The natural history of complex regional pain syndrome. Clin J Pain. 2009;25:273-280. [PMID: 19590474 DOI: 10.1097/ajp.0b013e31818ecea5]

Is CRPS-1 a Chronic Disabling Disease? A Long-term, Real-Life Study on Patients Treated With Neridronate

Background

Complex Regional Pain Syndrome type 1 (CRPS-1) is severely debilitating and painful disease that is difficult to treat.

Objective

The objective was to evaluate the long-term residual disability of patients with CRPS-1 following parenteral neridronate treatment.

Design

This is real-life retrospective observational study.

Methods

Patients affected by CRPS-1 of the upper limb were treated with neridronate infusions (400 mg over 10 days) between February 2017 and December 2021 for whom clinical and demographic information was collected. From November 2022, patients treated ⩾1 year previously were recalled for clinical evaluation. A dedicated instrument (DASH questionnaire, Disabilities of the Arm, Shoulder and Hand) was employed to assess residual disability. Multivariate logistic regression analysis was used to investigate predictors of disability.

Results

Forty-nine patients aged 61.1 ± 11.5 years and 73.5% female with CRPS-1 of the upper limb were included. Disease duration before treatment was 9.9 ± 8.0 weeks, and the mean length of follow-up was 4 years (47.7 ± 22.0 months). The disease had fully resolved in 46 patients (93.9%) for whom the diagnostic criteria were no longer recognized. According to the DASH score, 38 patients (77.6%) resulted free of functional limitations, whereas 11 patients (22.4%) were still suffering from disability. The DASH score was positively correlated with residual visual analogue scale (VAS; Spearman's Rho = 0.61; P < .001). Predictors of residual disability were younger age (odds ratio [OR]: 0.77, 95% CI: 0.63-0.93; P = .012) and delay between disease onset and treatment (OR: 1.45, 95% CI: 1.13-1.96; P = .004).

Conclusions

In this real-life study, neridronate parenteral treatment provided a full recovery of CRPS-1 in over 3 quarters of patients, provided they are treated early.

Chronic Widespread Pain

OBJECTIVE

This article reviews the potential etiologies of chronic widespread pain syndromes and outlines a practical approach to the management of patients with these disorders.

LATEST DEVELOPMENTS

Recent updates to diagnostic criteria for primary chronic widespread pain syndromes have allowed for more effective diagnosis. Fibromyalgia is the most common presentation of chronic widespread pain, and the concept of nociplastic pain has been used to describe pain that is related to altered processing of pain sensory pathways. Research studies have provided a better understanding of the pathophysiology of the central augmentation that occurs in patients with nociplastic pain and fibromyalgia.

ESSENTIAL POINTS

Primary chronic widespread pain and fibromyalgia have established diagnostic criteria in which chronic pain involves multiple defined regions and occurs for longer than 3 months. Evaluation of chronic widespread pain should be directed by the clinical presentation. Neurologic disease can present with chronic widespread pain but is accompanied by associated signs and symptoms. Patients with chronic widespread pain benefit from effective communication that validates concerns, provides an understandable explanation of the presenting symptoms, and sets realistic expectations in outcomes using a comprehensive multimodal care plan.

Somatotopic disruption of the functional connectivity of the primary sensorimotor cortex in complex regional pain syndrome type 1

In complex regional pain syndrome (CRPS), the representation area of the affected limb in the primary sensorimotor cortex (SM1) reacts abnormally during sensory stimulation and motor actions. We recorded 3T functional magnetic resonance imaging resting-state data from 17 upper-limb CRPS type 1 patients and 19 healthy control subjects to identify alterations of patients' SM1 function during spontaneous pain and to find out how the spatial distribution of these alterations were related to peripheral symptoms. Seed-based correlations and independent component analyses indicated that patients' upper-limb SM1 representation areas display (i) reduced interhemispheric connectivity, associated with the combined effect of intensity and spatial extent of limb pain, (ii) increased connectivity with the right anterior insula that positively correlated with the duration of CRPS, (iii) increased connectivity with periaqueductal gray matter, and (iv) disengagement from the other parts of the SM1 network. These findings, now reported for the first time in CRPS, parallel the alterations found in patients suffering from other chronic pain conditions or from limb denervation; they also agree with findings in healthy persons who are exposed to experimental pain or have used their limbs asymmetrically. Our results suggest that CRPS is associated with a sustained and somatotopically specific alteration of SM1 function, that has correspondence to the spatial distribution of the peripheral manifestations and to the duration of the syndrome.

Diagnosis and Outcomes of 225 Consecutive Cases of Complex Regional Pain Syndrome of the Hand

BACKGROUND

The lack of specific tests and potential diagnostic inaccuracy may be behind the stunning figures of complex regional pain syndrome (CRPS) cases. The author tested the hypothesis that patients diagnosed with CRPS at referral could be assigned to recognized conditions and treated accordingly.

METHODS

From January of 2018 to April of 2021, 225 consecutive patients attended the author's office having been diagnosed with and treated for CRPS for an average of 16 ± 26 months. There were 180 women and 45 men; no patient was excluded.

RESULTS

All patients could be allocated in named conditions: 79 had a wrong diagnosis; seven had a true causalgia; 16 were dystonic-psychogenic hands; 20 presented a flare reaction; and 90 had an "irritative" carpal tunnel syndrome. The remaining 13 patients had a miscellany of symptoms within a substandard management setting. Surgery was offered to 175 with a correctable cause; 50 (20 of whom had a tangible cause responsible for their pain) declined, and their outcome is unknown. The remaining 125 were operated on and tracked for an average of 20 ± 9 months. In the operated group, pain dropped 7.5 ± 2.2 points ( P < 0.0001) on a numerical rating scale of 0 to 10. Disabilities of the Arm, Shoulder, and Hand questionnaire scores fell from 80 to 16 ( P < 0.0001). Patients who were operated on rated their satisfaction on a scale of 0 to 10 as 8.9 ± 1.9.

CONCLUSIONS

Unlike with CRPS, all patients in this series had a true, diagnosable condition explaining their clinical picture. Most patients who agreed to be operated on had a favorable outcome.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Randomized controlled study to evaluate the efficacy and safety of soticlestat as adjunctive therapy in adults with complex regional pain syndrome

OBJECTIVE

The objective was to investigate the efficacy and safety of soticlestat as adjunctive therapy in participants with complex regional pain syndrome (CRPS).

DESIGN

A proof-of-concept phase 2a study, comprising a 15-week randomized, double-blind, placebo-controlled, parallel-group study (part A), and an optional 14-week open-label extension (part B).

METHODS

Twenty-four participants (median age 44.5 years [range, 18-62 years]; 70.8% female) with chronic CRPS were randomized (2:1) to receive oral soticlestat or placebo. Soticlestat dosing started at 100 mg twice daily and was titrated up to 300 mg twice daily. In part B, soticlestat dosing started at 200 mg twice daily and was titrated up or down at the investigator's discretion. Pain intensity scores using the 11-point Numeric Pain Scale (NPS) were collected daily. The Patient-Reported Outcomes Measurement Information System (PROMIS)-29, Patients' Global Impression of Change (PGI-C), and CRPS Severity Score (CSS) were completed at screening and weeks 15 and 29.

RESULTS

From baseline to week 15, soticlestat treatment was associated with a mean change in 24-hour pain intensity NPS score (95% confidence interval) of -0.75 (-1.55, 0.05) vs -0.41 (-1.41, 0.59) in the placebo group, resulting in a non-significant placebo-adjusted difference of -0.34 (-1.55, 0.88; P = .570). Statistically non-significant numerical changes were observed for the PROMIS-29, PGI-C, and CSS at weeks 15 and 29.

CONCLUSIONS

Adjunctive soticlestat treatment did not significantly reduce pain intensity in participants with chronic CRPS.

Ketamine for Complex Regional Pain Syndrome: A Narrative Review Highlighting Dosing Practices and Treatment Response

This is a narrative review of intravenous ketamine infusions for the treatment of complex regional pain syndrome (CRPS). It briefly covers the definition of CRPS, its epidemiology, and other treatments before introducing ketamine as the article's focus. A summary of ketamine's evidence base and its mechanisms of action is provided. The authors then review ketamine dosages reported in peer-reviewed literature for the treatment of CRPS, and their associated duration of pain relief. The observed response rates to ketamine and predictors of treatment response are also discussed.

Hand Allodynia, Lack of Finger Flexion, and the Need for Carpal Tunnel Release

PURPOSE

The clinical features of classic carpal tunnel syndrome are well known. However, some patients who may respond equally well to carpal tunnel release (CTR) display atypical signs and symptoms. The chief differential features are allodynia (painful dysesthesias), lack of finger flexion, and, on examination, pain on passive finger flexion. The goal of the study was to present the clinical features, increase awareness, facilitate accurate diagnosis, and report the outcomes after surgery.

METHODS

Thirty-five hands, from 22 patients with the main features of allodynia and lack of full finger flexion, were gathered in the period 2014-2021. The other common complaints included sleeping disturbances (20 patients), hand swelling (31 hands), and shoulder pain on the same side as the hand problem with limited range of motion (30 sides). The Tinel or Phalen signs were obscured by the pain. However, pain with passive flexion of the fingers was universally present. All the patients were treated with carpal tunnel release through a mini-incision approach: four patients had a trigger finger, which was treated concomitantly in six hands, and one patient underwent contralateral CTR for carpal tunnel syndrome with a more standard presentation.

RESULTS

At a minimum of 6 months of follow-up (mean, 22 months; range, 6-60 months), the pain decreased by 7.5 ± 1.9 points on the Numerical Rating Scale, which ranges from 0 to 10. The pulp-to-palm distance improved from 3.7 to 0.3 cm. The mean Disabilities of the Arm, Shoulder, and Hand score decreased from 67 to 20. The mean Single-Assessment Numeric Evaluation score for the whole group was 9.7 ± 0.6.

CONCLUSIONS

Hand allodynia and lack of finger flexion may be indications of median neuropathy in the carpal canal, which responds to CTR. Awareness of this condition is important because the uncharacteristic clinical presentation may not be considered an indication for surgery that can be beneficial.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Biological and psychological early prognostic factors in complex regional pain syndrome: A systematic review

BACKGROUND AND OBJECTIVE

Several risk factors for the onset of CRPS have been found, but evidence for prognostic factors associated with the progression of this condition remains sparse. However, the detection and management of these factors are necessary to design secondary prevention strategies. The objective of this systematic review was to identify prognostic factors in adult individuals with early CRPS.

DATABASE AND DATA TREATMENT

PubMed, Embase, PsycINFO, Cochrane Library and Scopus, were published between January 1990 and November 2021. Two independent investigators selected cross-sectional and longitudinal studies looking at early (<12 weeks from onset) prognostic factors for pain, CRPS severity score, disability, return to work, or quality of life. The quality in prognostic studies (QUIPS) tool was used to assess the risk of bias. A qualitative meta-synthesis was performed.

RESULTS

Out of 4652 different articles, six studies met the inclusion criteria. We identified 21 early factors associated with a poorer prognosis in type I CRPS. We found moderate evidence to support six of them: higher pain intensity, self-rated disability, anxiety, pain-related fear, being a female and high-energy triggering event. Only two studies had an overall low risk of bias.

CONCLUSIONS

This study showed an important lack of information on early prognostic factors in CRPS. Only one article investigated the link with psychological characteristics. There is a crucial need for larger studies, with a well-defined population using validated measures.

SIGNIFICANCE

This systematic review highlights the lack of knowledge about early prognostic factors in CRPS. A few putative prognostic factors were identified. Most of the moderate evidence is related to a single cohort. Future research is required to find out which patients are vulnerable to chronification.

Outcomes of Carpal Tunnel Release in Complex Regional Pain Syndrome/Reflex Sympathetic Dystrophy/Sudeck Disease Patients

BACKGROUND

The clinical features of classic carpal tunnel syndrome are well known. However, some patients who display atypical symptoms and signs of pain and dysesthesias in the hand, worsening of symptoms at night, and above all, inability to make a full fist, respond equally well to carpal tunnel release. This same clinical picture was shared by some patients labeled as having complex regional pain syndrome. Because of the poor outcome of complex regional pain syndrome patients with current regimens, the authors tested the hypothesis that carpal tunnel release could be effective on them. The purpose of this article is to report the outcome of carpal tunnel release in complex regional pain syndrome patients who presented the above signs and symptoms.

METHODS

Fifty-three patients with an average age of 55 years presenting the above cluster of symptoms were operated on. All were unilateral cases, had sustained trauma, and were treated for complex regional pain syndrome before referral for an average of 16 months. All patients underwent carpal tunnel release.

RESULTS

At a minimum of 6 months' follow-up, pain dropped 7.5 points on a numerical rating scale of 0 to 10 ( p < 0.001). Disabilities of the Arm, Shoulder and Hand scoring fell from 82 to 17 ( p < 0.001). Six patients had an unsatisfactory result.

CONCLUSIONS

Some patients with complex regional pain syndrome may respond successfully to a carpal tunnel release operation. Recognition of this possibility is crucial, as the symptoms and signs might lead the clinician away from the proper diagnosis and treatment.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Complex regional pain syndrome what is the outcome? - a systematic review of the course and impact of CRPS at 12 months from symptom onset and beyond

Background and Objective

To improve CRPS treatment, it is imperative to understand the nature, degree and relative importance of ongoing problems associated with CRPS. The objective of this systematic review was to summarize the published data concerning measures of function and impact including occupational parameters, of CRPS at 12 months from symptom onset and beyond.

Databases and Data Treatment

MEDLINE, EmBase and PsychINFO were searched (inception to May 2021). Study cohorts were eligible if they included; adult patients with the primary complaint of CRPS ≥12 months duration, outcomes that reported change in CRPS signs and symptoms, and physical and social function. Prospero registration: CRD42021241785.

Results

Twenty‐two included studies suggest that pain and motor dysfunction are the most dominant long‐term features of CRPS, persisting for 51%–89% of patients at ≥12 months. On average for all patients who had CRPS at baseline, grip strength was found to be reduced by 25%–66%, and range of motion reduced by 20%–25% at ≥12 months. Such losses were associated with physical and social disability. Thirty to forty percent of all patients did not return to work and a further 27%–35% of persons returned to work but required some form of workplace adaptation, although the quality of this data was poor. Quality assessment highlighted limitations in the literature, such as high attrition bias and variations in diagnostic criteria.

Conclusions

Results provide first‐time quantitative data including specific evidence about losses to motor function and long‐term compromises to work status. Results demonstrate that the ongoing impact of one episode of CRPS on limb function and work status is relatively high.

Significance

This review provides first‐time clarity in relation to outcomes of limb function and work status associated with an episode of CRPS, beyond 12 months from onset. Results demonstrate that the long‐term impact of an episode of CRPS on these outcomes is much larger than previously described, and thus also illustrates how the wider health economic impact of CRPS is not yet fully understood. We additionally highlight the need for future research that identifies long‐term predictors, and treatments that can foster good functional and occupational recovery.

Innovations and advances in modelling and measuring pain in animals

Best practices in preclinical algesiometry (pain behaviour testing) have shifted over the past decade as a result of technological advancements, the continued dearth of translational progress and the emphasis that funding institutions and journals have placed on rigour and reproducibility. Here we describe the changing trends in research methods by analysing the methods reported in preclinical pain publications from the past 40 years, with a focus on the last 5 years. We also discuss how the status quo may be hampering translational success. This discussion is centred on four fundamental decisions that apply to every pain behaviour experiment: choice of subject (model organism), choice of assay (pain-inducing injury), laboratory environment and choice of outcome measures. Finally, we discuss how human tissues, which are increasingly accessible, can be used to validate the translatability of targets and mechanisms identified in animal pain models.

"I Don't Identify with It": A Qualitative Analysis of People's Experiences of Living with Complex Regional Pain Styndrome

OBJECTIVE

Complex regional pain syndrome (CRPS) is a painful limb condition known to cause significant disability and distress. However, little previous research has explored CRPS from a patient perspective. The present qualitative study aimed to describe the experiences of people living with CRPS.

SUBJECTS

Forty-eight people with CRPS participated in this research.

METHODS

Participants completed a face-to-face or telephone interview about their perceptions and experiences of CRPS and completed three drawings to illustrate their experiences. Data were analyzed through reflexive thematic analysis, and images in drawings were grouped and coded by theme.

RESULTS

Three overarching themes encapsulated the data, including that 1) people experience CRPS as a source of severe symptoms and emotional difficulties, 2) CRPS undermines personal and social identity, and 3) this results in psychological responses that protect against the emotional and social impact of severe symptoms. Psychological responses include: a) searching for an explanation, b) "nothing is my fault," emphasizing a lack of personal responsibility and personal control, and c) detaching the limb from the self.

CONCLUSIONS

CRPS is experienced as highly threatening to physical ability, psychological state, and identity. In response to these threats, people may develop their own explanations for CRPS and may mentally detach themselves from responsibility, control, and the painful limb itself. Future research could explore the impact of these factors on psychological well-being and CRPS symptoms and outcomes.

Roles of Long Non-coding RNAs in the Development of Chronic Pain

Chronic pain, a severe public health issue, affects the quality of life of patients and results in a major socioeconomic burden. Only limited drug treatments for chronic pain are available, and they have insufficient efficacy. Recent studies have found that the expression of long non-coding RNAs (lncRNAs) is dysregulated in various chronic pain models, including chronic neuropathic pain, chronic inflammatory pain, and chronic cancer-related pain. Studies have also explored the effect of these dysregulated lncRNAs on the activation of microRNAs, inflammatory cytokines, and so on. These mechanisms have been widely demonstrated to play a critical role in the development of chronic pain. The findings of these studies indicate the significant roles of dysregulated lncRNAs in chronic pain in the dorsal root ganglion and spinal cord, following peripheral or central nerve lesions. This review summarizes the mechanism underlying the abnormal expression of lncRNAs in the development of chronic pain induced by peripheral nerve injury, diabetic neuropathy, inflammatory response, trigeminal neuralgia, spinal cord injury, cancer metastasis, and other conditions. Understanding the effect of lncRNAs may provide a novel insight that targeting lncRNAs could be a potential candidate for therapeutic intervention in chronic pain.

Determinants of Diagnostic Delay in Complex Regional Pain Syndrome Type 1: An Observational Study of 180 Consecutive New Cases

BACKGROUND/OBJECTIVE

Complex regional pain syndrome type 1 (CRPS-1) is a disabling painful disease, with variable outcomes in terms of chronic pain and disability. A long time between onset and diagnosis seems predictive for late recovery and progression toward a chronic disease. This study aims to investigate demographic and clinical variables associated with delayed CRPS-1 diagnosis.

METHODS

From March 2013 to January 2018, consecutive patients newly diagnosed according to International Association for the Study of Pain diagnostic criteria for CRPS-1 were recruited. Demographic and clinical variables were collected at diagnosis. Student t test and Mann-Whitney U test were used for comparisons; Cox proportional hazards model was applied to evaluate the variables associated with delayed CRPS-1 diagnosis.

RESULTS

One hundred eighty patients entered the study. At diagnosis, women were older, and foot was more often involved than hand. The triggering event was more commonly a trauma without fracture for foot disease and a fracture for hand localization. No differences between hand and foot disease were found by the International Association for the Study of Pain diagnostic categories (clinical vs research) or pain measures. Variables significantly associated with a longer time between disease onset and diagnosis were foot localization, general practitioner referral, higher number of visits before CRPS diagnosis, and prior physiotherapy prescribed for symptoms later diagnosed as CRPS. An overt clinical manifestation (research CRPS-1) predicted a shorter delay.

CONCLUSIONS

Foot localization, prior physiotherapy prescribed for symptoms later diagnosed as CRPS, and a disease without overt clinical manifestations were independent predictive factors for a delayed diagnosis. Clinicians should pay attention to these issues to ensure a timely diagnosis and possibly avoid progression toward a chronic disease.

The Utility of Dynamic Movement Orthoses in the Management of Complex Regional Pain Syndrome-A Case Series

Complex regional pain syndrome (CRPS) is a relatively rare, but debilitating condition that may occur after limb or peripheral nerve trauma. Typical symptoms of CRPS include swelling, allodynia, hyperalgesia, and skin temperature changes. Although a variety of pharmacological and non-pharmacological approaches are commonly used in caring for individuals with CRPS, they are frequently ineffective and often associated with side effects and/or additional risks. Previously, elastomeric orthotic garments have been shown to decrease neuropathic pain, reduce edema, and increase proprioception, but no previous reports have described their use in treating CRPS. Accordingly, this case series describes our experiences using a Lycra-based, custom-fabricated Dynamic Movement Orthosis (DMO) as a novel treatment to reduce the symptoms of CRPS and promote function. Four patients were included in this case series, all of whom had very different causes for their CRPS, including a combat-related gunshot injury resulting in multiple foot fractures with a partial nerve injury, a post-metatarsophalangeal fusion, an L5 radiculopathy, and a case of post-lower leg fasciotomies. These four patients all reported subjective improvement in their pain, function, and exercise tolerance in association with their DMO use. All patients demonstrated reduced use of analgesic medications. The pre- and post-DMO lower extremity functional scale showed clinically significant improvement in the two patients for which it was obtained.

Circulating microRNAs from the mouse tibia fracture model reflect the signature from patients with complex regional pain syndrome

INTRODUCTION

Complex regional pain syndrome (CRPS) often results from an initial trauma that later produces a disproportionate amount of pain. The mechanisms underlying CRPS have been studied using a tibia fracture model (TFM) in rodents because this model closely mimics symptoms and has several molecular correlates observed in patients with CRPS.

OBJECTIVE

Here, we determined whether the TFM has alterations in circulating microRNAs (miRNAs) and cytokines transported by small extracellular vesicles (sEVs) that faithfully model previously reported miRNA alterations from patients with CRPS.

METHODS

We isolated and characterized serum-derived sEVs from mice 3 weeks after fracture when symptoms such as pain hypersensitivity develop. Whole-transcriptome profiling was used to determine sEV miRNAs, and Bio-Plex Pro Mouse Cytokine 23-plex assay was used to measure cytokines. Differentially expressed miRNAs from TFM were compared with previously reported circulating miRNA alterations from patients with CRPS.

RESULTS

Although sEV cytokine levels were unchanged, there were significant changes in sEV miRNA profiles. Differentially expressed miRNAs from TFM sEVs significantly overlapped with those previously reported in patients with CRPS. Of the 57 sEV miRNAs dysregulated in the TFM, 30 were previously reported in patients with CRPS compared with healthy control donors both in sEVs and 23 in whole blood.

CONCLUSIONS

These findings enhance the validity of TFM as a model for CRPS and suggest that specific miRNA dysregulation may be a shared feature of CRPS and the TFM. These dysregulated miRNAs could help identify mechanistic targets or serve as biomarker candidates for both diagnosis and treatment responses in clinical trials.

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.

Effects of photobiomodulation on different application points and different phases of complex regional pain syndrome type I in the experimental model

BACKGROUND

Complex regional pain syndrome type I (CRPS-I) consists of disorders caused by spontaneous pain or induced by some stimulus. The objective was to verify the effects of photobiomodulation (PBM) using 830 nm wavelength light at the affected paw and involved spinal cord segments during the warm or acute phase.

METHODS

Fifty-six mice were randomized into seven groups. Group (G) 1 was the placebo group; G2 and G3 were treated with PBM on the paw in the warm and acute phase, respectively; G4 and G5 treated with PBM on involved spinal cord segments in the warm and acute phase, respectively; G6 and G7 treated with PBM on paw and involved spinal cord segments in the warm and acute phase, respectively. Edema degree, thermal and mechanical hyperalgesia, skin temperature, and functional quality of gait (Sciatic Static Index [SSI] and Sciatic Functional Index [SFI]) were evaluated.

RESULTS

Edema was lower in G3 and G7, and these were the only groups to return to baseline values at the end of treatment. For thermal hyperalgesia only G3 and G5 returned to baseline values. Regarding mechanical hyperalgesia, the groups did not show significant differences. Thermography showed increased temperature in all groups on the seventh day. In SSI and SFI assessment, G3 and G7 showed lower values when compared to G1, respectively.

CONCLUSIONS

PBM irradiation in the acute phase and in the affected paw showed better results in reducing edema, thermal and mechanical hyperalgesia, and in improving gait quality, demonstrating efficacy in treatment of CRPS-I symptoms.

Complex Regional Pain Syndrome Caused by an Axillary Lipoma

Complex regional pain syndrome (CRPS), formerly known as reflex sympathetic dystrophy syndrome, is a rare chronic neuro-inflammatory pain condition, which can follow a soft-tissue, bone (type I), or nerve injury (type II) that can be severe and often lasts longer than the original tissue damage. Lipomas impinging on the brachial plexus are rare. To date, there have been no documented cases of CRPS caused by a benign tumor. Here, we report a rare case of CRPS caused by surgical removal of a left axillary lipoma impinging on the brachial plexus. The patient presented with neuropathic pain and hyperalgesia of the left arm, in a non-dermatomal pattern, and pain out of proportion to touch and painful stimulus. Persistent CRPS continued to occur post-operatively for one year without significant change in her pain characteristics. CRPS following elective or emergent surgery to the extremities can pose significant complications to recovery and post-operative care. This condition can be induced through surgery or trauma, which can complicate recovery, impair motor functionality, and cause debilitating pain. Treatment modalities and pathogenesis for CRPS remain obscure and limited, which leads to wide misdiagnosis. Our case highlights the importance of considering CRPS when evaluating differential diagnoses for pre- and post-operative conditions affecting the upper and lower extremities.

Chiropractic Care of a Patient With Complex Regional Pain Syndrome Type 1 (CRPS-1): A Case Report

Objective

The purpose of this case report is to describe the evaluation and treatment of a patient presenting with left upper extremity pain and neck pain after a slip and fall.

Clinical Features

A 56-year-old woman sustained a left distal radius fracture secondary to a slip-and-fall accident. She was placed in a cast for 6 weeks, and after the removal of her cast she developed excruciating left forearm, wrist, hand, and finger pain. The patient was diagnosed with complex regional pain syndrome type 1 utilizing the modified (Budapest) International Association for the Study of Pain criteria.

Intervention and Outcome

The patient did not respond positively to initial management, which included the application of a cast after closed reduction of the distal radius fracture, 8 weeks of physical/occupational therapy, and the use of a brace which kept her left wrist, hand, and fingers in a flexed position. Subsequently, the patient presented to the University of Bridgeport College of Chiropractic outpatient clinic, where she was evaluated and treated. She received a total of 36 chiropractic treatments between her initial office visit in January 2018 and the follow-up in June 2018. The patient reported and demonstrated amelioration of her presenting complaints, decreased pain, increased ranges of motion, and increased function.

Conclusion

This case report underscores the importance of a rapid, accurate, initial diagnosis of complex regional pain syndrome type 1, during the acute (warm) stage.

Complex regional pain syndrome: an evolving perspective

BACKGROUND

Complex regional pain syndrome (CRPS) is a heterogenous and poorly understood condition that can be provoked by quite minor injuries. The symptoms and signs of CRPS persist, long after the patient has recovered from the inciting event. In some cases, there is a clear association with a peripheral nerve injury. The degree of disability produced by CRPS is often out of proportion to the scale of the original insult and the condition is associated with protracted recovery times and frequent litigation.

METHODS

We have performed a PubMed literature search, referenced landmark papers in the field and included a national expert in peripheral nerve injury and repair in our team of authors.

RESULTS AND CONCLUSIONS

The diagnostic criteria for CRPS have changed repeatedly over the last two centuries and much of the historical literature is difficult to compare with more recent research. In this review article, we consider how our understanding of the condition has evolved and discuss its pathogenesis, its apparent heterogenicity and the various investigations and treatments available to the clinician.

Prognostic Factors in Complex Regional Pain Syndrome Type 1 Occurring in the Korean Army

OBJECTIVES

In Korea, patients diagnosed with complex regional pain syndrome (CRPS) in the army are typically discharged from the army; however, the course of the disease after discharge is not known. The purpose of this study was to investigate the course of CRPS that occurred in the army and to identify the influences of various clinical and psychosocial factors immediately before discharge on the disease course.

METHODS

Clinical profiles and psychosocial status were collected from the medical records of 16 patients with CRPS type 1 who were discharged during the period between March 2017 and April 2018. The degree of improvement after discharge was assessed by follow-up evaluation through telephone contact. Cox proportional hazards regression was performed to identify clinical and psychosocial predictors for the rate of recovery.

RESULTS

The median time to recovery after discharge was 39 weeks (95% confidence interval [CI] = 8.8-69.2 weeks). The sole predictor for time to recovery after discharge was the time period from the onset of pain to discharge. Each one-week increase in the duration of pain experienced in the military was associated with a 18.2% (95% CI = 5.3%-29.5%) reduction in the rate of recovery after discharge (P = 0.007).

CONCLUSIONS

Patients who experienced a short period of pain in the military demonstrated a relatively good prognosis after discharge. This may show how prolonged pain in the army could affect the experience of pain from a social point of view, in that it shows the disease course after a change in the social environment.

Direct Health Care Cost and Work Incapacity Related to Complex Regional Pain Syndrome in Switzerland: A Retrospective Analysis from 2008 to 2015

OBJECTIVE

First, to determine the number of accident-related complex regional pain syndrome (CRPS) cases from 2008 to 2015 and to identify factors associated with an increased risk for developing CRPS. Second, to analyze the duration of work incapacity and direct health care costs over follow-up periods of two and five years, respectively.

DESIGN

Retrospective data analysis.

SETTING

Database from the Statistical Service for the Swiss National Accident Insurances covering all accidents insured under the compulsory Swiss Accident Insurance Law.

SUBJECTS

Subjects were registered after an accident between 2008 and 2015.

METHODS

Cases were retrospectively retrieved from the Statistical Service for the Swiss National Accident Insurances. Cases were identified using the appropriate International Classification of Diseases, 10th Revision, codes.

RESULTS

CRPS accounted for 0.15% of all accident cases. Age, female gender (odds ratio [OR] = 1.53, 95% confidence interval [CI] = 1.47-1.60), and fracture of the forearm (OR = 38, 95% CI = 35-42) were related to an increased risk of developing CRPS. Over five years, one CRPS case accumulated average insurance costs of $86,900 USD and treatment costs of $23,300 USD. Insurance costs were 19 times and treatment costs 13 times the average costs of accidents without CPRS. Within the first two years after the accident, the number of days lost at work was 20 times higher in patients with CRPS (330 ± 7 days) than in patients without CRPS (16.1 ± 0.1 days). Two-thirds of all CRPS cases developed long-term work incapacity of more than 90 days.

CONCLUSION

CRPS is a relatively rare condition but is associated with high direct health care costs and work incapacity.

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.

The Evolving Role of High-Frequency Spinal Cord Stimulation as Salvage Therapy in Neurostimulation

BACKGROUND

High-frequency 10-kHz spinal cord stimulation (10-kHz SCS) has shown promise in multicenter prospective trials for the management of chronic back and leg pain. Traditional spinal cord stimulation (t-SCS) has a long history of effectiveness in chronic neuropathic syndromes but not uncommonly can fail to provide long-term relief, leaving a significant group of patients with unsatisfactory outcomes. There is mounting evidence that 10-kHz SCS may offer relief in this subset of patients.

METHODS

The purpose of this retrospective analysis was to report a single-institution long-term experience of 10-kHz SCS in patients who did not get adequate pain relief with prior t-SCS devices. A temporary trial of 10-kHz SCS was carried out for 7 days, and those experiencing an average of 50% reduction in pain intensity underwent implantation. Patients were classified as moderate responders if relief was 31% to 50% and excellent responders if pain relief exceeded 50%.

RESULTS

Thirty-one patients who had experienced failed t-SCS primarily from poor paresthesia coverage underwent a trial of 10-kHz SCS and 29 underwent implantation. Twenty-eight patients were available for analysis, with 57.1% experiencing 30% response and 46.4% experiencing excellent response at a median follow-up of 21.2 (±8.4) months.

CONCLUSIONS

This small single-institution study suggests that a significant proportion of patients with previously failed t-SCS may achieve clinically meaningful and durable pain relief with 10-kHz SCS.

Symptom reduction and improved function in chronic CRPS type 1 after 12-week integrated, interdisciplinary therapy

Background and aims Complex Regional Pain Syndrome (CRPS) often recovers spontaneously within the first year, but when it becomes chronic, available rehabilitative therapies (pharmacological management, physiotherapy, and psychological intervention) have limited effectiveness. This study examined the effect of a 12-week intensive outpatient rehabilitation on pain relief and function in chronic CRPS patients. Rehabilitation program included memantine and morphine treatment (added to patient's prior pain medication) and concurrent psychological and physiotherapeutic intervention. Primary outcome measure was a change in CRPS symptom count and secondary outcomes were motor performance, psychological factors, pain intensity, and quality of life. Methods Ten patients with chronic upper limb CRPS I (median 2.9 years, range 8 months to 12 years) were recruited to the study and were assessed before and after the intervention. Hand motor function of the patients was evaluated by an independent physiotherapist. There were standardized questionnaires for depression, pain anxiety, pain acceptance, quality of life, and CRPS symptom count. In addition, psychological factors were evaluated by a semi-structured interview. Severity of experienced pain was rated at movement and at rest. In addition, a video experiment of a hand action observation was conducted pre- and post-intervention to study possible change in neuronal maladaptation. Intervention consisted of pharmacological, psychological and physiotherapeutic treatment. First, 10 mg daily morphine was started and increased gradually to 30 mg daily, if tolerated. After 30 mg/day or tolerated dose of morphine was achieved, 5 mg daily memantine was started and increased gradually to 40 mg, if tolerated. Psychological intervention consisted of weekly group sessions, using cognitive and behavioral methods (relaxation, behavioral activation, and exposure) and acceptance and commitment therapy (ACT) and daily home practice. Physiotherapeutic intervention consisted of graded motor imagery and physiotherapy exercises with weekly group sessions and/or individual guidance by the physiotherapist, and individual exercise of the affected upper limb. Results Multimodal intensive intervention resulted in significant decrease in CRPS symptom count. The effect was strongest in motor and trophic symptoms (19% decrease after intervention) and in sensory symptoms (18% decrease). Additionally, improvement was seen in some, but not all, secondary outcomes (movement pain, motor symptoms, change in perceptions during video experiment of hand actions, and summary index with motor functioning, pain, and psychological factors). There were no dropouts. Conclusions Intensive 12-week multimodal intervention reduced some CRPS symptoms but was not sufficient to alter patients' rest pain, distress, or quality of life. Implications These results support the efficacy of an interdisciplinary rehabilitation program for pain and function in chronic CRPS patients. After intervention, some CRPS symptoms reduced and function improved, but distress and quality of life were unchanged. This may be due to the relatively short duration of this program; to delayed effects; to particular cognitive problems of CPRS patients; and/or to low distress levels at baseline that make statistically significant reduction less likely.

Psychological, social and biological correlates of body perception disturbance in complex regional pain syndrome

Body Perception Disturbance (BPD) in Complex Regional Pain Syndrome (CRPS) still represents a poorly understood phenomenon. Research has shown that knowledge about changes in body perception can yield relevant information for understanding and treating the disease. This study addressed possible connections between BPD and psychological and social factors, pain intensity, and disease duration. Sixty patients with chronic CRPS Type I of the hand were recruited. Body Perception Disturbance was assessed using the Galer and Jensen Neurobehavioral Questionnaire (GJ) and the BATH CRPS Body Perception Disturbance Scale (BATH). Depression, anxiety, stress, childhood trauma and other life events were assessed using standardized and validated questionnaires. This study found that BPD in CRPS was significantly correlated with measures of depression, anxiety, current stress, quality of life, and pain intensity, but not with stress experienced in the twelve months preceding onset of illness, childhood trauma, or duration of illness. Future research needs to identify which patients are most likely to develop these psychological conditions of CRPS, so that early, preventive intervention is possible. This study establishes a relationship between depression, anxiety, current stress, quality of life, pain intensity, and BPD severity. It also supports literature suggesting that preexisting stress, childhood trauma, and disease duration have no influence on BPD. The findings suggest that there is a bidirectional influence between brain alterations, psychological symptoms, and illness severity.

Commonalities and differences in abnormal peripheral metabolites between patients with fibromyalgia and complex regional pain syndrome

Background: Fibromyalgia (FM) and complex regional pain syndrome (CRPS) share many pathological mechanisms related to chronic pain that could contribute to multifactorial pathological mechanisms.Methods: We investigated peripheral metabolites in FM and CRPS patients compared to healthy controls based on cross-sectional study.Results: Mean corpuscular hemoglobin (p < 0.001), mean corpuscular volume (p = 0.014), and total bilirubin levels (p = 0.017) were lower in FM patients than in healthy controls. On the other hand, CRPS patients showed lower levels of total bilirubin than healthy controls (p = 0.037). Creatinine level was lower in FM patients (p = 0.057) compared to healthy controls, particularly when comparing the low-hemoglobin subgroup among FM patients (p = 0.035) with the low-hemoglobin subgroup among healthy controls. Red blood cell count (r = -0.620, p = 0.031), hematocrit (r = -0.593, p = 0.042), and creatinine level (r = -0.598, p = 0.040) showed negative correlations with McGill Pain Questionnaire-Affective (MPQ-A) scores in FM patients. A negative correlation was observed between MCV and McGill Pain Questionnaire-Sensory scores (r = -0.680, p = 0.015) in CRPS patients.Conclusion: We found specific peripheral metabolites that may exhibit different tendency between FM and CRPS patients as well as some common metabolites, which may be associated with peripheral pathology in the patients. Considering this study had a few limitations such as a small sample sizes and using a liberal threshold of significance in the correlation analysis, future studies with larger sample sizes may be needed to generalize these findings.

Complex regional pain syndrome following a centipede bite: a case report

Context: Complex Regional Pain Syndrome (CRPS) is a chronic neuropathic pain condition associated with autonomic features. To date, the development of CRPS following centipede bite has not been reported. We report a case of CRPS likely secondary to a centipede bite.Case details: A 31-year-old female was bitten by a centipede on the right 2nd toe. She was initially treated with analgesics, and two weeks later developed severe pain, allodynia, pruritus, and edema of the right foot, with hyperpigmentation over the affected toe. The X-ray, ultrasound, electromyography, nerve conduction velocity studies of the foot, blood chemistries, and erythrocyte sedimentation rate showed no abnormalities. The patient was diagnosed with CRPS type 1 by fulfilling the Budapest criteria. She was treated with gabapentin, amitriptyline, desloratadine, and fluoxetine, along with physical rehabilitation. Clinical symptoms gradually improved, and resolved at approximately 9 months with persistent hyperpigmentation.Discussion: Centipede bite may be an eliciting event for CRPS. It is unknown whether direct bite trauma or envenomation was the primary etiology in this case. Awareness of this condition is important for early diagnosis and appropriate management.

Fibromyalgia as a Predictor of Complex Regional Pain Syndrome After Distal Radius Fracture

Background: Complex regional pain syndrome (CRPS) can be a devastating complication following extremity injury, but risk factors are not well understood. The purpose of this study was to investigate the association between fibromyalgia and the development of CRPS after distal radius fracture. Methods: The PearlDiver Medicare database was queried using International Classification of Diseases, 9th Revision (ICD-9) and Current Procedural Terminology (CPT) codes for diagnoses and treatments of distal radius fractures. Patients were separated into fibromyalgia and control cohorts, and the prevalence of CRPS was measured at 3, 6, 9, and 12 months from the date of injury or procedure. Demographic factors, treatment modality, and comorbid conditions were analyzed by multivariable logistic regression to reduce confounding and identify additional risk factors. Results: Database queries yielded 853 186 patients diagnosed or treated for distal radius fracture, with 6% having previous diagnosis of fibromyalgia. The prevalence of CRPS following distal radius fracture was increased at 3, 6, 9, and 12 months in the fibromyalgia cohort compared with the control c, with a 1-year incidence of 0.51% compared with 0.20% (odds ratio [OR], 2.54, P < .001). Multivariable logistic regression supported the association, with estimated OR of 2.0 (P < .001). In addition, female gender, surgical or manipulative treatment, and anxiety were positively associated with CRPS, and age >65, diabetes, and heart failure were negatively associated. Conclusions: While the basis of the association between fibromyalgia and CRPS is unknown, our data suggest that it could serve as a useful predictor of CRPS risk, promoting increased vigilance for CRPS symptoms and earlier recognition and treatment, thereby improving patient outcomes.

Clinical Course and Impact of Complex Regional Pain Syndrome Confined to the Knee

OBJECTIVE

Although complex regional pain syndrome (CRPS) of the knee is comparable to CRPS of the ankle/foot at time of diagnosis, no reports are available concerning the course of knee CRPS. Therefore, this study investigated the clinical course in terms of the symptoms and signs, health-related quality of life (HR-QoL), and work status of patients diagnosed with CRPS of the knee.

DESIGN

Observational, descriptive study.

SETTING

Single-center study.

SUBJECTS

Patients with CRPS of the knee.

METHODS

Patients self-reported their past and current CRPS symptoms, HR-QoL, and work status; all underwent a physical examination. A comparison was made of changes in symptoms over time between patients with CRPS of the knee and those with CRPS of more distal locations.

RESULTS

In total, 32 patients were enrolled. The follow-up time was 11.5 ± 6.29 years since diagnosis, and symptoms and signs showed a significant decrease over time. Twelve patients (37.5%) rated their health as (generally) positive. Patients who were still able to work (31.3%) stated that their physical health gave them at least some problems in the performance of their job. A change in symptoms occurred significantly less often in CRPS of the knee.

CONCLUSIONS

CRPS of the knee changes in terms of symptoms over time, but significantly less than CRPS of other locations. A change in work status was reported in 82% of the patients due to their CRPS, and in 91%, the pain interfered with their daily life. CRPS of the knee is a painful condition with persistent symptoms causing a diminished HR-QoL.

Comparison of complex regional pain syndrome and fibromyalgia: Differences in beta and gamma bands on quantitative electroencephalography

Complex regional pain syndrome (CRPS) and fibromyalgia (FM) share many features. Both can cause severe pain and are considered to have a mechanism of action, including dysfunction of the sympathetic nervous system. However, they have clinical differences in pain range and degree. The present study aimed to find neurophysiologic differences between CRPS and FM using quantitative electroencephalography (QEEG). Thirty-eight patients with CRPS and 33 patients with FM were included in the analysis. Resting-state QEEG data were grouped into frontal, central, and posterior regions to analyze for regional differences. General linear models were utilized to test for group differences in absolute and relative powers. As a result, the CRPS group relative to FM group showed lower total absolute powers in the beta band (F = 5.159, P < .05), high beta (F = 14.120, P < .05), and gamma band (F = 15.034, P < .05). There were no significant differences between 2 groups in the delta, theta, and alpha bands. The present findings show that the CRPS and FM groups differ mainly in the high frequency, which may reflect their distinct pathophysiology and symptomatology. Our study suggests that the QEEG differences can be clinically useful in assessing brain function in patients with CRPS and FM.

The Role of the Peripheral Nerve Surgeon in the Treatment of Pain

Pain is a frequent cause of physician visits. Many physicians find these patients challenging because they often have complicated histories, emotional comorbidities, confusing examinations, difficult problems to fix, and the possibility of factitious complaints for attention or narcotic pain medications. As a result, many patients are lumped into the category of chronic, centralized pain and relegated to pain management. However, recent literature suggests that surgical management of carefully diagnosed generators of pain can greatly reduce patients' pain and narcotic requirements. This article reviews recent literature on surgical management of pain and four specific sources of chronic pain amenable to surgical treatment: painful neuroma, nerve compression, myofascial/musculoskeletal pain, and complex regional pain syndrome type II.

Spinal epidural abscess associated with an epidural catheter in a woman with complex regional pain syndrome and selective IgG3 deficiency: A case report

RATIONALE

Continuous epidural infusion of local anesthetic may be an alternative to sympathetic blocks in refractory cases of complex regional pain syndrome (CRPS). Spinal epidural abscess (SEA) is a well-known complication associated with this technique, especially in patients with immune deficiencies. We herewith report a cervical SEA associated with an epidural catheter in a woman with CRPS and selective IgG3 subclass deficiency.

PATIENT CONCERNS

Severe pain interfering with activities of daily living.

DIAGNOSIS

Complex regional pain syndrome type-1 with involvement of upper extremity.

INTERVENTIONS

The patient underwent inpatient epidural infusion for management of left upper extremity CRPS. Her history was notable for previous left shoulder injury requiring numerous surgical revisions complicated by recurrent shoulder infections, and selective IgG3 deficiency. She received antibiotic prophylaxis and underwent placement of a C6-C7 epidural catheter. On day 5, she became febrile. Neurological examination remained unchanged and an MRI demonstrated acute fluid collection from C3-T1. The following day she developed left arm weakness and was taken for emergent cervical decompression. Intraoperative abscess cultures were positive for Pseudomonas aeruginosa.

OUTCOMES

Postoperatively, the patient's neurological symptoms and signs improved.

LESSONS

Patients with selective IgG3 deficiency who are being considered for epidural catheterization may benefit from expert consultation with infectious diseases specialist. A history of recurrent device- or tissue-related infections should alert the clinician to the possible presence of a biofilm or dormant bacterial colonization. Close monitoring in an ICU setting during therapy is recommended. In case of early signs of infection, clinicians should have a high suspicion to rule out a SEA in immunocompromised patients.

Autoinflammatory and autoimmune contributions to complex regional pain syndrome

Complex regional pain syndrome (CRPS) is a highly enigmatic syndrome typically developing after injury or surgery to a limb. Severe pain and disability are common among those with chronic forms of this condition. Accumulating evidence suggests that CRPS may involve both autoinflammatory and autoimmune components. In this review article, evidence for dysfunction of both the innate and adaptive immune systems in CRPS is presented. Findings from human studies in which cytokines and other inflammatory mediators were measured in the skin of affected limbs are discussed. Additional results from studies of mediator levels in animal models are evaluated in this context. Similarly, the evidence from human, animal, and translational studies of the production of autoantibodies and the potential targets of those antibodies is reviewed. Compelling evidence of autoinflammation in skin and muscle of the affected limb has been collected from CRPS patients and laboratory animals. Cytokines including IL-1β, IL-6, TNFα, and others are reliably identified during the acute phases of the syndrome. More recently, autoimmune contributions have been suggested by the discovery of self-directed pain-promoting IgG and IgM antibodies in CRPS patients and model animals. Both the autoimmune and the autoinflammatory components of CRPS appear to be regulated by neuropeptide-containing peripheral nerve fibers and the sympathetic nervous system. While CRPS displays a complex neuroimmunological pathogenesis, therapeutic interventions could be designed targeting autoinflammation, autoimmunity, or the neural support for these phenomena.

miR-34a-mediated regulation of XIST in female cells under inflammation

Background

Evidence is overwhelming for sex differences in pain, with women representing the majority of the chronic pain patient population. There is a need to explore novel avenues to elucidate this sex bias in the development of chronic inflammatory pain conditions. Complex regional pain syndrome (CRPS) is a chronic neuropathic pain disorder, and the incidence of CRPS is greater in women than in men by ~4:1. Since neurogenic inflammation is a key feature of CRPS, dysregulation of inflammatory responses can be a factor in predisposing women to chronic pain.

Methods

Our studies investigating alterations in circulating microRNAs (miRNAs) in whole blood from female CRPS patients showed significant differential expression of miRNAs between responders and poor responders to ketamine treatment. Several of these miRNAs are predicted to target the long noncoding RNA, X-inactive-specific transcript (XIST). XIST mediates X-chromosome inactivation and is essential for equalizing the expression of X-linked genes between females and males. Based on the well-established role in inflammatory process, we focused on miR-34a, one of the miRNAs predicted to target XIST, and downregulated in CRPS patients responding poorly to ketamine.

Results

Our in vitro and in vivo models of acute inflammation and data from patients with CRPS showed that miR-34a can regulate XIST under inflammation directly, and through pro-inflammatory transcription factor Yin-Yang 1 (YY1). XIST was significantly upregulated in a subset of CRPS patients responding poorly to ketamine.

Conclusion

Since dysregulation of XIST can result in genes escaping inactivation or reactivation in female cells, further investigations on the role of XIST in the predominance of chronic inflammatory and pain disorders in women is warranted.

Subliminal (latent) processing of pain and its evolution to conscious awareness

By unconscious or covert processing of pain we refer to nascent interactions that affect the eventual deliverance of pain awareness. Thus, internal processes (viz., repeated nociceptive events, inflammatory kindling, reorganization of brain networks, genetic) or external processes (viz., environment, socioeconomic levels, modulation of epigenetic status) contribute to enhancing or inhibiting the presentation of pain awareness. Here we put forward the notion that for many patients, ongoing sub-conscious changes in brain function are significant players in the eventual manifestation of chronic pain. In this review, we provide clinical examples of nascent or what we term pre-pain processes and the neurobiological mechanisms of how these changes may contribute to pain, but also potential opportunities to define the process for early therapeutic interventions.

The Effect of Ketamine Infusion in the Treatment of Complex Regional Pain Syndrome: a Systemic Review and Meta-analysis

PURPOSE OF REVIEW

Complex regional pain syndrome (CRPS) is a painful debilitating neurological condition that accounts for approximately 1.2% of adult chronic pain population. Ketamine, an NMDA receptor antagonist, is an anesthetic agent that has been used by some pain specialists for CRPS. There is a growing body of clinical evidence to support the use of ketamine in the treatment of neuropathic pain, especially CRPS. This meta-analysis study was aimed to examine the efficacy of ketamine in the treatment of CRPS.

RECENT FINDINGS

A search of Embase, Pubmed, Web of Knowledge, Cochrane, Clinical Trial.gov , and FDA.gov between Jan 1, 1950, and August 1, 2017, was conducted to evaluate ketamine infusion therapy in the treatment of CRPS. We selected randomized clinical trials or cohort studies for meta-analyses. I 2 index estimates were calculated to test for variability and heterogeneity across the included studies. The primary outcome is pain relief. The effect of ketamine treatment for complex regional pain syndrome was assessed by 0-10 scale numerical rating pain score. The secondary outcome is the pain relief event rate, which is defined as the percentage of participants who achieved 30% or higher pain relief in each of the qualified studies. Our meta-analysis results showed that the Ketamine treatment led to a decreased mean of pain score in comparison to the self-controlled baseline (p < 0.000001). However, there is a statistical significance of between-study heterogeneity. The immediate pain relief event rate was 69% (95% confidence interval (CI) 53%, 84%). The pain relief event rate at the 1-3 months follow-ups was 58% (95% CI 41%, 75%). The current available studies regarding ketamine infusion for CRPS were reviewed, and meta-analyses were conducted to evaluate the efficacy of ketamine infusion in the treatment of CRPS. Our findings suggested that ketamine infusion can provide clinically effective pain relief in short term for less than 3 months. However, because of the high heterogeneity of the included studies and publication bias, additional random controlled trials and standardized multicenter studies are needed to confirm this conclusion. Furthermore, studies are needed to prove long-term efficacy of ketamine infusion in the treatment of CRPS.

Signs and Symptoms in 1,043 Patients with Complex Regional Pain Syndrome

Complex regional pain syndrome (CRPS) is a complex pain disorder that can emerge after limb trauma or a lesion in the peripheral nervous system. Typical features include continuing pain, sensory, vasomotor, sudomotor, motor, and trophic changes as well as edema. These signs provide the basis of CRPS diagnosis. A detailed description of the signs, symptoms, and medical history of CRPS could potentially facilitate an earlier and more accurate diagnosis. The aim of this study was to provide such a description, on the basis of epidemiological measures, clinical presentation, and a thorough description of pain sensations. Some signs (eg, differences of skin temperature >1°C), which have been thought to be crucial for diagnosis, were less common than assumed. We identified 11 distinct etiological triggers, which cover more than 99% of the study participants. We developed a weighted score on the basis of the most decisive data, which achieved a sensitivity of .869 and a specificity of .829, compared with .819 and .679 for the Budapest criteria. The weighted diagnostic criteria may help to better aid in distinguishing CRPS from other pain disorders.

PERSPECTIVE

This article provides a retrospective epidemiological analysis of 1,043 CRPS patients compared with 421 patients with other pain disorders. The findings could potentially facilitate a more reliable and earlier diagnosis of CRPS, a better differentiation from other pain disorders, and ultimately in a more targeted and effective therapy.

Recommendations for a first Core Outcome Measurement set for complex regional PAin syndrome Clinical sTudies (COMPACT)

Complex regional pain syndrome (CRPS) is a persistent pain condition that remains incompletely understood and challenging to treat. Historically, a wide range of different outcome measures have been used to capture the multidimensional nature of CRPS. This has been a significant limiting factor in the advancement of our understanding of the mechanisms and management of CRPS. In 2013, an international consortium of patients, clinicians, researchers, and industry representatives was established, to develop and agree on a minimum core set of standardised outcome measures for use in future CRPS clinical research, including but not limited to clinical trials within adult populations. The development of a core measurement set was informed through workshops and supplementary work, using an iterative consensus process. "What is the clinical presentation and course of CRPS, and what factors influence it?" was agreed as the most pertinent research question that our standardised set of patient-reported outcome measures should be selected to answer. The domains encompassing the key concepts necessary to answer the research question were agreed as follows: pain, disease severity, participation and physical function, emotional and psychological function, self-efficacy, catastrophizing, and patient's global impression of change. The final core measurement set included the optimum generic or condition-specific patient-reported questionnaire outcome measures, which captured the essence of each domain, and 1 clinician-reported outcome measure to capture the degree of severity of CRPS. The next step is to test the feasibility and acceptability of collecting outcome measure data using the core measurement set in the CRPS population internationally.

[Complex regional pain syndrome]

The term complex regional pain syndrome (CRPS) describes a variety of painful conditions, which typically occur distally on an extremity following an initiating event. Characteristically CRPS exceeds the expected clinical course in both magnitude and duration. Clinical manifestations of CRPS include sensory, vasomotor, sudomotor, motor and trophic disorders. The diagnosis of CRPS is purely clinical and based on the modified Budapest criteria. Essential differential diagnoses in the early phase include infections, neurological compression and inflammatory conditions. Although benign courses have been reported, many patients develop a chronic condition with persisting complaints even after 1 year. Therapy is based on a variety of pharmacological, interventional, physiotherapeutic, occupational and psychiatric treatment options.

Usefulness of bone scintigraphy for the diagnosis of Complex Regional Pain Syndrome 1: A systematic review and Bayesian meta-analysis

BACKGROUND

Since 2007, the Budapest criteria are recommended for the diagnosis of Complex Regional Pain Syndrome (CRPS) 1. The usefulness of bone scintigraphy (BS, index test) for the diagnosis of CRPS 1 remains controversial. Imperfect reference tests (RT) result in underestimation of the diagnostic accuracy of BS. Further, biased results can occur when a dependency between the RT and BS exists. The objective was to assess the impact of different RTs, specifically the Budapest criteria, and the assumed imperfect nature of the RT on the diagnostic accuracy of BS. Further, we analyzed the association between baseline characteristics and positive BS in patients with CRPS 1.

METHODS

Systematic literature review and Bayesian meta-analysis to assess the test accuracy of BS with and without accounting for the imperfect nature of the RT. We examined correlations (Spearman correlation coefficients / Wilcoxon tests) between baseline characteristics and the proportion of positive BS in patients with CRPS 1.

RESULTS

The pooled sensitivity was 0.804 (95% credible interval (CI) 0.225-1.0, 21 studies) and specificity 0.853 (95%CI 0.278-1.00). Sensitivity and specificity of BS increased when accounting for the imperfect nature of the RT. However, in studies using Budapest criteria as reference, the sensitivity decreased (0.551; 95% CI 0.046-1) and the specificity increased (0.935; 95% CI 0.306-1). Shorter disease duration and a higher proportion of males were associated with a higher proportion of positive BS (27 studies, disease duration <52 weeks Wilcoxon test p = 0.047, female proportion Spearman correlation -0.63, p = 0.009).

CONCLUSION

Compared to the accepted Budapest diagnostic criteria BS cannot be used to rule-in the diagnosis of CRPS 1. In patients with negative BS CRPS 1 is less likely the underlying illness. Studies using older or no diagnostic criteria should not be used to evaluate the diagnostic accuracy of BS in CRPS 1.

Physical therapy under hypnosis for the treatment of patients with type 1 complex regional pain syndrome of the hand and wrist: Retrospective study of 20 cases

Type 1 complex regional painful syndrome (CRPS-1) has a complex physiopathology. The aim of this study was to evaluate the effectiveness of physical therapy under hypnotherapy to treat this condition. Twenty patients with CRPS-1 at the wrist and hand were evaluated retrospectively: 13 women and 7 men with an average age of 56 years (34-75). Thirteen patients were in the inflammatory phase and 7 in the dystrophic phase. The main endpoints were pain (VAS, analgesic use), stiffness (wrist and finger range of motion), and strength (pinch and grasp). Secondary endpoints were functional scores (QuickDASH, PWRE), patient satisfaction, return to work, and side effects. Results were satisfactory in all cases after 5.4 sessions on average. VAS decreased by 4 points, PWRE-pain by 4.1 points, and analgesic use was limited to paracetamol upon request. Finger and wrist range of motion increased and the QuickDASH decreased by 34 points, PRWE-function by 3.8 points, pinch strength increased 4 points, and grasp strength by 10 points. Return to work was possible in 80% of the cases. All patients were satisfied or very satisfied with the treatment. Physical therapy under hypnosis appears to be an effective treatment for CRPS-1 at the wrist and hand no matter the etiology.

Identification and Treatment of New Inflammatory Triggers for Complex Regional Pain Syndrome: Small Intestinal Bacterial Overgrowth and Obstructive Sleep Apnea

Complex regional pain syndrome (CRPS) is evoked by conditions that may be associated with local and/or systemic inflammation. We present a case of long-standing CRPS in a patient with Ehlers-Danlos syndrome in which prolonged remission was attained by directing therapy toward concomitant small intestinal bacterial overgrowth, obstructive sleep apnea, and potential increased microglia activity. We theorize that cytokine production produced by small intestinal bacterial overgrowth and obstructive sleep apnea may act as stimuli for ongoing CRPS symptoms. CRPS may also benefit from the properties of low-dose naltrexone that blocks microglia Toll-like receptors and induces production of endorphins that regulate and reduce inflammation.

Complex regional pain syndrome: medical and legal ramifications of clinical variability and experience and perspective of a practicing clinician

Objective

The aim of this study was to demonstrate the ramifications of clinical variability of complex regional pain syndrome (CRPS) and how they can affect the various aspects of this condition, favorably or unfavorably, for both patients and participating medical and legal professionals.

Methods

Twelve patients diagnosed with CRPS at different times in the past 25 years were followed up, and their signs and symptoms were reviewed for variability. None had preexisting or ongoing medical disorders and prior injury to the peripheral nerves or musculoskeletal tissues. None had been involved in litigation. Physical traumas that triggered CRPS were job-related, vehicular accidents, and personal injuries. The presence of vasomotor symptoms (eg, swelling, skin discoloration, and temperature changes) and allodynia in the affected extremity was the basis for clinical diagnosis in all the patients. The need for imaging studies was precluded in some patients owing to the presence of vasomotor symptoms, which either fluctuated or were steady. Seven of the patients had type 1 CRPS, and five patients had type 2 CRPS.

Results

Most patients encountered delay in diagnosis and treatment and legal obstacles owing to the lack of “typical” objective signs of CRPS. The patients’ symptoms fluctuated at different times of the day. Eight patients experienced spread of vasomotor symptoms and varying degree of allodynia in the opposite extremity. One patient, who developed signs and symptoms of rheumatoid arthritis, 2 months after the injury, continued to have CRPS symptoms in the injured hand. Treatment modalities administered in all the patients were essentially ineffective. All the patients, except one, were unable to return to their original line of work, and their symptoms persisted regardless of the outcome of their legal claims.

Conclusion

It is likely that patients who continue to complain of pain and vasomotor symptoms followed by a physical injury have CRPS. The complex interaction between the peripheral, autonomic, and central nervous system in this condition makes it challenging to diagnose, treat, and prognosticate.

Analysis of medical disputes regarding chronic pain management in the 2009-2016 period using the Korean Society of Anesthesiologists database

Background

The active involvement of anesthesiologists in chronic pain management has been associated with an increase in the number of related medical dispute cases.

Methods

Using the Korean Society of Anesthesiologists Legislation Committee database covering case files from July 2009 to June 2016, we explored injuries and liability characteristics in a subset of cases involving chronic pain management.

Results

During the study period, 58 cases were eligible for final analysis. There were 27 cases related to complex regional pain syndrome (CRPS), many of them involving problems with financial compensation (24/27, 88.9%). The CRPS cases showed male dominance (22 males, 5 females). In a disproportionately large number of these cases, the causative injury occurred during military training (n = 5). Two cases were associated with noninvasive pain managements, and 29 cases with invasive procedures. Of the latter group, procedures involving the spine (both neuraxial and non-neuraxial procedures) resulted in more severe complications than other procedures (P = 0.007). Seven of the patients who underwent invasive procedures died. The most common type of invasive procedures were lumbosacral procedures (16/29, 55.2%). More specifically, the most common damaging events were inadvertent intravascular or intrathecal injection of local anesthetics (n = 6).

Conclusions

Several characteristics of medical disputes related to chronic pain management were identified: the prevalence of injury benefit claims in CRPS patients, higher severity of complications in procedures performed at the spine or cervical region, and the preventability of inadvertent intravascular or intrathecal injection of local anesthetics.