Epidemiology of complex regional pain syndrome: a retrospective chart review of 134 patients

Hyperbaric Oxygen Therapy for Management of Complex Regional Pain Syndrome

OBJECTIVES

Complex regional pain syndrome remains a challenging condition characterized by severe, persistent pain and a variety of inflammatory and trophic symptoms. This study aimed to analyze the current literature to evaluate hyperbaric oxygen therapy (HBOT)'s efficacy in treating complex regional pain syndrome (CRPS), focusing on both sympathetically maintained pain (SMP) and sympathetically independent pain (SIP) subtypes.

METHODS

A comprehensive literature search was conducted in PubMed Clinical Queries using the MeSH term "Complex Regional Pain Syndromes" OR the keyword "CRPS" AND "Hyperbaric Oxygen Therapy" OR the keyword "HBOT." The selected publication types included a randomized controlled trial, a retrospective observational study, a comparative study, a retrospective case series, and case reports. The search was restricted to articles published in English between January 1994 and October 2024. The results from the search were used to compile this review. Patients were categorized into SMP, SIP, or indeterminate groups based on the presence of prior sympathetic nerve block history or disease duration.

RESULTS

Thirteen studies involving 280 participants were reviewed. Of the patients, 42.5% were categorized as SMP, 48.2% as SIP, and 9.3% as indeterminate. HBOT treatment ranged from 3 to 63 sessions, typically using 2.4 atmospheres absolute for 90 minutes. The results indicated significant symptom relief and functional improvement across both SMP and SIP subtypes, suggesting the broad efficacy of HBOT for CRPS management.

DISCUSSION

This review of the current literature suggests that HBOT may offer significant symptom relief, regardless of CRPS subtype or disease duration. HBOT's anti-inflammatory and neuroplasticity promoting properties make it a valuable noninvasive option for CRPS patients, potentially improving outcomes when combined with other therapeutic modalities. Further research is necessary to refine patient selection and optimize treatment protocols.

The Efficacy of Neuromodulation, Interventional Treatment and Unconventional Therapies in the Treatment of Complex Regional Pain Syndrome: A Systematic Review

Complex regional pain syndrome (CRPS) is a chronic debilitating multisystem neuropathic pain disorder. It is characterized by continuous pain, usually out of proportion to any known tissue injury, vasomotor changes, sudomotor or edema, and motor or trophic changes. The objective of this study is to assess the efficacy of neuromodulation, interventional, and unconventional treatments for CRPS. The primary focus is pain reduction, assessed through various scales, with secondary outcomes examining effects on autonomic, sensory, motor, and psychological aspects, and quality of life. PubMed, Cochrane Library, MDPI, and ScienceDirect databases were thoroughly searched using our detailed search strategy and relevant literature compiled. Articles were assessed using our eligibility criteria and quality appraisal tools. All types of study designs were considered. Initially, 463 articles were identified; after a thorough assessment, 23 articles comprising 2307 patients were shortlisted. Neuromodulation interventions, specifically Dorsal Root Ganglion (DRG) and Spinal Cord Stimulation (SCS) demonstrated statistically significant pain reduction (43-82% and up to 70%, respectively). Both modalities demonstrate improvement in secondary outcomes and quality of life. Interventional interventions, specifically nerve blockade ranging from sympathetic, stellate ganglion, and regional nerve blocks, all demonstrate varying levels of efficacy on measured pain and secondary outcomes. Unconventional: Botulinum toxin injections through multiple delivery systems demonstrated varying levels of efficacy in treating pain and improving secondary outcomes. In conclusion, DRG stimulation and SCS, nerve blockade, and botulinum toxin all display promise in alleviating symptoms of CRPS. Definite conclusions were not made due to a lack of clinical trial data, and longer multi-year follow-up is recommended.

Effect of Occupation-Based Intervention Using the ADOC-H Combined With Physical Function-Based Intervention on Patients With Distal Radius Fractures: A Retrospective Case-Control Study

Objectives

Occupation-based intervention (OBI) involves daily and meaningful activities for evaluation and intervention. Recently, the "aid for decision-making in occupation choice for hand" (ADOC-H) was developed to facilitate OBI in patients with hand injuries. We aimed to examine the efficacy of OBI using the ADOC-H combined with physical function-based interventions (PBI) for patients with distal radius fractures (DRF).

Material and methods

Patients with DRF were retrospectively allocated to two groups, ADOC-H group (n = 14) and PBI group (n = 14), and compared.

Results

Improvements in the Pain Catastrophizing Scale magnification and Hospital Anxiety and Depression Scale and Disabilities of the Arm, Shoulder, and Hand questionnaire scores were significantly higher in the ADOC-H group than in the PBI group (p < .05). The groups showed no differences in measure of physical function, such as range of motion and grip strength.

Conclusion

OBI using the ADOC-H combined with PBI is clinically useful for patients with DRF as it promotes use of the injured hand for daily activities in a step-by-step approach, improving psychological difficulties in using the hand.

COVID-19 Vaccination-related Complex Regional Pain Syndrome Masquerading as Erythromelalgia: A Case Report

Abstract is missing (Short communication)

The Classic Three-Month Post-Operative Adaptation Phase in Foot and Ankle Surgery-An Expert Perspective

Foot and ankle disorders are a common reason for orthopedic surgical intervention. After surgery, specific precautions such as partial weight bearing or complete unloading, and the use of walking aids, coupled with a period of rest, are usually implemented to ensure the surgical outcome. However, when these aids are discontinued and the patients resume load increase and normal daily activities, they may enter a transitional phase characterized by inflammation, swelling, and pain. We call this phenomenon the "classic three-month post-operative adaptation phase" (POAP). It is essential to differentiate this physiological transition phase from other conditions, such as from the immediate post-surgical inflammation, complex pain regional syndrome, or an infection. The objective of this expert opinion is to describe and raise medical awareness of this evidence-based phenomenon, which we commonly observe in our daily practice.

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.

Comparison of Epidemiological Data of Complex Regional Pain Syndrome (CRPS) Patients in Relation to Disease Severity-A Retrospective Single-Center Study

A retrospective data analysis of 159 complex regional pain syndrome (CRPS) patients (n = 116 women, 73.0%, mean age 60.9 ± 14.4 years; n = 43 men, 27.0%, mean age 52.3 ± 16.7 years) was performed from 2009 to 2020. The right side was affected in 74 patients (46.5%), the left in 84 patients (52.8%), and 1 patient (0.7%) developed a bilateral CRPS. Data were analyzed for the frequency and distribution of symptoms. The number of reduction maneuvers and the number of Budapest criteria were compared in relation to the severity of CRPS. Hand and wrist (n = 107, 67.3%), followed by foot and ankle (n = 36, 22.6%) and other locations (n = 16, 10.1%) were mainly affected by CRPS. The main causes included direct trauma (n = 120, 75.5%), surgery without previous trauma (n = 25, 15.7%), other causes (n = 9, 5.7%), and spontaneous development (n = 3, 1.9%); there was also missing documentation (n = 2, 1.3%). The most common symptoms were difference in temperature (n = 156, 98.1%), limitation of movement (n = 149, 93.7%), and swelling (n = 146, 91.8%). There was no correlation between the number of reduction maneuvers and the number of Budapest criteria. In summary, patients with the following constellation are at increased risk of CRPS: a female, over 60 years old, who has fallen and has sustained a fracture in the hand or wrist with persistent pain and has been immobilized with a cast for approx. 4 weeks.

Altered bodily perceptions in chronic neuropathic pain conditions and implications for treatment using immersive virtual reality

Chronic neuropathic pain is highly disabling and difficult to treat and manage. Patients with such conditions often report altered bodily perceptions that are thought to be associated with maladaptive structural and functional alterations in the somatosensory cortex. Manipulating these altered perceptions using body illusions in virtual reality is being investigated and may have positive clinical implications for the treatment of these conditions. Here, we have conducted a narrative review of the evidence for the types of bodily distortions associated with a variety of peripheral and central neuropathic pain conditions. In addition, we summarize the experimental and clinical studies that have explored embodiment and body transformation illusions in immersive virtual reality for neuropathic pain relief, which are thought to target these maladaptive changes, as well as suggesting directions for future research.

Management of patients with neuropathic pain

Background: Neuropathic pain diseases commonly treated with pain medicine are postherpetic neuralgia (PHN), diabetic peripheral neuropathy (DPNP), complex regional pain syndrome (CRPS), and chronic pain after spinal surgery. Diagnosis and treatment of these neuropathic pain diseases is an arduous task, and there is a need to improve the understanding of these entities.Current Concepts: PHN is diagnosed when pain persists for more than 3 months after the healing of herpes zoster rashes, and this disease is commonly encountered in the elderly population. The pathophysiology of DPNP is ischemia of nerve tissue due to microvascular damage. In addition to sensory nerves, DPNP can also result in changes in motor and autonomic nerves. CRPS is a chronic intractable pain disorder, and is classified into types 1 and 2. Type 1 CRPS is diagnosed when there is no evidence of nerve damage while type 2 CRPS shows evidence of nerve damage. However, the signs and symptoms do not differ depending on the type. Chronic pain after spinal surgery is characterized by persistent back pain even after one or more spinal surgeries. This neuropathic pain occurs in the lower back or leg region.Discussion and Conclusion: The most crucial step in the management of patients with neuropathic pain is to suspect and diagnose if the pain has the characteristics of any pain-related disease. Although the etiology and pathophysiology may differ, the treatment of neuropathic pain remains the same and includes both conservative and interventional approaches. Neuropathic pain diseases often become chronic in nature, and thus, it is important to establish a treatment plan which aims at decreasing pain, improving patient’s functionality and attaining an acceptable quality of life.

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.

Vitamin C prevention of complex regional pain syndrome after foot and ankle surgery: a prospective randomized study of three hundred and twenty nine patients

PURPOSE

Complex regional pain syndrome (CRPS) after foot and ankle surgery has a significant impact on the ability to walk. As the symptomatic treatment of this disaster complication is poor and has low efficacy, a preventive treatment would be beneficial. Vitamin C has been reported to be efficient in preventing CRPS in elective scheduled surgery. Few authors explored this efficiency in foot and ankle surgery. We, therefore, evaluated the efficacy of vitamin C in preventing this complication after foot and ankle surgeries for both trauma and elective surgery.

MATERIAL AND METHODS

Between January 2018 and December 2019, 329 patients were included in the study. We conducted a prospective randomized study on the efficiency of vitamin C (one group with and one without vitamin C) to prevent CRPS risk in patients operated in our institution on foot or ankle surgery. The incidence of CRPS after foot and ankle surgery was evaluated in both groups; the diagnostic of CRPS was made using the Budapest criteria associated with three-phase bone scintigraphy.

RESULTS

Among the 329 patients included in the study (232 women and 97 men), 121 patients were included in the vitamin C group and 208 in the control group (without vitamin C). Vitamin C was statistically linked with a decreased risk of CRPS (OR 0.19; CI 95% from 0.05 to 0.8; p = 0.021). Alcoholism and cast immobilization were increased risks factors of CRPS (respectively p = 0.001 and p = 0.034).

CONCLUSION

Taking 1 g per day of vitamin C during 40 days after a foot or ankle surgery reduces the risk of CRPS.

A Korean nationwide investigation of the national trend of complex regional pain syndrome vis-à-vis age-structural transformations

Background

The present study employed National Health Insurance Data to explore complex regional pain syndrome (CRPS) updated epidemiology in a Korean context.

Methods

A CRPS cohort for the period 2009-2016 was created based on Korean Standard Classification of Diseases codes alongside the national registry. The general CRPS incidence rate and the yearly incidence rate trend for every CRPS type were respectively the primary and secondary outcomes. Among the analyzed risk factors were age, sex, region, and hospital level for the yearly trend of the incidence rate for every CRPS. Statistical analysis was performed via the chi-square test and the linear and logistic linear regression tests.

Results

Over the research period, the number of registered patients was 122,210. The general CRPS incidence rate was 15.83 per 100,000, with 19.5 for type 1 and 12.1 for type 2. The condition exhibited a declining trend according to its overall occurrence, particularly in the case of type 2 (P < 0.001). On the other hand, registration was more pervasive among type 1 compared to type 2 patients (61.7% vs. 38.3%), while both types affected female individuals to a greater extent. Regarding age, individuals older than 60 years of age were associated with the highest prevalence in both types, regardless of sex (P < 0.001).

Conclusions

CRPS displayed an overall incidence of 15.83 per 100,000 in Korea and a declining trend for every age group which showed a negative association with the aging shift phenomenon.

Quantitative Analysis of Real-Time Infrared Thermography for the Assessment of Lumbar Sympathetic Blocks: A Preliminary Study

Lumbar sympathetic blocks (LSBs) are commonly performed to treat pain ailments in the lower limbs. LSBs involve injecting local anesthetic around the nerves. The injection is guided by fluoroscopy which is sometimes considered to be insufficiently accurate. The main aim was to analyze the plantar foot skin temperature data acquired while performing LSBs in patients with complex regional pain syndrome (CRPS) affecting the lower limbs. Forty-four LSBs for treating lower limb CRPS in 13 patients were assessed. Pain medicine physicians visualized the infrared thermography (IRT) video in real time and classified the performance depending on the observed thermal changes within the first 4 min. Thirty-two percent of the cases did not register temperature variations after lidocaine was injected, requiring the needle to be relocated. Differences between moments are indicated using the 95% confidence intervals of the differences (CI 95%), the Cohen effect size (ES) and the significance (p value). In successful cases, after injecting lidocaine, increases at minute 7 for the mean (CI 95% (1.4, 2.1 °C), p < 0.001 and ES = 0.5), at minute 5 for maximum temperature (CI 95% (2.3, 3.3 °C), p < 0.001 and ES = 0.6) and at minute 6 for SD (CI 95% (0.2, 0.3 °C), p < 0.001 and ES = 0.5) were observed. The results of our preliminary study showed that the measurement of skin temperature in real time by infrared thermography is valuable for assessing the success of lumbar sympathetic blocks.

Autoimmune regulation of chronic pain

Chronic pain is an unpleasant and debilitating condition that is often poorly managed by existing therapeutics. Reciprocal interactions between the nervous system and the immune system have been recognized as playing an essential role in the initiation and maintenance of pain. In this review, we discuss how neuroimmune signaling can contribute to peripheral and central sensitization and promote chronic pain through various autoimmune mechanisms. These pathogenic autoimmune mechanisms involve the production and release of autoreactive antibodies from B cells. Autoantibodies-ie, antibodies that recognize self-antigens-have been identified as potential molecules that can modulate the function of nociceptive neurons and thereby induce persistent pain. Autoantibodies can influence neuronal excitability by activating the complement pathway; by directly signaling at sensory neurons expressing Fc gamma receptors, the receptors for the Fc fragment of immunoglobulin G immune complexes; or by binding and disrupting ion channels expressed by nociceptors. Using examples primarily from rheumatoid arthritis, complex regional pain syndrome, and channelopathies from potassium channel complex autoimmunity, we suggest that autoantibody signaling at the central nervous system has therapeutic implications for designing novel disease-modifying treatments for chronic pain.

The superoxide scavenger tempol attenuates DNA oxidative injury and spontaneous pain-like behavior in chronic post-cast pain model rats

The mechanism of severe pain occurring because of physical disuse, such as complex regional pain syndrome Type I, has not been elucidated so far. Therefore, to investigate this mechanism, we have developed a model called a chronic post-cast pain (CPCP) model. Oxidative stress-related factors generated in a fixed limb may be triggers for nociceptive signals due to physical disuse. On the basis of the results of our previous studies, we speculated that oxidative stress-related factors in immobilized hind limbs may also be triggers of nociceptive signals due to physical disuse. In this study, we aimed to clarify whether an oxidative stress-related factor is involved in the induction of nociceptive signals. The time course of oxidative damage in the soleus (slow-twitch fiber) and gastrocnemius (fast-twitch fiber) muscles was evaluated by immunostaining of 8-hydroxy-2'-deoxyguanosine (a marker of oxidative damage in DNA). We also investigated the effects of tempol, a scavenger of superoxide, on oxidative damage in DNA, spontaneous pain-related behaviors (licking and/or biting and flinching), and the activation of spinal dorsal horn neurons (c-Fos). Systemic administration of tempol before cast removal attenuated oxidative damage to DNA in immobilized skeletal muscles, suppressed spontaneous pain-related behavior, and suppressed the activation of spinal dorsal horn neurons. We suggest that superoxide generated in immobilized skeletal muscles after cast removal is one of the peripheral factors that trigger nociceptive signals.

Effects of cyclic stretching exercise on long-lasting hyperalgesia, joint contracture, and muscle injury following cast immobilization in rats

The effects of exercise on mechanical hyperalgesia, joint contracture, and muscle injury resulting from immobilization are not completely understood. This study aimed to investigate the effects of cyclic stretching on these parameters in a rat model of chronic post-cast pain (CPCP). Seventeen 8-week-old Wistar rats were randomly assigned to (1) control group, (2) immobilization (CPCP) group, or (3) immobilization and stretching exercise (CPCP+STR) group. In the CPCP and CPCP+STR groups, both hindlimbs of each rat were immobilized in full plantar flexion with a plaster cast for a 4-week period. In the CPCP+STR group, cyclic stretching exercise was performed 6 days/week for 2 weeks, beginning immediately after cast removal prior to reloading. Although mechanical hyperalgesia in the plantar skin and calf muscle, ankle joint contracture, and gastrocnemius muscle injury were observed in both immobilized groups, these changes were significantly less severe in the CPCP+STR group than in the CPCP group. These results clearly demonstrate the beneficial effect of cyclic stretching exercises on widespread mechanical hyperalgesia, joint contracture, and muscle injury in a rat model of CPCP.

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.

Physical disuse contributes to widespread chronic mechanical hyperalgesia, tactile allodynia, and cold allodynia through neurogenic inflammation and spino-parabrachio-amygdaloid pathway activation

Physical disuse could lead to a state of chronic pain typified by complex regional pain syndrome type I due to fear of pain through movement (kinesiophobia) or inappropriate resting procedures. However, the mechanisms by which physical disuse is associated with acute/chronic pain and other pathological signs remain unresolved. We have previously reported that inflammatory signs, contractures, disuse muscle atrophy, spontaneous pain-like behaviors, and chronic widespread mechanical hyperalgesia based on central plasticity occurred after 2 weeks of cast immobilization in chronic post-cast pain (CPCP) rat model. In this study, we also demonstrated dystrophy-like changes, both peripheral nociceptive signals and activation of the central pain pathway in CPCP rats. This was done by the following methods: (1) vascular permeability (Evans blue dye) and inflammatory- and oxidative stress-related messenger RNA changes (real-time quantitative polymerase chain reaction); (2) immunofluorescence of pERK and/or c-Fos expression in the spino-parabrachio-amygdaloid pathway; and (3) blockade of nociceptive-related signals using sciatic nerve block. Furthermore, we demonstrated tactile allodynia using an optogenetic method in a transgenic rat line (W-TChR2V4), cold allodynia using the acetone test, and activation of dorsal horn neurons in the chronic phase associated with chronic mechanical hyperalgesia using c-Fos immunofluorescence. In addition, we showed that nociceptive signals in the acute phase are involved in chronic pathological pain-like behaviors by studying the effects of sciatic nerve block. Thus, we conclude that physical disuse contributes to dystrophy-like changes, spontaneous pain-like behavior, and chronic widespread pathological pain-like behaviors in CPCP rats after 2 weeks of cast immobilization.

The Case for Comorbid Myofascial Pain-A Qualitative Review

Myofascial pain syndrome is widely considered to be among the most prevalent pain conditions, both in the community and in specialized pain clinics. While myofascial pain often arises in otherwise healthy individuals, evidence is mounting that its prevalence may be even higher in individuals with various comorbidities. Comorbid myofascial pain has been observed in a wide variety of medical conditions, including malignant tumors, osteoarthritis, neurological conditions, and mental health conditions. Here, we review the evidence of comorbid myofascial pain and discuss the diagnostic and therapeutic implications of its recognition.

Autoantibodies against P29ING4 are associated with complex regional pain syndrome

INTRODUCTION

Complex regional pain syndrome (CRPS) is a complication following trauma or surgery and may be difficult to diagnose since biomarkers are lacking. Using protein array technology, we found antibodies binding to p29ING4, which we further characterized using ELISA.

METHODS

Thirty-six sera of early-stage type 1 CRPS, 66 sera of rheumatoid arthritis (RA), 53 sera of axial spondyloarthritis (axSpA), 29 sera of psoriatic arthritis (PsA), 22 sera of patients after radial fractures (trauma control), and 100 sera of blood donors (BD) were analyzed for anti-p29ING4. We established ELISAs with 7 different antigens and using different secondary antibodies binding to IgG, IgG1, IgG2, IgG3, IgG4, IgA, and IgM, and 2 different tests to detect immune complexes (IC) of p29ING4 and IgG or IgG1.

RESULTS

The highest likelihood ratios versus CRPS and trauma control were observed considering the A1-23 (sensitivity 19%, specificity 100%, LR > 19) using IgG as a secondary antibody, the A120-165 (sensitivity 17%, specificity 100%, LR = 17) using IgG as a secondary antibody and the A120-165 (sensitivity 31%, specificity 95%, LR = 6.2) using IgA as a secondary antibody. IC of p29ING4 and IgG were present in 11/36 (31%) CRPS sera, 17/64 (27%) RA sera, 13/53 (25%) SpA sera, 5/29 (17%) PsA sera, 1/22 (5%) trauma control sera, and 4/100 (4%) sera of BD. IC of p29ING4 and IgG1 were present in 14/36 (39%) CRPS sera, 19/64 (30%) RA sera, 13/53 (25%) SpA, 1/29 (3%) PsA, 2/22 (9%) trauma control, and 4/100 (4%) of the BD sera.

CONCLUSION

Due to the lack of other biomarkers of type 1 CRPS, P29ING4 autoantibodies could be helpful in its diagnostic work-up.

The effect of human mesenchymal stem cell injection on pain behavior in chronic post-ischemia pain mice

Background

Neuropathic pain (NP) is considered a clinically incurable condition despite various treatment options due to its diverse causes and complicated disease mechanisms. Since the early 2000s, multipotent human mesenchymal stem cells (hMSCs) have been used in the treatment of NP in animal models. However, the effects of hMSC injections have not been studied in chronic post-ischemia pain (CPIP) mice models. Here, we investigated whether intrathecal (IT) and intrapaw (IP) injections of hMSCs can reduce mechanical allodynia in CPIP model mice.

Methods

Seventeen CPIP C57/BL6 mice were selected and randomized into four groups: IT sham (n = 4), IT stem (n = 5), IP sham (n = 4), and IP stem (n = 4). Mice in the IT sham and IT stem groups received an injection of 5 μL saline and 2 × 10⁴ hMSCs, respectively, while mice in the IP sham and IP stem groups received an injection of 5 μL saline and 2 × 10⁵ hMSCs, respectively. Mechanical allodynia was assessed using von Frey filaments from pre-injection to 30 days post-injection. Glial fibrillary acidic protein (GFAP) expression in the spinal cord and dorsal root ganglia were also evaluated.

Results

IT and IP injections of hMSCs improved mechanical allodynia. GFAP expression was decreased on day 25 post-injection compared with the sham group. Injections of hMSCs improved allodynia and GFAP expression was decreased compared with the sham group.

Conclusions

These results suggested that hMSCs may be also another treatment modality in NP model by ischemia-reperfusion.

Complex regional pain syndrome in the young male population: a retrospective study of 200 Korean young male patients

Background

The aim of this study was to investigate the clinical characteristics of complex regional pain syndrome (CRPS) in young male patients in South Korea, especially focusing on the association with military service.

Methods

From January 2007 to May 2017, we investigated the electronic medical records of 430 consecutive patients, aged 18 to 30 years, who visited Seoul National University Hospital Pain Center, with a suspected diagnosis of CRPS at the initial visit. The following patient details were available for analysis: demographic and disease-related variables, relevance to military service, medications, and the treatment modalities received.

Results

Out of 430 patients, 245 (57.0%) were diagnosed with CRPS, of which, 200 were male patients and 45 were female patients. Of the male patients, 95 (47.5%) developed CRPS during military service. CRPS during military service was more likely to result from sprain/strain, and the incidence of CRPS was significantly higher in the lower extremities in patients from the military service group than in those from the non-military service group. During the follow-up period, 37.9% of male CRPS patients (n = 61/161) were treated successfully. Patients with moderate to severe initial pain intensity, and diagnosed during their military service, showed better outcomes.

Conclusions

Our results demonstrated that manifestation of CRPS in the young Korean population was more common in male and among those male CRPS patients, about half the cases developed during the military service period.

Visuo-tactile stimulation, but not type of movement, modulates pain during the vision of a moving virtual limb

Aim: Evidence has revealed a relationship between pain and the observation of limb movement, but it is unknown whether different types of movements have diverse modulating effects. In this immersive virtual reality study, we explored the effect of the vision of different virtual arm movements (arm vs wrist) on heat pain threshold of healthy participants. Patients & methods: 40 healthy participants underwent four conditions in virtual reality, while heat pain thresholds were measured. Visuo-tactile stimulation was used to attempt to modulate the feeling of virtual limb ownership while the participants kept their arms still. Results: Effects on pain threshold were present for type of stimulation but not type of movement. Conclusion: The type of observed movement does not appear to influence pain modulation, at least not during acute pain states.

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.

Does a familial subtype of complex regional pain syndrome exist? Results of a systematic review

Background and Objective: Complex regional pain syndrome (CRPS) is a chronic condition characterized by severe regional pain, allodynia, hyperalgesia, and functional impairment. The aim of this systematic review is to investigate whether a familial subtype of CRPS (fCRPS) exists and to determine whether people with fCRPS have specific characteristics.

Methods: Databases CINAHL, Medline, PsycINFO, and PubMed were searched with no date limitation. Quality of reporting was assessed using the Scottish Intercollegiate Guidelines Network scale and the Joanna Briggs Institute’s checklists.

Results: Eight studies were included. Family relationships were defined as any immediate (i.e., parents or siblings) or blood relatives. A combination of participants with known or unknown causes for CRPS was recruited. The studies in this review support the potential for the existence of fCRPS, although this included less than 25% of those affected. People with potential fCRPS showed more severe symptoms, more sites involved, a higher percentage of spontaneous onset, and earlier age at onset. An elevated sibling recurrence risk ratio of 5.6 (95% confidence interval [CI], 3.0 to 9.8) was reported for people under 50. None of the studies established a pattern of heritability. Therefore, the most likely explanation for heritability would be a multifactorial model in which cumulative and interactive Gene × Environment effects may be involved.

Conclusions: This systematic review supports the potential for the existence of fCRPS; however, all identified studies used uncontrolled case reports, case series, and case–control designs that cannot provide evidence of causation. Further studies are required to reveal the heritability and genetic structure of fCRPS.

Psychosocial factors associated with poor outcomes after amputation for complex regional pain syndrome type-I

Background

Amputation for longstanding therapy resistant complex regional pain syndrome type-I (CRPS-I) is controversial. Reported results are inconsistent. It is assumed that psychological factors play a role in CRPS-I.

Objective

To explore which psychological factors prior to amputation are associated with poor outcomes after amputation in the case of longstanding therapy resistant CRPS-I.

Methods

Between May 2008 and August 2015, 31 patients with longstanding therapy resistant CRPS-I were amputated. Before the amputation 11 psychological factors were assessed. In 2016, participants had a structured interview by telephone and filled out questionnaires to assess their outcome. In case of a perceived recurrence of CRPS-I a physician visited the patient to examine the symptoms. Associations between psychological factors and poor outcomes were analysed.

Results

Four of the 11 psychological factors were associated with poor outcomes. Regression analyses showed that change in the worst pain in the past week was associated with poor social support (B = 0.3, 95% confidence interval: 0.1;0.6) and intensity of pain before amputation (B = 2.0, 95% confidence interval 0.9;3.0). Patients who reported important improvements in mobility (n = 23) had significantly higher baseline resilience (median 79) compared to those (n = 8) who did not report it (median 69)(Mann-Whitney U, Z = -2.398, p = 0.015). Being involved in a lawsuit prior to amputation was associated with a recurrence in the residual limb (Bruehl criteria). A psychiatric history was associated with recurrence somewhere else (Bruehl criteria).

Conclusion

Poor outcomes of amputation in longstanding therapy resistant CPRS-1 are associated with psychological factors. Outstanding life events are not associated with poor outcome although half of the participants had experienced outstanding life events.

Proximal myofascial pain in patients with distal complex regional pain syndrome of the upper limb

BACKGROUND

Patients suffering from complex regional pain syndrome (CRPS) endure myofascial-related pain in at least 50% of cases.

AIMS

To evaluate the association of upper limb CRPS with myofascial pain in muscles that might influence arm or hand pain, and to evaluate whether the paraspinal skin and subcutaneous layers' tenderness and allodynia are associated with CRPS.

METHODS

A case-control study comprising 20 patients presenting with upper limb CRPS, and 20 healthy controls matched for sex and age, were evaluated in the thoracic paraspinal area and myofascial trigger points (MTrPs) (infraspinatus, rhomboids, subclavius, serratus posterior superior and pectoralis minor) via a skin rolling test.

RESULTS

The prevalence of MTrPs in the affected extremity of the subjects was significantly higher than in the right limb of the controls: 45% exhibited active and latent MTrPs in the infraspinatus muscle (χ² = 11.613, p = 0.001); 60% in active and latent MTrPs in the subclavius muscle (χ² = 17.143, p < 0.001); and in the pectoralis minor muscle (χ2 = 13.786, p < 0.001). In addition, 55% of the cases exhibited active and latent MTrPs in the serratus posterior superior muscle (χ² = 15.172, p < 0.001). Significant differences between the groups in skin texture and pain levels (p = 0.01, p < 0.001, respectively) demonstrated that CRPS patients felt more pain, and their skin and subcutaneous layers were much tighter than in the healthy controls.

CONCLUSION

There is a high prevalence of MTrPs in the shoulder and upper thoracic area muscles in subjects who suffer from CRPS. We recommend adding an MTrPs evaluation to the standardized examination of these patients.

Exercise Reverses Nociceptive Sensitization, Upregulated Neuropeptide Signaling, Inflammatory Changes, Anxiety, and Memory Impairment in a Mouse Tibia Fracture Model

WHAT WE ALREADY KNOW ABOUT THIS TOPIC

WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: This study tested the hypothesis that ad lib running wheel exercise in a tibia fracture model of complex regional pain syndrome can reverse hindlimb nociceptive sensitization and inflammation in mice.

METHODS

Three weeks after tibia fracture, the cast was removed and hindlimb von Frey thresholds and unweighting were tested; the mice were then randomized to either ad lib access to a running wheel for 4 weeks or no wheel access. After 4 weeks the behavioral testing was repeated and then skin, sciatic nerve, and spinal cord tissues collected for polymerase chain reaction and enzyme immunoassay measurements of neuropeptide and inflammatory mediator levels. A similar protocol was used in fracture mice treated with exercise for 4 weeks, and then the running wheel was removed for 2 weeks. Memory and anxiety were measured in both groups with use of open-field, zero-maze, and novel-objects recognition assays.

RESULTS

At 7 weeks postfracture the mice with no wheel access exhibited hindlimb allodynia and unweighting, anxiety, memory loss, upregulated spinal neuropeptide signaling, and increased hind paw and spinal inflammatory mediator expression, but the postfracture mice allowed to exercise for 4 weeks exhibited none of these changes (n = 12/cohort). When exercise was stopped for 2 weeks after 4 weeks of running, hindlimb allodynia and unweighting were rekindled, and this nociceptive sensitization was associated with increased sciatic nerve neuropeptide levels and hind paw skin interleukin 6 and nerve growth factor expression (n = 12/cohort).

CONCLUSIONS

Daily exercise reversed nociceptive sensitization, inflammation, anxiety, and memory loss after tibia fracture.

Sensory modulation dysfunction is associated with Complex Regional Pain Syndrome

OBJECTIVE

Complex Regional Pain Syndrome (CRPS), a chronic pain condition, develops mainly after limb trauma and severely inhibits function. While early diagnosis is essential, factors for CRPS onset are elusive. Therefore, identifying those at risk is crucial. Sensory modulation dysfunction (SMD), affects the capacity to regulate responses to sensory input in a graded and adaptive manner and was found associated with hyperalgesia in otherwise healthy individuals, suggestive of altered pain processing.

AIM

To test SMD as a potential risk factor for CRPS.

METHODS

In this cross-sectional study, forty-four individuals with CRPS (29.9±11 years, 27 men) and 204 healthy controls (27.4±3.7 years, 105 men) completed the Sensory Responsiveness Questionnaire-Intensity Scale (SRQ-IS). A physician conducted the CRPS Severity Score (CSS), testing individuals with CRPS.

RESULTS

Thirty-four percent of the individuals with CRPS and twelve percent of the healthy individuals were identified to have SMD (χ2 (1) = 11.95; p<0.001). Logistic regression modeling revealed that the risk of CRPS is 2.68 and 8.21 times higher in individuals with sensory over- and sensory under-responsiveness, respectively, compared to non-SMD individuals (p = 0.03 and p = 0.01, respectively).

CONCLUSIONS

SMD, particularly sensory under-responsiveness, might serve as a potential risk factor for CRPS and therefore screening for SMD is recommended. This study provides the risk index probability clinical tool a simple evaluation to be applied by clinicians in order to identify those at risk for CRPS immediately after injury. Further research is needed.

Epidemiology of complex regional pain syndrome in Korea: An electronic population health data study

Chronic regional pain syndrome (CRPS) is an inflammatory and neuropathic pain disorder characterized by the involvement of the autonomic nervous system with sensory, autonomic, motor, skin, and bone changes. At present, universally accepted consensus criteria for CRPS are not yet established, despite the diagnostic criteria proposed by the International Association for the Study of Pain (IASP). Various hypotheses for the pathophysiology of CRPS have been proposed; as a result, current therapeutic modalities are varied. General epidemiological data on CRPS are necessary for effective management. However, recent data on the epidemiology of CRPS in Korea are scarce. The aim of this study was to evaluate the incidence and other epidemiological features of CRPS in the general population in Korea. In this study on the epidemiology of CRPS in Korea, population-based medical data acquired from 51,448,491 subscribers to the National Health Insurance Service (NHIS) from 2011 to 2015 were analyzed, including the incidence, distribution by the CRPS type, regional distribution, monthly distribution, medical costs, and healthcare resource-utilization. The findings indicated that the incidence of CRPS in Korea was 29.0 per 100,000 person-years in 2015 and was correlated with patient age and sex. CRPS types included type I (63%) and type II (37%); moreover, the number of individuals with CRPS I have shown a growing trend since 2011. There was no monthly distribution, but there was regional variation according to the province. The medical departments managing CRPS I the most were orthopedics, internal medicine, anesthesiology and pain medicine, in order; however, patients with CRPS spent more money per visit in the departments of rehabilitation medicine, and anesthesiology and pain medicine. The incidence rate of CRPS in Korea was 29.0 per 100,000 person-years with an increasing trend, which was correlated with patient age in the 70s and female sex. CRPS type I was more common than CRPS type II; in addition, constant increase in medical expenses, regional imbalance, and differences in medical expense among medical specialties should be considered for early management of patients to reduce the disease burden in Korea. Sharing of knowledge about the diagnostic criteria of CRPS are also needed.

Healthcare Use Patterns and Economic Burden of Chronic Musculoskeletal Pain in Children before Diagnosis

OBJECTIVES

To evaluate the healthcare use and costs of amplified musculoskeletal pain syndrome (AMPS) in children before diagnosis.

STUDY DESIGN

We performed a retrospective study in children with AMPS at a pediatric rheumatology clinic between 2010 and 2014. Data were abstracted on 80 patients after primary rheumatic diseases were excluded. Healthcare visits, medications and diagnostic testing that occurred in the years before diagnosis were collected. The Medical Expenditure Panel Survey was used to estimate visit costs.

RESULTS

Patients were adolescent females (89%) and white (86%). The median time to diagnosis was 10.2 months. The median pain score was 6.5 and the median Childhood Health Assessment Questionnaire score was 1.1. In this cohort, 29% had at least 1 ED visit and 5% were hospitalized. All patients saw a rheumatologist and 41% had visited another specialist, typically orthopedics and sports medicine. More than one-half had at least 1 radiographic study and 21% had at least 1 magnetic resonance imaging. The total cost for office, emergency department, and hospital visits for AMPS in all 80 patients was $152 853. The mean cost per patient over the entire study period (2008-2014) was $1911 ± $3808, and 43% of costs were outpatient visits.

CONCLUSIONS

Children with AMPS have high levels of disability and take a long time to be diagnosed. As a result, even before diagnosis, they have high levels of healthcare use, diagnostic testing, and medical costs. Early recognition of disability and quicker referral to trained subspecialists may improve the prognosis, reduce unnecessary testing, and reduce the overall costs of healthcare.

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.

Selective Fiber Degeneration in the Peripheral Nerve of a Patient With Severe Complex Regional Pain Syndrome

Aims: Complex regional pain syndrome (CRPS) is characterized by chronic debilitating pain disproportional to the inciting event and accompanied by motor, sensory, and autonomic disturbances. The pathophysiology of CRPS remains elusive. An exceptional case of severe CRPS leading to forearm amputation provided the opportunity to examine nerve histopathological features of the peripheral nerves.

Methods: A 35-year-old female developed CRPS secondary to low voltage electrical injury. The CRPS was refractory to medical therapy and led to functional loss of the forelimb, repeated cutaneous wound infections leading to hospitalization. Specifically, the patient had exhausted a targeted conservative pain management programme prior to forearm amputation. Radial, median, and ulnar nerve specimens were obtained from the amputated limb and analyzed by light and transmission electron microscopy (TEM).

Results: All samples showed features of selective myelinated nerve fiber degeneration (47–58% of fibers) on electron microscopy. Degenerating myelinated fibers were significantly larger than healthy fibers (p < 0.05), and corresponded to the larger Aα fibers (motor/proprioception) whilst smaller Aδ (pain/temperature) fibers were spared. Groups of small unmyelinated C fibers (Remak bundles) also showed evidence of degeneration in all samples.

Conclusions: We are the first to show large fiber degeneration in CRPS using TEM. Degeneration of Aα fibers may lead to an imbalance in nerve signaling, inappropriately triggering the smaller healthy Aδ fibers, which transmit pain and temperature. These findings suggest peripheral nerve degeneration may play a key role in CRPS. Improved knowledge of pathogenesis will help develop more targeted treatments.

Therapeutic effects of diclofenac, pregabalin, and duloxetine on disuse-induced chronic musculoskeletal pain in rats

The aim of this study was to clarify the mechanism of disuse-induced muscle hyperalgesia through the evaluation of the pharmacological behaviour of muscle hyperalgesia profiles in chronic post-cast pain (CPCP) rats with acute and chronic-phase mirror-image muscle hyperalgesia treated with diclofenac (NSAID), pregabalin (an inhibitor of Ca²⁺ channel α2δ), and duloxetine (SNRI). After 2 weeks of cast immobilization, the peak cross-sectional area and muscle wet weight of the ipsilateral soleus and gastrocnemius muscles decreased more significantly in CPCP rats than in untreated rats. Histological findings revealed disuse-induced muscle atrophy in CPCP rats. The blood biochemical parameters of CPCP rats in acute and chronic phases did not differ significantly from those of untreated rats. The diclofenac and pregabalin-treated groups exhibited no improvement in acute or chronic muscle hyperalgesia. In contrast, the duloxetine-treated group exhibited an improvement in acute muscle hyperalgesia, but showed no apparent effect on chronic muscle hyperalgesia on ipsilateral or contralateral sides. However, the chronic muscle hyperalgesia was reversed by intrathecal administration of DAMGO (a μ-opioid receptor agonist). The results suggest that chronic muscle hyperalgesia in CPCP rats did not result from an inflammatory mechanism, and there is only a low probability that it's caused by a neuropathic mechanism.

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.

Evidence already exists for motor system reorganization in CRPS

Complex regional pain syndrome (CRPS) is a disabling condition that is usually preceded by trauma or surgical procedure. Involvement of the motor system is a well-known phenomenon in CRPS, though the pathophysiologic mechanisms of motor system affliction in CRPS are poorly understood. Graded motor imagery (GMI) has been proposed to be one of the therapeutic interventions to help improve pain and other disabling symptoms associated with CRPS, though the benefits noted are modest and inconsistent. The neurophysiological mechanisms implicated in motor imagery are intended to target the aberrant prefrontal and sensorimotor integration areas, which may potentially help restore the aberrant cortical plasticity in CRPS. Detailed well-controlled experiments using insights from the existing body of literature on motor system reorganization in CRPS are required to better understand this complicated disorder. Attempts to gain pathophysiologic insights about complicated disorders like CRPS based on case reports with poorly performed and uncontrolled interventions are misguided.

Neurogenic Edema from Complex Regional Pain Syndrome Resulting in Fulminant Infection Necessitating Below Elbow Amputation

We report a case of severe upper extremity complex regional pain syndrome type 1 (CRPS-1) and neurogenic edema that ultimately led to a medically necessary below-elbow amputation. The patient presented with a history of remote bilateral carpal tunnel release complicated by debilitating and recalcitrant bilateral CRPS-1. Following years of severe neurogenic edema of the left upper extremity, the patient had full-thickness skin sloughing on the dorsum of her hand due to massive edema. This subsequently led to maggot infestation of the soft tissues of the left hand ultimately necessitating amputation. We present the case as an illustration of an extreme case of neurogenic edema, a potential physical manifestation of CRPS-1. The case presented discusses upper extremity amputation as an end treatment option for CRPS-1, though in this case amputation was primarily indicated secondary to medical necessity.

Complex regional pain syndrome-up-to-date

Complex regional pain syndrome (CRPS) was described for the first time in the 19th century by Silas Weir Mitchell. After the exclusion of other causes, CRPS is characterised by a typical clinical constellation of pain, sensory, autonomic, motor, or trophic symptoms which can no longer be explained by the initial trauma. These symptoms spread distally and are not limited to innervation territories. If CRPS is not improved in the acute phase and becomes chronic, the visible symptoms change throughout because of the changing pathophysiology; the pain, however, remains. The diagnosis is primarily clinical, although in complex cases further technical examination mainly for exclusion of alternative diagnoses is warranted. In the initial phase, the pathophysiology is dominated by a posttraumatic inflammatory reaction by the activation of the innate and adaptive immune system. In particular, without adequate treatment, central nociceptive sensitization, reorganisation, and implicit learning processes develop, whereas the inflammation moderates. The main symptoms then include movement disorders, alternating skin temperature, sensory loss, hyperalgesia, and body perception disturbances. Psychological factors such as posttraumatic stress or pain-related fear may impact the course and the treatability of CRPS. The treatment should be ideally adjusted to the pathophysiology. Pharmacological treatment maybe particularly effective in acute stages and includes steroids, bisphosphonates, and dimethylsulfoxide cream. Common anti-neuropathic pain drugs can be recommended empirically. Intravenous long-term ketamine administration has shown efficacy in randomised controlled trials, but its repeated application is demanding and has side effects. Important components of the treatment include physio- and occupational therapy including behavioural therapy (eg, graded exposure in vivo and graded motor imaging). If psychosocial comorbidities exist, patients should be appropriately treated and supported. Invasive methods should only be used in specialised centres and in carefully evaluated cases. Considering these fundamentals, CRPS often remains a chronic pain disorder but the devastating cases should become rare.

Orofacial complex regional pain syndrome: pathophysiologic mechanisms and functional MRI

Complex regional pain syndrome (CRPS) is one of the most challenging chronic pain conditions and is characterized by burning pain, allodynia, hyperalgesia, autonomic changes, trophic changes, edema, and functional loss involving mainly the extremities. Until recently, very few reports have been published concerning CRPS involving the orofacial area. We report on a 50-year-old female patient who presented with unbearable pain in all of her teeth and hypersensitivity of the facial skin. She also reported intractable pain in both extremities accompanied by temperature changes and orofacial pain that increased when the other pains were aggravated. In the case of CRPS with trigeminal neuropathic pain, protocols for proper diagnosis and prompt treatment have yet to be established in academia or in the clinical field. We performed functional magnetic resonance imaging for a thorough analysis of the cortical representation of the affected orofacial area immediately before and immediately after isolated light stimulus of the affected hand and foot and concluded that CRPS can be correlated with trigeminal neuropathy in the orofacial area. Furthermore, the patient was treated with carbamazepine administration and stellate ganglion block, which can result in a rapid improvement of pain in the trigeminal region.

Efficacy of vitamin C in preventing complex regional pain syndrome after wrist fracture: A systematic review and meta-analysis

BACKGROUND

Complex regional pain syndrome type I (CRPS-I), previously known as reflex sympathetic dystrophy, is common after conservatively or surgically treated wrist fractures. Several studies support the efficacy of vitamin C in preventing CRPS-I, although the data are somewhat conflicting. The primary objective of this systematic literature review and meta-analysis was to assess the efficacy of vitamin C therapy in preventing CRPS-I after a wrist fracture.

METHODS

Randomised, placebo-controlled trials of vitamin C to prevent CRPS-I after wrist fractures were sought in the three main databases: PubMed (1980 to December 2015), CENTRAL (Central 2015, number 12), and Embase (1980 to December 2015). Two authors worked independently to select articles. Data from selected articles were collected independently.

RESULTS

Three randomised placebo-controlled trials in a total of 875 patients were included. Treatment was non-operative in 758/890 (85.1%) fractures and operative in 132 (14.9%) fractures. Vitamin C supplementation was started on the day of the injury and continued for 50 days. In the group given 500mg of vitamin C daily, the risk ratio for CRPS-I was 0.54 (95%CI, 0.33-0.91; P=0.02). Thus, the risk of developing CRPS-I was significantly decreased by prophylactic treatment with 500mg of vitamin C per day. The heterogeneity rate was 65% (non-significant).

CONCLUSION

Daily supplementation with 500mg of vitamin C per day for 50 days decreases the 1-year risk of CRPS-I after wrist fracture.

LEVEL OF EVIDENCE

II, systematic review of level I and II studies.

Pain Phenotypes and Associated Clinical Risk Factors Following Traumatic Amputation: Results from Veterans Integrated Pain Evaluation Research (VIPER)

OBJECTIVE

To define clinical phenotypes of postamputation pain and identify markers of risk for the development of chronic pain.

DESIGN

Cross-sectional study of military service members enrolled 3-18 months after traumatic amputation injury.

SETTING

Military Medical Center.

SUBJECTS

124 recent active duty military service members.

METHODS

Study subjects completed multiple pain and psychometric questionnaires to assess the qualities of phantom and residual limb pain. Medical records were reviewed to determine the presence/absence of a regional catheter near the time of injury. Subtypes of residual limb pain (somatic, neuroma, and complex regional pain syndrome) were additionally analyzed and associated with clinical risk factors.

RESULTS

A majority of enrolled patients (64.5%) reported clinically significant pain (pain score ≥ 3 averaged over previous week). 61% experienced residual limb pain and 58% experienced phantom pain. When analysis of pain subtypes was performed in those with residual limb pain, we found evidence of a sensitized neuroma in 48.7%, somatic pain in 40.8%, and complex regional pain syndrome in 19.7% of individuals. The presence of clinically significant neuropathic residual limb pain was associated with symptoms of PTSD and depression. Neuropathic pain of any severity was associated with symptoms of all four assessed clinical risk factors: depression, PTSD, catastrophizing, and the absence of regional analgesia catheter.

CONCLUSIONS

Most military service members in this cohort suffered both phantom and residual limb pain following amputation. Neuroma was a common cause of neuropathic pain in this group. Associated risk factors for significant neuropathic pain included PTSD and depression. PTSD, depression, catastrophizing, and the absence of a regional analgesia catheter were associated with neuropathic pain of any severity.

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.

The Effect of Written Information on Recall of Surgical Risks of Carpal Tunnel Release Surgery: A Randomized Controlled Study

BACKGROUND

Written information has been thought to help patients recall surgical risks discussed during the informed consent process, but has not been assessed for carpal tunnel release, a procedure with the rare but serious risk of complex regional pain syndrome. The authors' objective was to determine whether providing a pamphlet would improve patients' ability to remember the risks of surgery.

METHODS

Sixty patients seen for carpal tunnel release were included in this prospective, single-blind, randomized study. Patients received either a written pamphlet of the risks of surgery or no additional information following a standardized consultation. Two weeks after the initial consultation, patients were contacted to assess their risk recall and whether they had read about the operation from any source.

RESULTS

There was no difference in terms of the number of risks recalled between pamphlet (1.33 ± 1.21) or control groups (1.45 ± 1.22; p = 0.73). Recall of infection was better in the pamphlet group (p < 0.05). No patients remembered complex regional pain syndrome. There was no difference in the proportion of people who read additional information about carpal tunnel release surgery between the pamphlet (34.8 percent) and control groups (21.4 percent; p = 0.39), but reading about carpal tunnel release surgery was associated with improved recall (2.45 ± 1.13 versus 0.77 ± 0.91; p < 0.01).

CONCLUSIONS

Reading about surgery improved risk recall, but providing this information in the form of a pamphlet did not, nor did it affect patients' ability to recall the risk of complex regional pain syndrome. These results demonstrate that surgeons should implement additional measures to improve comprehension of surgical risks.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, I.