Pain
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Previous studies on sensory function in persistent postherniotomy pain (PPP) have only identified pressure pain threshold to be significantly different from pain-free patients despite several patients reporting cutaneous pain and wind-up phenomena. However the limited number of patients studied hinders evaluation of potential subgroups for further investigation and/or treatment allocation. Thus we used a standardized QST protocol to evaluate sensory functions in PPP and pain-free control patients, to allow individual sensory characterization of pain patients from calculated Z-values. ⋯ A high incidence (26%) of pressure hyperalgesia was found in the contralateral groin, with a significant correlation (rho=0.58, p=0.002) to the hyperalgesic level on the painful side, again suggesting central nervous mechanisms in PPP. In conclusion, this study shows that a standardized trauma results in heterogeneous combinations of hypo- and hyperalgesia. Z-score evaluation of sensory function identifies subpopulations in PPP, which may be used in selecting surgical and/or pharmacological treatment strategies.
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Chronic stressful events induce biochemical, physiological and psychological changes, resulting in stress-related neuropsychiatric disorders, such as anxiety or depression. Using repeated social defeat as a stressful event model, we show that this preclinical paradigm induces a transient increase in the expression of the genes encoding the pro-inflammatory molecules iNOS and COX-2. We provide the first demonstration that chronic stress affects spinal plasticity through a mechanism involving local neuroinflammation. ⋯ The present study highlights the adverse effects of chronic stress on spinal neuroinflammation triggering sensory hypersensitivity. Exploration of this phenomenon points out the divergence between pain sensitivity and anxiety-induced hyperalgesia, which is in agreement with clinical observations. Altogether, these data open up new perspectives for clinical research devoted to the evaluation and treatment of pain in anxio-depressive patients.
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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.