A fairly new type of magnetic resonance imaging (MRI), called diffusion tensor imaging (DTI), has been used to examine the brains of children diagnosed with attention deficit hyperactivity disorder (ADHD) and ADHD children were found to have abnormal fiber pathways that connect the different parts of the brain.
CHICAGO – Children with attention deficit hyperactivity disorder (ADHD) display anatomical brain abnormalities beyond chemical imbalance, according to research presented at the annual meeting of the Radiological Society of North America (RSNA). Stimulant medications prescribed to balance brain chemistry appear to normalize some of these brain irregularities, a second study reported.
"We found abnormality of the fiber pathways in the frontal cortex, basal ganglia, brain stem and cerebellum," said lead author of both studies, Manzar Ashtari, PhD., associate professor of radiology and psychiatry at North Shore-Long Island Jewish Health System in New Hyde Park, N.Y.
"These areas are involved in the processes that regulate attention, impulsive behavior, motor activity, and inhibition--the key symptoms in ADHD children," Dr. Ashtari said. "They are also known to be part of a bigger circuit in the brain that establishes communication between the frontal lobe and cerebellum."
According to the National Institute of Mental Health (NIMH), ADHD affects 3 to 5 percent of children in the United States. Children with ADHD have difficulty controlling their behavior or focusing their attention.
Using diffusion tensor imaging (DTI) to compare 18 children with diagnosed ADHD with 15 control children to evaluate the brain's white-matter fiber development, Dr. Ashtari's team found differences in the brain fiber pathways that transmit and receive information among brain areas.
"Typically ADHD is described as a chemical imbalance, but our research has shown that there may also be subtle anatomical differences in areas of the brain that are important in this disorder," said co-principal investigator Sanjiv Kumra, M.D., a psychiatrist at the Zucker Hillside Hospital in Glen Oaks, N.Y.
If DTI brain scanning can be used to diagnose ADHD then that could lower the rate of misdiagnosis and kids wouldn't be given drugs unnecessarily. The treatment of ADHD with stimulant drugs appears to have a beneficial effect on brain development!
In the second study, the researchers found that children who had received stimulant treatment for ADHD had fewer white matter abnormalities than children who did not receive medication.
Patients consisted of two groups, each comprised of 10 children with ADHD. The first group had not taken medication or had been minimally exposed to medications. The second group was exposed to stimulants for an average of 2.5 years. Each of these groups was compared with 10 age- and gender-matched controls. The medicated ADHD children exhibited a normalization effect in fiber pathways of several brain areas.
"The findings from this small, cross-sectional study indicate that the therapeutic effect of stimulants may involve a brain normalization process," Dr. Kumra said.
Between 3 percent and 5 percent of American children are diagnosed with ADHD.
The ability to use DTI to measure abnormalities of brains of children with ADHD will also allow comparison of different ADHD drug treatments to identify treatments that do a better job of reducing the size of the brain abnormalities.
WASHINGTON— Researchers at the Boston Veterans Affairs Health Care System – Brockton Division, Harvard Medical School, and the University of Massachusetts-Boston are using new imaging technology to gather valuable information about the brains of people with schizophrenia. This new variety of magnetic resonance imaging (MRI) is called diffusion tensor imaging (DTI). Using DTI on patients with schizophrenia, neuropsychologists have related smaller sizes in two distinct webs of brain fibers to two distinct types of cognitive malfunction.
The findings appear in the October issue of Neuropsychology, which is published by the American Psychological Association (APA).
Diffusion tensor imaging (DTI) uses a regular MRI machine to analyze the movement of water molecules in and around the fibers that connect different parts of the brain. Neuroscientists use DTI to track indicators of brain “connectivity” – factors such as the number, thickness, density and arrangement of axons (the hair-like extensions of neurons, which send messages to other neurons) and thickness of the insulating/conducting fatty myelin sheath in which they are embedded. If weaker structural integrity reduces connectivity, lead author Paul Nestor, PhD, says it may mean that, “different brain areas do not communicate as well – with less synchrony or harmony, akin to an orchestra or band playing out of synch.”
The researchers conducted neuropsychological tests on 41 patients with schizophrenia and 46 healthy controls, and used DTI scans on a 14-person subset of people with schizophrenia and healthy controls, a sample size typical of seminal studies of the human brain and comparable to early studies using functional MRI.
Brain images from the schizophrenic patients showed abnormalities in two functionally and anatomically different neural pathways – the uncinate fasciculus (UF) and the cingulate bundle (CB). Compared with age-matched controls, patients had smaller UF and CB. These bunches of axons are wrapped in myelin sheaths and bundled like electrical wire. The UF connects different parts of the frontal and temporal lobes and the CB connects parts of the prefrontal-cingulate regions. Each of these fiber tracts may help to define distinct neural networks. “We presume that the health of these fibers reflects the degree to which different parts of the brain are able to communicate,” says Nestor.
It seems reasonable to expect DTI will help to accelerate the development of drugs for schizophrenia as well. Comparison of patient brain scans before and after treatment will provide a way to compare the efficacy of different drugs in reducing brain abnormalities. To repeat a frequent FuturePundit refrain: advances in scientific and medical instrumentation enable the acceleration of advances in science and medical treatment.
|Share |||Randall Parker, 2004 November 30 02:20 PM Brain Disorder Repair|