The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial
Repetitive transcranial magnetic stimulation is efficacious as an add-on to pharmacological therapy in complex regional pain syndrome (CRPS) type I.
Single-session repetitive transcranial magnetic stimulation (rTMS) of the motor cortex (M1) is effective in the treatment of chronic pain patients, but the analgesic effect of repeated sessions is still unknown. We evaluated the effects of rTMS in patients with refractory pain due to complex regional pain syndrome (CRPS) type I. Twenty-three patients presenting CRPS type I of 1 upper limb were treated with the best medical treatment (analgesics and adjuvant medications, physical therapy) plus 10 daily sessions of either real (r-) or sham (s-) 10 Hz rTMS to the motor cortex (M1). Patients were assessed daily and after 1 week and 3 months after the last session using the Visual Analogical Scale (VAS), the McGill Pain Questionnaire (MPQ), the Health Survey-36 (SF-36), and the Hamilton Depression (HDRS). During treatment there was a significant reduction in the VAS scores favoring the r-rTMS group, mean reduction of 4.65 cm (50.9%) against 2.18 cm (24.7%) in the s-rTMS group. The highest reduction occurred at the tenth session and correlated to improvement in the affective and emotional subscores of the MPQ and SF-36. Real rTMS to the M1 produced analgesic effects and positive changes in affective aspects of pain in CRPS patients during the period of stimulation. ⋯ This study shows an efficacy of repetitive sessions of high-frequency rTMS as an add-on therapy to refractory CRPS type I patients. It had a positive effect in different aspects of pain (sensory-discriminative and emotional-affective). It opens the perspective for the clinical use of this technique.
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Based on prior research identifying dispositional optimism as a predictor of placebo responding, the present study tested the hypothesis that individuals high in optimism would be more likely to respond to a placebo analgesic. Optimists and pessimists were randomly assigned to a placebo expectation condition or a no expectation condition before a cold pressor task. Blood pressure and heart rate were recorded before and during the cold pressor task, and participant ratings of pain and expectations were obtained immediately after the task. Analysis of the expectation manipulation revealed that the placebo instruction was successful in altering participant expectancy during the cold pressor. Supporting the main hypothesis, dispositional optimism was associated with lower pain ratings in the placebo condition but not in the control condition. Because dispositional optimism can alter placebo responding to laboratory pain, future studies should examine the potential role that this individual difference factor may play in patient responsivity to pharmacological and nonpharmacological treatments for clinical pain. ⋯ This study examined the possibility that individual differences can predict placebo analgesia. Participants were randomly assigned to receive either a placebo expectation or no expectation before a cold pressor task. Dispositional optimism was related to less cold pressor pain in the placebo condition as compared with the control condition.
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A cross-sectional, Internet-based survey was conducted in a nationally representative sample of United States (US) adults to estimate the point prevalence of chronic pain and to describe sociodemographic correlates and characteristics of chronic pain. The survey was distributed to 35,718 members (aged 18 years and older) of a Web-enabled panel that is representative of the US population, and 27,035 individuals responded. Crude and weighted prevalence estimates were calculated and stratified by age, sex, and type of chronic pain. The weighted point-prevalence of chronic pain (defined as chronic, recurrent, or long-lasting pain lasting for at least 6 months) was 30.7% (95% CI, 29.8-31.7). Prevalence was higher for females (34.3%) than males (26.7%) and increased with age. The weighted prevalence of primary chronic lower back pain was 8.1% and primary osteoarthritis pain was 3.9%. Half of respondents with chronic pain experienced daily pain, and average (past 3 months) pain intensity was severe (≥ 7 on a scale ranging from 0 to 10) for 32%. Multiple logistic regression analysis identified low household income and unemployment as significant socioeconomic correlates of chronic pain. Chronic pain is prevalent among US adults and is related to indicators of poorer socioeconomic status. ⋯ The results of this cross-sectional Internet-based survey suggest a considerable burden of chronic pain in US adults. Chronic pain, experienced by about a third of the population, was correlated with indicators of poorer socioeconomic status. Primary chronic pain was most commonly attributed to lower back pain, followed by osteoarthritis pain.
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The formalin test produces 2 well-known acute phases of nociceptive behavior. Recently, we have shown that this same formalin test produces a third phase of nociceptive behavior consisting of prolonged thermal and mechanical hyperalgesia beginning days after formalin injection and lasting for at least 3 weeks. Here we investigated the activity of 3 MAPKs (p38, ERK and JNK) in the spinal dorsal horn following 5% formalin injection into rat hind paw. The p38 MAPK was rapidly activated in the spinal microglia minutes after injection and the activation persisted for 1 hour. In addition, this same injury induced a secondary increase of phospho-p38 expression in spinal microglia that was maximal 3 to 7 days postinjection. Intrathecal administration of p38 inhibitor SB203580 not only inhibited the early acute spontaneous nociceptive behaviors, but also inhibited the long-term formalin injury-induced mechanical hyperalgesia. Our results suggest that peripheral formalin injection induces 2 stages of microglial activation, and p38 activation in spinal microglia plays key roles in central pain modulation in formalin test respectively for the early acute phases and the late secondary long-term pain state as well. ⋯ This article presents unique properties of spinal microglial activation in a pain animal model. This finding could potentially help clinicians to further understand the contributions of spinal microglia to acute and chronic pain state.
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This study examined characteristics associated with prescription drug use disorder (PDUD) in primary-care patients with chronic pain from a cross-sectional survey conducted at an urban academically affiliated safety-net hospital. Participants were 18 to 60 years old, had pain for ≥ 3 months, took prescription or nonprescription analgesics, and spoke English. Measurements included the Composite International Diagnostic Interview (PDUD, other substance use disorders (SUD), Posttraumatic Stress Disorder [PTSD]); Graded Chronic Pain Scale, smoking status; family history of SUD; and time spent in jail. Of 597 patients (41% male, 61% black, mean age 46 years), 110 (18.4%) had PDUD of whom 99 (90%) had another SUD. In adjusted analyses, those with PDUD were more likely than those without any current or past SUD to report jail time (OR 5.1, 95% CI 2.8-9.3), family history of SUD (OR 3.4, 1.9-6), greater pain-related limitations (OR 3.8, 1.2-11.7), cigarette smoking (OR 3.6, 2-6.2), or to be white (OR 3.2, 1.7-6), male (OR 1.9, 1.1-3.5) or have PTSD (OR 1.9, 1.1-3.4). PDUD appears increased among those with easily identifiable characteristics. The challenge is to determine who, among those with risk factors, can avoid, with proper management, developing the increasingly common diagnosis of PDUD. ⋯ This article examines risk factors for prescription drug use disorder (PDUD) among a sample of primary-care patients with chronic pain at an urban, academic, safety-net hospital. The findings may help clinicians identify those most at risk for developing PDUD when developing appropriate treatment plans.