[Seeking the aetiology of autistic spectrum disorder. Part 1: Structural neuroimaging]

Although the aetiology of autistic-spectrum disorder (ASD) remains unclear, great advances have been made to clarify the underlying neuroanatomical abnormalities and brain-behaviour relationships in autism. There is variability in the literature on structural neuroimaging findings in ASD. Early brain overgrowth is probably the most replicated finding in this subgroup. Additionally some specific brain regions are particularly implicated, including the frontal, limbic, basal ganglia and cerebellar regions. There is also evidence of volume abnormalities in both grey and white matter. New techniques, such as cortical-thickness measurements, surface morphometry and diffusion tensor imaging help to understand in more detail the patterns of abnormalities. More work is required, involving the use of large and homogeneous samples, to investigate the neuroanatomical determinants and their role in aetiology of ASD. The goal of this review is to summarise the available structural neuroimaging data and examine their implication for understanding of the neurobiology of ASD.