Seattle Post-Intelligencer; ABC Australia; Adam Feinstein, 16/07/2003
SAN DIEGO, California, USA: Head circumference in infants with autism may indicate the disorder before their behaviour does.
Children who are autistic appear to have accelerated brain growth well before any behavioural indicators appear, an American study has found.
Dr Eric Courchesne, professor of neurosciences at the University of California-San Diego and director of the Center for Autism Research at the Children's Hospital and Health Center in that city, has found that more than half of autistic children have an enlarged brain by the time they reach 14 months. This is the first time a potential early warning sign for autism has been identified.
Autism begins very early in life, but is not usually identified until a child shows behavioural signs and symptoms beginning at two or three years of age. These include delayed speech, unusual social and emotional reactions and poor attention to, and exploration of, the environment.
The study looked at the medical records of 48 children with autism spectrum disorder aged two to five years. The researchers compared head measurements of children with autistic disorder with those from two databases that describe normal growth patterns in infants.
They found that the children with autistic disorder had a rapid and excessive increase in head circumference measurements, beginning several months after birth. The findings appear in the July 16, 2003, issue of the Journal of the American Medical Association.
"In our study, head size increased from the 25th percentile - based on the Centres for Disease Control and Prevention averages of healthy infants - to the 84th percentile in six to 14 months," the researchers wrote in their paper. "This excessive increase occurred well before the typical onset of clinical behavioural symptoms."
Statistically, 59 per cent of the infants with autistic disorder showed the accelerated growth, compared to only 6 per cent of the healthy infants.
The head circumference of 15 of the children had been taken at birth, one to two months, three to five months and then six to 14 months. The remaining 33 children had all had their heads measured at birth, and seven of those had also had a measurement at six to 14 months.
"This burst of overgrowth takes place in a brief period of time, between about two months and six to 14 months of age," Dr Courchesne said. "So, we know it cannot be caused by events that occur later, such as vaccinations for mumps, measles and rubella or exposure to toxins during childhood."
He added: "Once we know what causes this specific growth defect, it may be possible to use biological treatments to successfully intervene before the overgrowth begins, thereby allowing the brain and behaviour to develop down more normal paths.
"During this period of important learning and plasticity, when the brain is experiencing the world and deciding how to construct itself, it's growing too fast in the infant with autism. Without the guidance of experience and learning, the brain may be creating abnormal connections which make it very hard for autistic children to make sense of the world they live in," he added.
Vaccinations and exposure to environmental poisons such as mercury have both been thought to be possible causes of autism. A study earlier this year pointed to a genetic component in some cases traced to chromosome 15.
The key question for researchers is whether rapid brain growth - which in theory is too fast for vital neurological connections to form - is the cause or just a symptom of autism. Autism is only diagnosed later, as early as the age of two.
While the study was small it "is the first ... to our knowledge to find a potential early warning biological sign for autism and to link it to a later brain abnormality," Courchesne wrote. He agreed there is a need for a larger study.
The suggestion that people with autism had larger brains is not new: it was first put forward when the disorder was diagnosed in 1943. Since then, the observation has been confirmed through analysis and it is one of the most replicated neurobiological findings of autism. This new study helps determine when this brain-size increase occurs.
While an infant having a big head is not a certain indicator of autism, it does appear to be an important signal of heightened risk for the disorder, the authors said. Dr Janet Lainhart from the University of Utah School of Medicine agreed in an accompanying editorial.
While it is premature to conclude that increased rate of head growth is a universal feature of autism, Dr Lainhart said, she called for larger studies to be undertaken. She also suggested a study which specifically looks at the pattern of infant head growth and early autism.
Although no one had yet determined the cause of autism, the findings "give us information about the timing of abnormal brain development, and provide a timeframe for further research," said Ruth Carper, a neuroscience researcher involved in the study.
There are other reasons infants have big heads early in life, such as having water on the brain or certain types of metabolic disorders, the researchers noted. But those conditions are much less common than autism disorders, which occur in as many as 1 in every 160 children. According to the Autism Society of America, more than 1 million Americans, including adults, suffer from an autistic spectrum disorder.
When Dr Courchesne first broke this story to delegates at the Inaugural World Autism Congress in Melbourne, Australia, last November, he told Adam Feinstein, Editor of the Autismconnect and Awares websites: "If our study is replicated and found to be consistently true, then it may become a useful early warning of possible autism. That, in turn, allows the development of additional tests to verify the possible diagnosis of autism. It opens up the opportunity for a whole new realm of treatments at a much earlier stage. [The simple method of a tape-measure around the head of very young children] might turn out to be an amazingly useful tool in the early identification of children who are potentially at risk from autism ... I'm very optimistic that, in the span of five to seven years, researchers will have discovered major factors involved in this brain overgrowth, and once they do, I believe research will proceed at a tremendously fast pace. So I'm very hopeful."