Brain Abnormalities Found in Children with ADHD

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Brain Abnormalities Found in Children with ADHD

Toronto (April 19, 1999) -- Children diagnosed with attention deficit hyperactivity disorder (ADHD) often have smaller overall brain volumes than normal children with significantly less gray matter in their frontal brain region, particularly in the right frontal region, according to a study presented during the American Academy of Neurology's 51st Annual Meeting April 17 - 24, 1999, in Toronto.

ADHD originates in childhood and is more frequent in males than females. Although many patients are inattentive and hyperactive/impulsive, one or the other pattern may be predominant. Children with ADHD have difficulty controlling their behavior because they are less capable of selectively attending to important stimuli while ignoring irrelevant stimuli.

"There is a lot of evidence that the brain's right hemisphere is dominant in attentional processes," said study author and neurologist Stewart Mostofsky, MD, of the Kennedy Krieger Institute and Johns Hopkins School of Medicine in Baltimore. "Abnormalities in the brain's right frontal structure and function may be contributing to the behavioral impairments associated with ADHD."

Along with less right frontal gray matter, the researchers also found that ADHD patients had smaller volumes of left frontal gray matter as well as right and left frontal white matter when compared to children without ADHD. However, these differences were not as large as differences seen in right frontal gray matter.

"Gray matter primarily consists of neurons, the actual cells of the brain," explains Mostofsky. "White matter, which could be thought of as the brain's 'wires,' is primarily made up of axons, the connections between cells, and their coverings called myelin."

The study included 12 boys diagnosed with ADHD and 14 boys without ADHD. All boys were between the ages of seven and 13.

Recently developed imaging techniques aided in this research. "The techniques used in this study allowed us to specifically identify frontal lobe abnormalities and accurately divide the various brain regions into gray matter, white matter and cerebrospinal fluid volumes," Mostofsky said.

Although ADHD is widely diagnosed, it is a complex disorder with much yet to be learned at the neurobiological level. Mostofsky stated, "Although these are preliminary findings, they contribute to our understanding that ADHD is a disorder of 'intention' (preparedness to respond) secondary to differences in frontal lobe development. A better understanding of the neurologic basis of ADHD could eventually contribute to better diagnosis and treatment."

This study was supported by grants from the National Institutes of Health.

The American Academy of Neurology, an association of more than 15,000 neurologists and neuroscience professionals, is dedicated to improving care for patients with neurological disorders through education and research.

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Editor's Note: Dr. Mostofsky will present the research at the American Academy of Neurology's 51st Annual Meeting in Toronto, Canada, during the Child Neurology II Scientific Platform Session on Monday, April 19, 1999, at 4:45 pm in Room 104D of the Metro Toronto Convention Centre.