Stereotactic Surgery for Parkinson's Disease
UVA surgeons perform stereotactic surgeries for the treatment of the debilitating symptoms of Parkinson's disease with good results.
Parkinson's disease is a progressive, degenerative disease whose victims experience the symptoms of bradykinesia, tremor and rigidity.
Initially, symptoms can be controlled with L-Dopa, but eventually, side effects of the medication preclude further dose increase.
The patient develops periods of painful spasms, "freezing" of movements and abnormal involuntary movements which can involve one or both sides of the body.
Several types of surgery are accepted in the treatment of Parkinson's disease. The most important are deep brain stimulation, pallidotomy and thalamotomy. These are all "stereotactic" surgeries, which means that a special frame is attached to the head for the operation. This frame has calibration marks that enable the surgeon to position instruments very precisely within the brain. Magnetic Resonance (MR) images are taken after the frame is put in place, and these images are used to find the correct target sites in the brain for the surgery.
Stereotactic surgery requires only a small incision and a hole less than 1/2 inch in diameter to be made in the skull. This is usually done under local anesthesia. Because stereotactic brain surgery is "minimally invasive" many stereotactic surgeries can be performed on an outpatient basis.
At UVA, a Parkinson’s Disease patient having stereotactic surgery is admitted the day of the procedure, a localizing frame is attached to the patient's head and an MRI scan is performed. The surgical team then focuses on a particular target, depending on the type of procedure to be performed:
Deep Brain Stimulation (DBS)
This procedure involves the permanent placement of an electrode into the thalamus, the pallidum or the subthalamic nucleus (STN). These are parts of the brain that are involved in the control of movement. In Parkinson's Disease, these areas are affected and can contribute to symptoms such as tremor, rigidity and hypokinesia. The electrode is connected to a small battery powered stimulator that looks like a cardiac pacemaker. The stimulator is surgically implanted under the skin just below the collarbone, and there is a wire that runs beneath the skin to connect it to the electrode in the brain. The stimulator produces electrical impulses that affect the nerve cells around the electrode and improve some of the symptoms. Unlike earlier surgical treatments, DBS does not destroy brain cells (except for those damaged by simply placing the electrode into the brain), and the stimulator can be reprogrammed to provide the best relief of symptoms if the effectiveness ever begins to diminish. Because the DBS treatment does not damage many brain cells, it usually has lower risk. Because of the lower risk and the increased flexibility of treatment, DBS has become the treatment of choice for most patients undergoing surgical treatment for Parkinson’s Disease.
During DBS surgery, the surgeon makes an incision and a small hole in the skull. A thin needle electrode is then advanced into the target. At this point an electrophysiologist tests the patient. Electrical impulses are used to test the effect on movement and to simulate the effect of the treatment. Activity of individual brain cells is also measured; the activity of the individual cells is different in different brain areas, and this highly specialized recording can help ensure that the electrode is exactly in the target. The patient is awake for these tests and will need to pay attention and cooperate. After the tests confirm that the electrode is placed accurately, the permanent electrode is fixed in place where it emerges from the skull and the hole is closed. A MR scan is taken to confirm that the electrode is properly placed. The patient is then anesthetized while the surgeon threads the connecting wires under the skin and places the stimulator under the skin in the chest. The DBS device will be "off" until the patient comes back two weeks after the operation to have stitches removed. At that time the electrophysiologist will activate the device and program the stimulation.
This procedure is used when the main problem is severe tremor. The thalamus was the first target area approved for DBS in the United States, and there are still more patients with DBS electrodes in thalamus than other areas. About 90% of patients experience immediate relief of tremor, but thalamic DBS does not help very much with symptoms other than tremor.
This procedure is performed when rigidity, hypokinesia and tremor are present. The permanent electrode is placed into the pallidum, another part of the brain involved in movement. DBS in pallidum can benefit rigidity and hypokinesia, and an improvement in tremor will usually develop over several days or weeks. The effects of pallidal DBS can take several days to develop. This means it may take several programming appointments to get a good effect.
Subthalamic Nucleus (STN) DBS
This procedure is also an option for rigidity, hypokinesia and tremor. The permanent electrode is placed into the STN, which lies just below the thalamus. DBS in STN, like in pallidum, produces a benefit in rigidity, hypokinesia and tremor in a majority of patients. It may have the added value of enabling medications to be reduced further, but DBS of the STN can also interact with Parkinson’s Disease medicine. Because of the interaction with medicines, DBS of the STN is usually done on both sides. Otherwise one side of the body can have too little medication or the other side could have too much. As with pallidal DBS, it may take several programming appointments to get a good effect with STN DBS without bothersome side effects. The STN has become the most common target for surgical treatment of Parkinson’s Disease.
This procedure may be the surgery of choice when the main problem is severe tremor and Deep Brain Stimulation is not appropriate. For thalamotomy, a thin needle electrode is advanced into the thalamus, and the patient is tested by an electrophysiologist. As in DBS surgery, the patient needs to pay attention and cooperate in these tests. After the tests confirm that the electrode is placed accurately, a small, high frequency electrical current is applied to the electrode. This heats the tissue at the tip of the electrode, and destroys a small part (about 4mm in diameter) of the thalamus. About 90% of patients experience immediate relief of tremor. The advantage of the thalamotomy is that there is no incision in the chest, and no electrode, wire or stimulator permanently placed in the patient. There is no battery to wear out. The disadvantage is that the treatment is permanent and cannot be undone. There is a small but significant risk of permanent side effects such as impairment of voice, and a higher risk of complications such as stroke.
This procedure is performed when rigidity, hypokinesia and tremor are present and Deep Brain Stimulation is not appropriate. It entails placing the needle electrode into the pallidum. The placement of the electrode is confirmed with testing like in thalamotomy, and a small part of the pallidum is destroyed. This produces an immediate benefit in rigidity and hypokinesia in about 80% of patients, and an improvement in tremor usually develops over several weeks after the procedure. The advantages and disadvantages are much like for thalamotomy.
The results of any of these procedures involve only the movement symptoms of Parkinson’s Disease. Mental or emotional symptoms are not changed, and the disease will continue to progress.
The permanent benefits of the surgery can only be assessed a few months after the operation, when the brain has completely healed. Experience at UVA and other centers indicates that any benefits noted at 3 months after surgery will likely continue for years.
Pallidotomy, thalamotomy and DBS are safe procedures. There is less than a 1 percent incidence of intracranial bleeding and infection in our stereotactic neurosurgery patients. The risk of bleeding is probably lower in DBS than in pallidotomy or thalamotomy.
Thalamotomy and pallidotomy both carry a small risk of developing weakness of facial muscles, the arm or the leg on the side opposite the surgery. There is also a small risk of stroke occurring near the treated brain area within the first two months after the operation. This risk is much lower with DBS.
Thalamotomy has a small risk of speech impairment or difficulty swallowing. This risk may be higher if the procedure is done on both sides of the brain. This risk is much lower in DBS.
Pallidotomy carries a small risk of producing a blind spot in the visual field. If this complication develops in the right side of the visual field (when surgery is performed on the left side), it may make reading difficult. We have never experienced this complication at UVA, but it has been reported in other centers performing pallidotomies.
Parkinson's disease patients with mental impairment are not candidates for any of these operations. Respiratory, cardiovascular or other health problems that could increase the risk of any surgery should be discussed with your surgeon.
For More Information
Additional information can be obtained through the Stereotactic Neurosurgery Group:
W. Jeff Elias, MD
Department of Neurological Surgery
Charlottesville, VA 22908-0212
(434) 924-0451 FAX (434) 929-9656