Introduction:
Parkinson’s is a progressive disorder of the nervous system that affects body movements of the affected person. This disease is more common in people 60 years old and older.
First documented as “shaking palsy” in 1817 by Physician James Parkinson, Parkinson’s disease (PD), which bears his name, has presented patients and clinicians with significant treatment challenges due to the debilitating neurologic complications related to the disease. As per an estimate, India has 1 Million people suffering from Parkinson’s, while worldwide this figure is about 10 million. Today Parkinson’s is the second most common neurodegenerative disease after Alzheimer’s disease.
Parkinson’s Disease and Deep Brain Stimulation (DBS)
For many patients, medications are effective for maintaining a good quality of life. These medications work by stimulating the remaining cells and thus restore the balance between the chemicals in the brain.
However, some patients, with the passage of time, develop variability in their response to treatment, known as “motor fluctuations. During “on” periods, a patient may move with relative ease, often with reduced tremor and stiffness. During “off” periods, patients may have more difficulty controlling movements. Off periods may occur just prior to a patient taking their next dose of medication, and these episodes are called “wearing off.” For such patients, doctors recommend surgery to control the symptoms.
Deep Brain Stimulation (DBS)
Currently, the most common surgical treatment for Parkinson’s disease is Deep Brain Stimulation. This treatment strategy is best in cases of bradykinesia, rigidity and tremors in patients who are not responding to medication in desired manner, or patients who suffer from medication induced dyskinesias.
DBS offers a safer alternative to other surgical procedures. It utilizes small electrodes which are implanted to provide an electrical impulse to either the subthalamic nucleus of the thalamus or the globus pallidus, deep parts of the brain involved in motor function. Implantation of the electrode is guided through magnetic resonance imaging (MRI) and neurophysiological mapping, to pinpoint the correct location.
The electrode is connected to wires that lead to an impulse generator or IPG (similar to a pacemaker) that is placed under the collarbone and beneath the skin. Patients have a controller, which allows them to turn the device on or off. The electrodes are usually placed on one side of the brain. An electrode implanted in the left side of the brain will control the symptoms on the right side of the body and vice versa. Some patients may need to have stimulators implanted on both sides of the brain.
This form of stimulation helps rebalance the control messages in the brain, thereby suppressing tremor. DBS of the subthalamic nucleus or globus pallidus may be effective in treating all of the primary motor features of Parkinson’s and may allow for significant decreases in medication doses.
The Three Components of DBS
Owing to its similarity in function and design with pacemakers used in heart, DBS is sometimes called as “brain pacemakers’.
The DBS system consists of 3 components:
- The lead – a coated wire with a number of electrodes at the tip that deliver electric pulses to the brain tissue. It is placed inside the brain and connects to an extension wire through a small hole in the skull.
- The Extension – an insulated wire that connects the lead to the neurostimulator. It is placed under the skin and runs from the scalp, behind the ear, down the neck, and to the chest.
- Neuro-Stimulator – A programmable battery-operated medical device, called “Implantable Pulse Generator (IPG). This is the main device that creates electric pulses. It is placed under the skin of the chest below the collarbone or in the abdomen.
In addition to these 3 main components, the patient uses a handheld controller to turn the DBS system on and off. The doctor programs the stimulator settings with a wireless device. The stimulation settings can be adjusted as a patient’s condition changes over timeThe lead (also called an electrode)—a thin, insulated wire—is inserted through a small opening made in the skull and implanted in the brain. The extension is an insulated wire connecting the lead to the IPG. This device, of the size similar to a stopwatch, is usually implanted under the skin near the collarbone. Or, it may be implanted lower in the chest or under the skin over the abdomen.
What Are the Facts?
Deep Brain Stimulation (DBS) surgery was first approved in 1997 to treat Parkinson’s disease (PD) tremor, then in 2002 for the treatment of advanced Parkinson’s symptoms. More recently, in 2016, DBS surgery has been approved for the earlier stages of PD — for people who have had PD for at least four years and have motor symptoms not adequately controlled with medication.
DBS is certainly the most important therapeutic advancement since the development of levodopa. Some of the facts associated with DBS are as follows:
- DBS is a surgical procedure for treating a variety of disabling neurological symptoms, like symptoms of Parkinson’s, such as tremor, rigidity, stiffness, slowed movement and slowed walking.
- It is also used to treat essential tremor, a common neurological movement disorder.
DBS does not damage healthy brain tissue or destroy nerve cells. It only interrupts the problematic electrical signals from targeted areas in the brain. - At present, this 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 MRI or CT scanning to identify and locate the exact target within the brain where electrical nerve signals generate the PD symptoms.
- During surgery, some surgeons 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, sub-thalamic nucleus (STN) 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 active contacts of the lead in the brain. These impulses interfere with and block the electrical signals that cause PD symptoms.
Am I a Good Candidate for DBS?
Are you not getting desired benefits from medication? Are you finding it increasingly difficult to do routine work? If your answer to these questions is “YES”, then you are a good candidate for DBS. You should immediately consult a doctor to see if DBS is the right treatment for you.
Specifically speaking, you are a good candidate for DBS, if:
- You have had PD symptoms for at least five years.
- You have “on/off” fluctuations despite consistent and regular medication dosing.
You have dyskinesias. - You are unable to tolerate anti-parkinson’s medications due to side effects.
- You have tremor that is not well controlled with medication (even with medical management by a movement disorders specialist).
- 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 anti-Parkinson’s medications under the supervision of a movement disorders neurologist.
- You have PD symptoms that interfere with daily activities.
Levodopa Response Test
One more test that doctors use to identify which patients are likely to benefit from DBS is called Levodopa response test. In this test, patients stop taking levodopa for 8 to 12 hours and then receive a single dose. If the patients show a clear positive response after this single dose, then they are likely to benefit from DBS.
Conclusion:
Based upon the type and severity of symptoms, the deterioration of a patient’s quality of life and a patient’s overall health, a doctor may suggest to go for surgery.
Currently, the most common surgical treatment for Parkinson’s disease is Deep Brain Stimulation. This treatment strategy is best in cases of bradykinesia, rigidity and tremors in patients who are not responding to medication in desired manner, or patients who suffer from medication induced dyskinesias.
Unlike other surgeries, such as pallidotomy or thalamotomy, DBS does not damage the brain tissue. Thus, if better treatments develop in the future, the DBS procedure can be reversed.
