Reflex sympathetic dystrophy of the hand: an excessive inflammatory response?

Perspectives on the pharmacological management of complex regional pain syndrome

INTRODUCTION

Complex regional pain syndrome (CRPS) is a chronic pain condition that is notoriously difficult to treat. Therapies for CRPS include cognitive behavioral, physical, and occupational therapy, single or multidrug pharmacotherapy, and a variety of interventional techniques. Unfortunately, randomized clinical trials of these therapies are limited. The large number of potential pharmacologic options can be overwhelming for providers in their attempts to develop a treatment plan.

AREAS COVERED

This article will review the literature on the pharmacologic management of CRPS. It is based on a systematic search of PubMed using keywords, followed by evaluation of the bibliographies for relevant articles.

EXPERT OPINION

No single drug has amassed enough evidence to suggest clear efficacy, but a handful of agents with at least modest evidence are commonly used, including gabapentinoids, bisphosphonates, ketamine, and pulsed dose steroids. Meanwhile, other agents that lack significant evidence specifically in CRPS but have evidence in other neuropathic conditions are commonly prescribed, including tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SNRIs). In our opinion, careful selection and prompt initiation of appropriate pharmacotherapy may optimize pain relief and improve functionality in patients burdened with this debilitating condition.

Efficacy and Safety of N-acetylcysteine for the Management of Chronic Pain in Adults: A Systematic Review & Meta-analysis

OBJECTIVE

To assess the efficacy and safety of N-acetylcysteine in the treatment of chronic pain.

METHODS

A systematic search was carried out until April 2020 for clinical studies of N-acetylcysteine in the management of any persistent or recurrent chronic pain condition for adults ≥ 18 years old. Risk of Bias was assessed using the validated risk of bias tools. When appropriate, a meta-analysis using a random-effects model was performed, with a fixed-effect model for sensitivity analysis.

RESULTS

Nine studies (n = 863) were included (5 randomized controlled trials [RCTs], 2 open-label non-comparative studies and 2 comparative studies), that evaluated patients with sickle cell disease (3), complex regional pain syndrome (1), pelvic pain/endometriosis (2), rheumatoid arthritis (1), diabetic neuropathy (1), and chronic neuropathic pain (1). In the pooled analysis of 3 RCTs, N-acetylcysteine did not reduce pain intensities (SMD -0.21, 95% CI -0.33 to 0.75, random-effects), improve functional outcomes (SMD 0.21, 95% CI -0.33 to 0.75) or quality of life (SMD 0.60, 95% CI -4.44 to 5.64); however, sensitivity analysis with a fixed effect model demonstrated an effect for pain intensities and function. Due to adverse events being inconsistently reported, no conclusion could be made regarding safety of N-acetylcysteine in chronic pain.

CONCLUSIONS

While there is some evidence to indicate N-acetylcysteine may provide analgesic efficacy for certain pain conditions, there is insufficient evidence to provide definitive evidence on NAC in chronic pain management. Larger-size RCTs spanning a variety of chronic pain conditions are needed to determine N-acetylcysteine's role, if any, in pain medicine.

What Is the Effect of Vitamin C on Finger Stiffness After Distal Radius Fracture? A Double-blind, Placebo-controlled Randomized Trial

BACKGROUND

It is proposed that vitamin C administration can reduce disproportionate pain and stiffness after distal radius fracture; however, randomized trials that tested this hypothesis have had inconsistent results.

QUESTIONS/PURPOSES

(1) Is administering vitamin C after distal radius fracture associated with better ROM, patient-reported upper extremity function, and pain scores? (2) What factors are associated with post-fracture finger stiffness and worse upper extremity function?

METHODS

This is a double-blind, randomized, placebo-controlled, noncrossover study. Between August 2014 and July 2017, we approached 204 consecutive patients, of which 195 were eligible, and 134 chose to participate. Participants were randomized to receive once-daily 500 mg vitamin C (67 participants) or placebo (67 participants) within 2 weeks after distal radius fracture. All patients received usual care at the discretion of their surgeon. The mean age of participants was 49 ± 17 years, 99 patients (74%) were women, and 83 (62%) were treated nonoperatively. The primary outcome was the distance between the fingertip and distal palmar crease 6 weeks after fracture. This measure is easy to obtain and previously has been shown to correlate with aggregate ROM of all finger joints. The secondary outcomes were total active finger motion, total active thumb motion, upper extremity-specific limitations, and pain intensity.An a priori power analysis suggested 126 patients would provide 80% power to detect a difference of 2 cm (SD 4.0) fingertip distance to palmar crease with α set at 0.05 using a two-tailed Student's t-test. Accounting for 5% lost to followup, we included 134 patients.All analyses were intention-to-treat. Ten participants of the intervention group and five of the placebo group were lost to followup. Their missing data were addressed by multiple imputation, after which we performed linear regression analysis for our outcome variables.

RESULTS

Administration of vitamin C was not associated with ROM, function, or pain scores at 6 weeks (distance to palmar crease: β -0.23; 95% CI -1.7 to 1.2; p = 0.754; finger ROM: β 4.9; 95% CI, -40 to 50; p = 0.829; thumb ROM: β 0.98; 95% CI, -18 to 20; p = 0.918, Patient-Reported Outcomes Measurement Information System [PROMIS] score: β 0.32; 95% CI, -2.6 to 3.2; p = 0.828; pain score: β -0.62; 95% CI, -0.62 to 0.89; p = 0.729) nor at 6 months (PROMIS score: β -0.21; 95% CI, -3.7 to 3.3; p = 0.904; pain score: β 0.31; 95% CI, -0.74 to 1.4; p = 0.559). At 6 weeks, we found that more finger stiffness was mildly associated with greater age (β -1.5; 95% CI, -2.8 to -0.083; p = 0.038). Thumb stiffness was mildly associated with greater age (β -0.72; 95% CI, -1.3 to -0.18; p = 0.009) and strongly associated with operative treatment (β -32; 95% CI, -50 to -13; p = 0.001). Greater pain interference was modestly associated with greater functional limitations at 6 weeks (β -0.32; 95% CI, -0.52 to -0.12; p = 0.002) and 6 months (β -0.36; 95% CI, -0.60 to -0.11; p = 0.004).

CONCLUSIONS

Vitamin C does not seem to facilitate recovery after distal radius fracture, but amelioration of maladaptation to nociception (pain interference) merits greater attention.

LEVEL OF EVIDENCE

Level I, therapeutic study.

The Rodent Tibia Fracture Model: A Critical Review and Comparison With the Complex Regional Pain Syndrome Literature

Distal limb fracture is the most common cause of complex regional pain syndrome (CRPS), thus the rodent tibia fracture model (TFM) was developed to study CRPS pathogenesis. This comprehensive review summarizes the published TFM research and compares these experimental results with the CRPS literature. The TFM generated spontaneous and evoked pain behaviors, inflammatory symptoms (edema, warmth), and trophic changes (skin thickening, osteoporosis) resembling symptoms in early CRPS. Neuropeptides, inflammatory cytokines, and nerve growth factor (NGF) have been linked to pain behaviors, inflammation, and trophic changes in the TFM model and proliferating keratinocytes were identified as the primary source of cutaneous cytokines and NGF. Tibia fracture also activated spinal glia and upregulated spinal neuropeptide, cytokine, and NGF expression, and in the brain it changed dendritic architecture. B cell-expressed immunoglobulin M antibodies also contributed to pain behavior, indicating a role for adaptive immunity. These results modeled many findings in early CRPS, but significant differences were also noted.

PERSPECTIVE

Multiple neuroimmune signaling mechanisms contribute to the pain, inflammation, and trophic changes observed in the injured limb of the rodent TFM. This model replicates many of the symptoms, signs, and pathophysiology of early CRPS, but most post-fracture changes resolve within 5 months and may not contribute to perpetuating chronic CRPS.

Complex regional pain syndrome: evidence for warm and cold subtypes in a large prospective clinical sample

Limited research suggests that there may be Warm complex regional pain syndrome (CRPS) and Cold CRPS subtypes, with inflammatory mechanisms contributing most strongly to the former. This study for the first time used an unbiased statistical pattern recognition technique to evaluate whether distinct Warm vs Cold CRPS subtypes can be discerned in the clinical population. An international, multisite study was conducted using standardized procedures to evaluate signs and symptoms in 152 patients with clinical CRPS at baseline, with 3-month follow-up evaluations in 112 of these patients. Two-step cluster analysis using automated cluster selection identified a 2-cluster solution as optimal. Results revealed a Warm CRPS patient cluster characterized by a warm, red, edematous, and sweaty extremity and a Cold CRPS patient cluster characterized by a cold, blue, and less edematous extremity. Median pain duration was significantly (P < 0.001) shorter in the Warm CRPS (4.7 months) than in the Cold CRPS subtype (20 months), with pain intensity comparable. A derived total inflammatory score was significantly (P < 0.001) elevated in the Warm CRPS group (compared with Cold CRPS) at baseline but diminished significantly (P < 0.001) over the follow-up period, whereas this score did not diminish in the Cold CRPS group (time × subtype interaction: P < 0.001). Results support the existence of a Warm CRPS subtype common in patients with acute (<6 months) CRPS and a relatively distinct Cold CRPS subtype most common in chronic CRPS. The pattern of clinical features suggests that inflammatory mechanisms contribute most prominently to the Warm CRPS subtype but that these mechanisms diminish substantially during the first year postinjury.

The Therapeutic Effect of Vitamin C in an Animal Model of Complex Regional Pain Syndrome Produced by Prolonged Hindpaw Ischemia-Reperfusion in Rats

Objectives: It is known that increased free radicals from oxidative stress are one of the major causes of complex regional pain syndrome (CRPS). In this study, we tested the hypothesis that vitamin C has a dose-related treatment effect in a chronic post-ischemic pain (CPIP) model. Methods: A total of 49 male rats weighing 250 to 350 g were used. The 4 treatment groups were control (no medication), group 1.0 (administration of 1 mg/day for vitamin C for 5 days), group 2.5 (administration of 2.5 mg/day vitamin C for 5 days), and group 7.5 (administration of 7.5 mg/day vitamin C for 5 days). The 50% mechanical withdrawal threshold and total blood antioxidant status (TAS) were measured before and after administration of vitamin C. Results: Twenty-eight CPIP model rats were generated from 49 rats. Seven rats were randomly allocated to each group. The 50% mechanical withdrawal threshold of group 2.5 (after the administration of vitamin C) was higher than that of the control group and group 1.0 (P < 0.05). At 1 day of the administration of vitamin C, the 50% mechanical withdrawal threshold of group 1.0 was higher than that of the control group and the blood levels of TAS in groups 2.5 and 7.5 were higher than that in control group (P < 0.05). Twelve days after the administration of vitamin C, the blood levels of TAS in groups 2.5 and 7.5 were lower than that of the control group (P < 0.05). Discussion: The administration of a proper dose of vitamin C can reduce oxidative stress, increase antioxidants, and recover the threshold for mechanical allodynia in the CPIP model.

The Different Types of Algodystrophy after Fracture of the Distal Radius

A prospective study of algodystrophy after fracture of the distal radius was carried out to search for early diagnostic and prognostic criteria. One hundred consecutive patients were assessed by a radiographic score and by a semi-quantitative clinical score at 1, 6 and 12 weeks and 1 year after fracture. The reactive disorders observed could be classified in four groups, each with a different course. There was a close link between patient satisfaction at 1 year and the group to which the patient belonged. Algodystrophy was diagnosed in 26% of cases. Of these, 58% were active and left sequelae at 1 year. A clinical score greater than 7 at 6 weeks predicted 96% of these cases of active algodystrophy. Active algodystrophy was more likely after a severe initial injury and if there was pain at the distal radioulnar joint.

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.

Platelet and Erythrocyte Indexes in Complex Regional Pain Syndrome Type I

Objectives

This study aims to compare the levels of platelet and erythrocyte indexes including mean platelet volume, platelet distribution width (PDW), and red blood cell distribution (RDW) values between complex regional pain syndrome (CRPS) type I patients and healthy controls to establish a marker of neuroinflammation that might be a potential factor involved in CRPS etiopathogenesis.

Patients and methods

A total of 21 patients (14 males, 7 females; mean age 35.0±15.4 years; range 15 to 69 years) with a diagnosis of CRPS type I and 44 age- and sex-similar healthy controls (29 males, 15 females; mean age 35.8±8.5 years; range 16 to 53 years) were included in this study. Mean platelet volume, PDW, RDW, white blood count, hemoglobin, erythrocyte sedimentation rate, and C-reactive protein levels, and neutrophil to lymphocyte ratio and thrombocyte to lymphocyte ratio were compared between the patient and control groups.

Results

No differences were noted between patient and control groups in terms of erythrocyte sedimentation rate and C-reactive protein levels, white blood cell, neutrophil, lymphocyte and thrombocyte counts, and neutrophil to lymphocyte and thrombocyte to lymphocyte ratios (all p>0.05). When compared with controls, patients had significantly higher mean corpuscular volume (p=0.019) and RDW (p=0.002) values, and a lower PDW level (p=0.006).

Conclusion

Differences in PDW, RDW, and mean corpuscular volume values between patients and controls might support the potential role of neuroinflammation in the etiopathogenesis of CRPS type I. Prospective studies with larger sample sizes are warranted in the early detection and differential diagnosis of CRPS type I.

Neurogenic neuroinflammation in fibromyalgia and complex regional pain syndrome

Although fibromyalgia and complex regional pain syndrome (CRPS) have distinct clinical phenotypes, they do share many other features. Pain, allodynia and dysaesthesia occur in each condition and seem to exist on a similar spectrum. Fibromyalgia and CRPS can both be triggered by specific traumatic events, although fibromyalgia is most commonly associated with psychological trauma and CRPS is most often associated with physical trauma, which is frequently deemed routine or minor by the patient. Fibromyalgia and CRPS also seem to share many pathophysiological mechanisms, among which the most important are those involving central effects. Nonetheless, peripheral effects, such as neurogenic neuroinflammation, are also important contributors to the clinical features of each of these disorders. This Review highlights the differing degrees to which neurogenic neuroinflammation might contribute to the multifactorial pathogenesis of both fibromyalgia and CRPS, and discusses the evidence suggesting that this mechanism is an important link between the two disorders, and could offer novel therapeutic targets.

The influence of vitamin C on the outcome of distal radial fractures: a double-blind, randomized controlled trial

BACKGROUND

Vitamin C has been proposed to improve outcomes after a distal radial fracture by promotion of bone and soft-tissue healing and reduction of the prevalence of complex regional pain syndrome (CRPS). Our primary aim was to examine the effect of vitamin C on functional outcome after a distal radial fracture.

METHODS

A total of 336 adult patients with an acute fracture of the distal aspect of the radius were recruited over a one-year period and randomized to receive 500 mg of vitamin C or placebo daily for fifty days after the fracture. The primary outcomes were the DASH (Disabilities of the Arm, Shoulder and Hand) score at six weeks and at one year. Secondary variables included complications, wrist and finger motion, grip and pinch strength, pain, and a CRPS score.

RESULTS

There were no significant differences in patient or fracture characteristics between the treatment groups. There was no significant effect of vitamin C on the DASH score throughout the study period. At six weeks, patients in the vitamin C group with a nondisplaced fracture had a significantly greater wrist flexion deficit (p = 0.008) and pinch strength deficit (p = 0.020) and a greater rate of CRPS (p = 0.022), but there was no difference in the CRPS rate at any other time point. At twenty-six weeks, there was a higher rate of complications (p = 0.043) and greater pain with use (p = 0.045) in the patients with a displaced fracture treated with vitamin C. There was no significant difference in the time to fracture-healing.

CONCLUSIONS

This study demonstrated no significant difference at one year in the DASH score, other functional outcomes, the rate of CRPS, or osseous healing of nondisplaced or displaced distal radial fractures treated with vitamin C compared with placebo. We conclude that administration of vitamin C confers no benefit to patients with a displaced or nondisplaced fracture of the distal aspect of the radius.

LEVEL OF EVIDENCE

Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Immobilization contributes to exaggerated neuropeptide signaling, inflammatory changes, and nociceptive sensitization after fracture in rats

A tibia fracture cast immobilized for 4 weeks can induce exaggerated substance P and calcitonin gene-related peptide signaling and neuropeptide-dependent nociceptive and inflammatory changes in the hind limbs of rats similar to those seen in complex regional pain syndrome (CRPS). Four weeks of hind limb cast immobilization can also induce nociceptive and vascular changes resembling CRPS. To test our hypothesis that immobilization alone could cause exaggerated neuropeptide signaling and inflammatory changes, we tested 5 cohorts of rats: 1) controls; 2) tibia fracture and hind limb casted; 3) hind limb casted, no fracture; 4) tibia fracture with intramedullary pinning, no cast; and 5) tibia fracture with intramedullary pinning and hind limb casting. After 4 weeks, the casts were removed and hind limb allodynia, unweighting, warmth, edema, sciatic nerve neuropeptide content, cutaneous and spinal cord inflammatory mediator levels, and spinal c-Fos activation were measured. After fracture with casting, there was allodynia, unweighting, warmth, edema, increased sciatic nerve substance P and calcitonin gene-related peptide, increased skin neurokinin 1 receptors and keratinocyte proliferation, increased inflammatory mediator expression in the hind paw skin (tumor necrosis factor-α, interleukin [IL]-1β, IL-6, nerve growth factor) and cord (IL-1β, nerve growth factor), and increased spinal c-Fos activation. These same changes were observed after cast immobilization alone, except that spinal IL-1β levels were not increased. Treating cast-only rats with a neurokinin 1 receptor antagonist inhibited development of nociceptive and inflammatory changes. Four weeks after fracture with pinning, all nociceptive and vascular changes had resolved and there were no increases in neuropeptide signaling or inflammatory mediator expression.

PERSPECTIVE

Collectively, these data indicate that immobilization alone increased neuropeptide signaling and caused nociceptive and inflammatory changes similar to those observed after tibia fracture and casting, and that early mobilization after fracture with pinning inhibited these changes. Early limb mobilization after fracture may prevent the development of CRPS.

Bilateral Hypersensitivity to Capsaicin, Thermal, and Mechanical Stimuli in Unilateral Complex Regional Pain Syndrome

Background:

Complex regional pain syndrome is multifactorial. Exaggerated inflammatory responses to limb injury may be involved. The authors hypothesized that capsaicin-induced pain and neurogenic inflammation (skin perfusion and flare area) are increased in patients with complex regional pain syndrome compared with that in controls.

Methods:

Twenty patients with unilateral upper-limb complex regional pain syndrome and 20 age-, sex-, and body mass index–matched controls participated. Topical capsaicin 5% was applied to the back of both hands for 30 min, and pain intensity was assessed on a visual analogue scale. A laser Doppler perfusion imager scanner estimated capsaicin-induced skin perfusion and flare area. Autonomic and small-fiber function was assessed by sensory testing, quantitative sudomotor axon reflex test, and vasoconstrictor responses.

Results:

The authors found bilateral hypersensitivity to capsaicin (P ≤ 0.02), skin fold (P = 0.001), joint pressure (P &lt; 0.0001), cold (P ≤ 0.01), and heat pain (P ≤ 0.04) in patients compared with that in controls and thermal and mechanical hyperalgesia in the complex regional pain syndrome–affected hand compared with that in the unaffected hand (P ≤ 0.001). The patients had normal capsaicin-induced flare areas, thermal detection thresholds, quantitative sudomotor axon reflex test, and vasoconstrictor responses.

Conclusions:

The main finding is bilaterally increased capsaicin-induced pain in patients compared with controls. The flare response to capsaicin was normal, suggesting that the increased pain response was not due to increased neurogenic inflammation. The bilateral hypersensitivity to painful chemical, thermal, and mechanical stimuli not confined to the innervation area of a peripheral nerve or root cannot be explained by a regional change and may partly be due to central sensitization.

Inflammation in CRPS: role of the sympathetic supply

Acute Complex Regional Pain Syndrome (CRPS) is associated with signs of inflammation such as increased skin temperature, oedema, skin colour changes and pain. Pro-inflammatory cytokines (tumour necrosis factor-α (TNF-α), interleukin-2 (IL-2), IL-1beta, IL-6) are up-regulated, whereas anti-inflammatory cytokines (IL-4, IL-10) are diminished. Adaptive immunity seems to be involved in CRPS pathophysiology as many patients have autoantibodies directed against β2 adrenergic and muscarinic-2 receptors. In an animal tibial fracture model changes in the innate immune response such as up-regulation of keratinocytes are also found. Additionally, CRPS is accompanied by increased neurogenic inflammation which depends mainly on neuropeptides such as CGRP and Substance P. Besides inflammatory signs, sympathetic nervous system involvement in CRPS results in cool skin, increased sweating and sympathetically-maintained pain. The norepinephrine level is lower in the CRPS-affected than contralateral limb, but sympathetic sprouting and up-regulation of alpha-adrenoceptors may result in an adrenergic supersensitivity. The sympathetic nervous system and inflammation interact: norepinephrine influences the immune system and the production of cytokines. There is substantial evidence that this interaction contributes to the pathophysiology and clinical presentation of CRPS, but this interaction is not straightforward. How inflammation in CRPS might be exaggerated by sympathetic transmitters requires further elucidation.

Mast cells: a new target in the treatment of complex regional pain syndrome?

There is convincing evidence that inflammation plays a pivotal role in the pathophysiology of complex regional pain syndrome (CRPS). Besides inflammation, central sensitization is also an important phenomenon. Mast cells are known to be involved in the inflammatory process of CRPS and also play a role (at least partially) in the process of central sensitization. In the development of a more mechanism-based treatment, influencing the activity of mast cells might be important in the treatment of CRPS. We describe the rationale for using medication that counteracts the effects of mast cells in the treatment of CRPS.

Targeting oxidative injury and cytokines' activity in the treatment with anti-tumor necrosis factor-α antibody for complex regional pain syndrome 1

Cytokines and oxygen free radicals have been implicated in the potential pathogenic development of complex regional pain syndrome (CRPS). We aimed to analyze the relationship between clinical status, circulating levels of cytokines, and markers of oxidative damage during the treatment with anti-TNFα antibodies. The patient chosen for treatment had not had improvement through a number of conventional therapies and fulfilled the current diagnostic criteria for CRPS-1. We investigated the clinical variables before and after systemic administration of 1.4 mg/kg anti-TNFα antibody (infliximab), repeated after 1 month in a dose of 3 mg/kg. Blood samples were collected before and after anti-TNFα antibodies administration, and plasma was analyzed for 8-isoprostane-prostaglandin F2α (8-iso-PGF2α, a marker of oxidative injury) and cytokines (TNF-α, IL-4, IL-6, IL-7, IL-8, IL-10, IL-17A). Plasma concentrations of 8-iso-PGF2α were measured with radioimmunoassay (RIA), and the kinetics of cytokines were detected in plasma by antibody-based proximity ligation (PLA). Pathologically high levels of 8-iso-PGF2α were found in the patient. Immediately after each administration of infliximab, the levels of 8-iso-PGF2α decreased. Although the patient showed an improvement of the cutaneous dystrophic symptoms and diminished pain associated with these lesions, the levels of circulating TNFα increased after the administration of anti-TNFα antibodies. In a patient with CRPS-1 treated with anti-TNFα antibodies, we report increased levels of circulating TNFα and a temporary mitigation of oxidative stress as measured by plasma F2 -isoprostane. This case report provides evidence 2 supporting the indication of monitoring the oxidative stress biomarkers during treatment with anti-TNFα antibodies in CRPS 1.

Neuropeptide deficient mice have attenuated nociceptive, vascular, and inflammatory changes in a tibia fracture model of complex regional pain syndrome

BACKGROUND

Distal limb fracture in man can induce a complex regional pain syndrome (CRPS) with pain, warmth, edema, and cutaneous inflammation. In the present study substance P (SP, Tac1(-/-)) and CGRP receptor (RAMP1(-/-)) deficient mice were used to investigate the contribution of neuropeptide signaling to CRPS-like changes in a tibia fracture mouse model. Wildtype, Tac1(-/-), and RAMP1(-/-) mice underwent tibia fracture and casting for 3 weeks, then the cast was removed and hindpaw mechanical allodynia, unweighting, warmth, and edema were tested over time. Hindpaw skin was collected at 3 weeks post-fracture for immunoassay and femurs were collected for micro-CT analysis.

RESULTS

Wildtype mice developed hindpaw allodynia, unweighting, warmth, and edema at 3 weeks post-fracture, but in the Tac1(-/-) fracture mice allodynia and unweighting were attenuated and there was no warmth and edema. RAMP1(-/-) fracture mice had a similar presentation, except there was no reduction in hindpaw edema. Hindpaw skin TNFα, IL-1β, IL-6 and NGF levels were up-regulated in wildtype fracture mice at 3 weeks post-fracture, but in the Tac1(-/-) and RAMP1(-/-) fracture mice only IL-6 was increased. The epidermal keratinocytes were the cellular source for these inflammatory mediators. An IL-6 receptor antagonist partially reversed post-fracture pain behaviors in wildtype mice.

CONCLUSIONS

In conclusion, both SP and CGRP are critical neuropeptide mediators for the pain behaviors, vascular abnormalities, and up-regulated innate immune responses observed in the fracture hindlimb. We postulate that the residual pain behaviors observed in the Tac1(-/-) and RAMP1(-/-) fracture mice are attributable to the increased IL-6 levels observed in the hindpaw skin after fracture.

Keratinocyte expression of inflammatory mediators plays a crucial role in substance P-induced acute and chronic pain

Tibia fracture in rats followed by cast immobilization leads to nociceptive, trophic, vascular and bone-related changes similar to those seen in Complex Regional Pain Syndrome (CRPS). Substance P (SP) mediated neurogenic inflammation may be responsible for some of the signs of CRPS in humans. We therefore hypothesized that SP acting through the SP receptor (NK1) leads to the CRPS-like changes found in the rat model. In the present study, we intradermally injected rats with SP and monitored hindpaw mechanical allodynia, temperature, and thickness as well as tissue levels of tumor necrosis factor-α (TNF-α), interleukin 1β (IL-1β), interleukin 6 (IL-6), and nerve growth factor-β (NGF) for 72 h. Anti-NGF antibody was utilized to block the effects of SP-induced NGF up-regulation. Fracture rats treated with the selective NK1 receptor antagonist LY303870 prior to cast removal were assessed for BrdU, a DNA synthesis marker, incorporation in skin cells to examine cellular proliferation. Bone microarchitecture was measured using micro computed tomography (μCT). We observed that: (1) SP intraplantar injection induced mechanical allodynia, warmth and edema as well as the expression of nociceptive mediators in the hindpaw skin of normal rats, (2) LY303870 administered intraperitoneally after fracture attenuated allodynia, hindpaw unweighting, warmth, and edema, as well as cytokine and NGF expression, (3) LY303870 blocked fracture-induced epidermal thickening and BrdU incorporation after fracture, (4) anti-NGF antibody blocked SP-induced allodynia but not warmth or edema, and (5) LY303870 had no effect on bone microarchitecture. Collectively our data indicate that SP acting through NK1 receptors supports the nociceptive and vascular components of CRPS, but not the bone-related changes.

Is there a correlation between symptoms and bone scintigraphic findings in patients with complex regional pain syndrome?

BACKGROUND

Complex regional pain syndrome (CRPS) is characterized by pain in combination with sensory, vasomotor, sudomotor, trophic and motor abnormalities. The diagnosis of CRPS is based primarily on clinical criteria and the presence of distinct signs and symptoms. The role of bone scintigraphy in the diagnosis of these patients has been limited by its variable sensitivity. In this study, we aim to look if the presence of specific symptoms or symptom subgroups in patients with clinically diagnosed CRPS correlates with scintigraphic findings in bone scan.

MATERIALS AND METHODS

We retrospectively reviewed clinical records of patients referred for bone scintigraphy with the clinical diagnosis of CRPS during the period December 2006 until February 2011. Patients were classified into 4 distinct subgroups according to the presence of specific symptoms namely sensory subgroup, sudomotor and/or edema subgroup, vasomotor subgroup and finally motor and/or trophic changes subgroup. We looked specifically for the correlation between these specific symptoms and scintigraphic bone findings.

RESULTS

37 patients were referred for bone scintigraphy with the clinical diagnosis of CRPS and were enrolled in the study. The presence of vasomotor symptoms and (motor and/or trophic changes) was significantly higher in patients with positive bone scintigraphy (P value 0.0133, 0.018 respectively). There was no other statistically significant correlation between the presence of specific symptoms or symptom subgroups on one hand and the result of bone scintigraphy on the other hand.

CONCLUSIONS

The probability of positive bone scintigraphy increased significantly in patients with vasomotor symptoms and in patients with motor and/or trophic changes. This may contribute to the reported variability of the diagnostic performance of bone scintigraphy in CRPS patients.

Substance P signaling controls mast cell activation, degranulation, and nociceptive sensitization in a rat fracture model of complex regional pain syndrome

BACKGROUND

Patients with complex regional pain syndrome have increased tryptase in the skin of the affected extremity indicating mast cell (MC) accumulation and degranulation, processes known to be mediated by substance P (SP). The dysregulation of SP release from primary afferent neurons is characteristic of complex regional pain syndrome. The authors hypothesized that SP acting through the neurokinin-1 receptor results in mast cell accumulation, degranulation, and nociceptive sensitization in a rat model of complex regional pain syndrome.

METHODS

Groups of 6-10 rats underwent tibia fracture and hind limb casting for 4 weeks, and the hind paw skin was harvested for histologic and immunohistochemical analysis. The effects of a selective neurokinin-1 receptor antagonist (LY303870) and of direct SP intraplantar injection were measured. Dermal MC degranulation induced by sciatic nerve stimulation and the effects of LY303870 on this process were investigated. Finally, the antinociceptive effects of acute and chronic treatment with a MC degranulator (48/80) were tested.

RESULTS

The authors observed that fracture caused MC accumulation, activation, and degranulation, which were inhibited by LY303870; the percentage of MCs in close proximity to peptidergic nerve fibers increased after fracture; electrical stimulation caused MC activation and degranulation, which was blocked by LY303870; intraplantar SP-induced MC degranulation and acute administration of 48/80 caused MC degranulation and enhanced postfracture nociception, but MC-depleted animals showed less sensitization.

CONCLUSIONS

These results indicate that facilitated peptidergic neuron-MC signaling after fracture can cause MC accumulation, activation, and degranulation in the injured limb, resulting in nociceptive sensitization.

The effectiveness and cost evaluation of pain exposure physical therapy and conventional therapy in patients with complex regional pain syndrome type 1. Rationale and design of a randomized controlled trial

BACKGROUND

Pain Exposure Physical Therapy is a new treatment option for patients with Complex Regional Pain Syndrome type 1. It has been evaluated in retrospective as well as in prospective studies and proven to be safe and possibly effective. This indicates that Pain Exposure Physical Therapy is now ready for clinical evaluation. The results of an earlier performed pilot study with an n = 1 design, in which 20 patients with Complex Regional Pain Syndrome type 1 were treated with Pain Exposure Physical Therapy, were used for the design and power calculation of the present study.After completion and evaluation of this phase III study, a multi-centre implementation study will be conducted.The aim of this study is to determine whether Pain Exposure Physical Therapy can improve functional outcomes in patients with Complex Regional Pain Syndrome type 1.

METHODS/DESIGN

This study is designed as a single-blinded, randomized clinical trial. 62 patients will be randomized with a follow-up of 9 months to demonstrate the expected treatment effect. Complex Regional Pain Syndrome type 1 is diagnosed in accordance with the Bruehl/International Association for the Study of Pain criteria. Conventional therapy in accordance with the Dutch guideline will be compared with Pain Exposure Physical Therapy. Primary outcome measure is the Impairment level SumScore, restricted version.

DISCUSSION

This is the first randomized controlled study with single blinding that has ever been planned in patients with Complex Regional Pain Syndrome type 1 and does not focus on a single aspect of the pain syndrome but compares treatment strategies based on completely different pathophysiological and cognitive theories.

SPECT/CT versus MRI in patients with nonspecific pain of the hand and wrist - a pilot study

BACKGROUND

Hand and wrist pain is a diagnostic challenge for hand surgeons and radiologists due to the complex anatomy of the involved small structures. The American College of Radiology recommends MRI as the study of choice in patients with chronic wrist pain if radiographs are negative. Lately, state-of-the-art SPECT/CT systems have been introduced and may help in the diagnosis of this selected indication.

MATERIALS AND METHODS

This retrospective study included 21 patients with nonspecific pain of the hand/wrist. The diagnosis of nonspecific wrist pain was made by the referring hand surgeon based on patient history, clinical examination, plain radiography and clinical guidelines. All patients received planar early-phase imaging and late-phase SPECT/CT imaging as well as MRI. Lesions were divided into major (causative) and minor (not causative) pathologies according to clinical follow-up. Furthermore, oedema-like bone marrow changes seen on MRI were compared with focally increased tracer uptake seen on SPECT/CT images.

RESULTS

MRI yielded a quite high sensitivity (0.86), but a low specificity (0.20). In contrast, SPECT/CT yielded a high specificity (1.00) and a low sensitivity (0.71). Oedema-like bone marrow changes were detected in 15 lesions in 11 patients. In ten lesions with bone marrow oedema on MRI, foci of elevated tracer uptake were detected on SPECT/CT. Overall, MRI was more sensitive, but SPECT/CT was more specific in the evaluation of causative pathologies.

CONCLUSION

In this initial comparison, SPECT/CT showed higher specificity than MRI in the evaluation of causative pathologies in patients with nonspecific wrist pain. However, MRI was more sensitive. Thus, SPECT/CT was shown to be a useful problem-solving tool in the diagnostic work-up of these patients.

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.

Still's Disease and Recurrent Complex Regional Pain Syndrome Type-I: The First Description

Complex regional pain syndrome (CRPS) is a chronic neuropathic pain disorder characterized by neuropathic pain associated with local edema and changes suggestive of autonomic involvement such as altered sweating, skin color, and skin temperature of the affected region. CRPS was described associated with several diseases, such as trauma, psychiatric conditions, and cancer. However, no case associated with Still's disease has been previously described. In this paper, the authors describe the first case of CRPS associated with Still's disease.

Peripheral trauma induced dystonia or post-traumatic syndrome?

The relationship between peripheral trauma and dystonia has been debated for more than a century but the issue still remains controversial. There are passionate supporters and detractors of the association and both the groups have their own arguments. This review aims to critically evaluate those arguments and presents current understanding of this association. In the process, the relevant case series and scientific papers exploring this subject have been discussed. Upon careful review of available literature coupled with their own experience, the authors believe that peripheral trauma can predispose to abnormal posturing of a body part after variable intervals. To call this posturing a "post-traumatic dystonia" might be premature and the term "post-traumatic syndrome" can be used instead. More work is needed to unravel the pathophysiology of this post-traumatic syndrome.

Role of neuropeptide, cytokine, and growth factor signaling in complex regional pain syndrome

OBJECTIVE

Complex regional pain syndrome (CRPS) patients exhibit multiorgan pathology and inflammatory changes after limb trauma. The objective of this study was to identify how neuro-cutaneous signaling is facilitated after fracture and examine how this altered signaling contributes to the development of CRPS-like changes in the injured limb.

DESIGN AND METHODS

These studies used a rat tibia fracture model that reliably generates hindpaw warmth, edema, increased spontaneous protein extravasation, allodynia, unweighting, and periarticular bone loss, a symptom complex resembling the vascular, nociceptive, and bone sequelae observed in early CRPS. Substance P (SP)-evoked extravasation responses, EIA and PCR assays, and immunohistochemical techniques were used to evaluate post-fracture up-regulation of neuro-cutaneous inflammatory signaling. A SP NK1 receptor antagonist was used to inhibit CRPS-like changes in the fracture model.

RESULTS

In the rat fracture model the SP-evoked extravasation and edema responses were enhanced. SP NK1 receptor expression also increased in the microvascular endothelial cells in the fracture hindpaw skin, leading us to postulate that NK1 receptor up-regulation mediates the facilitated extravasation and edema responses observed after SP injection. The NK1 receptor antagonist LY303870 reversed hindpaw warmth, edema, increased vascular permeability, allodynia, and unweighting observed after tibia fracture in rats. There was also increased keratinocyte proliferation and NK1 receptor expression in the fracture hindpaw. Similar to the rat fracture model, we have observed increased epidermal thickness and keratinocyte NK1 expression in skin biopsies from CRPS patients. There was an up-regulation of inflammatory cytokine expression in the rat hindpaw skin and in keratinocytes at 4 weeks post-fracture. These inflammatory mediators appear to play a crucial role in the development of pain behavior after fracture, as we have repeatedly demonstrated that inhibition of cytokine, and NGF signaling prevents the allodynia and attenuates unweighting at 4 weeks post-fracture. LY303870 treatment also reversed post-fracture keratinocyte proliferation, suggesting that SP might be acting as an intermediate mediator in the inflammatory cascade by causing the up-regulation of inflammatory proteins that can directly sensitize nociceptors in the skin and joints.

CONCLUSIONS

Collectively, these data suggest that neuro-cutaneous signaling is up-regulated and can mediate inflammatory changes observed in the hindpaw skin of the fracture rat model and in human CRPS skin. Future translational and clinical studies mapping these inflammatory changes may identify novel therapeutic targets for preventing post-traumatic pain from transitioning into chronic CRPS.

Movement disorders in complex regional pain syndrome

About 25% of the patients with complex regional pain syndrome (CRPS) suffer movement disorders, including loss of voluntary control, bradykinesia, dystonia, myoclonus, and tremor. These movement disorders are generally difficult to manage and add considerably to the disease burden. Over the last years, interesting findings have emerged that show how tissue or nerve injury may induce spinal plasticity (central sensitization), which alters sensory transmission and sensorimotor processing in the spinal cord and is associated with disinhibition. These changes, in turn, set the stage for the development of movement disorders seen in CRPS. There are no randomized control studies on the treatment of movement disorders in CRPS but findings from fundamental and clinical research suggest that strategies that enhance the central inhibitory state may benefit these patients.

A hypothesis for the cause of complex regional pain syndrome-type I (reflex sympathetic dystrophy): pain due to deep-tissue microvascular pathology

Complex regional pain syndrome-type I (CRPS-I; reflex sympathetic dystrophy) is a chronic pain condition that usually follows a deep-tissue injury such as fracture or sprain. The cause of the pain is unknown. We have developed an animal model (chronic post-ischemia pain) that creates CRPS-I-like symptomatology. The model is produced by occluding the blood flow to one hind paw for 3 hours under general anesthesia. Following reperfusion, the treated hind paw exhibits an initial phase of hyperemia and edema. This is followed by mechano-hyperalgesia, mechano-allodynia, and cold-allodynia that lasted for at least 1 month. Light microscopic analyses and electron microscopic analyses of the nerves at the site of the tourniquet show that the majority of these animals have no sign of injury to myelinated or unmyelinated axons. However, electron microscopy shows that the ischemia-reperfusion injury produces a microvascular injury, slow-flow/no-reflow, in the capillaries of the hind paw muscle and digital nerves. We propose that the slow-flow/no-reflow phenomenon initiates and maintains deep-tissue ischemia and inflammation, leading to the activation of muscle nociceptors, and the ectopic activation of sensory afferent axons due to endoneurial ischemia and inflammation. These data, and a large body of clinical evidence, suggest that in at least a subset of CRPS-I patients, the fundamental cause of the abnormal pain sensations is ischemia and inflammation due to microvascular pathology in deep tissues, leading to a combination of inflammatory and neuropathic pain processes. Moreover, we suggest a unifying idea that relates the pathogenesis of CRPS-I to that of CRPS-II. Lastly, our hypothesis suggests that the role of the sympathetic nervous system in CRPS-I is a factor that is not fundamentally causative, but may have an important contributory role in early-stage disease.

Fracture induces keratinocyte activation, proliferation, and expression of pro-nociceptive inflammatory mediators

Tibia fracture in rats results in chronic vascular and nociceptive changes in the injured limb resembling complex regional pain syndrome (CRPS) and up-regulates expression of interleukin 1β (IL-1β), interleukin IL-6 (IL-6), tumor necrosis factor-α (TNF-α), and nerve growth factor-β (NGF-β) in the hindpaw skin. When fractured rats are treated with cytokine or NGF inhibitors nociceptive sensitization is blocked. Because there is no leukocyte infiltration in the hindpaw skin we postulated that resident skin cells produce the inflammatory mediators causing nociceptive sensitization after fracture. To test this hypothesis rats underwent distal tibia fracture and hindlimb casting for 4 weeks, then the hindpaw skin was harvested and immunostained for keratin, cytokines and NGF. BrdU staining was used to evaluate cell proliferation. Hindpaw nociceptive thresholds, edema, and temperature were tested before and up to 96h after intraplantar injections of IL-6 and TNF-α. Tibia fracture caused keratinocyte activation, proliferation, and up-regulated IL-1β, IL-6, TNF-α and NGF-β protein expression in the hindpaw keratinocytes. Local injections of IL-6 and TNF-α induced hindpaw mechanical allodynia lasting for several days and modest increases in temperature and edema. These data indicate that activated keratinocytes proliferate and express IL-1β, IL-6, TNF-α, and NGF-β after fracture and that excess amounts of inflammatory mediators in the skin cause sustained nociceptive sensitization. This is the first study demonstrating in vivo keratinocyte expression of IL-6, TNF-α and NGF-β in a CRPS model and we postulate that the keratinocyte is the primary cellular source for the inflammatory signals mediating cutaneous nociceptive sensitization in early CRPS.

Complex regional pain syndrome type I: neuropathic or not?

Complex regional pain syndrome (CRPS) is clinically characterized by pain, abnormal regulation of blood flow and sweating, edema of skin and subcutaneous tissues, active and passive movement disorders, and trophic changes. It is classified as type I (reflex sympathetic dystrophy) and type II (causalgia). CRPS cannot be reduced to one system or to one mechanism only. In the past decades, there has been absolutely no doubt that complex regional pain syndromes have to be classified as neuropathic pain disorders. This situation changed when a proposal to redefine neuropathic pain states was recently published, which resulted in an exclusion of CRPS from neuropathic pain disorders. We analyzed the strength of the scientific evidence that supports the neuropathic nature of complex regional pain syndromes.

Mannitol as salvage treatment for Complex Regional Pain Syndrome Type I

INTRODUCTION

Complex Regional Pain Syndrome Type I (CRPS I) is a continuation of symptoms and signs due to a pathological exaggerated reaction in an extremity of the human body after an injury or operation. Although the clinical picture of CRPS I in the majority of patients is well known, the underlying pathophysiology remains unclear. In The Netherlands, intravenous mannitol administration used as hydroxyl radical scavenger for patients who do not respond to conservative treatment of CRPS I is advocated but little evidence supports this salvage strategy. In this study the effect of mannitol as salvage medication was evaluated in a well-defined multimodal step-up treatment protocol.

PATIENTS AND METHODS

A consecutive group of 68 adult patients with persistent CRPS I was analysed, who underwent a total of 100 mannitol infusions. The effect of treatment was considered per sign and per symptom according to the Veldman et al. criteria for CRPS I.

RESULTS

Overall improvement of CRPS I after mannitol treatment was successful in 24% after 1 week, and in 30% after 1 month. Mannitol treatment had some effect in patients with initially warm CRPS I in contrast to patients with cold CRPS I (OR=6.30 with CI [2.37-16.75]). Also patients with CRPS I at the upper extremity had more benefit than patients with CRPS I at the lower extremity (OR=3.26 with CI [1.34-7.93]). Poor results of mannitol treatment were associated with cold CRPS I (p<0.001), chronic CRPS I (p=0.04) and multiple mannitol treatments (p=0.04).

CONCLUSION

Mannitol did not significantly contribute to the overall success of treatment in patients with CRPS I. Patients, presenting with acute, warm CRPS I in the upper extremity may have some benefit.

Frequencies of polymorphisms in cytokines, neurotransmitters and adrenergic receptors in patients with complex regional pain syndrome type I after distal radial fracture

OBJECTIVES

The complex regional pain syndrome type I (CRPS I) is one of the main complications after a fracture of the distal radius. The underlying pathology is not fully understood. Different theories have been put forward to explain the pathogenesis of this disease, some including genetic models. The aim of this study was to find a possible genetic involvement in the occurrence of CRPS I.

METHODS

We tested for known single nucleotide polymorphisms in cytokines, adrenergic receptors, and inflammatory neuropeptides in a cohort of patients at risk to develop CRPS I after a distal radius fracture. Subjective pain and functional parameters were recorded during the course of 1 year after trauma.

RESULTS

Fifteen of 163 patients with fractures of the distal radius were diagnosed with CRPS I according to the International Association for the Study of Pain research criteria. A significant association was detected for the rs1048101 polymorphism of the alpha1a-adrenoceptor. All other tested variants were not associated with CRPS I. Patients with CRPS I fared worse in all functional tests compared with the control group.

DISCUSSION

This study suggests the rs1048101 single nucleotide polymorphism within the alpha1a-adrenoceptor as one risk factor for the development of CRPS I after the distal radius fracture.

Complex regional pain syndrome after hand surgery

Complex regional pain syndrome (CRPS) after an emergent or elective upper extremity surgery may complicate recovery, delay return to work, diminish health-related quality of life, and increase the likelihood of poor outcomes and/or litigation. CRPS after hand surgery is not uncommon and may complicate postoperative care. Early diagnosis and treatment of CRPS is critical for optimal patient outcomes. This article discusses the diagnosis, physiology, and management of postsurgical CRPS that occurs after hand surgery.

Effect of vitamin C on prevention of complex regional pain syndrome type I in foot and ankle surgery

BACKGROUND

The public health cost impact of complex regional pain syndrome type I (CRPS I) is considerable in both emergency and scheduled orthopaedic surgery. We proposed to assess the effectiveness of vitamin C in prevention of CRPS I in foot and ankle surgery.

METHODS

We carried out a "before-after" quasi-experimental study comparing two chronologically successive groups without (Group I: July 2002-June 2003) and with (Group II: July 2003-June 2004) preventive 1g daily vitamin C treatment. All patients having surgery on the foot or ankle were enrolled, with the exception of diabetic foot cases. Several factors were analysed: sex, age, type of pathology, history of CRPS I, psychological context, tourniquet time, and cast immobilisation time.

RESULTS

420 feet (392 patients) were included in the study: 185 in Group I, 235 in Group II. CRPS I occurred in 18 cases in Group I (9.6%) and 4 cases in Group II (1.7%) (p<10(-4)), with history of CRPS I as a significantly correlated factor (relative risk=10.4). The psychological context (anxio-depressive state) showed a (sub-significant) tendency to increase the risk of CRPS I (relative risk=2.6).

CONCLUSION

Vitamin C has been shown to be effective in preventing CRPS I secondary to wrist fracture, but few data are available with respect to foot and ankle cases. The present study demonstrates the effectiveness of vitamin C in preventing CRPS I of the foot and ankle-a frequent complication in our control group (9.6%). The authors recommend preventive management by vitamin C.

The NALP1 inflammasome controls cytokine production and nociception in a rat fracture model of complex regional pain syndrome

Tibia fracture followed by limb immobilization in rats evokes nociceptive and vascular changes resembling complex regional pain syndrome type I (CRPS I). Previously we observed that substance P (SP) and interleukin-1beta (IL-1beta) signaling contribute to chronic regional nociceptive sensitization in this model. It is known that inflammasome multi-protein complexes containing caspase-1 and NALP1 are involved in the activation of the IL-1beta family of pro-nociceptive cytokines expressed in skin and other tissues. Therefore, we hypothesized that SP activated inflammasomes might contribute to mechanical allodynia after fracture. Using this model we observed that: (1) inflammasome components and products NALP1, caspase-1, IL-1beta and IL-18 were present in low levels in normal skin, but expression of all these was strongly up-regulated after fracture, (2) NALP1, caspase-1 and IL-1beta were co-expressed in keratinocytes, and the number of NALP1, caspase-1, and IL-1beta positive cells dramatically increased at 4 weeks post-fracture, (3) LY303870, an NK1 receptor antagonist, effectively blocked fracture-induced up-regulation of activated inflammasome components and cytokines, (4) IL-1beta and IL-18 intraplantar injection induced mechanical allodynia in normal rats, and (5) both a selective caspase-1 inhibitor and an IL-1 receptor antagonist attenuated fracture-induced hindpaw mechanical allodynia. Collectively, these data suggest that NALP1 containing inflammasomes activated by NK1 receptors are expressed in keratinocytes and contribute to post-traumatic regional nociceptive sensitization. These findings highlight the possible importance of neuro-cutaneous signaling and innate immunity mechanisms in the development of CRPS.

Regulation of peripheral blood flow in complex regional pain syndrome: clinical implication for symptomatic relief and pain management

BACKGROUND

During the chronic stage of Complex Regional Pain Syndrome (CRPS), impaired microcirculation is related to increased vasoconstriction, tissue hypoxia, and metabolic tissue acidosis in the affected limb. Several mechanisms may be responsible for the ischemia and pain in chronic cold CPRS.

DISCUSSION

The diminished blood flow may be caused by either sympathetic dysfunction, hypersensitivity to circulating catecholamines, or endothelial dysfunction. The pain may be of neuropathic, inflammatory, nociceptive, or functional nature, or of mixed origin.

SUMMARY

The origin of the pain should be the basis of the symptomatic therapy. Since the difference in temperature between both hands fluctuates over time in cold CRPS, when in doubt, the clinician should prioritize the patient's report of a persistent cold extremity over clinical tests that show no difference. Future research should focus on developing easily applied methods for clinical use to differentiate between central and peripheral blood flow regulation disorders in individual patients.

Intravenous magnesium for complex regional pain syndrome type 1 (CRPS 1) patients: a pilot study

OBJECTIVES

To explore the feasibility of intravenous magnesium administration as a potential candidate intervention for a large size trial in Complex Regional Pain Syndrome Type 1 (CRPS 1).

DESIGN

Randomized clinical trial.

SETTING

Outpatient pain clinic.

PATIENTS

Ten CRPS 1 patients.

INTERVENTIONS

Eight patients received 70 mg/kg magnesium sulphate infusions in 4 hours for 5 days. For blinding purposes, 2 patients received equal amount NaCl 0.9% solutions (data not analyzed or presented). Interventions were accompanied by standardized physical therapy.

OUTCOME MEASURES

Pain was assessed using an 11-point Box scale (three times daily for a week) and the McGill Pain Questionnaire. Skin sensitivity was measured with the Semmes Weinstein Monofilaments, (other) impairments with the Impairment Level Sumscore. In addition, functional limitations (Radboud Skills Questionnaire, questionnaire rising and sitting down) and quality of life (Short Form-36 [SF-36], EuroQol) were evaluated. Assessments were performed at baseline, 1, 3, 6, and 12 weeks after intervention.

RESULTS

Mild systemic side effects were experienced and the infusions were locally well tolerated. Pain was significantly reduced at all follow up compared with baseline (T1: P = 0.01, T3: P = 0.04, T6: P = 0.02, T12: P = 0.02). McGill sensory subscale improved significantly at T1 (number of words chosen: P = 0.03 and pain rating index: P = 0.03). Impairment level (P = 0.03) and quality of life (EuroQol P = 0.04, SF-36 physical P = 0.01) were significantly improved at T12. No improvement was found for skin sensitivity and functional limitations.

CONCLUSION

Intravenous magnesium significantly improved pain, impairment and quality of life and was well tolerated. The results of this pilot study are encouraging and suggest that magnesium IV as a treatment in CRPS 1 should be further explored in a large size formal trial design.

Post-junctional facilitation of Substance P signaling in a tibia fracture rat model of complex regional pain syndrome type I

Tibia fracture in rats evokes nociceptive, vascular, and bone changes resembling complex regional pain syndrome (CRPS). Substance P (SP) signaling contributes to the hindpaw warmth, increased vascular permeability, and edema observed in this model, suggesting that neurogenic inflammatory responses could be enhanced after fracture. Four weeks after tibia fracture we measured SP and calcitonin gene-related peptide (CGRP) protein levels in the sciatic nerve and serum. Hindpaw skin extravasation responses and SP receptor (NK1), CGRP receptor (calcitonin receptor-like receptor, CRLR) and neutral endopeptidase (NEP) protein levels were also determined. Gene expression levels of these peptides, receptors, and peptidase were examined in the DRG and skin. Spontaneous and intravenous SP-evoked extravasation responses were increased ipsilateral, but not contralateral to the fracture. Fracture increased SP and CGRP gene expression in the ipsilateral L4,L5 DRG and neuropeptide protein levels in the sciatic nerve and in serum, but had no effect on electrically evoked SP and CGRP release. NK1 receptor expression was increased in the ipsilateral hindpaw skin keratinocytes and endothelial cells after injury, but CRLR and NEP expression were unchanged. Fracture also increased epidermal thickness, but had no effect on epidermal skin neurite counts. These results demonstrate that spontaneous and intravenous SP-evoked extravasation responses are enhanced in the ipsilateral hindlimb after fracture and that fracture chronically increases the expression of endothelial and keratinocyte NK1 receptors in the injured limb. We postulate that SP activation of these up-regulated NK1 receptors results in skin warmth, protein leakage, edema, and keratinocyte proliferation in the injured limb.

Systemic inflammatory mediators in post-traumatic complex regional pain syndrome (CRPS I) - longitudinal investigations and differences to control groups

OBJECTIVES

The Complex Regional Pain Syndrome I (CRPS I) is a disease that might affect an extremity after trauma or operation. The pathogenesis remains yet unclear. It has clinical signs of severe local inflammation as a result of an exaggerated inflammatory response but neurogenic dysregulation also contributes to it. Some studies investigated the role inflammatory mediators and cytokines; however, few longitudinal studies exist and control groups except healthy controls were not investigated yet.

METHODS

To get further insights into the role of systemic inflammatory mediators in CRPS I, we investigated a variety of pro-, anti-, or neuro-inflammatory mediators such as C-Reactive Protein (CRP), White Blood Cell Count (WBC), Interleukins 4, 6, 8, 10, 11, 12 (p70), Interferon gamma, Tumor-Necrosis-Factor alpha (TNF-a) and its soluble Receptors I/II, soluble Selectins (E,L,P), Substance-P (SP), and Calcitonin Gene-Related Peptide (CGRP) at different time points in venous blood from patients with acute (AC) and chronic (CC) CRPS I, patients with forearm fractures (FR), with neuralgia (NE), and from healthy volunteers (C).

RESULTS

No significant changes for serum parameters investigated in CRPS compared to control groups were found except for CC/C (CGRP p = 0.007), FR/C (CGRP p = 0.048) and AC/CC (IL-12 p = 0.02; TNFRI/II p = 0.01; SP p = 0.049). High interindividual variations were observed. No intra- or interindividual correlation of parameters with clinical course (e.g. chronification) or outcome was detectable.

CONCLUSION

Although clinically appearing as inflammation in acute stages, local rather than systemic inflammatory responses seem to be relevant in CRPS. Variable results from different studies might be explained by unpredictable intermittent release of mediators from local inflammatory processes into the blood combined with high interindividual variabilities. A clinically relevant difference to various control groups was not notable in this pilot study. Determination of systemic inflammatory parameters is not yet helpful in diagnostic and follow-up of CRPS I.

The efficacy of manual lymphatic drainage therapy in the management of limb edema secondary to reflex sympathetic dystrophy

The objective of this study is to investigate the efficacy of manual lymphatic drainage (MLD) therapy in edema secondary to the reflex sympathetic dystrophy (RSD). A total of 34 patients were allocated randomly into two groups. All of the patients undertook nonstreoidal anti-inflammatory drug, physical therapy and therapeutic exercise program for 3 weeks. Patients in study group undertook MLD therapy additionally. Then the patients continued 2-month maintenance period with recommended home programs. Volumetric measurements pain scores and functional measurements were assessed at baseline, after treatment and 2 months after the treatment. After treatment, improvement in edema was statistically significant in the study group but not in the control group. At follow-up, with respect to baseline, improvements were not significant in both of the groups. Between the groups, difference of the percentage improvements in edema was statistically significant with superiority of MLD group after treatment, but not significant at follow-up. In this pilot study, MLD therapy was found to be beneficial in the management of edema resulted from RSD. Although the long-term results showed tendency towards improvement, the difference was not significant.