Multimodal MRI reveals structural and functional alterations in thyroid-associated ophthalmopathy

This study aimed to investigate white matter microstructural damage, spontaneous brain activity, and functional connectivity alterations in patients with thyroid-associated ophthalmopathy (TAO) and visual impairment using multimodal MRI.

Forty-five TAO patients with visual impairment and 32 healthy controls (HCs) underwent diffusion kurtosis imaging (DKI) and resting-state functional MRI (rs-fMRI). Microstructural changes along the visual pathway were quantified using fractional anisotropy (FA), mean kurtosis (MK), and mean diffusivity (MD). Regional spontaneous activity was assessed using the amplitude of low-frequency fluctuation (ALFF) and fractional ALFF (fALFF), and seed-based functional connectivity (FC) analyses were employed. Group differences were examinded using two-sample t-tests with false discovery rate (FDR) correction (p < 0.05). Correlations between imaging parameters and clinical indicators were further analyzed.

Compared with HCs, the TAO group showed significantly decreased MK, FA, and MD values in the optic radiation, lateral geniculate body, optic tract, and optic nerve, with MK being the most markedly reduced one. Patients also exhibited increased ALFF in the right parahippocampal gyrus and decreased ALFF in the left calcarine fissure, as well as decreased fALFF in the left calcarine fissure and postcentral gyrus. Further analyses revealed decreased FC between the left calcarine fissure and the right lingual gyrus/middle frontal gyrus/bilateral postcentral gyri, and increased FC with the left supplementary motor area/fusiform gyrus. ALFF/fALFF in visual network-related regions correlated with proptosis and extraocular muscle thickening in TAO patients.

TAO is associated with white matter microstructural damage, aberrant spontaneous neural activity, and functional reorganization. The combination of DKI and rs-fMRI (ALFF/fALFF, FC) may provide comprehensively insights into central neuropathological mechanisms, providing a basis for early diagnosis and targeted intervention.