Deep
brain stimulation in Parkinson Disease reduces uncontrolled
movements
Deep brain stimulation of two
different areas of the brain appears to improve problems with
uncontrolled movements (dyskinesia) in patients with Parkinson
disease (PD), according to an article in the April issue of
Archives of Neurology, one of the JAMA/Archives journals.
Deep brain stimulation with
electrical impulses delivered to structures deep within the brain is
being intensively investigated for the management of advanced
Parkinson disease, according to background information in the
article. Although a number of studies have shown that stimulation of
two different areas of the brain, the globus pallidus interna (GPi)
and the subthalmic nucleus (STN), can be achieved safely and
effectively, STN has been thought to be the preferred target. At the
same time, the authors note, there does seem to be some evidence
that the STN is more vulnerable during surgery and that STN patients
may have more postoperative problems.
Valerie C. Anderson, Ph.D., of the
Oregon Health and Science University, Portland, and colleagues
compared 23 patients with Parkinson disease and problems with
medication-induced uncontrolled movement who were randomly assigned
to implantation of deep brain stimulators in either the GPi or the
STN areas of the brain. Patients’ Parkinson symptoms were evaluated
with and without medication using a standard rating scale at three,
six and 12 months after surgery.
“Off-medication Unified
Parkinson’s Disease Rating Scale motor scores were improved after 12
months of both GPi and STN stimulation (39 vs 48 percent),” the
authors write. “Bradykinesia [extremely slow movement] tended to
improve more with STN than GPi stimulation. No improvement in
on-medication function was observed in either group. Levodopa
[Parkinson medication] dose was reduced by 38 percent in STN
stimulation patients compared with three percent in GPi stimulation
patients. … Dyskinesia was reduced by stimulation at both GPi and
STN ( 89 v 62 percent). Cognitive and behavioral complications were
observed only in combination with STN stimulation.”
“At this point, it appears that
stimulation at either STN or GPi improves off-medication motor
scores and levodopa-induced dyskinesia for at least one year, and
there is no clear superiority of STN over GPi stimulation,” the
authors conclude. “Indeed, our comparison of GPi vs STN stimulation
suggests that selection of a stimulation site should be influenced
by symptom profile. Although GPi stimulation may be better for the
patient with dose-limiting dyskinesia, STN stimulation may be better
for the younger patient with prominent bradykinesia.”
Editor’s Note: This study was
supported in part by a grant from the Public Health Service.
Editorial: Will Pallidal Deep
Brain Stimulation Make a Triumphant Return?
In an editorial accompanying this
study, Michael S. Okun, M.D., and Kelly D. Foote, M.D., of the
University of Florida, Gainesville, write, “Dyskinesia improves
dramatically with both GPi and STN DBS [deep brain stimulation]. As
suggested by the authors of this article and by others, the
mechanism underlying this improvement may be different for each
target. The majority of the anti-dyskinetic benefit of GPi DBS may
be due to active stimulation, and the benefits in STN may be
primarily a result of medication reduction. … the antidyskinetic
effects of GPi DBS seem to be greater than those of STN DBS.”
“One important and perhaps
deciding factor in the rematch between GPi and STN DBS will be the
incidence of surgical and postoperative complications,” the authors
suggest. “Assuming that the rates of the procedure-related and
device complications are equal, then long-term cognitive, mood, and
behavioral problems may lead to a victory of one target over the
other.”
“The unanswered questions
regarding target selection will require several more head-to-head
rematches between GPi and STN,” the authors conclude. “Future
improvements in implantation technique and in lead design may also
enhance the benefit in each target. Studies may prove that STN is a
better target than GPi or that there is no clear winner. Studies may
also prove that STN is superior for certain features of the disease
such as tremor, bradykinesia, and medication reduction.
Alternatively, studies may show that GPi is equal to STN with regard
to motor improvements, and is better antidyskinesia treatment, but
has fewer cognitive, mood, and behavioral adverse effects. Whatever
the outcome of these rematches, we should be open to changes in our
current practices and recognize the possibility that we should match
individual patient needs with the strengths and weaknesses of
individual targets.”
Deep
brain stimulation in Parkinson Disease reduces uncontrolled
movements