Pain
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In 14 patients with unilateral persistent idiopathic facial pain (PIFP), classified according to the criteria of the International Headache Society, and 16 age-matched control subjects sensory functions were examined on the face by quantitative sensory testing (QST). Additionally, the somatotopy of the primary somatosensory cortex (SI) to tactile input from the pain area was evaluated by means of magnetoencephalography. Previously reported abnormalities in PIFP as a dishabituation of the R2 component of the blink reflex and psychiatric disturbances were co-evaluated. ⋯ The interhemispheric difference in distance between the cortical representation of the lip and the index finger did not differ between patients and control subjects. Psychiatric evaluation did not disclose significant abnormalities at a group level. It is concluded that PIFP is maintained by mechanisms which do not involve somatosensory processing of stimuli from the pain area.
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Comparative Study
Prolonged rhythmic gum chewing suppresses nociceptive response via serotonergic descending inhibitory pathway in humans.
Serotonergic (5-HT) neurons are implicated in modulating nociceptive transmission. It is established that 5-HT neuronal activity is enhanced by rhythmic behaviors such as chewing and locomotion in animals. We thus hypothesized that 5-HT descending inhibitory pathways may be enhanced by rhythmic behavior of gum chewing in humans. ⋯ The WB 5-HT level obtained 30 min after cessation of chewing was significantly greater than the pre-chewing level. Serotonin transporters have recently been discovered at the blood-brain barrier, suggesting that the rise in blood 5-HT may possibly reflect an increase in 5-HT level within the brain. The present results support our hypothesis that the rhythmic behavior of chewing suppresses nociceptive responses via the 5-HT descending inhibitory pathway.
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Paclitaxel is an effective antineoplastic drug treatment used as an anti-tumoral therapy. Unfortunately its use is associated with unwanted side effects, which include the development of peripheral neuropathies and neuropathic pain, greatly affecting the quality of life of patients. It is well known that agonists of the cannabinoid receptor are able to reduce hyperalgesia and allodynia that develop after nerve injury. ⋯ This effect was antagonized by SR 141716A, suggesting the involvement of the CB1 receptor, although the participation of CB2 receptors cannot be excluded from this study. When WIN 55,212-2 was administered intraplantar, no differences were observed between the injected paw and the contralateral paw, suggesting that systemic mechanisms are needed to reach effectiveness. From these results we suggest that cannabinoids may be an interesting alternative to reduce neuropathic symptoms induced by paclitaxel, however more work is required to assess this possibility.
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Multicenter Study Comparative Study Controlled Clinical Trial
Reliability of clinical temporomandibular disorder diagnoses.
Temporomandibular disorders (TMD) diagnoses can be viewed as the most useful clinical summary for classifying subtypes of TMD. The Research Diagnostic Criteria for TMD (RDC/TMD) is the most widely used TMD diagnostic system for conducting clinical research. It has been translated into 18 languages and is used by a consortium of 45 RDC/TMD-based international researchers. ⋯ The reliability of diagnostic classification improved when diagnoses were grouped into pain versus non-pain diagnoses (ICC=0.72) and for detecting any diagnosis versus no diagnosis (ICC=0.78). In clinical decision-making and research, arriving at a reliable diagnosis is critical in establishing a clinical condition and a rational approach to treatment. The RDC/TMD demonstrates sufficiently high reliability for the most common TMD diagnoses, supporting its use in clinical research and decision making.
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Comparative Study
Isometric exercise has opposite effects on central pain mechanisms in fibromyalgia patients compared to normal controls.
Aerobic exercise has been shown to activate endogenous opioid and adrenergic systems and attenuate experimental pain in normal control subjects (NC). In contrast, fibromyalgia (FM) subjects' experimental pain ratings increase after aerobic exercise, suggestive of abnormal pain modulation. In order to determine whether central or peripheral mechanisms are predominantly involved in the abnormal pain modulation of FM patients, the effects of handgrip exercise on thermal (cutaneous) and mechanical (somatic) experimental pain was tested in local as well as remote body areas of FM and NC subjects. ⋯ Thus, sustained local muscular contraction induced widespread pain inhibitory effects in NC. In contrast, the widespread hyperalgesic effects of exercise on FM patients clearly indicate altered central pain mechanisms. However, whether these exercise effects of FM patients result from abnormal descending inhibition or excessive activation of muscle nociceptive afferents needs to be addressed in future studies.