Observations of increased brain size and head circumference in autism spectrum disorder (ASD) are certainly nothing new [1, 2], with previous work having suggested accelerated growth rates as potential early warning signs of risk of ASD . However, an interesting study published in Nature reports additional evidence, including timing of this event and its relationship with behavioral symptoms .
Hazlett and colleagues conducted a prospective anatomical MRI study of infants at high vs. low familial risk of ASD and found evidence that early post-natal hyper-expansion of cortical surface area may play a role in the development of ASD . Furthermore, this cortical surface area increase (which was observed between 6-12 months) was linked with increases in total brain volume (at 12 - 24 months) and social deficits (at 24 months).
In terms of potential underlying mechanisms the authors discuss previously suggested mechanisms such as increase proliferation of neural progenitor cells, increase in number of mini-columns and decreased pruning.
- Piven, J. et al. An MRI study of brain size in autism. Am. J. Psychiatry 152, 1145–1149. 1995.
- Courchesne, E. et al. Unusual brain growth patterns in early life in patients with autistic disorder: an MRI study. Neurology 57, 245–254. 2001.
- Courchesne et al. Evidence of brain overgrowth in the first year of life in autism. JAMA. 2003.
- Hazlett et al . Early brain development in infants at high risk for autism spectrum disorder. Nature. 2017.