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TMS: Using the Theta-Burst Protocol to Explore Mechanism of Plasticity in Individuals with Fragile X Syndrome and Autism
Published on: December 28, 2010
Trajectories of early brain volume development in fragile X syndrome and autism
Heather Cody Hazlett1, Michele D Poe, Amy A Lightbody
1University of North Carolina at Chapel Hill and the Carolina Institute for Developmental Disabilities, NC 27599-2267, USA. heather_cody@med.unc.edu
Insights
Children with fragile X syndrome (FXS) show generalized brain overgrowth compared to controls, with specific regional differences distinguishing them from autism. These brain growth patterns persist from early preschool years into later childhood.
Area of Science:
- Neuroscience
- Developmental Pediatrics
- Genetics
Background:
- Fragile X syndrome (FXS) is a genetic disorder associated with intellectual disability and autism spectrum disorder (ASD).
- Early brain development is critical for understanding neurodevelopmental disorders like FXS and ASD.
- Previous research suggests brain overgrowth in FXS, but detailed longitudinal patterns are less understood, especially in comparison to idiopathic autism.
Purpose of the Study:
- To investigate and compare early brain growth patterns in preschool-aged boys with FXS versus those with idiopathic autism and typically developing controls.
- To identify specific structural brain differences and growth trajectories associated with FXS.
- To differentiate brain development in FXS from that in idiopathic autism using longitudinal MRI data.
Main Methods:
- Longitudinal structural magnetic resonance imaging (MRI) was used to assess brain volumes in 53 boys with FXS, 68 with idiopathic autism, and 50 controls.
- Participants were aged 18-42 months at the first scan and followed up at 4-5 years of age.
- Total brain volumes, lobar tissue volumes, and specific subcortical structures (basal ganglia, hippocampus, amygdala) were analyzed.
Main Results:
- Boys with FXS exhibited generalized brain overgrowth compared to controls, a pattern maintained from age 2 to 5.
- Children with FXS and idiopathic autism did not differ in global brain volume, but displayed distinct regional growth patterns.
- FXS was associated with enlarged temporal lobe white matter, cerebellar gray matter, and caudate nucleus, alongside a smaller amygdala, unlike the generalized cortical enlargement seen in idiopathic autism.
Conclusions:
- Preschoolers with FXS demonstrate generalized brain overgrowth compared to controls, evident early and persisting through age 5.
- Distinct patterns of brain growth differentiate boys with FXS from those with idiopathic autism, highlighting specific neurodevelopmental trajectories.
- These findings underscore the utility of longitudinal MRI in characterizing neurodevelopmental differences in genetic disorders like FXS.
Objective:
To examine patterns of early brain growth in young children with fragile X syndrome (FXS) compared with a comparison group (controls) and a group with idiopathic autism.
Method:
The study included 53 boys 18 to 42 months of age with FXS, 68 boys with idiopathic autism (autism spectrum disorder), and a comparison group of 50 typically developing and developmentally delayed controls. Structural brain volumes were examined using magnetic resonance imaging across two time points, at 2 to 3 and again at 4 to 5 years of age, and total brain volumes and regional (lobar) tissue volumes were examined. In addition, a selected group of subcortical structures implicated in the behavioral features of FXS (e.g., basal ganglia, hippocampus, amygdala) was studied.
Results:
Children with FXS had larger global brain volumes compared with controls but were not different than children with idiopathic autism, and the rate of brain growth from 2 to 5 years of age paralleled that seen in controls. In contrast to children with idiopathic autism who had generalized cortical lobe enlargement, children with FXS showed specific enlargement in the temporal lobe white matter, cerebellar gray matter, and caudate nucleus, but a significantly smaller amygdala.
Conclusions:
This structural longitudinal magnetic resonance imaging study of preschoolers with FXS observed generalized brain overgrowth in children with FXS compared with controls, evident at age 2 and maintained across ages 4 to 5. In addition, different patterns of brain growth that distinguished boys with FXS from boys with idiopathic autism were found.
