New MRI Technique Detects Subtle But Serious Brain Injury
ScienceDaily (May 13, 2008) - A new technique for analyzing magnetic
resonance
imaging data, developed by researchers at UT Southwestern Medical
Center, can
reveal serious brain injury missed by current tests and help predict a
patient's
degree of recovery.

In brain injuries sustained when the head suddenly stops moving -
during a motor
vehicle accident, for instance - the force can shear and damage nerve
cells.
This kind of injury does not show up on computerized tomography scans,
the
researchers said, and magnetic resonance imaging does not yet reliably
detect
this type of injury.

"This is a new way of measuring a common injury that has been
overlooked," said
Dr. Ramón Díaz-Arrastia, professor of neurology and senior author of
the paper,
which appears in the May issue of the journal Archives of Neurology.

"No matter how many seat belts and airbags there are, if you hit a
tree at 50
miles an hour, you're going to have this kind of injury," Dr. Díaz-
Arrastia
said. "It may account for up to half of the traumatic brain injuries
from car
accidents."

The injury typically affects the portions of nerve cells in the brain
called the
axons, the long, thin extensions of nerve cells that reach from one
area to
another. When the brain is subjected to powerful, inertial forces,
axons can be
deformed and damaged. This type of trauma, called diffuse axonal
injury, or DAI,
is often difficult to diagnose, Dr. Díaz-Arrastia said.

In the study, the researchers performed MRI analysis on 12 people,
ranging in
age from 16 to 37, who had severe closed-head brain injury, who were
either able
to give consent or whose legal guardians gave consent.

From the patients' point of view, the test was the same as undergoing
an
ordinary MRI. The difference was that the researchers used a new
mathematical
analysis, called diffusion tensor tractography, to detect diffuse
axonal injury.
They also analyzed the MRI data using an existing method called FLAIR,
for fluid
attenuation and inversion recovery.

The new analysis tested for how easily water could move around in the
brain in
the areas surrounding cells. When the axons are damaged, they swell,
absorbing
the water around them and leaving less that can move around between
cells. As
the axons die, they release the water, resulting in more water
surrounding the
cells.

By comparing multiple MRI images over time, the researchers could
detect this
change in water motion. Their analysis focused on three areas of the
brain - the
corpus callosum, the fornix and the peduncular projections - that
consist
largely of axons that project from one part of the brain to another.

The researchers tested the patients' degree of consciousness and
ability to care
for themselves immediately after their injuries, as well as six to 11
months
later. One patient died, and one had fully recovered, with the rest
showing
partial recovery. One patient could not be located for the follow-up.

In most of the brain areas studied, the degree of diffuse axonal
injury, which
is reflected by a reduction of the motion of water around the never
cells, was
significantly linked to how much the patients improved over time, the
researchers found. In contrast, FLAIR analysis did not show a
statistically
significant link with the degree of recovery.

Further studies are under way to include more patients, which will
provide more
power to the analysis. The researchers will also study other areas of
the brain
that are at risk for diffuse axonal injury to see whether MRI analysis
can be
useful in those regions as well.

Other UT Southwestern researchers involved in the study were Dr.
Michael Devous,
professor of radiology; Dr. Roddy McColl, associate professor of
radiology; Dr.
Christopher Madden, assistant professor of neurological surgery; Dr.
Carlos
Marquez de la Plata, assistant professor of psychiatry; Drs. Anthony
Whittemore
and Evelyn Babcock, both assistant professors of radiology; Carol
Moore and Kan
Ding, both clinical research coordinators in neurology; and medical
students
Tiffany Rickbeil, Julia Dobervich, David Kroll, Bao Dao and Nisha
Mohindra.

Lead author Jun-Yi Wang; Dr. Khamid Bakhadirov; and Dr. Herve Abdi
from the
department of cognition and neuroscience at UT Dallas also
participated in the
study.

The work was supported by the National Institute on Disability and
Rehabilitation Research and the National Institutes of Health.


----------------------------------------------------------------------------Adapted from materials provided by UT Southwestern Medical Center.
UT Southwestern Medical Center (2008, May 13). New MRI Technique
Detects Subtle
But Serious Brain Injury. ScienceDaily. Retrieved May 13, 2008, from
http://www.sciencedaily.com/releases/2008/05/080512163852.htm