Deep Brain Stimulation

What are the facts?

• Deep brain stimulation (DBS) is a surgical procedure used to treat a variety of disabling neurological symptoms—most commonly the debilitating symptoms of Parkinson’s disease (PD), such as tremor, rigidity, stiffness, slowed movement, and walking problems.
• The procedure is also used to treat essential tremor, a common neurological movement disorder.
• DBS does not damage healthy brain tissue by destroying nerve cells. Instead the procedure blocks electrical signals from targeted areas in the brain.
• At present, the procedure is used only for patients whose symptoms cannot be adequately controlled with medications.DBS uses a surgically implanted, battery-operated medical device called a neurostimulator—similar to a heart pacemaker and approximately the size of a stopwatch—to deliver electrical stimulation to targeted areas in the brain that control movement, blocking the abnormal nerve signals that cause tremor and PD symptoms. Before the procedure, a neurosurgeon uses magnetic resonance imaging (MRI) or computed tomography (CT) scanning to identify and locate the exact target within the brain where electrical nerve signals generate the PD symptoms.
• Some surgeons may use microelectrode recording—which involves a small wire that monitors the activity of nerve cells in the target area—to more specifically identify the precise brain target that will be stimulated.
• Generally, these targets are the thalamus, subthalamic nucleus, and a portion of the globus pallidus.
• Once the system is in place, electrical impulses are sent from the neurostimulator up along the extension wire and the lead and into the brain. These impulses interfere with and block the electrical signals that cause PD symptoms.

The DBS system consists of three components:

• The lead- (also called an electrode)—a thin, insulated wire—is inserted through a small opening in the skull and implanted in the brain. The tip of the electrode is positioned within the targeted brain area.
• The extension- is an insulated wire that is passed under the skin of the head, neck, and shoulder, connecting the lead to the neurostimulator.
• The neurostimulator- (the "battery pack") is the third component and is usually implanted under the skin near the collarbone. In some cases it may be implanted lower in the chest or under the skin over the abdomen.

There are many brain targets that the DBS lead may be placed within; which one should you choose?

• There are three brain targets that have been FDA approved for use in Parkinson’s disease.
• The most commonly utilized brain targets include the subthalamic nucleus (STN) and also the globus pallidus interna (GPi).
• Target choice should be tailored to a patient’s individual needs (Benabid, Benazzouz et al. 1998; Okun and Vitek 2004; Benabid, Chabardes et al. 2005; Rodriguez, Fernandez et al. 2007).
• There are many ongoing studies that will help to refine target choice for individual patients.
• Although the picture is not yet clear on the issue of target choice, the STN does seem to provide more medication reduction, while GPi may be slightly safer for language and cognition.

View pictorial representations of each of the three main DBS targets used in Parkinson’s disease (figures were used with permission of Dr. Okun).

What is the prognosis?

Although most patients still need to take medication after undergoing DBS, many patients experience considerable reduction of their PD symptoms and are able to greatly reduce their medications. The amount of reduction varies from patient to patient but can be considerably reduced in most patients. The reduction in dose of medication leads to a significant improvement in side effects such as dyskinesias (involuntary movements caused by long-term use of levodopa). There is a 1-3% chance of infection, stroke, cranial bleeding, or other complications associated with anesthesia, per side that is done. It is best to discuss the risks associated with your neurologist because there are many risk factors, including underlying medical conditions.

How do I know if I am a good candidate for DBS?

• You have had PD symptoms for at least five years.
• You have “on/off fluctuations, with or without dyskinesia.
• You continue to have a good response to PD medications, especially carbidopa/levodopa, although the duration of response may be insufficient.
• You have tried different combinations of levodopa/carbidopa and dopamine agonists under the supervision of a movement disorders neurologist.
• You have tried other PD medications, such as entacapone, tolcapone, selegiline or amantadine without beneficial results.
• You have PD symptoms that interfere with daily activities.

http://www.parkinson.org/understanding-parkinsons/treatment/surgery-treatment-options/Deep-Brain-Stimulation

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