Pain
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Peripheral neuropathic pain is produced by multiple etiological factors that initiate a number of diverse mechanisms operating at different sites and at different times and expressed both within, and across different disease states. Unraveling the mechanisms involved requires laboratory animal models that replicate as far as possible, the different pathophysiological changes present in patients. It is unlikely that a single animal model will include the full range of neuropathic pain mechanisms. ⋯ The mechanical (von Frey and pinprick) sensitivity and thermal (hot and cold) responsiveness is increased in the ipsilateral sural and to a lesser extent saphenous territories, without any change in heat thermal thresholds. Crush injury of the tibial and common peroneal nerves produce similar early changes, which return, however to baseline at 7-9 weeks. The spared nerve injury model may provide, therefore, an additional resource for unraveling the mechanisms responsible for the production of neuropathic pain.
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Mechanical allodynia- and hyperalgesia-like behavior which develops in rats after L5 spinal nerve lesion has been suggested to be due to ectopic activity in the lesioned afferent neurons originating at the lesion site and/or in the dorsal root ganglion because it is eliminated by section of the dorsal root. Here we reevaluated the effect of a dorsal rhizotomy in rats after L5 spinal nerve lesion. Using calibrated von Frey hairs, paw withdrawal threshold to single stimuli and paw withdrawal incidence to repetitive stimulation were tested before and after nerve section. ⋯ These results challenge the widely accepted idea that neuropathic pain behavior developing after spinal nerve lesion is dependent on ectopic activity in the lesioned afferent neurons. However, the present results do not rule out the possibility that after the two nerve lesions the mechanisms generating neuropathic pain behavior are different. After dorsal rhizotomy neuropathic pain behavior may be related to deafferentation whereas after spinal nerve lesion it may be caused by ectopic activity.
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Little is known about the epidemiology of pain in children. We studied the prevalence of pain in Dutch children aged from 0 to 18 years in the open population, and the relationship with age, gender and pain parameters. A random sample of 1300 children aged 0-3 years was taken from the register of population in Rotterdam, The Netherlands. ⋯ The intensity of pain was higher in the case of chronic pain (P<0. 001) and multiple pains (P<0.001), and for chronic pain the intensity was higher for girls (P<0.001). These findings indicate that chronic pain is a common complaint in childhood and adolescence. In particular, the high prevalence of severe chronic pain and multiple pain in girls aged 12 years and over calls for follow-up investigations documenting the various bio-psycho-social factors related to this pain.
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The ultimate objective of our epidemiological research is to complete a longitudinal population-based study to document the prevalence and impact of acute, recurrent, and chronic pain in children and adolescents. As the first phase of our epidemiological research, we developed a comprehensive screening instrument for identifying children with acute, recurrent, and chronic pain, the Pain Experience Interview. We designed this interview to provide information about the lifetime and point prevalence of various pains, and also to provide information about the intensity, affect, duration, and frequency of children's pain. ⋯ These included four predictions about the common response patterns that we would expect to observe for all children based on our understanding of acute pain caused by trauma/disease, and six predictions about the distinct response patterns that we would expect to observe based on the known differences among children in their experiences of headache, acute treatment-related pain, recurrent pain, and chronic pain. All study predictions were confirmed, demonstrating that the Pain Experience Interview is a valid screening instrument for differentiating children with different types of pain problems. The interview can provide estimates for the lifetime and point prevalence of various pains in children, and data on the intensity, affect, duration, and frequency of their pain experiences.
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Clinical Trial
Human chromaffin cell graft into the CSF for cancer pain management: a prospective phase II clinical study.
A number of pre-clinical studies have demonstrated the value of adrenal medullary allografts in the management of chronic pain. The present longitudinal survey studied 15 patients transplanted for intractable cancer pain after failure of systemic opioids due to the persistence of undesirable side-effects. Before inclusion, all the patients had their pain controlled by daily intrathecal (I-Th) morphine administration. ⋯ In most cases, we noted a relationship between analgesic responses and CSF met-enkephalin levels. The results of this phase II open study demonstrate the feasibility and the safety of this approach using chromaffin cell grafts for long-term relief of intractable cancer pain. However, while analgesic efficacy was indicated by the reduction or stabilization in complementary opioid intake, these observations will need to be confirmed in a controlled trial in a larger series of patients.