Objectives: In this report, we examined the structural MRI data from a sample of 6 month olds at high risk for autism and typically-developing controls with follow-up scans at age 12 months.
Methods: Imaging data was obtained from all four IBIS data collection sites. In addition to an imaging protocol that included structural MRI and DTI scans, subjects received include a battery of behavioral and developmental tests. All the brain MRI scans were completed on a 3T Siemens scanner during natural sleep. This longitudinal study is currently ongoing, so we are reporting on findings from the cross-sectional data at age 6 months and age 12 months.
Results: Brain volume measures were performed on 83 high-risk and 34 low-risk controls infants at age 6 months. At the 6 month time point, we measured intracranial volume (ICV), total brain volume (TBV), cerebrum, cerebellum, lateral ventricles, and head circumference. At age 12 months, we were also able to examine the tissue volume of the cortical lobes (frontal, temporal, parietal, occipital). Statistical analyses included covariates such as gender, site, body size, and age at scan. We find no group difference in the brain volumes at age 6 months, with the exception of significantly decreased size of the lateral ventricles in the high-risk siblings (right p = .01, left p = .03). We find no group differences in the global brain volume measures at age 12 months. Our data on the cortical lobe volumes is preliminary at this point in time, as we have not yet completed quality checks (QC) on our data, but this data should be available for the meeting. Preliminary looks at brain volume across this longitudinal period (6-12 months) finds evidence for age effects but so far no group differences are observed in the rate of brain growth.
Conclusions: The results from this ongoing study provide evidence for normal total, cerebrum, and cerebellum volume at age 6 months in infants at high-risk for autism, with bilaterally decreased volume of the lateral ventricles observed in the high-risk infants. Preliminary data at 12 months indicates that there are no global brain differences at this time. Analysis is currently ongoing to characterize regional cortical lobe volumes and potential related group differences.