Complex regional pain syndrome--diagnostic, mechanisms, CNS involvement and therapy

Ketamine Infusion for Complex Regional Pain Syndrome Treatment: A Narrative Review

PURPOSE OF REVIEW

Complex Regional Pain Syndrome (CRPS) is a neuropathic pain disorder characterized by pain disproportionate to the inciting event that is constant for an extended duration. Numerous treatment options for this condition have been explored with unsatisfactory results in many cases. Ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist typically used as an anesthetic and analgesic, presents a promising potential treatment for CRPS in patients who fail to respond to traditional therapies.

RECENT FINDINGS

Numerous studies report significant improvement in the degree of pain, mobility of extremities, and other parameters after ketamine infusion in patients with CRPS. Although adverse effects were not reported often, some subjects experienced nausea, vomiting, headache or psychotropic or psychomimetic symptoms which could be mitigated with cessation of the drug. Although more research is needed to determine optimal dosing and duration, ketamine seems to be a safe and effective treatment for refractory cases of CRPS.

CONCLUSION

The present investigation summarizes existing knowledge and research surrounding ketamine infusions for CRPS to provide a well-rounded depiction of advantages and disadvantages for physicians who may be considering it for patients with this challenging and complex condition.

10. Complex regional pain syndrome

INTRODUCTION

Complex regional pain syndrome (CRPS) is a clinical disorder that can develop following surgery or trauma. Based on the most prominent underlying pathophysiological mechanisms, CRPS can be classified into different subtypes, namely inflammatory, nociplastic/neuropathic, vasomotor, and motor. Depending on the subtype, personalized treatment can be applied. If conservative treatments are insufficient or ineffective, more invasive treatments may be recommended. This article provides an overview of the most recent insights into CRPS and discusses the most common invasive treatments.

METHODS

The literature regarding interventional treatments for CRPS has been systematically reviewed and summarized.

RESULTS

Bisphosphonates are effective in treating the inflammatory subtype, while ketamine can provide pain relief for the nociplastic/neuropathic subtype. Sympathetic blocks are effective in addressing vasomotor disturbances. For patients with refractory symptoms, neurostimulation is a viable option due to its multimechanistic properties for all subtypes. End-of-line motor disturbances may benefit from intrathecal baclofen.

CONCLUSIONS

CRPS is a debilitating condition with an unpredictable course. The effectiveness of treatment varies from patient to patient. When conservative approaches prove insufficient, gradual progression to invasive treatments based on the underlying subtype is recommended.

Bone Scintigraphy in 2 Cases of Complex Regional Pain Syndrome

ABSTRACT

A 59-year-old woman was presented to the outpatient clinic with persistent pain after a hyperextension/inversion trauma of the ankle. Six months after the incident, a 3-phase bone scan was performed. A second patient, a 54-year-old man, was referred for a 3-phase bone scan 2 months after his right hand was twisted while using a drill. In both patients, scintigraphy showed diffuse increased uptake in the affected limb in all 3 phases. The x-rays of the affected limbs showed osteopenia. These findings are consistent with (early phase) complex regional pain syndrome.

Virtual Reality Facilitated Exercise Increases Sympathetic Activity and Reduces Pain Perception: A Randomized Crossover Study

OBJECTIVE

Both virtual reality and exercise reduce pain while avoiding the risks of traditional pharmacotherapy. The aim of this study was to assess how virtual reality-facilitated exercise modulates sympathetic activity and pain perception.

DESIGN

Healthy adult volunteers were randomized by hand dominance and then subjected to a standardized cold pressor test while experiencing a virtual reality application. After a 5-min washout, participants were crossed-over and repeated the test on their other hand while undergoing a virtual reality-facilitated exercise application. Sympathetic activation, pain sensation, and pain tolerance data were collected identically during both conditions.

RESULTS

One hundred ten participants were analyzed. Sympathetic activity increased in both conditions but was higher in the virtual reality-facilitated exercise condition ( P < 0.0001). Pain sensation scores were initially higher with virtual reality-facilitated exercise but dropped below the virtual reality-only condition by the end of the intervention ( P = 0.0175). There were no differences in pain tolerance between conditions ( P = 0.18).

CONCLUSIONS

The decrease in pain perception with virtual reality-facilitated exercise condition compared to virtual reality alone indicates virtual reality-facilitated exercise can be a useful tool for managing pain. Though this effect did not translate into higher pain tolerance, virtual reality-facilitated exercise may be a useful intervention in the setting of physical therapy or for patients with chronic pain.

Complex Regional Pain Syndrome: Evidence-Based Advances in Concepts and Treatments

PURPOSE OF REVIEW

This review presents the most current information about the epidemiology of complex regional pain syndrome (CRPS), classification and diagnostic criteria, childhood CRPS, subtypes, pathophysiology, conventional and less conventional treatments, and preventive strategies.

RECENT FINDINGS

CRPS is a painful disorder with multifactorial pathophysiology. The data describe sensitization of the central and peripheral nervous systems, inflammation, possible genetic factors, sympatho-afferent coupling, autoimmunity, and mental health factors as contributors to the syndrome. In addition to conventional subtypes (type I and type II), cluster analyses have uncovered other proposed subtypes. Prevalence of CRPS is approximately 1.2%, female gender is consistently associated with a higher risk of development, and substantial physical, emotional, and financial costs can result from the syndrome. Children with CRPS seem to benefit from multifaceted physical therapy leading to a high percentage of symptom-free patients. The best available evidence along with standard clinical practice supports pharmacological agents, physical and occupational therapy, sympathetic blocks for engaging physical restoration, steroids for acute CRPS, neuromodulation, ketamine, and intrathecal baclofen as therapeutic approaches. There are many emerging treatments that can be considered as a part of individualized, patient-centered care. Vitamin C may be preventive. CRPS can lead to progressively painful sensory and vascular changes, edema, limb weakness, and trophic disturbances, all of which substantially erode healthy living. Despite some progress in research, more comprehensive basic science investigation is needed to clarify the molecular mechanisms of the disease so that targeted treatments can be developed for better outcomes. Incorporating a variety of standard therapies with different modes of action may offer the most effective analgesia. Introducing less conventional approaches may also be helpful when traditional treatments fail to provide sufficient improvement.

Effectiveness of Decision Support to Treat Complex Regional Pain Syndrome

Background: Complex regional pain syndrome (CRPS) type 1 is a rare but disabling pain condition, usually involving distal extremities such as the wrist, hand, ankle, and foot due to either direct or indirect traumas. CRPS type 1 is characterized by a complex set of symptoms where no correlation can be identified between the severity of the initial injury and the ensuing painful syndrome. Over the years, numerous treatment strategies have been proposed for CRPS management, but therapies remain controversial. At present, no successful therapeutic intervention exists for this condition. The aim of the present study was to propose and assess the effectiveness of a rehabilitative treatment algorithm for CRPS, which is actually in use at our institution. Methods: We retrospectively reviewed all the patients that underwent physical rehabilitative treatment algorithm for hand CRPS between 2011 and 2017 at our Institution. Results: All the parameters taken into consideration, namely the Purdue Pegboard Test (PPT), Disability of the Arm, Shoulder and Hand (DASH), Visual Analog Scale (VAS), as well hand edema, were significantly improved at the end of the rehabilitation protocol. Conclusions: The results obtained in the present study demonstrated that our rehabilitation protocol was able to achieve substantial improvement in pain and quality of life scores. Thus, an early and skillful rehabilitation intervention is of paramount importance for CPRS type 1 management to achieve a stable and optimal functional recovery while preventing the onset of deformities.

Autoantibodies from patients with complex regional pain syndrome (CRPS) induce pro-inflammatory effects and functional disturbances on endothelial cells in vitro

ABSTRACT

Complex regional pain syndrome (CRPS) is an inadequate local response after a limb trauma, which leads to severe pain and autonomic and trophic changes of the affected limb. Autoantibodies directed against human β2 adrenergic and muscarinic M2-receptors (hβ2AR and hM2R) have been described in CRPS-patients previously.We analyzed sera from CRPS-patients for autoantibodies against hß2AR, hM2R and endothelial cells, and investigated the functional effects of purified IgG, derived from 13 CRPS patients, on endothelial cells. Eleven healthy controls, seven radial fracture patients without CRPS, and 10 patients with peripheral arterial vascular disease served as controls.CRPS-IgG, but not control IgG, bound to the surface of endothelial cells (P < 0.001) and to hβ2AR and hM2R (P < 0.05), the latter being reversed by adding β2AR and M2R antagonists. CRPS-IgG led to an increased cytotoxicity and a reduced proliferation rate of endothelial cells, and by adding specific antagonists, the effect was neutralized. Regarding second messenger pathways, CRPS-IgG induced ERK-1/2-, P38-, and STAT1-phosphorylation, while AKT-phosphorylation was decreased at the protein level. In addition, increased expression of adhesion molecules (ICAM-1, VCAM-1) on the mRNA-level was induced by CRPS-IgG, thus inducing a pro-inflammatory condition of the endothelial cells.Our results show that patients with CRPS not only develop autoantibodies against hβ2AR and hM2R, but these antibodies interfere with endothelial cells, inducing functional effects on these in vitro, and thus might contribute to the pathophysiology of CRPS.

Left/right discrimination is not impaired in people with unilateral chronic Achilles tendinopathy

OBJECTIVE

Impaired left/right discrimination of an affected body part has been observed in various chronic pain states. This study aimed to examine whether people with unilateral chronic Achilles tendinopathy also present with impaired left/right discrimination.

DESIGN

Cross-sectional study.

METHODS

Nineteen runners with persistent unilateral Achilles tendinopathy and 19 matched healthy volunteers performed a left/right discrimination task in a laboratory setting. Participants were shown pictures of feet, hands and Shepard-Metzler figures and were asked to decide as accurately and as fast as possible whether the body part belonged to the left or right side of the body, or whether the Shepard-Metzler figures were rotated or mirrored. Performance was evaluated in terms of accuracy and response time. Data were analysed with mixed-design ANOVAs.

RESULTS

The decline in left/right discrimination ability at group level, if present, between affected and unaffected side, or compared to healthy participants, was negligible for both accuracy (<1.5%) and response time (<50 ms). There was no significant effect of side (affected versus unaffected side) or group (people with Achilles tendinopathy versus healthy) for accuracy (p > 0.36) or response time (p > 0.69).

CONCLUSIONS

People with Achilles tendinopathy recognised the affected side as accurately and as fast as the non-affected side and their performance was comparable to healthy participants. The absence of impaired left/right discrimination despite the chronicity of the condition may be attributable to the typical intermittent nature of Achilles tendinopathy pain and/or maintained sports activity.

Impaired Performance in Mental Rotation of Hands and Feet and Its Association with Social Cognition in Patients with Complex Regional Pain Syndrome

Objectives. 

So far, dysfunction in mental rotation has been assessed in relation to the left- or right-sided CRPS. Here we examined mental rotation in patients with upper or lower limb CRPS. Considering the potential role of socio-emotional functioning on the perception of body image, we further investigated the association between performance on mental rotation and socio-emotional characteristics.

Methods. 

We examined the performance of 36 patients with upper or lower limb CRPS on the limb laterality recognition. Accuracy and response times for pictures of hands and feet at 4 rotation angles were evaluated. Socio-emotional functioning was measured by the Interpersonal Reactivity Scale and the Toronto Alexithymia Scale.

Results. 

Patients with upper limb pain showed longer RTs to recognize the laterality of hands than feet (P = 0.002), whereas patients with lower limb pain showed longer RTs for feet than hands (P = 0.039). Exploratory correlation analyses revealed that RTs for feet were negatively correlated with the levels of empathic ability to take another’s perspective (P = 0.006) and positively correlated with the level of emotional difficulty in identifying feelings (P = 0.006).

Conclusions. 

This study is the first to report selectively impaired mental rotation of hands vs feet in patients with upper or lower limb CRPS. The findings suggest that impaired mental rotation derives from relative deficits in the representation of the affected limb. Correlations between impaired mental rotation and socio-emotional inability indicate that an altered body schema may be closely associated with impaired social cognitive aspects in CRPS patients.

The challenge of recognizing severe pain and autonomic abnormalities for early diagnosis of CRPS

OBJECTIVES

Complex regional pain syndrome (CRPS) is a disabling usually post-traumatic pain condition. International guidelines emphasize early diagnosis for treatment and improved outcome. Early intense and persistent pain along with features of autonomic dysfunction in the first week's post-injury are early warning signs for development of CRPS. We have previously reported a delayed diagnosis of CRPS. The main purpose of the present study was to investigate possible causes of a delayed diagnosis, with a special focus of recognition of risk factors.

METHODS

A total of 52 CRPS 1 (without detectable nerve damage) and CRPS 2 (with evidence of nerve lesion) patients were included in the study. When examined at OUS-Rikshospitalet, we retrospectively asked the patients on the development of pain and autonomic abnormalities from the time of the eliciting injury, performed a thorough clinical investigation with an emphasis on signs of autonomic failure and compared symptoms and clinical findings with such information in previous medical records. We also evaluated symptoms and signs according to the type of injury they had suffered.

RESULTS

Of a total of 52 patients (30 women and 22 men, mean age 39.0 years at the time of injury), 34 patients had CRPS type 1 (65.4%) and 18 CRPS type 2 (34.6%), 25 patients with pain in the upper and 27 in the lower extremity. A total of 35 patients (67.3%) were diagnosed with CRPS (following mean 2.1 years) prior to the investigation at OUS-Rikshospitalet (mean 4.86 years following injury). Mean time from injury to diagnosis was 33.5 months (SD 30.6) (2.8 years) for all patients. In retrospect, all 17 patients first diagnosed at OUS met the CRPS diagnosis at an earlier stage. All patients retrospectively reported intense pain (numeric rating scale > 7) from the time of injury with a large discrepancy to previous medical records which only stated intense pain in 29.4% of patients with CRPS type 1 and 44.4% of patients with CRPS type 2 within the first four months. While the patients reported an early onset of autonomic dysfunction, present in 67.3 and 94.2% of the patients within one week and one month, respectively, reports of autonomic abnormalities within the first four months was far less (maximum in 51.7% of patients with CRPS type 1 and in 60% in CRPS 2). In 10 patients with CRPS type 1, no symptom nor sign of autonomic abnormalities was reported.

CONCLUSIONS

We still find a significant delay in the diagnosis of CRPS. There is a large discrepancy between both self-reporting of intense, disproportionate pain, as well as symptoms of autonomic abnormalities from the time of injury, and documentation in previous medical records. Our findings suggest a lack of awareness of risk factors for the development of CRPS, such as early intense pain and autonomic abnormalities without recovery, contributing to delayed diagnosis. The present results suggest causes of delayed CRPS-diagnosis. An increased attention to early warning signs/risk factors may improve diagnosis of CRPS.

Neuromodulation for Pain Management in the Inpatient Setting: A Narrative Review

Pain is highly prevalent and pharmacological therapy is not always efficacious. There are a few pathophysiological reasons to believe that neuromodulation would increase the rate of success of pain management. This review article is focused on that aspect, discussing non-invasive or minimally invasive neuromodulation techniques in both the inpatient and outpatient setting. This article provides an in-depth discussion of the multiple neuromodulation techniques available over time to be suitable and effective when used as analgesic therapies for chronic pain. We reviewed the literature and discussed all available neuromodulation options that were tested in the inpatient and outpatient setting. Neuromodulation plays a very important role in treating chronic pain in both inpatient and outpatient setting.

Treating Complex Regional Pain Syndrome Using Counterstrain: A Novel Approach

Complex regional pain syndrome (CRPS) is a challenging disease to treat and requires a multidisciplinary and multimodal approach. We discuss the use of a novel approach to counterstrain using irritants - as identified by the patient - to induce symptoms of neuropathy and paresthesia and treat these symptoms as if they were counterstrain tender points. This treatment approach to CRPS has not previously been described in osteopathic manipulative treatment (OMT) literature, including Foundations of Osteopathic Medicine. A 23-year-old female presented with an array of symptoms consistent with complex regional pain syndrome in her right foot and lower leg that had been gradually worsening for approximately one year. She had been treated with physical therapy, medications, injections, orthotics, and a transcutaneous nerve stimulation (TENS) unit, all of which provided temporary symptomatic relief but had not treated the underlying disease. By utilizing the mentioned osteopathic approach to treat the neuropathic aspect of her CRPS, we were able to produce a lasting resolution of her symptoms and improve her loss in proprioception and temperature discrimination in the affected limb. A counterstrain should be considered a reasonable option to assist in the treatment of complex regional pain syndrome. This new treatment approach does not require extensive training or experience with osteopathic manipulative treatment, nor does it take much time to administer. Thus, it could be easily learned and utilized by many standard practitioners for patients with complex regional pain syndrome. In addition, given its low intensity and passive approach, it more likely to be tolerated well by patients. Understanding the challenging nature of treating complex regional pain syndrome, this report aims to be helpful in adding to the general fund of knowledge regarding this condition and the possible treatments. We fully understand that the safety of this intervention cannot be demonstrated with one case nor can the effectiveness. However, our goal is to emphasize and educate readers of these promising results with the hope that this can be the first step toward the required further research in prospective and controlled trials.

Complex regional pain syndrome: An updated comprehensive review

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

Effect of Early Orthopedic Rehabilitation on Development of Complex Regional Pain Syndrome Type 1

Objective

Complex regional pain syndrome (CRPS) is a syndrome usually occurs in one extremity and characterized by pain, tenderness with palpation, and symptoms of autonomic nervous system dysfunction. An essential factor in the etiology of CRPS is immobilization of the extremity as a result of a fracture. Delaying the start of physical medicine and rehabilitation program after removal of the plaster or splint may increase the rates of CRPS development in patients with fractures. This study aims to determine a direct relationship between delay time in rehabilitation and CRPS development.

Materials and Methods

Patients admitted to our physical therapy and rehabilitation outpatient clinic within the last 3 years (January 2016 to January 2018) for orthopedic rehabilitation following fractures were retrospectively analyzed. CRPS development status, the delay time for the rehabilitation program was determined in 38 CRPS patients of 91 patients with fractures. Probit regression was used to reveal the relationship between delay time for rehabilitation and CRPS development.

Results

CRPS development rates were decreased by years (48.71% in 2016, 43.47% in 2017, and 31.03% in 2018). When cases in 2016 were taken as a reference, it was seen that cases in 2017 and 2018 were exposed to CRPS approximately 0.03% and 16.00% lower than the reference year, 2016. A delay of one day exposes the patient to approximately 0.35% more CRPS.

Conclusion

As the delay time for rehabilitation in our clinic decreased, the incidence of CRPS decreased. The awareness of physicians and patients about the importance of early rehabilitation should be improved.

Bradykinin Receptors Play a Critical Role in the Chronic Post-ischaemia Pain Model

Complex regional pain syndrome type-I (CRPS-I) is a chronic painful condition resulting from trauma. Bradykinin (BK) is an important inflammatory mediator required in acute and chronic pain response. The objective of this study was to evaluate the association between BK receptors (B₁ and B₂) and chronic post-ischaemia pain (CPIP) development in mice, a widely accepted CRPS-I model. We assessed mechanical and cold allodynia, and paw oedema in male and female Swiss mice exposed to the CPIP model. Upon induction, the animals were treated with BKR antagonists (HOE-140 and DALBK); BKR agonists (Tyr-BK and DABK); antisense oligonucleotides targeting B₁ and B₂ and captopril by different routes in the model (7, 14 and 21 days post-induction). Here, we demonstrated that treatment with BKR antagonists, by intraperitoneal (i.p.), intraplantar (i.pl.), and intrathecal (i.t.) routes, mitigated CPIP-induced mechanical allodynia and oedematogenic response, but not cold allodynia. On the other hand, i.pl. administration of BKR agonists exacerbated pain response. Moreover, a single treatment with captopril significantly reversed the anti-allodynic effect of BKR antagonists. In turn, the inhibition of BKRs gene expression in the spinal cord inhibited the nociceptive behaviour in the 14th post-induction. The results of the present study suggest the participation of BKRs in the development and maintenance of chronic pain associated with the CPIP model, possibly linking them to CRPS-I pathogenesis.

A medical mystery of complex regional pain syndrome

Complex regional pain syndrome (CRPS) is a condition of neuropathic pain, which is characterized by significant autonomic and inflammatory features. CRPS occurs in patients who have limb surgery, limb fractures, or trauma. Many patients may have pain resolve within twelve months of the inciting incident; however, a small subset progresses to the chronic form. This transitional process often happens by changing from warm CRPS with dominant inflammatory phase to cold CRPS, in which autonomic characteristics or manifestations dominate. Several peripheral and central mechanisms are involved, which might vary among individuals over a period of time. Other contributors include peripheral and central sensitization, autonomic alterations, inflammatory and immune changes, neurochemical changes, and psychological and genetic factors. Although effective management of the chronic CRPS form is often challenging, there are a few high quality randomized controlled trials that support the efficacy of the most commonly used therapeutic approaches.

Mechanism-specific rehabilitation management of complex regional pain syndrome: Proposed recommendations from evidence synthesis

STUDY DESIGN

Narrative review.

INTRODUCTION

There are a variety of treatments with demonstrated effectiveness for the management of complex regional pain syndrome (CRPS). However given the variability in symptom presentation in this population, therapists may be unsure what treatments would be most effective for individual clients.

PURPOSE OF THE STUDY

To present a brief synthesis of the literature and propose a rehabilitation version of a mechanism-specific management algorithm to guide personalized treatment of CRPS.

METHODS

A systematic search of the literature was conducted to identify all randomized controlled trials, systematic reviews, and clinical practice guidelines addressing rehabilitation of CRPS. Results were reviewed independently by 2 reviewers and final selection of articles was reached by consensus, Data was extracted using standardized forms, and a single rater gave quality ratings. Both reviewers then used the extracted data to present a synthesis of the evidence categorized by the proposed mechanisms of effect.

RESULTS

A total of 111 articles were retrieved and reviewed for inclusion; 49 were selected for data extraction. A synthesis of the key recommendations was compiled into a rehabilitation-specific version of the mechanism-based management algorithm proposed by Gierthmühlen et al (2014).

CONCLUSIONS

Consideration of mechanism-appropriate rehabilitation interventions may assist therapists to select the most appropriate and effective treatments from the body of evidence supporting rehabilitation of CRPS.

Posttraumatic Complex Regional Pain Syndrome and Related Comorbidities

The complex regional pain syndrome (CRPS) is a neuropathic disorder, often precipitated by a fracture, injury of the soft tissue or a surgical procedure followed by extended immobilization. Clinical signs and symptoms of this syndrome include abnormalities of pain processing (mechanical and thermal allodynia, hyperalgesia and hyperpathia), skin changes regarding local temperature and the presence of erythema, cyanosis or mottled appearance, neurogenic edema, motor and trophic disorders. The CRPS has three evolutionary stages-acute, dystrophic and atrophic, and it is divided into two types, reflecting the absence or presence of nerve damage. The patient presented in this study was a female with a history of metabolic syndrome, diagnosed with polyarticular chronic gout, which despite the specific drug treatment administered, had multiple predisposing factors for the development of CRPS consecutive to the fracture of both bones of the right forearm. It is evident that the recovery period after injury is slightly different in each individual and depends on the severity of the injury and patient factors such as age, general condition and the presence of other comorbidities. The delay between the onset of symptoms and her presentation to the physician, conferred a poor prognosis for the developing pathology, with important functional and motor impairment.

Complex Regional Pain Syndrome: An update

Complex regional pain syndrome (CRPS) is a perplexing painful syndrome of the extremities usually following a harmful event. It is distinguished in two types, mainly depending on the presence of nerve injury. Although its prevalence may vary depending on social and ethnic factors, middle-aged women seem to suffer most often and the upper limb is the most commonly affected extremity. Apart from pain, which is the dominating feature, the clinical picture unfolds across several domains: sensory, motor, autonomic and trophic. This syndrome develops in two phases, the acute (warm) phase, with the classic symptoms of inflammation, and the chronic (cold) phase, often characterized by trophic changes of the soft tissues and even bones. Although the syndrome has been studied for over two decades, no imaging or laboratory test has been established for the diagnosis and recently proposed diagnostic criteria have not yet been validated and are only occasionally applied. Its pathophysiology is still quite obscure, although the most likely mechanisms involve the classic and neurogenic paths of inflammation mediated by cytokines and neuropeptides, intertwined with changes of the autonomic and central nervous system, psychological mechanisms and, perhaps, autoimmunity. Although plenty of treatment modalities have been tried, none has been proven unequivocally efficacious. Apart from information and education, which should be offered to all patients, the most effective pharmacological treatments seem to be bisphosphonates, glucocorticoids and vasoactive mediators, while physical therapy and rehabilitation therapy also make part of the treatment.

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.

Evaluation Through Transcutaneous Tissue Oximetry (Near Infrared Spectroscopy) of Spinal Cord Stimulation in Patients With Complex Regional Pain Syndrome Type I

OBJECTIVE

One of the physiopathological hypothesis behind complex regional pain syndrome (CRPS) type I involves the deep-tissue hypoxia of the affected areas. Spinal cord stimulation (SCS) appears to be effective in the treatment of these patients. We evaluated whether ESCS modifies tissue oxygen saturation (StO₂ ) measured with near-infrared spectroscopy (NIRS) in the affected limbs in patients diagnosed with CRPS type I.

MATERIALS AND METHODS

Nonrandomized, cross-sectional study that evaluated 16 patients with CRPS type I who were receiving SCS applied to the posterior cords. NIRS was used to evaluate baseline StO₂ (primary outcome) and variations in StO₂ (secondary outcome) during an ischemia-reperfusion test performed using a vascular occlusion test, comparing the hands of limbs unilaterally affected by CRPS type I with the unaffected contralateral hands. We also determined whether the variations in StO₂ were related to a modification in the percentage of subjective pain improvement and in the visual analog scale score.

RESULTS

The baseline StO₂ of the affected hands was significantly higher than that of the unaffected hands (mean 4.7%; 95% confidence interval: 1.41, 6.7; p = 0.005). Variations in StO₂ during the ischemia-reperfusion test revealed no differences between affected and unaffected hands. No significant correlations were detected between baseline StO₂ values or variations in StO₂ during the vascular occlusion test and the pain measurements.

CONCLUSIONS

Baseline StO₂ evaluated by NIRS was greater in the affected hands of patients with CRPS type I treated with SCS than in the unaffected, contralateral hands.

Complex Regional Pain Syndrome of Non-hemiplegic Upper Limb in a Stroke Patient: A Case Report

Complex regional pain syndrome (CRPS) type I in stroke patients is usually known to affect the hemiplegic upper limb. We report a case of CRPS presented in an ipsilesional arm of a 72-year-old female patient after an ischemic stroke at the left middle cerebral artery territory. Clinical signs such as painful range of motion and hyperalgesia of her left upper extremity, swollen left hand, and dystonic posture were suggestive of CRPS. A three-phase bone scintigraphy showed increased uptake in all phases in the ipsilesional arm. Diffusion tensor tractography showed significantly decreased fiber numbers of the corticospinal tract and the spinothalamic tract in both unaffected and affected hemispheres. Pain and range of motion of the left arm of the patient improved after oral steroids with a starting dose of 50 mg/day.

Update on the effects of graded motor imagery and mirror therapy on complex regional pain syndrome type 1: A systematic review

Graded motor imagery (GMI) and mirror therapy (MT) is thought to improve pain in patients with complex regional pain syndrome (CRPS) types 1 and 2. However, the evidence is limited and analysis are not independent between types of CRPS. The purpose of this review was to analyze the effects of GMI and MT on pain in independent groups of patients with CRPS types 1 and 2. Searches for literature published between 1990 and 2016 were conducted in databases. Randomized controlled trials that compared GMI or MT with other treatments for CRPS types 1 and 2 were included. Six articles met the inclusion criteria and were classified from moderate to high quality. The total sample was composed of 171 participants with CRPS type 1. Three studies presented GMI with 3 components and three studies only used the MT. The studies were heterogeneous in terms of sample size and the disorders that triggered CRPS type 1. There were no trials that included participants with CRPS type 2. GMI and MT can improve pain in patients with CRPS type 1; however, there is not sufficient evidence to recommend these therapies over other treatments given the small size and heterogeneity of the studied population.

Bone scintigraphy in patients with pain

Nuclear medicine imaging is widely used in pain medicine. Low back pain is commonly encountered by physicians, with its prevalence from 49% to 70%. Computed tomography (CT) or magnetic resonance imaging (MRI) are usually used to evaluate the cause of low back pain, however, these findings from these scans could also be observed in asymptomatic patients. Bone scintigraphy has an additional value in patients with low back pain. Complex regional pain syndrome (CRPS) is defined as a painful disorder of the extremities, which is characterized by sensory, autonomic, vasomotor, and trophic disturbances. To assist the diagnosis of CRPS, three-phase bone scintigraphy is thought to be superior compared to other modalities, and could be used to rule out CRPS due to its high specificity. Studies regarding the effect of bone scintigraphy in patients with extremity pain have not been widely conducted. Ultrasound, CT and MRI are widely used imaging modalities for evaluating extremity pain. However, SPECT/CT has an additional role in assessing pain in the extremities.

Adult Complex Regional Pain Syndrome Type I: A Narrative Review

Complex regional pain syndrome type I (CRPS I) is a multifactorial painful disorder with a complex pathogenesis. Both peripheral and central mechanisms are involved. Acute CRPS I is considered to be an exaggerated inflammatory disorder; however, over time, because of altered function of the sympathetic nervous system and maladaptive neuroplasticity, CRPS I evolves into a neurological disorder. This review thoroughly describes the pathophysiological aspects of CRPS I and summarizes the potential therapeutic options. The mechanisms and targets of the treatment are different in the early and late stages of the disease. This current review builds on a previous review by this author group by deepening the role of the peripheral classic and neuronal inflammatory component in the acute stage of this painful disorder.

LEVEL OF EVIDENCE

Not applicable.

The refined biomimetic NeuroDigm GEL™ model of neuropathic pain in a mature rat

Background: Many humans suffering with chronic neuropathic pain have no objective evidence of an etiological lesion or disease. Frequently their persistent pain occurs after the healing of a soft tissue injury. Based on clinical observations over time, our hypothesis was that after an injury in mammals the process of tissue repair could cause chronic neural pain. Our objectives were to create the delayed onset of neuropathic pain in rats with minimal nerve trauma using a physiologic hydrogel, and characterize the rats' responses to known analgesics and a targeted biologic. Methods: In mature male Sprague Dawley rats (age 9.5 months) a percutaneous implant of tissue-derived hydrogel was placed in the musculofascial tunnel of the distal tibial nerve. Subcutaneous morphine (3 mg/kg), celecoxib (10 mg/kg), gabapentin (25 mg/kg) and duloxetine (10 mg/kg) were each screened in the model three times each over 5 months after pain behaviors developed. Sham and control groups were used in all screenings. A pilot study followed in which recombinant human erythropoietin (200 units) was injected by the GEL™ neural procedure site. Results: The GEL group gradually developed mechanical hypersensitivity lasting months. Morphine, initially effective, had less analgesia over time. Celecoxib produced no analgesia, while gabapentin and duloxetine at low doses demonstrated profound analgesia at all times tested. The injected erythropoietin markedly decreased bilateral pain behavior that had been present for over 4 months, p ≤ 0.001. Histology of the GEL group tibial nerve revealed a site of focal neural remodeling, with neural regeneration, as found in nerve biopsies of patients with neuropathic pain. Conclusion: The refined NeuroDigm GEL™ model induces a neural response resulting in robust neuropathic pain behavior. The analgesic responses in this model reflect known responses of humans with neuropathic pain. The targeted recombinant human erythropoietin at the ectopic neural lesion appears to alleviate the persistent pain behavior in the GEL™ model rodents.

The refined biomimetic NeuroDigm GEL™ Model of neuropathic pain in the mature rat

Background:Many humans suffering with chronic pain have no clinical evidence of a lesion or disease. They are managed with a morass of drugs and invasive procedures. Opiates usually become less effective over time. In many, their persistent pain occurs after the healing of a soft tissue injury. Current animal models of neuropathic pain typically create direct neural damage with open surgeries using ligatures, neurectomies, chemicals or other forms of deliberate trauma. However, we have observed clinically that after an injury in humans, the naturally occurring process of tissue repair can cause chronic neural pain.Methods:We demonstrate how the refined biomimetic NeuroDigm GEL™ Model, in the mature male rat, gradually induces neuropathic pain behavior with a nonsurgical percutaneous implant of tissue-derived hydrogel in the musculo-fascial tunnel of the distal tibial nerve. Morphine, Celecoxib, Gabapentin and Duloxetine were each screened in the model three times each over 5 months after pain behaviors developed. A pilot study followed in which recombinant human erythropoietin was applied to the GEL neural procedure site.Results:The GEL Model gradually developed neuropathic pain behavior lasting months. Morphine, initially effective, had less analgesia over time. Celecoxib produced no analgesia, while gabapentin and duloxetine at low doses had profound analgesia at all times tested. The injected erythropoietin markedly decreased bilateral pain behavior that had been present for over 4 months. Histology revealed a site of focal neural remodeling, with neural regeneration, as in human biopsies.Conclusion:The refined NeuroDigm GEL™ Model induces localized neural remodeling resulting in robust neuropathic pain behavior. The analgesics responses in this model reflect known responses of humans with neuropathic pain. The targeted recombinant human erythropoietin appears to heal the ectopic focal neural site, as demonstrated by the extinguishing of neuropathic pain behavior present for over 4 months.

Sympathetic Responses to Noxious Stimulation of Muscle and Skin

Acute pain triggers adaptive physiological responses that serve as protective mechanisms that prevent continuing damage to tissues and cause the individual to react to remove or escape the painful stimulus. However, an extension of the pain response beyond signaling tissue damage and healing, such as in chronic pain states, serves no particular biological function; it is maladaptive. The increasing number of chronic pain sufferers is concerning, and the associated disease burden is putting healthcare systems around the world under significant pressure. The incapacitating effects of long-lasting pain are not just psychological – reflexes driven by nociceptors during the establishment of chronic pain may cause serious physiological consequences on regulation of other body systems. The sympathetic nervous system is inherently involved in a host of physiological responses evoked by noxious stimulation. Experimental animal and human models demonstrate a diverse array of heterogeneous reactions to nociception. The purpose of this review is to understand how pain affects the sympathetic nervous system by investigating the reflex cardiovascular and neural responses to acute pain and the long-lasting physiological responses to prolonged (tonic) pain. By observing the sympathetic responses to long-lasting pain, we can begin to understand the physiological consequences of long-term pain on cardiovascular regulation.

Involvement of the Sympathetic Nervous System in Complex Regional Pain Syndrome

Complex regional pain syndrome (CRPS) occasionally develops as a complication of limb trauma. Sympathetic neurotransmitter release is compromised in the affected limb of at least a subgroup of patients throughout the course of the disorder, whereas signs of sympathetic deficit (a warm flushed limb) often evolve into signs of sympathetic overactivity (a cool moist limb) due to the development of adrenergic supersensitivity. Cross-talk between sympathetic neurotransmitters and the sensory neurons that signal pain appears to contribute to CRPS in a subgroup of patients. In addition, sympathetic activity may retard normal healing by aggravating the vascular disturbances associated with inflammation. Sympathetic dysfunction seems to originate from within the central nervous system in patients without peripheral nerve injury, possibly in association with chronic activation of the “defeat” response associated with inhibitory opioid-mediated pain modulation. Fatigue of this inhibitory process may unmask a facilitatory influence of arousal on nociceptive transmission in the thalamus and cortex that contributes to stress-induced pain.

Pregabalin Treatment of a Patient With Complex Regional Pain Syndrome

BACKGROUND

Complex regional pain syndrome (CRPS) is a painful and disabling neurovascular condition. There is no consensus on the etiopathogenesis or the treatment. We present a patient with CRPS type 1 accompanied by a psychiatric disorder to discuss the relationship between CRPS and psychiatric disease and to emphasize the response of this case to treatment with pregabalin.

PATIENT DESCRIPTION

A 15-year-old girl presented with swelling, severe pain, edema, hyperesthesia, allodynia, and sweating changes in the left arm and was diagnosed as CRPS type 1. The presence of disturbed family relations was revealed on psychiatric examination, and a diagnosis of major depression was made. Her symptoms did not respond to selective serotonin reuptake inhibitors and noradrenergic and specific serotonergic antidepressives, gabapentin, or stellate ganglion blockage, but the patient's pain resolved with pregabalin. Symptom-oriented measures and psychiatric support enabled ongoing treatment. A social services evaluation led to her being placed in the care of social services to protect her from the chaotic and traumatic family life.

CONCLUSION

Detailed psycological and psychiatric evaluation is recommended in individuals with CRPS because psychiatric support and improvement of associated psychosocial concerns in addition to pregabalin seems to facilitate treatments in some patients.

Complex regional pain syndrome type I: a comprehensive review

BACKGROUND

Complex regional pain syndrome type I (CRPS I), formerly known as reflex sympathetic dystrophy (RSD), is a chronic painful disorder that usually develops after a minor injury to a limb. This topical review gives a synopsis of CRPS I and discusses the current concepts of our understanding of CRPS I in adults, the diagnosis, and treatment options based on the limited evidence found in medical literature. CRPS I is a multifactorial disorder. Possible pathophysiological mechanisms of CRPS I are classic and neurogenic inflammation, and maladaptive neuroplasticity. At the level of the central nervous system, it has been suggested that an increased input from peripheral nociceptors alters the central processing mechanisms.

METHODS

A literature search was conducted using, as electronic bibliographic database, Medline from 1980 until 2014.

RESULTS

An early diagnosis and multidisciplinary treatment are necessary to prevent permanent disability.

CONCLUSIONS

The pharmacological treatment of CRPS I is empirical and insufficiently effective. Further research is needed regarding the therapeutic modalities discussed in the guidelines. Physical therapy is widely recommended as a first-line treatment. The efficacy of local anesthetic sympathetic blockade as treatment for CRPS I is questionable.

Inflammation in cold complex regional pain syndrome

BACKGROUND

In patients with complex regional pain syndrome (CRPS), the temperature of the affected side often differs from that of the contralateral side. In the acute phase, the affected side is usually warmer than the contralateral side, the so-called 'warm' CRPS. This thermal asymmetry can develop into a colder affected side, the so-called 'cold' CRPS. In contrast to cold CRPS, in warm CRPS, inflammation is generally assumed to be present. However, there are reports of cold CRPS patients, successfully treated with vasodilatation therapy, who subsequently displayed warm CRPS. It seems that inflammation could be 'hidden' behind vasomotor disturbance. This study was designed to test this hypothesis.

METHODS

A retrospective analysis was made of patients in our CRPS database. We defined three types of CRPS: cold CRPS, neither cold nor warm (intermediate) CRPS, and warm CRPS. Of these patients, the difference between the level of the pro-inflammatory cytokines interleukin (IL)-6 (Δ IL-6) and tumor necrosis factor (TNF)-α (Δ TNF-α) in the affected extremity and that in the contralateral extremity was determined.

RESULTS

The bilateral difference of the level of these cytokines did not differ among patients with cold CRPS, intermediate CRPS, or those with warm CRPS.

CONCLUSION

Inflammation may be involved in cold CRPS.

Post stroke pain: identification, assessment, and therapy

BACKGROUND

Pain is a common complication after stroke and is associated with the presence of depression, cognitive dysfunction, and impaired quality of life. It remains underdiagnosed and undertreated, despite evidence that effective treatment of pain may improve function and quality of life.

SUMMARY

We provide an overview of the means for clinical assessment and risk factors for the development of post-stroke pain, then review the newest available literature regarding the commonest post-stroke pain syndromes, including central post-stroke pain, complex regional pain syndrome, musculoskeletal pain including shoulder subluxation, spasticity-related pain, and post-stroke headache, as well as the available epidemiology and current treatment options. Key Messages: In the best interests of optimizing quality of life and function after stroke, clinicians should be aware of pain as a common complication after stroke, identify those patients at highest risk, directly inquire as to the presence and characteristics of pain, and should be aware of the options for treatment for the various pain syndromes.

The roads to mitochondrial dysfunction in a rat model of posttraumatic syringomyelia

The pathophysiology of posttraumatic syringomyelia is incompletely understood. We examined whether local ischemia occurs after spinal cord injury. If so, whether it causes neuronal mitochondrial dysfunction and depletion, and subsequent energy metabolism impairment results in cell starvation of energy and even cell death, contributing to the enlargement of the cavity. Local blood flow was measured in a rat model of posttraumatic syringomyelia that had received injections of quisqualic acid and kaolin. We found an 86 ± 11% reduction of local blood flow at C8 where a cyst formed at 6 weeks after syrinx induction procedure (P < 0.05), and no difference in blood flow rate between the laminectomy and intact controls. Electron microscopy confirmed irreversible neuronal mitochondrion depletion surrounding the cyst, but recoverable mitochondrial loses in laminectomy rats. Profound energy loss quantified in the spinal cord of syrinx animals, and less ATP and ADP decline observed in laminectomy rats. Our findings demonstrate that an excitotoxic injury induces local ischemia in the spinal cord and results in neuronal mitochondrial depletion, and profound ATP loss, contributing to syrinx enlargement. Ischemia did not occur following laminectomy induced trauma in which mitochondrial loss and decline in ATP were reversible. This confirms excitotoxic injury contributing to the pathology of posttraumatic syringomyelia.

Repetitive transcranial magnetic stimulation in chronic pain: a review of the literature

OBJECTIVE

To review the literature on the analgesic effects of repetitive transcranial magnetic stimulation (rTMS) in chronic pain according to different pain syndromes and stimulation parameters.

DATA SOURCES

Publications on rTMS and chronic pain were searched in PubMed and Google Scholar using the following key words: chronic pain, analgesia, transcranial magnetic stimulation, neuropathic pain, fibromyalgia, and complex regional pain syndrome.

STUDY SELECTION

This review only included double-blind, controlled studies with >10 participants in each arm that were published from 1996 to 2014 and written in English. Studies with relevant information for the understanding of the effects of rTMS were also cited.

DATA EXTRACTION

The following data were retained: type of pain syndrome, type of study, coil type, target, stimulation intensity, frequency, number of pulses, orientation of induced current, number of session, and a brief summary of intervention outcomes.

DATA SYNTHESIS

A total of 33 randomized trials were found. Many studies reported significant pain relief by rTMS, especially high-frequency stimulation over the primary motor cortex performed in consecutive treatment sessions. Pain relief was frequently >30% compared with control treatment. Neuropathic pain, fibromyalgia, and complex regional pain syndrome were the pain syndromes more frequently studied. However, among all published studies, only a few performed repetitive sessions of rTMS.

CONCLUSIONS

rTMS has potential utility in the management of chronic pain; however, studies using maintenance sessions of rTMS and assessing the effects of rTMS on the different aspects of chronic pain are needed to provide a more solid basis for its clinical application for pain relief.

Immediate Return to Ambulation and Improved Functional Capacity for Rehabilitation in Complex Regional Pain Syndrome following Early Implantation of a Spinal Cord Stimulation System

Complex regional pain syndrome (CRPS) is a neuropathic pain condition that is characterized by vasomotor, sensory, sudomotor, and motor symptoms. Spinal cord stimulation (SCS) has been successfully utilized for the treatment of pain refractory to conventional therapies. We present a case of a previously highly functioning 54-year-old female who developed a rarely reported case of idiopathic CRPS of the right ankle which spontaneously occurred four months after an uncomplicated anterior cervical disc fusion. This condition resulted in severe pain and functional impairment that was unresponsive to pharmacological management. The patient's rehabilitation was severely stymied by her excruciating pain. However, with the initiation of spinal cord stimulation, her pain was adequately controlled allowing for progression to full unassisted ambulation, advancing functional capacity, and improving quality of life. This case report supports the concept that rapid progression to neuromodulation, rather than delays that occur due to attempts at serial sympathetic blocks, may better control symptoms leading allowing for a more meaningful recovery.

Photoplethysmographic signals to predict the success of lumbar sympathetic blockade for lower extremity pain

OBJECTIVE

A prospective, observational study to investigate how photoplethysmography (PPG) signals change during lumbar sympathetic blockade (LSB), and whether these changes can predict sympathetically mediated pain (SMP).

METHODS

Patients with unilateral lower extremity pain and self-reported cold hyperalgesia underwent LSB. Bilateral temperature and PPG signals (AC and DC) were recorded. Power spectrum analysis (PSA) was performed.

RESULTS

Of the total patient cohort (n = 38), eight patients (22.1%) had excellent pain-relief after LSB and were determined to have SMP. In all patients, the PPG AC signal changed immediately after drug administration, before any temperature change. DC signals decreased slowly in a linear fashion. PSA of DC signals showed significantly lower low-frequency/high-frequency (LF/HF) ratios in the SMP group than the sympathetically independent pain group, both before and after LSB. A cut-off value of 2.92 for LF/HF resulted in sensitivity, specificity and positive predictive values for SMP of 75.0%, 76.7% and 3.21 [1.5, 6.9], respectively.

CONCLUSIONS

PPG may be used as an early indicator of a successful LSB and could also be helpful in diagnosing SMP.

Spinal cord stimulation for complex regional pain syndrome type 1 with dystonia: a case report and discussion of the literature

Background: Complex Regional Pain Syndrome type 1 (CRPS-1) is a debilitating chronic pain disorder, the physiopathology of which can lead to dystonia associated with changes in the autonomic, central and peripheral nervous system. An interdisciplinary approach (pharmacological, interventional and psychological therapies in conjunction with a rehabilitation pathway) is central to progress towards pain reduction and restoration of function.Aim: This case report aims to stimulate reflection and development of mechanism-based therapeutic strategies concerning CRPS associated with dystonia.Case description: A 31 year old female CRPS-1 patient presented with dystonia of the right foot following ligamentoplasty for chronic ankle instability. She did not have a satisfactory response to the usual therapies. Multiple anesthetic blocks (popliteal, epidural and intrathecal) were not associated with significant anesthesia and analgesia. Mobilization of the foot by a physiotherapist was not possible. A multidisciplinary approach with psychological support, physiotherapy and spinal cord stimulation (SCS) brought pain relief, rehabilitation and improvement in the quality of life.Conclusion: The present case report demonstrates the occurrence of multilevel (peripheral and central) pathological modifications in the nervous system of a CRPS-1 patient with dystonia. This conclusion is based on the patient’s pain being resistant to anesthetic blocks at different levels and the favourable, at least initially, response to SCS. The importance of the bio-psycho-social model is also suggested, permitting behavioural change.

Complex regional pain syndrome: a review

Complex regional pain syndrome, formally known as reflex sympathetic dystrophy, is a poorly understood condition that describes a collection of clinical symptoms and signs occurring in the peripheries most commonly after trauma. Pain is the main problem. It is generally out of proportion to the degree of injury and can be unresponsive to narcotics. In addition joint stiffness, temperature and colour changes, and swelling occur. The diagnosis and treatment are challenging for any clinician and a multidisciplinary approach is often necessary with physiotherapy, occupational therapy, and the pain team. The hand surgeon is involved for two reasons, firstly as the upper limb is the most frequently involved, and secondly because the condition may be a complication of the patient's surgery and result in a much prolonged recovery. This review elucidates the recent advances in the knowledge of the aetiology, classification and treatment of this fascinating condition.

Spinal cord stimulation as treatment for complex regional pain syndrome should be considered earlier than last resort therapy

BACKGROUND

Spinal cord stimulation (SCS), by virtue of its historically described up-front costs and level of invasiveness, has been relegated by several complex regional pain syndrome (CRPS) treatment algorithms to a therapy of last resort. Newer information regarding safety, cost, and efficacy leads us to believe that SCS for the treatment of CRPS should be implemented earlier in a treatment algorithm using a more comprehensive approach.

METHODS

We reviewed the literature on pain care algorithmic thinking and applied the safety, appropriateness, fiscal or cost neutrality, and efficacy (S.A.F.E.) principles to establish an appropriate position for SCS in an algorithm of pain care.

RESULTS AND CONCLUSION

Based on literature-contingent considerations of safety, efficacy, cost efficacy, and cost neutrality, we conclude that SCS should not be considered a therapy of last resort for CRPS but rather should be applied earlier (e.g., three months) as soon as more conservative therapies have failed.

Hypothalamic-pituitary-adrenal axis function in patients with complex regional pain syndrome type 1

An exaggerated inflammatory process is considered an important pathophysiological feature of complex regional pain syndrome type 1 (CRPS-1). The hypothalamic-pituitary-adrenal (HPA) axis serves as a negative feedback mechanism for inflammatory processes. The present study examined the HPA axis function in patients with CRPS-1 by a determination of cortisol concentrations in saliva. Three sets of saliva samples were sequentially collected from 24 patients with CRPS-1 during medication (on-Med), 72 h after stopping medication (off-Med) and 8h after the oral administration of 1mg dexamethasone. One set of saliva samples was collected from healthy controls. The cortisol awakening response (CAR) and diurnal cortisol decline (DCD) were used as indices for HPA axis function. Cortisol levels during the post-awakening period in patients were increased following withdrawal of medications. The CAR during the off-Med condition was disappeared after administration of dexamethasone. Among the examined CRPS-related numerical variables, the frequency of spontaneous pain attacks showed relationships with the indices of HPA axis function. After classifying the patients into two subgroups, we observed that the CAR and DCD in patient who had a relatively high frequency of spontaneous pain attacks (subgroup 5 ≤) were lower and less steep than those in patient who had a relatively low frequency of spontaneous pain attacks (subgroup 0-4) for the on- and off-Med conditions. The CAR and DCD in subgroup 5 ≤ during their off-Med condition were comparable to those in controls. These results suggest that the increase in frequency of spontaneous pain attacks is associated with a reduced CAR and flattened DCD in patients CRPS-1.

Behavioral and sensory changes after direct ischemia-reperfusion injury in rats

Complex regional pain syndromes (CRPS) are disabling pain syndromes that can develop after trauma or minor tissue injury affecting a limb. Characteristics of CRPS are sensory signs and symptoms, autonomic abnormalities, trophic changes and an impaired motor function. Pathophysiological mechanisms for the development of CRPS are still a matter of investigation. Based on clinical data and investigations of CRPS patients it is hypothesized that tissue hypoxia and inflammation are important for the development of CRPS. The aim of the current study was therefore to examine if direct ischemia-reperfusion injury can induce behavior in rats with symptoms present in patients with CRPS. After baseline behavior measurements the femoral artery of Wistar rats was ligated for 3h with consecutive reperfusion. Sham-operated rats underwent the same preparation except ligation of the artery. Subsequent behavioral testing (observations of spontaneous pain behavior, paw withdrawal to mechanical, noxious mechanical, cold and heat stimuli) was performed up to two months after surgery. Both in rats that underwent ischemia and in sham-operated rats no obvious changes of hindpaw tissue were observed after ischemia-reperfusion injury (trophic changes, edema, differences in skin color or temperature). In behavioral tests only minor changes were observed, these being not different between postischemic rats and sham-operated rats. Using Wistar rats, our data do not support the idea that an ischemia-reperfusion injury can play a major role in the development of CRPS.