Surgery & tremor
What is DBS?
A patient undergoes surgery to implant a medical device, usually called a Kinetra™. This is similar to a cardiac pacemaker. It is connected to electrodes which are precisely positioned in both sides of the brain. Continuous stimulation through these electrodes, blocks the signals which cause the physical symptoms of the disease. The aim of the treatment is for patients to regain control over their movement. All the individual components of the DBS system are implanted underneath the skin so they are barely visible; the Kinetra is implanted underneath the skin usually on the chest wall or occasionally in the lower abdominal wall. The surgery can be described as unilateral (one-sided) if the patient has tremor on one side only; or bilateral (two-sided) if the tremor is on both sides.
How does it work?
The electrodes are implanted into areas of the brain such as the thalamus or Zona Incerta dependent on the clinical team’s choice. The minute electrical currents which are carefully controlled have a beneficial effect on the tremor by reducing its amplitude. It is not known exactly how it all works. The thalamus is an area of the brain which is extensively involved in controlling and coordinating movement such as tremor. Stimulation of this area is also known as thalamic stimulation.
What does the operation involve?
Before a patient is accepted for surgery, a detailed medical history is taken and they will have to undergo a series of assessments, often including neuropsychological tests. This is done to ensure that DBS is the best option for the patient. A video of the patient can also be made so that a patient's movement can be compared after surgery. Once the procedure and process has been fully discussed with the patient, and all the implications understood, the patient is offered the treatment.
Next the patient undergoes a series of brain scans, usually both MRI and CT, which allows the surgeon to decide exactly where to place the electrodes in the thalamus. Before the scans, a lightweight frame will be fixed to the patient's skull to prevent movement within the scanner. They are usually performed under a general anaesthetic. These scans help the team to plan the route and the final position the wire(s) will take, avoiding other important areas of the brain next to where the wire(s) need to be.
The wire(s) are then usually implanted in the awake patient. The patient’s skin receives a local anaesthetic so that they do not feel pain. The brain containing no pain receptors itself does not feel pain.
One or two small burr holes are made on either side of the skull. The electrodes are passed through these, down to the target area in the thalamus. There are four in-line electrodes at the end of a DBS lead. The aim is to introduce as many as possible of them within the depth and volume of the target area. The exact placement for the electrodes is then decided from the scans and other tests carried out in the operating theatre. When the electrodes are in the right place, the holes are closed and the other end of the DBS™ leads (not containing the electrodes) are connected individually to one or two extension cables. The extension cable(s) are tunnelled underneath the skin behind the ear, on the same side of the neck to the chest wall. The extension(s) are connected to the Kinetra stimulator which is then put into a small 'pocket' made under the skin. All the wounds are closed and dressed.
The patient usually then has another scan to check that the electrode(s) are in exactly the right place. They are transferred to recovery for a brief period of observation before being transferred onto a neurosurgical or neurological ward.
N.B. The Kinetra may be placed on the lower abdominal wall in children and in female patients for cosmetic reasons
What happens next depends on the centre where the surgery takes place. The stimulator may be programmed with an initial set of electrical parameters, either straight away or within a few days. A physician programmer uses radio waves to 'talk' to the implanted Kinetra. This is not painful or invasive. The physician can then adjust many variables of the stimulation, including which electrodes are selected, to ensure that the best effect is achieved. It is usual for the patient to need many adjustments over the next few months to optimise the therapy.
How long will I be in hospital?
The amount of time that you have to remain in hospital depends on the centre implanting the device. Patients are usually admitted for further tests, one to three days before surgery. The length of the operation also depends on the technique used by each centre, but it often lasts between 3-6 hours from start to finish.
As long as the electrodes are accurately placed, without complications, the recovery period usually lasts from between 3 to 5 days. The patient is then discharged with clear instructions about the amount of activity that is safe, and with a series of planned outpatient appointments.
How long will it take to work?
Patients who have DBS for Essential tremor or other tremors often see improvements immediately or within a few hours. Patience is often essential to optimise the therapy requiring several programming sessions. Everyone is different and so every person responds differently to stimulation.
For patients to see improvements, a number of things must occur. Firstly the electrode(s) must be accurately placed. Secondly, using the physician programmer a member of the clinical team must also find the optimum stimulation settings. Finally any other medical considerations have to be taken into account. The best combination may not be achieved the first time the Kinetra is activated and programmed after surgery. Often the effect of the surgery itself causes the tremor to lessen or stop, this is called a micro-lesion effect. This effect needs to vanish to allow the clinical effects of the stimulation to be determined, this may take a few days. Patients should expect that they will have to undergo frequent programming sessions to get the best clinical improvement for the symptoms being targeted.
What are the risks?
There are three main types of risks: those that are associated with any brain surgery; risks related to the device and having a foreign body inside you and those connected with the stimulation itself.
All neurosurgical procedures of the brain have the same degree of risk associated with having the surgery itself and the anaesthetic. There are a number of risks which relate to having the electrode(s) inserted which include but not exclusive to
1. The risk of stroke which is reported to be between 1 - 3% in the latest clinical literature
2. Intracranial haemorrhage, hemiplegia, headaches and seizures.
However, the advances in MRI scanning technology have helped the neurosurgical teams to implant the electrode(s) into a precise position via the best routes, avoiding major blood vessels. Many centres state that their adverse events are lower than the published clinical literature.
Having the stimulator hardware implanted may carry a small risk of infection. Skin may breakdown over the Kinetra pulse generator or where the lead(s) exit from the burr hole(s). There may be a small risk of components of the stimulator failing, for example a DBS lead may break which would mean that the therapy would have to be stopped until the problem was resolved. If the stimulation is stopped, this may cause the symptoms to temporarily worsen again. This is known as the ‘rebound effect’ which lasts until the component is replaced.
The thalamus is near areas of the brain which do not coordinate movement. Stimulating one of these areas by mistake can cause adverse events such as speech disturbances, dyskinetic (flailing) movements and sensory disturbances. Because the stimulator can be adjusted an infinite number of times, adverse events caused by the stimulation usually do not last and can be reduced or eliminated whilst still maintaining good tremor suppression.
What if it does not work?
There are a number of factors which significantly increase the chance of surgery being a success: Detailed patient assessment is carried out before surgery and from the assessment, medical staff have a clear selection and deselection process. The electrode(s) are precisely placed in the brain. Accuracy in targeting insures that the electrode(s) are placed in exactly the right place. The team are experts in managing patient care after the stimulator has been implanted.
Before the stimulator is implanted, the physician, patient and their family discuss what improvements can be expected for the symptoms which are being targeted allowing the setting of realistic expectations and goals. Every patient has an individual response to stimulation but published data shows an improvement in mean tremor scores & activities of daily living continuing at 6 years post-implant. In addition, many essential tremor patients are able to reduce or stop their medications post implant.
One of the benefits of DBS is that the electrode(s) do not destroy brain tissue so if it is decided that a satisfactory clinical outcome has not been achieved, the DBS system can simply be turned off or removed (explanted). You would have to have an operation under a general anaesthetic to have the stimulator removed.
How do I go about being considered for DBS?
To find out whether you are suitable for DBS, you need to be referred by your GP to a specialist neurologist, geriatrician or to the specialist implanting neurosurgeon, who has an interest or is an expert in the area of movement disorders. It is often difficult to find a specialist neurologist and you may have to look outside of the immediate area where you live. Ideally the specialist should be part of a team which includes a specialist functional neurosurgeon, neuropsychologist, anaesthetist, and specialist nurses.
There are a number of UK neurosurgical centres which are able to accept referrals as well as a number of specialist neurologists who assess patients and where appropriate, refer them to these centres. The National Tremor Foundation has a list of these specialists.
After a patient has been referred, they have to undergo a detailed selection and de-selection process. If it is decided that a patient is suitable, then the centre offering the surgery has to obtain funding and authorization from the patients GP and local primary care trust (PCT). This process can take a long time and is still not a guarantee that surgery will take place. If approved, the patient is put on a DBS neurosurgical waiting list.
Where can I get the operation?
There are many neurosurgical centres in the UK that accept referrals for patients who are considering DBS. The National Tremor Foundation has the complete list. It may be necessary for a patient to travel to a neighbouring county for surgery as there is not a centre in every county. The patient may want to take the list of centres offering the surgery with them when they go to see the GP for a referral.
How long does the recuperation take?
As long as there are no complications as a result of the surgery, patients usually stay in hospital for 3 to 5 days after the device is implanted. This may vary however, according to the different practices of each centre. Some centres are involved in clinical research programmes. These centres may ask patients whether they are willing to take part in their studies. This may involve a slightly longer stay in hospital.
After a patient is discharged from hospital, they will be given clear and precise instructions about how much activity they may do. They will also usually be given a structured outpatient appointment schedule which should be closely followed. Outpatients’ appointments are arranged to check that the wounds are healing and to assess how well the stimulation is working. Adjustments to the stimulator settings may be made at this time. After the patient is discharged from hospital, they should be able to resume normal life.
What types of tremor can be treated?
The types of tremor which respond well to DBS which are considered to be a primary indication are:
- Essential tremor
- Tremor of Parkinson’s disease
In addition, many centres report good results in tremor of multiple sclerosis
Most types of tremor respond well to DBS and include – rest tremor, postural tremor & intention tremor. There are also reports that head & voice tremor can respond well to DBS. DBS is able to lessen tremor in both the upper & lower limbs depending on the position of the electrode(s) in the thalamus.
There is no upper age limit for patients being offered surgery, as long as there is no other illness which may complicate the surgery. This would be discussed during the patient assessment.
What follow-up treatment is needed?
Adhering to the follow-up schedule provided by the implanting team is crucial to maximising the clinical efficacy of the stimulation and any adjustments of medications that maybe required.
It is important that during the first weeks, patients should watch the incision site carefully. The implanting team must be told if there is any sign of redness, soreness, pain over the incision site, (other than what would be expected after surgery) or anything else that is unusual.
During the first months after the stimulator is implanted, it will be necessary to attend an outpatients’ clinic to assess the clinical benefits of the stimulator and make any necessary adjustments to the stimulator settings. The adjustments are made by a physician programmer which uses radio waves to ‘talk’ to the stimulator. This is a painless procedure where a device is held over the stimulator. The number of outpatient appointments varies from one patient to another but eventually, the stimulator parameters plateau to provide maximum clinical effect on the symptoms being targeted. Once this stage is reached, the stimulator needs very small infrequent changes.
The stimulator is powered by a battery. The level which the stimulator is programmed at, effects how long the battery lasts. The battery life span can be checked by a physician programmer or a patient Therapy Access Controller™ (TAC). This is a small patient programmer which is given to some patients when the implanting team agrees. The TAC allows a patient to monitor the battery life and switch the device ‘on’ or ‘off’ if necessary. When the implanting team agree, this device also allows the patient to make minor adjustments to the stimulation intensity.
Once the battery is reaching its ‘end-of-life’, patients need to have a small operation. The battery is removed and then replaced with a new stimulator unit. The extension cable(s) and DBS lead(s) are not replaced at this time. This surgery usually lasts for about one hour.
After this surgery, the new stimulator which contains the fresh battery is programmed using the same settings as the previous stimulator. The patient is then discharged from hospital.
How do I get an assessment for DBS?
DBS is a complex procedure and so it is only offered to a patient who has had a detailed assessment from a multidisciplinary team, and who has not responded to, or is not suitable for, less invasive procedures. The patient needs to obtain a referral to a specialist team which has experience in movement disorders and DBS surgery. The process starts with a letter from the patient’s GP. This is sent to either the specialist neurologist or the specialist neurosurgeon, asking them to discuss DBS and whether or not this procedure is suitable for that patient. Where the person is considered to be a potential candidate, the assessment process is started. Patients often have to be referred outside of their local area because there are not many specialists in this field.
The implanting team then consider, discuss, and agree, the following issues with patients:
- All aspects of a patient’s medical history.
- The risks and potential benefits of DBS.
- The surgical procedure.
- Realistic expectations and goal setting
The Team and the patient agree which symptoms will be targeted and what success they should expect.
If, after all these things have been discussed, the patient then decides that they want to go ahead with surgery, they are put on a waiting list. During this time the implanting centre has to gain the funding for the surgery from the patient’s Primary Care Trust (PCT).
Questions to ask your doctor
Anyone considering DBS should ask many questions of the physicians who will be treating them. Here are some of the questions you might ask:
- am I a candidate for this therapy? Why? Why not?
- what are the potential risks and benefits of the therapy?
- what are the potential risks of the surgery?
- what are the side effects of the therapy? Can the side effects be controlled?
- what kinds of tests will be conducted before the surgery?
- what can I expect the day of surgery?
- how long does the surgery last? Is it painful?
- how long will I need to be hospitalised?
- will my condition improve immediately after surgery, or will it take more time?
- what precautions will I need to take after surgery?
- how often will I need to return for follow-up visits? How many programming sessions to adjust the stimulation can I expect?
- will I still need to take medication after having the DBS implanted?
Here are some other things to keep in mind when talking with physicians who provide deep brain stimulation: