The journal of pain : official journal of the American Pain Society
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Fibromyalgia (FM) is a chronic, widespread musculoskeletal pain disorder that is very prevalent in the general population (approximately 5%). Accumulating evidence suggests that FM is associated with central pain processing abnormalities, ie, central sensitization. Several previous studies of chronic pain patients, including FM, have shown gray matter atrophy of brain areas associated with sensory and affective pain processing. These findings, however, have not been confirmed in all FM studies. In this study, we investigated gray matter volumes of brain areas associated with pain-related areas of FM patients identified by functional brain imaging. Using voxel-based morphometric (VBM) analysis of magnetic resonance brain images, we compared 19 pain-related brain areas of 14 female FM patients and 11 healthy controls (NC). We found that FM patients had significantly less gray matter volumes than NC in 3 of these brain regions, including the anterior and mid-cingulate, as well as mid-insular cortices. Importantly, FM patients demonstrated neither global gray matter atrophy nor gray matter changes associated with depression, as shown in some studies. Using a more stringent analysis than other VBM studies, we provide evidence for decreased gray matter volumes in a number of pain-related brain areas in FM. Although the mechanisms for these gray matter changes are presently unclear, they may contribute to some of the core features of this chronic disorder including affective disturbances and chronic widespread pain. ⋯ Increasing evidence supports the association of chronic pain with accelerated gray matter atrophy in pain disorders like low back pain, IBS, and FM syndrome. However, cause-effect relationships between chronic pain and decreased gray matter volumes have not been established yet and will require future prospective studies.
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Global ratings of treatment satisfaction and improvement can provide an opportunity for patients to aggregate multiple aspects of their treatment into a single measure of its perceived benefits and disadvantages. Although such measures have been recommended for chronic pain clinical trials, only limited data are available that address the hypothesis that they reflect multiple aspects of patients' treatment experience. Our objective was to identify the factors that make independent contributions to ratings of treatment satisfaction. We analyzed data from 5 open-label clinical trials of lidocaine patch 5% in osteoarthritis knee pain and chronic low back pain that were 2 to 12 weeks in duration. A total of 383 patients completed the Patient Global Assessment of Treatment Satisfaction scale and measures of pain, interference with physical and emotional functioning, sleep interference, and adverse events. The results of multivariate analyses indicated that improvements in measures of pain intensity, pain relief, and interference with physical functioning each made independent contributions to treatment satisfaction in both groups of patients. Improvements in interference with emotional functioning and sleep and the presence and severity of adverse events were not associated with satisfaction. ⋯ Measures of treatment satisfaction can reflect different aspects of the patient's treatment response, including improvements in pain and physical functioning. Increased understanding of such global measures may facilitate development of clinical trial outcomes that allow patients to evaluate with minimal burden those aspects of the treatment experience they consider personally meaningful.
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The Tampa Scale for Kinesiophobia (TSK) is one of the most frequently employed measures for assessing pain-related fear in pain patients. Although the TSK has been translated into different languages, a Spanish version of the TSK has not been available, up to now. Thus, the aim of this study was to validate the Spanish version of the TSK in 2 different pain samples: A heterogeneous chronic pain sample (n = 125) and a musculoskeletal acute pain sample (n = 86). Factor analysis revealed a 2-factor model of 11 items replicated on both samples, named TSK-11. The instrument obtained shows good reliability (internal consistency and stability) and validity (convergent and predictive), with the advantage of brevity. Evidence is provided on discriminant validity between both TSK factors (called Activity Avoidance and Harm). The Harm factor shows the best predictive validity, as it predicts pain persistence, catastrophizing, depression, and pain intensity scores after 6 months. Changes in the Activity Avoidance factor are positively correlated with changes in catastrophizing and anxiety, and negatively associated with changes in functional status. The results of this study point to the relative contribution of both components of pain-related fear to pain adjustment. ⋯ This article presents the Spanish version of the TSK. Factor analysis revealed a 2-factor model (called Activity Avoidance and Harm). The version obtained shows good reliability and validity. Results provide clinicians with access to a measure of pain-related fear for Spanish-speaking pain patients, offering the advantage of brevity.
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To investigate the pain-modulatory effects of a local inflammatory stimulus on pain elsewhere in the body, capsaicin was applied topically to the forearm of 14 healthy female volunteers. Pressure-pain thresholds and sensitivity to sharpness were assessed on each side of the forehead twice per day during 48 hours of capsaicin treatment, and in the treated and contralateral forearm before and at the end of treatment. Heat was applied to the treated area to rekindle pain at times of forehead assessment. Hyperalgesia to sharpness, but not pressure pain, developed in the treated area whereas sensations remained stable in the contralateral forearm. Sharpness ratings decreased bilaterally in the forehead after 6 hours of treatment, and ipsilateral analgesia to pressure pain developed in the forehead when the capsaicin site was heated after 48 hours of treatment. These findings suggest that pain modulation involves unilateral regulatory mechanisms in addition to local and generalized pain control. The dissociated changes to sharpness and pressure pain indicate distinct cutaneous and deep central pain pathways. ⋯ The findings lend support to an increasing body of research which demonstrates that pain modulation involves hemilateral mechanisms in addition to local and generalized controls. Elucidation of mechanisms that modulate ipsilateral pain processing may help to clarify the pathophysiology of complex regional pain syndrome, which is characterized by hemilateral hyperalgesia.
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Persistent shoulder pain is a common complication after stroke. Its etiology and underlying mechanisms are not well understood and treatment is generally unsatisfactory. The objective of this study was to assess the role of central sensitization and disinhibition in chronic stroke patients with chronic PSSP (n = 19), pain-free stroke patients (n = 29), and healthy controls (n = 23). Positive and negative somatosensory symptoms and signs were assessed using clinical examination and electrical and mechanical quantitative sensory testing (QST). Conditioned pain modulation (CPM) was assessed by comparing QST thresholds before and after applying a cold pressor test. Sensory abnormalities were more frequently observed and more severe in patients with PSSP, including positive signs such as allodynia at the affected side and generalized hyperalgesia at the unaffected side. CPM was similar in stroke patients and healthy controls. This study showed that chronic PSSP was associated with several positive and negative somatosensory signs, implicating a role for central sensitization and possibly for disinhibition. Since the causal relationship remains unclear, and may be related to either neuroplasticity induced by ongoing nociception as well as to the neuropathic brain lesion, prospective studies are warranted. ⋯ The assessment of somatosensory symptoms and signs and endogenous pain modulation demonstrated a role for central sensitization and possibly for disinhibition in chronic PSSP. Prevention and treatment of PSSP could benefit from a more detailed analysis of both peripheral and central pain mechanisms.