An ALE meta-analysis of pain processing alterations in fibromyalgia: Toward an evidence-based process model

It has been hypothesized that core pain-related symptoms of fibromyalgia (FM) might be associated with alterations of pain processing mechanisms. On the one hand, several fMRI studies were conducted to evaluate possible alterations of neural responsiveness toward the presentation of different kinds of noxious stimuli among patients with FM. On the other hand, a quantitative summary of these findings is still lacking. Accordingly, it was conducted an ALE meta-analysis (FWE, p < .05) of studies comparing brain responsiveness to the administration of painful stimuli between patients with FM and healthy controls (HCs). Twenty-one studies were included for meta-analytic procedures. Results showed 3 main findings: i) key areas of the pain matrix (i.e., dorsal anterior cingulate cortex [dACC], basal ganglia and thalamic nuclei) were commonly involved in pain processing in both FM patients and HCs; ii) pain processing in FM patients were characterized by a recruitment of the right insula; whereas, HCs mainly recruited prefrontal areas; iii) patients with FM, compared to HCs, showed an increased magnitude of dACC and supplementary motor area responsiveness toward the presentation of painful stimuli. These findings suggest that altered pain processing in FM is characterized by: i) an increased salience of painful stimuli, which are processed at a viscero-somatic non-mentalized level; ii) high intensity and low granularity of painful experiences accompanied by a negative valence, and modulated through maladaptive avoidance strategies; iii) the development of hypervigilance toward any potential harmful stimuli.