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Index
Parkinson's Disease (PD) is a progressive neurological disorder caused by a loss of nerve cells in the substantia nigra, a small area deep within the brainstem. The cells that die are inhibitory to other cells in the brain. So over activity of neurons is actually the characteristic that makes Parkinson’s Disease amenable to neurosurgical treatments which kill cells or otherwise lessen their activity. In most cases, the cause of PD is unknown although Parkinson's-like conditions can be seen after stroke, encephalitis, carbon monoxide or manganese poisoning and head trauma. The onset is usually insidious and occurs in most patients in their 50's and 60's.
The major manifestations of the disease are resting tremor, rigidity, bradykinesia [slowness of movements] and hypokinesia [difficulty initiating movements]. Some people also experience extra-involuntary movements, called dyskinesias, as a side effect of the drugs used to treat Parkinson’s Disease. Gait disturbance (shuffling gait) is also often a prominent symptom of Parkinson's Disease. Parkinson’s disease is often well controlled by medications, especially those containing L-DOPA (Sinemet).
Although this discussion centers on Parkinson’s Disease, much of it is also applicable to other movement disorders such as essential tremor (also called benign tremor or familial tremor), dystonia, spasmodic torticollis, post-stroke tremor, multiple sclerosis tremor, or post-traumatic tremor. Instead of the three possible targets for surgery as in Parkinson’s Disease only one of the targets (the thalamus) is currently considered effective for the other causes of tremor.
Similarly many patients with Parkinson's Disease experience excess movements or postures
at times. These are called dyskinesia and dystonia, respectively. Surgical treatments for tremor, dyskinesia, and
dystonia whatever the cause overlap significantly with those for Parkinson's Disease. Parkinson’s Disease, dyskinesia,
dystonia, and tremor are diseases are that collectively fall into the category "movement disorders."
In the early 1900s, before the advent of modern anti-Parkinsonian drugs, surgical treatment of Parkinson's Disease and other movement disorders was common. A variety of operations aimed at destroying certain areas of the brain were carried out in an attempt to relieve severe tremor and rigidity. In 1947, special stereotactic techniques were introduced which allowed for safer, more precise surgical treatment and many deep brain structures within the basal ganglia were targeted with varied degrees of success. Pallidotomy was introduced in 1952 by Dr. Lars Leksell and was successful in relieving many Parkinsonian symptoms in patients.
At the same time, many surgeons were performing surgery on the thalamus and for a variety of reasons, thalamotomy became widely accepted, replacing pallidotomy as the surgical treatment of choice for Parkinson's Disease. Thalamotomy, which has an excellent effect on the tremor, is not as effective at reducing rigidity, bradykinesia, or hypokinesia. In addition, bradykinesia can be aggravated by the procedure.
In 1985 Dr. Lauri Laitinen, who had worked with Leksell in Sweden, re-introduced the pallidotomy,
as a treatment for patients who had previously undergone thalamotomy but remained symptomatic. Many of his patients
suffered from severe bradykinesia, rigidity, tremor and other unusual involuntary movements. These patients had
long standing, severe PD that had been treated with medications for many years and exhibited what is known as drug-induced
dyskinesia. He reported his first pallidotomy series of 38 patients in January of 1992 and found that 80-90% of
patients had a long lasting relief of symptoms. The rate of control of tremor is somewhat lower, while chance of
eliminating dyskinesias is even higher. This encouraging experience prompted other specialists to re-examine the
role of pallidotomy in PD and several centers in the United States currently carry out the Laitinen pallidotomy
procedure.
Pallidotomy has also been found to be effective for some patients with a handful of other movement disorders known
collectively as dystonias. The "mildest" forms of dystonia are writers cramp and spasmodic torticollis.
More severe is idiopathic hemidystonia. Familial dystonias are usually the most disabling forms of dystonia. All
have been observed to respond to globus pallidus surgery.
In 1997 the most important procedure to treat the tremor of Parkinson's Disease and essential
tremor received approval from the U.S. Food and Drug Administration (FDA), namely stereotactic insertion of a deep
brain stimulator into the thalamus. In January 2002 the FDA approved bilateral subthalamic nucleus and globus pallidus
deep brain stimulators to treat other movement symptoms of Parkinson's disease including rigidity, bradykinesia
[slowness of movement], tremor, and freezing. Bilateral Subthalamic nucleus (STN)
Bilateral Globus pallidus (GPi)
Thlamus (VIM or VPL)
Deep brain stimulation has the advantage that instead of destroying the overactive cells that cause symptoms in
Parkinson's disease it instead temporarily disables them by firing rapid pulses of electricity between four electrodes
at the tip of the lead. The lead is permanently implanted and connected to a pacemaker controller installed underneath
the skin of the chest.
Deep brain stimulators are also under investigation for control of dyskinesia and dystonia, whether related to
Parkinson's Disease or not. The globus pallidus appears to be the most promising target for these potential indications.
DBS Target
Likely symptomatic benefit
An alternative to making a lesion with an electrode is to use highly focused radiation. The advantage of this technique is that there is no need for an incision. Two types of devices can be used to deliver stereotactic radiosurgery here at the Wake Forest University Baptist Medical Center, namely the Gamma Knife and the LINAC-Scalpel.
The disadvantage of radiosurgery for movement disorders is that it is not possible to make
a test lesion or to change the position of the lesion after this position is computed from the scans. For this
reason the success rate of radiosurgical thalamotomy or subthalamic nucleus lesioning is probably lower than that
of the more traditional procedures. Stereotactic radiosurgery has been used for years to treat tumors and experience
for this indication leads to the prediction that the hemorrhage rate of radiosurgical lesioning is likely to be
lower than that for conventional procedures. Nonetheless, neurologic complications may arise from direct injury
caused by the radiation or from a syndrome known as radiation necrosis. In fact, complication rates for radiosurgical
pallidotomy appear to be higher than those for radiofrequency (Laitinen) pallidotomy.
The possibility of reconstituting damaged pathways rather than inactivating overactive downstream
neurons has long been appealing. Unfortunately the potential benefits of this approach are yet to be realized in
practice. In fact, the preliminary results from a randomized trial of fetal cell transplantation for Parkinson's
Disease showed no benefit overall. There was improvement in rigidity and slowness of movement in some patients
under 60 years of age. Unfortunately, side effects included significant worsening of dyskinesias. There was no
benefit in patients over 60 years old.
|
Target for Intervention |
|||
| Intervention type: |
Thalamus (v.i.m. nucleus) |
Globus pallidus (ventrolateral GPi) |
Subthalamic nucleus |
|
Lesioning = "otomy" (with a radiofrequency electrode) |
Thalamotomy: Procedure for tremor sometimes favored in young people with tremor on only one side | Pallidotomy: Classic procedure for PD. Being replaced by DBS because of its lower complication rates. |
Subthalamic nucleus radiofrequency lesioning: A new procedure for PD not generally performed in the US |
|
Deep brain stimulator (DBS) |
DBS in the thalamus on one or both sides is the favored procedure for most people with disabling tremor. | Bilateral DBS has proven benefit at this target but is not as successful at reducing freezing or lowering medication requirements as deep brain stimulation of STN for PD | Bilateral STN DBS is frequently the procedure of choice for PD. |
|
Stereotactic Radiosurgery (non-invasive lesioning) |
Radiosurgery uses radiation to create a lesion. Since the current success rate is lower than that for the procedures above and complication rates are as high or higher it is usually reserved for those with medical problems that prevent them from having direct surgical procedures. | ||
There are three different types of procedures and three different targets. It is
often best to make the final decision about which target or combination of targets is best in the operating room
during surgery based on the response to test stimulation.
The appropriate selection of people affected by movement disorders for surgical treatment
implies a thorough pre-surgical evaluation. In particular, because of the risks of the surgical procedure patients
who are well controlled by medications are usually advised against surgery. Preoperative evaluation, therefore,
includes a detailed history and physical examination. Videotaping of the patient's preoperative condition can also
be helpful. This preoperative evaluation is important to ensure that the patient is a good candidate for surgical
intervention and understands the risks and potential benefits of the procedure. Many of these scales and tests
also may be performed post-operatively, to assess the results of surgery in an objective fashion.
Deciding among the various available procedures is often best made during the operation where several different
targets can be tested in the hope of optimizing the benefit.
Stereotactic neurosurgery is not without certain risks although major morbidity and mortality
is relatively low at approximately 0.5-5%. The most feared problems are most often the result of hemorrhage (bleeding)
and may be thought of as being the equivalent of a stroke. The lower rates of hemorrhage have been reported among
centers that do not use microelectrode recording for intraoperative localization. The range of deficits and the
potential for recovery in these instances is similar to that for other causes of intracranial hemorrhage or stroke.
Although the surgery is not thought of as one of the most physiologically stressful patients have the risks of
those in their age group and health status for other complications such as those involving the heart, blood vessels,
and lungs.
One side effect of pallidotomy has been a contra-lateral visual field defect seen in approximately 7-10% of patients
who do not have microelectrode recording performed and a smaller percentage among those that do have microelectrode
recording intraoperatively. This visual field defect or scotoma creates a blind spot in the lower visual field
and if this occurs on the left side it is generally well tolerated, but on the right side it may disturb reading.
Other side affects of neurosurgery for Parkinson's Disease can relate to weakness or coordination and these often
improve over time. Some patients report personality or cognitive changes after the procedure but most do not. For
procedures in the thalamus, a difficulty with speech called dysarthria can occur. This is especially common with
bilateral thalamotomies for tremor but is not a common permanent effect of deep brain stimulators. The incidence
of these side effect and other potential side effects are minimized by intraoperative physiologic testing during
the procedure.
Because a deep brain stimulator is not part of the body there is always a chance that it could become infected
by bacteria and need to be removed.
Surgery for Parkinson's Disease does not benefit symptoms that are not directly caused by the death of cells in
the substantia nigra. Thus only movement symtpoms can be expected to benefit. In additon the procedures have been
optimized for arm and leg movement so speech is rarely improved by surgery. Although freezing is frequently improved
by subthalamic nucleus DBS balance is usually not. Therefore, falls are often not reduced by any surgery and may
even be increased by surgery for movement disorders. In addition, there is no known benefit to memory problems,
depression, drooling, constipation, or urinary problems. Restless legs are also benefited only variably.
Similar limitations apply with respect to thalamotomy or deep brain stimulators for tremor. These procedures have
been optimized to reduce arm tremor. There are somewhat less effective for leg tremor and significantly less effective
for head and voice tremor. Although bilateral thalamic DBS often does help voice and head tremor.
In fact, it should be remembered that although surgery is often gratifyingly successful at improving quality of
life in those experiencing movement disorders, there is no guarantee of functionally significant improvement in
any area.
Since the risks of surgery are significant even if statistically moderate, surgery is only recommended for patients
whose quality of life is significantly impaired by their movement disorder. The determination of what constitutes
significant impairment is best made by the affected individual with the input of their physician's and loved ones.
Stereotactic lesioning or insertion of a deep brain stimulator is usually only mildly painful. The surgical target is defined by a CT and/or MRI scan carried out with a special stereotactic frame attached to the head. Once the appropriate target coordinates have been selected on a computer work station, the patient is taken back to the operating room for the surgical procedure itself. A patch of hair is shaved and the surgery is then carried out with local anesthesia. A 3-4 cm (1-2 inch) skin incision is made in the scalp after infiltration with local anesthesia and a burr hole is drilled through the skull.
For lesioning an insulated stimulating electrode is then introduced into the target. The target area is stimulated with very small electrical impulses which may give rise to a variety of different reactions. The purpose of the stimulation is to make sure that the probe lies in the correct position in the brain. With electrical stimulation, tremor and rigidity can be reduced almost immediately in the operating room and this confirms accurate placement of the electrode tip. Electrical stimulation may also give rise to visual, motor, sensory or other untoward symptoms and this would indicate that the probe may need repositioning. If symptoms occur even after repositioning, there is a risk that the surgery cannot be performed safely and the probe would be removed without actual creation of the lesion.
When the intraoperative stimulation indicates that the tip of the electrode lies in the optimal location, a temporary (nonpermanent) lesion is first made. This allows for detailed testing of the patient intraoperatively to insure that no neurologic deficit will be incurred with creation of a permanent lesion. It also will allow for assessment of beneficial effect on tremor, rigidity and bradykinesia. If all of these conditions are met, then a permanent lesion is created at the target site. During the lesioning, the patient will be given a variety of motor, visual and psychological tests to check that no adverse effects develop. If unexpected reactions are observed, further lesioning is stopped immediately. It should be noted that none of the stimulation or lesioning is painful for most people.
If a stimulator is chosen instead of a lesion, then the patient is sedated for placement of the chest lead and controller underneath the skin if adequate improvement of symptoms is obtained during the operation. The stimulator is usually not turned on until the next day or sometimes for several weeks.
Because of the imaging steps and calculations as well as the intraoperative testing the procedure usually takes most of a day.
Post-operatively the patient is observed in the recovery room for approximately one hour
and then returned to his hospital room. He may eat and drink immediately after the surgery and is often able to
leave the hospital in one or two days. The hypokinesia, rigidity and dyskinesia generally improves immediately.
Sometimes the tremor continues to gradually diminish over several days to weeks.
Deep brain stimulators need to be reprogrammed at least twice during the first six weeks to achieve optimal improvement in symptoms. The stimulator batteries usually last from three to five years and changing them requires a small operation. The patient can turn the stimulator on and off with a magnet. Turning it off extends the battery life.
Many patients experience swelling around the eyes which we believe is from the local anesthetic used for placing the frame. The swelling can be quite severe but resolves spontaneously. Keeping the head elevated is the only process that seems to speed the resolution of the swelling.
If the surgery is successful without side effects, no special post-operative care or training is required for lesioning procedures. Stitches can be removed one week after surgery. Headache in the post-operative phase is usually minimal and can generally be controlled with Tylenol. Most patients stay on their pre-operative medications although simplification of the schedule and/or reduction in dose is often possible.
Many people worry unnecessarily about the cost of movement disorders surgery. While it is an expensive procedure,
it should be covered by insurance just like any other operation. Some insurance may require preauthorization. Medicare
and Medicaid policies vary from State to State. In general, FDA approved indications are likely to be covered.
Reimbursements to physicians and hositals may not cover all of the costs as the stimulator alone costs over $10,000.
However, in general, patients can not be billed for the excess. (Thus many centers ration the number of procedures
they perform resulting in long waiting lists. Fortunately, this has not yet been necessary here at Wake Forest.)
Although basic Parkinson's disease research is the target of increased federal
funding because of the tremendous support of people like the actor, Michael J Fox, there is a tremendous need for
additional clinical research to attempt to cure Parkinson's disease, tremor of other causes, and dystonia.
The Wake Forest University School of Medicine is actively involved in trying to cure these diseases and encourages
donations to support our research efforts. For information about how to make a tax-deductible contribution, please,
send a check, call (800) 899-7128 or see http://www.wfubmc.edu/surg-sci/ns/md-gifts.html.
To schedule an appointment to discuss surgery, please, call the numbers below or click on
the icon below for on line scheduling:
.
For more information see the Parkinson’s
Disease Index on the Internet at http://www.wfubmc.edu/surg-sci/ns/pd.html or the Essential
Tremor Index at http://www.wfubmc.edu/surg-sci/ns/tremor.html.
For a detailed slide presentation see:
http://www.wfubmc.edu/surg-sci/ns/MDSurgery.html
For a video presentation (including an actual operation) of the deep brain stimulator for Parkinson's disease see:
http://www.wfubmc.edu/slp3d/dbsindex.html
Stephen B. Tatter, M.D., Ph.D.
Department of Neurosurgery
Wake Forest University School of Medicine
Winston-Salem, NC 27157-1029
phone: (336) 716-4047 or 716-6438
toll free (US): (800) 446-2255
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130902 Stephen B. Tatter, M.D., Ph.D.