Pain
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Multicenter Study
CACNG2 polymorphisms associate with chronic pain following mastectomy.
Chronic postmastectomy pain (PMP) imposes a major burden on the quality of life of the ever-increasing number of long-term survivors of breast cancer. An earlier report by Nissenbaum et al. claimed that particular polymorphisms in the gene CACNG2 are associated with the risk of developing chronic PMP after breast surgery (Nissenbaum J, Devor M, Seltzer Z, Gebauer M, Michaelis M, Tal M, Dorfman R, Abitbul-Yarkoni M, Lu Y, Elahipanah T, delCanho S, Minert A, Fried K, Persson AK, Shpigler H, Shabo E, Yakir B, Pisante A, Darvasi A. Susceptibility to chronic pain following nerve injury is genetically affected by CACNG2. ⋯ We found that the biomarker is selective because it did not predict pain after laparoscopic hernia repair and was not associated with pain sensitivity to experimentally applied noxious thermal stimuli. We conclude that the A-C-C haplotype at the 3 single-nucleotide polymorphisms (rs4820242, rs2284015, and rs2284017) in the CACNG2 gene is associated with increased risk of developing PMP. This information may advance current knowledge on pathophysiology of PMP and serve as a step forward in the prediction of clinical outcomes and personalized pain management.
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We aimed to investigate the pattern and utilization of neuropathic pain medications in peripheral neuropathy patients. Using a privately insured, health care claims database from 2001 to 2014, we identified a retrospective cohort of incident peripheral neuropathy patients (validated ICD-9 definition) after excluding other chronic pain conditions. Outcome measures included opioid prescriptions, chronic opioid therapy (greater than or equal to 90 days of continuous supply), guideline-recommended medications for painful peripheral neuropathy (serotonin reuptake inhibitors, tricyclic antidepressants, and gabapentinoids), and pain specialists (neurologists, physiatrists, and anesthesiologists). ⋯ Pain specialists were associated with high opioid utilization and high guideline-recommended medication utilization. In conclusion, opioid initiation and transition to chronic opioid therapy are frequent in a peripheral neuropathy population despite few patients receiving more than one guideline-recommended medication. Efforts to decrease opioid utilization and increase guideline-recommended medication use are needed to improve current neuropathic pain treatment.
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Multicenter Study
Obesity increases the risk of chronic pain development following motor vehicle collision.
Obesity has been found to increase the risk of musculoskeletal pain (MSP) in other settings, but to our knowledge, the influence of increased body mass index on pain outcomes after common trauma exposures such as motor vehicle collision (MVC) has not been assessed. In addition, obesity results in biomechanical changes, as well as physiologic changes including reduced hypothalamic pituitary adrenal axis negative feedback inhibition, but mechanisms by which obesity may result in worse post-traumatic outcomes remain poorly understood. ⋯ After adjusting for an array of sociodemographic factors, obesity (particularly morbid obesity) was an independent risk factor for worse MSP after MVC (eg, RR 1.41 [95% CI 1.11, 1.80] for moderate or severe MSP 6 months after MVC among morbidly obese vs normal weight MVC survivors). Interestingly, substantial effect modification was observed between obesity risk and a genetic variant known to reduce hypothalamic pituitary adrenal axis negative feedback inhibition (FKBP5 rs9380526). (eg, 41% vs 16% increased risk of moderate or severe MSP at 6 months among obese individuals with and without the risk allele.) Further studies are needed to elucidate mechanisms underlying chronic pain development in obese trauma survivors and to develop interventions that will reduce chronic pain severity among this common, at-risk group.
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Randomized Controlled Trial
The association between endogenous opioid function and morphine responsiveness: a moderating role for endocannabinoids.
We sought to replicate previous findings that low endogenous opioid (EO) function predicts greater morphine analgesia and extended these findings by examining whether circulating endocannabinoids and related lipids moderate EO-related predictive effects. Individuals with chronic low-back pain (n = 46) provided blood samples for endocannabinoid analyses, then underwent separate identical laboratory sessions under 3 drug conditions: saline placebo, intravenous (i.v.) naloxone (opioid antagonist; 12-mg total), and i.v. morphine (0.09-mg/kg total). During each session, participants rated low-back pain intensity, evoked heat pain intensity, and nonpain subjective effects 4 times in sequence after incremental drug dosing. ⋯ In the absence of significant interactions, lower EO function predicted significantly greater morphine analgesia (as in past work) and euphoria. Results indicate that EO effects on analgesic and subjective responses to opioid medications are greatest when endocannabinoid levels are low. These findings may help guide development of mechanism-based predictors for personalized pain medicine algorithms.
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To develop a machine learning model to investigate the discriminative power of whole-brain gray-matter (GM) images derived from primary dysmenorrhea (PDM) women and healthy controls (HCs) during the pain-free phase and further evaluate the predictive ability of contributing features in predicting the variance in menstrual pain intensity. Sixty patients with PDM and 54 matched female HCs were recruited from the local university. All participants underwent the head and pelvic magnetic resonance imaging scans to calculate GM volume and myometrium-apparent diffusion coefficient (ADC) during their periovulatory phase. ⋯ In the regression analysis, demographical indicators and myometrium ADC accounted for a total of 29.37% of the variance in pain intensity. After regressing out these factors, GM features explained 60.33% of the remaining variance. Our results suggested that GM volume can be used to discriminate patients with PDM and HCs during the pain-free phase, and neuroimaging features can further predict the variance in the intensity of menstrual pain, which may provide a potential imaging marker for the assessment of menstrual pain intervention.