Analysis of peak magnitude and duration of analgesia produced by local anesthetics injected into sympathetic ganglia of complex regional pain syndrome patients

Analgesic efficacy of pre-operative stellate ganglion block on postoperative pain relief: a randomised controlled trial

We undertook a randomised, double-blind, placebo-controlled study to compare the analgesic efficacy of pre-operative stellate ganglion block on postoperative pain relief after upper limb orthopaedic surgery. Patients were administered a 3-ml injection during ultrasound-guided stellate ganglion block; 15 patients received lidocaine 2% and 15 patients received 0.9% saline. Following the block, all patients received standardised general anaesthesia. Postoperative analgesia included regular intravenous diclofenac, paracetamol and patient-controlled analgesia with tramadol for 24 h. Patients were observed at 0, 2, 4, 6, 8, 12 and 24 h after surgery for tramadol consumption, cardiovascular variables and visual analogue scale pain scores at rest and on movement. The mean (SD) hourly tramadol consumption was significantly reduced in the lidocaine group compared with the saline group at 4 h (8.0 (10.1) mg vs 28.0 (12.6) mg, respectively; p = 0.001), 6 h (5.3 (10.8) mg vs 17.3 (12.7) mg, respectively; p = 0.013) and 8 h (5.3 (11.8) mg vs 21.3 (9.1) mg, respectively; p = 0.001). The cumulative 24-h tramadol consumption was 97.3 (16.6) mg in the lidocaine group and 150.6 (26.0) mg in the saline group (p = 0.001). There were significant differences in the pain visual analogue scale at rest at two time points; at 4 h the median (IQR [range]) visual analogue scale scores were 4 (4-6 [2-8]) in the lidocaine group and 5 (4-6 [2-7]) in the saline group (p = 0.03), and at 6 h visual analogue scale scores were 3 (3-4 [3-6]) and 4 (4-6 [2-7]), respectively (p = 0.04). Pain visual analogue scale on movement was lower in the lidocaine group at all time intervals compared with the saline group, but this did not reach statistical significance. The present study has demonstrated a postoperative tramadol-sparing and analgesic effect of pre-operative stellate ganglion block in patients undergoing upper limb orthopaedic surgery under general anaesthesia.

Pulsed radiofrequency treatment of complex regional pain syndrome: a case series

BACKGROUND

Various forms of sympathetic chain neurolysis (sympathectomy) have, at one time or another, held promise as effective treatment options for complex regional pain syndrome (CRPS). Complications, such as worsening pain and the development of new pain syndromes, have prevented sympathectomy from emerging as a standard intervention. In an effort to avoid poor outcomes associated with neurolysis, pulsed radiofrequency (PRF) has been proposed as a potential treatment alternative for a number of chronic neuropathic pain states, including some forms of CRPS.

METHODS

The present report describes three cases in which patients diagnosed with lower extremity CRPS type I obtained substantial and lasting intervals of pain relief following PRF of the lumbar sympathetic chain. Over a period of four years, 14 fluoroscopically guided procedures using PRF lesioning of the lumbar sympathetic chain at L2, L3 and L4 were performed in three individuals with CRPS type I of the lower limb. Outcome measures included pre- and post-treatment self-reported pain and medication requirements.

RESULTS

Substantial pain relief (>50%) was achieved in 91.7% of PRF applications at three months and 83.3% at six months, with some treatments resulting in persistent relief well beyond 12 months. Medication use decreased to a comparable degree, with discontinuation of opiates after all but three treatments.

CONCLUSIONS

PRF lesioning of the lumbar sympathetic chain can be an effective treatment for patients with CRPS type I of the lower extremity, with the potential to provide ≥6 months of substantial pain relief.

Complex regional pain syndrome: From diagnosis to rehabilitation

Complex regional pain syndrome (CRPS) is a debilitating pathology characterised by intense chronic pain associated with vasomotor, sensory and motor dysfunction of the affected limb. Although the pathophysiology of CRPS is not fully understood, it is recognised that inflammatory processes and autonomic dysfunction are involved. These processes are associated with peripheral and central sensitisation as well as changes in brain structure and function, and are reflected in the clinical presentation of CRPS. CRPS management requires an interdisciplinary team and requires the therapeutic approach to be individualised. With regard to pharmacological treatment, bisphosphonates, corticosteroids, ketamine and anticonvulsants have been demonstrated to be effective for CRPS management. Psychotherapy, including cognitive-behavioural therapy, has produced promising results but more studies are needed to confirm its efficacy. Among rehabilitation interventions, there is evidence of the efficacy of physiotherapy and occupational therapy in diminishing CRPS symptoms and achieving a higher level of functioning. In this regard, the rehabilitation modality that seems the most promising according to the actual literature is graded motor imagery, which can help to reverse the maladaptive neuroplasticity occurring in CRPS.

Stimulation of dorsal root ganglia for the management of complex regional pain syndrome: a prospective case series

BACKGROUND

Complex regional pain syndrome (CRPS) is a chronic and progressive pain condition usually involving the extremities and characterized by sensorimotor, vascular, and trophic changes. Spinal cord stimulation (SCS) is an effective intervention for this condition, but is hampered by the technical challenges associated with precisely directing stimulation to distal extremities. Dorsal root ganglia (DRG) may be more effective as a physiological target for electrical modulation due to recruitment of the primary sensory neurons that innervate the painful distal anatomical regions.

METHODS

Eleven subjects diagnosed with uni- or bilateral lower-extremity CRPS were recruited as part of a larger study involving chronic pain of heterogeneous etiologies. Quadripolar epidural leads of a newly developed neurostimulation system were placed near lumbar DRGs using conventional percutaneous techniques. The neurostimulators were trialed; 8 were successful and permanently implanted and programed to achieve optimal pain-paresthesia overlap.

RESULTS

All 8 subjects experienced some degree of pain relief and subjective improvement in function, as measured by multiple metrics. One month after implantation of the neurostimulator, there was significant reduction in average self-reported pain to 62% relative to baseline values. Pain relief persisted through 12 months in most subjects. In some subjects, edema and trophic skin changes associated with CRPS were also mitigated and function improved. Neuromodulation of the DRG was able to provide excellent pain-paresthesia concordance in locations that are typically hard to target with traditional SCS, and the stimulation reduced the area of pain distributions.

CONCLUSIONS

Neuromodulation of the DRG appears to be a promising option for relieving chronic pain and other symptoms associated with CRPS. The capture of discrete painful areas such as the feet, combined with stable paresthesia intensities independent of body position, suggests this stimulation modality may allow more selective and consistent targeting of painful areas than traditional SCS.

Local anaesthetic sympathetic blockade for complex regional pain syndrome

BACKGROUND

This is an update of the original Cochrane review published in The Cochrane Library, 2005, Issue 4, on local anaesthetic blockade (LASB) of the sympathetic chain used to treat complex regional pain syndrome (CRPS).

OBJECTIVES

To assess the efficacy of LASB for the treatment of pain in CRPS and to evaluate the incidence of adverse effects of the procedure.

SEARCH METHODS

We updated searches of the Cochrane Pain, Palliative and Supportive Care Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL) on the Cochrane Library (Issue 11 of 12, 2012), MEDLINE (1966 to 22/11/12), EMBASE (1974 to 22/11/12), LILACS (1982 to 22/11/12), conference abstracts of the World Congresses of the International Association for the Study of Pain (1995 to 2010), and various clinical trial registers (inception to 2012). We also searched bibliographies from retrieved articles for additional studies.

SELECTION CRITERIA

We considered for inclusion randomised controlled trials (RCTs) that evaluated the effect of sympathetic blockade with local anaesthetics in children or adults with CRPS.

DATA COLLECTION AND ANALYSIS

The outcomes of interest were reduction in pain intensity levels, the proportion who achieved moderate or substantial pain relief, the duration of pain relief, and the presence of adverse effects in each treatment arm.

MAIN RESULTS

We included an additional 10 studies (combined n = 363) in this update. Overall we include 12 studies (combined n = 386). All included studies were assessed to be at high or unclear risk of bias.Three small studies compared LASB to placebo/sham. We were able to pool the results from two of these trials (intervention n = 23). Pooling did not demonstrate significant short-term benefit for LASB (in terms of the risk of a 50% reduction of pain scores).Of two studies that investigated LASB as an addition to rehabilitation treatment, the only study that reported pain outcomes demonstrated no additional benefit from LASB.Eight small randomised studies compared sympathetic blockade to another active intervention. Most studies found no difference in pain outcomes between sympathetic block and other active treatments.Only five studies reported adverse effects, all with minor effects reported.

AUTHORS' CONCLUSIONS

This update has found similar results to the original systematic review. There remains a scarcity of published evidence to support the use of local anaesthetic sympathetic blockade for CRPS. From the existing evidence it is not possible to draw firm conclusions regarding the efficacy or safety of this intervention but the limited data available do not suggest that LASB is effective for reducing pain in CRPS.

Shaped magnetic field pulses by multi-coil repetitive transcranial magnetic stimulation (rTMS) differentially modulate anterior cingulate cortex responses and pain in volunteers and fibromyalgia patients

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) has shown promise in the alleviation of acute and chronic pain by altering the activity of cortical areas involved in pain sensation. However, current single-coil rTMS technology only allows for effects in surface cortical structures. The ability to affect activity in certain deep brain structures may however, allow for a better efficacy, safety, and tolerability. This study used PET imaging to determine whether a novel multi-coil rTMS would allow for preferential targeting of the dorsal anterior cingulate cortex (dACC), an area always activated with pain, and to provide preliminary evidence as to whether this targeted approach would allow for efficacious, safe, and tolerable analgesia both in a volunteer/acute pain model as well as in fibromyalgia chronic pain patients.

METHODS

Part 1: Different coil configurations were tested in a placebo-controlled crossover design in volunteers (N = 16). Tonic pain was induced using a capsaicin/thermal pain model and functional brain imaging was performed by means of H2(15)O positron emission tomography - computed tomography (PET/CT) scans. Differences in NRS pain ratings between TMS and sham treatment (NRS(TMS)-NRS(placebo)) which were recorded each minute during the 10 minute PET scans. Part 2: 16 fibromyalgia patients were subjected to 20 multi-coil rTMS treatments over 4 weeks and effects on standard pain scales (Brief Pain Inventory, item 5, i.e. average pain NRS over the last 24 hours) were recorded.

RESULTS

A single 30 minute session using one of 3 tested rTMS coil configurations operated at 1 Hz consistently produced robust reduction (mean 70% on NRS scale) in evoked pain in volunteers. In fibromyalgia patients, the 20 rTMS sessions also produced a significant pain inhibition (43% reduction in NRS pain over last 24 hours), but only when operated at 10 Hz. This degree of pain control was maintained for at least 4 weeks after the final session.

CONCLUSION

Multi-coil rTMS may be a safe and effective treatment option for acute as well as for chronic pain, such as that accompanying fibromyalgia. Further studies are necessary to optimize configurations and settings as well as to elucidate the mechanisms that lead to the long-lasting pain control produced by these treatments.

Complex regional pain syndrome: a review

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

Interventions for treating pain and disability in adults with complex regional pain syndrome

BACKGROUND

There is currently no strong consensus regarding the optimal management of complex regional pain syndrome although a multitude of interventions have been described and are commonly used.

OBJECTIVES

To summarise the evidence from Cochrane and non-Cochrane systematic reviews of the effectiveness of any therapeutic intervention used to reduce pain, disability or both in adults with complex regional pain syndrome (CRPS).

METHODS

We identified Cochrane reviews and non-Cochrane reviews through a systematic search of the following databases: Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects (DARE), Ovid MEDLINE, Ovid EMBASE, CINAHL, LILACS and PEDro. We included non-Cochrane systematic reviews where they contained evidence not covered by identified Cochrane reviews. The methodological quality of reviews was assessed using the AMSTAR tool.We extracted data for the primary outcomes pain, disability and adverse events, and the secondary outcomes of quality of life, emotional well being and participants' ratings of satisfaction or improvement. Only evidence arising from randomised controlled trials was considered. We used the GRADE system to assess the quality of evidence.

MAIN RESULTS

We included six Cochrane reviews and 13 non-Cochrane systematic reviews. Cochrane reviews demonstrated better methodological quality than non-Cochrane reviews. Trials were typically small and the quality variable.There is moderate quality evidence that intravenous regional blockade with guanethidine is not effective in CRPS and that the procedure appears to be associated with the risk of significant adverse events.There is low quality evidence that bisphosphonates, calcitonin or a daily course of intravenous ketamine may be effective for pain when compared with placebo; graded motor imagery may be effective for pain and function when compared with usual care; and that mirror therapy may be effective for pain in post-stroke CRPS compared with a 'covered mirror' control. This evidence should be interpreted with caution. There is low quality evidence that local anaesthetic sympathetic blockade is not effective. Low quality evidence suggests that physiotherapy or occupational therapy are associated with small positive effects that are unlikely to be clinically important at one year follow up when compared with a social work passive attention control.For a wide range of other interventions, there is either no evidence or very low quality evidence available from which no conclusions should be drawn.

AUTHORS' CONCLUSIONS

There is a critical lack of high quality evidence for the effectiveness of most therapies for CRPS. Until further larger trials are undertaken, formulating an evidence-based approach to managing CRPS will remain difficult.

Interventions for treating pain and disability in adults with complex regional pain syndrome

BACKGROUND

There is currently no strong consensus regarding the optimal management of complex regional pain syndrome although a multitude of interventions have been described and are commonly used.

OBJECTIVES

To summarise the evidence from Cochrane and non-Cochrane systematic reviews of the effectiveness of any therapeutic intervention used to reduce pain, disability or both in adults with complex regional pain syndrome (CRPS).

METHODS

We identified Cochrane reviews and non-Cochrane reviews through a systematic search of the following databases: Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects (DARE), Ovid MEDLINE, Ovid EMBASE, CINAHL, LILACS and PEDro. We included non-Cochrane systematic reviews where they contained evidence not covered by identified Cochrane reviews. The methodological quality of reviews was assessed using the AMSTAR tool.We extracted data for the primary outcomes pain, disability and adverse events, and the secondary outcomes of quality of life, emotional well being and participants' ratings of satisfaction or improvement. Only evidence arising from randomised controlled trials was considered. We used the GRADE system to assess the quality of evidence.

MAIN RESULTS

We included six Cochrane reviews and 13 non-Cochrane systematic reviews. Cochrane reviews demonstrated better methodological quality than non-Cochrane reviews. Trials were typically small and the quality variable.There is moderate quality evidence that intravenous regional blockade with guanethidine is not effective in CRPS and that the procedure appears to be associated with the risk of significant adverse events.There is low quality evidence that bisphosphonates, calcitonin or a daily course of intravenous ketamine may be effective for pain when compared with placebo; graded motor imagery may be effective for pain and function when compared with usual care; and that mirror therapy may be effective for pain in post-stroke CRPS compared with a 'covered mirror' control. This evidence should be interpreted with caution. There is low quality evidence that local anaesthetic sympathetic blockade is not effective. Low quality evidence suggests that physiotherapy or occupational therapy are associated with small positive effects that are unlikely to be clinically important at one year follow up when compared with a social work passive attention control.For a wide range of other interventions, there is either no evidence or very low quality evidence available from which no conclusions should be drawn.

AUTHORS' CONCLUSIONS

There is a critical lack of high quality evidence for the effectiveness of most therapies for CRPS. Until further larger trials are undertaken, formulating an evidence-based approach to managing CRPS will remain difficult.

[Please don't hurt me!: a plea against invasive procedures in children and adolescents with complex regional pain syndrome (CRPS)]

BACKGROUND

Complex regional pain syndrome (CRPS; formerly known as Morbus Sudeck/reflex dystrophy) is diagnosed in children and adolescents, but the clinical presentation is often atypical. Unfortunately, potentially harmful, invasive treatments are used in pediatric patients.

PATIENTS AND METHODS

A retrospective chart study of pediatric chronic pain patients with CRPS was performed.

RESULTS

Over the course of 6 years, 37 (35 girls) children and adolescents took part in a multidisciplinary chronic pain inpatient program. At admission, patients took on average 4.4 (range 1-10) different medications and 29 different pharmaceuticals were used overall. Prior to admission, invasive pain treatments were performed without success in 16 of the children (43%). At least 13 children received two or more invasive treatments. Although sympathetic blocks were most prevalent, operations and regional anesthesia were also used.

CONCLUSION

Despite a lack of evidence for invasive procedures, these continue to be used in children and adolescents with CRPS, who later respond positively to conventional treatment. The English full-text version of this article is available at SpringerLink (under "Supplemental").

Cutaneous noradrenaline measured by microdialysis in complex regional pain syndrome during whole-body cooling and heating

Complex regional pain syndrome (CRPS) is characterised by autonomic, sensory, and motor disturbances. The underlying mechanisms of the autonomic changes in CPRS are unknown. However, it has been postulated that sympathetic inhibition in the acute phase with locally reduced levels of noradrenaline is followed by an up-regulation of alpha-adrenoceptors in chronic CRPS leading to denervation supersensitivity to catecholamines. This exploratory study examined the effect of cutaneous sympathetic activation and inhibition on cutaneous noradrenaline release, vascular reactivity, and pain in CRPS patients and in healthy volunteers. Seven patients and nine controls completed whole-body cooling (sympathetic activation) and heating (sympathetic inhibition) induced by a whole-body thermal suit with simultaneous measurement of the skin temperature, skin blood flow, and release of dermal noradrenaline. CRPS pain and the perceived skin temperature were measured every 5 min during thermal exposure, while noradrenaline was determined from cutaneous microdialysate collected every 20 min throughout the study period. Cooling induced peripheral sympathetic activation in patients and controls with significant increases in dermal noradrenaline, vasoconstriction, and reduction in skin temperature. The main findings were that the noradrenaline response did not differ between patients and controls or between the CRPS hand and the contralateral unaffected hand, suggesting that the evoked noradrenaline release from the cutaneous sympathetic postganglionic fibres is preserved in chronic CRPS patients.

Complex regional pain syndrome: practical diagnostic and treatment guidelines, 4th edition

OBJECTIVE

This is the fourth edition of diagnostic and treatment guidelines for complex regional pain syndrome (CRPS; aka reflex sympathetic dystrophy).

METHODS

Expert practitioners in each discipline traditionally utilized in the treatment of CRPS systematically reviewed the available and relevant literature; due to the paucity of levels 1 and 2 studies, less rigorous, preliminary research reports were included. The literature review was supplemented with knowledge gained from extensive empirical clinical experience, particularly in areas where high-quality evidence to guide therapy is lacking.

RESULTS

The research quality, clinical relevance, and "state of the art" of diagnostic criteria or treatment modalities are discussed, sometimes in considerable detail with an eye to the expert practitioner in each therapeutic area. Levels of evidence are mentioned when available, so that the practitioner can better assess and analyze the modality under discussion, and if desired, to personally consider the citations. Tables provide details on characteristics of studies in different subject domains described in the literature.

CONCLUSIONS

In the humanitarian spirit of making the most of all current thinking in the area, balanced by a careful case-by-case analysis of the risk/cost vs benefit analysis, the authors offer these "practical" guidelines.

Stellate ganglion block: a therapeutic alternative for patients with medically refractory inappropriate sinus tachycardia?

Inappropriate sinus tachycardia (IST) is a clinical syndrome characterized by presence of non-paroxysmal tachyarrhythmia manifesting with increased resting heart rate and exaggerated or persistent response to exercise or position. When IST is intolerable and medically refractory, invasive therapies such as sinus node modification or atrioventricular node ablation with placement of permanent pacemaker are tried to control symptoms. We present a 34 year old patient with symptomatic IST unresponsive to medical therapy who underwent anesthetic block of the right and left stellate ganglia. At four month follow up the patient demonstrated sustained improvement in heart rate and reported freedom from previous symptoms.

Treatment of complex regional pain syndrome in adults: a systematic review of randomized controlled trials published from June 2000 to February 2012

Complex regional pain syndrome (CRPS) is a disabling pain condition with sensory, motor and autonomic manifestations. Uncertainty remains about how CRPS can be effectively managed. We conducted a systematic review of randomized controlled trials (RCTs) for treatment and prophylactic interventions for CRPS published during the period 2000-2012, building on previous work by another group reviewing the period 1966-2000. Bibliographic database searches identified 173 papers which were filtered by three reviewers. This process generated 29 trials suitable for further analysis, each of which was reviewed and scored by two independent reviewers for methodological quality using a 15-item checklist. A number of novel and potentially effective treatments were investigated. Analysing the results from both review periods in combination, there was a steep rise in the number of published RCTs per review decade. There is evidence for the efficacy of 10 treatments (3× strong--bisphosphonates, repetitive transcranial magnetic stimulation and graded motor imagery, 1× moderate and 6× limited evidence), and against the efficacy of 15 treatments (1× strong, 1× moderate and ×13 limited). The heterogeneity of trialled interventions and the pilot nature of many trials militate against drawing clear conclusions about the clinical usefulness of most interventions. This and the observed phenomenon of excellent responses in CRPS subgroups would support the case for a network- and multi-centre approach in the conduct of future clinical trials. Most published trials in CRPS are small with a short follow-up period, although several novel interventions investigated from 2000 to 2012 appear promising.

Complex [corrected] regional pain syndrome: what specialized rehabilitation services do patients require?

Complex [corrected] regional pain syndrome (CRPS) is a complex disorder, the optimal treatment of which requires an interdisciplinary approach encompassing medical, interventional, psychological, and rehabilitation services that emphasize the role of physical and occupational therapies. The central focus of treatment is the restoration of function, utilizing a systematic, coordinated, and progressive set of therapeutic strategies. The poorly delineated pathophysiology and variable course of CRPS suggest that individualized strategies are required for optimal management, but also mean that carefully controlled trials of physiotherapy are difficult to conduct. This article presents a brief review of the nature and pathophysiology of CRPS, the medical and psychological approaches that have been found to be effective, and a review of the current trends in rehabilitation.

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.

Buprenorphine injection to the stellate ganglion in the treatment of upper body chronic pain syndromes

BACKGROUND

The injection of low dose buprenorphine to the sympathetic ganglia, termed "GLOA", Ganglionide Local Opioid Analgesia, is used to treat chronic pain in several European centres. It is not known whether the clinically observed GLOA effect in chronic pain syndromes is due to a specific effect of buprenorphine at the ganglia. We assessed whether GLOA, plus intramuscular saline, was more efficacious than the reverse, saline injection to the stellate plus intramuscular buprenorphine, termed SSB.

METHODS

We devised a randomized, double-blinded, controlled crossover trial to treat patients with chronic upper body pain syndromes. Patients first received either GLOA or SSB. Pain was assessed using pain diaries both before injection and over the first 8h and 6days afterwards, and was expressed as relative pain intensity post versus pre-injection pain.

RESULTS

The median relative pain intensity after injections did not differ between GLOA and SSB. Four patients reported a low, <50%, relative pain level over the first 8h after SSB only. Four patients did not complete the trial and were excluded. One patient with cardiomyopathy became acutely diaphoretic and fatigued after GLOA, his vital signs however remained stable.

CONCLUSIONS

We failed to show a superiority of GLOA over SSB. Our results suggest it unlikely that the clinically observed effect after a single GLOA injection is due to a specific action of buprenorphine at the stellate ganglion. The efficacy of GLOA is hereby questioned. The use of GLOA in patients with cardiomyopathy should be cautioned.

TRIAL REGISTRATION

ISRCTN59287260; http://www.controlled-trials.com/

Complex regional pain syndrome: state of the art update

OPINION STATEMENT

Although the pathophysiology of complex regional pain syndrome (CRPS) is not fully understood, it appears to reflect multiple interacting mechanisms. In addition to altered autonomic function, a role for inflammatory mechanisms and altered somatosensory and motor function in the brain is increasingly suggested. Several possible risk factors for development of CRPS, including genetic factors, have been identified. Few treatments have been proven effective for CRPS in well-designed clinical trials. However, recent work suggests that bisphosphonates may be useful in CRPS management and that the N-methyl-D: -aspartate receptor antagonist ketamine significantly reduces CRPS pain when administered topically or intravenously at subanesthetic dosages. Extended use of ketamine at anesthetic dosages ("ketamine coma") remains a controversial and unproven treatment for CRPS. Spinal cord stimulation may be effective for reducing pain in approximately two thirds of CRPS patients not responding to other treatments, but its efficacy appears to diminish over time.

Complex regional pain syndrome in adults

Complex regional pain syndrome (CRPS) is a highly painful, limb-confined condition, which arises usually after trauma. It is associated with a particularly poor quality of life, and large health-care and societal costs. The causes of CRPS remain unknown. The condition's distinct combination of abnormalities includes limb-confined inflammation and tissue hypoxia, sympathetic dysregulation, small fibre damage, serum autoantibodies, central sensitization and cortical reorganization. These features place CRPS at a crossroads of interests of several disciplines including rheumatology, pain medicine and neurology. Significant scientific and clinical advances over the past 10 years hold promise both for an improved understanding of the causes of CRPS, and for more effective treatments. This review summarizes current concepts of our understanding of CRPS in adults. Based on the results from systematic reviews, treatment approaches are discussed within the context of these concepts. The treatment of CRPS is multidisciplinary and aims to educate about the condition, sustain or restore limb function, reduce pain and provide psychological intervention. Results from recent randomized controlled trials suggest that it is possible that some patients whose condition was considered refractory in the past can now be effectively treated, but confirmatory trials are required. The review concludes with a discussion of the need for additional research.

Complex regional pain syndrome

Complex regional pain syndrome (CRPS) is a challenging pain condition for doctors and patients, with a natural history characterized by chronicity and relapses that can result in significant disability. CRPS is difficult to diagnose and treat, and requires close follow-up to ensure that progress is being made. Early diagnosis and treatment are required to prevent a long-standing or permanent disability. Clinical features such as spontaneous pain, edema, hyperalgesia, temperature or sudomotor changes, motor function abnormality, and autonomic changes are the hallmark of this disease. The treatment of CRPS remains controversial, and includes medications, physical therapy, regional anesthesia, and neuromodulation.

Stellate ganglion blockade for analgesia following upper limb surgery

We report the successful use of a stellate ganglion block as part of a multi-modal postoperative analgesic regimen. Four patients scheduled for orthopaedic surgery following upper limb trauma underwent blockade of the stellate ganglion pre-operatively under ultrasound guidance. Patients reported excellent postoperative analgesia, with postoperative VAS pain scores between 0 and 2, and consumption of morphine in the first 24 h ranging from 0 to 14 mg. While these are preliminary findings, and must be confirmed in a clinical trial, they highlight the potential for stellate ganglion blockade to provide analgesia following major upper limb surgery.

The contribution of sympathetic mechanisms to postamputation phantom and residual limb pain: a pilot study

Postamputation pain (PAP) affects over 60% of major limb amputees. One of the main challenges in treating PAP is the difficulty involved in identifying pain mechanism(s), which pertains to both residual limb pain (RLP) and phantom limb pain (PLP). In this study, sympathetic blocks were performed on 17 major limb amputees refractory to treatment, including 2 placebo-controlled blocks done for bilateral amputations. One hour postinjection, mean RLP scores at rest declined from 5.2 (SD 2.8) to 2.8 (SD 2.6) (P = .0002), and PLP decreased from 5.3 (SD 3.1) to 2.3 (SD 2.1) (P = .0009). By 1 week, mean pain scores for RLP and PLP were 4.3 (SD 2.9) and 4.2 (SD 3.0), respectively. Overall, 8 of 16 (50%) patients experienced ≥50% reduction in RLP 1-hour postinjection, with the beneficial effects being maintained at 1 and 8 weeks in 4 and 1 patient(s), respectively. For PLP, 8 of 15 (53%) patients obtained ≥50% decrease in pain 1-hour postblock, with these numbers decreasing to 2 patients at both 1 and 8 weeks. In the 2 bilateral amputees who received controlled injections, mean PLP and RLP at rest scores went from 4.0 and 3.3 to 4.0 and 2.5 1-hour postblock, respectively, on the placebo side. On the treatment side, mean PLP and RLP scores decreased from 7.5 and 6.5, respectively, to 0.

PERSPECTIVE

The results of this study suggest that sympathetic mechanisms play a role in PLP and to a lesser extent, RLP, but that blocks confer long-term benefits in only a small percentage of patients.

Is it all central sensitization? Role of peripheral tissue nociception in chronic musculoskeletal pain

Fibromyalgia syndrome (FM) is a highly prevalent musculoskeletal disorder that is often accompanied by somatic hyperalgesia (enhanced pain from noxious stimuli). Neural mechanisms of somatic hyperalgesia have been analyzed via quantitative sensory testing of FM patients. Results of these studies suggest that FM pain is associated with widespread primary and secondary cutaneous hyperalgesia, which are dynamically maintained by tonic impulse input from deep tissues and likely by brain-to-spinal cord facilitation. Enhanced somatic pains are accompanied by mechanical hyperalgesia and allodynia in FM patients as compared with healthy controls. FM pain is likely to be at least partially maintained by peripheral impulse input from deep tissues. This conclusion is supported by results of several studies showing that injection of local anesthetics into painful muscles normalizes somatic hyperalgesia in FM patients.

Diagnostic blocks for chronic pain

Many conditions associated with chronic pain have no detectable morphological correlate. Consequently, the source of pain cannot be established by clinical examination or medical imaging. However, for some such conditions, the source of pain can be established using diagnostic blocks. The aim of this paper is to review the available evidence concerning the validity and utility of diagnostic blocks, and to identify areas where research is needed. Diagnostic blocks for cervical and lumbar zygapophysial joint pain have been extensively studied. Single blocks are associated with about 30% false-positive responses. Patients can report relief of pain for reasons other than the effect of a local anaesthetic injected during a diagnostic block, e.g. as the result of placebo effect. Therefore, in order to be valid, diagnostic blocks must be controlled in each patient. Many practitioners find limitations in the clinical applicability of placebo-controlled blocks. Comparative blocks (comparison lidocaine-bupivacaine for each block within each patient) have been investigated as alternatives to placebo-controlled blocks. A positive response requires short-lasting relief when lidocaine is used, and long-lasting relief when bupivacaine is used. The validity of comparative blocks is high when the disease under investigation is common. This is the case for zygapophysial joint pain after whiplash injury. However, the validity of comparative blocks strongly decreases with decreasing prevalence of the condition. This is the case for lumbar zygapophysial joint pain in young subjects: in these patients, the expected false-positive rate with comparative blocks is unacceptably high. Diagnostic blocks for cervical and lumbar zygapophysial joint have therapeutic utility. When positive, radiofrequency denervation is expected to produce substantial pain relief in 60-80% of patients. For all other types of blocks, very little research has been conducted. The few studies that have been published did not use controlled blocks. This may have produced a high rate of false-positive responses. Some data on spinal nerve root blocks suggest that these procedures may be valid for the diagnosis of radicular pain and are perhaps predictive for the success of surgery. The validity of diagnostic sympathetic blocks and their prognostic value in relation to outcomes of sympathectomy are unclear. There is lack of data on the validity of diagnostic intra-articular blocks. Discogenic pain is typically diagnosed by provocative discography, but this procedure remains controversial. Intradiscal and sinuvertebral nerve blocks with local anaesthetics are possible alternatives to provocation discography. At present, the sparse data available on these procedures do not allow an estimation of their validity. In conclusion, nerve blocks have an important potential role in the management of chronic pain. These procedures are not suitable to identify the pathology that is the cause of the pain (e.g. inflammatory, neuropathic, etc.). However, they can reveal the anatomical source of pain, thereby allowing the development of targeted treatments. Unfortunately, there is currently very little research on the validity and prognostic value of blocks. The potential usefulness of this practice remains therefore largely unexplored.

Evidence-based interventional pain medicine according to clinical diagnoses. 16. Complex regional pain syndrome

Complex regional pain syndrome (CRPS), formerly known as reflex sympathetic dystrophy is a pain syndrome with an unclear pathophysiology and unpredictable clinical course. The disease is often therapy resistant, the natural course not always favorable. The diagnosis of CRPS is based on signs and symptoms derived from medical history and physical examination. Pharmacological pain management and physical rehabilitation of limb function are the main pillars of therapy and should be started as early as possible. If, however, there is no improvement of limb function and persistent severe pain, interventional pain management techniques may be considered. Intravenous regional blocks with guanethidine did not prove superior to placebo but frequent side effects occurred.Therefore this technique receives a negative recommendation (2 A-). Sympathetic block is the interventional treatment of first choice and has a 2 B+ rating. Ganglion stellatum (stellate ganglion) block with repeated local anesthetic injections or by radiofrequency denervation after positive diagnostic block is documented in prospective and retrospective trials in patients suffering from upper limb CRPS. Lumbar sympathetic blocks can be performed with repeated local anesthetic injections. For a more prolonged lumbar sympathetic block radiofrequency treatment is preferred over phenol neurolysis because effects are comparable whereas the risk for side effects is lower (2 B+). For patients suffering from CRPS refractory to conventional treatment and sympathetic blocks, plexus brachialis block or continuous epidural infusion analgesia coupled with exercise therapy may be tried (2 C+). Spinal cord stimulation is recommended if other treatments fail to improve pain and dysfunction (2 B+). Alternatively peripheral nerve stimulation can be considered, preferentially in study conditions (2 C+).

Neuropathic pain: diagnosis, pathophysiological mechanisms, and treatment

Neuropathic pain develops as a result of lesions or disease affecting the somatosensory nervous system either in the periphery or centrally. Examples of neuropathic pain include painful polyneuropathy, postherpetic neuralgia, trigeminal neuralgia, and post-stroke pain. Clinically, neuropathic pain is characterised by spontaneous ongoing or shooting pain and evoked amplified pain responses after noxious or non-noxious stimuli. Methods such as questionnaires for screening and assessment focus on the presence and quality of neuropathic pain. Basic research is enabling the identification of different pathophysiological mechanisms, and clinical assessment of symptoms and signs can help to determine which mechanisms are involved in specific neuropathic pain disorders. Management of neuropathic pain requires an interdisciplinary approach, centred around pharmacological treatment. A better understanding of neuropathic pain and, in particular, of the translation of pathophysiological mechanisms into sensory signs will lead to a more effective and specific mechanism-based treatment approach.

Complex regional pain syndrome: an actual survey

Complex regional pain syndrome - in the past called sympathetic reflex dystrophy - is, in its pathophysiology, still not fully understood. However, research in the last few years has led to a better understanding of the illness and the beginning of a pathophysiologically- orientated therapy. The core hypothesis is based on neuropeptide release, neurogenic inflammation and its sympathetic dependence. Therapy should be based on current pathophysiological concepts regarding CRPS and neuropathic pain and could thereby lead to a good outcome of the illness.

Treatment of complex regional pain syndrome: a review of the evidence

PURPOSE

This narrative review summarizes the evidence derived from randomized controlled trials pertaining to the treatment of complex regional pain syndrome (CRPS).

SOURCE

Using the MEDLINE (January 1950 to April 2009) and EMBASE (January 1980 to April 2009) databases, the following medical subject headings (MeSH) were searched: "Complex Regional Pain Syndrome", "Reflex Sympathetic Dystrophy", and "causalgia" as well as the key words "algodystrophy", "Sudeck's atrophy", "shoulder hand syndrome", "neurodystrophy", "neuroalgodystrophy", "reflex neuromuscular dystrophy", and "posttraumatic dystrophy". Results were limited to randomized controlled trials (RCTs) conducted on human subjects, written in English, published in peer-reviewed journals, and pertinent to treatment.

PRINCIPAL FINDINGS

The search criteria yielded 41 RCTs with a mean of 31.7 subjects per study. Blinded assessment and sample size justification were provided in 70.7% and 19.5% of RCTs, respectively. Only biphosphonates appear to offer clear benefits for patients with CRPS. Improvement has been reported with dimethyl sulfoxide, steroids, epidural clonidine, intrathecal baclofen, spinal cord stimulation, and motor imagery programs, but further trials are required. The available evidence does not support the use of calcitonin, vasodilators, or sympatholytic and neuromodulative intravenous regional blockade. Clear benefits have not been reported with stellate/lumbar sympathetic blocks, mannitol, gabapentin, and physical/occupational therapy.

CONCLUSIONS

Published RCTs can only provide limited evidence to formulate recommendations for treatment of CRPS. In this review, no study was excluded based on factors such as sample size justification, statistical power, blinding, definition of intervention allocation, or clinical outcomes. Thus, evidence derived from "weaker" trials may be overemphasized. Further well-designed RCTs are warranted.

Evidence based guidelines for complex regional pain syndrome type 1

Background

Treatment of complex regional pain syndrome type I (CRPS-I) is subject to discussion. The purpose of this study was to develop multidisciplinary guidelines for treatment of CRPS-I.

Method

A multidisciplinary task force graded literature evaluating treatment effects for CRPS-I according to their strength of evidence, published between 1980 to June 2005. Treatment recommendations based on the literature findings were formulated and formally approved by all Dutch professional associations involved in CRPS-I treatment.

Results

For pain treatment, the WHO analgesic ladder is advised with the exception of strong opioids. For neuropathic pain, anticonvulsants and tricyclic antidepressants may be considered. For inflammatory symptoms, free-radical scavengers (dimethylsulphoxide or acetylcysteine) are advised. To promote peripheral blood flow, vasodilatory medication may be considered. Percutaneous sympathetic blockades may be used to increase blood flow in case vasodilatory medication has insufficient effect. To decrease functional limitations, standardised physiotherapy and occupational therapy are advised. To prevent the occurrence of CRPS-I after wrist fractures, vitamin C is recommended. Adequate perioperative analgesia, limitation of operating time, limited use of tourniquet, and use of regional anaesthetic techniques are recommended for secondary prevention of CRPS-I.

Conclusions

Based on the literature identified and the extent of evidence found for therapeutic interventions for CRPS-I, we conclude that further research is needed into each of the therapeutic modalities discussed in the guidelines.

Complex regional pain syndrome type I: efficacy of stellate ganglion blockade

Background

This study was performed to evaluate the treatment of complex regional pain syndrome (CRPS) type I with stellate ganglion blockade.

Materials and methods

We performed three blockades at weekly intervals in 22 patients with CRPS type I in one hand. The patients were divided into two groups depending on the time between symptom onset and treatment initiation. Group 1and 2 patients had short and long symptom-onset-to-treatment intervals, respectively. Pain intensity, using a visual analog score (VAS), and range of motion (ROM) for the wrist joint were assessed before and 2 weeks after treatment and were compared using nonparametric statistical analysis.

Results

Treatment produced a statistically significant difference in wrist ROM for all patients (P < 0.001). VAS values showed an overall decrease from 8 ± 1 to 1 ± 1 following treatment, and there was a significant difference in VAS value between groups 1 and 2 (P < 0.05).

Conclusions

We concluded that stellate ganglion blockade successfully decreased VAS and increased ROM of wrist joints in patients with CRPS type I. Further, the duration between symptom onset and therapy initiation was a major factor affecting blockade success.

The fascination of complex regional pain syndrome

Complex regional pain syndrome (CRPS) is a pain disorder involving the somatosensory, the somatomotor and the sympathetic nervous systems. Based on experiments conducted by Bove (2009), it is suggested that changes in impulse activity in small-diameter afferents and postganglionic axons generated by neuritis can contribute to signs of early CRPS. The potential mechanisms involved are discussed. These mechanisms include the possibility that CRPS, a disorder of the central nervous system, may be caused by a nerve inflammation.

The natural history of complex regional pain syndrome

OBJECTIVE

Complex regional pain syndrome (CRPS) is a severe chronic pain condition characterized by sensory, autonomic, motor, and dystrophic signs and symptoms. This study was undertaken to expand our current knowledge of the evolution of CRPS signs and symptoms with duration of disease.

METHOD

This was a retrospective, cross-sectional analysis using data extracted from a patient questionnaire to evaluate the clinical characteristics of CRPS at different time points of disease progression. Data from the questionnaire included pain characteristics and associated symptoms. It also included autonomic, motor, and dystrophic symptoms and also initiating events, ameliorating and aggravating factors, quality of life, work status, comorbid conditions, pattern of pain spread, family history, and demographics. Comparisons were made of different parameters as they varied with disease duration.

RESULTS

A total of 656 patients with CRPS of at least 1-year duration were evaluated. The average age of all participants was 37.5 years, with disease duration varying from 1 to 46 years. The majority of participants were white (96%). A total of 80.3% were females. None of the patients in this study demonstrated spontaneous remission of their symptoms. The pain in these patients was refractory showing only modest improvement with most current therapies.

DISCUSSION

This study shows that although CRPS is a progressive disease, after 1 year, the majority of the signs and symptoms were well developed and although many variables worsen over the course of the illness, the majority demonstrated only moderate increases with disease duration.

Enhanced central pain processing of fibromyalgia patients is maintained by muscle afferent input: a randomized, double-blind, placebo-controlled study

Fibromyalgia (FM) syndrome is characterized by pain and widespread hyperalgesia to mechanical, thermal, and electrical stimuli. Despite convincing evidence for central sensitization of nociceptive pain pathways, the role of peripheral tissue impulse input in the initiation and maintenance of FM is unclear. Therefore this randomized, double-blind, placebo-controlled trial of 22 female normal controls (NCs) and 28 female FM subjects tested the effects of trapezius muscle (TrapM) tender point injections with 1% lidocaine on local pain thresholds as well as on remote heat hyperalgesia at the forearm. Prior to muscle injections shoulder pain was standardized by tonic mechanical muscle stimulation, resulting in local pain ratings of 4.0+/-0.5 VAS units. Tonic muscle stimulation was interrupted for the TrapM injections but was continued afterwards at the same level. NC as well as FM subjects experienced significant increases of TrapM pressure pain thresholds from lidocaine injections but not from placebo injections (p<0.001). Additionally, heat hyperalgesia of FM participants was significantly reduced at areas remote from the injection site (forearm) by lidocaine but not by placebo (p=0.02). Neither lidocaine nor saline injections significantly affected clinical FM pain ratings, a result most likely due to the very low dose of lidocaine (50mg) used in this trial.

CONCLUSION

Lidocaine injections increased local pain thresholds and decreased remote secondary heat hyperalgesia in FM patients, emphasizing the important role of peripheral impulse input in maintaining central sensitization in this chronic pain syndrome; similar to other persistent pain conditions such as irritable bowel syndrome and complex regional pain syndrome.

Widespread hyperalgesia in irritable bowel syndrome is dynamically maintained by tonic visceral impulse input and placebo/nocebo factors: evidence from human psychophysics, animal models, and neuroimaging

Irritable bowel syndrome (IBS) is a highly prevalent gastrointestinal disorder that is often accompanied by both visceral and somatic hyperalgesia (enhanced pain from colorectal and somatic stimuli). Neural mechanisms of both types of hyperalgesia have been analyzed by neuroimaging studies of IBS patients and animal analog studies of "IBS-like" rats with delayed rectal and somatic hypersensitivity. Results from these studies suggest that pains associated with both visceral and widespread secondary cutaneous hyperalgesia are dynamically maintained by tonic impulse input from the non-inflamed colon and/or rectum and by brain-to-spinal cord facilitation. Enhanced visceral and somatic pains are accompanied by enhanced pain-related brain activity in IBS patients as compared to normal control subjects; placebos can normalize both their hyperalgesia and enhanced brain activity. That pain in IBS which is likely to be at least partly maintained by peripheral impulse input from the colon/rectum is supported by results showing that local rectal-colonic anesthesia normalizes visceral and somatic hyperalgesia in IBS patients and visceral and somatic hypersensitivity in "IBS-like" rats. Yet these forms of hyperalgesia are also highly modifiable by placebo and nocebo factors (e.g., expectations of relief or distress, respectively). Our working hypothesis is that synergistic interactions occur between placebo/nocebo factors and enhanced afferent processing so as to enhance, maintain, or reduce hyperalgesia in IBS. This explanatory model may be relevant to other persistent pain conditions.

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.

Neuropathic pain: a clinical perspective

Neuropathic pain syndromes, i.e., pain after a lesion or disease of the peripheral or central nervous system, are clinically characterized by spontaneous pain (ongoing, paroxysms) and evoked types of pain (hyperalgesia, allodynia). A variety of distinct pathophysiological mechanisms in the peripheral and central nervous system operate in concert: In some patients the nerve lesion triggers molecular changes in nociceptive neurons that become abnormally sensitive and develop pathological spontaneous activity (upregulation of sodium channels and receptors, e.g., vanilloid TRPV1 receptors, menthol-sensitive TRPM8 receptors, or alpha-receptors). These phenomena may lead to spontaneous pain, shooting pain sensations, as well as heat hyperalgesia, cold hyperalgesia, and sympathetically maintained pain. Spontaneous activity in damaged large nonnociceptive A-fibers may lead to paresthesias. All these changes may also occur in uninjured neurons driven by substances released by adjacent dying cells and should receive more attention in the future. The hyperactivity in nociceptors in turn induces secondary changes (hyperexcitability) in processing neurons in the spinal cord and brain. This central sensitization causes input from mechanoreceptive A-fibers to be perceived as pain (mechanical allodynia). Neuroplastic changes in the central descending pain modulatory systems (inhibitory or facilitatory) may lead to further hyperexcitability. Neuropathic pain represents a major neurological problem and treatment of patients with such pain has been largely neglected by neurologists in the past. The medical management of neuropathic pain consists of five main classes of oral medication (antidepressants with reuptake blocking effect, anticonvulsants with sodium-blocking action, anticonvulsants with calcium-modulating actions, tramadol, and opioids) and several categories of topical medications for patients with cutaneous allodynia and hyperalgesia (capsaicin and local anesthetics). In many cases an early combination of compounds effecting different mechanisms is useful. At present existing trials only provide general pain relief values for specific causes, which in part may explain the failure to obtain complete pain relief in neuropathic pain conditions. In general, the treatment of neuropathic pain is still unsatisfactorily. Therefore, a new hypothetical concept was proposed in which pain is analyzed on the basis of underlying mechanisms. The increased knowledge of pain-generating mechanisms and their translation into symptoms and signs may in the future allow a dissection of the mechanisms that operate in each patient. If a systematic clinical examination of the neuropathic pain patient and a precise phenotypic characterization is combined with a selection of drugs acting against those particular mechanisms, it should ultimately be possible to design optimal treatments for the individual patient.

Reversal of visceral and somatic hypersensitivity in a subset of hypersensitive rats by intracolonic lidocaine

Chronic abdominal pain is a common gastrointestinal symptom experienced by patients. We have previously shown that IBS patients with visceral hypersensitivity also have evidence of thermal hypersensitivity of the hand and foot that is reversed by rectal lidocaine jelly. We have also recently developed an animal model of chronic visceral and somatic hypersensitivity in rats treated with intracolonic trinitrobenzene sulfonic acid (TNBS). The objective of the current study was to determine the effects of intracolonic lidocaine on visceral/somatic hypersensitivity in TNBS-treated rats. A total of 20 hypersensitive rats received either 20mg intracolonic lidocaine (n=10) or saline jelly (n=10). In comparison to saline jelly, intracolonic lidocaine jelly reduced responses to nociceptive visceral/somatic stimuli in hypersensitive rats. The effects were present within 5-30 min after administration of lidocaine and lasted for 6h. Lidocaine had no effects on recovered rats or control rats that had originally been treated with intracolonic saline instead of TNBS. Local anesthetic blockade of peripheral impulse input from the colon reduces both visceral and somatic hypersensitivity in TNBS-treated rats, similar to results in IBS patients. The results provide further evidence that visceral and secondary somatic hypersensitivity in a subset of TNBS-treated rats reflect central sensitization mechanisms maintained by tonic impulse input from the colon. This study evaluates the reversal of visceral/somatic hypersensitivity in a subset of TNBS-treated rats with intracolonic lidocaine. This animal model may be used in the future to study the mechanisms of local anesthetic agents applied to the gut to reduce visceral pain.