Deep brain stimulation (DBS), a surgical therapy for Parkinson’s disease, is typically considered when a person who has had Parkinson’s for four years or more develops complications, such as dyskinesia(uncontrolled, involuntary movements) and/or significant “off” time (when medication isn’t working optimally and symptoms return). Like all currently available Parkinson’s therapies, DBS is a symptomatic treatment — it eases motor symptoms but does not change the underlying course of the disease.
DBS typically works best to lessen motor symptoms like stiffness, slowness and tremor. It doesn’t work as well for imbalance, freezing when walking or non-motor symptoms. DBS may even exacerbate thinking or memory problems so it’s not recommended for people with dementia.
A general rule is that DBS will likely improve Parkinson’s symptoms that respond to medication.
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.
The Evaluation prior to DBS Surgery
A team of experts, including a movement disorder specialist (a neurologist with extra training in Parkinson’s) and a neurosurgeon (a doctor who performs DBS procedures), conduct an extensive assessment when considering DBS for someone. The evaluation consists of medication and symptom review, examination both on and off Parkinson’s drugs, brain imaging, and oftentimes also detailed memory/thinking testing (to detect any problems that could worsen after DBS). If DBS is offered, it’s important to discuss the expected benefits (e.g., decreased tremor, fewer medications, etc.) as each person’s experience is unique. It’s also critical to discuss the potential surgical risks, including bleeding, stroke and infection.
The DBS Procedure and Device Programming
In DBS surgery, thin wires called electrodes are placed into one or both sides of the brain in specific areas (either the subthalamic nucleus or the globus pallidus interna) that control movement. Usually a person remains awake during surgery so that he or she can answer questions and perform certain tasks to make sure that the electrodes are positioned correctly. However, some medical centers now are using brain imaging to guide the electrodes to the right spot while a person is asleep. Each method has its pros and cons and may not be suitable for everyone or available everywhere.
Once the electrodes are situated, they are connected to a battery-operated device (similar to a cardiac pacemaker) that is typically placed under the skin below the collarbone. This device, called a neurostimulator, delivers continuous electrical pulses through the electrodes to decrease Parkinson’s symptoms.
A few weeks after surgery, a movement disorder specialist uses a handheld programmer to set parameters, tailored to each individual’s unique symptoms, into the neurostimulator. The DBS settings are gradually tweaked over time and medications are simultaneously adjusted. Most people are able to decrease (but not completely discontinue) Parkinson’s drugs after DBS. Determining the optimal combination of drugs and DBS settings — that which gives the most benefit and the least side effects — can take several months and even up to a year.
How DBS Works
Exactly how DBS works is not completely understood, but many researchers and specialists believe that DBS regulates abnormal electrical signaling patterns in the brain. In order to control normal movement and other functions, brain cells communicate with each other using electrical signals. In Parkinson’s disease, these signals become irregular and uncoordinated and lead to motor symptoms. DBS basically interrupts the atypical signaling patterns in a way that allows the cells to communicate more smoothly and thereby lessens symptoms.
Research on DBS
Researchers are working to improve upon the existing DBS devices and surgical methods with the goal of making the therapy beneficial for more symptoms and therefore for a greater number of people. Some researchers are targeting DBS to a different area of the brain — the pedunculopontine nucleus (PPN) — to treat walking and balance problems that don’t typically improve with present-day DBS strategies. Others are developing so-called “smart” DBS, in which devices record a person’s unique brain signals and deliver electrical stimulation only when needed, such as when symptoms return, rather than continuously, as the current systems do.
Advances in the understanding of DBS mechanisms and improvements in the devices and surgical approaches may eventually make the therapy effective for more symptoms and, as a result, for a wider variety of people at different stages of Parkinson’s.
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