Macrocephaly
Macrocephaly
Description
The human adult brain reaches a total volume of about 1,700 ml where 80% of the volume is composed of parenchyma, 10% blood, and 10% cerebrospinal fluid. A subtle increase in the number and/or molecular fluid environment in the central nervous system could lead to significantly increased brain size. 1
Causes
Macrocephaly can be caused by megalencephaly(true atrophy or increase in numbers of the actual neurons or glial cells) or other conditions like hydrocephalus(an accumulation of cerebrospinal fluid in the brain) or cranial hyperostosis(an overgrowth of bone). 1
Connections with Autism
Macrocephaly occurs in 15-35% of autistic children and is more prevalent in autism than in children with learning delays(up to 15%). Macrocephaly has a higher prevalence across the spectrum even among very high functioning ASD children. Typically, it manifests in children around 1-3 years and is not present at birth. Most of the increase in volume is due to white matter increase. However, no consistent brain pathology has been found. ASD probands with PTEN mutations have been found. Studies suggest that macrocephaly is segregating independently in the non-autistic family members.1
References
1. Williams CA et. al. Genetic disorders associated with macrocephaly.Am J Med Genet A. 2008 Aug 1;146A(15):2023-37. PMID 18629877
