Microstructural alterations of the corpus callosum in affective and non-affective early psychosis: A diffusion magnetic resonance imaging study

Background: Early psychosis (EP) is associated with a disrupted integrity of the white matter microstructure of a variety of brain regions, especially the corpus callosum (CC). In this study, we used diffusion-weighted magnetic resonance imaging data of patients with EP and employed diffusion tensor imaging (DTI), free water-corrected diffusion, and neurite orientation dispersion and density imaging (NODDI) to comprehensively assess the white matter microstructure. Methods: 106 patients with EP (84 non-affective and 22 affective) and 51 healthy controls (HCs) were included from the Human Connectome Project in the Early Psychosis dataset. We used tract-specific analysis for tractography of three parts of the CC and quantified the diffusion measurements for each segment. CC measurement differences between EP vs. HCs and affective vs. non-affective psychosis were assessed by multivariate analysis of covariance. Principal component analysis was used for dimension reduction of diffusion metrics. Results: EP was associated with disrupted white matter integrity in the body of CC indicated by a lower fractional anisotropy and intracellular volume fraction, alongside increased diffusivity measures. None of the CC subregions showed a significant difference in the genu and splenium of the CC between EP and HC groups or between affective and non-affective subgroups. Furthermore, lower white matter integrity in the genu was marginally associated with increased symptom severity. Conclusions: Our findings suggest that microstructural alterations of white matter fibers crossing CC may underlie the pathophysiology of EP. These findings may contribute to a growing body of evidence pointing to white matter disruption as a potential biomarker of disease vulnerability.