In the decades since deep brain stimulation surgery (DBS) was first used to treat Parkinson’s symptoms, over 80,000 people worldwide have received DBS. Each year, about 10,000 DBS operations are conducted on people with Parkinson’s disease. Canada is a leader in this area, with neurologists and neurosurgeons coming here from all over the world to train in how to do the procedure. We have asked distinguished neurosurgeon Dr. Andres Lozano to give us an overview of DBS.
What is deep brain stimulation (DBS)?
DBS is the introduction of stimulating electrodes into a specific area of the brain to treat the symptoms of Parkinson’s disease.
Which areas of the brain are targeted?
If you imagine a loop in the brain with several stops along the loop, there are at least three targets we can choose along this circuit, depending on the Parkinson’s symptom. For tremor, for example, the thalamus is the best target. For rigidity and other motor symptoms, the subthalamic nucleus and globus pallidus appear to be equivalent.
Who is the best candidate?
The symptoms that respond very well to DBS surgery are motor fluctuations, tremor, rigidity and slow movement. So if people are not getting the most benefit from their levodopa therapy, for example, the medications are not lasting as long and people are experiencing on/off fluctuations through the day, or if tremor, rigidity and slow movement are getting worse, then it may be time to consider DBS. Roughly 15% of patients with Parkinson’s could benefit from DBS surgery. It is a major plus if the person has strong family support.
Are there people unsuited to DBS?
Some people with Parkinson’s will be excluded if they have another medical condition that makes them less likely to benefit; for example, significant cognitive problems, psychiatric problems or a condition requiring them to have many MRI images throughout their lives. The safety of MRI has not been fully established yet for patients with implants.
Is age a factor?
With age, patients become less responsive to both drugs and surgery and the benefit-to-risk ratio becomes less favourable, so we are less enthusiastic about offering DBS surgery to people over 70. Since older people also have much more medical co-morbidity, such as heart disease, we think very carefully before offering DBS to people at an advanced age.
Is consideration being given to offering DBS earlier in Parkinson’s?
Indeed. There can be opportunity costs associated with waiting. For example, people may have to give up their employment or may decide to decline a promotion because of Parkinson’s and its rate of progression. Surgery may be able to help here. There is a general trend to offer surgery earlier and earlier. Some studies are specifically looking at using DBS within five years of onset instead of the average 12 years after diagnosis. This, of course, has to be balanced with the small, but not absent, risk of the surgical procedure and treatment.
What does the procedure involve?
We can put patients to sleep if they are anxious, but the procedure is best done with the patient awake so we can select a better spot for the electrodes. Before the procedure, patients have an MRI scan of the brain. Then a frame is placed on the patient’s head. During the surgery, we make two openings in the skull and pass the electrodes through. Once the electrodes are in place, we put in a battery in the chest, underneath the collarbone. Next, we tunnel a cable from the electrodes in the head to the battery in the chest – it goes underneath the skin behind the ear, down the neck, over the collarbone, and into the chest. Patients usually go to sleep for that part. We then connect the battery to the electrodes. Using a device similar to a TV remote control, we point a remote controller through the skin to the implanted battery to change the settings and control how much current is delivered to the brain.
Does the device stay on 24-7?
Yes. When the brain is missing dopamine, certain areas of the brain malfunction or misfire. That misfiring is transmitted in the circuits of the brain and causes a person to have tremor, not be able to initiate movement and so on. With DBS, we are able to block or stop that misfiring so the brain can work in a more normal way.
What are the risks of DBS surgery?
Every time you operate on the brain, something bad could happen. We tell patients that there is a 1-2% risk of serious complication relating to the surgery. The worst that could happen is there could be bleeding in the brain when the electrodes are introduced. It happens in less than one in 100 cases but is potentially very serious. Next, there could be problems when the device is turned on and off; there could be a side-effect from the stimulation but this can be controlled by turning the machine down or off. Thirdly, the hardware could break down, the batteries could wear out and the person could get an infection. Those are the three kinds of at-risk effects we see: risks relating to surgery, stimulation and hardware.
After surgery, what kind of maintenance is required?
Initially, people come in for three or four sessions of programming until we find the best stimulation parameters. After that, they have a check-up every six to 12 months. We were using batteries that last four to five years but now we also have the possibility of inserting a rechargeable battery that requires one hour of recharging per week and lasts eight or nine years instead of five.
How long do the benefits of the surgery last?
Parkinson’s is a multi-faceted illness. For symptoms such as motor fluctuations, tremor and rigidity, the benefits will last forever. However, because Parkinson’s is a progressive illness, other symptoms will appear; for example, cognitive decline, speech problems, balance problems, problems with bladder and sexual function. These will continue with or without medication, with or without surgery. So some symptoms are very well treated forever and others are not influenced by the surgery.
In what new directions is DBS heading?
My research team and others are looking at ways to address the difficult non-dopamine-responsive symptoms such as cognitive problems, depression and walking difficulties. We’re looking to see if we may be able to go into different areas of the brain to treat those. DBS is also being studied for its potential to treat other neurological conditions and psychiatric disorders.
Deep Brain Stimulation for Parkinson Disease: An Expert Consensus and Review of Key Issues
(Abstract of article published in Archives of Neurology, October 11, 2010 Online edition.)
Beware the miracle cure
(Oct. 23, 2010 National Post article on deep-brain stimulation.)