Functional connectivity and microstructural changes of the brain in primary Sjögren syndrome: the relationship with depression

Background Fatigue and depression are among the most common manifestations of primary Sjögren syndrome (pSS), but information is lacking on the relationship with brain function and microstructural changes. Purpose To investigate microstructural changes and brain connectivity in pSS, and to evaluate their relationship with fatigue and depression. Material and Methods The study included 29 patients with pSS (mean age 61.2 ± 12.1 years; disease duration 10.5 ± 5.9 years) and 28 controls (mean age 58.4 ± 9.2 years). All the patients completed the Beck’s depression and Fatigue Assessment Scale questionnaires. The imaging protocol consisted of: (i) standard magnetic resonance imaging (MRI) pulse sequences (FLAIR, 3D T1W); (ii) a diffusion tensor imaging pulse sequence; and (iii) a resting state functional MRI pulse sequence. Resting state brain networks and maps of diffusion metrics were calculated and compared between patients and controls. Results Compared with the controls, the patients with pSS and depression showed increased axial, radial, and mean diffusivity and decreased fractional anisotropy; those without depression showed decreased axial diffusivity in major white matter tracts (superior longitudinal fasciculus, inferior longitudinal fasciculus, corticospinal tract, anterior thalamic radiation, inferior fronto-occipital fasciculus, cingulum, uncinate fasciculus, and forceps minor-major). Decreased brain activation in the sensorimotor network was observed in the patients with pSS compared with the controls. No correlation was found between fatigue and structural or functional changes of the brain. Conclusion pSS is associated with functional connectivity abnormalities of the somatosensory cortex and microstructural abnormalities in major white matter tracts, which are more pronounced in depression.