By Dr. James McInerney
Deep brain stimulators are powerful devices that were developed to allow for the precise treatment of brain disorders such as Parkinson’s disease or Essential Tremor in a minimally invasive, yet dramatic, way.
Historically, there was no treatment for these diseases prior to the past century. Parkinson’s disease, for example, has been a problem for as long as humans have existed and yet we have only even named this disease in the past 200 years. The first treatment was surgical and came about in the early 20th century. This involved injuring (lesioning) a precise area of the brain. This led to improvement in tremors, and these lesions were the standard treatment until the first medications for Parkinson’s disease were discovered.
These procedures evolved into stimulation through the efforts of centers in Europe in the 1980s. These centers began using stimulation as a means of mimicking the effects seen with the lesions, without being destructive. It turned out these stimulation techniques were also effective at controlling symptoms, and deep brain stimulation was FDA approved and introduced for use in the United States in 1998. In fact, stimulation has worked so well against features of Parkinson’s disease that studies have been done to compare stimulation against best medical therapy. A study reported in Europe and a similar study reported in the Journal of American Medical Association here in the United States demonstrated that stimulation is not only better than the best medical therapy, but it actually allows for improvement in the symptoms, which no previous study has been able to demonstrate with any other therapeutic intervention for Parkinson’s disease.
Implanting these devices requires a great deal of preparation and planning but actually very little surgery. The surgery includes a few small incisions, and, as a result, people tend to heal from it very well. The planning is significant because the target is about the size and shape of an almond sliver and is located deep inside the brain. The procedure involves mapping the brain anatomically, with imaging studies such as MRI and CT scans, as well as physiologically. The activity of the brain is recorded and analyzed to ensure and refine the final proper placement of the stimulating electrode. The electrode is also tested intra-operatively to gauge both the effect of stimulation and to ensure that there are no adverse side effects. Because so little surgery is involved, most people go home the next day.
Who is a good candidate for stimulation? For essential tremor, any patient whose tremor prevents him from doing normal daily activities—eating, dressing, or walking—might consider deep brain stimulation. For Parkinson’s disease, good candidates are typically patients who have symptoms that are worsening and are requiring increased administration of medication in terms of dose, frequency or number of medications. It is important, however, that patients are continuing to respond to their medications.
The goals of stimulation surgery are to give patients the level of function they experience when they are at their best on medications and to make this level of function what they experience the majority of time. Stimulation also is FDA approved for dystonia and obsessive compulsive disorder. Though these diseases are rarer, the results are usually impressive. In the near future, stimulation is likely to be approved for depression and epilepsy. Research is ongoing for the use of stimulation in a variety of other disorders, including Tourette’s syndrome, brain injury, obesity, addiction and eating disorders.
Ultimately deep brain stimulator implantation is an elective procedure. It is done for patients who are functional in an attempt to make them more functional. As a result, the answers to “Who is right for deep brain stimulation?” and “When is the right time to do it?” are largely personal ones. Our guidance is typically that the risk of doing something ought to be less than the risk of doing nothing. While we are able to extensively discuss the risk of the procedure, we are unable to know what the risks of doing nothing are. Only the patient knows what these risks may be.
Penn State Milton S. Hershey Medical Center has become a leader in the implantation of deep brain stimulators. If you would like more information about deep brain stimulation or would like to set up a consultation, call 717-531-4191.
Dr. James McInerney is director of the Penn State Hershey Stereotactic and Functional Neurosurgery and associate professor in the Department of Neurosurgery at the Penn State Milton S. Hershey Medical Center.