Sympathetic dysfunction as a temporary phenomenon in acute posttraumatic CRPS I

Complex Regional Pain Syndrome. A Comprehensive Review on Neuroplastic Changes Supporting the Use of Non-invasive Neurostimulation in Clinical Settings

Background: Complex regional pain syndrome (CRPS) is a rare debilitating disorder characterized by severe pain affecting one or more limbs. CRPS presents a complex multifactorial physiopathology. The peripheral and sensorimotor abnormalities reflect maladaptive changes of the central nervous system. These changes of volume, connectivity, activation, metabolism, etc., could be the keys to understand chronicization, refractoriness to conventional treatment, and developing more efficient treatments. Objective: This review discusses the use of non-pharmacological, non-invasive neurostimulation techniques in CRPS, with regard to the CRPS physiopathology, brain changes underlying chronicization, conventional approaches to treat CRPS, current evidence, and mechanisms of action of peripheral and brain stimulation. Conclusion: Future work is warranted to foster the evidence of the efficacy of non-invasive neurostimulation in CRPS. It seems that the approach has to be individualized owing to the integrity of the brain and corticospinal function. Non-invasive neurostimulation of the brain or of nerve/muscles/spinal roots, alone or in combination with conventional therapy, represents a fertile ground to develop more efficient approaches for pain management in CRPS.

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

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

Mental load during cognitive performance in complex regional pain syndrome I

BACKGROUND

Complex regional pain syndrome (CRPS) is associated with deficits in limb recognition. The purpose of our study was to determine whether mental load during this task affected performance, sympathetic nervous system activity or pain in CRPS patients.

METHODS

We investigated twenty CRPS-I patients with pain in the upper extremity and twenty age- and sex-matched healthy controls. Each participant completed a limb recognition task. To experimentally manipulate mental load, the presentation time for each picture varied from 2 s (greatest mental load), 4, 6 to 10 s (least mental load). Before and after each run, pain intensity was assessed. Skin conductance was recorded continuously.

RESULTS

Patients with CRPS did not differ from controls in terms of limb recognition and skin conductance reactivity. However, patients with CRPS reported an increase in pain during the task, particularly during high mental load and during the latter stages of the task. Interestingly, state anxiety and depressive symptoms were also associated with increases in pain intensity during high mental load.

CONCLUSIONS

These findings indicate that high mental load intensifies pain in CRPS. The increase of pain in association with anxiety and depression indicates a detrimental effect of negative affective states in situations of high stress and mental load in CRPS.

SIGNIFICANCE

The effects of mental load need to be considered when patients with CRPS-I are investigated for diagnostic or therapeutic reasons.

Orofacial complex regional pain syndrome: pathophysiologic mechanisms and functional MRI

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

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.

[Complex regional pain syndrome in nerve root compression and after spinal surgery]

Complex regional pain syndrome (CRPS) is an extremely painful and partially disabling disease. It often occurs secondary to trauma, but also spontaneously. The emergence of CRPS has been reported following nerve root compression and/or spinal surgery, but its incidence is unknown. In this article, the present knowledge about the incidence of CRPS in the context of nerve root compression and spine surgery is reviewed and therapeutic and diagnostic consequences are discussed.

New Concepts in Complex Regional Pain Syndrome

Despite the severe pain and disability associated with complex regional pain syndrome (CRPS), the lack of understanding of the pathophysiological mechanisms supporting this enigmatic condition prevents the rational design of new therapies, a situation that is frustrating to both the physician and the patient. The review highlights some of the mechanisms thought to be involved in the pathophysiology of CRPS in preclinical models and CRPS patients, with the ultimate goal that understanding these mechanisms will lead to the design of efficacious, mechanism-based treatments available to the clinic.

Bimodal Modulation of Ipsilateral Spinal-Coeruleo-Spinal Pathway in CRPS: A Novel Model for Explaining Different Clinical Features of the Syndrome

OBJECTIVE

The objective is to present a hypothesis to explain the sensory, autonomic, and motor disturbances associated with complex regional pain syndrome (CRPS) syndrome.

METHODS

The author reviewed the available and relevant literature, which was supplemented with research on experimental animal models, with a focus on how they may translate into humans, particularly in areas about pathophysiologic mechanisms of CRPS.

RESULTS

We propose that different CRPS subtypes may result from facilitative or inhibitory influences exerted by the spinal-coeruleo-spinal pathway in three sites at the spinal cord: the dorsal horn (DH), intermediolateral cell column (IML) and ventral horn (VH). A facilitatory influence over DH may have a pronociceptive effect that explains exacerbated pain, sensory disturbances, and spreading sensitization and neuroinflammation. Conversely, a facilitatory influence over preganglionic neurons located in IML cell column may increase sympathetic outflow with peripheral vasoconstriction, which leads to cold skin, ipsilateral limb ischaemia, and sympathetically maintained pain (SMP). For patients presenting with these symptoms, a descending inhibitory influence would be predicted to result in decreased sympathetic outflow and warm skin, as well as impairment of peripheral vasoconstrictor reflexes. Finally, a descending inhibitory influence over VH could explain muscle weakness and decreased active range of motion, while also facilitating motor reflexes, tremor and dystonia.

CONCLUSIONS

The proposed model provides a mechanistically based diagnostic scheme for classifying and explaining the sensory, autonomic and motor disturbances associated with CRPS syndrome.

Potential risk factors for the onset of complex regional pain syndrome type 1: a systematic literature review

Anaesthetists in the acute and chronic pain teams are often involved in treating Complex Regional Pain Syndromes. Current literature about the risk factors for the onset of Complex Regional Pain Syndrome Type 1 (CRPS 1) remains sparse. This syndrome has a low prevalence, a highly variable presentation, and no gold standard for diagnosis. In the research setting, the pathogenesis of the syndrome continues to be elusive. There is a growing body of literature that addresses efficacy of a wide range of interventions as well as the likely mechanisms that contribute to the onset of CRPS 1. The objective for this systematic search of the literature focuses on determining the potential risk factors for the onset of CRPS 1. Eligible articles were analysed, dated 1996 to April 2014, and potential risk factors for the onset of CRPS 1 were identified from 10 prospective and 6 retrospective studies. Potential risk factors for the onset of CRPS 1 were found to include being female, particularly postmenopausal female, ankle dislocation or intra-articular fracture, immobilisation, and a report of higher than usual levels of pain in the early phases of trauma. It is not possible to draw definite conclusions as this evidence is heterogeneous and of mixed quality, relevance, and weighting strength against bias and has not been confirmed across multiple trials or in homogenous studies.

Enhanced pain and autonomic responses to ambiguous visual stimuli in chronic Complex Regional Pain Syndrome (CRPS) type I

Cortical reorganisation of sensory, motor and autonomic systems can lead to dysfunctional central integrative control. This may contribute to signs and symptoms of Complex Regional Pain Syndrome (CRPS), including pain. It has been hypothesised that central neuroplastic changes may cause afferent sensory feedback conflicts and produce pain. We investigated autonomic responses produced by ambiguous visual stimuli (AVS) in CRPS, and their relationship to pain. Thirty CRPS patients with upper limb involvement and 30 age and sex matched healthy controls had sympathetic autonomic function assessed using laser Doppler flowmetry of the finger pulp at baseline and while viewing a control figure or AVS. Compared to controls, there were diminished vasoconstrictor responses and a significant difference in the ratio of response between affected and unaffected limbs (symmetry ratio) to a deep breath and viewing AVS. While viewing visual stimuli, 33.5% of patients had asymmetric vasomotor responses and all healthy controls had a homologous symmetric pattern of response. Nineteen (61%) CRPS patients had enhanced pain within seconds of viewing the AVS. All the asymmetric vasomotor responses were in this group, and were not predictable from baseline autonomic function. Ten patients had accompanying dystonic reactions in their affected limb: 50% were in the asymmetric sub-group. In conclusion, there is a group of CRPS patients that demonstrate abnormal pain networks interacting with central somatomotor and autonomic integrational pathways.

Imaging and clinical evidence of sensorimotor problems in CRPS: utilizing novel treatment approaches

Inflammation and altered autonomic function are diagnostic signs and symptoms of Complex Regional Pain Syndrome. In the acute stages these are commonly at their most florid accompanied by severe pain and reduced function. Understandably this has directed research towards potential peripheral drivers for the causal mechanisms of this condition. In particular this is now focused on the inflammatory process and the potential role of autoantibodies. More subtle changes also occur in terms of altered tactile processing within the affected limb, disturbances in body perception and motor planning problems that become more evident as the condition progresses. Through careful clinical observation and neuro-imaging techniques, these changes are now thought to be associated with altered cortical processing that includes reorganisation of both the motor and sensory maps. Furthermore, there appears to be a close relationship between the intensity of pain experienced and the extent of cortical re-organisation. This increased knowledge around the peripheral and central mechanisms that may be operating in CRPS has been used to inform novel therapeutic approaches. We discuss here the presenting signs and symptoms of CRPS, with particular focus on sensory and motor changes and consider which mechanisms may drive these changes. Finally, we consider the emerging therapeutic options designed to correct these aberrant mechanisms.

Effect of muscle load tasks with maximal isometric contractions on oxygenation of the trapezius muscle and sympathetic nervous activity in females with chronic neck and shoulder pain

Background

Sympathetic nervous activity contributes to the maintenance of muscle oxygenation. However, patients with chronic pain may suffer from autonomic dysfunction. Furthermore, insufficient muscle oxygenation is observed among workers with chronic neck and shoulder pain. The aim of our study was to investigate how muscle load tasks affect sympathetic nervous activity and changes in oxygenation of the trapezius muscles in subjects with chronic neck and shoulder pain.

Methods

Thirty females were assigned to two groups: a pain group consisting of subjects with chronic neck and shoulder pain and a control group consisting of asymptomatic subjects. The participants performed three sets of isometric exercise in an upright position; they contracted their trapezius muscles with maximum effort and let the muscles relax (Relax). Autonomic nervous activity and oxygenation of the trapezius muscles were measured by heart rate variability (HRV) and Near-Infrared Spectroscopy.

Results

Oxyhemoglobin and total hemoglobin of the trapezius muscles in the pain group were lower during the Relax period compared with the control group. In addition, the low frequency / high frequency (LF/HF) ratio of HRV significantly increased during isometric exercise in the control group, whereas there were no significant changes in the pain group.

Conclusions

Subjects with neck and shoulder pain showed lower oxygenation and blood flow of the trapezius muscles responding to isometric exercise, compared with asymptomatic subjects. Subjects with neck and shoulder pain also showed no significant changes in the LF/HF ratio of HRV responding to isometric exercise, which would imply a reduction in sympathetic nervous activity.

Complex regional pain syndrome following spine surgery: clinical and prognostic implications

BACKGROUND

Complex regional pain syndrome (CRPS) has been reported following spinal surgery, but its frequency after spinal surgery is unknown. The aim of this study was to determine the frequency of spinal surgery preceding CRPS and to examine these patients regarding the course of the disease and prognostic factors.

METHODS

We examined 35 CRPS patients regarding the symptoms and signs of CRPS, the type of CRPS (I or II), the origin and grade of the disease, the type of surgeries prior to CRPS onset, the course of the disease, and the therapies following diagnosis of CRPS.

RESULTS

In 6 patients, CRPS began during the postoperative course (lumbar spine surgery, n = 5; cervical spine surgery, n = 1). Four of these patients suffered from CRPS II. The course of the disease in the 6 patients was not different from that of patients with CRPS of other origins. First symptoms of CRPS could be observed 1-14 days after surgery.

CONCLUSIONS

CRPS is a rare complication after spinal surgery, but spinal surgery precedes the onset of CRPS of the lower limb in almost one-third of the cases. The first typical symptoms of CRPS emerge within 2 weeks after spinal surgery.

Neurological diseases and pain

Chronic pain is a frequent component of many neurological disorders, affecting 20-40% of patients for many primary neurological diseases. These diseases result from a wide range of pathophysiologies including traumatic injury to the central nervous system, neurodegeneration and neuroinflammation, and exploring the aetiology of pain in these disorders is an opportunity to achieve new insight into pain processing. Whether pain originates in the central or peripheral nervous system, it frequently becomes centralized through maladaptive responses within the central nervous system that can profoundly alter brain systems and thereby behaviour (e.g. depression). Chronic pain should thus be considered a brain disease in which alterations in neural networks affect multiple aspects of brain function, structure and chemistry. The study and treatment of this disease is greatly complicated by the lack of objective measures for either the symptoms or the underlying mechanisms of chronic pain. In pain associated with neurological disease, it is sometimes difficult to obtain even a subjective evaluation of pain, as is the case for patients in a vegetative state or end-stage Alzheimer's disease. It is critical that neurologists become more involved in chronic pain treatment and research (already significant in the fields of migraine and peripheral neuropathies). To achieve this goal, greater efforts are needed to enhance training for neurologists in pain treatment and promote greater interest in the field. This review describes examples of pain in different neurological diseases including primary neurological pain conditions, discusses the therapeutic potential of brain-targeted therapies and highlights the need for objective measures of pain.

CRPS I following artificial disc surgery: case report and review of the literature

We report a case of type 1 complex regional pain syndrome (CRPS I) of the left leg following the implantation of an artificial disc type in the L4/5 segment of the lumbar spine using a midline left-sided retroperitoneal approach. This approach included the mobilisation of the sympathetic trunk with incision and resection of the intervertebral disc. The perioperative and immediate postoperative periods were uneventful, but on the second postoperative day the patient complained of a progressive allodynia of the whole left leg in combination with weakness of the limb. Neurological examination did not reveal any radicular deficit or paresis. A sympathetic reaction following the mobilisation of the sympathetic trunk during the ventral preparation of the spine was suspected and investigated further. A diagnosis of CRPS I was proposed, and the patient was treated with analgesia, co-analgesics for pain alienation, and systemic corticosteroid therapy. A computed tomography-guided sympathetic block and lymphatic drainage were performed. Following conservative orthopaedic rehabilitation therapy, the degree of pain, allodynia, weakness, and swelling were reduced and the condition of the patient was ameliorated. The cost-benefit ratio of spinal arthroplasty is still controversial. The utility of this paper is to debate a possible cause of a painful complication, which can invalidate the results of a successful operation.

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.

Sympathetic dysfunction in long-term complex regional pain syndrome

OBJECTIVE

Malfunction of the sympathetic nervous system (SNS) is common in early complex regional pain syndrome type I (CRPS I). This study was designed to evaluate the function of the SNS in patients with chronic CRPS I and to correlate the obtained data with hand function measurements.

MATERIALS AND METHODS

Thirty-two patients of both the sexes in whom the diagnosis of CRPS I of the upper extremity had been established for at least 3 years before they were included in the study. Besides a hand outcomes questionnaire [Michigan Hand Outcome Questionnaire, (MHQ)] the patients underwent a standardized testing of the peripheral sympathetic nervous system (pSNS) using laser Doppler flowmetry (LDF).

RESULTS

Mean time since initial diagnosis was 4.6+/-2.1 years. The mean MHQ score of the affected limb was 57.3+/-17 compared with 69.4+/-13.7 for the unaffected hand (P=0.002). Twenty patients (62.5%) still demonstrated pathologic results regarding the pSNS function (mean sympathetic reflex 0.18+/-0.11, normal range>0.38). We found no statistically significant correlation between pSNS function either with the clinical outcome as measured by MHQ (r=0.246; P=0.175), or with the level of pain (r=0.132; P=0.473).

CONCLUSIONS

Even 5 years after the diagnosis of CRPS I of the upper extremity we detected significant impairments of the pSNS in nearly two thirds of our patients. Patients still have pain and present with a significant deterioration of their hand function in comparison with the not affected hand. In our study we could not identify any correlation between pSNS function and clinical outcome as measured by MHQ.

Lumbar sympathetic blockade in children with complex regional pain syndromes: a double blind placebo-controlled crossover trial

BACKGROUND

Sympathetic blockade is used in the management of complex regional pain syndromes in children, but there are no data on the efficacy or mechanism(s) by which it produces pain relief. The purpose of this study is to compare the efficacy of lidocaine administered by lumbar sympathetic to IV route.

METHODS

Under general anesthesia, children with unilateral lower limb complex regional pain syndromes received catheters along the lumbar sympathetic chain. In a double-blind placebo-controlled crossover design, patients received IV lidocaine and lumbar sympathetic saline or lumbar sympathetic lidocaine and IV saline. Spontaneous and evoked pain ratings and sensory thresholds were assessed before and after these two lidocaine/saline doses and between routes of lumbar sympathetic blockade and IV.

RESULTS

Twenty-three patients, ages 10-18 yr, were enrolled. There was evidence for reduction of mean pain intensity of allodynia to brush (mean -1.4, 95% confidence interval [CI] -2.5 to -0.3) and to pinprick temporal summation (mean -1.3, 95% CI -2.5 to -0.2) with lidocaine treatment via the lumbar sympathetic blockade compared to IV route. Lumbar sympathetic blockade also produced significant reduction in pain intensity compared to pretreatment values of allodynia to brush, pinprick and pinprick temporal summation and verbal pain scores. IV lidocaine did not produce significant changes in spontaneous and evoked pain intensity measurements compared to pretreatment values. There were no carryover effects as assessed by route-by-period interaction.

CONCLUSIONS

Under the conditions of this study, the results provide some direct evidence that a component of pain may be mediated by abnormal sympathetic efferent activity.

Current management of reflex sympathetic dystrophy syndrome (complex regional pain syndrome type I)

Although no major advances have occurred in the curative treatment of reflex sympathetic dystrophy syndrome (RSDS), new pathogenic insights may soon lead to innovative approaches, which may also prove effective in alleviating some forms of neuropathic pain. Preventing nerve compression and ischemia-reperfusion injury constitute valuable measures for preventing RSDS. Vitamin C administration can also prevent RSDS, together with clonidine in high-risk patients. Short-term glucocorticoid therapy has been found effective in preventing RSDS after stroke but has not been evaluated in other situations. Beneficial effects of bisphosphonates have been documented in several placebo-controlled trials. Placebo-controlled trials of ketamine and spinal cord stimulation are in order to confirm or refute the promising results obtained in open-label studies. Mirror visual feedback was introduced recently for the rehabilitation of patients with RSDS but needs to be evaluated in randomized controlled trials.

Pathophysiology of complex regional pain syndrome

Complex regional pain syndrome (CRPS) most often follows injury to peripheral nerves or their endings in soft tissue. A combination of prostanoids, kinins and cytokines cause peripheral nociceptive sensitization. In time, the Mg(2+) block of the N-methyl-D-aspartate receptor is removed, pain transmission neurons (PTN) are altered by an influx of Ca(2+) that activates kinases for excitation and phosphatases for depression, activity-dependent plasticity that alters the firing of PTN. In time, these neurons undergo central sensitization that lead to a major physiological change of the autonomic, pain and motor systems. The role of the immune system and the sickness response is becoming clearer as microglia are activated following injury and can induce central sensitization while astrocytes may maintain the process.