Increased brain responses during subjectively-matched mechanical pain stimulation in fibromyalgia patients as evidenced by MEG

ObjectiveThe precise pathophysiology of fibromyalgia, a syndrome characterized by chronic widespread pain, remains to be clarified. When subjected to the same amount of stimulation, patients show enhanced brain responses as compared to controls, providing evidence of central pain augmentation in this syndrome. We aimed to characterize brain response differences when stimulation is adjusted to elicit similar subjective levels of pain in both groups.MethodsMagnetoencephalography (MEG) was used to investigate the brain responses to pressure stimulation applied both above and below the pain threshold in nine patients and nine control subjects. A device was developed to deliver pressure pulses in a quantifiable and precise manner. The amount of pressure was adjusted to produce similar subjective pain in both groups.ResultsA between-group comparison of differences between responses evoked by stimulation above and below the pain threshold was performed using cluster-based permutation testing. Increases in signal amplitude in somatosensory, temporal and parietal areas at short latencies, and in prefrontal areas at both short and long latencies, were found to be larger for patients than for control subjects.ConclusionFibromyalgia patients show enhanced brain responses after reducing the amount of pressure to produce similar subjective levels of pain than to the control subjects.SignificanceThe present results suggest that central pain augmentation is present in fibromyalgia, not only when the objective level of stimulation is kept the same as for control subjects, but also when stimulation is adjusted to produce similar levels of pain in patients and controls.

► Fibromyalgia patients showed increased brain responses with respect to controls during subjectively-matched painful mechanical stimulation.
► Increased activity was found in somatosensory, temporal and parietal areas at short latencies and in prefrontal areas at both short and long latencies.
► Therefore, central pain augmentation in fibromyalgia is not only present when patients and controls are subjected to the same level of stimulation but also occurs when stimulation is adjusted to produce similar subjective levels of pain in both groups.