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An increased incidence of macrocephaly has been found among autistic children estimated at 20%. Brain development in autism shows accelerated growth in early life that results in brain enlargement in childhood. Based on this consistent finding in a subgroup of children with autism, theories have been raised regarding the relationship between macrocephaly and the pathogenesis of autism.
Objectives: To evaluate the prevalence of abnormal head circumference of children with autism in one district of Israel and to compare it to the published data on autistic children, and to the head circumference of children with developmental language disorder (DLD). Methods: The head circumference of all children diagnosed with autism and Pervasive Developmental Disorder NOS (by DSM IV criteria) during 2000-2008 at the child development centers in the Shfela and Jerusalem districts of Maccabi Healthcare Services were searched from their computerised files. Only children with documented measurements were included. The measurement at the first evaluation was collected. Exclusion criteria were: severe neurologic deficits, genetic syndromes and S/P prematurity. The control group included children diagnosed with DLD, with or without gross and fine motor delays. All children with DLD who were diagnosed during 2006-7, were included in alphabetical order to match the number of children with autism. An additional exclusion criterion was mental retardation. Macrocephaly was defined as a head circumference >97th percentile and microcephaly as a head circumference <3rd percentile ( Nellhaus head circumference charts, 1968). 296 children (250 boys [84.5%]) with autism met the above criteria. The mean age for head circumference measurement was 2 years and 8 months. Macrocephaly was found in 3.7% (P=0.7 NS) and microcephaly in 3% of children with autism. 299 children with DLD (228 boys [76.3%]) were included. Macrocephaly was found in 2.7% and microcephaly in 9.4% (P<0.0001). Mean age at their first measurement was 3 years and 10 months. Conclusions: The prevalence of macrocephaly among children with autism in Israel is similar to the expected in the normal population and in children with language impairment. The overall distribution of the head circumference measurements in autistic children is typical. The lack of a large subgroup of children with autism and macrocephaly suggests a possible different genetic background of Israeli children with autism. The unexpected proportion of children with DLD and microcephaly might reflect some undiagnosed genetic or environmental causes and should be further investigated.