Deep brain stimulation (DBS) is an advanced surgical treatment that is indicated mainly for three movement disorders: Parkinson’s disease, dystonia, and essential tremor, although there is also a human device exception (HDE), for obsessive-compulsive disorder.
The rationale for the use of deep brain stimulation is based on the inability of medical treatment in many cases to satisfy the needs of these patients, though it can be different for different diseases. Particularly in Parkinson’s disease, we can be very successful for several years pharmacologially controling the motor symptoms, the tremor, rigidity, and bradykinesia of our patients, But after a number of years the effectiveness of medication like levodopa or dopaminergic medication can literally fade. It can also be complicated by a number of problems like fluctuations of the response to levodopa or dyskinesias. And in these cases, if the patient has now developed cognitive decline or other problems that would contraindicate surgery, deep brain stimulation becomes sometimes a miraculous remedy for their problems.
The problems that we have to face in the short-term with DBS therapy are mainly the setting of the appropriate stimulation parameters. Implanting these electrodes either in the subthalamic nucleus or the globus pallidus is not enough to obtain the control of Parkinson’s symptoms. We have to train physicians and health care providers to properly program these devices to the actual settings that will benefit patients.
In the short-term we sometimes have to work hard to find exactly the electrical settings that will stop the tremor and will help these patients relieve their stiffness or their slowness of movements. This might take as little as a couple of hours or as long as three months, and it might take a few back and forths in the clinic for patients.
We have developed over the years some reliable paradigms. This entails going systematically through the settings that we already know work in the clinic, and if they don’t work,then we have to troubleshoot and come up with creative alternatives.
Once we have found the right parameters and we have adjusted the medications accordingly, usually over a number of months, we don’t have to do many adjustments to these settings for a number of years in the best-case scenario.
There is an intermediate time in which stimulation works pretty well and actually, as I like to tell my patients, turns the clock back for them to a time in which taking the medication was enough to relieve their symptoms. But over the long-term, sometimes we have to face other problems that may come up due to the progression of the disease, particularly for Parkinson’s disease and sometimes for essential tremor. Problems like speech difficulties or gait and balance abnormalities, and cognitive declines might complicate not necessarily the effect of DBS, but the quality of life of patients. In the case of dystonia, stimulation tends to hold its benefits longer in time.
Managing expectations of patients who are good candidates for DBS is also very important, because despite providing sometimes exceptional improvement for their symptoms, DBS is not a cure. It is not going to completely relieve all the symptoms of Parkinson’s disease and eliminate, for example, the need to take medications. This makes it extremely important for the neurologist to go through the expected benefits, as well as the possible side effects and the possible complications that are associated with brain surgery, in order to make sure that expectations are reasonable. This allows us to avoid the paradox of having a patient that dramatically improved their symptoms but is greatly disappointed because he or she is not completely cured of their disease.
Michele Tagliati, MD is Vice Chairman of Neurology and Director of the Movement Disorder Program at Cedars-Sinai Medical Center in Los Angeles.