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Research Highlights
A new approach to detecting mild brain injuries
September 8, 2008
Traumatic brain injury (TBI)—even
when it is relatively mild—can have
all the subtlety of a wrecking ball in terms
of how it affects the lives of veterans and
their families. But when it comes to
diagnosis, mild TBI is subtle—to the point
where it often can’t be detected through
conventional brain scans.
Mingxiong Huang, PhD, and Roland
Lee, MD, of VA and the University of
California, San Diego (UCSD), are among
several VA scientists searching for a better
way. With collaborators at UCSD and the
Marines' Camp Pendleton, Huang and Lee
are exploring whether newer brain scanning
methods can detect injuries missed through
ordinary MRI or CT scans. Their study will
involve up to 150 veterans and military
personnel.
One of the technologies being used is
MEG, short for magnetoencephalography.
A MEG scanner resembles a giant salon
hair dryer. It records electromagnetic
signals given off by brain cells as they
"talk" with each other. The biggest plus of
MEG relative to other scanning
technologies is its speed: It captures bursts
of neuronal cross-talk that last only a few
milliseconds. (Think of the time it takes
between seeing a red light and stepping on
the brake pedal.) Other imaging methods
that show brain activity, such as functional
MRI or PET scans, have their own
advantages but are far slower. Also, data
from MEG scans can be overlaid on a map
of the brain, and abnormalities—even
subtle ones—can be visualized as patches
of color, indicating precisely which areas of
the brain may be damaged.
According to Huang, injured brains
generate pathological low-frequency brain
waves—like those seen in normal patients
during deep, dreamless sleep. He believes
the reason may be that damaged neurons
become like frayed wires, unable to conduct
impulses efficiently. MEG’s ability to
noninvasively measure and "localize" these
abnormalities, he says, may be critical in
diagnosing brain injuries.
The costar in Huang and Lee’s vision is
DTI, or diffusion tensor imaging. A
relatively new form of MRI, this method
records how water molecules move, or
diffuse, through the nerve fibers that make
up the brain’s white matter. These fibers link
different regions of the brain, like the cables
connecting computers on a network.
Problems in the white matter—for example,
nerve fibers that are not bundled together
coherently or that have lost their fatty
"myelin" coating—show up in DTI scans
but not in regular MRI scans.
Huang says he hopes to eventually
incorporate a third imaging technique,
chemical shift imaging (CSI), also called
MR spectroscopy imaging. This method
reveals the distribution of certain chemicals
in the brain—another potential marker for
subtle brain injury.
"The measurements of neuronal
electromagnetic signals using MEG, the
diffusion property of the white matter fiber
tracts using DTI, and metabolic information
using CSI should provide a comprehensive
picture of TBI," says Huang. "All of these
imaging modalities are non-invasive and
can be performed multiple times" over a
long-term study. He notes that in addition to
aiding diagnosis, they may be helpful in
evaluating the effects of new TBI
medications or other treatments.
This article originally appeared in the September 2008 issue of VA Research Currents.
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