Pain
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As part of a comprehensive study of the natural history of herpes zoster (HZ), 57 of 94 subjects in a cohort at elevated risk for post-herpetic neuralgia (PHN) consented to collection of 3-mm skin punch biopsies from affected, mirror-image, and distant control skin at baseline and followup visits. As cutaneous innervation is reduced in longstanding severe PHN, we tested the hypothesis that development of PHN is correlated with severity of initial neural injury and/or a failure of neural recovery. Quantitative analysis using single-label PGP9.5 immunofluorescence microscopy showed epidermal profiles were reduced in zoster skin by approximately 40% at study entry compared to control and mirror skin. ⋯ Sensory abnormalities and symptom aggravation by focal capsaicin application showed partial and selective recovery over 6months. In contrast, cutaneous innervation showed no recovery at all by 6months, conclusive evidence that resolution of pain and allodynia does not require cutaneous reinnervation. A much longer period of observation is needed to determine if zoster-affected skin is ever reinnervated.
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Muscular tension is assigned an important role in the development and maintenance of chronic pain syndromes. It is seen as a psychophysiological correlate of learned fear and avoidance behavior. Basic theoretical models emphasize classical conditioning of muscular responses as a mechanism of pain chronification. ⋯ Furthermore a significant relation was found between muscular responses and the experience of pain 1day after the experiment. Muscular responses can be learned via classical conditioning. TTH and BP patients revealed a higher number of unconditioned and conditioned responses.
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This paper describes the psychometric properties of the PROMIS-pain interference (PROMIS-PI) bank. An initial candidate item pool (n=644) was developed and evaluated based on the review of existing instruments, interviews with patients, and consultation with pain experts. From this pool, a candidate item bank of 56 items was selected and responses to the items were collected from large community and clinical samples. ⋯ The scores discriminated among persons with different numbers of chronic conditions, disabling conditions, levels of self-reported health, and pain intensity (p<0.0001). The results indicated that the PROMIS-PI items constitute a psychometrically sound bank. Computerized adaptive testing and short forms are available.
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This study aimed to identify distinctive trajectories for pain/disability and posttraumatic stress disorder (PTSD) symptoms following whiplash injury and to examine the effect of injury compensation claim lodgement on the trajectories. In a prospective study, 155 individuals with whiplash were assessed at <1month, 3, 6 and 12months post injury. Outcomes at each time point were Neck Disability Index (NDI) and the Posttraumatic Stress Diagnostic Scale (PDS). ⋯ Following whiplash injury, there are distinct pathways of recovery for pain/ disability and PTSD symptoms. Management of whiplash should consider the detrimental association of compensation claim with psychological recovery and recovery of those with mild to moderate pain/disability levels. However, claim lodgement has no significant association with a more severe pain and disability trajectory.
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Behavioral studies have suggested that placebo analgesia is partly mediated by the endogenous opioid system. Expanding on these results we have shown that the opioid-receptor-rich rostral anterior cingulate cortex (rACC) is activated in both placebo and opioid analgesia. However, there are also differences between the two treatments. ⋯ Furthermore, the rACC activity co-varied with the prefrontal regions in the placebo condition specifically. A similar correlation between rACC and vlPFC was reproduced in another dataset involving emotional placebo and correlated with the degree of the placebo effect. Our results thus support that placebo is different from specific treatment with a prefrontal top-down influence on rACC.