Cold Water Pressor Test Differentially Modulates Functional Network Connectivity in Fibromyalgia Patients Compared with Healthy Controls.

Fibromyalgia is a multifaceted chronic pain condition of unknown etiology. Conditioned pain modulation (CPM) such as cold water pressor test of the foot, is widely documented as being disrupted in patients with fibromyalgia. To date, the mechanisms underlying such dysregulation of the descending control of pain in fibromyalgia remain poorly understood. In this study, we used ICA-based network analysis to comprehensively compare differences in functional network connectivity among relevant (nonartifactual) intrinsic connectivity brain networks during the resting state before and after cold pressor test in patients with fibromyalgia and healthy controls. The results revealed significant differences in functional connectivity between the two groups that included the networks that integrate cognitive control and attention systems with memory, emotion and brainstem regions. Specifically, functional connectivity involving central executive network was absent in patients with fibromyalgia compared with controls. Patients showed significant functional connectivity changes involving subcortical and brainstem networks with the sensorimotor and dorsal attention networks. Accordingly, aberrant CPM in patients with fibromyalgia may be due to the differences in functional connectivity involving the subcortical/brainstem regions, and is facilitated by the recruitment of the dorsal attention network in lieu of the central executive network. Future research replicating the present findings with larger sample size can shed more light on neurobiology of endogenous pain modulation in fibromyalgia.