Altered Neurovascular Coupling in Patients with Chronic Myofascial Pain.

Background Despite previous reports on cerebral structures and functional connectivity in patients with myofascial pain (MFP), it is not clear whether alterations in neurovascular coupling occur in these patients. Objectives We analyzed the coupling between resting-state cerebral blood flow (CBF) and functional connectivity strength (FCS) for observation of neurovascular coupling in patients with chronic MFP. Study design Observational study. Setting University hospital. Methods Resting-state functional magnetic resonance imaging and arterial spin labeling were performed in 23 patients with chronic MFP and 23 healthy controls (HC) for the calculation of FCS and CBF. The whole-brain gray matter CBF-FCS correlations and CBF/FCS ratios of the various voxels of the 2 groups were subsequently compared. Results Compared with the HC, the patients with MFP experienced a decrease in whole-brain gray matter CBF-FCS coupling. In patients with MFP, a decrease in CBF/FCS was found in the bilateral superior temporal gyri, right parahippocampal gyrus, right hippocampus, caudate nucleus, right medial prefrontal cortex, and the periaqueductal gray matter (PAG), whereas an increase in CBF/FCS was found in the bilateral lingual gyri, posterior cingulate cortex, and bilateral inferior parietal lobules. In addition, the CBF/FCS of the PAG in patients with MFP was significantly negatively correlated with the pain visual analog scale score and pain duration. Limitations Alterations in neurovascular coupling in patients with MFP were observed only before treatment. Therefore, there is a lack of data on the alterations that occurred after treatment. Conclusion This study demonstrated for the first time that impairment of neurovascular coupling in the brain may be a potential neuropathological mechanism of chronic MFP.