Oct. 1, 2014
Over
the past several decades, brain stimulation has become an increasingly
important treatment option for a number of psychiatric and neurological
conditions.
Divided
into two broad approaches, invasive and noninvasive, brain stimulation works by
targeting specific sites to adjust brain activity. The most widely known
invasive technique, deep brain stimulation (DBS), requires brain surgery to
insert an electrode and is approved by the U.S. Food and Drug Administration
(FDA) for the treatment of Parkinson's disease and essential tremor. Noninvasive techniques,
including transcranial magnetic stimulation (TMS), can be administered from
outside the head and are currently approved for the treatment of depression. Brain stimulation can result in
dramatic benefit to patients with these disorders, motivating researchers to
test whether it can also help patients with other diseases.
But,
in many cases, the ideal sites to administer stimulation have remained
ambiguous. Exactly where in the brain is the best spot to stimulate to treat a
given patient or a given disease?
Now
a new study in the Proceedings of the National Academy of Sciences (PNAS)
helps answer this question. Led by investigators at Beth Israel Deaconess
Medical Center (BIDMC), the findings suggest that brain networks - the interconnected
pathways that link brain circuits to one another - can help guide site
selection for brain stimulation therapies.
"Although
different types of brain stimulation are currently applied in different
locations, we found that the targets used to treat the same disease are nodes
in the same connected brain network," says first author Michael D. Fox,
MD, PhD, an investigator in the Berenson-Allen Center for Noninvasive Brain
Stimulation and in the Parkinson's Disease and Movement Disorders Center at
BIDMC.
"This
may have implications for how we administer brain stimulation to treat disease.
If you want to treat Parkinson's disease or tremor with brain stimulation, you
can insert an electrode deep in the brain and get a great effect. However,
getting this same benefit with noninvasive stimulation is difficult, as you
can't directly stimulate the same site deep in the brain from outside the
head," explains Fox, an Assistant Professor of Neurology at Harvard
Medical School (HMS). "But, by looking at the brain's own network
connectivity, we can identify sites on the surface of the brain that connect
with this deep site, and stimulate those sites noninvasively."
Brain
networks consist of interconnected pathways linking brain circuits or loops,
similar to a college campus in which paved sidewalks connect a wide variety of
buildings.
In
this paper, Fox led a team that first conducted a large-scale literature search
to identify all neurological and psychiatric diseases where improvement had
been seen with both invasive and noninvasive brain stimulation. Their analysis
revealed 14 conditions: addiction,
Alzheimer's disease, anorexia, depression, dystonia, epilepsy, essential tremor, gait
dysfunction, Huntington's disease, minimally conscious
state, obsessive compulsive disorder, pain,
Parkinson disease and Tourette syndrome. They next listed the stimulation
sites, either deep in the brain or on the surface of the brain, thought to be
effective for the treatment of each of the 14 diseases.
"We
wanted to test the hypothesis that these various stimulation sites are actually
different spots within the same brain network," explains Fox. "To
examine the connectivity from any one site to other brain regions, we used a
data base of functional MRI images and a technique that enables you
to see correlations in spontaneous brain activity." From these
correlations, the investigators were able to create a map of connections from
deep brain stimulation sites to the surface of the brain. When they compared
this map to sites on the brain surface that work for noninvasive brain
stimulation, the two matched.
"These
results suggest that brain networks might be used to help us better understand
why brain stimulation works and to improve therapy by identifying the best
place to stimulate the brain for each individual patient and given
disease," says senior author Alvaro Pascual-Leone, MD, PhD, the Director
of the Berenson-Allen Center for Noninvasive Brain Stimulation at BIDMC and
Professor of Neurology at HMS. "This study illustrates the potential of
gaining fundamental insights into brain function while helping patients with
debilitating diseases, and provides us with a powerful way of selecting targets
based on their connectivity to other regions that can be widely applied to help
guide brain stimulation therapy across multiple neurological and psychiatric
disorders."
"As
we're trying different types of brain stimulation for different diseases, the
question comes up, 'How does one relate to the other'?" notes Fox.
"In other words, can we use the success in one to help design a trial or
inform how we apply a new type of brain stimulation? Our new findings suggest
that resting-state functional connectivity may be useful for translating
therapy between treatment modalities, optimizing treatment and identifying new
stimulation targets."
http://www.medicalnewstoday.com/releases/283202.php
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