No significant brain volume decreases or increases in adults with high-functioning autism spectrum disorder and above average intelligence: a voxel-based morphometric study.

Autism spectrum disorder (ASD) is increasingly being recognized as an important issue in adult psychiatry and psychotherapy. High intelligence indicates overall good brain functioning and might thus present a particularly good opportunity to study possible cerebral correlates of core autistic features in terms of impaired social cognition, communication skills, the need for routines, and circumscribed interests. Anatomical MRI data sets for 30 highly intelligent patients with high-functioning autism and 30 pairwise-matched control subjects were acquired and analyzed with voxel-based morphometry. The gray matter volume of the pairwise-matched patients and the controls did not differ significantly. When correcting for total brain volume influences, the patients with ASD exhibited smaller left superior frontal volumes on a trend level. Heterogeneous volumetric findings in earlier studies might partly be explained by study samples biased by a high inclusion rate of secondary forms of ASD, which often go along with neuronal abnormalities. Including only patients with high IQ scores might have decreased the influence of secondary forms of ASD and might explain the absence of significant volumetric differences between the patients and the controls in this study.