The very earliest description by Kanner indicated that large head size was associated with autism spectrum disorder. Yet, since then, opinion has ranged from those who argue that head and brain size is a general feature of autism spectrum disorder (ASD) to those who posit that this association is an artifact. We selectively review the literature on macrocephaly and megalencephaly in ASD and come to the conclusion that head and brain enlargement is characteristic of only a subset of approximately 15% of males with ASD. It appears that this is much less common in females. Moreover, the widespread notion that early macrocephaly and megalencephaly is followed by normalization of head/brain size is not supported by essential longitudinal studies. Given that an enlarged brain is a feature of one form of ASD, the critical remaining issues are what causes the abnormal brain enlargement and whether this has consequences on the clinical and cognitive outcomes of the affected individuals.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)