Autism Linked to Head Size
> 2/4/2008 2:32:32 PM

Recent advancement in our understanding of autism hasfueled hopes of early detection and treatment of the disorder. Lastweek, we reported on the exciting find that abnormalities in chromosome16 can help predict autism. However, we are a long way from locatingall of the genetic contributors to the disorder, and there may beenvironmental factors of which we are not yet aware. Another, moreeasily discernible, factor is explored in a study from the University of Washington, published recently in the Journal of Child Neurology.

Thereare many signs that a child may be autistic� lack of eye contact,preoccupation with certain objects, repetitive movement� but many ofthese signs are difficult to evaluate objectively or do not becomeapparent until after the first few years. There have been a few suggestionsthat head circumference correlates with autism, but these early studieswere inconclusive. This Washington study goes far towards confirmingthe correlation because it adjusts for body size and looks at headgrowth rather than head size. This is not as strange as it may seem atfirst. 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 greymatter in some regions of the brain, such as the parietal lobes.

Itturns out that autistic children are not more likely to be born withlarge heads. Rather, they are born with average-sized heads (somestudies suggest that they may even be below-average at birth), whichthen grow more rapidly than average between 7 and 10 months. This heldtrue for both early and late-onset autism (where a normally developedchild�s abilities suddenly deteriorate). The link was not common tocognitive problems in general because children with unrelateddevelopmental delays did not show abnormal head growth.

Around60% of the autistic subjects showed significantly accelerated headgrowth. While this is far from a sure detection method, it is very easyfor doctors and parents to look for abnormal head growth and then lookmore carefully for other signs. It is possible that early preventative measurescan lessen the severity of autism, so head growth, which can bedetected before many behavior problems, could be used as a valuablewarning sign.

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