The Changing Role of Deep Brain Stimulation

THE CHANGING ROLE OF DEEP BRAIN STIMULATION IN THE TREATMENT OF PARKINSON'S DISEASE

by Michael Rezak, MD, PhD

Parkinson's disease (PD) affects approximately one and a half to two million people in the United States. Parkinson's begins most commonly in the sixth decade of life, but approximately ten percent of those diagnosed with the disease are between the ages of 21 and 40. This disease is characterized by a tremor that occurs at rest, stiffness, slowness, and walking and balance difficulties which progress slowly over time. Although no cure has yet been discovered, many medications are available that can manage the symptoms for a number of years. Nevertheless, with progression of the disease, a time may come when medicines may no longer provide adequate relief.

Fortunately, neurosurgical options are available that can regain control of Parkinson's symptoms. The neurosurgical option, deep brain stimulation (DBS), is now considered "main stream" treatment and should be utilized before a patient enters the later stages of the disease. The reliability, relatively low risk and the potential dramatic benefit of DBS for the appropriate patient should place this procedure in the forefront of treatment options when inadequate benefit is derived from medications.

It is estimated that approximately ten percent of all Parkinson's patients are appropriate candidates for neurosurgical treatment of their disease. Yet, many patients and physicians remain uninformed about this option or may have unrealistic fears about surgery. Others falsely believe that DBS is only for the most advanced patient. It cannot be emphasized enough that middle stage patients who are not obtaining adequate relief from their medications or who have intolerable dyskinesias and motor fluctuations are, in fact, excellent candidates.

DBS for the treatment of PD was approved by the FDA in January 2002, but because of its great efficacy in Europe, it was actually being performed in certain parts of the United States for many years before the formal approval. The device used in the procedure is manufactured by Medtronic Inc. and is called Activa® Parkinson's Control Therapy. The surgical procedure requires the implantation of a lead containing four electrodes in one of two sites within a very specific region of the brain called the basal ganglia. The two sites are the subthalamic nucleus and the internal segment of the globus pallidus which are accurately identified using MRI scanning and neurophysiological mapping. The lead is then connected by an extension wire under the skin to a programmable power supply (generator) placed under the clavicle. While the device is turned on and delivering electrical pulses, the Parkinson's symptoms, dyskinesias and motor fluctuations can be markedly improved or may even disappear. DBS can also result in significant medication reductions. It should be noted that in most cases both sides of the brain will need to be implanted with a DBS device.

The DBS procedure requires a team approach. The team includes an experienced functional neurosurgeon, a movement disorders neurologist, a nurse specialist and a neurophysiologist in addition to the usual operating room staff. Patients typically stay in the hospital for three days. In our Center, approximately one month after surgery (some centers vary on this time frame), the nurse and the neurologist will initially program the DBS device to obtain optimal benefit for the patient's symptoms. This first programming session can take several hours. Several subsequent visits for additional programming are usually necessary but are typically of shorter duration. Deep brain stimulation can be extremely beneficial in reducing or eliminating motor fluctuations and drug induced involuntary movements. A reduction in medication may also benefit drug induced mental status changes.

All surgical procedures carry certain risks. The DBS procedure poses a one to two percent risk of a stroke or hemorrhage which can occur during the procedure. Other very low risks can include infection, wire breakage and skin erosion over the wire. While not a risk, the battery must be replaced every three to five years which is performed as an outpatient procedure.

When considering DBS surgery, a Center that performs this procedure on a regular basis with an experienced and permanently established team should be selected. Furthermore, it is my opinion that intraoperative microelectrode mapping is mandatory to assure a high degree of success and thus an experienced neurophysiologist must be a part of the team. The concept of employing DBS earlier in the course of PD (when greater benefit can be obtained) cannot be over emphasized.

We continue to make great strides in the treatment of PD. I am personally grateful to have DBS surgery in our armamentarium of treatment options for our patients who have exhausted medical management and who would otherwise be relegated to a nonfunctional status. Although I have emphasized consideration of DBS surgery for patients earlier in the course of PD at which time greater improvement may be seen, DBS surgery still remains appropriate for some patients with more advanced symptoms as well.

Dr. Rezak is the Medical Director of the APDA National Young Onset Center as well as the Director of the Movement Disorders Center and Co-Director of the Deep Brain Stimulation Program of the Neurosciences Institute at Central DuPage Hospital in Winfield, IL. Dr. Rezak is also on the Speaker's Bureau for Allergan, Novartis, Medtronic, Teva, and GlaxoSmithKline.

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