ncc / article - brain development and autism clues /medscape

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y 28,2002  

Findings Shed Light on Brain Development in Autistic Patients- (from medscape

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http://www.medscape.com/viewarticle/439052

NEW YORK (Reuters Health) Jul 22 - In patients with autism, the brain appears

to grow rapidly in childhood and then decreases slightly in size, so that the

volume is similar to that of normal brains once adolescence is reached,

according to a report published in the July 23rd issue of Neurology.

Findings from another study indicate that several brain structures, including

the cerebrum and cerebellum, are larger in young children with autism than

similarly aged normal children or developmentally delayed children.

In the first study, Dr. H. Aylward, from the University of

Washington in Seattle, and colleagues used MRI to compare the brain volumes

of 67 autistic patients with those of 83 healthy volunteers. The head

circumference of all subjects was also measured. The subjects ranged in age

from 8 to 46 years.

The researchers found that in subjects 12 years of age and younger, brain

volumes were significantly larger in the autistic group than in the control

group. In older subjects, however, no significant differences in brain volume

were observed. In both age groups head circumference was greater in autistic

patients than controls, suggesting that the older patients probably had

increased brain volumes during childhood.

In another study, Dr. R. Dager, also from the University of

Washington, and colleagues used volumetric MRI to compare the sizes of

several brain structures in 3- to 4-year-old children with and without

autism. The study included 45 children with autism, 14 with developmental

delay, and 26 normal children.

Cerebral volume was significantly increased in autistic children compared

with the other two groups. In addition, volumes of the cerebellum, amygdala,

and hippocampus were increased in autistic children, but all of these

increases were proportional to the overall increase in total cerebral volume.

Structural abnormalities were observed more often in boys with autism than in

girls, but the statistical power of this observation is limited because the

study group only included seven girls. The structural findings did not

correlate with nonverbal IQ, the authors note.

In a related editorial, Dr. W. Mink, from the University of

Rochester in New York, and Dr. C. McKinstry, from Washington

University in St. Louis, discuss the implications of the current findings and

make suggestions for the focus of future research.

" We now have pretty good evidence that the brains of young autistic patients

are larger than those of healthy subjects, " Dr. Mink told Reuters Health.

" However, we still really don't know much about the biology of the disorder. "

Dr. Mink believes that future research should move beyond just describing the

differences between normal and autistic brains. " We really need to have

specific hypotheses, " he explained.

" For example, a fundamental problem in autism is language development and we

know the areas of the brain that are involved in language, " Dr. Mink noted.

" Therefore, a study could be done focusing specifically on abnormalities in

those areas, " he said. However, for studies like this to be successful a

homogeneous autistic population is needed, which can be difficult to find

because autism is such a heterogeneous disorder, he added.

Neurology 2002;59:158-159,175-192.

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