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CHICAGO -- Children diagnosed with attention deficit-hyperactivity disorder (ADHD) appear to have brain abnormalities that can be observed with MRI, findings that may allow for a more objective diagnosis of the disorder, a researcher suggested here.

After analyzing MRI scans of almost 8,000 children, investigators observed abnormal connectivity in the brain networks involved in memory processing and auditory processing among those with ADHD, said Huang Lin, PhD, a postgraduate fellow at the Yale School of Medicine in New Haven, Connecticut.

They also observed a thinning of the brain cortex and significant white matter microstructural changes, especially in the frontal lobe of the brain, according to her presentation at the annual meeting.

"The frontal lobe is the area of the brain involved in governing impulsivity and attention or lack thereof -- two of the leading symptoms of ADHD," Lin told MedPage Today. "We were able to see, using structural MRI, that the surface area and volume of the gray matter in the brain of children with ADHD diagnoses were reduced. Using diffusion-weighted imaging, we could also see that the white matter integrity was disrupted among children with ADHD. This may be a cause of inattention in these children."

"We have not yet looked into whether treatment of these children has an impact on those brain changes that we see on the current scans," Lin noted. "Our study was aimed at showing that ADHD is not only an external-like syndrome but these children actually have changes in the brain like any other neurological disease."

"There's a need for a more objective methodology for a more efficient and reliable diagnosis," she continued. "ADHD symptoms are often undiagnosed or misdiagnosed because the evaluation is subjective. Our study underscores that ADHD is a neurological disorder with neuro-structural and functional manifestations in the brain -- not just a purely externalized behavior syndrome."

Lin and co-authors used MRI data from the NIH-sponsored multisite Adolescent Brain Cognitive Development (ABCD) study, which is the largest long-term study of brain development and child health in the U.S. It includes data on 11,878 children who were 9-10 years old at enrollment, from 21 centers across the country.

After applying exclusionary criteria to the cohort, Lin and colleagues were able to identify 1,798 children who had been diagnosed with ADHD, and their MRI scans were compared with those of 6,007 children without an ADHD diagnosis.

All the children had undergone structural MRI scanning, diffusion tensor imaging, and resting-state functional MRI. The researchers inputted the information into machine-learning technology that assisted in handling the data generated, Lin explained.

"Nowadays a lot more kids are diagnosed with ADHD compared to the past," Max Wintermark, MD, chief of neuroradiology at the University of Texas MD Anderson Cancer Center in Houston, told MedPage Today. "We can't be sure if it is because the prevalence has increased or because we have less patience with those kids, and we characterize them with ADHD. It is good to have some kind of biomarker, because that can help you when someone has conditions that can be relatively difficult to diagnose. It is good to have an objective fact that we can rely on in making such a diagnosis."

"The study found changes in the central lobe of the brain among those with ADHD, and that kind of makes sense, because that is where we have our executive function such as self-control," said Wintermark, who was not involved with the study.

Lin said the team is now working to tweak the machine-learning component, perhaps to assess the impact of treatments, and to see if the algorithm can differentiate between subtypes of ADHD.

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