Microstructural White Matter Alterations in Angelman Syndrome: A Fixel-Based Analysis

Angelman syndrome (AS) is a neurodevelopmental disorder resulting from UBE3A gene mutations, characterized by intellectual disability, movement disorders, language difficulties, ataxia, microcephaly, and seizures. While previous studies have examined brain connectivity in AS, the specifics of white matter structural changes have remained unclear. In this study, we utilized advanced diffusion MRI techniques to investigate the microstructural abnormalities of white matter for AS patients. A total of 30 AS patients and 19 age- and sex-matched healthy controls were included in the study. We used metrics derived from both fixel-based analysis (FBA) and diffusion tensor imaging to compare the white matter microstructure differences between AS patients and healthy controls. The results indicate that patients with AS have white matter microstructural differences throughout the whole brain, particularly in the corticospinal tract, arcuate fasciculate, and corpus callosum. FBA-derived metrics demonstrated greater specificity and sensitivity than tensor-based measures. Subsequently, we extracted six fiber tracts with significant differences from the FBA analysis and conducted tract-based statistics, including parieto-occipital pontine, anterior commissure, arcuate fasciculate, corticospinal tract, splenium of corpus callosum, and isthmus of corpus callosum. In all six fiber tracts, we found that AS patients with a higher frequency of seizures exhibited more white matter alterations. Overall, this study provides new insights into the structural differences in AS and their association with clinical symptoms, highlighting the extensive white matter differences and their potential impact on patient outcomes.