Pain
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Using cross-sectional data from the United States, England, China, and India, we examined the relationship between education and frequent pain, alongside the modification role of gender in this relationship. We further examined patterns of 3 pain dimensions among participants who reported frequent pain, including pain severity, interference with daily activities, and medication use (these pain dimension questions were not administered in all countries). Our analytical sample included 92,204 participants aged 50 years and above. ⋯ In the United States, these associations were stronger among women. Our findings highlight the prevalent pain among middle-aged and older adults in these 4 countries and emphasize the potentially protective role of higher education on frequent pain, with nuanced gender differences across different settings. This underscores the need for tailored strategies considering educational and gender differences to improve pain management and awareness.
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The concept "nociplastic pain" has been developed for patients with features of nociceptive system sensitization that are not explained as nociceptive or neuropathic. Here, we tested how well the recently published grading system differentiates between chronic primary and secondary pain conditions. We recruited patients with fibromyalgia (FMS, n = 41), complex regional pain syndrome (CRPS, n = 11), osteoarthritis (OA, n = 21), or peripheral nerve injury (PNI, n = 8). ⋯ Based on these data, specificity remained excellent (93%), but sensitivity dropped substantially (60%) due to lacking evidence for pain hypersensitivity in many patients with FMS. This low sensitivity suggests that the published grading system is not suitable for screening purposes. We suggest structural and content modifications to improve sensitivity, including placement of patient history before clinical examination and addition of a high tender point count as evidence for widespread pain hypersensitivity.
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The thalamus plays an important role in sensory and motor information processing by mediating communication between the periphery and the cerebral cortex. Alterations in thalamic development have profound consequences on sensory and motor function. ⋯ Our findings reveal a role for first-order posterior medial thalamic neurons and their projections to layer 4 of the secondary somatosensory cortex in the transmission of nociceptive information. Together, these results establish a connection between a neurodevelopmental lesion in the thalamus and a modality-specific disruption in pain perception.
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The thermal grill illusion (TGI), a phenomenon in which the juxtaposition of innocuous warm and cold temperatures on the skin elicits a burning sensation, offers a unique perspective to how pain occurs in response to harmless stimuli. We investigated the role of the spinal cord in the generation of the TGI across 2 experiments (total n = 80). We applied heat and cold stimuli to dermatomes, areas of skin innervated by a single spinal nerve, that mapped onto adjacent or nonadjacent spinal segments. ⋯ Perceived warmth and burning intensity increased when the cold stimulus projected to the segment more caudal to the warm stimulus, whereas perceived cold during the TGI decreased compared with the opposite spatial arrangement. This suggests that the perception of TGI is enhanced when cold afferents are projected to spinal segments positioned caudally in relation to those receiving warm afferents. Our results indicate distinct interaction of sensory pathways based on the segmental arrangement of afferent fibres and are consistent with current interpretations of the spread and integration of thermosensory information along the spinal cord.