Imaging Corticospinal Correlates of Aberrant Pain Processing and Modulation in Fibromyalgia Using Combined Brain-Spinal Cord Functional Magnetic Resonance Imaging

Chronic widespread pain represents the cardinal symptom of fibromyalgia (FM). While dysfunctions in cerebral pain-modulatory systems were found to contribute, their link to the spinal cord (SC) is missing. This preliminary study aimed to characterize corticospinal mechanisms of aberrant nociceptive processing and physical activity-related descending pain modulation in FM, by means of combined brain-SC functional magnetic resonance imaging. We scanned 10 females (6 FM, aged 22-62; 4 healthy volunteers (HV), aged 33-62) at 3T (GE SIGNA Premier) using an echo-planar imaging pulse sequence (repetition time=2.5s/echo time=30ms/GRAPPA=2) with 30 brain and 13 cervical SC (centered at C6) slices. The experimental design included four conditions (8x each, 13s), randomized: stimulation ON/OFF paired with motor task ON/OFF. Thermal stimuli were applied at right volar forearm (C6 dermatome) at individualized temperatures (6/10, ATS thermode (Medoc)). The motor task consisted of repetitive isometric right-hand gripping (60% of maximal voluntary contraction, Dynamometer (BIOPAC)). We observed higher activity in pain-processing regions in FM than HV during noxious stimulation. Upon stimulation during motor task, greater activity was found within SC dorsal horns (level C6) and brain regions implicated in sensory pain aspects (e.g., insula, S1) in FM compared to HV, while HV demonstrated enhanced activity in regions implicated in pain regulation (e.g., prefrontal cortex, periaqueductal gray, motor cortices), paralleled by lower pain ratings. We identified neural correlates of aberrant pain modulation in FM which might advance understanding of spinal-supraspinal interactions in chronic pain and pain biomarker development. Funded by National Institutes of Health and Swiss National Science Foundation.