Parkinson’s disease: Deep brain stimulation

Photo of a couple preparing a meal (PantherMedia / Rawpixel) In deep brain stimulation (DBS), one or two electrodes are implanted in the brain. There they send electrical signals to nerve cells that influence particular movements. This can reduce the symptoms of Parkinson's disease. But these “brain pacemakers” can have side effects too, and are only suitable in some people who have Parkinson's disease.

Parkinson’s disease is typically treated with medication. The medication usually works very well in the first few years of treatment, but it starts becoming less effective after some time. This is particularly noticeable because of how it affects motor (movement) symptoms. People go through phases of muscle stiffness followed by phases of uncontrolled movements, then stiffness again, and so on. They may also experience prolonged involuntary shaking (tremor). If someone has very distressing symptoms despite taking medication, a treatment known as deep brain stimulation (sometimes called “a brain pacemaker”) might be considered. This treatment can reduce the symptoms, but it can't cure the disease. The electrodes can only be placed inside the brain (implanted) in certain specialized hospitals.

What is deep brain stimulation?

Deep brain stimulation involves a surgical procedure where one or two electrodes (fine wires) are fixed in place just under the scalp at one end and then inserted deep into the brain through the skull. A pacemaker-like device known as a pulse generator regularly sends weak electrical signals (impulses) along the electrodes to very specific areas of the brain – that's why it's called “deep brain stimulation.” The electrodes are connected to the pulse generator through fine cables that run under the skin. The pulse generator is placed under the skin around the collarbone area, for instance.

The signals travel along certain electric circuits in the brain, influencing muscle activity. This makes it possible to reduce movement problems in people who have Parkinson's disease. But it's still not clear exactly how deep brain stimulation works. It is thought that it helps to improve communication between different areas of the brain.

Illustration: In DBS, electrical signals are sent to certain areas of the brain (in this example: electrode on one side of the brain only)In deep brain stimulation, electrical signals are sent to certain areas of the brain (in this example: electrode on one side of the brain only)

Who can have this treatment?

Deep brain stimulation is only suitable for certain people who have Parkinson’s disease. In Germany, several hundred people receive a brain pacemaker per year.

The main requirement is that the person has very distressing symptoms despite taking medication. These include, in particular, persistent tremor and alternating involuntary movements and muscle stiffness. There's no clear age limit, but people have to be “healthy” enough for the surgery not to be too risky. For instance, they shouldn't have any serious heart or lung diseases. Deep brain stimulation also isn't an option if the person has a psychological illness such as psychosis or dementia.

To find out whether someone can have this treatment, various examinations and tests need to be carried out first: a general physical check-up, an MRI scan of the head, memory tests and a psychiatric examination. A special test (known as the levodopa challenge test) is also done in order to find out how well certain Parkinson’s disease medications work. This can help doctors to get an idea of how effective deep brain stimulation is likely to be.

The person who has Parkinson’s disease discusses the results of the examinations together with their doctor and their loved ones. The potential benefits and harms of the surgery are considered too. If possible, friends or family members should go along to the appointment. It’s especially important to talk about your own expectations of the surgery, as well as about what can be realistically expected. This helps to avoid disappointment if the deep brain stimulation doesn't have the desired effect. While considering the pros and cons of this surgery, it’s important to talk about the other treatment options too.

What does the surgery involve?

The operation is done in two steps and takes about 6 to 8 hours in total. The patient is awake for about 2 of those hours.

Step 1: Inserting the electrodes

First of all, a CT scan (computer tomography) of the brain is done in order to find out where to best insert the electrode(s). The target location will depend on the patient's symptoms.

If possible, the procedure takes place under light anesthesia, using a medication to numb the area. Otherwise it is done under general anesthesia. During the operation the person's head is fixed in place using a special head frame so they can't move it. Their scalp is partially or completely shaved, and cuts are made in one or two places. Then one or two small holes are drilled into the skull. An electrode is inserted through the hole and gently pushed deep into the brain. The outer ends of the electrodes are later attached to the skull, beneath the scalp.

Just before the electrodes reach the target location, the anesthesia is stopped and the patient wakes up. The doctors can then talk to them. That's important because the doctors need to test how effective the electrodes are. To do so, they send test signals and see whether the symptoms improve as a result. The test signals can also cause side effects, such as speech problems, muscle cramps or tingling in the patient’s hands. Depending on the reaction, the electrodes are moved to a different place until the best position is found.

Step 2: Implanting the pacemaker

The pacemaker is implanted under the skin – usually just under the collarbone – using general anesthesia. Then the thin connecting cables are pushed along under the skin until they reach the electrodes, to which they are then connected.

It is usually possible to implant both the pacemaker and the electrode(s) on the same day. In some hospitals, the pacemaker is implanted one or two days later.

How is the pacemaker adjusted?

After the surgery, the patient has several appointments where the doctor adjusts the pacemaker using a special programming device. The strength of the electrical signals can be increased or decreased.

The patient is also given their own small programmer device which they can use to turn the pacemaker on and off themselves, and adjust the settings to a certain extent too. The electrodes and pacemaker only cause slight restrictions in everyday life. But you should avoid sports that may involve your head being struck or moved with force. Although some people can feel the pacemaker under the skin near their collarbone, most of them aren’t bothered by that.

Other technical devices normally don’t influence the pacemaker. So there’s no need to worry that the pacemaker signals will be affected by things like mobile phones or microwaves. The body scanners that are used when you go through security at airports usually aren't a problem either. But people are still generally advised to show their pacemaker identification card to the security staff. Then the security check can be done by hand or using a metal detector instead.

Treatments or examinations that involve the use of strong electromagnetic fields aren’t (fully) possible in people who have a pacemaker, though. These include things like magnetic resonance imaging (MRI scans), which can only be done in specialized centers, and only in people who have modern pacemakers. Treatments that use deep heat (diathermy), such as ultrasound therapy, should also generally be avoided.

How effective is DBS in Parkinson's disease?

Studies have shown that deep brain stimulation can relieve the symptoms of Parkinson's disease. Both stiffness and involuntary movements are reduced, leading to an improvement in quality of life and independence. For instance, it might become easier to do everyday activities like washing yourself or cooking, and it may be possible to take up certain hobbies again. DBS can reduce tremors (shaking), which makes the illness less visible to others and can be a great relief. But this treatment doesn’t stop the illness from progressing, so the symptoms might increase again after some time.

Deep brain stimulation can't replace medication. But it can reduce the dose needed, which reduces the side effects too.

DBS has little or no effect on speech and memory problems, though. It takes a few weeks or months to adjust the pacemaker properly.

Up until now, deep brain stimulation surgery has mainly been done in people who have advanced Parkinson's disease, and only if their medication hardly helps anymore. But recent studies have suggested that this treatment can help to reduce the symptoms of Parkinson's disease at an earlier stage, too.

What are the side effects of brain stimulation?

Side effects and complications can occur as a result of the surgery, as well as later when using the pacemaker.

Surgery-related complications

Bleeding in the brain occurs in about 2 out of 100 people. The bleeding may be mild or severe. It is estimated that this surgery leads to permanent complications such as paralysis or speech problems in about 1 in 100 people.

After surgery, there may be problems with the implanted electrodes and pacemaker. For instance, an electrode might slip out of place, the pacemaker may pause, and inflammations or skin irritation may occur. These problems sometimes go away on their own, but further treatment might be needed (e.g. an electrode might have to be replaced). They occurred in about 5 to 20 out of 100 patients in the studies.

Side effects of brain stimulation

Deep brain stimulation sometimes leads to changes in behavior, such as increased motivation, mood swings, or even depression. Other possible side effects include trouble with movements such as walking, balance problems, slurred speech and temporary confusion. They often go away again by adjusting the pacemaker settings or medication. But these problems are sometimes caused by the Parkinson’s disease itself. In order to determine whether they are normal symptoms of the disease or side effects of brain stimulation, a thorough medical examination is needed.

Deep brain stimulation can also affect your feelings, relationships with others, and your family life. Some of these effects are positive, but they may also lead to difficult situations or conflicts. Then professional psychological support can help.

If the side effects are too distressing, the brain pacemaker can be removed again.

What happens after the surgery?

After the surgery, you stay in the hospital for about 10 days. You then go to a rehabilitation clinic. During your stay there, the pacemaker settings are adjusted until the Parkinson’s disease symptoms have been reduced as much as possible. The medication is usually already adjusted then too. The rehabilitation treatment also includes things like movement therapy and relaxation techniques.

Strenous physical activities should be avoided in the first few weeks after the surgery. You shouldn’t go swimming or take a bath either, because that could affect the wound-healing process.

The follow-up care also includes regular check-ups: You have an appointment every three to six months to see whether the Parkinson's disease is progressing and how well the pacemaker is working. The battery inside the pacemaker might have to be replaced after three to five years. This can be done through a small cut in the skin after numbing the area. The electrodes in the brain don’t have to be replaced for this reason. There are also devices that don't need batteries. Some can be recharged every week using a recharger.

People who have a brain pacemaker are given a special pacemaker identification card which they should carry on them at all times. It’s also important to tell medical professionals (e.g. doctors, nurses and physical therapists) that you have a brain pacemaker.