What is deep brain stimulation and what can it be used to treat?
Deep brain stimulation refers to the insertion of electrodes into the center of the brain and the influencing of nerve cells with an electric current.
The treatment is “deep” because the target structures are often 10 or 12 cm away from the surface of the brain. For electrical stimulation, the electrodes are connected to a pulse generator via cables that are implanted invisibly under the skin. This is also called a “brain pacemaker”, “pulse generator” or simply “battery”. This device is comparable to a pacemaker, only usually somewhat larger. In addition to the actual battery, it also contains a computer that can control the stimulation completely independently. The entire system can be read out and programmed from the outside, either by a patient programming device (similar to a cell phone) or a special tablet computer, which can connect to the pulse generator by radio.
The main reasons for deep brain stimulation are Parkinson’s disease, tremor and dystonia. Several hundred thousand people worldwide have already been treated with this therapy. Since the entire brain essentially functions on the basis of electricity, the theoretical possibilities of this therapy method are of course even greater. New treatments for other diseases are therefore regularly developed and tested in studies.
At our center, for example, we regularly use deep brain stimulation to treat the most severe treatment-resistant cases of epilepsy, chronic pain or psychiatric disorders such as severe depression, obsessive-compulsive disorder or Gilles-dela-Tourette syndrome. For such “new” indications, however, it must be carefully examined in each individual case whether the risks and high treatment costs are justified and whether health insurance will cover the costs.
However, the treatment of Parkinson’s, tremor and dystonia are part of the compulsory catalog in Switzerland and are fully covered in all cases, minus the deductible agreed with the insurer.
What side effects can occur?
Escalation therapies Side effects that can result from unwanted stimulation of neighboring structures include a speech disorder, cramping (independent of the actual dystonia), tingling or sensory disturbances or a visual disturbance. In practice, however, the most significant symptom is a slowing of movements that is reminiscent of Parkinson’s disease. This mainly affects walking: This can lead to so-called “freezing”, i.e. the feet “sticking” to the ground, especially when walking or turning.
As is always the case with deep brain stimulation, these side effects are reversible, i.e. they can be reversed by changing the stimulation parameters. The problem with the “Parkinson’s side effect” is that the site where the side effect occurs is usually also the site where the best dystonia control can be achieved. So sometimes you have to look for a compromise: As good dystonia control as possible – and as few “Parkinson’s side effects” as possible.
The implants are all concealed under the skin and are not visible from the outside or, depending on the thickness of the patient’s subcutaneous fatty tissue, are only visible with difficulty. The pulse generator can be implanted either on the left or right and on the abdomen or chest. In order to prevent the implants from interfering, for example, when recording an ECG or during treatments in the heart area, we now generally recommend implanting the pulse generator on the right side.
Examinations before and after the operation
In order to select the best possible treatment for patients and for rigorous quality control, various examinations are required before the operation and six months afterwards. The aim of the preliminary examinations is to ensure that the indication for treatment is correct and that patients have the best possible chance of the best possible outcome with as few side effects and complications as possible. The follow-up examinations are used for quality assurance and systematic therapy optimization.
We are also obliged to carry out these examinations, as they also follow the guidelines of the Federal Office of Public Health. Patients also make this commitment when they undergo deep brain stimulation. The preliminary and follow-up examinations differ slightly for the various treatment indications and are listed separately above.
The operation
Before the operation, Aspirin® (ASA/acetylsalicylic acid) and other blood-thinning medication (e.g. Marcoumar®, Xarelto®, Eliquis®, Pradaxa®, Lixiana®) must be completely discontinued in good time in accordance with the neurosurgeon’s instructions.
Aspirin®, for example, must be discontinued seven days before the procedure. This means that there is a certain risk that the event against which the medication should have provided protection (e.g. stroke, etc.) will occur during the period without a protective effect. We look at this very individually and assess the risk. It may be necessary to bridge the time until the operation with another short-acting blood-thinning medication, for example with Fragmin® injections.
It is also important to ensure that you do not “accidentally” take a blood-thinning medication. For example, many people take Aspirin® for pain or mixed into a cold remedy – and are not even aware of its blood-thinning effect. If a patient takes even one tablet of Aspirin® in the week before the operation, the operation must be postponed due to the increased risk of bleeding.
Other possible medication changes depend on the underlying disease being treated. Depending on the severity of the Parkinson’s symptoms, the Parkinson’s medication must be paused on the day of the operation. If a patient is taking too many different, even long-acting Parkinson’s medications, they are switched to a short-acting dopamine preparation beforehand – similar to the previous levodopa test. We inform patients in advance about how the changeover should be carried out. If you have any problems or questions, you can contact us at any time.
On the morning of the day of the operation, we anesthetize the scalp by injecting a local anesthetic in several places around the head under light sedation.
We then attach a stereotactic frame to the skull with four screws through the skin. This procedure is not painful thanks to prior anesthesia. The frame remains attached to the head until the end of the operation, i.e. for about four hours.
In the operating room, the hair is carefully parted and only minimally shaved in the area of the operation. After careful disinfection and sterile draping, the actual operation begins. A neurosurgical drill is used to make a 14 mm diameter opening in the skull. This is not painful, takes a few seconds and is perceived as a loud noise due to the direct transmission of the vibrations of the device to the hearing organs in the skull. One or more fine electrodes are now inserted through this opening to the planned target point.
The recording of brain waves from the tip of the electrode allows the neurologist and neurophysiologist also present to check and optimize the accuracy of the procedure. The signal indicates whether the electrode is in the correct core area.
During a test stimulation, the neurologist checks the effectiveness of the stimulation and the occurrence of any side effects. The aim is to achieve a good effect with little stimulation, while side effects should only occur with strong stimulation. This allows greater scope for programming the stimulator later on. As soon as the results are satisfactory, the neurosurgeon replaces the test electrode with an electrode with several contacts at the tip, which should remain permanently in the target region. It is attached to the bone and the drill hole is closed at the same time.
Immediately afterwards, the entire procedure is repeated on the other side of the head. A computer tomography of the head finally confirms the correct electrode position on both sides so that we can remove the stereotactic frame.
Overall, the procedure itself is not painful, only the drilling of the holes in the skull is very loud. Most patients find lying down for long periods with their head fixed in position the most uncomfortable aspect of the operation. This applies in particular to Parkinson’s patients who are in “medication OFF”. Increased Parkinson’s symptoms such as leg cramps or pronounced tremors at rest can then be a problem.
Thanks to our many years of experience, we can deal with these symptoms. Our nursing staff, who get to know the patients in advance, play an important role here. Of course, anesthesia is also present at all times. If necessary, she will provide light sedation using an intravenous drug. In extreme cases, general anesthesia can also be administered. After inserting the electrodes, the next step is to insert the pulse generator. General anesthesia is required for this. The procedure takes another 30 minutes.
Awake or under anesthesia?
The operation can always be performed under anesthesia or awake. Different centers take different approaches here. However, most neurosurgeons today prefer to operate while the patient is awake because this procedure allows the effects and side effects of stimulation to be tested during the operation and the implantation to be optimized accordingly.
At our center, the implantation of electrodes in the “Parkinson’s nucleus” for Parkinson’s disease and in the “tremor nucleus” for tremor diseases is carried out while the patient is awake as standard, as this allows greater safety with regard to effects and side effects to be achieved. The following two factors are decisive for this:
Firstly, brain waves can be better recorded from the target area when the patient is awake, as they are not influenced by anesthetics. This allows the target region of the Parkinson’s nucleus to be defined more precisely.
Secondly, a test stimulation in the waking state enables an estimation of the entire so-called therapeutic window for a specific stimulation site.
We see whether and with how much current the complaints are alleviated – ideally with as little current as necessary – or with how much current which side effects occur due to unwanted co-stimulation of neighboring structures – this should ideally not occur at all or only with a lot of current. We call this range between the lowest possible effect threshold and the highest possible side effect threshold the therapeutic window, which is ideally very wide. This is specific to a certain stimulation site or a certain electrode position. If the test stimulation reveals that the therapeutic window is not optimal, the position of the electrodes can be corrected.
This is particularly important if the microelectrode derivation shows that several points in the target location are potentially suitable. This allows us to compare them during the operation and select the best location.
In a study from our clinic, we found that this procedure led to a more optimal electrode position in 1 out of 9 patients who underwent surgery. Other centers that primarily operate under general anesthesia also test possible side effects with the help of muscle derivatives in sleeping patients. However, this procedure is relatively crude because minor side effects may not be recorded. In addition, the effect threshold is not investigated at all, so that the therapeutic window remains in the dark. It also increases the chance of achieving the best possible result in the long term. In this respect, the advantages of greater security and better opportunities generally clearly outweigh the disadvantages of greater expense and more work. This is particularly true because our patients are well prepared and accompanied during the awake operation and – if necessary or desired – receive short-acting sedative medication during the operation.
Other implantations, such as implantations in the “hypermovement nucleus” globus pallidus internus or deep brain stimulation for epilepsy, are usually performed under anesthesia because testing while awake is not very useful. We always take the patient’s wishes into account and discuss the advantages and disadvantages of both procedures together. This means that we can also perform operations in the Parkinson’s core under general anesthesia, for example, if the patient is basically suitable for this, but would not tolerate an awake operation despite all the preparation and support.
After the operation
After electrode implantation, patients initially remain in inpatient treatment. The wounds are checked and after three days patients are allowed to shower and wash their hair again. An X-ray check of the entire system is carried out. Some – but not all – patients notice a positive effect on their symptoms after electrode implantation, even if there is little or no current. This effect is caused by the small amount of tissue damage caused by the placement of the electrodes in the core area (hence the “placement effect”).
A few days after the operation, the stimulation is switched on and a so-called monopolar test is carried out, whereby all eight poles are tested so that the best possible contact can be confirmed and possible side effects can be documented. The stimulation is then slowly increased step by step and the medication is adjusted accordingly. Depending on the underlying disease and state of health, the patient is transferred to a rehabilitation clinic around seven to ten days after the operation (obligatory in the case of Parkinson’s disease, possibly in the case of tremor and dystonia) or is transferred home.
Surgical complications
Deep brain stimulation is one of the procedures with the lowest complication rate in neurosurgery. All the possible consequences that we list here are very rare. Nevertheless, it is important to be aware that serious complications can also occur during this operation and that there is a risk of severe neurological disorders or even death.
- Persistent pain or fluid accumulation at the implantation site of the pacemaker.
- Infections and bacterial colonization of electrodes and pacemakers occur in up to 3% of patients during the first year after implantation and necessitate temporary removal of the system and treatment with antibiotics.
- The insertion of the electrode pushes the brain tissue aside without causing significant injury. Nevertheless, in 1-2% of cases, injury to small blood vessels can cause cerebral hemorrhages. Most such hemorrhages are small and do not cause any symptoms, but they can rarely be large or critical and cause symptoms ranging from paralysis and speech disorders to death.
- Seizures can occur in up to 1-3% of cases.
- General medical complications, such as a blood clot in the lung, are seen in 1%. A so-called “delirium” (German term “Durchgangssyndrom”) can also occur after an operation. Those affected are mentally and / or psychologically altered: They are slowed down or driven. They may be “confused” and have difficulty concentrating or remembering the content of the conversation. Strange behavior” or even hallucinations are also possible. It is important to understand that this delirium is due to the operation and not to the stimulation. Patients usually recover completely from this condition – but it can take some time. We know that the older and sicker patients are, the higher the risk of delirium and the more severely their higher brain functions are impaired. The risk of delirium exists not only with deep brain stimulation but with any type of surgery; and even general anesthesia alone can trigger delirium.
Side effects
Stimulation can cause side effects if tissue in the immediate vicinity of the target area is stimulated unintentionally. Deep brain stimulation is reversible, i.e. the current can be changed so that the side effects do not occur. Alternatively, other contacts can be controlled or other stimulation parameters can be used. The side effects result from the core areas that are stimulated.
The treatment parameters can be changed at any time by reprogramming and have different consequences for the stimulation. One strategy to counteract side effects is directional stimulation.
In the latest generation of stimulation electrodes, the contacts are not only arranged in a ring shape, but are also partially segmented. This allows us to direct a stimulation field in a specific direction, e.g. away from the inner capsule on the side. This can be important if, for example, the electrode is not 100% optimally positioned or the target structure is very slim.
Sometimes it is necessary to reach a compromise:
For example, it must be weighed up whether the maximum treatment of the symptoms is desired at the expense of a certain side effect – or whether the setting should be chosen so that no side effects occur. In return, you may have to put up with certain symptoms or take more medication.
Brain sensing
Classically, the device stimulates continuously, 24 hours a day, and does not adapt to brain activity. New developments now also allow so-called “sensing”. This is the measurement of brain activity by the stimulator. This can offer decisive advantages, such as only stimulating when symptoms are present and necessary. This is a typical scenario in Parkinson’s disease as there are good and bad phases.
This may save battery power in the future. It is also conceivable that side effects can be reduced. This new technology is currently being tested worldwide, but is essentially already available.
By reading out the stimulator, we can already see how many bad and how many good phases there have been since the last check-up. This can be a valuable addition to the conversation, especially for people with Parkinson’s.
Monitoring at home
Some providers implement the stimulator in a network that can be accessed by both patients and the doctors treating them. In future, this will increasingly allow solutions to be found without the need for a consultation in hospital.
The settings can be read out remotely by the attending physician and allow conclusions to be drawn about the stimulation and its effect. Battery replacement and rechargeable neurostimulators The pulse generators have either a non-rechargeable (“permanent cell”, PC) or a battery that can be recharged by induction (“rechargeable cell”, RC).
The service life of non-rechargeable stimulators is normally between three and five years, depending on individual power consumption. In the case of dystonia and epilepsy, experience has shown that quite strong stimulation is used, which is why the power consumption is higher and the battery life is shorter. If a battery is exhausted, the patient receives a message from the patient programmer informing him or her of the remaining service life. If this is less than three months, the patient will be asked to contact the hospital to plan the pulse generator replacement.
This change is usually performed under local anesthesia and takes about ten minutes. The rechargeable stimulators can be operated for 15 years without changing and are slightly smaller than the non-rechargeable stimulators. To do this, they have to be charged daily or at least every few days by induction. When traveling, for example, this means that the charger must always be carried with you. Most patients therefore choose non-rechargeable systems, as this eliminates the need to regularly recharge the batteries and they do not have to constantly think about deep brain stimulation. If the service life proves to be very short in an individual case, a rechargeable stimulator can be used when changing.
Living with deep brain stimulation (DBS)
Doing sport
In principle, DBS patients can take part in most sports – including water sports. However, it should be noted that a small proportion of Parkinson’s sufferers with deep brain stimulation in the “Parkinson’s core” lose the ability to swim, ski or play golf after the operation. Caution is therefore advised when going into deep water or onto the ski slope for the first time.
In addition, strong forces acting on the body can cause the leads to break or the stimulator to malfunction. All contact sports such as boxing or karate are risky in this respect, as is rifle shooting because of the recoil. Deep-sea diving with THS is also not recommended.
Medical examinations
Most medical examinations and treatment procedures are still possible. Only magnetic resonance imaging (MRI) examinations are only possible within certain limits due to the strong electromagnetic fields generated. The latest THS devices allow imaging with MR devices operating at a strength of 1.5 or 3 Tesla. If in doubt, the situation must be clarified with the attending radiologist.
During the examination, certain settings must be set on the stimulator. Patients can do this independently with his patient programming device. You will receive an implant card from us with the necessary information.
Physical therapies for local heating that work according to the high-frequency principle (diathermy) are dangerous and must not be used under any circumstances.
Bipolar cauterization is required during operations. Problems can also occur when recording an electrocardiogram (ECG) if the high-frequency electrical impulses of the DBS system interfere with the ECG image. Briefly switching off the stimulator or activating an MRI or ECG mode solves the problem.
Travel
Traveling is possible. At airports, staff must be made aware of the stimulator by means of an appropriate implant badge. There is no danger when passing through the control system. Checking with hand-held devices or metal detectors, on the other hand, is not recommended for safety reasons. The patient programmer and medication should always be carried in your hand luggage.
In principle, driving a vehicle in the presence of deep brain stimulation is not prohibited and there is no medical reason to prohibit it per se. However, in the first few months after the procedure and in principle until the stimulation and medication settings have been satisfactorily resolved, motorized vehicles should not be driven. This is particularly true for Parkinson’s patients, where the adjustment is most complex. As a standard, the patient is not fit to drive for at least three months after the operation.
After this time, we carry out a memory and concentration test during the consultation and assess the patient’s motor skills. Depending on the result, the patient’s fitness to drive is then released again – or the driving ban is extended until a new, detailed neuropsychological test is carried out six months after the operation.
