Cortical morphometric alterations and disrupted structural covariance networks in Somatic Symptom Disorder

Previous studies have reported alterations in gray matter volume (GMV) in patients with Somatic Symptom Disorder (SSD), but the specific characteristics of cortical morphology and brain network organization remain poorly understood. This study aims to investigate cortical structural changes, focusing on cortical thickness (CT) and surface area (SA), and further explore potential disruptions in the structural covariance networks (SCNs) in individuals with SSD.

High-resolution T1-weighted MRI data were acquired from 50 patients with SSD and 60 healthy controls (HCs), to assess group differences in CT and SA using FreeSurfer. Partial correlation analyses were conducted to explore associations between cortical metrics and clinical variables. SCNs were constructed based on regional morphometric features, and graph theoretical analysis was employed to evaluate network topology.

Compared to HCs, SSD patients showed reduced CT in the left superior frontal gyrus (SFG), left pars triangularis gyrus (PTG), and bilateral rostral middle frontal gyrus (rMFG). Notably, CT in the right rMFG was negatively associated with somatic symptom severity. Graph theoretical analysis of the CT-based SCN revealed increased nodal degree in the right inferior temporal gyrus, along with higher small-worldness index (σ), normalized clustering coefficient (γ), and local efficiency in the right hemisphere. In the SA-based SCN, decreased nodal efficiency was observed in the left middle occipital sulcus and lunate sulcus.

These findings highlight both cortical structural alterations and disrupted SCN organization in SSD. Such abnormalities may serve as potential neuroimaging markers for understanding the neurobiological mechanisms underlying SSD.