SYDNEY - A brain signal test invented by Australian scientists may provide the first objective and safe way for doctors to diagnose children with attention deficit hyperactivity disorder (ADHD).
The test also appears to confirm that the condition, which reportedly affects 5% to 8% of children, has a biological basis. The test, known as steady state probe topography, found significant differences in activity in the front of the brain in 13 boys with the disorder, compared with 18 "normal" boys.
Richard Silberstein and colleagues at the Center for Applied Neurosciences at Swinburne University of Technology in Melbourne gave the children visual exercises asking them to respond when the letter "X" appeared on a screen, with the letter "A" appearing shortly before to warn them.
While the front lobe of the brain in "normal" children was activated by the exercise, the same site in children with the attention-disorder was not activated.
"If anything there was a slight reduction (in brain activity)," the university professor said.
"If these parts of the brain are not properly active, you tend to be more distractable."
It has often been seen as a paradox that some children with ADHD are given brain-stimulating drugs such as methyl phenidate, given the children appear well-stimulated anyway, he observed. But this work appears to confirm that the brain in such children needs stimulating.
While it is too early for the test to be made available for general use, it may form the basis of a future test to be used in hospitals to test children with the disorder, Silberstein said.
A diagnosis of ADHD is currently based on subjective opinion, with no scientifically accepted test available.
Silberstein said this was why estimates of how common the disorder is varied widely, anywhere from 3% to 13% of children. He was skeptical about the higher figure and the true figure was probably somewhere in the middle.
"It depends on where you draw the line," Silberstein said.
"When is it (the disorder) and when is it normal, natural restlessness?"
Until now, other tests have given scientists only a poor indicator of what is happening in the brain and they have been loath to use them on children because they use radioactive substances.
The steady state probe topography test does not use radioactive material.
The Australian scientists have been invited to present their work and discuss their test at the New York Academy of Sciences in May.
Silberstein said boys were six to nine times as likely as girls to have ADHD but the reason for the gender imbalance was unknown. One theory is that it may be because of developmental differences in the brain between boys and girls.
The test will be used to study treatment regimes on ADHD children in an effort to tailor drug therapy for patients.
Copyright © 1996 Maclean Hunter Publishing Limited
Reprinted with permission.
Internet Mental Health (www.mentalhealth.com) copyright © 1995-2011 by Phillip W. Long, M.D.