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The International Association for the Study of Pain has released a new classification scheme for chronic pain. This classification scheme describes chronic pain as either a symptom of a disease (chronic secondary pain) or as the disease itself (chronic primary pain). Chronic temporomandibular disorders have many similarities to other proposed chronic overlapping pain disorders, but are classified and managed by dental practitioners as a localized pain condition of the orofacial region. We review the literature to describe the similarities between chronic temporomandibular disorders and chronic overlapping pain disorders, and discuss how this evolving concept may affect the way that dentists approach the diagnosis and management of chronic temporomandibular disorders.
The present study explores the benefits of an 8-week mindfulness-based stress reduction (MBSR) program to white matter integrity among breast cancer survivors experiencing chronic neuropathic pain (CNP).
Gabapentinoid drugs (gabapentin and pregabalin) are effective in neuropathic pain, which has a prevalence of ∼7%. Concerns about increased prescribing have implications for patient safety, misuse, and diversion. Drug-related deaths (DRDs) have increased and toxicology often implicates gabapentinoids. We studied national and regional prescribing rates (2006-2016) and identified associated sociodemographic factors, co-prescriptions and mortality, including DRDs.
Luminal distention and abdominal pain are major clinical hallmarks of obstructive bowel disorders and functional bowel disorders linked to gut dysbiosis. Our recent studies found that chronic lumen distention increased visceral sensitivity and decreased abundance of gut commensal Lactobacillus reuteri in a rodent model of partial colon obstruction (OB). To establish causation, we performed precision microbial therapy to assess whether recolonization of L. reuteri prevents visceral hypersensitivity in lumen distention, and if so, to identify the gut-microbiota mechanism. Lumen distention was induced in Sprague-Dawley rats by implanting an obstruction band in the distal colon for up to 7 days. L. reuteri strains or vehicle were gavage ingested 1X10 CFU/g daily starting 2 days prior to obstruction. L. reuteri rat strains that were able to recolonize obstructed colon significantly improved food intake and body weight in OB rats, and attenuated referred visceral hyperalgesia measured by the withdrawal response to von Frey filament applications to the abdomen. Mechanistically, L. reuteri treatment attenuated hyper-excitability of the dorsal root ganglia neurons projecting to the distended colon by promoting opioid receptor function in affected tissues. The expression of µ, δ, and κ opioid receptors was significantly downregulated in colonic muscularis externae and sensory neurons in OB rats. However, L. reuteri treatment prevented the loss of opioid receptors. Further, administration of peripheral opioid receptor antagonist naloxone methiodide abolished the analgesic effect of L. reuteri in OB. In conclusion, precision L. reuteri therapy prevents lumen distention-associated visceral hypersensitivity by local bacterial induction of opioid receptors.
Acute pain that persists for a few days is associated with a reduction in patients' quality of life. Orofacial persistent pain promotes psychological disorders such as anxiety, impairs daily essential activities such as eating, and results in decreased social interaction. Here, we investigated whether rats subjected to orofacial formalin injection or intraoral incision surgery display persistent facial heat hyperalgesia, ongoing pain, anxiety-like behavior and changes in ultrasonic vocalization. Orofacial formalin injection or intraoral incision caused facial heat hyperalgesia for 3 days compared to saline-injected and sham animals. Additionally, both experimental groups showed a reduction in the number of entries and in the time spent in the open arms in the elevated plus maze test on day 3, suggesting that anxiety-like behavior developed as a consequence of persistent pain. At this time point, both groups also displayed a reduction in the number of 50-kHz calls, specifically in the flat subtype, which suggests a decrease in social communication. Moreover, on day 3 after surgery, systemic morphine produced robust conditioned place preference in rats subjected to intraoral incision compared to sham, and the former group also presented increased spontaneous facial grooming, revealing the presence of ongoing pain. Finally, western blot and immunohistochemistry analysis showed a reduction in tyrosine hydroxylase expression in the nucleus accumbens (NAc), which may reflect a decrease in mesolimbic dopaminergic activity. Altogether, the results demonstrate that acute orofacial pain causes prolonged changes in behavioral and affective pain components, which may be related to dopaminergic changes in the NAc.
Aerobic exercise is believed to be an effective chronic low back pain (CLBP) intervention, although its mechanisms remain largely untested. This study evaluated whether endogenous opioid (EO) mechanisms contributed to the analgesic effects of an aerobic exercise intervention for CLBP. Individuals with CLBP were randomized to a 6-week, 18-session aerobic exercise intervention (n = 38) or usual activity control (n = 44). Before and after the intervention, participants underwent separate laboratory sessions to assess responses to evoked heat pain after receiving saline placebo or i.v. naloxone (opioid antagonist) in double-blinded, crossover fashion. Chronic pain intensity and interference were assessed before and after the intervention. EO analgesia was indexed by naloxone-placebo condition differences in evoked pain responses (blockade effects). Relative to controls, exercise participants reported significantly greater pre-post intervention decreases in chronic pain intensity and interference (p's < .04) and larger reductions in placebo condition evoked pain responsiveness (McGill Pain Questionnaire-Short Form [MPQ]-Total). At the group level, EO analgesia (MPQ-Total blockade effects) increased significantly pre-post intervention only among female exercisers (p = .03). Dose-response effects were suggested by a significant positive association in the exercise group between exercise intensity (based on meeting heart rate targets) and EO increases (MPQ-Present Pain Intensity; p = .04). Enhanced EO analgesia (MPQ-Total) was associated with significantly greater improvement in average chronic pain intensity (p = .009). Aerobic exercise training in the absence of other interventions appears effective for CLBP management. Aerobic exercise-related enhancements in endogenous pain inhibition, in part EO-related, likely contribute to these benefits.
Migraine is a complex and disabling neurological disorder, and the exact neurological mechanisms remain unclear. Thalamus is considered the hub of the central processing and integration of nociceptive information, as well as the modulation of these processes.
While dipyrone is a widely used analgesic, its mechanism of action is not completely understood. Recently we have reported that the dipyrone metabolite 4-aminoantipirine (4-AA) reduces prostaglandin E (PGE )-induced pain-related behaviour through the cannabinoid type 1 (CB1) receptor. Here, we ascertained, in naive and PGE -induced "inflamed" conditions, both in vivo and in vitro, the molecular mechanisms involved in the 4-AA-induced analgesic effects.
The COVID-19 health emergency has led many Headache providers to transition to virtual care overnight without preparation. We review our experience and discuss tips to bring humanity to the virtual visits.
Nonsteroidal anti-inflammatory drugs (NSAIDs) are, in general, the cornerstone of musculoskeletal pain management; however, systemic adverse events with oral formulations of NSAIDs are common. To address this problem and limit systemic exposure, topical formulations of some NSAIDs have been developed. The aim of this systematic review was to assess the available evidence on the efficacy and safety of the topical formulations of the NSAID etofenamate in patients with musculoskeletal disorders.