Pain
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The current International Association for the Study of Pain (IASP) definition of pain as "An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage" was recommended by the Subcommittee on Taxonomy and adopted by the IASP Council in 1979. This definition has become accepted widely by health care professionals and researchers in the pain field and adopted by several professional, governmental, and nongovernmental organizations, including the World Health Organization. In recent years, some in the field have reasoned that advances in our understanding of pain warrant a reevaluation of the definition and have proposed modifications. ⋯ This review provides a synopsis of the critical concepts, the analysis of comments from the IASP membership and public, and the committee's final recommendations for revisions to the definition and notes, which were discussed over a 2-year period. The task force ultimately recommended that the definition of pain be revised to "An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage," and that the accompanying notes be updated to a bulleted list that included the etymology. The revised definition and notes were unanimously accepted by the IASP Council early this year.
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The interaction between osteoarthritis (OA) pain and brain properties remains minimally understood, although anatomical and functional neuroimaging studies suggest that OA, similar to other chronic pain conditions, may impact as well as partly be determined by brain properties. Here, we studied brain gray matter (GM) properties in OA patients scheduled to undergo total joint replacement surgery. We tested the hypothesis that brain regional GM volume is distinct between hip OA (HOA) and knee OA (KOA) patients, relative to healthy controls and moreover, that these properties are related to OA pain. ⋯ The multivariable model in KOA, but not HOA, was related to neuropathic OA pain. These results were mapped into term space (using Neurosynth), providing a meta-analytic summary of brain anatomical distortions in OA. Our results indicate more subtle cortical anatomical differences in OA than previously reported and also emphasize the interaction between OA pain, namely its neuropathic component, and OA brain anatomy.
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Single cell sequencing has provided unprecedented information about the transcriptomic diversity of somatosensory systems. Here, we describe a simple and versatile in situ hybridization (ISH)-based approach for mapping this information back to the tissue. We illustrate the power of this approach by demonstrating that ISH localization with just 8 probes is sufficient to distinguish all major classes of neurons in sections of the trigeminal ganglion. ⋯ Our results demonstrate that the surface of the eye and meninges are targeted by broad arrays of neural classes despite their very different sensory properties but exhibit idiotypic patterns of innervation at a quantitative level. Very surprisingly, itch-related neurons extensively innervated the meninges, indicating that these transcriptomic cell classes are not simply labeled lines for triggering itch. Together, these results substantiate the importance of a sensory neuron's peripheral and central connections as well as its transcriptomic class in determining its role in sensation.