Pain
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The painDETECT Questionnaire (PDQ) is commonly used as a screening tool to discriminate between neuropathic pain (NP) and nociceptive pain, based on the self-report of symptoms, including pain qualities, numbness, and pain to touch, cold, or heat. However, there are minimal data about whether the PDQ is differentially sensitive to different sensory phenotypes in NP. The aim of the study was to analyze whether the overall PDQ score or its items reflect phenotypes of sensory loss in NP as determined by quantitative sensory testing. ⋯ Patients with loss of thermal sensation (2 and 4) significantly more often reported pain evoked by light touch, and patients with loss of mechanical sensation (3 and 4) significantly more often reported numbness and significantly less often burning sensations and pain evoked by light touch. Although the PDQ was not designed to assess sensory loss, single items reflect thermal and/or mechanical sensory loss at group level, but because of substantial variability, the PDQ does not allow for individual allocation of patients into sensory profiles. It will be useful to develop screening tools according to the current definition of NP.
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With the increased interest in longitudinal brain imaging of awake rodents, it is important to understand both the short-term and long-term effects of restraint on sensory and emotional processing in the brain. To understand the effects of repeated restraint on pain behaviors and stress responses, we modeled a restraint protocol similar to those used to habituate rodents for magnetic resonance imaging scanning, and studied sensory sensitivity and stress hormone responses over 5 days. ⋯ We found that while restraint causes acute increases in the stress hormone corticosterone, it can also cause lasting reductions in nociceptive behavior in the formalin test, coupled with heightened corticosterone levels and increased activation of the "nociceptive" central nucleus of the amygdala, as seen by Fos protein expression. These results suggest that short-term repeated restraint, similar to that used to habituate rats for awake functional brain scanning, could potentially cause long-lasting changes in physiological and brain responses to pain stimuli that are stress-related, and therefore could potentially confound the functional activation patterns seen in awake rodents in response to pain stimuli.
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Migraine and other primary headache disorders affect a large population and cause debilitating pain. Establishing animal models that display behavioral correlates of long-lasting and ongoing headache, the most common and disabling symptom of migraine, is vital for the elucidation of disease mechanisms and identification of drug targets. We have developed a mouse model of headache, using dural application of capsaicin along with a mixture of inflammatory mediators (IScap) to simulate the induction of a headache episode. ⋯ In addition, dural application of IScap increased resting time in female mice. Taken together, we present the first detailed study using dural application of IScap in mice. This headache model can be applied to genetically modified mice to facilitate research on the mechanisms and therapeutic targets for migraine headache.
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The redefinition of neuropathic pain as "pain arising as a direct consequence of a lesion or disease affecting the somatosensory system," which was suggested by the International Association for the Study of Pain (IASP) Special Interest Group on Neuropathic Pain (NeuPSIG) in 2008, has been widely accepted. In contrast, the proposed grading system of possible, probable, and definite neuropathic pain from 2008 has been used to a lesser extent. Here, we report a citation analysis of the original NeuPSIG grading paper of 2008, followed by an analysis of its use by an expert panel and recommendations for an improved grading system. ⋯ Obstacles to a wider use of the grading system were identified, including (1) questions about the relative significance of confirmatory tests, (2) the role of screening tools, and (3) uncertainties about what is considered a neuroanatomically plausible pain distribution. Here, we present a revised grading system with an adjusted order, better reflecting clinical practice, improvements in the specifications, and a word of caution that even the "definite" level of neuropathic pain does not always indicate causality. In addition, we add a table illustrating the area of pain and sensory abnormalities in common neuropathic pain conditions and propose areas for further research.
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During long-term opioid therapy for chronic noncancer pain, monitoring medication adherence of patients with a history of aberrant opioid medication-taking behaviors (AMTB) is an essential practice. There is limited research, however, into the concordance among existing monitoring tools of self-report, physician report, and biofluid screening. This study examined associations among patient and provider assessments of AMTB and urine drug screening using data from a randomized trial of a cognitive-behavioral intervention designed to improve medication adherence and pain-related outcomes among 110 opioid-treated patients with chronic pain who screened positive for AMTB and were enrolled in a pain program. ⋯ However, the ABC ratings of experienced providers (nurse practitioners/attending physicians) were higher than those of less experienced providers (fellows) and were correlated with CCI scores and risk factors for AMTB. Associations between patient- and provider-reported AMTB and urine drug screening results were low and largely nonsignificant. In conclusion, concordance between patient and provider reports of AMTB among patients with chronic pain prescribed opioid medication varied by provider level of training.