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Abstract
50 years after Kanner's original 1943 description1 of large heads in autism, Bailey et al2 reintroduced the possibility of a relation between abnormalities in head size or brain volume and autism. In 1997, Stevenson et al3 found that macrocephaly was the single most consistent physical characteristic of children with autism. A subsequent study4 concluded that macrocephaly is an independent trait in autism. Compared with that in healthy volunteers, brain development in autism is abnormal, with accelerated growth in early life that results in brain enlargement in childhood.5 Brain volume in adolescents and adults with autism is, however, normal,6,7 probably because of a slight decrease in brain volume at the same time as normal children are having a slight increase.