Longitudinal Study of Repetitive Behavior and Volumes of the Caudate and Thalamus in Children with Autism Spectrum Disorder Between 3 and 9 Years of Age

Background: Abnormalities of the caudate and thalami may contribute to symptom expression in autism spectrum disorders (ASD). Cross-sectional studies of older children and adults with ASD report an association between volumetric alterations of these structures and higher levels of repetitive behavior (RB). We are not aware of previous studies investigating developmental changes in young children in terms of caudate and thalami volumes and level of RB.

Objectives: We investigated changes in RB from 3 to 9 years of age in children with ASD. Caudate and thalami volumes were compared in children with ASD, developmental delay (DD) and typical development (TD) at 3, 6 and 9 years. Longitudinal relationships between RB and volumetric measures were examined from 3 to 9 years of age among children with ASD.

Methods: Children were assessed at 3, 6, and 9 years for RB with subscales from the ADI, ADOS and ABC (ASD n=75). A subgroup was also assessed with 3-D MRI (ASD n=45 at age 3) with additional MRI data for DD (n=14 at age 3) and TD groups (n=25 at age 3). Structures assessed include the caudate and thalami as well as total cerebral volume (TCV).

Results: Severity of RB increased between 3 and 9 years of age among children with ASD.  This trend persisted after adjusting for differences in cognitive ability. Mean caudate volumes were larger in the ASD group at ages 3, 6 and 9 compared to the TD group.  Differences were not significant after scaling for TCV. Thalami volumes did not differ between the ASD and TD groups.  The ASD group had larger thalami and caudate compared to the DD group at age 3, 6, and 9. After scaling for TCV, these differences were significant at age 3 for the thalami and age 3 and 6 for the caudate.  We will present results on the association between RB and volumetric measures at age 3, 6, and 9.

Conclusions: RB level increased in children with ASD between the ages of 3 and 9. Volumetric measures did not differ between the ASD and TD group after scaling for TCV.  Thalami and caudate volumes were decreased in the DD group. Developmental changes in the thalami and caudate will be presented as will potential relations between RB and thalami and caudate volumes.