European journal of pain : EJP
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In the context of neuropathic pain, the contribution of regeneration to the development of positive symptoms is not completely understood. Several efforts have been done to described changes in axotomized neurons, however, there is scarce data on changes occurring in intact neurons, despite experimental evidence of functional changes. To address this issue, we analysed by immunohistochemistry the presence of phosphorylated signal transducer and activator of transcription 3 (pSTAT3), an accepted marker of regeneration, within DRGs where axotomized neurons were retrogradely labelled following peripheral nerve injury. Likewise, we have characterized abnormal electrophysiological properties in intact fibres after partial nerve injury. ⋯ Positive symptoms in patients with peripheral neuropathies correlate to abnormal functioning of different subpopulations of primary afferents. Peripheral nerve damage triggers regenerating programs in the cell bodies of axotomized but also in non-axotomized nociceptors which is in turn, develop abnormal spontaneous and evoked discharges. Therefore, intact nociceptors have a significant role in the development of neuropathic pain due to their hyperexcitable peripheral terminals. Therapeutical targets should focus on inhibiting peripheral hyperexcitability in an attempt to limit peripheral and central sensitization.
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Randomized Controlled Trial
Dependence-like behaviour in patients treated for medication overuse headache: A prospective open-label randomized controlled trial.
Dependence-like behaviour may complicate withdrawal and increase risk of relapse of medication overuse headache (MOH). The most effective treatment for reducing dependence-like behaviour is unknown. ⋯ Withdrawal combined with preventive medication from start is the treatment strategy that reduces dependence-like behaviour the most in MOH patients. Patients initially considered preventive treatment without withdrawal as the most feasible treatment. However, no difference in feasibility between the three arms was found at 6-month follow-up. Withdrawal combined with preventive medication is recommended for treatment of MOH.
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Research among adult and paediatric samples suggests that pain-related injustice appraisals contribute to adverse pain-related functioning. However, a singular focus on pain-related injustice appraisals carries the risk of underestimating the role of broader concepts of justice. This study examined the unique roles of child pain-related injustice appraisals and just-world beliefs in understanding disability and physical, emotional, social and academic functioning, as well as the mediating role of injustice appraisals in the relationship between just-world beliefs and functioning. ⋯ The present study adds to emerging literature on the adverse effects of child pain-related injustice appraisals in the context of pain, through showing that pain-related injustice appraisals are uniquely associated with pain-related functioning and mediate the relationship between just-world beliefs and pain-related functioning. These findings suggest that interventions may target pain-related injustice appraisals as a mechanism for change in children.
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A noxious stimulus following a more intense stimulus often feels less painful than continuous noxious stimulation. This effect, known as offset analgesia (OA), may be due to descending inhibitory control, to changes in peripheral neural transmission or both. The timing and location of noxious thermal stimulation were manipulated to better understand the peripheral and central contributions to OA. ⋯ Offset analgesia (OA) is a fundamentally temporal phenomenon dependent on dynamic changes in stimulus intensity. Here we demonstrate increased OA with increased stimulus duration. This finding implies the more slowly-responding AMH-I peripheral mechanoreceptors contribute to OA. The more rapidly responding AMH-II peripheral mechanoreceptors, however, may be absent or more difficult to activate in the palm where we did not observe OA. This finding implies that the AMH-II receptors are necessary for OA. Our studies suggest methods to unravel the different peripheral and central contributions to OA.
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The rat mid-thoracic contusion model has been used to study at-level tactile allodynia, a common type of pain that develops after spinal cord injury (SCI). An important advantage of this model is that not all animals develop hypersensitivity. Therefore, it can be used to examine mechanisms that are strictly related to the development of pain-like behaviour separately from mechanisms related to the injury itself. However, how to separate animals that develop hypersensitivity from those that do not is unclear. ⋯ However, the amount of spared spinal matter in the cord did not explain the development of hypersensitivity, as previously reported. This approach can be used to study the mechanisms underlying the development of hypersensitivity separately from mechanisms related to injury alone.