Deep brain stimulation (DBS) is a surgical procedure used to treat several disabling neurological symptoms—most commonly the debilitating motor 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, dystonia, and focal epilepsy (epilepsy that originates in just one part of the brain). At present, the procedure is used only for individuals whose symptoms cannot be adequately controlled with medications. However, only individuals who improve to some degree after taking medication for Parkinson’s benefit from DBS.
DBS uses a surgically implanted, battery-operated medical device called an implantable pulse generator (IPG)—similar to a heart pacemaker and approximately the size of a stopwatch to—deliver electrical stimulation to specific areas in the brain that control movement, thus blocking the abnormal nerve signals that cause symptoms. The DBS system consists of three components: the lead, the extension, and the IPG. 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 specific 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 implantable pulse generator. The IPG (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.
Before the procedure, a neurosurgeon uses magnetic resonance imaging or computed tomography scanning to identify and locate the exact target within the brain for surgical intervention. Generally, these areas are the thalamus, subthalamic nucleus, and globus pallidus.
Once the system is in place, electrical impulses are sent from the IPG up along the extension wire and the lead and into the brain. These impulses block abnormal electrical signals and alleviate motor symptoms.
Most individuals still need to take medication after undergoing DBS. Many people with Parkinson’s disease experience considerable reduction of their motor symptoms after DBS and are able to reduce their medications. People with dystonia may respond better to DBS than medications in reducing involuntary muscle contractions. DBS targeting the thalamus can improve involuntary movement of the hands, arms, and head that is associated with involuntary tremor.
DBS for epilepsy may reduce the number of seizures over time. DBS does not improve cognitive symptoms in PD and indeed may worsen them, so it is not generally used if there are signs of dementia. DBS changes the brain firing pattern but does not slow the progression of the neurodegeneration.
DBS uses electrical stimulation to regulate electrical signals in neural circuits to and from identified areas in the brain to improve movement symptoms. Thus, if DBS causes unwanted side effects or newer, more promising treatments develop in the future, the implantable pulse generator can be removed, and the DBS procedure can be halted. Also, stimulation from the IPG is easily adjustable—without further surgery—if the person’s condition changes. Some people describe the pulse generator adjustments as “programming.”
DBS involves minimal permanent surgical change to the brain. Although minimally invasive, DBS is a surgical procedure that carries some associated risk. There is a low chance that placement of the stimulator may casue bleeding or infection in the brain. Complications may include bleeding and swelling of brain tissue, headaches, seizures, and temporary pain following the surgery.