White matter correlates of autonomic cardiac dysfunction in anorexia nervosa.

Anorexia nervosa (AN) is linked to changes in autonomic function, but the specific neuroanatomical substrates of these changes are not well understood. In this study, we used diffusion-weighted imaging to examine white matter structure in the ventromedial prefrontal cortex-dorsal vagal complex (vmPFC-DVC) pathway, which is essential for autonomic regulation. Compared to healthy controls, individuals with AN showed significantly higher fractional anisotropy and axial diffusivity, as well as more streamlines connecting the vmPFC and DVC-indicating altered structural organization. However, radial diffusivity, which relates to myelin integrity, did not differ between groups, suggesting that changes are not due to higher myelination in AN individuals. Region-specific analysis located the differences in white matter metrics to the region of fiber decussation at the ponto-midbrain junction. Fractional anisotropy and radial diffusivity of vmPFC-DVC were associated with autonomic function in healthy controls but not in individuals with AN, pointing to a disruption in brain-body communication in AN. No differences were found in tensor metrics in other white matter tracts in the brainstem, indicating these alterations are specific to autonomic pathways rather than reflecting widespread brainstem abnormalities. This study provides the first evidence of structural disruptions in a key autonomic circuit in AN and highlights a potential decoupling between white matter integrity and autonomic regulation.