Pain
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Controlled Clinical Trial
Increased levels of interstitial potassium but normal levels of muscle IL-6 and LDH in patients with trapezius myalgia.
The mechanisms behind the development of work-related trapezius pain are suggested to involve both peripheral and central components, but the specific contribution of alterations in muscle nociceptive and other substances is not clear. Female patients with chronic trapezius myalgia (N=19; TM) and female controls (N=20; CON) were studied at rest, during 20 min repetitive low-force exercise and recovery, and had their interstitial concentrations of potassium (K(+)), lactate dehydrogenase (LDH), interleukin-6 (IL-6) and collagen turnover determined in the trapezius muscle by the microdialysis technique. K(+) levels were at all time points higher in TM than in CON (P<0.0001). ⋯ Rises in muscle LDH and IL-6 as well as the anabolic ratio for collagen type I was not significantly different between groups. In conclusion, patients with chronic pain in the trapezius muscle had increased levels of interstitial potassium. This finding could be causally related to myalgia or secondary to pain due to deconditioned muscle or altered muscle activity pattern.
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Randomized Controlled Trial
The role of threat-expectancy in acute pain: effects on attentional bias, coping strategy effectiveness and response to pain.
The aims of this study were threefold. Firstly, to investigate the effect of increasing threat-expectancy on attentional biases towards pain-related words. Secondly, to determine the interaction between threat-expectancy and the effectiveness of two coping strategies on pain threshold and tolerance. ⋯ The present results provide support for the fear-avoidance model of pain [Vlaeyen JWS, Linton SJ. Fear-avoidance and its consequences in chronic musculoskeletal pain: a state of the art. Pain 2000;85:317-332] and confirm the importance of threat-expectancy in hypervigilance towards pain and fear avoidance.
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Controlled Clinical Trial
Does medication overuse headache represent a behavior of dependence?
Medication overuse is relatively common in patients with frequent headache. To explore the prevalence of patients who meet the criteria for substance dependence in Diagnostic and Statistical Manual of Mental Disorders, Edition IV (DSM-IV), and to identify variables of substance dependence among patients with chronic daily headache, we recruited consecutive patients with chronic daily headache at a headache clinic from November 1999 to June 2004. Each patient completed a headache intake form, a dependence questionnaire modified from DSM-IV, and the Hospital Anxiety and Depression Scale (HADS). ⋯ Patients who fulfilled DSM-IV criteria of dependence had higher numbers of physician appointments in the past year. Multivariate logistic regression analyses revealed that migraine headache, frequent physician consultation, intensity of headache, and presence of a higher anxiety score were significant independent variables for substance dependence. Among patients with chronic daily headache, pMOH was associated with behaviors of substance dependence.
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Clinical Trial
An experimental study of viscero-visceral hyperalgesia using an ultrasound-based multimodal sensory testing approach.
Widespread visceral hypersensitivity and the overlap of symptom complexes observed in functional gastrointestinal disorders may be related to central sensitization and neuroplastic changes. A multimodal and multi-segmental model was developed to evaluate viscero-visceral hyperalgesia induced by experimental esophageal sensitization in healthy volunteers. Twelve healthy subjects were studied using a double-blinded, placebo-controlled design. ⋯ The present method demonstrated a new approach to assess multimodal sensitivity to experimental sensitization of the esophagus and related viscero-visceral hyperalgesia. Central mechanisms can explain the remote hyperalgesia to mechanical visceral stimulation and the increase in referred pain areas. The present method may be used to explore pathophysiology and pharmacological interventions in patients with visceral hypersensitivity.
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Nitric oxide (NO) acts as a neurotransmitter or neuromodulator involving in the modulation of thermal and/or inflammatory hyperalgesia. The neuronal nitric oxide synthase (nNOS) is a key enzyme for NO production in normal neuronal tissues, but its functional role in chronic pain remains unclear. The present study combined a genetic strategy with a pharmacologic approach to address the role of nNOS in the central mechanism of complete Freund's adjuvant (CFA)-induced chronic inflammatory pain. ⋯ Finally, spinal cord nNOS (but not endothelial NOS or inducible NOS) expression was up-regulated at 24h after CFA injection, occurring mainly in the ipsilateral superficial dorsal horn. Together, these data indicate that spinal cord nNOS may be essential for the maintenance of mechanical pain hypersensitivity and that it may also be sufficient for the development of mechanical pain hypersensitivity and for the development and maintenance of thermal pain hypersensitivity after chronic inflammation. Our findings suggest that spinal cord nNOS might play a critical role in central mechanisms of the development and/or maintenance of chronic inflammatory pain.