About A study published in the July 16, 2003, issue of the Journal of the American Medical Association has found that a small head circumference at birth that is followed in the first year by an excessive increase in head circumference is linked to autism.
The findings of this study, conducted by researchers at the University of California, San Diego (UCSD) School of Medicine and Children’s Hospital and Health Center, is meaningful in terms of earlier diagnosis that can lead to earlier intervention and therefore to improved outcomes for children diagnosed with autism.
Autism is usually diagnosed by age 3; diagnosis is made base on observation of behavior, not a medical test. The earlier the diagnosis is made, the earlier treatment can begin. The early warning sign of increased brain growth occurs before behavioral symptoms of autism are noted.
Researchers in the UCSD study found that the rapid brain growth in children with autism means that “when the brain is experiencing the world and deciding how to construct itself, it’s growing too fast in the infant with autism,” according to the study’s senior author Eric Courchesne, Ph.D. In short, the brain cannot keep up with experiences and information and this makes “it very hard for autistic children to make sense of the world they live in,” says Courchesne.
The more excessive the brain growth, the more severe autism is, according to study results.
Researchers studied medical records of 48 children aged 2 to 5 who have an autism diagnosis; head circumferences were compared to the Centers for Disease Control and Prevention’s growth charts for normal development. The findings were that, on average, the head circumference of autistic children at birth was smaller than about 75 percent of other newborns. However, in the first year, these children had a rapid growth in brain size, reaching the 85th percentile (only 15 % of other newborns had a smaller head size) at around 1 year to 14 months old. Then, brain growth slowed.
Courchesne explains: “This burst of overgrowth takes place in a brief period of time, between about two months and six to 14 months of age. 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.”
This study, according to Courchesne, “provides, for the first time, a developmental process to target for animal model studies of the disorder. Animal models that accurately mimic these abnormal growth events will be necessary in order to discover causes and biological treatments for autism. 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 behavior to develop down more normal paths.”
While certain other conditions such as hydrocephalus or certain metabolic disorders can cause a large head circumference, they are much less common than autism.
Research has found that experience-guided growth is beneficial to human brain development. Experiences that pass through certain pathways in the brain lead to higher order neurobehavioral functions and skills, such as motor skills, linguistic, emotional, and cognitive skills.
The findings of this study have positive implications for treatment. Courchesne states, “Using our findings as an early indicator of autism, intervention might begin two or three years earlier when the brain might be at a more malleable stage and so, might result in a better outcome for the child.”
While all it takes to measure head circumference and, consequently, brain size, is a tape measure, not all pediatricians include this in routine visits. The research team advocates routine head circumference measures in the first year of life.