NeuroImage
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The aim of the study was to investigate if an abnormal brain response to pain exists in patients with myofascial pain syndrome (MPS) when stimulated in a hypersensitive myofascial trigger point (MTP). Event-related functional magnetic resonance imaging was used to characterize the brain response to pain evoked from an MTP. Activation patterns from patients were compared with those evoked from an equivalent site in healthy controls with stimulus intensity matched and pain intensity matched stimuli. ⋯ At matched pain intensity, enhanced activity was found in the same somatosensory areas but not in limbic areas. Our results show that the hyperalgesic state observed in MPS patients was associated with abnormal hyperactivity in regions processing stimulus intensity and negative affect. We speculate that suppressed hippocampal activity might reflect stress-related changes in relation to chronic pain as an effective physical and emotional stressor.
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Standardized somatosensory stimulation of the face during functional MRI is technically demanding due to the high magnetic field of the MRI scanner and the confined geometry of the head coil. We developed a new computer-controlled MR-compatible stimulation device for mapping somatosensory-evoked brain activations during fMRI. The device employs von Frey-filaments which are commonly used for quantitative sensory testing (QST) to deliver punctate tactile stimuli to the face and other body surfaces with a high spatiotemporal accuracy. ⋯ In individuals where S1 was significantly activated during both experimental conditions, the punctate tactile stimuli allowed discriminating the face and the hand representation in S1. We conclude that the novel stimulation device appears to be a valuable tool for mapping somatosensory representations. The data suggest that an event-related study design could be beneficial as it better controls for confounding factors such as anticipation, habituation and attention.