What is deep brain stimulation (DBS)?
Deep brain stimulation (DBS) is a surgical procedure that involves implanting electrodes in the brain, which deliver electrical impulses that block or change the abnormal activity that cause symptoms.
The deep brain stimulation system consists of four parts:
- Leads (thin insulated wires) that end in electrodes that are implanted in the brain
- A small pacemaker-like device, called a pulse generator, that creates the electrical pulses
- Extension leads that carry electrical pulses from the device and are attached to the leads implanted in the brain
- Hand-held programmer device that adjusts the device’s signals and can turn the device off and on.
In deep brain stimulation, electrodes are placed in the targeted areas of the brain. The electrodes are connected by wires to a type of pacemaker device (called an implantable pulse generator) placed under the skin of the chest below the collarbone.
Once activated, the pulse generator sends continuous electrical pulses to the target areas in the brain, modifying the brain circuits in that area of the brain. The deep brain stimulation system operates much the same way as a pacemaker for the heart. In fact, deep brain stimulation is referred to as “the pacemaker for the brain.”
How is deep brain stimulation (DBS) used to treat Parkinson’s disease?
Deep brain stimulation (DBS) delivers electrical impulses to a targeted area of the brain that is responsible for the movement symptoms (also called motor symptoms) caused by Parkinson’s disease. The electrical impulses disrupt the abnormal activity that occurs in the brain’s circuitry, which is causing the symptoms.
There are three areas in the brain that can be targets for deep brain stimulation in patients with Parkinson’s disease. They are the subthalamic nucleus, the globus pallidus internus, and the ventral intermediate nucleus of the thalamus. Each of these areas plays a role in the brain’s circuitry that is responsible for the control of movement.
The specific area in the brain to target in an individual with Parkinson’s disease depends on symptoms that need to be treated. For example, deep brain stimulation of subthalamic nucleus is effective for all major movement symptoms of Parkinson's disease, such as tremor, slowness of movement (bradykinesia), stiffness (rigidity), and problems with walking and balance. Deep brain stimulation of globus pallidus is another effective target for a wide range of Parkinson's symptoms. The thalamic target is sometimes selected for patients with tremor symptoms. The recommended target for each patient is made collaboratively with the neurologist, neurosurgeon and other caregivers involved in the decision making process.
How do I know if I’m a candidate for deep brain stimulation (DBS)?
Before being considered a candidate for deep brain stimulation (DBS), patients with Parkinson’s disease must undergo an extensive evaluation process. Ideally, a multidisciplinary team of specialists in the area of movement disorders will assess the patient. This clinical team typically includes a neurologist, neurosurgeon, neuropsychologist and psychiatrist.
If patients are well managed on medications, DBS is not considered. Candidates for DBS are patients who meet one or more of the following criteria:
- Symptoms are not well controlled despite receiving the appropriate dose of levodopa and other medications.
- Symptoms are significantly reducing patients’ quality of life.
- Abnormal or uncontrolled involuntary movements (dyskinesia) or motor fluctuations are not improving despite adjustments in medications.
- Four or more doses of levodopa are required a day.
- Tremors that have not been able to be controlled by medications.
Levodopa response test
Patient’s response to a single dose of levodopa is another test physicians use to identify which patients are likely to benefit from DBS. In this test, patients stop taking levodopa for 8 to 12 hours and then receive a single dose. Patients are likely to benefit from DBS if they have a clear positive response after receiving the single dose of levodopa.
For many patients, the response to DBS will be similar to levodopa but without the symptoms fluctuations. In addition to this, DBS is still effective for tremor in Parkinson’s disease that may not be responsive to levodopa and will also help reduce dyskinesia related to medication use.