The brains of children with autism may be bigger than those of children who do not suffer from the disorder, according to a new study.

Using magnetic resonance imaging (MRI), researchers found evidence of brain enlargement in a number of children with autism.

Autism is a complex disorder that leads to social and communication problems and repetitive behaviors. The cause of autism is unknown, but some studies have suggested that abnormalities in brain volume may be associated with the disorder.

Brain Enlargement May Be Sign of Autism

The study was published in the Archives of General Psychiatry. Researchers examined brain volume and head circumference in 51 children with autism (aged 18 to 35 months) and 25 children in the same age group who were both developmentally delayed and normally developed.

Head measurements obtained from medical records were also examined in another larger sample of 113 children with autism and 189 healthy children, aged from 0 to 3 years.

The results showed that in children with autism there was significant enlargement in the volume of the brain region known as the cerebral cortex. That region is responsible for processing thought, perception, and memory, among other things.

Evidence of brain enlargement was found in both gray and white matter throughout this part of the brain.

No enlargement was found in the cerebellum, the region of the brain that deals with balance and coordination of movement.

The study also showed that autistic children’s head sizes appeared to be normal at birth but grew at an increased rate after the first year compared with the other children.

Researchers say the results confirm previous suggestions of brain enlargement and increased head circumference in children with autism by age 2, and these changes may begin to emerge after the first year of life.

By Jennifer Warner, reviewed by Louise Chang, MD

SOURCES:Hazlett, H. Archives of General Psychiatry, December 2005; vol 62: pp 1366-1376. News release, American Medical Association.