Reflex sympathetic dystrophy: facts and hypotheses

The Central Regulation of Bone Mass: Genetic Evidence and Molecular Bases

The alternation of resorption of preexisting bone by the osteoclasts followed by de novo bone formation by osteoblasts is called bone modeling during childhood and bone remodeling during adulthood. A central question raised by this physiological process that is fundamental to longitudinal growth during childhood and adolescence and that is attacked at the other end of life in the context of osteoporosis is to know how it is regulated. This question was rejuvenated in the late 1990s and early 2000s years when the application of mouse genetics made it feasible to test whether there were new endocrine determinants of bone (re)modeling. Addressing this question, taking into account fundamental cell biology features of bone led to the hypothesis that there should be a coordinated control of bone growth/mass, energy metabolism, and reproduction. Testing genetically and molecularly, this hypothesis revealed that, in vivo, the adipocyte-derived hormone leptin is a powerful inhibitor of bone mass accrual following its signaling in the brain. This chapter details the molecular bases and biological relevance of this regulation of bone mass accrual by leptin.

Impact of polyphenols on mast cells with special emphasis on the effect of quercetin and luteolin

Polyphenols are ubiquitous in food and have long been recognized to possess antioxidant, anti-inflammatory and anticancer activities. Mast cells (MCs) are implicated in the pathogenesis of inflammatory diseases, allergy, autoimmunity and cancer. MCs derive from hematopoietic progenitor cells, reside virtually in all vascularized tissue and are activated by crosslinking of FceRI-bound IgE (at very high affinity: 1 × 10¹⁰ M^-1) with multivalent antigen. MCs in cytoplasmic granules release preformed chemical mediators, and also they can release lipid mediators and cytokines/chemokines without degranulation.

Luteolin, 3’,4’,5,7-tetrahydroxyflavone, is a flavonoid contained in many kinds of plants including vegetables and fruits. This anti-oxidant product inhibits interleukin (IL)-6, IL-8 and vascular endothelial growth factor (VEGF) production from tumor necrosis factor (TNF)-triggered keratinocytes, and is a candidate for use in alternative therapies in the treatment of inflammatory skin disorders.

Quercetin (3,3’,4’,5,7-pentahydroxyflavone) is a ubiquitous flavonoid which exhibits anti-cancer, anti-oxidative and anti-inflammatory properties and causes a reduction in the availability of nitrite that influences vascular function. Quercetin exerts physiological functions though the interaction with phosphatidylinositol-3-phosphate kinase (PI3K), mitogen-activated protein kinase (MAPK), extracellular signal regulated kinase (ERK), kinase (MEK) 1, and others, and has a negative effect on FceRI cross-linking and other activating receptors on mast cells. In this article we report for the first time the interrelationship between mast cells and polyphenols.

Change in pulse transit time in the lower extremity after lumbar sympathetic ganglion block: an early indicator of successful block

Objective

To investigate the change in pulse transit time (PTT)—time between the electrocardiographic R wave and the highest point of the corresponding plethysmographic wave—after lumbar sympathetic ganglion block (LSGB) and evaluate PTT as an indicator of successful LSGB.

Methods

Sixteen cases of sympathetically mediated lower extremity neuropathic pain treated with LSGB were studied. Correlations between the changes in PTT and temperature were used to identify the cutoff point indicating successful LSGB.

Results

PTT rate of change at 5 min relative to the baseline PTT (dPTT5/PTT0) significantly correlated positively with the temperature change at 20 min (correlation coefficient 0.734). The dPTT5/PTT0 ratios of the Success and Failure groups were 6.46 ± 2.81% and 2.77 ± 1.72%, respectively. The dPTT5/PTT0 cutoff indicating successful LSGB, based on receiver operating characteristic curve analysis, was 4.23%.

Conclusion

PTT measurement 5 min after local anesthetic injection was an early, objective indicator of successful or failed LSGB.

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.

Treatment of complex regional pain syndrome with stellate ganglion local anesthetic blockade: a case report of one patient's experiences with traditional bupivacaine HCl and liposome bupivacaine

Complex regional pain syndrome (CRPS) is a poorly understood, debilitating disorder characterized by severe chronic pain in an affected limb or region of the body. This case presentation is the first to describe the effectiveness and prolonged duration of the effect of liposome bupivacaine in stellate ganglion block for CRPS.

Complex regional pain syndrome type I: a comprehensive review

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Endocrinology of bone/brain crosstalk

Bone metabolism is regulated by the action of two skeletal cells: osteoblasts and osteoclasts. This process is controlled by many genetic, hormonal and lifestyle factors, but today more and more studies have allowed us to identify a neuronal regulation system termed 'bone-brain crosstalk', which highlights a direct relationship between bone tissue and the nervous system. The first documentation of an anatomic relationship between nerves and bone was made via a wood cut by Charles Estienne in Paris in 1545. His diagram demonstrated nerves entering and leaving the bones of a skeleton. Later, several studies were conducted on bone innervation and, as of today, many observations on the regulation of bone remodeling by neurons and neuropeptides that reside in the CNS have created a new research field, that is, neuroskeletal research.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Complex regional pain syndrome type 1 in a pediatric patient: Case report

Complex regional pain syndrome type 1 is one of the causes of morbidity of childhood which is also named reflex symphathetic dystrophia. The syndrome is characterized with regional pain and vasomotor, sudomotor and sensory changes in the distal parts of the extremities involved. Complex regional pain syndrome type 1 shows difference in children in terms of clinical picture and imaging methods compared to adults. The most important point is that the prognosis is generally better in children if early diagnosis and treatment is provided. On the other hand, causes including presence of psychological factors or less contribution of imaging methods in children lead to delayed diagnosis or erroneous diagnosis. In this article, a 10 year-old male patient who was diagnosed with complex regional pain syndrome type 1 was described. Thus, we aimed to remind clinicians that this syndrome should also be kept in mind in the differential diagnosis of pain in children.

Complex regional pain syndrome of the knee - a case report

Background

Persistent unexplained pain around the knee can be a perplexing problem. Reports of complex regional pain syndrome involving primarily knee have been published, yet complex regional pain syndrome of the knee is infrequently included in differential diagnosis of pain out of proportion.

Case presentation

A 54 year old female presented to the physiotherapy outpatient department with complains of severe anterior knee pain and stiffness, persisting for more than 2 months post arthroscopic medial plical excision. The patient met the criteria for establishing a probable diagnosis of complex regional pain syndrome (CRPS) knee. Pressure algometre, goniometric measurements and knee outcome survey activities of daily living scale were used to document any changes. This patient was managed for a period of four sessions using graded desensitization therapy, TENS and mobilisation with feedback. Patient showed marked improvement in range of movement (ROM), hypersensitivity, pain and function.

Conclusion

Meticulous examination, early diagnosis and prompt treatment resulted in a quick improvement in the patient’s condition.

Diagnostic performance of three-phase bone scan for complex regional pain syndrome type 1 with optimally modified image criteria

PURPOSE

Although the three-phase bone scan (TBPS) is one of the widely used imaging studies for diagnosing complex regional pain syndrome type I (CRPS-1), there is some controversy regarding the TPBS image criteria for CRPS-1. In this study, we modified the image criteria using image pattern and quantitative analysis in the patients diagnosed using the most recent consensus clinical diagnostic criteria.

MATERIALS AND METHODS

The study included 140 patients with suspected CRPS-1 (CRPS-1, n = 79; non-CRPS, n = 61; mean age 39 ± 15 years) who underwent TPBS. The clinical diagnostic criteria for CRPS-1 revised by the Budapest consensus group were used for confirmative diagnosis. Patients were classified according to flow/pool and delayed uptake (DU) image patterns, and the time interval between the initiating event and TPBS (TIevent-scan). Quantitative analysis for lesion-to-contralateral ratio (LCR) was performed. Modified TPBS image criteria were created and evaluated for optimal diagnostic performance.

RESULTS

Both increased and decreased periarticular DU were significant image findings for CRPS-1 (CRPS-1 positive-rate = 73% in the increased DU group, 75% in the decreased DU group). The TIevent-scan did not differ significantly between the different image pattern groups. Quantitative analysis revealed an LCR of 1.43 was the optimal cutoff value for CRPS-1 and diagnostic performance was significantly improved in the increased DU group (area under the curve = 0.732). Given the modified image criteria, the sensitivity and specificity of TPBS for diagnosing CRPS-1 were 80% and 72%, respectively.

CONCLUSIONS

Optimally modified TPBS image criteria for CRPS-1 were suggested using image pattern and quantitative analysis. With the criteria, TPBS is an effective imaging study for CRPS-1 even with the most recent consensus clinical diagnostic criteria.

The roles of the sympathetic nervous system in osteoporotic diseases: A review of experimental and clinical studies

With the rapid aging of the world population, the issue of skeletal health is becoming more prominent and urgent. The bone remodeling mechanism has sparked great interest among bone research societies. At the same time, increasing clinical and experimental evidence has driven attention towards the pivotal role of the sympathetic nervous system (SNS) in bone remodeling. Bone remodeling is thought to be partially controlled by the hypothalamus, a process which is mediated by the adrenergic nerves and neurotransmitters. Currently, new knowledge about the role of the SNS in the development and pathophysiology of osteoporosis is being generated. The aim of this review is to summarize the evidence that proves the involvement of the SNS in bone metabolism and to outline some common osteoporotic diseases that occur under different circumstances. The adrenergic signaling pathway and its neurotransmitters are involved to various degrees of importance in the development of osteoporosis in postmenopause, as well as in spinal cord injury, depression, unloading and the complex regional pain syndrome. In addition, clinical and pharmacological studies have helped to increase the comprehension of the adrenergic signaling pathway. We try to individually examine the contributions of the SNS in osteoporotic diseases from a different perspective. It is our hope that a further understanding of the adrenergic signaling by the SNS will pave the way for conceptualizing optimal treatment regimens for osteoporosis in the near future.

The Cut-Off Rate of Skin Temperature Change to Confirm Successful Lumbar Sympathetic Block

The purpose of this study was to find the best cut-off value for the rate of change in temperature of the plantar surface of the foot for predicting the success of lumbar sympathetic block (LSB). A total of 185 LSBs were performed on 82 patients via a posterolateral approach under fluoroscopic guidance. Successful LSB was considered to have occurred when changes in the ipsilateral temperature between preblock and post-block were ≥ 2 °C. A receiver operating characteristic (ROC) curve for the minimum rate of temperature change was constructed as a predictor of the onset of a successful LSB. The area under the ROC curve was 0.971 at the rate of 0.4°C/min with a sensitivity of 89.5% and a specificity of 91.8%. Achieving a rate of temperature change of 0.4°C/min within approximately 5 min of the injection of local anaesthetic could be used as an indicator of the onset of successful LSB.

Central control of bone remodelling

The discovery that the brain controls bone remodelling has provided a new paradigm for our understanding of bone biology. This review summarises the genetic, molecular and physiological bases for the central control of bone remodelling and discusses the future directions of this new research field of neuroskeletal biology.

The biochemical origin of pain: the origin of all pain is inflammation and the inflammatory response. Part 2 of 3 - inflammatory profile of pain syndromes

Every pain syndrome has an inflammatory profile consisting of the inflammatory mediators that are present in the pain syndrome. The inflammatory profile may have variations from one person to another and may have variations in the same person at different times. The key to treatment of Pain Syndromes is an understanding of their inflammatory profile. Pain syndromes may be treated medically or surgically. The goal should be inhibition or suppression of production of the inflammatory mediators and inhibition, suppression or modulation of neuronal afferent and efferent (motor) transmission. A successful outcome is one that results in less inflammation and thus less pain. We hereby briefly describe the inflammatory profile for several pain syndromes including arthritis, back pain, neck pain, fibromyalgia, interstitial cystitis, migraine, neuropathic pain, complex regional pain syndrome/reflex sympathetic dystrophy (CRPS/RSD), bursitis, shoulder pain and vulvodynia. These profiles are derived from basic science and clinical research performed in the past by numerous investigators and serve as a foundation to be built upon by other researchers and will be updated in the future by new technologies such as magnetic resonance spectroscopy. Our unifying theory or law of pain states: the origin of all pain is inflammation and the inflammatory response. The biochemical mediators of inflammation include cytokines, neuropeptides, growth factors and neurotransmitters. Irrespective of the type of pain whether it is acute or chronic pain, peripheral or central pain, nociceptive or neuropathic pain, the underlying origin is inflammation and the inflammatory response. Activation of pain receptors, transmission and modulation of pain signals, neuro plasticity and central sensitization are all one continuum of inflammation and the inflammatory response. Irrespective of the characteristic of the pain, whether it is sharp, dull, aching, burning, stabbing, numbing or tingling, all pain arise from inflammation and the inflammatory response. We are proposing a re-classification and treatment of pain syndromes based upon their inflammatory profile.

Permanent sacral nerve stimulation for treatment of functional anorectal pain: report of a case

PURPOSE

Patients with functional anorectal pain in the absence of an organic cause often have symptoms that are resistant to conventional medical and behavioral therapy. This study assessed the use of sacral nerve stimulation in the treatment of this condition.

METHODS

A 56-year-old, female subject with an 18-month history of intermittent severe anorectal pain, in the absence of any evacuatory disorder or gross pathology, underwent temporary then subsequent permanent sacral nerve stimulation. Treatment efficacy was measured by verbal pain scores obtained at baseline, during screening, after screening, and subsequent follow-up.

RESULTS

Temporary sacral nerve stimulation of the left S3 root (3-5 V; 14 Hz; 210 microsec) resulted in total alleviation of the patient's symptoms. A verbal pain score of 10/10 preoperatively was reduced to 0/10 with no adverse effects from stimulation. On completing the trial evaluation, the symptoms of pain returned with a verbal pain score of 10/10. A permanent pulse generator was implanted with a Medtronic 3093 quadripolar electrode lead, placed in the left S3 foramen. Results of chronic stimulation showed that pain symptoms were again abolished with no recurrence of symptoms seen at one-year follow-up (1.3 V; 14 Hz; 210 microsec).

CONCLUSIONS

Sacral nerve stimulation may be of benefit in the treatment of functional anorectal pain resistant to conventional treatments. The mechanism of action is not known. Further prospective evaluation of a series of patients is required using pain scoring, quality of life, and psychologic assessment to aid selection.

The "kick-off" position: a new sign for early diagnosis of complex regional pain syndrome in the leg

BACKGROUND

Complex regional pain syndrome (CRPS) is a clinical entity that develops after a precipitating injury. It involves dysfunction of the sensory, autonomic, and motor systems and frequently is missed on initial presentation. The purpose of this report was to describe a simple clinical sign that can aid in its diagnosis.

METHODS

A retrospective review was conducted of 39 consecutive patients with CRPS type I or II seen in a foot and ankle clinic between October, 2001, and May, 2005. The diagnosis was based on clinical findings.

RESULTS

Twenty-six patients had type I (67%) and 13 patients had type II (33%) CRPS. The most common nerve involved in type II was the superficial peroneal nerve. Each patient, while sitting on the exam table, held the affected extremity with the knee extended against gravity. When the leg was pushed back to a relaxed and suspended position, the patient eventually involuntarily resumed the extended position. This position in which the patients held their legs was termed the "kick-off" position sign. Nine patients were seen at the foot and ankle clinic within 6 weeks of the initial inciting event and had an established "kick-off" position sign within 3 months from the time of injury. The disappearance of this sign correlated with the subsidence of pain.

CONCLUSIONS

Patients with CRPS have variable clinical presentations. The awareness of this simple observation in the right clinical setting should raise the index of suspicion of CRPS in the differential diagnosis. Early treatment of this syndrome is associated with better outcome.

Convergence between bone and energy homeostases: leptin regulation of bone mass

The observation that obesity protects from osteoporosis suggested that energy metabolism and bone mass could be regulated by the same hormones. Testing this hypothesis revealed that leptin regulates bone mass through a hypothalamic relay and using two neural mediators, the sympathetic tone and CART, both acting on one cell type the osteoblast. This review summarizes the genetic and molecular bases of this regulation and discusses its potential clinical implications.

The Role of Nuclear Medicine in the Evaluation of Complex Regional Pain Syndrome Type I

Chronic pain resulting from complex regional pain syndrome type I (CRPS I), formerly referred to as the reflex sympathetic dystrophy syndrome (RSDS), is a diagnostic challenge to the clinician. It involves multiple organ systems, namely peripheral as well as central nervous, vascular, soft tissue, and skeletal. It usually develops as a consequence of trauma, without nerve injury. Signs and symptoms vary depending on the time since the initiating event, and there is no confirmatory histopathologic diagnosis. This article summarizes the current consensus on the classification, pathophysiology, and diagnostic approaches, emphasizing the role of scintigraphy in the management of this multisystem disorder.

The predictive value of additional late blood pool imaging to the three-phase bone scan in the diagnosis of reflex sympathetic dystrophy in hemiplegic patients

Reflex sympathetic dystrophy (RSD) is a relative common sequel after hemiplegia. The diagnosis of RSD in hemiplegic patients presents difficult clinical problems, as the symptoms and signs of RSD are not specific and RSD may be due to reasons other than hemiplegia. Bone scintigraphy has been routinely used for the diagnosis of RSD; however, the optimal acquisition protocols, diagnostic patterns and the utility of quantitation are controversial. This prospective study was conducted to demonstrate the higher predictive value of an additional late blood pool image to the three-phase bone scan compared to the regular three-phase bone scans in RSD patients associated with hemiplegia. Thirty-four RSD patients were enrolled into the study. Bone scans according to the new protocol were obtained for all patients. Those patients with either negative or positive bone scans with no evidence of RSD were followed for 6 months. The patients had positive bone scan findings and were symptomatic at the time of the study. Of these, seven patients (58.3%) subsequently became symptomatic and five patients (41.7%) remained asymptomatic at 6 months. None of the patients with negative bone scans had symptoms of RSD on presentation except one case. We conclude that the addition of a late blood pool image increases the predictive value and has an impact on initiating early treatment in asymptomatic patients.

Tissue hypoxia in complex regional pain syndrome

Untreated complex regional pain syndrome (CRPS) may progress from acute stages with increased hair and nail growth in the affected limb to chronic stages with atrophy of the skin, muscles and bones. The aim of this study was to investigate whether tissue hypoxia could be one mechanism responsible for this late CRPS symptoms. Nineteen patients with CRPS and two control groups (healthy control subjects, surgery patients with edema) participated in this study. Skin capillary hemoglobin oxygenation (HbO(2)) was measured non-invasively employing micro-lightguide spectrophotometry (EMPHO). The EMPHO probe was mounted force-controlled onto the skin of the affected and unaffected hand. HbO(2) was measured at rest and during postischemic reactive hyperemia. HbO(2) did not differ between the right (58.20%+/-1.12) and left (57.79%+/-1.31, ns) hand in control subjects. However, in patients, HbO(2) of the affected side (36.63%+/-2.16) was significantly decreased as compared to the clinically unaffected side (46.35%+/-2.97, P<0.01). As compared to controls, HbO(2) in CRPS was reduced on both sides (P<0.001). Postischemic hyperoxygenation was impaired on the affected side in CRPS (60.81%+/-2.90)--as compared to the unaffected side (67.73%+/-1.50, P<0.04) and to controls (68.63%+/-0.87, P<0.005). The unaffected limb in CRPS did not differ from controls. Despite skin edema, pre- (49.06%+/-2.02) and postsurgery HbO(2) (53.15%+/-4.44, ns) were not different in the second control group. Our results indicate skin hypoxia in CRPS. Impairment of nutritive blood flow in the affected limb may be one factor contributing to atrophy and ulceration in chronic CRPS. The investigation of patients after surgery revealed that edema could not be the only reason for hypoxia.

Bone marrow edema syndrome of the foot: one year follow-up with MR imaging

OBJECTIVE

To describe the MR findings of bone marrow edema syndrome (BMES) of the foot and its evolution at 1 year follow-up.

DESIGN AND PATIENTS

Twenty-five of 32 patients with disabling foot and ankle pain unrelated to trauma diagnosed as BMES when MR imaging demonstrated a bone marrow edema pattern in one or more bones without any radiological or underlying clinical cause, were re-evaluated by MR imaging 1 year later.

RESULTS

On the initial MR examinations an average of 4.7 individual bones were involved by bone marrow edema. Soft tissue edema was present in every patient and joint effusion in 10 patients. MR imaging at 1 year showed resolution of bone edema in 18 patients (72%), partial improvement in five (20%) and no improvement in two (8%). Six patients (24%) developed similar symptoms in the other foot during follow-up. Ten of 17 available plain radiographs showed some loss of radiodensity. Further bone marrow edema developed in bones of the same foot that were initially normal, or in uninvolved distant bone marrow areas in the same affected bone, in six of seven patients on follow-up MR imaging.

CONCLUSIONS

The evolution of the MR findings of BMES of the foot is to complete resolution or partial improvement at 1 year in the majority of cases. Migration to the other foot occurs in up to a quarter of patients.

Reflex sympathetic dystrophy syndrome and neuromediators

Concepts related to the pathophysiology of reflex sympathetic dystrophy syndrome (RSDS) are changing. Although sympathetic influences are still viewed as the most likely mechanism underlying the development and/or perpetuation of RSDS, these influences are no longer ascribed to an increase in sympathetic tone. Rather, the most likely mechanism may be increased sensitivity to catecholamines due to sympathetic denervation with an increase in the number and/or sensitivity of peripheral axonal adrenoceptors. Several other pathophysiological mechanisms have been suggested, including neurogenic inflammation with the release of neuropeptides by primary nociceptive afferents and sympathetic efferents. These neuromediators, particularly substance P, calcitonin gene-related peptide, and neuropeptide Y (NPY), may play a pivotal role in the genesis of pain in RSDS. They induce an inflammatory response (cutaneous erythema and edema) and lower the pain threshold. Neurogenic inflammation at the site of the lesion with neuromediator accumulation or depletion probably contributes to the pathophysiology of RSDS. However, no single neuromediator has been proved responsible, and other hypotheses continue to arouse interest.

Beyond neurons: evidence that immune and glial cells contribute to pathological pain states

Chronic pain can occur after peripheral nerve injury, infection, or inflammation. Under such neuropathic pain conditions, sensory processing in the affected body region becomes grossly abnormal. Despite decades of research, currently available drugs largely fail to control such pain. This review explores the possibility that the reason for this failure lies in the fact that such drugs were designed to target neurons rather than immune or glial cells. It describes how immune cells are a natural and inextricable part of skin, peripheral nerves, dorsal root ganglia, and spinal cord. It then examines how immune and glial activation may participate in the etiology and symptomatology of diverse pathological pain states in both humans and laboratory animals. Of the variety of substances released by activated immune and glial cells, proinflammatory cytokines (tumor necrosis factor, interleukin-1, interleukin-6) appear to be of special importance in the creation of peripheral nerve and neuronal hyperexcitability. Although this review focuses on immune modulation of pain, the implications are pervasive. Indeed, all nerves and neurons regardless of modality or function are likely affected by immune and glial activation in the ways described for pain.

Vascular diseases are the most common cutaneous manifestations of reflex sympathetic dystrophy

Reflex sympathetic dystrophy (RSD) is a chronic pain syndrome with prominent cutaneous findings. Atrophy has been considered to be the most common manifestation of the disease. We catalogued the abnormal skin conditions in RSD by means of chart review. Vascular problems were most common, followed by inflammatory diseases, infections, and atrophic diseases. Atrophic disease accounts for a minority of the skin problems seen in RSD. Most cutaneous complaints were related to vascular disease, particularly edema.

Lumbar sympathetic block for sympathetically maintained pain: changes in cutaneous temperatures and pain perception

Lumbar sympathetic block (LSB) is used in the management of sympathetically maintained pain states. We characterized cutaneous temperature changes over the lower extremities after LSB. Additionally, we examined the effects of iohexol, a radio-opaque contrast medium, on temperature changes and pain relief. After institutional review board approval and written, informed consent, 28 LSBs were studied in 17 patients. Iohexol or normal saline was injected in a randomized, double-blinded fashion before bupivacaine. Lower extremity cutaneous temperatures were measured. Pain, allodynia, interference with daily function, and perceived pain relief were reported in a subset of 15 LSBs for 1 wk after the block. The distal lower extremity ipsilateral to the LSB had the greatest magnitude (8.7 degrees +/- 0.8 degrees C) and rate (1.1 degrees +/- 0.2 degrees C/min) of temperature change. The great toe temperature was within 3 degrees C of core temperature within 35 min after LSB. There were no differences in temperature change between the groups. The iohexol group had greater relief of pain until the morning of the first postblock day (P = 0.002) and longer perceived relief of pain (P = 0.01). The maximum temperature of the great toe correlated with allodynia relief (P = 0.0007). Thus clinicians should expect ipsilateral toe temperatures to increase to within approximately 3 degrees C of core temperature. Iohexol does not alter the efficacy of LSB and may improve relief of symptoms. The magnitude of temperature change may predict relief of allodynia.

IMPLICATIONS

Cutaneous toe temperatures approaching core temperature provide a useful monitor of lumbar sympathetic block and may predict relief of sympathetically maintained pain. Iohexol will not compromise temperature changes or pain relief.