Pacemaker for the Brain
A Better Life with Deep Brain Stimulation
Monday January 14, 2008
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Deep brain stimulation involves surgically implanted electrodes in specific areas of the brain where abnormal movements originate.
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DBS: Potential for Depression and OCD
Just as with DBS treatment for Parkinson’s and essential tremor, which already is FDA approved, the success of DBS for mental depression and OCD is directly related to finding the specific area in the brain for stimulation and can be adjusted as a patient’s condition changes over time.
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Control over their bodies translates into functional, active, and independent lives. But too often traditional medication regimens do not adequately address the disabling and embarrassing symptoms, leaving many as shut-ins, isolated from activities, family, and friends.
“People can make themselves prisoners and cut themselves off socially,” says Sharon K. Powell, RN, MPH, nurse educator and deep brain stimulation (DBS) coordinator at the Maryland Parkinson’s Disease and Movement Disorders Center, department of neurology, University of Maryland Medical Center in Baltimore.
Now, thanks to the advanced technology of DBS, many people can experience a dramatic increase in body control and get out of the house to enjoy life.
DBS involves surgically implanting electrodes in specific areas of the brain where abnormal movements originate. The electrode device is similar to a cardiac pacemaker and is programmed individually to provide the right electrical stimulation needed to interfere with, and suppress, abnormal electrical impulses that are causing symptoms such as seizures and tremors.
DBS is approved by the Food and Drug Administration as a treatment for essential tremor, Parkinson’s disease, and dystonia and also is used in the treatment of tremor, because of muscular sclerosis, and for chronic pain. DBS is being investigated for use in seizure disorders, depression, and obsessive-
compulsive disorder.
“DBS is a very exciting surgical intervention that can really make a difference in quality of life,” says Powell.
Steps to better body control
Treatment with DBS is done in several stages. First, MRI and CT imaging is used to pinpoint the specific areas of the brain that need to be treated. A high-tech guidance system translates images into 3D pictures that help surgeons map out the safest, least-invasive path to the tiny targets, which are only millimeters in size.
During the surgery, the guided imaging system is combined with an audio component and a recording device that allows surgeons to listen to the distinctive sounds of brainwaves in different areas of the brain and locate the precise area to place the electrode. For patients with bilateral symptoms, twin electrodes are placed in the specific structure in both sides of the brain.
For Parkinson’s disease, electrodes are placed in the subthalamic nucleus, where stimulation can improve tremor; rigidity; akinesia (lack of movement or loss of spontaneous movement); bradykinesia (slowness of movement); and problems with walking, handwriting, and posture.
For tremors, electrodes are placed in the thalamus. Thalamic stimulation can treat tremors of any cause, including essential tremor, multiple sclerosis, dystonic tremors, and Parkinson’s disease.
The DBS procedure is performed through a burr hole in the skull and is tested on the spot to confirm placement. Incredibly, it is not unusual for tremors to stop instantaneously upon stimulation in the OR, according to Patricia Taverna, RN, MA, ANP, a nurse practitioner at the Center for Movement Disorders at New York University.
“For the patients with essential tremor, you see the most dramatic effect in the OR,” she says, adding that patients who have muscle rigidity also may experience rapid relief.
Patients remain conscious and talking throughout the procedure so they can participate in the initial testing of the device. Because there are no pain receptors in the brain, patients only need a local anesthetic to numb the skin and do not feel the drilling of the burr hole and the placement of the electrode.
“They do not complain of pain during the procedure,” says Taverna.
An added benefit to remaining conscious during the procedure is patients often experience the success of the surgery instantly. Patients also are able to tell the surgical team if they see any flashes of light or feel unusual sensations, such as tingling, which could indicate an electrode may be getting too close to an area that could cause complications.
Patients must complete more steps before they again can experience the initial excitement of testing done in the OR. They also must undergo a follow-up procedure about a week later to implant the pacemaker-type device, the neurostimulator. It is placed below the collarbone and connected to the electrode in the brain by running wires under the skin. The neurostimulator contains a battery and electronics that produce the electrical charge in the brain.
Patients need to wait two to three weeks before they can have the neurostimulator programmed. This period ensures they are fully recovered from the procedures and the brain swelling that occurs during surgery is resolved. The care team then turns on and adjusts the charges from the stimulator, depending on the patient’s needs.
“DBS is programmable, and we can keep adjusting the voltage and the frequency as necessary to continue to control symptoms throughout a lifetime,” says Powell.
Realistic expectations
Patient education before the procedure is vital to ensure patients have realistic expectations of the procedure.
“The take-home message for candidates for the procedures is that … DBS doesn’t cure or stop the progression of the disease or make you like you were 20 years ago,” says Powell. “People with realistic expectations are much more pleased after the surgery.”
It is possible a small number of patients will have no improvement in their symptoms.
However, nine out of 10 Parkinson’s patients experience a significant improvement in functional ability with DBS. It also eliminates tremor in more than 80% of patients, according to Patrick J. Kelly, MD, professor and chairman of the department of neurosurgery at New York University School of Medicine.
Candidates also should understand they still will need medications after the surgery. They can, however, often reduce their dosages so much that side effects such as dyskinesias improve substantially.
“Most patients still need their meds, but they are reduced by about 50%,” says Taverna.
Patients also need to know DBS, like all forms of brain surgery, has a small risk of infection or bleeding. Rarely, significant bleeding into the brain can occur with stroke-like signs such as weakness on one side of the body. Some patients also experience short-term confusion.
In addition, not everyone is a good candidate for the surgery.
Patients who are not satisfied with their increasing loss of control because of movement disorders, who experience symptoms that cause a decline in the quality of life, and who have tried a reasonable trial of medication without adequate control of symptoms are considered good candidates.
The good news
Despite the risks and limitations, DBS is a significant upgrade over older surgeries, such as thalamotomy and pallidotomy, which treat Parkinson’s by destroying small parts of the brain within the thalamus or globus pallidus. Since the advent of DBS, it is no longer necessary to damage even small parts of the brain.
“The beauty of the surgery is that there is no destruction of brain tissue,” says Taverna.
The treatment also is completely reversible, according to Powell.
“If stem-cell therapy becomes the new answer for Parkinson’s disease, DBS can be stopped and removed,” she says.
Prospects for uncontrolled epilepsy
Research into other uses for DBS currently is underway. It is hoped the same DBS technology used to treat Parkinson’s and essential tremor will be effective and become FDA approved for the treatment of medically refractory epilepsy, which does not respond to antiepileptic drugs. About 1 million people have this debilitating form of seizures, according to the Epilepsy Foundation.
“These are people who have failed conservative treatment with medication,” says Carol Blyzniuk, RN, BSN, clinical nurse coordinator in the department of neurosurgery at Thomas Jefferson University Hospital in Philadelphia. She notes some people with medically refractory epilepsy do not even get relief with more aggressive treatment, such as the implantation of a vagus nerve stimulation device that prevents seizures by sending pulses of electrical energy to the brain via the vagus nerve.
Thomas Jefferson University Hospital is one of 17 medical centers in the nation participating in a trial to test Medtronic DBS technology for medically refractory epilepsy. The randomized double-blind study, the Stimulation of the Anterior Nucleus of the Thalamus in Epilepsy (SANTE) Trial, is investigating whether bilateral stimulation of the anterior nucleus of the thalamus — the brain’s central message and relay station — can safely and effectively reduce seizure frequency.
Trial participants are adults with partial-onset epilepsy, seizures that originate in a localized area of the brain, for whom at least three antiepileptic drugs have proven ineffective, and who have an average of six or more seizures per month.
Participants also include those who can’t have other procedures for recurring seizures, such a patient who has a tumor in the brain’s speech center.
“You can’t remove a tumor there because you would knock out the patient’s speech,” says Blyzniuk.
The DBS device has been implanted in 110 patients, who will be monitored for 13 months following implant, with long-term follow-up continuing until the device is approved for treating epilepsy or the study is stopped.
Results of the study are expected to be available this year.
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