The journal of pain : official journal of the American Pain Society
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Self-report, the most widely used, gold standard measurement of pain, is crucial for pain research, diagnosis, and management. However, there are no accurate, reliable methods for detecting dishonesty in self-reports when there is incentive for pain deception. We introduce a novel approach to detecting pain deception by analyzing performance patterns of honest and dishonest psychophysical pain testing. Warmth sensation threshold (WST) and heat pain threshold (HPT) were measured in healthy individuals (N = 37) under 2 conditions: standard instruction (ie, provide sincere reports) and instructions to simulate intense pain (i.e., provide feigned reports) with the intention of deceiving. In the feigned compared with sincere condition, participants had significantly increased WST and decreased HPT. Repeatability and variability indices were indistinguishable between conditions. In a second, separate cohort (N = 24), measurements were repeated with the addition of a sensory interference to influence task performance. When sensory interference during HPT measurement was introduced, feigned pain reports had significantly higher variability and poorer repeatability compared with sincere reports and were distinguishable from sincere reports, with high sensitivity (83%) and specificity (84%). The statistical properties of psychophysical performance under sensory interference provide a method for identifying feigned performance and could be applied to evaluations of pain malingering. ⋯ This article introduces a method to detect whether individuals are being dishonest in psychophysical pain testing. The method could help clinicians to detect chronic pain malingering in contexts in which there is incentive to deceive.
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It has been assumed that patients with chronic disorders of consciousness (DOC) do not feel pain, but it is possible that some of them just cannot report it. Modulation of γ-band oscillatory activity (γBO) in centroparietal areas (considered as a marker of either subjective pain perception processes or pain-related motor behavior preparation) by part of the anterior cingulate cortex (ACC) has been proposed to be suggestive of conscious pain perception and could therefore be used to assess the maintenance of some level of conscious pain perception in patients with DOC. Hence, we used a repetitive transcranial magnetic stimulation (rTMS) approach in an attempt to trigger frontoparietal output. We enrolled 10 healthy participants (HC), 10 patients in a minimally conscious state (MCS), and 10 with unresponsive wakefulness syndrome (UWS), who underwent a 1-Hz rTMS protocol over ACC. Before and after the neurostimulation paradigm, we measured the pain-rating assessment (pVAS), γBO, latency, and the amplitude of cortical nociceptive potentials evoked by transcutaneous electric sinusoidal stimuli (EEP). In all the HC and MCS and in 2 of the UWS subjects, rTMS increased γBO and reduced the EEP amplitude, whereas pVAS scoring improved in the HC. Our findings provide some evidence about conscious pain processing even in patients with severe DOC and show that rTMS over ACC may be a useful approach to better investigate the level of conscious impairment. ⋯ Patients with DOC may not be able to respond to pain stimuli, although they may feel it. The possibility of detecting residual pain perceptions by means of a noninvasive neuromodulation paradigm, studying the correlation between the ACC and centroparietal γBO, may help clinicians to better assess pain in such individuals.