|
Researchers
Locate Key Area of the Brain Impacted by ADHD
Use New MRI Technique to Measure Ritalin's Effect |
BELMONT, Mass.--(BW HealthWire)--Researchers at
McLean Hospital, using a new brain imaging technique
they developed, have identified a key area of the
brain that is underactive in children with attention
deficit hyperactivity disorder (ADHD). The technique,
a new form of functional magnetic resonance imaging
(fMRI), also enabled the researchers to show how
Ritalin restored function in ADHD children who were
demonstrably hyperactive - that is, children who
had an impaired ability to sit still during a computerized
motion analysis test.
The findings are significant because they provide
further evidence for a biological basis for ADHD
and bring new information to the discussion of Ritalin
use in children and the subjectivity with which
ADHD is diagnosed.
The research team, led by Martin Teicher, MD, PhD,
director of McLean
Hospital's Developmental Biopsychiatry Research
Program, report their findings in the April 2000
issue of Nature Medicine.
ADHD is one of the most commonly diagnosed psychiatric
disorders in children. Clinical hallmarks of ADHD
are hyperactivity, inattention and impulsivity.
The McLean study involved six healthy boys with
no history of ADHD or psychiatric disorders, and
11 boys diagnosed with ADHD according to the standard
DSM-IV criteria. All 17 boys also were given a computer
test that uses an infrared motion analysis system
to objectively measure activity, movement and attention.
Six of the 11 boys who met DSM-IV criteria for ADHD
were also confirmed to be hyperactive by the objective
computer test.
Using their new fMRI technique, Teicher and his
colleagues identified one area of the brain--the
putamen--to which ADHD symptoms may be closely tied.
Long-believed to be important in motor function
and some aspects of attention, the putamen was shown
to have diminished blood flow in the children with
ADHD. Further, the researchers found, the more objectively
hyperactive or inattentive the children were, the
greater was their impairment in blood flow to the
putamen.
For the six ADHD boys who tested objectively hyperactive,
the researchers found that use of Ritalin enhanced
blood flow significantly in the putamen. However,
conversely, for the five ADHD boys who were not
objectively hyperactive, Ritalin decreased blood
flow in the putamen even further.
``This study supports other research that points
to the putamen as an important region of the brain
involved in ADHD, and that diminished blood flow
in the putamen may be another way to objectively
diagnose ADHD,'' said Teicher. ``It also shows that
Ritalin may not be effective for all children diagnosed
with ADHD using only DSM-IV criteria. These criteria
identify a mixed group of children with
similar behavioral problems, some of whom have an
identifiable neurobiological abnormality and a deficient
capacity to sit still and pay attention. But the
DSM-IV criteria are broad and seem to include children
with similar behavioral problems that may arise
for other reasons.''
The 11 ADHD boys were treated one week at a time
with randomly low, medium and high doses of Ritalin
and placebo, and were scanned on each dose. The
six healthy boys were not medicated and scanned
only once. The new fMRI test, unlike conventional
MRI, enabled investigators for the first time ever
to study brain blood flow at rest in the boys while
on Ritalin and on placebo, thus allowing them
to see which area of the brain the medication was
targeting and whether or not it was working.
``Many children have the capacity to sit still
but do not utilize that capacity. Using our new
technique, we found that children who tested objectively
hyperactive had a physiological reason for not sitting
still and that they are the ones who may receive
the greatest benefit from Ritalin,'' said Teicher.
Study coauthors are Carl Anderson, PhD; Ann Polcari,
RN; Carol Glod, PhD, and Perry Renshaw, MD, PhD,
all of McLean Hospital; and Luis Maas, MD, of McLean
Hospital and the Harvard-MIT Division of Health
Sciences and Technology.
The study was funded by the National Institute
of Mental Health and the National Institute for
Drug Abuse. McLean Hospital is the largest psychiatric
teaching affiliate of Harvard Medical School, an
affiliate of Massachusetts General Hospital and
a member of Partners HealthCare System.
|
