Pain
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Randomized Controlled Trial
Learning potentiates neurophysiological and behavioral placebo analgesic responses.
Expectation and conditioning are supposed to be the two main psychological mechanisms for inducing a placebo response. Here, we further investigate the effects of both expectation, which was induced by verbal suggestion alone, and conditioning at the level of N1 and N2-P2 components of CO2 laser-evoked potentials (LEPs) and subjective pain reports. Forty-four healthy volunteers were pseudorandomly assigned to one of three experimental groups: Group 1 was tested with verbal suggestion alone, Group 2 was tested with a conditioning procedure, whereby the intensity of painful stimulation was reduced surreptitiously, so as to make the volunteers believe that the treatment was effective, Group 3 was a control group that allowed us to rule out phenomena of sensitization and/or habituation. ⋯ Conversely, the N2-P2 amplitude changes that were induced by the conditioning procedure were associated with the subjective perception of pain reduction. Compared to natural history, conditioning produced more robust reductions of LEP amplitudes than verbal suggestions alone. Overall, these findings indicate that prior positive experience plays a key role in maximizing both behavioral and neurophysiological placebo responses, emphasizing that the placebo effect is a learning phenomenon which affects the early central nociceptive processing.
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Multicenter Study
Post-trauma ratings of pre-collision pain and psychological distress predict poor outcome following acute whiplash trauma: a 12-month follow-up study.
Patients with acute whiplash trauma were followed to examine if post-trauma ratings of pre-collision pain and psychological distress were associated with reduced work capability and neck pain at 12 months follow-up. The study included 740 consecutive patients (474 females, 266 males) referred from emergency departments or primary care after car accidents in four counties in Denmark. After the collision patients received a questionnaire on psychological distress, unspecified pain and socio-demographics and 12 months later a follow-up on work capability and neck pain was performed. ⋯ In conclusion unspecified as opposed to specified pain (neck pain) before the collision is associated with poor recovery and high accumulation of pre-collision psychological distress is associated with considerable neck pain at follow-up. However, no conclusions on causality can be drawn. Personal characteristics before the collision are important for recovery and attention to pre-collision characteristics may contribute to the prevention of poor recovery after acute whiplash trauma.
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Randomized Controlled Trial
Stimulation of myofascial trigger points with ultrasound induces segmental antinociceptive effects: a randomized controlled study.
Musculoskeletal pain affects a significant proportion of the general population. The myofascial trigger point is recognized as a key factor in the pathophysiology of musculoskeletal pain. Ultrasound is commonly employed in the treatment and management of soft tissue pain and, in this study, we set out to investigate the segmental antinociceptive effect of ultrasound. ⋯ Following the ultrasound intervention, PPT readings were recorded at 1, 3, 5, 10 and 15 min intervals at both infraspinatus and gluteus medius trigger points; the difference between infraspinatus and gluteus medius PPT values, PPT seg, represents the segmental influence on the PPT. The ultrasound test group demonstrated statistically significant increases in PPT seg (decreased infraspinatus sensitivity) at 1, 3 and 5 min, when compared with PPT seg in the sham ultrasound group. These results establish that low-dose ultrasound evokes short-term segmental antinociceptive effects on trigger points which may have applications in the management of musculoskeletal pain.
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Randomized Controlled Trial
Escitalopram in painful polyneuropathy: a randomized, placebo-controlled, cross-over trial.
Serotonin (5-HT) is involved in pain modulation via descending pathways in the central nervous system. The aim of this study was to test if escitalopram, a selective serotonin reuptake inhibitor (SSRI), would relieve pain in polyneuropathy. The study design was a randomized, double-blind, placebo-controlled cross-over trial. ⋯ Five patients (10.4%) discontinued the study because of adverse effects during escitalopram. This study found a pain-relieving effect of escitalopram in patients with painful polyneuropathy, but a clinically relevant effect was obtained in only few patients. Currently, the drug cannot be recommended as a standard treatment in neuropathic pain.