Pain
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Randomized Controlled Trial
Enhanced central pain processing of fibromyalgia patients is maintained by muscle afferent input: a randomized, double-blind, placebo-controlled study.
Fibromyalgia (FM) syndrome is characterized by pain and widespread hyperalgesia to mechanical, thermal, and electrical stimuli. Despite convincing evidence for central sensitization of nociceptive pain pathways, the role of peripheral tissue impulse input in the initiation and maintenance of FM is unclear. Therefore this randomized, double-blind, placebo-controlled trial of 22 female normal controls (NCs) and 28 female FM subjects tested the effects of trapezius muscle (TrapM) tender point injections with 1% lidocaine on local pain thresholds as well as on remote heat hyperalgesia at the forearm. Prior to muscle injections shoulder pain was standardized by tonic mechanical muscle stimulation, resulting in local pain ratings of 4.0+/-0.5 VAS units. Tonic muscle stimulation was interrupted for the TrapM injections but was continued afterwards at the same level. NC as well as FM subjects experienced significant increases of TrapM pressure pain thresholds from lidocaine injections but not from placebo injections (p<0.001). Additionally, heat hyperalgesia of FM participants was significantly reduced at areas remote from the injection site (forearm) by lidocaine but not by placebo (p=0.02). Neither lidocaine nor saline injections significantly affected clinical FM pain ratings, a result most likely due to the very low dose of lidocaine (50mg) used in this trial. ⋯ Lidocaine injections increased local pain thresholds and decreased remote secondary heat hyperalgesia in FM patients, emphasizing the important role of peripheral impulse input in maintaining central sensitization in this chronic pain syndrome; similar to other persistent pain conditions such as irritable bowel syndrome and complex regional pain syndrome.
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Comparative Study
A prospective comparison of post-surgical behavioral pain scales in preschoolers highlighting the risk of false evaluations.
Four behavioral rating scales (BRS) (CHEOPS, CHIPPS, FLACC and OPS) assessing postoperative pain in children aged 1-7 years were studied to compare their psychometric properties, sensitivity and specificity. One hundred and fifty children included in this prospective longitudinal study were videotaped to analyze retrospectively peri-operative behaviors. Pain and anxiety were evaluated by children or by their parents prospectively. ⋯ Moreover, the analysis of sensitivity and specificity using both self-reporting of pain and FASS showed that some children were still under-evaluated. The multivariate analysis underlines silence as a high risk factor of misevaluating postoperative pain. In conclusion, this study highlights the difficulty of discriminating pain intensity from anxiety when using the four BRS and that postoperatively, nearly one child in 10 was misevaluated.
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Randomized Controlled Trial
Activation of the prostaglandin system in response to sleep loss in healthy humans: potential mediator of increased spontaneous pain.
Insufficient duration of sleep is a highly prevalent behavioral pattern in society that has been shown to cause an increase in spontaneous pain and sensitivity to noxious stimuli. Prostaglandins (PGs), in particular PGE2, are key mediators of inflammation and pain, and we investigated whether PGE2 is a potential mediator in sleep-loss-induced changes in nociceptive processing. Twenty-four participants (7 females, age 35.1+/-7.1 years) stayed for 7 days in the Clinical Research Center. ⋯ Urinary PGE2 metabolite significantly increased by about 30% in TSD over sleep condition. TSD-induced increase in spontaneous pain, in particular headache and muscle pain, was significantly correlated with increase in PGE2 metabolite. Activation of the PGE2 system appears to be a potential mediator of increased spontaneous pain in response to insufficient sleep.
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Complex Regional Pain Syndrome (CRPS) is clinically characterized by pain in combination with sensory, autonomic, and motor symptoms that may include weakness, tremor, myoclonus and dystonia of the affected limb(s). The syndrome is multifactorial in origin and mostly attributed to tissue injury. There is some evidence that the human leukocyte antigen (HLA) system plays a role in the pathophysiology of CRPS, but previous studies lacked power. ⋯ HLA-B62 (OR=2.05 [95% CI 1.41-2.99], P=0.0005) and HLA-DQ8 (OR=1.75 [95% CI 1.20-2.57], P=0.005) were found significantly associated with CRPS and dystonia. The association remained significant after correction (HLA-B62 P(corrected) [P(c)] = 0.02 and HLA-DQ8 P(c)=0.04). The involvement of HLA-B62 and HLA-DQ8 in CRPS with dystonia may indicate that these HLA loci are implicated in the susceptibility or expression of the disease.
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Clinical Trial
Functional and structural nerve fiber findings in heterozygote patients with Fabry disease.
Fabry disease is an X-linked inherited lysosomal disorder with dysfunction of the lysosomal enzyme alpha-galactosidase A causing accumulation of glycolipids in multiple organs including the nervous system. Pain and somatosensory disturbances are prominent manifestations of this disease. Until recently disease manifestations in female carriers of Fabry disease have been questioned. ⋯ Sensory nerve action potential amplitude and maximal sensory conduction velocity were not different, whereas there was a highly significant reduction in intraepidermal nerve fiber density. We found no correlation between pain VAS score, quantitative sensory testing and intraepidermal nerve fiber density. Our study demonstrates that careful evaluation of symptoms in female Fabry patients is important as small fiber disease manifestations are present, which in some cases is only detected by skin biopsy.