Intrinsic brain connectivity in fibromyalgia is associated with chronic pain intensity

Abstract

Objective: Fibromyalgia (FM) is considered to be the prototypical central chronic pain syndrome and is associated with widespread pain that fluctuates spontaneously. Multiple studies have demonstrated altered brain activity in these patients. The objective of this study was to investigate the degree of connectivity between multiple brain networks in patients with FM, as well as how activity in these networks correlates with the level of spontaneous pain.

Methods: Resting-state functional magnetic resonance imaging (FMRI) data from 18 patients with FM and 18 age-matched healthy control subjects were analyzed using dual-regression independent components analysis, which is a data-driven approach for the identification of independent brain networks. Intrinsic, or resting-state, connectivity was evaluated in multiple brain networks: the default mode network (DMN), the executive attention network (EAN), and the medial visual network (MVN), with the MVN serving as a negative control. Spontaneous pain levels were also analyzed for covariance with intrinsic connectivity.

Results: Patients with FM had greater connectivity within the DMN and right EAN (corrected P [P(corr)] < 0.05 versus controls), and greater connectivity between the DMN and the insular cortex, which is a brain region known to process evoked pain. Furthermore, greater intensity of spontaneous pain at the time of the FMRI scan correlated with greater intrinsic connectivity between the insula and both the DMN and right EAN (P(corr) < 0.05).

Conclusion: These findings indicate that resting brain activity within multiple networks is associated with spontaneous clinical pain in patients with FM. These findings may also have broader implications for how subjective experiences such as pain arise from a complex interplay among multiple brain networks.

Figures

Figure 1

ICN Group and Difference Maps. Group maps for HC and FM demonstrate the expected anatomical scope of the canonical DMN, EAN, and MVN for both groups, with the EAN split into a right and left lateralized network. Difference maps contrasting FM versus HC demonstrated that FM patients had greater intrinsic DMN connectivity to several brain regions outside the DMN but known to process evoked pain (insula). FM also demonstrated greater rEAN connectivity within this ICN (iPS). n.b. SII = secondary somatosensory cortex, iPS = intraparietal sulcus.

Figure 2

Covariation between DMN connectivity and age-adjusted spontaneous pain. Greater spontaneous pain intensity correlated with linearly increasing intrinsic DMN connectivity to the right middle and anterior insula.

Figure 3

Covariation between rEAN connectivity and age-adjusted spontaneous pain. Greater spontaneous pain intensity correlated with linearly increasing intrinsic rEAN connectivity to the right anterior insula and left posterior insula.