Pain
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Comparative Study
Intramuscular injection of tumor necrosis factor-alpha induces muscle hyperalgesia in rats.
The role of proinflammatory cytokines in neuropathic and inflammatory pain is well established. Recent studies suggest that cytokines such as tumor necrosis factor-alpha (TNF) may also be involved in the development of muscle pain. To investigate the pathophysiology of intramuscular TNF, exogenous TNF (0.1-10 microg), formalin (9%) or vehicle was injected into the gastrocnemius or biceps brachii muscles of rats. ⋯ TNF and formalin evoked intramuscular upregulation of CGRP and NGF, whereas PGE2 was increased exclusively after TNF injection. These findings allow us to speculate that endogenous TNF may play a role in the development of muscle hyperalgesia. Targeting proinflammatory cytokines might be beneficial for the treatment of musculoskeletal pain syndromes.
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Comparative Study
Contributing factors to chronic myofascial pain: a case-control study.
This case-control study was designed to investigate the contributing factors for chronic masticatory myofascial pain (MFP). Eighty-three patients with MFP, selected from the dental clinics of the Jewish General and Montreal General Hospitals, Montreal, Canada, and 100 concurrent controls selected only at the first clinic, participated in this study. The association with MFP was evaluated for bruxism, head-neck trauma, psychological factors (symptom check list 90 revised questionnaire, SCL-90R) and sociodemographic characteristics by using unconditional logistic regression. ⋯ In addition, female gender had almost three times the risk of chronic MFP than males when the model was also adjusted for psychological symptoms. Grinding-only, age, household income and education were not related with chronic MFP. Tooth clenching, trauma and female gender may contribute to MFP even when other psychological symptoms are similar between subjects.
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Comparative Study
Facial arthralgia and myalgia: can they be differentiated by trigeminal sensory assessment?
Heat and electrical detection thresholds were assessed in 72 patients suffering from painful temporomandibular disorder. Employing widely accepted criteria, 44 patients were classified as suffering from temporomandibular joint (TMJ) arthralgia (i.e. pain originating from the TMJ) and 28 from myalgia (i.e. pain originating from the muscles of mastication). Electrical stimulation was employed to assess thresholds in large myelinated nerve fibers (Abeta) and heat application to assess thresholds in unmyelinated nerve fibers (C). ⋯ Following arthrocentesis, mean electrical detection threshold ratios in the AUT territory were significantly elevated from 0.64+/-0.06 to 0.99+/-0.04 indicating resolution of the hypersensitivity (paired t-test, P=0.001). In conclusion, large myelinated fiber hypersensitivity is found in the skin overlying TMJs with clinical pain and pathology but is not found in controls. In patients with muscle-related facial pain there was significant elevation of the electrical detection threshold in the AUT region.
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Recent clinical studies showed that acute migraine attacks are accompanied by increased periorbital and bodily skin sensitivity to touch, heat and cold. Parallel pre-clinical studies showed that the underlying mechanism is sensitization of primary nociceptors and central trigeminovascular neurons. The present study investigates the sensory state of neuronal pathways that mediate skin pain sensation in migraine patients in between attacks. ⋯ The absence of clinically or overt laboratory expressed allodynia suggests that pain pathways are not sensitized in the pain-free migraine patients. Nevertheless, the increased temporal summation, and the slight decrease in mechanical pain thresholds, suggest that central nociceptive neurons do express activation-dependent plasticity. These findings may point to an important pathophysiological change in membrane properties of nociceptive neurons of migraine patients; a change that may hold a key to more effective prophylactic treatment.
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A patient's readiness to adopt a self-management approach to pain has been suggested as a construct that may explain differences among patients in coping, adjustment, and response to multidisciplinary pain treatment. The pain stages of change questionnaire (PSOCQ; Pain, 72 (1997) 227) was designed to assess four components of this construct. ⋯ The findings supported the first hypothesis and provided mixed support for the second. The implications of the findings for understanding the readiness to self-manage pain construct and the validity of the PSOCQ for assessing this construct are discussed.