Pain
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Patients with fibromyalgia syndrome (FMS) report chronic pain related to abnormal sensitivity of muscles that is reflected by so-called tender points (TP). TP represent areas of abnormal mechanical pain thresholds that have only shown a minor correlation with clinical pain of FMS patients and seem to be better suited for predicting distress. Pain-related negative affect (PRNA), abnormal temporal summation of second pain (termed wind-up or WU), and abnormal WU decay are frequently present in FMS patients. ⋯ Hierarchical regression analysis demonstrated that the combination of PRNA ratings, TP count, and WU decay ratings predicted 49.7% of the variance of clinical pain in FMS. This model demonstrates independent relationships of biological and psychological factors to clinical pain and underscores the important role of abnormal peripheral and central pain mechanisms for FMS. Therefore, the combination of PRNA, TP count, and WU decay may provide an excellent measure for future clinical studies of FMS patients.
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Comparative Study
Body motion during repetitive isodynamic lifting: a comparative study of normal subjects and low-back pain patients.
To quantify performance differences between patients with low-back pain (LBP) and a control group during their performance of a repetitive isodynamic lifting task. Case-control study was done. LBP patients were recruited and tested at an outpatient ambulatory chronic pain rehabilitation program before treatment was begun. ⋯ Patients and controls also differed significantly on dynamic measures, particularly lifting speed and hip and knee temporal midpoints. Major static and dynamic motion differences were found between LBP patients and controls as they performed repetitive lifting under a constant load. These findings indicate that body motion parameters, in addition to more common strength and endurance measures, are necessary to describe the impact of persistent LBP on a person's lifting abilities.
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Reduced habituation to experimental pain in migraine patients: a CO(2) laser evoked potential study.
The habituation to sensory stimuli of different modalities is reduced in migraine patients. However, the habituation to pain has never been evaluated. Our aim was to assess the nociceptive pathway function and the habituation to experimental pain in patients with migraine. ⋯ Moreover, while the N1-P1 amplitude showed a significant habituation in CS after hand stimulation, it did not change across repetitions in MO patients. In conclusion, no functional impairment of the nociceptive pathways, including the trigeminal pathways, was found in either MO or CTTH patients. But patients with migraine had a reduced habituation, which probably reflects an abnormal excitability of the cortical areas involved in pain processing.
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The inhibitory activity of gamma-aminobutyric acid (GABA) is considered critical in setting the conditions for synaptic plasticity, and many studies support an important role of GABA in the suppression of nociceptive transmission in the dorsal horn. Consequently, any injury-induced modification of the GABA action has the potential to critically modify spinal synaptic plasticity. We have previously reported that chronic constriction injury of the sciatic nerve was accompanied by long-lasting potentiation of superficial spinal dorsal horn field potentials following high-frequency tetanus. ⋯ In separate but related Western immunoblot experiments, we also established that the chronic constriction injury was accompanied by significant decreases in the content of the GABA transporter GAT-1. These data demonstrated that GABA-A receptor agonists may effectively influence the expression of long-lasting synaptic plasticity in the spinal dorsal horn, and that an injury-induced loss in GABA transporter content may have contributed to a depletion of GABA from its terminals within the spinal dorsal horn. These data lent further support to the notion that the loss of GABA inhibition may have important consequences for the development of neuropathic pain.
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Fear of movement/(re)injury and its associated avoidance behavior have shown to be strongly associated with functional disability in chronic low back pain. In acute low back pain disability, the role of pain-related fear has received little research attention so far. Measures of pain-related fear such as the Tampa Scale for Kinesiophobia (TSK) are increasingly being used in primary care. ⋯ Additionally, and in contrast to what is often observed in chronic pain, disability, and to a lesser degree participation, were also associated with pain intensity. Finally, the association between pain-related fear, pain intensity and participation was indeed mediated by disability. The results suggest that early on in the development of LBP disability, the successful reduction of pain-related fear and disability might foster increased participation in daily and social life activities.