Autism Linked to Head Size
> 1/31/2008 3:32:27 PM

Recent advancement in our understanding of autism has fueled hopes of early detection and treatment of the disorder. Last week, we reported on the exciting find that abnormalities in chromosome 16 can help predict autism. However, we are a long way from locating all of the genetic contributors to the disorder, and there may be environmental factors of which we are not yet aware. Another, more easily discernible, factor is explored in a study from the University of Washington, published recently in the Journal of Child Neurology.

There are many signs that a child may be autistic— lack of eye contact, preoccupation with certain objects, repetitive movement— but many of these signs are difficult to evaluate objectively or do not become apparent until after the first few years. There have been a few suggestions that head circumference correlates with autism, but these early studies were inconclusive. This Washington study goes far towards confirming the correlation because it adjusts for body size and looks at head growth rather than head size. This is not as strange as it may seem at first. While it might seem that the more brain matter the better, pruning out neurons is a crucial part of childhood development. Brain-scans have shown that autistic children have excessive grey matter in some regions of the brain, such as the parietal lobes.

It turns out that autistic children are not more likely to be born with large heads. Rather, they are born with average-sized heads (some studies suggest that they may even be below-average at birth), which then grow more rapidly than average between 7 and 10 months. This held true for both early and late-onset autism (where a normally developed child’s abilities suddenly deteriorate). The link was not common to cognitive problems in general because children with unrelated developmental delays did not show abnormal head growth.

Around 60% of the autistic subjects showed significantly accelerated head growth. While this is far from a sure detection method, it is very easy for doctors and parents to look for abnormal head growth and then look more carefully for other signs. It is possible that early preventative measures can lessen the severity of autism, so head growth, which can be detected before many behavior problems, could be used as a valuable warning sign.

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