Deep Brain Stimulation for Parkinsons Disease

STN-DBS is a treatment that involves electrical stimulation of the brain. It is done in several stages.

First, surgery is performed to place electrodes in either one or both sides of the brain in a small region called the subthalamic nucleus (STN). This requires a 1-2 night stay in the hospital. After about one week, the patient returns to the hospital for day surgery in which one or two pulse generators, or "batteries," are placed under the skin of the chest. These devices are connected to the electrodes in the brain. Several weeks later, your movement disorder specialist will turn the pulse generators on to activate the electrodes in the brain.

GPi-DBS is a treatment that involves electrical stimulation of the brain. The procedure for GPi-DBS is similar to the procedure for STN-DBS and is done in several stages. The only difference is the region in the brain where electrodes are implanted.

First, surgery is performed to place electrodes in either one or both sides of the brain in a small region called the Globus Pallidus pars interna. This requires a 1-2 night stay in the hospital. After about one week, the patient returns to the hospital for day surgery in which one or two pulse generators, or "batteries," are placed under the skin of the chest. These devices are connected to the electrodes in the brain. Several weeks later, the pulse generators are turned on and begin to activate the electrodes in the brain.

Although we cannot tell for sure who will or will not respond, we and others have found that both STN and GPi treatment works best for symptoms that have responded well to levodopa in the past. If your symptoms have not responded to levodopa, STN/GPi-DBS treatment may not be right for you. In addition, some Parkinson's disease symptoms, such as freezing of gait (when you get stuck as you try to walk) or soft voice, are sometimes less responsive to DBS treatment. Other factors that are considered in deciding who might be a candidate for this treatment are summarized below.

STN and GPi surgery generally have the same criteria for candidacy and similar long term outcomes. The choice of the surgery (STN or GPi) is ultimately decided by a collaboration of movement disorder neurologists and the operating neurosurgeon.

Factors that may mean you are a good candidate are listed below:

• Patients who have advanced idiopathic Parkinson's disease that has responded well to levodopa
• Patients who have unsatisfactory side effects associated with levodopa treatment, such as dyskinesias and motor fluctuations (periods of time during the day when symptoms are poorly controlled)
• Patients who are able to travel to BIDMC for frequent follow-up appointments for the first three months after surgery

A major advantage of this procedure is that it helps even out a patient's response to their medication. Patients who take dopaminergic medications often find that, at a certain point following each dose, there is a peak time of effectiveness when the medication works at its best. This is followed by a period where the medication is less effective and symptoms return. With STN/GPi-DBS, the continuous stimulation of the targeted brain area helps make these variations in treatment response less pronounced. That is, rather than having several good hours, followed by periods when symptoms reappear, there is increased relief of symptoms throughout the day. Also, many patients who are helped by levodopa are bothered by dyskinesias - abnormal involuntary movements caused by the levodopa. Treatment with STN/GPi-DBS will allow these patients to lower their levodopa dose, which will in turn decrease their episodes of dyskinesia.

It is important to understand that patients who have STN/GPi-DBS must make frequent visits to the outpatient clinic during the first three months after surgery. These visits are needed so that doctors can program your stimulation so that it is just right for you. The doctor can change the strength and frequency of the electrical stimulation that your brain is receiving. These changes are then matched with adjustments in your medications until the right balance is achieved.

At first, you may be coming in as often as every two weeks for adjustments. Once stable settings are found and a new medication schedule has been established, you will not need to come in as frequently.

During the first few months, you require frequent adjustments. Over time, you may need additional changes as your Parkinson's disease progresses. If you live far from the hospital or have difficulty arranging transportation, this is something to carefully consider before deciding to have the surgery.

Any surgical procedure carries some risk, and this is also true of STN and GPi-DBS surgery as well. Your overall health will be evaluated carefully before you are recommended for this surgery to make sure the risk of problems is low. Fortunately, neurologic side effects of both STN-DBS and GPi-DBS have been uncommon in our experience. The most potentially serious side effect is bleeding in the part of the brain where each electrode is inserted. Some bleeding in the brain occurs in 1-2% of procedures in which a needle, wire, or electrode is passed through the brain. Fortunately, the majority of such brain hemorrhages are small, produce little or no neurologic deficit, and are detected only by postoperative brain imaging, which is done the day after surgery. To help prevent bleeding, patients are instructed not to take any blood thinners such as warfarin (Coumadin), heparin, aspirin, anti-inflammatory drugs, or arthritis medications (all of which interfere with blood clotting mechanisms) for at least two weeks before surgery.

There are several possible problems related to equipment that may occur months to years after the system has been installed. These include breakage of the electrode wire under the skin in the scalp or neck and skin infection or skin breakdown in the scalp. With the exception of certain types of hardware breakage, these problems can usually be corrected without removal or replacement of the brain electrode. Your neurologist and neurosurgeon will speak with you in more detail concerning these possible complications and answer any questions you may have.

If MRI is needed for any reason after having DBS placed, you will need to let the radiologist know that you have a DBS system in place. Because MRI uses a powerful magnet to make images, care is needed to avoid damaging the hardware or any tissues that are in contact with the DBS. For this reason, head MRI may be done in a very limited fashion. MRI of other body parts may not be done safely at this time and CT scan is recommended. Other tests, like X-rays, ultrasound or CT scans, can be done safely.

Also, diathermy (e.g., shortwave diathermy, microwave diathermy or therapeutic ultrasound diathermy) is contraindicated because diathermy's energy can be transferred through the system, which can cause tissue damage and can result in injury or death.

If you and your doctor decide that you might be a good candidate for this surgery, we will ask you to meet with a number of specialists on our team and to undergo a series of examinations. Through this process, we will be better able to tell if there is a good chance the surgery will help you without posing any unusual risk. This process will include:

• A prolonged, in depth evaluation of your Parkinson's disease - We will ask you to come to our clinic without taking your usual morning Parkinson's medications and spend 4-6 hours with a nurse practitioner, neurologist, and other members of our staff as you follow your usual medication schedule. During the visit, staff will carefully evaluate your symptoms and your response to the medication you are taking.
• Neuropsychological testing - You will meet with a neuropsychologist who will administer tests to evaluate how well your brain functions in the following areas such as attention/concentration, processing speed, learning and memory, reasoning, and executive functions.
• Meeting with the neurosurgeon - You will also meet with the neurosurgeon who will perform the operation. You will undergo a complete examination, and have a chance to talk about any questions or concerns you may have about the surgery. If needed, a magnetic resonance imaging (MRI) examination of the brain will be scheduled.

Once all these exams are complete, our team will look at the information and decide whether or not to recommend surgery. The DBS team at BIDMC is a multidisciplinary group of healthcare providers specializing in neurology, neurosurgery, social work and neuropsychology. If our team feels that further treatment with medication is needed, these recommendations will be provided to you and your referring physician. If surgery is recommended, you will be scheduled for the procedure to take place within approximately one month. Once your surgery has been scheduled, you will be given more information about coming to the hospital for routine pre-operative tests.

First Stage

You will stop your Parkinson's disease medication the night before the operation. The first stage is implantation of an electrode on either one or both sides of the brain which is done after you undergo an MRI wearing a head frame on the morning of the operation. The operation is done under intravenous anesthesia so that you can be awakened during parts of the procedure so that we can judge your responses to brain stimulation during the operation. Medication for discomfort or anxiety will be given if needed. Electrical recording and stimulation of the brain is carried out by an electrophysiologist to precisely identify and map out the surgical target. You may be asked to perform some simple motor or cognitive tasks so that the best location for electrode placement can be identified. After mapping of the brain, a permanent stimulating electrode is placed within the subthalamic nucleus. For patients undergoing bilateral surgery the same procedure is repeated on the other side of the brain. The procedure will take approximately 4 to 5 hours. After surgery your medication will be resumed and a CT or MRI scan will be done. You will be sent home after one or two nights in the hospital.

Second Stage

Both stages of DBS surgery may take place in one day. If the neurosurgeon decides to wait before proceeding with the second stage, you will return about 7 days later for the second stage. The pulse generator will be implanted under the skin just below or near the collar bone. This is done under general anesthesia and will take approximately 1-2 hours. Patients having an electrode placed on both sides of the brain will have two pulse generators. These will be connected to the brain electrode by an extension wire running under the skin from the top of the head and behind the ear to the pulse generator which will not be visible. You will go home on the same day. Your first programming session will be scheduled for approximately 3-4 weeks after the second stage operation.