD-11 classification, which includes FND as a distinct neurological diagnosis apart from any psychiatric condition. Unfortunately, the creation of CPRS is not merely misguided brand marketing. It has serious social and health issues. At least in part, the existence of CRPS has led to the labeling of many patients with a diagnosis that allows the inappropriate use of invasive surgery, addictive opioids, and ketamine. The CRPS hypothesis also ignores the nature and purpose of pain, as a symptom of some organic or psychological process. Physicians have long encountered patients who voice symptoms that cannot be biologically explained. Terminology historically used to describe this phenomenon have been medically unexplained symptoms ("MUS"), hysterical, somatic, non-organic, psychogenic, conversion disorder, or dissociative symptoms. The more recent trend describes disorders where there is a functional, rather than structural cause of the symptoms, as "functional disorders." Physicians report high success treating functional neurological symptoms with reassurance, physiotherapy, and cognitive behavior therapy measured in terms of functional improvement. The CRPS label, however, neither leads to functional improvement in these patients nor resolution of symptoms. Under principles of evidence-based medicine, the CRPS label should be abandoned and the syndrome should simply be considered a subset of FNDs, specifically Functional Pain Disorder; and treated appropriately.

Complex regional pain syndrome: An updated comprehensive review

Complex regional pain syndrome (CRPS) is a complex disorder that can have a significant impact on the quality of life of a person with this syndrome. The diagnosis and treatment of CRPS are often difficult as there is no one confirmatory test and no one definitive treatment. Currently, the most widely accepted clinical diagnostic criteria are the Budapest criteria, which were developed by expert consensus. Though no one single treatment has been found to be universally effective, early detection and an interdisciplinary approach to treatment appear to be key in treating CRPS. This review aims to present up-to-date clinical information regarding the diagnosis and management of CRPS and highlight the potential issues with diagnosis in the neurological population. Ultimately, more research is needed to identify the exact etiology of CRPS in order to help target appropriate therapies. In addition, more randomized controlled trials need to be performed in order to test new therapies or combinations of therapies, including pharmacological, interventional, and behavioral therapies, to determine the best treatment options for this potentially debilitating disorder.

Multiple Limb Involvement in a Severe Case of Complex Regional Pain Syndrome Treated With Spinal Cord Stimulation: A Case Report

Complex regional pain syndrome (CRPS) can be a debilitating, persistent, and treatment-resistant pain condition. This report presents a case of severe CRPS affecting multiple limbs, resistant to standard treatment modalities. Treatment with spinal cord stimulation (SCS) had an initial good effect. Nevertheless, the CRPS continued to progress, eventually affecting all 4 extremities. A lead fracture resulted in a rapidly developing recurrence of CRPS in the patient's arm, necessitating amputation. SCS may be an effective modality for treatment of severe CRPS. However, mechanical problems should always be considered when an SCS-implanted patient experiences rapid symptom progression or abrupt cessation of stimulation.

Active Recharge Burst and Tonic Spinal Cord Stimulation Engage Different Supraspinal Mechanisms: A Functional Magnetic Resonance Imaging Study in Peripherally Injured Chronic Neuropathic Rats

OBJECTIVES

To assess the supraspinal working mechanisms of the burst spinal cord stimulation (SCS) mode, we used functional magnetic resonance imaging (fMRI) in chronic neuropathic rats. We hypothesized that active recharge burst SCS would induce a more profound blood oxygenation level-dependent (BOLD) signal increase in areas associated with cognitive-emotional aspects of pain, as compared to tonic SCS.

METHODS

Sprague Dawley rats (n = 17) underwent a unilateral partial sciatic nerve ligation, which resulted in chronic neuropathic pain. Quadripolar SCS electrodes were epidurally positioned on top of the dorsal columns at Th13. Isoflurane-anesthetized (1.5%) rats received either tonic SCS (n = 8) or burst SCS (n = 9) at 66% of motor threshold. BOLD fMRI was conducted before, during, and after SCS using a 9.4-T horizontal bore scanner.

RESULTS

Overall, both tonic and burst SCS induced a significant increase of BOLD signal levels in areas associated with the location and intensity of pain, and areas associated with cognitive-emotional aspects of pain. Additionally, burst SCS significantly increased BOLD signal levels in the raphe nuclei, nucleus accumbens, and caudate putamen. Tonic SCS did not induce a significant increase in BOLD signal levels in these areas.

CONCLUSIONS

In conclusion, active recharge burst and tonic SCS have different effects on the intensity and localization of SCS-induced activation responses in the brain. This work demonstrates that active recharge burst is another waveform that can engage brain areas associated with cognitive-emotional aspects of pain as well as areas associated with location and intensity of pain. Previous studies showing similar engagement used only passive recharge burst.

Utilization of Concurrent Dorsal Root Ganglion Stimulation and Dorsal Column Spinal Cord Stimulation in Complex Regional Pain Syndrome

INTRODUCTION

Complex regional pain syndrome (CRPS) can be effectively treated with spinal cord stimulation (t-SCS). There is also evidence that dorsal root ganglion (DRG) stimulation may be superior to t-SCS in CRPS. However, there has been no published data, to our knowledge, that looked at the concurrent use of t-SCS and DRG stimulation for treatment of CRPS.

METHODS

Our study includes four patients with severe CRPS who had all been implanted with a t-SCS. While all these patients had positive results from their t-SCS, they all had areas which lacked coverage, giving them incomplete pain relief. These patients also underwent successful trial and implantation of DRG-S. All four patients reported further improvement in their residual pain and function with DRG-S (>60%), and even superior pain relief (>80%) with concurrent use of t-SCS and t-SCS.

RESULTS

All patients had a diagnosis of lower extremity CRPS-1. After DRG-S implantation, multiple attempts were made in each patient to use DRG-S alone by temporarily turning the t-SCS off. However, in each attempt, all patients consistently reported superior pain relief and improvement in function with the concurrent use of t-SCS and DRG, as compared to DRG alone. The average numeric rating scale pain score decreased from approximately 7 in the regions not covered by t-SCS to 3 after DRG-S implantation, and to 1.25 with concurrent use t-SCS and DRG-S.

CONCLUSION

Both t-SCS and DRG-S have been shown to be effective in treatment of patients with CRPS. In our study, concurrent use of t-SCS and DRG-S provided significant improvement in pain and function as compared to using either device alone. This suggests the potential that combination therapy with t-SCS and DRG-S may be beneficial in patients with CRPS. Further prospective studies are required to evaluate this concept.

Perioperative Outcomes of Spinal Cord Stimulator Placement in Patients with Complex Regional Pain Syndrome Compared with Patients without Complex Regional Pain Syndrome

BACKGROUND AND OBJECTIVE

Complex regional pain syndrome (CRPS) is a multifaceted disorder resulting in an abnormal pain response to tissue injury. Among key CRPS features are neurogenic inflammation, maladaptive plasticity, and vasomotor dysfunction, which can result in severe pain and disability. Spinal cord stimulation (SCS) is an efficacious treatment for several chronic pain conditions and may improve pain and life quality in CRPS patients with CRPS. However, little information exists regarding perioperative outcomes of patients with CRPS undergoing surgical implantation of an SCS device.

METHODS

Patients were included if they underwent an SCS procedure at our institution between 2008 and 2016 for chronic pain. Cases were excluded if the procedure involved stimulator removal or if it was an outpatient procedure. Multivariate regression assessed the effect of CRPS and other clinical variables on perioperative outcomes.

RESULTS

Eighty-one inpatient SCS implantation cases for chronic pain were included, with 9 patients (11.1%) having a CRPS diagnosis. The CRPS cohort received higher mean quantities of intraoperative opioids and had a lower proportion of patients reporting meaningful pain reduction (16.7%) in the 24-hour postoperative setting compared with patients without CRPS (35.9%), although this was not statistically significant. Multivariate regression modeling suggested that CRPS was a significant predictor of increased odds of extended time to the postanesthesia care unit discharge (P = 0.0406) and higher direct costs of hospitalization (P = 0.0326).

CONCLUSIONS

Our data suggest that CRPS may pose several unique risks in the perioperative period after inpatient SCS implantation. These findings support the need for future prospective investigations examining risks and outcomes for SCS procedures in this population.

Spinal cord stimulation for the treatment of complex regional pain syndrome leads to improvement of quality of life, reduction of pain and psychological distress: a retrospective case series with 24 months follow up

Background and aims

Complex regional pain syndrome (CRPS) is a common pain condition which is characterized by pain, functional impairment, and trophic changes. Neurosurgical treatment is not widely offered. In this study the treatment with spinal cord stimulation (SCS) was evaluated over 24 months follow up.

Methods

A retrospective case analysis of six patients with severe CRPS was performed. Pain chronicity was recorded with the Mainz Pain Staging System (MPSS). Pain intensity (NRS), activity level and health-related quality of life (EQ-5D-5L), the actual mood state (ASTS), and treatment satisfaction (CSQ-8) were assessed. All patients received conventional pharmacological treatments including multimodal pain therapy through their local pain therapist or in specialized centers as well as physical therapy. A SCS electrode was implanted for trial stimulation. After successful trial a neurostimulator was implanted and connected to the electrode. Patients were retrospectively analyzed before implantation and 6, 12 and 24 months postoperatively. Statistical analysis was performed using Mann–Whitney U and Wilcoxon rank-sum test.

Results

Patients median age was 43 years (IQR25−75 37–43 years). The median MPSS Score was 3 of 3 indicating a high pain chronicity. Median NRS before implantation of the neurostimulator was 8.8 (IQR25−75 7.6–9.3). A reduction to 7.8 (IQR25−75 4.8–8.1; p = 0.14) after 6 months, 6.5 (IQR25−75 3.8–8.1; p = 0.08) after 1 year, and 6.8 (IQR25−75 3.8–8.5; p = 0.15) after 2 years was achieved. Median EQ-5D-5L index value before treatment was 0.27 (IQR25−75 0.25–0.41) indicating a severely lowered quality of life. A significant improvement to 0.53 (IQR25−75 0.26–0.65; p = 0.03) after 6 months, 0.58 (IQR25−75 0.26–0.84; p = 0.03) after 1 year as well as after 2 years was seen. ASTS scale showed an increase of values for positive mood, and a reduction in values for sorrow, fatigue, anger and desperation during the whole follow up period. The treatment satisfaction in the whole cohort with a median CSQ-8 value of 29.5 of 32 was very high.

Conclusion

The results of this small case series showed a significant improvement of the EQ-5D-5L after implantation of a neurostimulator. NRS reduction was not significant but a clear tendency towards reduced values was observed. We therefore conclude that SCS is an alternative option to relieve chronic pain and psychological distress originating from CRPS if non-invasive managements of severe CRPS failed. The preoperative selection plays a crucial role for good results.

Implications

CRPS is difficult to treat. SCS is an alternative option to improve the quality of life and relieve chronic pain originating from severe CRPS if conservative treatment modalities fail. Further psychological distress is reduced in long-term follow up. SCS should be kept in mind for therapy refractory cases.

Outcomes of Sympathetic Blocks in the Management of Complex Regional Pain Syndrome

Editor’s Perspective

What We Already Know about This Topic

What This Article Tells Us That Is New

Background

Sympathetic dysfunction may be present in complex regional pain syndrome, and sympathetic blocks are routinely performed in practice. To investigate the therapeutic and predictive values of sympathetic blocks, the authors test the hypotheses that sympathetic blocks provide analgesic effects that may be associated with the temperature differences between the two extremities before and after the blocks and that the effects of sympathetic blocks may predict the success (defined as achieving more than 50% pain reduction) of spinal cord stimulation trials.

Methods

The authors performed a retrospective study of 318 patients who underwent sympathetic blocks in a major academic center (2009 to 2016) to assess the association between pain reduction and preprocedure temperature difference between the involved and contralateral limbs. The primary outcome was pain improvement by more than 50%, and the secondary outcome was duration of more than 50% pain reduction per patient report. The authors assessed the association between pain reduction and the success rate of spinal cord stimulation trials.

Results

Among the 318 patients, 255 were diagnosed with complex regional pain syndrome and others with various sympathetically related disorders. Successful pain reduction (more than 50%) was observed in 155 patients with complex regional pain syndrome (155 of 255, 61%). The majority of patients (132 of 155, 85%) experienced more than 50% pain relief for 1 to 4 weeks or longer. The degree and duration of pain relief were not associated with preprocedure temperature parameters with estimated odds ratio of 1.03 (97.5% CI, 0.95–1.11) or 1.01 (97.5% CI, 0.96–1.06) for one degree decrease (P = 0.459 or 0.809). There was no difference in the success rate of spinal cord stimulation trials between patients with or without more than 50% pain relief after sympathetic blocks (35 of 40, 88% vs. 26 of 29, 90%, P &gt; 0.990).

Conclusions

The authors conclude that sympathetic blocks may be therapeutic in patients with complex regional pain syndrome regardless of preprocedure limb temperatures. The effects of sympathetic blocks do not predict the success of spinal cord stimulation.

Complex Regional Pain Syndrome Management: An Evaluation of the Risks and Benefits of Spinal Cord Stimulator Use in Pregnancy

OBJECTIVE

We present a case of a young woman diagnosed with complex regional pain syndrome (CRPS) who underwent spinal cord stimulator (SCS) implantation. She had 2 successful pregnancies following implantation.

DESIGN

We evaluated the electronic medical records of the patient following SCS implantation and while pregnant with her second and third children. A phone interview was conducted after her third pregnancy to discuss her experience with SCS use during and after pregnancy.

SETTING

Physical medicine and rehabilitation pain management clinic and obstetrician clinic, affiliated with the Medical College of Wisconsin in Milwaukee, Wisconsin.

SUBJECT

A 26-year-old woman with history of CRPS type I.

RESULTS

This 26-year-old woman was diagnosed with CRPS type I after left knee surgery. All conservative treatments had failed prior to her undergoing SCS implantation after the birth of her first child. SCS implantation brought near complete resolution of her symptoms. When she became pregnant with her second child, she turned off her SCS. Her CRPS symptoms intensified, but she had a normal pregnancy. She turned the SCS back on postpartum and elected to continue its use throughout her third pregnancy. She had a normal pregnancy, and her CRPS symptoms were well controlled. The patient and her children are currently healthy. Her SCS remains functional and effective.

CONCLUSION

Both an SCS and many medications used for pain management in CRPS could cause harm to both mother and fetus in pregnancy. Further research must be done to determine the safety and efficacy of SCS use in pregnancy.

A case report of wireless peripheral nerve stimulation for complex regional pain syndrome type-I of the upper extremity: 1 year follow up

Background

Complex regional pain syndrome (CRPS) is a chronic disabling painful disorder with limited options to achieve therapeutic relief. CRPS type I which follows trauma, may not show obvious damage to the nervous structures and remains dubious in its pathophysiology and also its response to conservative treatment or interventional pain management is elusive. Spinal cord and dorsal root ganglion stimulation (SCS, DRGS) provide good relief, mainly for causalgia or CRPS I of lower extremities but not very encouraging for upper extremity CRPS I. we reported earlier, a case of CRPS I of right arm treated successfully by wireless peripheral nerve stimulation (WPNS) with short term follow up. Here we present 1-year follow-up of this patient.

Objective

To present the first case of WPNS for CRPS I with a year follow up. The patient had minimally invasive peripheral nerve stimulation (PNS), without implantable pulse generator (IPG) or its accessories.

Case report

This was a case of refractory CRPS I after blunt trauma to the right forearm of a young female. She underwent placement of two Stimwave electrodes (Leads: FR4A-RCV-A0 with tines, Generation 1 and FR4A-RCV-B0 with tines, Generation 1) in her forearm under intraoperative electrophysiological and ultrasound guidance along radial and median nerves. This WPNS required no IPG. At high frequency (HF) stimulation (HF 10 kHz/32 μs, 2.0 mA), patient had shown remarkable relief in pain, allodynia and temperature impairment. At 5 months she started driving without opioid consumption, while allodynia disappeared. At 1 year follow up she was relieved of pain [visual analogue scale (VAS) score of 4 from 7] and Kapanji Index (Score) improved to 7–8. Both hands look similar in color and temperature. She never made unscheduled visits to the clinic or visited emergency room for any complications related to the WPNS.

Conclusions

CRPS I involving upper extremity remain difficult to manage with conventional SCS or DRGS because of equipment related adverse events. Minimally invasive WPNS in this case had shown consistent relief without any complications or side effects related to the wireless technology or the technique at the end of 1 year.

Implications

This is the first case illustration of WPNS for CRPS I, successfully treated and followed up for 1 year.

Spinal Stimulation for the Treatment of Intractable Spine and Limb Pain: A Systematic Review of RCTs and Meta-Analysis

OBJECTIVE

To synthesize the evidence regarding the effect of spinal stimulation (SS) vs medical therapy (MT) and the effect of newer SS technologies vs conventional SS on pain reduction in patients with intractable spine or limb pain.

METHODS

A comprehensive literature search was conducted by a reference librarian. The literature search encompassed January 1, 1995 - December 31, 2017. Reviewers worked independently to select and appraise trials. Random-effect meta-analysis and frequentist indirect comparison methods were used to compare the three interventions. Results were expressed as odds ratio (OR) or weighted mean difference (WMD) with 95% CIs.

RESULTS

We identified 12 trials enrolling 980 patients. Compared with MT, SS significantly increased the odds of reducing pain by 50% or more in three trials (OR, 13.01; 95% CI, 4.96-34.17) and significantly reduced pain as measured by visual analogue scale scores in three trials (WMD, 1.43 scale points; 95% CI, 0.16-2.71). Using the common comparator of MT, newer stimulation technology (eg, high-frequency 10 kilohertz spinal stimulation, Burst, dorsal root ganglion) was associated with increased odds of pain relief compared with conventional SS (OR, 2.07; 95% CI, 1.35-3.19).

CONCLUSIONS

In patients with intractable spine/limb pain, SS was associated with better pain reduction than MT. New stimulation technology was likely associated with better pain reduction than conventional stimulation.

Complex regional pain syndrome: a narrative review for the practising clinician

Complex regional pain syndrome (CRPS) is a life-altering condition that usually affects the extremities after a trauma or nerve injury. The physiologic changes that occur as a result of the inciting injury are complex, as the name of the syndrome implies. The pain and disability associated with CRPS often lead to psychological co-morbidities that create a vicious cycle of pain, isolation, and depression. We review recent developments in the understanding of CRPS and advancements in management of this syndrome. Further research in targeting specific mechanisms involved in the pathophysiology of CRPS should lead to prevention of this condition.

The Use of Spinal Cord Stimulation/Neuromodulation in the Management of Chronic Pain

Chronic pain causes a tremendous burden on the society in terms of economic factors and social costs. Rates of spinal surgery, especially spinal fusion, have increased exponentially over the past decade. The opioid epidemic in the United States has been one response to the management of pain, but it has been fraught with numerous catastrophic-related adverse effects. Clinically, spinal cord stimulation (SCS)/neuromodulation has been used in the management of chronic pain (especially spine-related pain) for more than two decades. More recent advances in this field have led to new theories and approaches in which SCS can be used in the management of chronic spine-related pain with precision and efficacy while minimizing adverse effects commonly seen with other forms of chronic pain treatment (eg, narcotics, injections, ablations). Narcotic medications have adverse effects of habituation, nausea, constipation, and the like. Injections sometimes lack efficacy and can have only limited duration of efficacy. Also, they can have adverse effects of cerebrospinal fluid leak, infection, and so on. Ablations can be associated with burning discomfort, lack of efficacy, recurrent symptoms, and infection. High-frequency stimulation, burst stimulation, tonic stimulation with broader paddles, and new stimulation targets such as the dorsal root ganglion hold promise for improved pain management via neuromodulation moving forward. Although a significant rate of complications with SCS technology are well described, this can be a useful tool in the management of chronic spine-related pain.

Effects of Tonic Spinal Cord Stimulation on Sensory Perception in Chronic Pain Patients: A Systematic Review

OBJECTIVES

Even if spinal cord stimulation (SCS) is widely used and effective in treating intractable chronic neuropathic pain conditions, little is known about its possible impacts on sensory perception. Quantitative sensory testing (QST) is a useful tool to assess this issue. The aim of this study was to review the impact of tonic SCS on somatosensory perception quantified by QST in chronic pain patients.

MATERIALS AND METHODS

Relevant articles and abstracts were searched in all languages from CINAHL, Cochrane, Embase, MEDLINE, and Web of Knowledge data bases. Data were extracted and included studies were assessed for risk of bias.

RESULTS

Out of 5610 records, 15 peer-reviewed articles were eligible and included. The results are heterogeneous due to inadequate comparability among studies for populations (a total of 224 patients diagnosed with more than 13 chronic pain conditions), QST parameters (22 measured with 25 different devices) and experimental procedures (study design, comparator, evaluation time, and area tested). The wide variety of studies, designs, populations, and measures included in this review did not lead to strong evidence on how conventional ("tonic") SCS affects sensory processing in patients with chronic pain.

CONCLUSIONS

The data available tend to suggest that conventional SCS does not interfere with perception of external stimuli. New studies that follow a standardized procedure and consider the possible influence of sensory profile, after-effect bias, and confounding factors are required to confirm this observation. Moreover, the impact on sensory perception of other SCS modalities and alternative electrical neuromodulation therapies could also be explored.

Spinal cord stimulation modulates descending pain inhibition and temporal summation of pricking pain in patients with neuropathic pain

BACKGROUND

Spinal cord stimulation (SCS) is an established treatment option for patients with refractory chronic pain conditions. While effects of SCS on dorsal horn neuronal circuitries are intensively studied, current knowledge on the impact of SCS on descending pain pathways is scarce and relies on preclinical data. We aimed to address this topic and hypothesized a significant effect of SCS on descending pain modulation. In light of current efforts to determine the sensitivity of "static" versus "dynamic" somatosensory parameters to characterize pathophysiological pain conditions, all SCS patients were carefully investigated using both classes of somatosensory outcome parameters.

METHODS

Descending pain pathways were investigated by using a "Cold Pressor Test." This test enables to evaluate the efficacy of conditioned pain modulation (CPM) at the individual level. CPM efficacy was assessed in eight neuropathic pain patients (age 55.5 ± 10.6) during the two conditions stimulator "ON" and "OFF." The impact of SCS on "static" and "dynamic" somatosensory parameters was explored by using a quantitative sensory testing (QST) battery.

RESULTS

CPM efficacy on pressure pain sensitivity was nearly absent during "OFF" (- 1.2 ± 5.6% facilitation), but increased significantly to 16.3 ± 3.4% inhibition during "ON" (p = 0.03). While most "static" nociceptive QST parameters, represented by mechanical/thermal pain thresholds, exhibited only small effects of SCS (p > 0.05), the wind-up ratio was strongly reduced to within the normal range during "ON" (p = 0.04; Cohen's d = 1.0). Dynamic mechanical allodynia was abolished in six of seven patients.

CONCLUSIONS

Our study provides first human evidence for an impact of SCS on descending pain pathways in the dorsolateral funiculus and emphasizes the significance of "dynamic" pain measures like "CPM"-efficacy and "temporal summation" to evaluate SCS treatment effects. Future prospective studies may use these measures of nociceptive processing to predict SCS therapy response.

Wireless peripheral nerve stimulation for complex regional pain syndrome type I of the upper extremity: a case illustration introducing a novel technology

Background

Complex regional pain syndrome (CRPS) is a debilitating painful disorder, cryptic in its pathophysiology and refractory condition with limited therapeutic options. Type I CRPS with its variable relationship to trauma has often no discernible fractures or nerve injuries and remains enigmatic in its response to conservative treatment as well as the other limited interventional therapies. Neuromodulation in the form of spinal cord and dorsal root ganglion stimulation (SCS, DRGS) has shown encouraging results, especially of causalgia or CRPS I of lower extremities. Upper extremity CRPS I is far more difficult.

Objective

To report a case of upper extremity CRPS I treated by wireless peripheral nerve stimulation (WPNS) for its unique features and minimally invasive technique. The system does not involve implantation of battery or its connections.

Case report

A 47 year old female patient presented with refractory CRPS I following a blunt trauma to her right forearm. As interventional treatment in the form of local anesthetics (Anesthesia of peripheral branches of radial nerve) and combined infusions of ketamine/lidocaine failed to provide any significant relief she opted for WPNS treatment. Based on the topographic distribution, two electrodes (Stimwave Leads: FR4A-RCV-A0 with tines, Generation 1 and FR4A-RCV-B0 with tines, Generation 1), were placed along the course of radial and median nerves under ultrasonography monitoring and guided by intraoperative stimulation. This procedure did not involve implantation of extension cables or the power source. At a frequency of 60 Hz and 300 μs the stimulation induced paresthesia along the distribution of the nerves. Therapeutic relief was observed with high frequency (HF) stimulation (HF 10 kHz/32 μs, 2.0 mA) reducing her pain from a visual analogue scale (VAS) score of 7–4 postoperatively. Three HF stimulations programs were provided at the time of discharge, as she improved in her sensory impairment to touch, pressure and temperature at her first follow up visit. At 5-months she was able to drive, did not require opioids and allodynia disappeared.

Conclusions

In a case with difficult CRPS I involving upper extremity, a minimally invasive WPNS of radial and median nerves provided good symptomatic relief. The procedure was tolerated well and both electrodes remained in place without any adverse events.

Implications

In view of the very limited options currently available to manage CRPS, WPNS can be a promising therapeutic modality.

Complex Regional Pain Syndrome, Current Concepts and Treatment Options

PURPOSE OF REVIEW

Complex regional pain syndrome (CRPS) refers to a chronic pain condition that is characterized by progressively worsening spontaneous regional pain without dermatomal distribution. The symptomatology includes pain out of proportion in time and severity to the inciting event. The purpose of this review is to present the most current information concerning epidemiology, diagnosis, pathophysiology, and therapy for CRPS.

RECENT FINDINGS

In recent years, discovery of pathophysiologic mechanisms of CRPS has led to significant strides in the understanding of the disease process. Continued elucidation of the underlying pathophysiological mechanisms will allow for the development of more targeted and effective evidence-based therapy protocols. Further large clinical trials are needed to investigate mechanisms and treatment of the disorder.

Prevalence and Cost Analysis of Complex Regional Pain Syndrome (CRPS): A Role for Neuromodulation

OBJECTIVE

The diagnosis and treatment of complex regional pain syndrome (CRPS) is challenging and there is a paucity of data describing its overall cost burden and quantifying its impact on the US healthcare system. The aim of this study was to assess the prevalence and healthcare utilization costs associated with CRPS.

MATERIALS AND METHODS

A retrospective longitudinal study was performed using the Truven MarketScan® database to identify patients with a new indexed diagnosis of CRPS (Type I, II, or both) from 2001 to 2012. We collected total, outpatient, and pain prescription costs three years prior to CRPS diagnosis (baseline), at year of CRPS diagnosis, and eight-year post-CRPS diagnosis. A longitudinal multivariate analysis was used to model the estimated total and pain prescription cost ratios comparing patients diagnosed before and after CRPS.

RESULTS

We included 35,316 patients with a newly indexed diagnosis of CRPS (Type I: n = 18,703, Type II: n = 14,599, Unspecified: n = 2014). Baseline characteristics were similar between the CRPS cohorts. Compared to two- and three-year baseline costs, one-year prior to diagnosis for all CRPS patients yielded the highest interquartile median [IQR] costs: total costs $7904[$3469, $16,084]; outpatient costs $6706[$3119, $12,715]; and pain prescription costs $1862[$147, $7649]. At the year of CRPS diagnosis, the median [IQR] costs were significantly higher than baseline costs: total costs $8508[$3943, $16,666]; outpatient costs $7251[$3527, $13,568]; and pain prescription costs $2077[$140, $8856]. Over the eight-year period after CRPS diagnosis, costs between all the years were similar, ranging from the highest (one-year) to lowest (seven-years), $4845 to $3888. The median total cumulative cost 8-years after CRPS diagnosis was $43,026 and $12,037 for pain prescription costs. [Correction added on 06 November 2017 after first online publication: the preceding sentence has been updated to demonstrate the median cumulative cost in replacement of the additive cumulative mean costs.]. During the CRPS diagnosis period, patients are expected to have a total cost 2.17-fold and prescription cost 2.56-fold of their baseline cost annually.

CONCLUSIONS

Our study demonstrates that there is a significant increase in cost and healthcare resource utilization one-year prior to and around the time of CRPS diagnosis. Furthermore, there is an increased annual cost post-diagnosis compared to baseline costs prior to CRPS diagnosis.