Pain
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Numerous preclinical studies support the role of spinal neuroimmune activation in the pathogenesis of chronic pain, and targeting glia (eg, microglia/astrocyte)- or macrophage-mediated neuroinflammatory responses effectively prevents or reverses the establishment of persistent nocifensive behaviors in laboratory animals. However, thus far, the translation of those findings into novel treatments for clinical use has been hindered by the scarcity of data supporting the role of neuroinflammation in human pain. ⋯ Furthermore, the neuroforaminal translocator protein signal was associated with responses to fluoroscopy-guided epidural steroid injections, supporting its role as an imaging marker of neuroinflammation, and highlighting the clinical significance of these observations. These results implicate immunoactivation at multiple levels of the nervous system as a potentially important and clinically relevant mechanism in human radicular pain, and suggest that therapies targeting immune cell activation may be beneficial for chronic pain patients.
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Chronic pain can be initiated by one or more acute stimulations to sensitize neurons into the primed state. In the primed state, the basal nociceptive thresholds of the animal are normal, but, in response to another hyperalgesic stimulus, the animal develops enhanced and prolonged hyperalgesia. The exact mechanism of how primed state is formed is not completely understood. ⋯ To test whether hyperalgesic priming leads to synaptic plasticity change, we recorded field excitatory postsynaptic potentials from spinal cord slices and found enhanced long-term potentiation in mice that received one acid injection. This long-term potentiation enhancement was prevented by inhibition of extracellular signal-regulated kinase. These findings show that the activation of PKC/ERK signal pathway and downstream protein synthesis is required for hyperalgesic priming and the consolidation of pain singling.
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Randomized Controlled Trial Multicenter Study
Systemic effects of epidural steroid injections for spinal stenosis.
This analysis of the lumbar epidural steroid injections for spinal stenosis multicenter randomized controlled trial data identifies the degree of and risk factors for cortisol suppression after epidural steroid injections in older adults with spinal stenosis. Four hundred patients aged 50 years and older with back or leg pain and central lumbar spinal stenosis completed baseline demographic and psychosocial measures. Morning serum cortisol levels were measured at baseline and 3 weeks after initial injection. ⋯ The effect on 3-week cortisol changes did not differ by demographic or patient-level characteristics. Those treated with methylprednisolone or triamcinolone had an average 3-week cortisol reduction of 41.0% (P = 0.005) and 41.6% (P < 0.001) from baseline, respectively, whereas patients treated with betamethasone or dexamethasone were not significantly different than comparable patients in the lidocaine arm. The higher rates of cortisol suppression at 3 weeks in those receiving epidural corticosteroid injections, particularly with longer-acting insoluble corticosteroid formulations, are consistent with sustained systemic absorption of corticosteroid.