Subtypes of complex regional pain syndrome-a systematic review of the literature.

To systematically identify and summarize possible subtypes of complex regional pain syndrome (CRPS), we searched MEDLINE, Embase, Cochrane, Scopus, and Web of Science for original studies reporting or investigating at least one subtype within a group of patients with CRPS. The search retrieved 4239 potentially relevant references. Twenty-five studies met our inclusion criteria and were included in the analysis. Complex regional pain syndrome phenotypes were investigated based on the following variables: clinical presentation/sensory disturbances, dystonia, skin temperature, disease duration, onset type, CRPS outcome, and neuropsychological test performance. Support was found for the following CRPS subtypes: CRPS type I, CRPS type II, acute CRPS, chronic CRPS, centralized CRPS, cold CRPS, warm CRPS, inflammatory CRPS, dystonic CRPS, nondystonic CRPS, familial CRPS, and nonfamilial CRPS. It is unclear whether these are distinct or overlapping subtypes. The results of this comprehensive review can facilitate the formulation of well-defined CRPS subtypes based on presumed underlying mechanisms. Our findings provide a foundation for establishing and defining clinically meaningful CRPS subtypes, with the ultimate goal of developing targeted and enhanced treatments for CRPS.

Lumbar Sympathetic Plexus Block as a Treatment for Postamputation Pain: Methodology for a Randomized Controlled Trial.

Objective: We present a technical protocol for rigorous assessment of patient-reported outcomes and psychophysical testing relevant to lumbar sympathetic blocks for the treatment of postamputation pain (PAP). This description is intended to inform future prospective investigation. Design: Series of four participants from a blinded randomized sham-controlled trial. Setting: Tertiary, urban, academic pain medicine center. Subjects: Four participants with a single lower limb amputation and associated chronic PAP. Methods: Participants were randomized to receive a lumbar sympathetic block with 0.25% bupivacaine or sham needle placement. Patient-rated outcome measures included the numerical rating scale (NRS) for pain, the McGill Pain Questionnaire-Short Form, Center for Epidemiological Studies Depression Scale, Pain and Anxiety Symptoms Scale-short version, and Pain Disability Index (PDI). Psychophysical and biometric testing was also performed, which included vibration sensation testing, pinprick sensation testing, brush sensation testing, Von Frey repeated weighted pinprick sensation, and thermal quantitative sensory testing. Results: In the four described cases, treatment of PAP with a single lumbar sympathetic block but not sham intervention resulted in reduction of both residual limb pain and phantom limb pain as well as perceived disability on the PDI at three-month follow-up. Conclusions: An appropriately powered randomized controlled study using this methodology may not only aid in determining the possible clinical efficacy of lumbar sympathetic block in PAP, but could also improve our understanding of underlying pathophysiologic mechanisms of PAP.

Managing the placebo effect: enhancing the signal-to-noise ratio.

Confirming the absence of the placebo response has been the bane of researchers throughout the ages. Thus, the gold standard of research methodology is the evidence for a treatment modality provided by a prospective randomized controlled trial. The "control" arm of a trial is the arm in which the placebo has been administered. Increasing evidence from basic science and clinical research is pointing to the fact that the placebo response may have some biological basis that can translate into enduring therapeutic benefit. Have our placebo-controlled trials simply compared one treatment effect to the treatment effect of the "placebo"? Thus, the "δ" is relative treatment effect; perhaps this may provide some insight as to why some treatment response is low compared to a relatively strong placebo response. How can we use this knowledge to create more robust clinical designs that help establish true treatment effect? This article aims to provide an overview of the contemporary insight into the placebo response.

Development of a severity score for CRPS.

The clinical diagnosis of Complex Regional Pain Syndrome (CRPS) is a dichotomous (yes/no) categorization necessary for clinical decision-making. However, such dichotomous diagnostic categories do not convey an individual's subtle and temporal gradations in severity of the condition, and have poor statistical power when used as an outcome measure in research. This study evaluated the validity and potential utility of a continuous type score to index severity of CRPS. Psychometric and medical evaluations were conducted in 114 CRPS patients and 41 non-CRPS neuropathic pain patients. Based on the presence/absence of 17 clinically-assessed signs and symptoms of CRPS, an overall CRPS Severity Score (CSS) was derived. The CSS discriminated well between CRPS and non-CRPS patients (p<.001), and displayed strong associations with dichotomous CRPS diagnoses using both IASP diagnostic criteria (Eta=0.69) and proposed revised criteria (Eta=0.77-0.88). Higher CSS was associated with significantly higher clinical pain intensity, distress, and functional impairments, as well as greater bilateral temperature asymmetry and thermal perception abnormalities (p's<.05). In an archival prospective dataset, increases in anxiety and depression from pre-surgical baseline to 4 weeks post-knee arthroplasty were found to predict significantly higher CSS at 6- and 12-month follow-up (p's<.05). Results indicate the CSS corresponds with and complements currently accepted dichotomous diagnostic criteria for CRPS, and support its validity as an index of CRPS severity. Its utility as an outcome measure in research studies is also suggested, with potential statistical advantages over dichotomous diagnostic criteria.

Validation of proposed diagnostic criteria (the "Budapest Criteria") for Complex Regional Pain Syndrome.

Current IASP diagnostic criteria for CRPS have low specificity, potentially leading to overdiagnosis. This validation study compared current IASP diagnostic criteria for CRPS to proposed new diagnostic criteria (the "Budapest Criteria") regarding diagnostic accuracy. Structured evaluations of CRPS-related signs and symptoms were conducted in 113 CRPS-I and 47 non-CRPS neuropathic pain patients. Discriminating between diagnostic groups based on presence of signs or symptoms meeting IASP criteria showed high diagnostic sensitivity (1.00), but poor specificity (0.41), replicating prior work. In comparison, the Budapest clinical criteria retained the exceptional sensitivity of the IASP criteria (0.99), but greatly improved upon the specificity (0.68). As designed, the Budapest research criteria resulted in the highest specificity (0.79), again replicating prior work. Analyses indicated that inclusion of four distinct CRPS components in the Budapest Criteria contributed to enhanced specificity. Overall, results corroborate the validity of the Budapest Criteria and suggest they improve upon existing IASP diagnostic criteria for CRPS.

Stages of change in readiness to adopt a self-management approach to chronic pain: the moderating role of early-treatment stage progression in predicting outcome.

Relative readiness to assume a self-management approach to chronic pain can be conceptualised as a stage model. Although both initial stage (precontemplation, action) and changes in attitudes reflecting stage orientation have been shown to predict treatment outcome, the joint contributions of these factors need to be examined. Sixty-five chronic pain patients, participating in a 4-week multidisciplinary pain program, completed the Pain Stages of Change Questionnaire (PSOCQ), subscales of the Multidimensional Pain Inventory, and the Beck Depression Inventory at pre-, mid- and post-treatment. Patients were assigned to stage group (precontemplation or action) based on whether their Precontemplation or Action subscale scores were highest. Results showed that: (a) stage group interacted with pre- to mid-treatment Precontemplation subscale changes to predict mid- to late-treatment pain severity and interference changes such that precontemplation attitude decreases were related to reduced pain and interference only among patients who were already action stage at pre-treatment; (b) stage group interacted with pre- to mid-treatment Action subscale changes to predict mid- to late-treatment interference and activity changes such that action attitude increases were related to reduced interference and increased activity only among patients at the action stage at pre-treatment; (c) pre- to mid-treatment decreases in depression did not account for these effects. Results suggest that any advantage enjoyed by patients with predominant action attitudes at pre-treatment may be enhanced by consolidating a pain self-management approach during treatment. In contrast, late-treatment gains of patients initially taking a predominant precontemplation stance were unaffected by their degree of early-treatment attitude changes.

Prospective examination of pain-related and psychological predictors of CRPS-like phenomena following total knee arthroplasty: a preliminary study.

We hypothesized that preoperative emotional distress and pain intensity would predict the occurrence of signs and symptoms of complex regional pain syndrome (CRPS) following total knee arthroplasty (TKA). Depression (Beck Depression Inventory, BDI), anxiety (State Trait Anxiety Inventory, STAI), pain (McGill Pain Questionnaire-Short Form, MPQ), and signs/symptoms meeting IASP criteria for CRPS were assessed preoperatively, and at 1-, 3-, and 6-months postoperatively in 77 patients undergoing TKA. The prevalence of subjects fulfilling CRPS criteria was 21.0% at 1 month, 13.0% at 3 months, and 12.7% at 6 months postoperative. Higher preoperative scores on the STAI predicted positive CRPS status at 1-month follow-up (P<0.05), with a similar non-significant trend for preoperative BDI scores (P<0.10). Diagnostic sensitivity for the STAI was good (0.73), with moderate specificity (0.56). Neither measure predicted CRPS at later follow-up (P>0.10). Greater preoperative pain intensity predicted positive CRPS status at 3-month (MPQ-Sensory and MPQ-Affective; P<0.01) and 6-month (MPQ-Sensory) follow-up (P<0.01), but not at 1-month (P>0.10). Diagnostic sensitivity was high (0.83-1.00), with moderate specificity (0.53-0.60). Post-TKA patients with CRPS were more depressed at 1-month follow-up (P<0.05) and more anxious at 6-month follow-up (P<0.05) than patients with ongoing non-CRPS pain (all other comparisons non-significant, P>0.10). Overall, results indicate that CRPS-like phenomena occur in a significant number of patients early post-TKA; however, it is not associated with significantly greater complaints of postoperative pain. There appears to be a modest utility for preoperative distress and pain in predicting CRPS signs and symptoms following TKA, although false positive rates are relatively high.

Unmet needs in the management of neuropathic pain.

Neuropathic pain is a challenging condition to treat. It is heterogeneous in nature and largely resistant to treatment with commonly prescribed analgesics. Current management strategies fail to achieve adequate or satisfactory pain relief in a high proportion of patients. The four main reasons that treatments for neuropathic pain fail are: inadequate diagnosis and a lack of appreciation of the mechanisms involved; insufficient management of comorbid conditions; incorrect understanding or selection of treatment options; and the use of inappropriate outcomes measures. These unmet needs in the current management of neuropathic pain are reviewed in this article. The review focuses on the need for a methodical and mechanistic approach to diagnosis, and a flexible, interdisciplinary approach to treatment of neuropathic pain conditions, in order to improve pain relief and quality of life in patients with neuropathic pain.

American Academy of Disability Evaluating Physicians (AADEP) position paper: complex regional pain syndrome I (RSD): impairment and disability issues.

OBJECTIVE: To provide an overview and methodology for the evaluation of impairment and functional residual capacity in complex regional pain syndrome I (CRPS I, RSD). This paper is intended to provide assistance to physicians asked to evaluate impairment- and disability-related issues and is not primarily geared to guide treatment of the CRPS I patient. METHOD: Conference and literature review by neurology, anesthesiology, pain medicine, physiatry, and disability evaluating physicians followed by description of issues, options, and recommendations based upon the committee's deliberations and the widely used AMA Guides to the Evaluation of Permanent Impairment, fourth and fifth editions. The authors present functional criteria for assessing the severity of CRPS. These criteria were developed by committee consensus opinion based on multidisciplinary clinical experience considering daily functional issues. They can be used in conjunction with CRPS-ADL Classes of Impairment in order to categorize an individual into a specific class for purposes of permanent impairment rating. Future reliability and validity studies of this rating scale are pending future use, acceptance and, hopefully, additional studies. RESULTS: Evaluators should perform a comprehensive assessment of patients with CRPS I to make an accurate diagnosis and exclude other conditions that could explain the symptoms and signs of the condition. While radiological, laboratory, and other diagnostic studies may be of assistance in making the diagnosis, in the final analysis, this is a clinical diagnosis. Impairment is based on objectively validated limitation in activities of daily living (ADL).