Treating Parkinson Disease with surgery was once a common practice.
But after the discovery of levodopa, surgery was restricted to only a few
cases. Studies in the past few decades have led to great improvements in
surgical techniques, and surgery is again being used in people with advanced
Parkinson Disease for whom drug therapy is no longer sufficient.
Pallidotomy and Thalamotomy. The
earliest types of surgery for Parkinson Disease involved selectively destroying specific
parts of the brain that contribute to the symptoms of the disease.
Investigators have now greatly refined the use of these procedures. The
most common of these procedures is called pallidotomy. In this
procedure, a surgeon selectively destroys a portion of the brain called the
globus pallidus. Pallidotomy can improve symptoms of tremor, rigidity, and
bradykinesia, possibly by interrupting the connections between the globus
pallidus and the striatum or thalamus. Some studies have also found that
pallidotomy can improve gait and balance and reduce the amount of levodopa
patients require, thus reducing drug-induced dyskinesias and dystonia. A
related procedure, called thalamotomy, involves surgically destroying
part of the brain's thalamus. Thalamotomy is useful primarily to reduce
tremor.
Because these procedures cause permanent destruction of
brain tissue, they have largely been replaced by deep brain stimulation
for treatment of Parkinson Disease.
Deep Brain Stimulation. Deep brain
stimulation, or DBS, uses an electrode surgically implanted into part of the
brain. The electrodes are connected by a wire under the skin to a small
electrical device called a pulse generator that is implanted in the chest
beneath the collarbone. The pulse generator and electrodes painlessly
stimulate the brain in a way that helps to stop many of the symptoms of
Parkinson Disease.
DBS has now been approved by the U.S. Food and Drug Administration, and it
is widely used as a treatment for Parkinson Disease.
DBS can be used on one or both sides of the brain. If
it is used on just one side, it will affect symptoms on the opposite side of
the body. DBS is primarily used to stimulate one of three brain regions:
the subthalamic nucleus, the globus pallidus, or the thalamus. However, the
subthalamic nucleus, a tiny area located beneath the thalamus, is the most
common target. Stimulation of either the globus pallidus or the subthalamic
nucleus can reduce tremor, bradykinesia, and rigidity. Stimulation of the
thalamus is useful primarily for reducing tremor.
DBS usually reduces the need for levodopa and related
drugs, which in turn decreases dyskinesias. It also helps to relieve on-off
fluctuation of symptoms. People who initially responded well to treatment
with levodopa tend to respond well to DBS. While the benefits of DBS can be
substantial, it usually does not help with speech problems, "freezing,"
posture, balance, anxiety, depression, or dementia.
One advantage of DBS compared to pallidotomy and
thalamotomy is that the electrical current can be turned off using a
handheld device. The pulse generator also can be externally programmed.
Patients must return to the medical center frequently
for several months after DBS surgery in order to have the stimulation
adjusted by trained doctors or other medical professionals. The pulse
generator must be programmed very carefully to give the best results.
Doctors also must supervise reductions in patients' medications. After a
few months, the number of medical visits usually decreases significantly,
though patients may occasionally need to return to the center to have their
stimulator checked. Also, the battery for the pulse generator must be
surgically replaced every three to five years, though externally
rechargeable batteries may eventually become available. Long-term results of
DBS are still being determined. DBS does not stop Parkinson Disease from progressing, and
some problems may gradually return. However, studies up to several years
after surgery have shown that many people's symptoms remain significantly
better than they were before DBS.
DBS is not a good solution for everyone. It is
generally used only in people with advanced, levodopa-responsive Parkinson
Disease who have
developed dyskinesias or other disabling "off" symptoms despite drug therapy.
It is not normally used in people with memory problems, hallucinations, a
poor response to levodopa, severe depression, or poor health. DBS generally
does not help people with "atypical" parkinsonian syndromes such as multiple
system atrophy, progressive supranuclear palsy, or post-traumatic
parkinsonism. Younger people generally do better than older people after
DBS, but healthy older people can undergo DBS and they may benefit a great
deal.
As with any brain surgery, DBS has potential
complications, including stroke or brain hemorrhage. These complications
are rare, however. There is also a risk of infection, which may require
antibiotics or even replacement of parts of the DBS system. The stimulator
may sometimes cause speech problems, balance problems, or even dyskinesias.
However, those problems are often reversible if the stimulation is modified.
Researchers are continuing to study DBS and to develop
ways of improving it. They are conducting clinical studies to determine the
best part of the brain to receive stimulation and to determine the long-term
effects of this therapy. They also are working to improve the technology
used in DBS.
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