Age-varying distinct neuroanatomy in young children with autism spectrum disorder and fragile X syndrome.

Researchers used brain scans to study 190 young children - some with fragile X syndrome, some with autism, and some with typical development. They found that children with fragile X syndrome and children with autism have different brain patterns, even though their behaviors can look similar. Children with autism showed faster brain growth in certain areas. This suggests these conditions affect the brain differently and may need different treatment approaches.

This neuroimaging study compared brain structure in 190 young children across three groups: 46 with fragile X syndrome (FXS), 90 with idiopathic autism spectrum disorder (ASD), and 54 typically developing controls. Using structural MRI and age-varying voxel-based morphometry, researchers identified distinct neuroanatomical profiles between FXS and ASD groups. Children with FXS showed increased gray matter volume in subcortical regions (caudate, cerebellar Crus I) but decreased volume in frontal insular regions and cerebellar vermis. Children with ASD demonstrated significantly faster gray matter volume growth rates.

These neuroanatomical differences correlated with behavioral assessments and suggest distinct neurobiological underpinnings despite overlapping clinical symptoms, with important implications for differential diagnosis and targeted interventions.

Findings support distinct neurobiological pathways for FXS and idiopathic ASD despite clinical overlap. This evidence could inform differential diagnostic approaches and suggest that interventions may need to be tailored differently for each condition based on their unique neuroanatomical profiles and developmental trajectories.

Cross-sectional design limits understanding of longitudinal developmental trajectories. Age differences between groups (FXS and ASD cohorts had different mean ages) may confound comparisons. The study does not specify methodological details about behavioral assessments or control for potential confounding variables.

Autism spectrum disorder (ASD) is a commonly associated behavioral diagnosis in individuals with fragile X syndrome (FXS). The present study aimed to identify the neuroanatomical profiles and the age effects on brain's developing trajectories that might be distinct or shared in FXS and idiopathic ASD. A total of 190 children were consecutively recruited including 46 with FXS (5.39 ± 2.68 years), 90 with idiopathic ASD (3.38 ± 1.36 years), and 54 typically developing children (5.40 ± 2.90 years). T1-weighted structural magnetic resonance imaging scans of the brain were acquired, and behavioral assessments were collected from all participants.

Age-varying, voxel-based morphometry (VBM) was conducted to identify neuroanatomical differences between groups. The most pronounced differences in brain morphological patterns were observed in the FXS group. Children with FXS had increased gray matter volume (GMV) in subcortical regions including caudate and Crus I of the cerebellum, but decreased GMV in frontal insular regions and cerebellar vermis lobules VIII/IX compared to the ASD and TD groups. Children with ASD had significantly faster growth rates of GMV.

The identified neuroanatomical profiles correlated with behavior assessments and differed between diagnosis groups. Our findings suggest that FXS and ASD have distinct neuroanatomical signatures during early childhood, particularly in subcortical and cerebellar regions, which are associated with divergent developmental trajectories. Together with their distinct brain-behavior associations, we conclude that these two conditions have distinct neurobiological underpinnings at spatial and temporal scales, despite their overlapping clinical symptoms. These findings have important implications for diagnosis and targeted interventions for children with ASD and FXS.