MRI provides a noninvasive way to measure iron levels in the brains of people with attention deficit hyperactivity disorder (ADHD), according to a recently published study (Adisetiyo V et al. Attention-deficit/hyperactivity disorder without comorbidity is associated with distinct atypical patterns of cerebral microstructural development. Hum Brain Mapp. 2013 doi: 10.1002)
ADHD is a common disorder in children and adolescents that can continue into adulthood. Symptoms include hyperactivity and difficulty staying focused, paying attention and controlling behavior. It has been estimated that ADHD affects three to seven of children of school-age.
Psychostimulant medications such as Ritalin are among the drugs commonly used to reduce ADHD symptoms. Psychostimulants affect levels of dopamine, the neurotransmitter in the brain associated with addiction.
“Studies show that psychostimulant drugs increase dopamine levels and help the kids that we suspect have lower dopamine levels,” said Dr Vit Adisetiyo, of the Medical University of South Carolina in Charleston, SC, USA. “As brain iron is required for dopamine synthesis, assessment of iron levels with MRI may provide a noninvasive, indirect measure of dopamine.” Dr. Adisetiyo and colleagues explored this possibility by measuring brain iron in 22 children and adolescents with ADHD and 27 healthy control children and adolescents using the relatively new MRI technique, magnetic field correlation (MFC) imaging. “MRI relaxation rates are the more conventional way to measure brain iron, but they are not very specific,” Dr. Adisetiyo said. “We added MFC because it offers more refined specificity.” The results showed that the 12 ADHD patients who had never been on medication had significantly lower MFC than the 10 ADHD patients who had been on psychostimulant medication or the 27 typically developing children and adolescents in the control group. In contrast, no significant group differences were detected using relaxation rates or serum measures. The lower brain iron levels in the non-medicated group appeared to normalize with psychostimulant medication.
The ability of MFC to noninvasively detect the low iron levels may help improve ADHD diagnosis and guide optimal treatment
If the results can be replicated in larger studies, then MFC might have a future role in determining which patients would benefit from psychostimulants—an important consideration because the drugs can become addictive in some patients and can lead to abuse of other psychostimulant drugs like cocaine.