The journal of pain : official journal of the American Pain Society
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Comparative Study
The specificity and mechanisms of hemilateral sensory disturbances in complex regional pain syndrome.
Hyperalgesia often extends from the affected limb to the ipsilateral forehead in patients with complex regional pain syndrome (CRPS). To investigate whether this is more common in CRPS than other chronic pain conditions, pressure-pain thresholds and sharpness to a firm bristle were assessed on each side of the forehead, at the pain site, and at an equivalent site on the contralateral side in 32 patients with chronic pain other than CRPS (neuropathic or nociceptive limb pain, radicular pain with referral to a lower limb or postherpetic neuralgia), and in 34 patients with CRPS. Ipsilateral forehead hyperalgesia to pressure pain was detected in 59% of CRPS patients compared with only 13% of patients with other forms of chronic pain. Immersion of the CRPS-affected limb in painfully cold water increased forehead sensitivity to pressure, especially ipsilaterally, whereas painful stimulation of the healthy limb reduced forehead sensitivity to pressure pain (albeit less efficiently than in healthy controls). In addition, auditory discomfort and increases in pain in the CRPS-affected limb were greater after acoustic startle to the ear on the affected than unaffected side. These findings indicate that generalized and hemilateral pain control mechanisms are disrupted in CRPS, and that multisensory integrative processes may be compromised. ⋯ The findings suggest that hemilateral hyperalgesia is specific to CRPS, which could be diagnostically important. Disruptions in pain-control mechanisms were associated with the development of hyperalgesia at sites remote from the CRPS limb. Addressing these mechanisms could potentially deter widespread hyperalgesia in CRPS.
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Randomized Controlled Trial Multicenter Study Comparative Study
A qualitative analysis of a randomized controlled trial comparing a cognitive-behavioral treatment with education.
Cognitive behavioral therapy (CBT) is a widely accepted psychosocial treatment for chronic pain. However, the efficacy of CBT has not been investigated within a rural setting. Furthermore, few studies have utilized first-person accounts to qualitatively investigate the key treatment elements and processes of change underlying the well-documented quantitative improvements associated with CBT. To address these gaps, we conducted a randomized controlled trial (RCT) investigating the efficacy of group CBT compared to an active education condition (EDU) within a rural, low-literacy population. Posttreatment semistructured interviews of 28 CBT and 24 EDU treatment completers were qualitatively analyzed. Emerging themes were collated to depict a set of finalized thematic maps to visually represent the patterns inherent in the data. Patterns were separated into procedural elements and presumed change processes of treatment. Key themes, subthemes, and example extracts for CBT and EDU are presented; unique and shared aspects pertaining to the thematic maps are discussed. Results indicate that while both groups benefited from the program, the CBT group described more breadth and depth of change as compared to the EDU group. Importantly, this study identified key treatment elements and explored possible processes of change from the patients' perspective. ⋯ This qualitative article describes patient-identified key procedural elements and change process factors associated with psychosocial approaches for chronic pain management. Results may guide further adaptations to existing treatment protocols for use within unique, underserved chronic pain populations. Continued development of patient-centered approaches may help reduce health, treatment, and ethnicity disparities.
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Comparative Study
Preservation of acute pain and efferent functions following intrathecal resiniferatoxin-induced analgesia in rats.
Resiniferatoxin (RTX) is a potent agonist of TRPV1, which possesses unique properties that can be utilized to treat certain modalities of pain. In the present study, systemic intraperitoneal (i.p.) administration of RTX resulted in a significant decrease in acute thermal pain sensitivity, whereas localized intrathecal (i.t.) administration had no effect on acute thermal pain sensitivity. Both i.p. and i.t. administration of RTX prevented TRPV1-induced nocifensive behavior and inflammatory thermal hypersensitivity. There were no alterations in mechanical sensitivity either by i.p. or i.t. administration of RTX. In spinal dorsal horn (L4-L6), TRPV1 and substance P immunoreactivity were abolished following i.p. and i.t. administration of RTX. In dorsal root ganglia (DRG), TRPV1 immunoreactivity was diminished following i.p. administration, but was unaffected following i.t. administration of RTX. Following i.p. administration, basal and evoked calcitonin gene-related peptide release were reduced both in the spinal cord and peripheral tissues. However, following i.t. administration, basal and evoked calcitonin gene-related peptide release were reduced in spinal cord (L4-L6), but were unaffected in peripheral tissues. Both i.p. and i.t. RTX administration lowered the body temperature acutely, but this effect reversed with time. Targeting TRPV1-expressing nerve terminals at the spinal cord can selectively abolish inflammatory thermal hypersensitivity without affecting acute thermal sensitivity and can preserve the efferent functions of DRG neurons at the peripheral nerve terminals. I.t. administration of RTX can be considered as a strategy for treating certain chronic and debilitating pain conditions. ⋯ Localized administration of RTX in spinal cord could be a useful strategy to treat chronic debilitating pain arising from certain conditions such as cancer and at the same time could maintain normal physiological peripheral efferent functions mediated by TRPV1.
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Comparative Study
Involvement of spinal neurotrophin-3 in electroacupuncture analgesia and inhibition of spinal glial activation in rat model of monoarthritis.
Although electroacupuncture (EA) has been proven to effectively relieve pain associated with arthritis, the underlying mechanism of EA analgesia requires further investigation. Here, the involvement of spinal neurotrophin-3 (NT-3) in EA's analgesic effects on complete Freund's adjuvant (CFA)-induced inflammatory pain was examined. The present study demonstrated that: 1) repeated EA stimulation of ipsilateral GB30 and GB34 acupoints remarkably suppressed CFA-induced hyperalgesia; 2) EA treatment markedly enhanced the upregulation of spinal NT-3 mRNA and protein levels following CFA injection; 3) antisense oligodeoxynucleotides (ODN) specifically against NT-3 intrathecally administered during EA treatment for 7 days significantly attenuated the EA analgesia; and 4) the suppressed expression of spinal GFAP (astrocytic marker), OX-42 (microglial marker) as well as proinflammatory cytokines, interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α by EA treatment was significantly attenuated following NT-3 antisense ODN delivery. These results suggested that endogenous NT-3 may be involved in the analgesic effect of EA on inflammatory pain in rats, mediated through the inhibition of spinal glial activity as well as proinflammatory cytokine production. ⋯ The present study may initiate a discussion on the possible roles of NT-3/glia/cytokines in the therapeutic effects of acupuncture and provide insight on the mechanism underlie the analgesic effects of acupuncture on pain associated with arthritis.
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Randomized Controlled Trial Multicenter Study Comparative Study
Reciprocal relationship between pain and depression: a 12-month longitudinal analysis in primary care.
Pain and depression are the most prevalent physical and psychological symptom-based disorders, respectively, and co-occur 30 to 50% of the time. However, their reciprocal relationship and potentially causative effects on one another have been inadequately studied. Longitudinal data analysis involving 500 primary care patients with persistent back, hip, or knee pain were enrolled in the Stepped Care for Affective Disorders and Musculoskeletal Pain (SCAMP) study. Half of the participants had comorbid depression and were randomized to a stepped care intervention (n = 123) or treatment as usual (n = 127). Another 250 nondepressed patients with similar pain were followed in a parallel cohort. Outcomes were assessed at baseline, 3, 6, and 12 months. Mixed effects model repeated measures (MMRM) multivariable analyses were conducted to determine if change in pain severity predicted subsequent depression severity, and vice versa. Change in pain was a strong predictor of subsequent depression severity (t-value = 6.63, P < .0001). Likewise, change in depression severity was an equally strong predictor of subsequent pain severity (t-value = 7.28, P < .0001). Results from the full cohort were similar in the clinical trial subgroup. In summary, pain and depression have strong and similar effects on one another when assessed longitudinally over 12 months. ⋯ This study strengthens the evidence for a bidirectional and potentially causative influence of pain and depression on one another. A change in severity of either symptom predicts subsequent severity of the other symptom. Thus, recognition and management of both conditions may be warranted, particularly when treatment focused on 1 condition is not leading to an optimal response.