Brain structural changes in regions within the salience network in patients with functional constipation.

Functional constipation (FCon) is one of the common functional gastrointestinal disorders (FGID). Previous studies reported alterations in cortical morphometry as well as changes in white matter (WM) fiber tracts and thalamo-limbic/parietal structural connectivity (SC). However, whether patients with FCon are implicated in changes in gray matter (GM) volume and associated SC remains unclear. Voxel-based morphometry (VBM) was first employed to examine differences in GM volume between 48 patients with FCon and 52 healthy controls (HC). Diffusion tensor imaging (DTI) with probabilistic tractography analysis was then employed to explore alterations in SC of these regions. Results showed abdominal symptoms were positively correlated with anxiety (SAS). Two sample t-test showed patients with FCon had decreased GM volumes in the right middle frontal gyrus (MFG_R), left insula (INS_L), and anterior cingulate cortex (ACC, P FWE  < 0.05) which were negatively correlated with abdominal symptoms and difficulty of defecation respectively. Seed-based SC analysis showed patients with FCon had decreased fractional anisotropy of the ACC-right MFG and bilateral INS-MFG tracts. These findings reflect FCon is associated with changes in GM volumes and corresponding SC in brain regions within the salience network.