Motor stereotypies and volumetric brain alterations in children with Autistic Disorder.

Motor stereotypies are defined as patterned, repetitive, purposeless movements. These stigmatizing motor behaviors represent one manifestation of the third core criterion for an Autistic Disorder (AD) diagnosis, and are becoming viewed as potential early markers of autism. Moreover, motor stereotypies might be a tangible expression of the underlying neurobiology of this neurodevelopmental disorder. In this study, we videoscored stereotypies recorded during semi-structured play sessions from school age children with AD. We examined the effect of severity and persistence over time of stereotypies on brain volumetric changes. Our findings confirmed that the brain volume of school age children with AD is, on average, larger than that of age-matched typically developing children. However, we have failed to detect any sign of volumetric differences in brain regions thought to be particularly linked to the pathophysiology of stereotypies. This negative finding may suggest that, at least with respect to motor stereotypies, functional rather than structural alterations might be the underpinning of these disruptive motor manifestations of autism.