Expression of endothelial nitric oxide synthase and endothelin-1 in skin tissue from amputated limbs of patients with complex regional pain syndrome

Amputation for Complex Regional Pain Syndrome: Meta-Analysis and Validation of a Histopathology Scoring System

OBJECTIVE

Pathology can provide crucial insights into the etiology of disease. The goal of this review is to evaluate the rigor of histopathology reports of Complex Regional Pain Syndrome (CRPS).

METHODS

A systematic search of multiple databases identified papers that described amputation for CRPS with pathology findings. Control pathology articles were randomly chosen from the same journals. Landmark articles in Surgical Pathology were previously identified. Papers were categorized by the use of histology: Anatomic (microscopic description), Diagnostic (binary result), and Substrate (special studies only). A novel Histopathology Score assigned 1 point for each of 10 History elements and 15 Pathology elements. All articles were scored and analyzed by appropriate statistics.

RESULTS

The search identified 22 CRPS, 50 Control and 50 Landmark articles. Multivariable analysis of the Pathology Score showed a significantly higher score for Anatomic vs Non-Anatomic papers (Incidence Rate Ratio (IRR) 1.54, P < .001) and Landmark vs CRPS articles (IRR 1.39, P value .003). CRPS papers reported some elements infrequently: diagnostic criteria (31.8%), routine stain (50%), any clinic-pathologic correlation (40.9%), and sample size >2 (27.3%).

CONCLUSIONS

The Pathology Score is a useful quality assessment tool to evaluate studies. As expected, Anatomic papers scored significantly higher than Non-Anatomic papers. CRPS papers had small sample sizes (median 1) and infrequent reporting of diagnostic criteria, routine stain, any clinical pathologic correlation. These particular elements are crucial for analyzing and reviewing pathologic features. The analysis explains why it is quite difficult to write a meaningful systematic review of CRPS histology at this time.

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.

Quality of life after amputation in patients with advanced complex regional pain syndrome: a systematic review

The majority of included studies (8 out of 11, n = 54) supported the concept of considering amputation for selected, unresponsive cases of complex regional pain syndrome (CRPS) as a justifiable alternative to an unsuccessful multimodality nonoperative option.Of patients who underwent amputation, 66% experienced improvement in quality of life (QOL) and 37% were able to use a prosthesis, 16% had an obvious decline in QOL and for 12% of patients, no clear details were given, although it was suggested by authors that these patients also encountered deterioration after amputation.Complications of phantom limb pain, recurrence of CRPS and stump pain were predominant risks and were noticed in 65%, 45% and 30% of cases after amputation, respectively and two-thirds of patients were satisfied.Amputation can be considered by clinicians and patients as an option to improve QOL and to relieve agonizing, excruciating pain of severe, resistant CRPS at a specialized centre after multidisclipinary involvement but it must be acknowledged that evidence is limited, and the there are risks of aggravating or recurrence of CRPS, phantom pain and unpredictable consequences of rehabilitation.Amputation, if considered for resistant CRPS, should be carried out at specialist centres and after MDT involvement before and after surgery. It should only be considered if requested by patients with poor quality of life who have failed to improve after multiple treatment modalities.Further high quality and comprehensive research is needed to understand the severe form of CRPS which behaves differently form less severe stages. Cite this article: EFORT Open Rev 2019;4:533-540. DOI: 10.1302/2058-5241.4.190008.

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.

Cutaneous immunopathology of long-standing complex regional pain syndrome

BACKGROUND

Both increased mast cells numbers and raised immune mediator concentrations indicate immune activation in the affected skin of patients with early complex regional pain syndrome (CRPS), but little is known about regional immune cell involvement in late-stage CRPS. The aim of the current study was to determine skin immune cell populations in long-standing CRPS.

METHODS

Using 6-mm skin punch biopsies from CRPS-affected and non-affected tissues, and a combination of chemical and immunofluorescence staining, we examined the density and function of key cell populations including mast cells, epidermal Langerhans cells (LCs) and tissue resident T-cells.

RESULTS

We found no significant differences in either overall immune cell infiltrates, or mast cell density between CRPS-affected and non-affected sub-epidermal tissue sections, contrasting recent findings in early CRPS by other groups. However, CD1a(+) LC densities in the epidermal layer were significantly decreased in affected compared to non-affected CRPS limbs (p < 0.01). T-cell clones isolated from CRPS-affected sub-epidermal tissues displayed a trend towards increased IL-13 production in ELISPOT assays when compared to T-cells isolated from non-affected areas, suggesting a Th2 bias.

CONCLUSIONS

Immune cell abnormalities are maintained in late-stage CRPS disease as manifest by changes in epidermal LC density and tissue resident T-cell phenotype.

Antiallodynic effect through spinal endothelin-B receptor antagonism in rat models of complex regional pain syndrome

Complex regional pain syndrome (CRPS) is a very complicated chronic pain disorder that has been classified into two types (I and II). Endothelin (ET) receptors are involved in pain conditions at the spinal level. We investigated the role of spinal ET receptors in CRPS. Chronic post-ischemia pain (CPIP) was induced in male Sprague-Dawley rats as a model for CRPS-I by placing a tourniquet (O-ring) at the ankle joint for 3h, and removing it to allow reperfusion. Ligation of L5 and L6 spinal nerves to induce neuropathic pain was performed as a model for CRPS-II. After O-ring application and spinal nerve ligation, the paw withdrawal threshold was significantly decreased at injured sites. Intrathecal administration of the selective ET-B receptor antagonist BQ 788 dose-dependently increased the withdrawal threshold in both CRPS-I and CRPS-II. In contrast, ET-A receptor antagonist BQ 123 did not affect the withdrawal threshold in either CRPS type. The ET-1 levels of plasma and spinal cord increased in both CRPS types. Intrathecal BQ 788 decreased the spinal ET-1 level. These results suggest that ET-1 is involved in the development of mechanical allodynia in CRPS. Furthermore, the ET-B receptor appears to be involved in spinal cord-related CRPS.

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.

Morphological macrovascular alterations in complex regional pain syndrome type I demonstrated by increased intima-media thickness

Background

Although intima-media thickness (IMT) was increased in several inflammatory diseases, studies investigating whether the inflammatory processes lead to macrovascular alteration with increased IMT in complex regional pain syndrome (CRPS) lack.

Methods

Using ultrasound (high-resolution B-mode), we compared bilaterally the IMT of the common carotid artery (CCA-IMT), the radial artery (RA-IMT), the brachial artery (BRA-IMT) and the quotient Q_RA/CCA, in CRPS type I (n=17), peripheral nerve injury (PNI, n=17) and pain-free controls (PFC, n=22, matched to CRPS by gender, age and traditional cardiovascular risk factors). Statistics: Spearman’s correlation, paired t-test, ANOVA (p<0.05).

Results

Compared to PFC, RA-IMT were significantly increased in both patient groups bilaterally (mean±standard deviation, CRPS affected side vs. PFC dominant side: 0.32±0.08 mm vs. 0.19±0.08 mm, p<0.001; PNI affected side vs. PFC dominant side: 0.27±0.09 mm vs. 0.19±0.08 mm, p< 0.05; CRPS non-affected side vs. PFC non-dominant side: 0.30±0.10 mm vs. 0.19±0.09 mm, p<0.001; PNI non-affected side vs. PFC non-dominant side: 0.25±0.10 mm vs. 0.19±0.09 mm, p<0.05) and Q_RA/CCA (CRPS affected-side vs. PFC dominant side: 0.49±0.12 vs. 0.30±0.11, p<0.001; PNI affected side vs. PFC dominant side: 0.41±0.10 vs. 0.30±0.11, p<0.05; CRPS non-affected side vs. PFC non-dominant side: 0.43±0.19 vs. 0.30±0.13, p<0.001; PNI non-affected side vs. PFC non-dominant side: 0.39±0.14 vs. 0.30±0.13, p<0.05), and BRA-IMT - only on the affected side in CRPS (CRPS: 0.42±0.06 mm vs. PFC: 0.35±0.08 mm; p<0.05). In CRPS, Q_RA/CCA was significantly higher on the affected side compared to PNI (p<0.05). However, only CRPS displayed within-group side-to-side differences with a significantly increased RA-IMT and Q_RA/CCA on the affected side (p<0.05). The CCA-IMT was comparable between all groups and sides.

Conclusions

The increased IMT of peripheral arteries in CRPS suggests ongoing inflammatory process. Until now, only endothelial dysfunction has been reported. The presented morphological macrovascular alterations might explain the treatment resistance of some CRPS patients.

Efficacy and safety of ketamine in patients with complex regional pain syndrome: a systematic review

Despite being a recognized clinical entity for over 140 years, complex regional pain syndrome (CRPS) remains a difficult-to-treat condition. While there have been multiple therapies explored in the treatment of CRPS, NMDA antagonists such as ketamine continue to hold significant interest because of their potential ability to alter the central sensitization noted in chronic pain states. The objective of this review is to identify published literature for evidence of the efficacy and safety of ketamine in the treatment of CRPS. PubMed and the Cochrane Controlled Trials Register were searched (final search 26 May 2011) using the MeSH terms 'ketamine', 'complex regional pain syndrome', 'analgesia' and 'pain' in the English literature. The manuscript bibliographies were then reviewed to identify additional relevant papers. Observational trials were evaluated using the Agency for Healthcare Research and Quality criteria; randomized trials were evaluated using the methodological assessment of randomized clinical trials. The search methodology yielded three randomized, placebo-controlled trials, seven observational studies and nine case studies/reports. In aggregate, the data available reveal ketamine as a promising treatment for CRPS. The optimum dose, route and timing of administration remain to be determined. Randomized controlled trials are needed to establish the efficacy and safety of ketamine and to determine its long-term benefit in CRPS.

Pathophysiology of the spreading of complex regional pain syndrome revisited: a case report

OBJECTIVE

  To determine if there is a relationship in our patient developing complex regional pain syndrome from a jellyfish and its subsequent spread to the contralateral side.

METHODS

  Data bases were searched using PubMed and Ovid. Keywords searched include "complex regional pain syndrome,""jelly fish," and "pathophysiology."

RESULTS

  This patient was successfully treated with a spinal cord stimulator implantation with bilateral lead placement at thoracic spine (T9) stimulating her lower extremities in addition to the leads that had already been placed in her cervical spine for her upper extremities.

CONCLUSION

  Definite knowledge of the pathophysiology of complex regional pain syndrome would allow better identification of risk factors for the development of this condition after trauma. This patient is at higher risk of developing complex regional pain syndrome and should avoid surgeries (such as knee and wrist surgeries) and high risk physical activities.

Vasomotor disturbances in complex regional pain syndrome--a review

Complex regional pain syndromes (CRPS) are characterized by vascular disturbances primary affecting the microcirculation in the distal part of the involved extremity. In the acute stage inhibited sympathetic vasoconstriction and exaggerated neurogenic inflammation driven by central and peripheral mechanisms, respectively, seem to be the major pathophysiological mechanisms inducing vasodilation. During the chronic course of the disease as well as early in some patients vasoconstriction dominates the clinical picture induced by changes in the microcirculation itself such as endothelial dysfunction or vascular hyperreactivity, whereas sympathetic vasoconstrictor activity returns and neurogenic inflammation is less severe. It can be suggested that the interaction between different mechanisms underlying vasomotor disturbances as well as the severity of each single mechanism in the individual patient have a great impact on the variety of the overall clinical picture in CRPS. Irrespective of the underlying pathophysiology, measurements of skin temperature differences between the affected and the contralateral extremity can serve as a diagnostic tool in CRPS, in particular when sensitivity and specificity is increased by considering dynamic alterations in skin temperature asymmetries.

Nitric oxide and pain: 'Something old, something new'

Challenges have emerged following the revival of nitric oxide (NO) from 'something old', a simple gas derived from nitrogen and oxygen with a role in the early stages of evolution, into 'something new', an endogenously formed biological mediator regulating a wide variety of physiological functions. Although pain is a common sensation, it encompasses multiple neurobiologic components, of which NO is only one. In pain research, the study of NO is complicated by convoluted problems related mostly to the effects of NO, which are pro- or anti-nociceptive depending on the circumstances. This dual function reflects the multi-faceted roles of the NO molecule described in physiology. This review covers current information about NO and its implications in pain mechanisms. In addition, it follows the pain pathways, demonstrating the role of NO in peripheral nociceptive transmission as well in central sensitization. This knowledge may provide the scientific basis for developing new drugs that are indicated for different types of pain, drugs that may be related to the chemical links of NO. A comprehensive approach to understanding the effects of NO will help clinicians identify novel agents that combine the pharmacological profile of native drugs with a controllable manner of NO release. Inhibitors of NO synthesis may have analgesic effects and would be of interest for treating inflammatory and neuropathic pain. Unfortunately, only a few of these compounds have reached the stage of clinical pain trials.

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.