Brain Imaging of Preschoolers with ADHD Detects Differences Linked to Symptoms

Researchers have found differences in the brain development of preschool children with symptoms of attention-deficit/hyperactivity disorder (ADHD). Their findings showed the area of the brain important for cognitive and motor control was smaller in these children than in typically developing children. Ground-breaking for its use of neuroimaging in very young, preschool age children with early symptoms of ADHD, this study’s examination of brain differences may offer new insights into potential early interventions for the disorder.

ADHD is the single most common child behavioral diagnosis, affecting approximately two million children. This highly prevalent developmental disorder is characterized by inattentiveness, hyperactivity, and impulsivity. By age four, as many as 40% of children have sufficient problems with attention to be of concern to parents and preschool teachers. This observation is important, as children whose symptoms begin in early childhood are at high risk for academic failure and grade repetition.

Since preschool children with symptoms of ADHD are at significant risk for social and academic difficulties compared to typically developing children, researchers set out to determine how to identify the disorder as early as possible in order to begin intervention earlier and facilitate better outcomes. Earlier magnetic resonance imaging (MRI) studies have provided some insights into brain differences associated with ADHD, but these have almost exclusively focused on children ages seven and older.

In the current study, researchers from the Kennedy Krieger Institute (Baltimore, MD, USA), who published their findings June 10, 2011, in the journal Clinical Neuropsychologist (e-publication ahead of print), analyzed brain images in preschoolers (ages four and five) both with and without symptoms of ADHD, particularly looking at cortical and basal ganglia volumes and the size of these specific areas of the brain. Researchers studied high-resolution MRI brain images in 26 preschoolers, 13 presenting with ADHD symptoms and 13 without, and found differences in the caudate nucleus. The caudate nucleus is a small structure in the subcortical region of the brain and is associated with cognitive and motor control.

The study’s findings revealed that children with ADHD symptoms had considerably reduced caudate volumes compared to the children who did not present with ADHD symptoms. Moreover, these caudate volumes were significantly correlated with parent ratings of hyperactive/impulsive symptoms. Cortical volumes, however, were not associated with symptom severity. The investigators concluded that differences in basal ganglia development, particularly the caudate nucleus, appear to play an important role among children presenting with early onset symptoms of ADHD.

“Clinically, this abnormal brain development sets the stage for the symptoms of ADHD that contribute to cognitive challenges and problems in school,” said Dr. Mark Mahone, lead author and director of Neuropsychology at the Kennedy Krieger Institute. “Earlier identification and treatment of children presenting with attention problems in the preschool years may minimize the impact of ADHD in the long-term.”

As part of this longitudinal study, researchers will continue to track the brain development of these children to determine if abnormalities persist or regress with age.

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Kennedy Krieger Institute