Altered fMRI responses to non-painful sensory stimulation in fibromyalgia patients
Citation: Lopez-Sola M., Pujol J., Wager T.D., Garcia-Fontanals A., Blanco-Hinojo L., Garcia-Blanco S., Poca-Dias V., Harrison B.J., Contreras-Rodriguez O., Monfort J., Garcia-Fructuoso F., Deus J. Altered fMRI responses to non-painful sensory stimulation in fibromyalgia patients. Arthritis Rheumatol. 2014 Jun 20. (accepted for publication). [Epub ahead of print]
Objective: Fibromyalgia (FM) is a disorder characterized by chronic pain and enhanced responses to acute noxious events. However, the sensory systems affected in FM may extend beyond pain itself, as FM patients show reduced tolerance to non-nociceptive sensory stimulation. Characterizing the neural substrates of multisensory hypersensitivity in fibromyalgia may thus provide important clues about the underlying pathophysiology of the disorder. The aim of this study was to characterize brain responses to non-nociceptive sensory stimulation in FM patients and its relationship to subjective sensory sensitivity and clinical pain severity. Methods: Functional magnetic resonance imaging (fMRI) was used to assess brain response to auditory, visual and tactile-motor stimulation in 35 women with FM and 25 matched controls. Correlation and mediation analyses were performed to establish the relationship between brain responses and three types of outcomes: subjective hyper-sensitivity to daily sensory stimulation, spontaneous pain, and functional disability.
Results: Patients reported increased subjective sensitivity (increased unpleasantness) in response to multisensory stimulation in daily life. FMRI revealed that patients showed reduced task-evoked activation in primary/secondary visual and auditory areas and augmented responses in the insula and anterior lingual gyrus. Reduced responses in visual and auditory areas were correlated with subjective sensory hyper-sensitivity and clinical severity measures. Conclusion: FM patients showed strong attenuation of brain responses to non-painful events in early sensory cortices, accompanied by an amplified response at later stages of sensory integration in the insula. These abnormalities are associated with core fibromyalgia symptoms, suggesting that they may be part of the pathophysiology of the disease.