In selecting sites for a pallidotomy, Dr. Olanow of Mt. Sinai, commented at
the March 7th Symposium that one should look for a teaching institution that
uses microelectrode stimulation. How does microelectrode recording differ
from electrical stimulation? The following article puts it in perspective.
 
Microelectrode vs Electrical Stimulation in Pallidotomies -- Discussion
 
Advanced Treatment for Parkinson's Disease Performed at
                      Boston Hospital
 
BOSTON, Jan. 22, 1996 -- Joining a handful of leading experts nationally,
physicians from Boston's Beth Israel Hospital have performed their first
pallidotomy guided by microelectrode recording on a patient with Parkinson's
disease. The technique promises to be more accurate, more effective, and
safer than the more commonly used "electrical stimulation" pallidotomy.
Pallidotomy guided by microelectrode recording has produced an improvement
in patients' symptoms that is twice as good initially, and about four times
as good after one year, as pallidotomy guided by electrical stimulation.
 
Parkinson's disease, a condition causing uncontrollable shaking and
difficulty in initiating simple body movements, afflicts 500,000 to one
million Americans, including U.S. Attorney General Janet Reno, who recently
announced that she has been diagnosed with early signs of the disease.
 
The goal of both types of pallidotomies is to destroy a pea-sized area in
the brain that is responsible for producing Parkinson's disease symptoms.
Physicians at Beth Israel Hospital used a technique of mapping the brain
area that contains the overactive nerve cells that produce these symptoms.
This is done by recording the activity of individual nerve cells through a
tiny electrical probe called a microelectrode.
 
"By recording the activity of single nerve cells, it is possible to identify
and destroy only the targeted brain area and to distinguish it from
neighboring areas that serve other critical functions. This precision brings
unprecedented accuracy and reduces to a minimum the chances of producing
unwanted damage to the patient," explains Rami Burstein, PhD, the
neurophysiologist who performed the microelectrode recording.
 
While pallidotomy guided by microelectrode recording identifies individual
nerve cells associated with the patient's symptoms, the more commonly used
electrical stimulation approach gives only a rough approximation of the
brain area in which these nerve cells are located. Therefore, procedures
using the more advanced pallidotomy technique are accurate to the thousandth
of a millimeter,
whereas procedures using electrical stimulation have the potential for
missing the mark by several millimeters. Since the target is only four to
six millimeters across, the improved accuracy results in better functional
recovery for the patient.
 
Burstein explains that in electrical stimulation pallidotomy, an electrical
current is delivered in different
brain areas through a stimulation probe. The main use of electrical
stimulation is to find and avoid the borders of the optic tract, which
controls vision, and the internal capsule, which is responsible for movement
on the opposite side of the body. This technique cannot identify the key
site for the pallidotomy directly, but does tell the surgeon when the probe
is too close to the optic tract or the internal capsule. "The problem,
however, is that it is impossible to know in which directions and to what
distance the current spreads," says Burstein. "This introduces uncertainty
as to the location of the probe in relation to the targeted nerve cells, and
thus reduces the level of accuracy."
 
"With the electrical stimulation approach, the surgeon tries to localize the
site in the brain as much as you might try to find your way to the center of
a darkened room by first feeling your way along the walls," explains
Clifford B. Saper, MD, PhD, neurologist-in-chief at Beth Israel Hospital.
 
Patients who benefit most from pallidotomy guided by microelectrode
recording are those with advanced Parkinson's disease. In the early stages
of the disease, medication can be used to control the symptoms. After many
years, however, the medication often ceases to be effective. In addition
to relieving much of the disease's effects, pallidotomy guided by
microelectrode recording also enables the medication once again to regain
effectiveness.
 
"Pallidotomy using microelectrode recording requires state-of-the-art
equipment and techniques normally used in research laboratories. What we
have done here is to bring this technology directly into the operating room
for the benefit of the patient," says David Dubuisson, MD, PhD, the
neurosurgeon who performed the pallidotomy.
 
The new technique of pallidotomy using microelectrode recording of nerve
cells has been performed on about 200 patients across the country to date.
The procedure requires a highly skilled neurophysiologist and a neurosurgeon
with expertise in destroying targeted areas of the brain. Beth
Israel Hospital's interdisciplinary team performing pallidotomies includes
neurosurgeon David Dubuisson, MD, PhD, neurophysiologist Rami Burstein, PhD,
and neurologist-in-chief Clifford Saper, MD, PhD. They join experts at only
a handful of institutions nationally to use this technique
successfully to treat Parkinson's disease.
 
Beth Israel HealthCare is a regional system of care that includes individual
physicians and medical groups, nurses, and other health professionals
associated with Boston's Beth Israel Hospital, a major clinical, teaching,
and research affiliate of Harvard Medical School.
 
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