Objectives: RB subtypes were investigated in children with ASD and developmental delay (DD) at 3 years. Basal ganglia and thalami volumes were compared in children with ASD, DD and typical development (TD) at 3 years. Longitudinal relationships between RB and volumetric measures were examined from 3 to 6 years.
Methods: Children were assessed at 3 and 6 years for RB with ADI, ADOS and ABC (ASD n=75, DD n=39). A subgroup was also assessed with 3-D T1 MRI (ASD n=45, DD n=14) with an additional MRI-only typical development (TD) group (n=24). Structures assessed include thalami and basal ganglia (striatum, globus pallidus, putamen and caudate).
Results: RB subtypes were identified and were elevated in the ASD group relative to the DD group at age 3. However, self-injurious behavior did not differ between groups. Volumetric findings indicate enlargement of most structures in the ASD relative to the TD group. Enlargement was proportional to overall brain volumes. Comparing the DD to both ASD and TD groups revealed disproportionately smaller volumes in selected structures. There does not appear to be a systematic relationship between levels of RB and volumetric measures at age 3. Developmental changes in RB will be presented in relation to morphometric findings between 3 and 6 years of age.
Conclusions: At age 3, RB was elevated in the ASD relative to the DD group, with the exception of self-injurious behavior. Basal ganglia and thalami were enlarged in the ASD group compared with the TD group and enlargement was in proportion to overall brain volume.