This functional magnetic resonance imaging study addressed similarities and differences in behavioral and neural responses to experimental visceral compared with somatic pain stimuli and explored the ...contribution of fear of pain to differences between pain modalities. In N = 22 healthy women, we assessed blood oxygen level-dependent responses to rectal distensions and cutaneous heat stimuli matched for perceived pain intensity. Fear of pain and pain unpleasantness were assessed before and after scanning. Visceral pain was more fear evoking and more unpleasant, and trial-by-trial intensity ratings failed to habituate across trials (all interactions modality × time: P < 0.01). Differences in fear of pain and pain intensity independently contributed to greater visceral pain unpleasantness (combined regression model: R(2) = 0.59). We observed joint neural activations in somatosensory cortex and frontoparietal attention network (conjunction analysis: all pFWE <0.05), but distensions induced greater activation in somatosensory cortex, dorsal and ventral anterior insula, dorsal anterior and midcingulate cortices, and brainstem, whereas cutaneous heat pain led to enhanced activation in posterior insula and hippocampus (all pFWE <0.05). Fear of visceral pain correlated with prefrontal activation, but did not consistently contribute to neural differences between modalities. These findings in healthy women support marked differences between phasic pain induced by rectal distensions vs cutaneous heat, likely reflecting the higher salience of visceral pain. More studies with clinically relevant pain models are needed to discern the role of fear in normal interindividual differences in the response to different types of pain and as a putative risk factor in the transition from acute to chronic pain.
Pain after surgery remains a major health problem, calling for optimized treatment regimens to maximize the efficacy of pharmacological interventions. In this randomized controlled trial, we tested ...in a routine surgical treatment setting whether postoperative pain can be reduced by a brief preoperative intervention, ie, positive verbal suggestions in combination with sham acupuncture, designed to optimize treatment expectations. We hypothesized that the expectancy intervention as add-on to patient-controlled intravenous analgesia with morphine reduces patient-reported postoperative pain and improves satisfaction with analgesia. Ninety-six women undergoing breast cancer surgery were randomized at 2 stages: Before surgery, anesthesiologists delivered either positive or neutral verbal suggestions regarding the benefits of acupuncture needling on postoperative pain ("information condition"). Patients were then randomized to receive sham acupuncture or no sham acupuncture during postoperative care ("sham acupuncture condition"). Average pain during the 24-hour observation period after surgery as primary and satisfaction with analgesia as secondary outcome was assessed with standardized measures and analyzed with analysis of covariance accounting for morphine dose, surgery-related, and psychological parameters. Postoperative pain ratings were significantly reduced in patients who received positive treatment-related suggestions (F = 4.45, P = 0.038, main effect of information). Moreover, patients who received an intervention aimed at optimized treatment expectations reported significantly greater satisfaction with analgesia (F = 4.89, P = 0.030, interaction effect). Together, our proof-of-concept data support that optimizing treatment expectations through verbal suggestions may offer a promising approach to improve patient-reported outcomes. Future translational and clinical studies are needed to test such psychological strategies in different surgical interventions, patient groups, and pharmacological treatment regimens.
