Pain
-
Comparative Study
Micromolar lidocaine selectively blocks propagating ectopic impulses at a distance from their site of origin.
Abnormal impulses caused by very slowly inactivating Na channels of peripheral nerve have been proposed to play a critical role in neuropathic pain. Low concentrations of local anesthetics, often effective in treating experimental and clinical neuropathic pain, are also known to potently suppress the long after-depolarizations induced by these persistently open Na channels. However, these drug actions on impulses that have propagated away from such sites are undetermined. ⋯ Tetrodotoxin also inhibited the induced spontaneous activity, but only at concentrations that also depressed the compound action potential spike. These findings show that low concentrations of lidocaine can restore normal firing patterns in nerve where hyperexcitability has been caused by delayed Na-channel inactivation, without acting directly at the site where ectopic impulses are generated. Thus, it appears that the pattern of abnormal activity rather than an abnormally gating Na channel per se can be a target for lidocaine's therapeutic action.
-
The aim of the present study was to examine the association between pain catastrophizing and general health status in a Dutch adult community sample, including various subgroups of people with musculoskeletal pain in the analyses. For exploratory reasons this study partly replicated previous studies of the factor structure, reliability, and validity of the Pain Catastrophizing Scale (PCS). Results demonstrated that across different pain subgroups, catastrophizing uniquely contributed variance to the prediction of the various aspects of general health status beyond the variance explained by pain intensity, age, gender, and chronicity. ⋯ This implies that a one-factor model might be justifiable as well, at least in the general community. Across various pain subgroups the reliability of the PCS total and subscales was adequate. Additional evidence for the concurrent validity of the PCS was found as well.
-
To obtain parents' identification and description of the behaviors, health care procedures and daily living situations associated with pain in children with cerebral palsy (CP), surveys were sent to parents of children with CP recruited via a clinic case list and a parents' newsletter. Forty-three parents completed the survey. Results indicated that children's ability to communicate pain verbally did not influence whether or not their parent reported observing pain. ⋯ Range of motion manipulation was the therapy most frequently identified as painful by parents (58%), and the one with the highest mean intensity. Parents are able to observe pain in their children with CP regardless of the child's verbal fluency. Knowledge of behaviors and painful situations identified by parents can facilitate management of pain in children with CP.
-
Laser evoked potentials (LEPs) are brain responses to activation of skin nociceptors by laser heat stimuli. LEPs consist of three components: N1, N2, and P2. Previous reports have suggested that in contrast to earlier activities (N1), LEPs responses after 230-250 ms (N2-P2) are modulated by attention to painful laser stimuli. ⋯ Conversely, processes underlying P2 (400 ms) were not affected by spatial attention, but by the probability of the stimulus. This probability effect was not due to P3b-related processes that were observed at a later latency (600 ms). Indeed, P600 could be seen as a P3b evoked by conscious detection of rare targets.
-
A variety of molecules released by inflammatory reactions in the dorsal root and dorsal root ganglion (DRG) may play important roles in the pathology of neuronal abnormalities in lumbar disc herniation. In order to elucidate the pathophysiological mechanisms of painful radiculopathy, secondary to lumbar disc herniation, we evaluated pain-related behavior and the change of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) expression in the DRG and dorsal root using a rat model of lumbar disc herniation. In the nucleus pulposus (NP) group, the left L4/5 nerve roots were exposed after hemilaminectomies and autologous intervertebral discs, which were obtained from coccygeal intervertebral discs, were implanted on each of the exposed nerve roots without mechanical compression. ⋯ We also injected NGF into the endoneurial space of the normal rat spinal nerve root and found that the NGF injection produced dose-dependent mechanical allodynia on the ipsilateral hind paw at 1 day after surgery and an increase in the percentage of BDNF-IR neurons in the DRG at 3 days after surgery compared to the group receiving saline injection. These findings suggest that in the lumbar disc herniation model, i.e. neuritis of the nerve root, increased NGF produced by the inflammatory responses in the dorsal root and DRG tissues may affect the production of BDNF in the DRG and may play important roles in the modulation of the dorsal horn neurons. These changes in neurotrophic factors in the primary afferents may be involved in the pathophysiological mechanisms of neuropathic pain produced by lumbar disc herniation.