Attention Deficit Hyperactivity Disorder (ADHD) is one of the most common neurobehavioral disorders in children, according to the Centers for Disease Control and Prevention. The condition can persist into adulthood, causing difficulty in paying attention or controlling impulsive behavior. Diagnoses of this disorder increased considerably over the decade leading up to 2012, with 2 million more children being diagnosed in 2011-2012 than were diagnosed in 2003-2004. Approximately one million more children take medication for ADHD than did a decade ago, according to a paper published in the Journal of the American Academy of Child and Adolescent Psychiatry in 2013.
There is a growing body of medical literature identifying a possible abnormality in iron homeostasis in the brains of children with ADHD, and in fact abnormal iron metabolism in the brain has been associated with other neurological disorders. Earlier research in childhood development has found that children with iron deficiency in the brain can be slower to develop cognitively, may be lethargic, and may have problems with attention span and cognition.
Challenges of Diagnosing ADHD
Diagnosis of ADHD can be tricky, and is an inexact science. Children who exhibit symptoms of ADHD are believed to have lower levels of dopamine in the brain. Psychostimulant medications like Ritalin are commonly prescribed to reduce ADHD symptoms because they increase dopamine levels in the brain. But measuring dopamine levels in the brain using magnetic resonance imaging (MRI) requires the use of radioactive contrast agents, and many parents of children with ADHD decline to use these contrast agents in their children.
However, a new medical imaging technique using MRI to examine levels of iron in the brain could offer a new diagnostic tool for ADHD. Iron in the brain is required for dopamine synthesis, so researchers at the Medical University of South Carolina (MUSC) hypothesized that assessing iron levels in brains of children with ADHD could provide an indirect measure of brain dopamine levels without requiring the use of radioactive contrast agents. That’s because areas of the brain with higher iron levels show up differently on MRIs than areas with low iron levels.
Brain Iron Levels in Untreated Children With ADHD
MUSC researchers measured brain iron levels in 22 children and adolescents with ADHD as well as in 27 healthy children without ADHD. Among the children diagnosed with ADHD, 12 had never used medication for the condition. Brains of all the subjects were imaged on a 3-Tesla scanner, and the children’s blood iron levels in the body were measured using a blood draw.
The medical imaging scans of the 12 patients who had never used ADHD medication showed significantly lower indexes of brain iron than the ADHD patients who had been taking psychostimulant medication. They also showed lower levels of brain iron than the control subjects. Children who had been medicated for ADHD had brain iron indexes that were comparable to those in the controls. This suggests that brain iron may reach normal levels in children with ADHD who are treated with psychostimulant medication.
Resting State Functional MRI in Children With ADHD
Measurement of brain iron levels using medical imaging is not the only way MRI may be someday used to diagnose ADHD. Researchers in the Department of Radiology at West China Hospital of Sichuan University in China used resting-state functional MRI (rfMRI) to examine the brains of 33 boys with ADHD and 32 similarly aged boys without ADHD.
The medical imaging technique of rfMRI measures brain activity when a person is not focusing on a particular task. In this study, participants underwent “executive function” tests, which measure control of processes like planning, working memory, and reasoning, processes that tend to be impaired in children with ADHD.
Once rfMRIs were correlated with results of executive function tests, the researchers found that the boys with ADHD had different structure and function in two parts of the brain: the orbitofrontal cortex (which is involved in strategic planning) and the globus pallidus (which plays a role in impulsive behaviors). They also found abnormalities in connections between brain networks linked to executive function, and these were abnormalities associated with cognitive, emotional, and behavioral difficulties. The researchers say that larger studies will be required to validate these promising preliminary findings.
Future Research on Brain Iron Levels
The MUSC medical imaging study of brain iron levels was a cross-sectional study, and researchers say the next step is to conduct a longitudinal brain iron study of patients diagnosed with ADHD before and after treatment with psychostimulant drugs. Such a study would determine if brain iron levels were low initially and then increased after treatment with medication, as one would hypothesize based on the initial study.
Another avenue of research the MUSC researchers are interested in has to do with people who abuse illicit psychostimulant substances like cocaine. Prescribed psychostimulant medications are addictive in some patients, and can lead to abuse of other psychostimulant substances. Researchers hope to look at brain iron levels in cocaine addicts as a separate study. Researchers hypothesize that since un-medicated people with ADHD show low brain iron levels and people without ADHD show normal brain iron levels, that people who are addicted to cocaine would have higher brain iron levels “because they are bombarding their system with psychostimulants.”
The Centers for Disease Control and Prevention says that 6.4 million children from ages 4 to 17 were diagnosed with ADHD in the 2011-2012 time frame. The American Psyciatric Association estimates that between 3% and 7% of school-aged children are affected by ADHD. Though ADHD affects both children and adults, it is more common in children, and is more prevalent in boys.
Diagnosis of ADHD is not always straightforward, but studies like the one at MUSC and at Sichuan University offer the possibility that the use of medical imaging may become more important in diagnosing the condition as more is learned about how it affects brain structure and function.
SteleRAD is a south Florida radiology specialty practice that is owned and operated by Board-certified radiologists. SteleRAD’s 23 staff radiologists are skilled and experienced in numerous medical imaging subspecialties, including fluoroscopy, ultrasound, diagnostic radiology, and various types of magnetic resonance imaging. SteleRAD is ready to help your medical facility cope with sudden increases in caseload, to cover for a physician who is unavailable, or to offer Board-certified second opinions. If you would like to know more about SteleRAD’s comprehensive medical imaging services, call 954-358-5250, or contact SteleRAD online.