Abstract
Fibromyalgia (FM) syndrome is characterized by chronic widespread pain, muscle tenderness and emotional distress. Previous studies found reduced endogenous pain modulation in FM. This deficiency of pain modulation may be related to the attributes of chronic pain and other clinical symptoms experienced in patients with FM. Thus, we tested whether there is a link between the clinical symptoms of FM and functional connectivity (FC) of the periaqueductal gray (PAG), a key node of pain modulation. We acquired resting state 3T functional MRI (rsfMRI) data from 23 female patients with FM and 16 age- and sex- matched healthy controls (HC) and assessed FM symptoms with the Brief Pain Inventory (BPI), Fibromyalgia Impact Questionnaire (FIQ), Hospital Anxiety and Depression Scale (HADS) and Pain Catastrophizing Scale (PCS). We found that patients with FM exhibit statistically significant disruptions in PAG FC, particularly with brain regions implicated in negative affect, self-awareness and saliency. Specifically, we found that, compared to HCs, the FM patients had stronger PAG FC with the lingual gyrus and hippocampus but weaker PAG FC with regions associated with motor/executive functions, the salience (SN) and default mode networks (DMN). The attenuated PAG FC was also negatively correlated with FIQ scores, and positively correlated with the magnification subscale of the PCS. These alterations were correlated with emotional and behavioral symptoms of FM. Our study implicates the PAG as a site of dysfunction contributing to the clinical manifestations and pain in FM.
Highlights
Fibromyalgia (FM) is a chronic pain condition present in 2%–8% of the population with a higher prevalence in women (Clauw, 2014)
We reported that subregions of the periaqueductal gray (PAG) has functional connectivity (FC) with brain regions involved in descending pain modulation, and regions related to executive functions, such as the prefrontal cortex (PFC), striatum and the hippocampus (Coulombe et al, 2016)
We have demonstrated that FC of the PAG is disrupted in patients with FM compared to healthy controls (HC), and that weakened connectivity is related to patients’ individual traits and the clinical manifestations of FM
Summary
Fibromyalgia (FM) is a chronic pain condition present in 2%–8% of the population with a higher prevalence in women (Clauw, 2014). Recent studies of skin biopsies (Levine and Saperstein, 2015), found that patients with small fiber polyneuropathy (SFPN) had reduced small fiber diameters compared to healthy subjects (Doppler et al, 2015), and this in consistent with decreased C fiber nociceptors conduction velocity by Serra et al (2014). Given that objective measures of small fibers does not necessarily correlate with perceived pain in FM, the central nervous system and its neuroplasticity is likely to play some role in FM (Clauw, 2015). A functional MRI (fMRI) study reported brain regions involved in descending pain modulation such as the periaqueductal gray (PAG) have attenuated responses to painful stimuli in FM patients (Jensen et al, 2012)
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