Shape mapping of the hippocampus in young children with autism spectrum disorder.

ABSTRACT

BACKGROUND AND PURPOSE: We hypothesized the occurrence of characteristic hippocampal-shape alterations in young children with autistic spectrum disorder (ASD) who also exhibit deficits on neuropsychologic tests of medial temporal lobe (MTL) function. MATERIALS AND METHODS: Coronal 3D MR images were acquired from 3- to 4-year-old children with ASD (n = 45) and age-matched children with typical development (n = 13). Children with ASD were further subclassified into those with autism disorder (AD, n = 29) or pervasive developmental disorder-not otherwise specified (PDD-NOS) (n = 16). Variations in hippocampal shape were evaluated by using large-deformation high-dimensional brain mapping. RESULTS: Hippocampal shape measures distinguished children with ASD from those with typical development; within the ASD sample, children with AD were distinguished from those with PDD-NOS. Hippocampal-shape alterations in children with ASD were correlated with degree of mental retardation and performance deficits on tests of MTL function. CONCLUSIONS: Children with ASD exhibited an alteration of hippocampal shape consistent with inward deformation of the subiculum. This pattern of hippocampal-shape deformations in the children with ASD was accentuated in the more severely affected subgroup of children with AD and was associated with deficits on neuropsychologic tests of MTL but not prefrontal function. Hippocampal-shape deformation in the children with ASD was observed to be similar to a pattern of hippocampal shape deformation previously reported in adults with MTL epilepsy. Although the children with ASD, and those with AD in particular, PDD-NOS are at high risk for epilepsy as they enter adolescence, the specificity and causal relationship of this pattern of hippocampal-shape deformation to the development of seizures is not yet known.