Advanced MRI scans may help treat essential tremors and Parkinson's disease
Researchers at UT
Southwestern Medical Center have recently developed MRI techniques used
to more precisely target a small area in the brain linked to Parkinson's
disease and essential tremor. This may lead to better outcomes without
surgery and with less risk of negative effects of treatment of tremors
and Parkinson's disease.
The study have been published in the journal Brain.
The research describes recently refined MRI methods designed to allow
neuroradiologists to zero in on a pea-sized region in the brain's
thalamus involved in movement. Using the images, doctors then can use
high-intensity focused ultrasound (HIFU) to ablate, or burn away,
problem tissue, says Bhavya R. Shah, M.D., first author of the study and
an assistant professor of radiology and neurological surgery at UT
Southwestern's Peter O'Donnell Jr. Brain Institute.
"The benefit for
patients is that we will be better able to target the brain structures
that we want," Shah says. "And because we're not hitting the wrong
target, we'll have fewer adverse effects." The procedures are already
Food and Drug Administration-approved for use in patients, and UTSW
plans to begin employing them to treat patients when its Neuro High
Intensity Focused Ultrasound Program opens this fall.
Adverse effects from
imprecise targeting include problems walking or slurring words. While
such effects are usually temporary, they can be permanent in 15 to 20
percent of cases, says Dr. Shah.
According to the National Institutes of Health, essential tremor affects
up to 10 million Americans and Parkinson's disease impacts more than 1
million. Both are neurologic diseases thought to have genetic links. The
first line of treatment for the involuntary trembling or shaking seen
with these diseases is medication. However, approximately 30 percent of
patients do not respond well to drugs, according to the study.
In the late 1990s,
neurosurgeons began using a procedure called deep brain stimulation,
opening the skull to permanently implant metal electrodes that could
then be stimulated via a battery pack.
About a decade ago, a new MRI-guided procedure emerged that uses
high-intensity ultrasound waves to heat and eliminate a small section of
the thalamus linked to the disorders. MRI-guided HIFU is currently
approved for treatment of essential tremor and tremors seen in
Parkinson's disease patients. The outpatient procedure does not require
opening the skull, and the patient is awake while it is performed, says
Dr. Shah. "No cuts. No anesthesia. No implanted devices."
A challenge in both
procedures has been locating the precise area inside the brain's
thalamus to treat - the pea-sized ventral intermediate nucleus, says Dr.
Shah.
Traditionally, doctors have relied on either landmarks or maps of the
brain drawn from cadavers to help them pinpoint the correct location.
However, every brain is different, Dr. Shah says, and tiny errors can
lead to damage in surrounding tissue, or to missing portions of the
correct target.
Three newly refined MRI
techniques are better at delineating the target tissue, according to
the study.
The most widely studied and perhaps most promising imaging method is
called diffusion tractography, says Dr. Shah. It creates precise brain
images by taking into account the natural water movement within tissues.
The other methods described are quantitative susceptibility mapping -
which creates contrast in the image by detecting distortions in the
magnetic field caused by substances such as iron or blood - and fast
gray matter acquisition TI inversion recovery - which operates much like
a photo negative, turning the brain's white matter dark and its gray
matter white in order to provide greater detail in the gray matter.
Dr. Shah and his team
plan to participate in a multicenter clinical trial with collaborators
at the Mayo Clinic in Rochester, Minnesota, testing the diffusion
tractography method in patients.
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