Benefits and Limitations of DBS Surgery
For Parkinson's Disease
In patients with Parkinson's disease (PD), surgery is generally recommended at a time when medications cannot adequately control symptoms. Patients are most often referred for deep brain stimulation (DBS) surgery when they have experienced problems with dyskinesias (excessive involuntary movements that occur as a consequence of PD medications) and fluctuations (the effects of medications do not last long enough between doses). When there really are no further adjustments that can be made with medications because of these problems, surgery may be a way to limit complications from medications, and improve motor function. However, it is important to note that surgery will NOT work any better than medications ever did. The major benefits of DBS surgery in this case are to decrease "off" time and to reduce or eliminate dyskinesias. In addition, many patients report that their quality of life improves substantially after DBS. Medications can be gradually reduced after DBS, but this is not always the case and may depend on many factors.
Less frequently, PD patients are referred for surgery when their tremor is not adequately controlled despite multiple medication trials. In these cases, surgery may be the only way to control tremor, with even better results than with medications. Surgery is rarely used in patients who are unable to tolerate levodopa.
In PD, any motor PD symptoms (tremor, rigidity, slowness/incoordination, walking/balance problems) that do not get better with medications will generally not get better following DBS surgery. The only exception is when the surgery is being primarily done to control tremor. Additionally, DBS is NOT a cure for PD, and it probably does not slow or stop the underlying progression. Some symptoms such as balance difficulties, speech problems, swallowing difficulties, and cognitive decline develop or worsen as PD progresses, and cannot be addressed with DBS adjustment. Finally, the non-motor complications of PD, such as depression, problems with thinking or memory, constipation, urinary changes or pain, are also not likely to be markedly improved by DBS. It is absolutely imperative that patients have realistic expectations and a clear understanding about the anticipated outcomes and potential risks before consenting to the procedure.
Essential Tremor and Dystonia
Patients with essential tremor (ET) or dystonia (including cervical dystonia or torticollis) should expect that their tremors or involuntary muscle contractions or postures are better controlled than with medications alone. However, there may be several factors that influence how well this can be done, including individual patient characteristics, duration of disease, and distribution of symptoms. DBS surgery will not help with balance problems or other non-movement related features.
Tremors of the head or trunk are more difficult to treat but can improve.
For Tourette Syndrome
Patients undergoing treatment for Tourette syndrome (TS) should be aware that DBS in this condition is still under investigation and there are no guarantees about the outcome. In our experience to date, tics can substantially improve, but they do not go away completely. There may also be some improvements in co-morbidities such as obsessive-compulsive disorder and attention deficit disorder. Surgery is generally reserved for severe cases in which all medical and psychological therapies have been exhausted and unsuccessful.
Risks Associated with DBS Surgery
There are potential risks associated with any brain surgery, including infection, intracerebral bleeding, leaks of the fluid surrounding the brain (cerebrospinal fluid), strokes, headaches, seizures, weakness, sensory changes, technical problems, wound healing problems, disfiguring scars, prolonged hospitalization, and the need for additional surgery. Additionally, there may be potential risks associated with receiving anesthesia. The percentage of patients who report or experience these complications is low, but may be different according to the surgeon who is performing the procedure. It is a good idea for patients to discuss individual complications rates with their neurosurgeon.
In addition, there may be potential risks related to the programming of the DBS device, which begins a couple of weeks after the surgical process is complete. When making adjustments to the DBS, there may be immediate short-lived side effects such as tingling, tightening sensations, visual changes or speech problems. Much of the time these may be eliminated by further DBS adjustment. However, certain effects may not become apparent until hours or days after the adjustment. These may include any of the above symptoms but also mood or behavior changes, involuntary movements, worsening of the underlying symptoms, or walking and balance problems, including falls. Patients undergoing DBS for ET, especially if the procedure is done on both sides of the brain, are particularly prone to developing problems with speech or gait/balance changes. It is important that these problems are communicated to the neurologist if they occur so that they can be rectified as soon as possible. There may be several ways that these problems can be addressed, but it is possible that the changes required to minimize such side effects will lead to less symptom control. Newer DBS hardware has recently become available that may provide your neurologist with greater programming options to manage your symptoms with fewer risks of side effects.
Less commonly, and in the long term, there may be device complications that include loss of effect, unexpected side effects, fracture or breakage of the wiring, change of position of the electrode within the brain, or infection. Some of these problems, if they develop, may require removal of the device or portions of the device.