Pain
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Randomized Controlled Trial Comparative Study
Comparison of glutamate-evoked pain between the temporalis and masseter muscles in men and women.
Pain in myofascial temporomandibular disorder (TMD) can affect both the masseter and temporalis muscles. Glutamate injection into the masseter muscle evokes pain that is greater in men than in women and this pain is attenuated by co-injection of the N-methyl-d-aspartate (NMDA) receptor antagonist ketamine (10 mmol/L) in men. Animal studies suggested that pain induced by peripheral NMDA receptor activation could differ between the temporalis and masseter muscles and between men and women. ⋯ Women reported significantly greater glutamate-evoked masseter muscle pain than men (P<.03). Co-injection of ketamine, at higher dose than previously used, was equally effective in attenuating glutamate-evoked pain from both muscles in both genders (P<.01). The current findings indicate that the characteristics of pain generated by intramuscular injection of glutamate vary for different masticatory muscles and may be partially generated through activation of peripheral NMDA receptors.
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Multicenter Study Comparative Study
Sensory signs in complex regional pain syndrome and peripheral nerve injury.
This study determined patterns of sensory signs in complex regional pain syndrome (CRPS) type I and II and peripheral nerve injury (PNI). Patients with upper-limb CRPS-I (n=298), CRPS-II (n=46), and PNI (n=72) were examined with quantitative sensory testing according to the protocol of the German Research Network on Neuropathic Pain. The majority of patients (66%-69%) exhibited a combination of sensory loss and gain. ⋯ However, in contrast to recent suggestions, small fiber deficits were less frequent than large fiber deficits. Sensory gain is highly prevalent in PNI, indicating a better similarity of animal models to human patients than previously thought. These sensory profiles should help prioritize approaches for translation between animal and human research.
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Randomized Controlled Trial Comparative Study
No pain no gain? Pursuing a competing goal inhibits avoidance behavior.
This experiment investigated pain-related avoidance behavior in context of competing goals. Participants (N=56) were presented trials of 2 different tasks of which 1 task could produce pain. They were free to decide whether or not to perform trials of these tasks. ⋯ Furthermore, the association between pain-related avoidance behavior and fear of pain was smaller in the competition group than in the control group. The findings indicate that the emergence of pain-related avoidance behavior depends upon the motivational context, and that the association between pain-related fear and avoidance is not stable. This study has implications for our understanding of disability, and points to the need to consider avoidance behavior within a broad context of multiple, often competing, goals.
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This report examines day-to-day variability in rheumatology patients' ratings of pain and related quality-of-life variables as well as predictors of that variability. Data from 2 studies were used. The hypothesis was that greater psychological distress (i.e., depression and anxiety) and poorer coping appraisals (i.e., higher pain catastrophizing and lower self-efficacy) are associated with more variability. ⋯ Anxiety was not significantly associated with day-to-day variability. The results of these studies suggest that individual differences in the magnitude of symptom fluctuation may play a vital role in understanding patients' adjustment to pain. Future research will be needed to examine the clinical utility of measuring variability in patients' pain and well-being, and to understand whether reducing variability may be an important treatment target.
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Osteoarthritis (OA) is a chronic condition characterized by pain during joint movement. Additionally, patients with advanced disease experience pain at rest (ie, ongoing pain) that is generally resistant to nonsteroidal antiinflammatory drugs. Injection of monosodium iodoacetate (MIA) into the intraarticular space of the rodent knee is a well-established model of OA that elicits weight-bearing asymmetry and referred tactile and thermal hypersensitivity. ⋯ Additionally, systemic or intraarticular HC030031, a TRPA1 antagonist, failed to block high-dose MIA-induced weight asymmetry or ongoing pain. Our studies suggest that a high dose of intraarticular MIA induces ongoing pain originating from the site of injury that is dependent on afferent fiber activity but apparently independent of TRPV1 or TRPA1 activation. Identification of mechanisms driving ongoing pain may enable development of improved treatments for patients with severe OA pain and diminish the need for joint replacement surgery.