Understanding Deep Brain Stimulation

For certain movement disorders, such as Parkinson's disease, deep brain stimulation (DBS) can be used to treat motor symptoms, tremor and involuntary muscle movements when medications begin to lose effectiveness. But what is DBS? How does it work? What conditions does it treat? Is it safe? We talked to Darolyn O'Donnell, MS, CTRS, the recreation therapy coordinator at the Barrow Neurological Institute's Muhammad Ali Parkinson Center, for further insight.

What Is Deep Brain Stimulation?

To understand how DBS works, you need to understand how Parkinson's disease and other movement disorders cause motor function symptoms such as tremor, slowness and stiffness. These symptoms are the result of faulty communication circuits among cells in certain areas of the brain. When these signals get scrambled, so do muscle movements.

In DBS, thin wires called electrodes are implanted in the brain, as the Parkinson's Disease Foundation (PDF) details. The original surgical approach for the DBS procedure was to keep patients "Awake" for deep brain stimulation. During the surgery, a local anesthetic is used to numb the areas of the scalp and skull affected by the operation. A metal frame is affixed to the patient's skull — this helps guide the surgeon's placement of the electrodes. Since the patients are lightly sedated during the procedure, they are awake to test the effects of the electrode's stimulation.

Barrow has been on the forefront in developing and validating a new approach to the DBS procedure. Patients now have the option to undergo DBS surgery "Asleep" under general anesthesia. This improves patient comfort, reduces the duration of the surgery and allows Parkinson's patients to maintain their regular medicine regime leading up to the procedure.

Asleep DBS uses Magnetic Resonance Imaging (MRI) to pick a target, followed by intraoperative computed tomography (CT) scan to verify the accurate placement of the electrodes to that target. The premise, is that asleep DBS can detect the target on MRI, but not on CT scans. Therefore awake surgery is usually recommended for patients who cannot undergo an MRI.

Once the electrodes are placed, they are then connected to a small device called an internal pulse generator (IPG) that is implanted under the skin, usually near the collarbone. The IPG sends a continuous electrical current to the area of the brain where the faulty communications are occurring. The electrical current disrupts the scrambled circuits, which helps calm dysfunctional movements in the body.

What Conditions Is DBS Used For?

Deep brain stimulation is not a widely used therapy. Approximately 125,000 people worldwide have DBS implants, according to PDF.

The American Association of Neurological Surgeons (AANS) says that although DBS is primarily used to treat symptoms of Parkinson's disease, the FDA has also approved its use for essential tremor and dystonia (a chronic muscle spasm neurological disorder).

Does DBS Work? Who Is a Candidate?

"DBS is a very effective treatment for people who are the right candidates," O'Donnell said. However, patients must meet certain criteria to be considered for the surgery. " Most DBS centers have specific criteria which include a confirmed diagnosis of Parkinson's for at least four years and require extensive testing including MRIs (satisfactory brain imaging), neuropsychological testing to make sure cognition is intact, 'on and off' testing ... and a complete medical evaluation to make sure people are healthy enough for surgery," she said. Good candidates also include patients who have had motor complications of medical therapy, like motor fluctuations, involuntary movements (dyskinesias) or refractory tremor.

O'Donnell explains that "on and off" testing refers to observing the effects of the medications on each patient: how your symptoms improve when you're "on" the medication and how taking you "off" the medication affect your muscle movements. This involves having the patient to abstain from their Parkinson's medications for 12 hours so your doctor can observe this state. Then the patient resumes medication usage and for the doctor to observes the difference. To qualify for DBS, you usually must exhibit a positive response to your Parkinson's medications. In order to qualify for DBS with other diagnoses, you must demonstrate that your quality of life is adversely impacted by the disease and you get little if any benefit from medications.

According to AANS, deep brain stimulation is generally safe, with minimal side effects. Because of its safety record -- and the fact that therapy can be adjusted to treat motor symptoms and involuntary muscle movements as the condition changes -- DBS continues to win acceptance as a viable treatment option for Parkinson's disease.

If you believe you might be a candidate for DBS, talk to your neurologist about options that might be right for you.