Attention-deficit hyperactivity disorder, or ADHD, is a neurodevelopmental disorder that affects 3 to 5 percent of children in the United States. Of these children, 50 percent will continue having symptoms of the condition even as adults. ADHD seems to run in families, and is linked to such environmental toxics as lead. The brain of an ADHD patient is different both in structure and function when compared to the brain of a healthy person. Several imaging methods can be used to study the structure of a brain affected by ADHD.
MRI
MRI, or magnetic resonance imaging, scans apply strong magnets to study the structure of the brain. Dr. F. Xavier Castellanos and colleagues used this safe, non-invasive method to demonstrate that the brain of ADHD patients seems to be smaller in size than those of healthy controls. Their study, published in the "Journal of the American Medical Association" in October 2002, showed that the biggest difference in volume between these two groups was seen in the prefrontal cortex. This area is responsible for such higher order cognitive functions as planning and decision-making. MRI scans can be used to study if the brain is developing normally and if certain areas of the brain are showing abnormalities that are typical of ADHD. MRI scans can also be run after neuropsychological tests have shown deficits in such cognitive abilities as memory to confirm these findings, and to find out why patients are having such problems.
FMRI
FMRI, or functional magnetic resonance imaging, uses the same technique as MRI, but unlike MRI that focuses on the structure of the brain, fMRI studies how the brain functions. It can be used, for example, to study the neurophysiological basis of different symptoms shown by ADHD subgroups. Dr. Mary V. Solanto and colleagues asked ADHD patients to respond differently to two kinds of visual stimuli. Their results, published in the "Journal of Neuroimaging" in July 2009, showed that the temporal and parietal regions of the brains were activated more in predominantly inattentive ADHD patients as compared to those with a combination of both inattentive and hyperactive symptoms. FMRI can be used to investigate how the brain of a person with ADHD works when he is performing the kind of tasks that are typically hard for him, such as problem solving or reading.
PET
PET, or positron emission tomography, is a type of nuclear medicine imaging that applies small amounts of radioactive material to study brain functions. It measures important bodily functions like the use of oxygen or blood flow to investigate what areas of the brains are active while the subject is performing a task. Abnormal activation levels might explain the symptoms that the patient is experiencing. Some neurotransmitters, such as dopamine, have been linked to ADHD. DR. Thomas J. Spencer and colleagues employed PET to study dopamine regulation in adult ADHD patients and healthy controls, and found significant differences in certain areas of the brain between these two groups.
References
- "Journal of American Medical Association": Developmental Trajectories of Brain Volume Abnormalities in Children and Adolescents
- "Journal of Neuroimaging": Event-related fMRI of Inhibitory Control in the Predominantly Inattentive and Combined Subtypes of AD/HD
- "Biological Psychiatry": Further Evidence of Dopamine Transporter Receptor Dysregulation in ADHD: A Controlled PET Imaging Study Using Altropane
- Surgery Encyclopedia: Magnetic Resonance Imaging
- RadiologyInfo: Functional MR Imaging (fMRI) - Brain
