Alterations in cortical surface morphometry in fibromyalgia: a multi-parametric study.

Introduction: Fibromyalgia (FM) is a chronic pain disorder with unclear neuroanatomical basis, as previous studies largely relied on volumetric measures insensitive to cortical surface morphology. This multi-parametric surface-based morphometry study examined cortical thickness (CT), fractal dimension (FD), gyrification index (GI), and sulcal depth (SD) in FM. Methods: Thirty-three female FM patients and thirty-three age-matched female healthy controls (HC) underwent T1-weighted MRI. Group differences were assessed using non-parametric permutation testing (TFCE, Results: FM patients showed widespread bidirectional alterations across all four metrics. CT was greater in the right posterior cingulate but lower in the left superior frontal gyrus (SFG), superior parietal lobule (SPL), caudal anterior cingulate (cACC), and right medial orbitofrontal cortex. FD was greater in sensorimotor regions (bilateral postcentral gyri, right precentral gyrus) but lower in visual/temporal areas (bilateral fusiform, left superior temporal gyrus). GI was greater in bilateral SPL and left SFG but lower in the right precuneus and precentral gyrus. SD was lower in bilateral supramarginal gyri and right inferior parietal lobule but greater in the left pars triangularis and right caudal middle frontal gyrus. Clinically, FM patients showed significantly higher depression, anxiety, and alexithymia. After correction, CT in the left cACC remained positively correlated with depression in FM. Discussion: FM is associated with a multifaceted cortical phenotype involving pain processing, emotion regulation, and self-referential cognition regions. These structural alterations, partly correlated with clinical symptoms, provide a robust framework complementing existing functional models of FM.