Pain
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Multicenter Study
Quantitative sensory testing in the German Research Network on Neuropathic Pain (DFNS): standardized protocol and reference values.
The nationwide multicenter trials of the German Research Network on Neuropathic Pain (DFNS) aim to characterize the somatosensory phenotype of patients with neuropathic pain. For this purpose, we have implemented a standardized quantitative sensory testing (QST) protocol giving a complete profile for one region within 30 min. To judge plus or minus signs in patients we have now established age- and gender-matched absolute and relative QST reference values from 180 healthy subjects, assessed bilaterally over face, hand and foot. ⋯ Sensitivity is enhanced by side-to-side comparisons by a factor ranging from 1.1 to 2.5. Relative comparisons across body regions do not offer advantages over absolute reference values. Application of this standardized QST protocol in patients and human surrogate models will allow to infer underlying mechanisms from somatosensory phenotypes.
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Imaging studies indicate that experimental pain is processed in multiple cortical areas which are often characterized as a network. However, the functional connectivity within the network and the other properties of the network is poorly understood. Substantial evidence demonstrates that synchronous oscillations between two cortical areas may indicate functional connectivity between those areas. ⋯ Therefore, attention to painful stimuli always enhanced synchrony between cortical pain-related structures. The pattern of this synchrony changed as the patient switched tasks from anticipation of the stimulus to counting the stimulus. These results are the first compelling evidence of pain networks characterized by rapidly switching, task-specific functional connectivity.
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Numerous studies have found evidence for the role of catastrophizing about pain in adjustment to pain in both adults and children. However, the social context influencing pain and pain behaviour has been largely ignored. Especially in understanding the complexities of childhood pain, family processes may be of major importance. ⋯ An oblique three-factor structure emerged to best fit the data in both a sample of parents of schoolchildren (N=205) and in a sample of parents of children with chronic pain (N=107). Moreover, this three-factor structure was found to be invariant across both parent samples. Further, in the clinical sample, parents' catastrophic thinking about their child's pain had a significant contribution in explaining (a) childhood illness-related parenting stress, parental depression and anxiety, and (b) the child's disability and school attendance, beyond the child's pain intensity.
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Accumulating evidence has demonstrated that tumor necrosis factor-alpha (TNF-alpha) plays an important role in neuropathic pain. Recently, it has been shown that Lumbar 5 ventral root transection (L5 VRT) induces persistent mechanical allodynia and thermal hyperalgesia in bilateral hind paws. In the present study, the role of TNF-alpha in the L5 VRT model was investigated. ⋯ Intraperitoneal injection of thalidomide, an inhibitor of TNF-alpha synthesis, started at 2h before surgery, blocked mechanical allodynia and thermal hyperalgesia. However, the drug failed to reverse the abnormal pain behaviors, when it was applied at day 7 after surgery. These data suggest that the upregulation of TNF-alpha and TNFR1 in DRG and spinal dorsal horn is essential for the initiation but not for maintenance of the neuropathic pain induced by L5 VRT.