Research Update: Down syndrome and Autism

July 28, 2008
Correlations of Autistic Behaviors Shown in Children with Down syndrome

Kennedy Krieger Research Update: Dr. Walter E. Kaufmann

In a continuation of his research looking at children with a co-diagnosis of both autism spectrum disorder (ASD) and other well-known genetic disorders, Dr. Walter E. Kaufmann and colleagues recently published a study that examined the difference in brain structure between children with either Down syndrome alone and children with both Down syndrome and ASD. Dr. Kaufmann and his research team at the Center for Genetic Disorders of Cognition and Behavior (GCB Center) at the Kennedy Krieger Institute believe this will provide more clues to the cause of autism, and lead to better diagnosis and care of children with both Down syndrome and ASD.

The study, which appears in the online journal NeuroReport, used anatomic MRIs to compare the brain scans of children with Down syndrome to children with both Down syndrome and autism, as well as a control group of typically developing children.

The study found that the brains of children with a co-diagnosis had significantly more white matter in the brainstem and cerebellum when compared to children with Down syndrome alone. The data also showed that children with both disorders exhibited an accelerated brain growth between the ages of two and five years-old. The volume of white matter in the children with a co-diagnosis tended to decrease slightly with age, but the volumes of white matter remained relatively constant in the group with Down syndrome alone.

The study supports the theory that the underlying cause of autism lies in the cerebellum, particularly the enlargement of the cerebellum due to increased white matter. The findings also suggest that the underlying mechanisms of ASD in Down syndrome may be shared, at least in part, with those in autism alone. The early pattern of accelerated brain growth in childhood with Down syndrome and a co-diagnosis of ASD resembles the pattern of head and brain growth typically observed in children with autism alone and differs from children with Down syndrome alone. These differences make it important for researchers conducting brain imaging studies on Down syndrome to carefully evaluate the presence of ASD, as autism in Down syndrome may often go undiagnosed.

Perhaps most importantly, the increased white matter in individuals with Down syndrome and a co-diagnosis of autism represents a distinguishing feature that is associated with abnormal behaviors which are typically seen in children with either disorder, namely repetitive motor movements known as stereotypies. Further research on autism in Down syndrome as well as autism in other conditions may help clarify the causes and functional consequences of autism in the general population.

anatomical MRI comparison of DS and DS+ASD