Deep brain stimulation for Parkinson's disease

Treatment Overview
Deep brain stimulation uses electrical impulses to stimulate a target area in the brain. The stimulation affects movement by altering the activity in that area of the brain. The procedure does not destroy any brain tissue, and stimulation can be stopped at any time by turning off the device that supplies the electrical impulses.

Surgery is required to implant the equipment that produces the electrical stimulation. The person is awake for the first part of the procedure, during which the scalp is numbed; general anesthesia is used for the rest of the procedure. A small hole is drilled in the skull, and tiny wire electrodes are placed in the brain. A small battery-powered device (generator) similar to a pacemaker is implanted in the chest and connected to the electrodes in the brain by a wire. The procedure usually takes 3 to 4 hours, although it may take up to 8 hours in some cases.

When turned on, the device sends 100 to 180 electrical pulses per minute to stimulate the specific area of the brain. The person can turn the device on and off by holding a magnet against the skin over the device. The device can be programmed so that it delivers the correct level of stimulation and so that it turns on and off according to a set schedule.

What to Expect After Treatment
The person will remain in the hospital for several days after the procedure while the doctor checks the effect of deep brain stimulation.

Why It Is Done
Deep brain stimulation may be used to relieve symptoms of Parkinson’s Disease especially tremor, when they cannot be controlled with medication. It is considered the surgical treatment of choice for Parkinson's disease because it is more effective, safer, and less destructive to brain tissue than other surgical methods.

Deep brain stimulation of the thalamus has been approved by the U.S. Food and Drug Administration (FDA) for treating disabling tremor caused by Parkinson's disease, as well as essential tremor.

Procedures that stimulate the subthalamic nucleus and the globus pallidus have also been approved by the FDA. These procedures help control a wider range of symptoms (in addition to tremor) and are used more often than stimulation of the thalamus.

How Well It Works
Deep brain stimulation of the thalamus is effective in reducing tremor. It does not affect slow movement (bradykinesia), stiffness (rigidity), or other symptoms.

Deep brain stimulation of the subthalamic nucleus or the globus pallidus may:

• Reduce tremor and, to a lesser extent, other symptoms of Parkinson's disease. Deep brain stimulation tends to have the greatest effect on tremor, but slow movement and stiffness can also be reduced and gait can be improved.
• Reduce the on-off motor fluctuations associated with long-term use of levodopa. During the course of a day, a person may have “on” periods when the levodopa controls Parkinson's symptoms and “off” periods when the medication stops working. Deep brain stimulation can reduce the length and severity of “off” periods.
• Reduce the abnormal movements (dyskinesias) that are side effects of levodopa therapy.
  

The practical effects of deep brain stimulation depend in part on which area of the brain receives the stimulation. Stimulation of the subthalamic nucleus reduces symptoms of Parkinson's disease, which allows people to reduce the amount of levodopa they are taking. Taking a lower dose helps reduce the abnormal movements (dyskinesias) that result from long-term levodopa therapy.

In contrast, stimulation of the globus pallidus reduces the dyskinesias associated with levodopa therapy, which allows people to increase the amount of levodopa they are taking without increasing side effects. In this case, the increased dosage of levodopa, rather than the brain stimulation itself, is what helps reduce tremor and other symptoms caused by Parkinson's disease.

Risks
Deep brain stimulation carries less risk than other surgical procedures used to treat Parkinson's disease. Risks may include:

• Bleeding in the brain during the surgery, resulting in a stroke.
• Numbness, tingling, twitching, or other abnormal sensations when the device is turned on. (These usually do not last long.)
• Infection or skin irritation caused by the device in the chest (stimulator) or electrodes.
• Break in the wire leading from the electrode to the stimulator. Repairing the problem would require another surgery.
• Need for a new battery for the device. A battery typically will last about 5 years; surgery is needed to replace it.
• Failure or malfunction of the stimulator or the electrodes.