Pain
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Randomized Controlled Trial
Comparison of masseter muscle referred sensations after mechanical and glutamate stimulation: a randomized, double-blind, controlled, cross-over study.
Referred sensations (RS) are commonly found in various musculoskeletal pain conditions. Experimental studies have shown that RS can be elicited through glutamate injection and mechanical stimulation. Despite this, differences and similarities between these modalities in RS outcomes remain unclear. ⋯ Hence, RS does not seem to be modality-dependent, and only the painfulness of the stimulus caused an increase in frequency of RS. Finally, RS location for each participant was similar in both sessions possibly indicating a preferred location of referral. These findings may have implications for our understanding of RS in craniofacial pain conditions.
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Patellofemoral pain (PFP) is a common and recurrent knee condition in young females, characterized by pressure hyperalgesia and reduced pain inhibitory control. This study investigated antinociceptive and pronociceptive profiles in young females with long-standing (>5 years) PFP (current-PFP), those who recovered from adolescent PFP (recovered-PFP), and pain-free controls. This preregistered, assessor-blinded, cross-sectional study included 87 females younger than 25 years: 36 current-PFP, 22 recovered-PFP, and 29 pain-free controls. ⋯ Compared with controls, the recovered-PFP also had reduced pressure pain thresholds at the knee, which were higher than the current-PFP (mean difference: 110-225 kPa; P < 0.05). In conclusion, both current-PFP and recovered-PFP displayed altered pain mechanisms compared to controls with no history of knee pain, despite resolution of symptoms in the recovered-PFP group. The implications of these findings in the recurrent nature of PFP requires further studies.
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Changes in brain function in chronic pain have been studied using paradigms that deliver acute pain-eliciting stimuli or assess the brain at rest. Although motor disability accompanies many chronic pain conditions, few studies have directly assessed brain activity during motor function in individuals with chronic pain. Using chronic jaw pain as a model, we assessed brain activity during a precisely controlled grip force task and during a precisely controlled pain-eliciting stimulus on the forearm. ⋯ Second, although stimulus intensity and pain perception were similar between the groups, functional activity in brain regions including the dorsal lateral prefrontal cortex, rostral ventral premotor cortex, and inferior parietal lobule best separated the groups. Our observations suggest that chronic jaw pain is associated with changes in how the brain processes motor and pain-related information even when the effector producing the force or experiencing the pain-eliciting stimulus is distant from the jaw. We also demonstrate that motor tasks and multivariate analyses offer alternative approaches for studying brain function in chronic jaw pain.
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Changes in activity patterns frequently accompany the experience of chronic pain. Two activity patterns, avoidance and overdoing, are hypothesized to contribute to the development of ongoing pain and pain-related disability, while activity pacing is frequently introduced to enhance pain management and functioning. Two studies were conducted to assess whether reliable subgroups with differing activity patterns could be identified in different pain populations and to evaluate changes in these subgroups after a group format, pain management program. ⋯ Individuals who used high levels of activity pacing and low levels of avoidance consistently reported significantly better functioning relative to all other individuals. Observed changes in activity patterns from pre-treatment to post-treatment suggested that decreasing the association between activity pacing and avoidance was associated with better functioning. These results have implications for both the assessment of activity pacing and for its use as an intervention in the management of ongoing pain.
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Peripheral neuropathy is the major dose-limiting side effect of many currently used chemotherapies, such as vincristine (VCR). We recently demonstrated that candesartan, an angiotensin II type 1 receptor antagonist, was neuroprotective against resiniferatoxin-induced sensory neuropathy, and that this effect is mediated by stimulation of the angiotensin II type 2 receptor (AT2R). Thus, we evaluated the effect of preventive treatment with candesartan and a specific AT2R agonist, C21, on a mouse model of VCR-induced neuropathy. ⋯ Both drugs prevented VCR-induced nonpeptidergic intraepidermal nerve fiber loss. Only C21 displayed neuroprotective effects against VCR-induced loss and enlargement of myelinated nerve fibers in the sciatic nerve. Our finding that candesartan and C21 are protective against VCR-induced neuropathic pain through AT2R stimulation favors evaluation of its therapeutic potential in patients receiving chemotherapy.