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TUESDAY, July 15, 2003 (HealthDayNews) -- For decades, the holy grail of autism research has been to find some measurable indication, a biological marker, which would detect the disorder before a child has any symptoms.
Now, researchers report in the July 16 issue of the Journal of the American Medical Association that two aspects of brain growth may be a tip-off: a smaller head circumference at birth and a sudden and excessive increase in head size between 1 to 2 months and 6 to 14 months of age.
"This study suggests that for a large percentage of children who go on to develop autism there are changes in their head growth and therefore changes in the relative development of their brain that are excessive and could be perhaps noted from pediatric monitoring before the end of the first year of life," says study co-author Natacha Akshoomoff, an assistant research scientist at Children's Hospital San Diego and an assistant professor of psychiatry at the University of California, San Diego.
Other experts, however, feel the findings are preliminary and will be most useful to researchers trying to pin down the underlying mechanisms of autism, not physicians trying to identify children who will develop the disorder.
"If you have 10,000 children going to a pediatrician, 600 of them are going to have an increased rate of head growth during infancy and be perfectly normal and 10 will have the increased rate of head growth and have autism," explains Dr. Janet Lainhart, a pediatrician who authored an accompanying editorial who is also an associate professor of psychiatry at the University of Utah in Salt Lake City. "What we cannot do right now is pick out those 10."
Autism initially manifests in children 2 to 3 years of age with behavioral changes including delayed speech as well as difficulty relating emotionally or socially to people and to the environment. Although the disorder (actually a cluster of disorders) is known to be neurobiological in origin, there are no clear neurobiological signs that it will emerge in a particular child.
Even though there is no cure, early intervention is considered crucial.
"During early childhood the brain is still developing, and so it has what's referred to as high levels of plasticity or ability to change," Lainhart explains. "If you could identify an infant who had not developed the full-blown syndrome of autism but who is having some subtle abnormalities of eye gaze and some subtle abnormalities of interacting with people, and if you could go after those and work really intensely at that age, the hope is that that would really help you to somewhat normalize brain development... The hope is that we could divert the normal course that brain development would otherwise take and at least ameliorate some of the disorder."
According to Lainhart, pediatricians already monitor children who have increased rates of head growth for developmental problems in general. "This study adds autism to the list of neurodevelopmental problems for which a pediatrician would normally monitor children closely," she says. "It's an important finding but on its own at the present time it may not help identify children who have autism early or, if it does, it's going to help with [only] a few children."
Complicating the picture is the fact that some children with autism do not have increased rates of head growth during infancy.
The authors of this study analyzed data, including head circumference, body length and body weight measurements from records of a small group of children (48 boys and girls) aged 2 to 5 years old with autism spectrum disorder (ASD). These children had previously participated in magnetic resonance imaging (MRI) studies that showed age-related changes in the brain.
Compared to two databases of healthy children, the children with autism had rapid and large increases in head circumference measurements which would indicate a growth in brain size. Head size increased in six to 14 months from the 25th percentile based on U.S. Centers for Disease Control and Prevention (CDC) averages of healthy infants to the 84th percentile. The increase occurred long before any symptoms.
While only 6 percent of healthy infants showed this growth spurt, 59 percent of infants with autistic disorder had the accelerated growth.
The findings are significant, but somewhat preliminary.
"If you combine this study with other studies that have already been done, the weight of the combined evidence now strongly suggests that this is a real phenomenon in autism," Lainhart says. "From a neurobiologic point of view, it is very important because it's objective, it's easy to measure and it's something that neuroscientists can really go after and try to better refine and make more specific so that it eventually helps identify kids with autism."
One day, Lainhart adds, "increased rate of head growth plus some subtle behavioral developmental indicators plus additional biological markers together might be able to pick those children out, or at least some of them."
More information
For more on autism, visit the Autism Society of America or the National Alliance for Autism Research.
