Changes in the brain of a child suffering from attention deficit/hyperactivity disorder (ADHD)has been identified that can help doctors diagnose the condition affecting 3–5% of all schoolgoing children in India.

There is no single test capable of diagnosing a child with the disorder. Consequently,difficultchildren are often incorrectly labelled with ADHD, while others with the disorder remain undiagnosed.

Using functional magnetic resonance imaging (fMRI), researchers have identified abnormalities in brains of children with ADHD that will serve as a biomarker for the disorder, according to a study presented at the annual meeting of the Radiological Society of North America (RSNA) here on Monday.

ADHD is one of the most common childhood disorders in India. Symptoms, which may continue into adulthood, include inattention, hyperactivity and impulsivity behaviours.

"Diagnosing ADHD is very difficult because of its wide variety of behavioural symptoms," said lead researcher Xiaobo Li, assistant professor of radiology at Albert Einstein College of Medicine in New York.

"Establishing a reliable imaging biomarker of ADHD would be a major contribution to the field," she said. Li and her colleagues performed fMRI on 18 typically developing children, and 18 children diagnosed with ADHD, aged between 9 and 15.

While undergoing fMRI, the children were engaged in a test of sustained attention in which they were shown a set of three numbers and asked whether subsequent groups of numbers matched the original set. For each participant, fMRI produced a brain activation map that revealed which regions of the brain became activatedwhen the child performed the task. The researchers also compared the brain activation maps of the two groups.

Children with ADHD showed abnormal functional activity in several regions of the brain involved in the processing of visual attention information. The researchers found that communication among the brain regions within this visual attention–processing pathway was disrupted in children with ADHD.

"Children withADHD are using partially different functional brain pathways to process the information, which may be caused by impaired white matter pathways involved in visual attention information processing," Dr Li said. She said much of the research conducted on ADHD has focused on the impulsivity component of the disorder.

"Inattention is an equally important component of this disorder," she said, "and our findings contribute to understanding the pathology of inattentiveness in ADHD."

India has witnessed a 175% rise of ADHD among children in the last six years, according to Assocham. Nearly one in 20 children in metros suffers from ADHD, it says. The Assocham study found that more boys are affected by ADHD than girls.