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Deep Brain Stimulation

Deep brain stimulation

Definition

Deep brain stimulation (DBS) delivers a constant low electrical stimulation to a small region of the brain, through implanted electrodes connected to an implanted battery. It is used to partially restore normal movements in Parkinson's disease, essential tremor, and dystonia.


Purpose

Parkinson's disease is due to degeneration of a group of cells called the substantia nigra. These cells interact with other brain regions to help control movement. The normal signals from the substantia nigra inhibit these other regions, and so when it degenerates, these regions become overactive. The electrical signals from the DBS electrodes mimic the inhibitory function of the substantia nigra, helping to restore more normal movements.

The substantia nigra normally releases the chemical dopamine, which exerts its inhibitory action on the globus pallidus interna (GPi) and the subthalamic nucleus (STN). For Parkinson's disease, deep brain stimulation is performed on these two centers. The target for DBS in dystonia is the GPi as well. Treatment of essential tremor usually targets the thalamus.

Each of these brain regions has two halves, which control movement on the opposite side of the body: right controls left, and left controls right. Unilateral DBS may be used if the symptoms are much more severe on one side. Bilateral DBS is used to treat symptoms on both sides.


Demographics

Parkinson's disease affects approximately one million Americans. The peak incidence is approximately age 62, but young-onset PD can occur as early as age 40. Because young-onset patients live with their disease for so many more years, they are more likely to become candidates for surgery than older-onset patients. In addition, younger patients tend to do better and have fewer adverse effects of surgery. Approximately 5% of older PD patients receive one form or another of PD surgery. Many more develop the symptoms for which surgery may be effective, but either develop them at an advanced age, making surgery inadvisable, or decide the risks of surgery are not worth the potential benefit, or do not choose surgery for some other reason.

Essential tremor is more common than Parkinson's disease, but rarely becomes severe enough to require surgery. Dystonia is a very rare condition, and the number of patients who have received DBS as of 2003 is under 100.


Description

Deep brain stimulation relies on implanting a long thin electrode deep into the brain, through a hole in the top of the skull. In order to precisely locate the target area and to ensure the probe is precisely placed in the target, a "stereotactic frame" is used. This device is a rigid frame attached to the patient's head, providing an immobile three-dimensional coordinate system, which can be used to precisely track the location of the GPi or STN and the movement of the electrode.

For unilateral DBS, a single "burr hole" is made in the top of the skull. Bilateral DBS requires two holes. A strong topical anesthetic is used to numb the skin while this hole is drilled. Since there are no pain receptors in the brain, there is no need for deeper anesthetic. In addition, the patient must remain awake in order to report any sensory changes during the surgery. The electrode is placed very close to several important brain structures. Sensory changes during electrode placement may indicate the electrode is too close to one or more of these regions.

Once the burr hole is made, the surgeon inserts the electrode. Small electric currents from the electrode are used to more precisely locate the target. This is harmless, but may cause twitching, light flashes, or other sensations. A contrast dye may also be injected into the spinal fluid, which allows the surgeon to visualize the brain's structure using one or more imaging techniques. The patient will be asked to make various movements to assist in determining the location of the electrode.

The electrode is connected by a wire to an implanted pulse generator. This wire is placed under the scalp and skin. A small incision is made in the area of the collarbone, and the pulse generator is placed there. This portion of the procedure is performed under general anesthesia.


Diagnosis/Preparation

DBS for Parkinson's disease is considered as an option in a patient who is still responsive to levodopa (used to treat symptoms) but has developed motor complications. These include the rapid loss of benefit from a single dose (wearing off), unpredictable fluctuations in benefit (on-off), and uncontrolled abnormal movements (dyskinesias). Essential tremor patients who are candidates for surgery are those whose tremor is unsatisfactorily controlled by medications and whose tremor significantly impairs activities of daily living. Similar criteria apply for dystonia patients.

The patient who is a candidate for DBS discusses all the surgical options with his neurologist before deciding on deep brain stimulation. A full understanding of the risks and potential benefits must be understood before consenting to the surgery.

The patient will undergo a variety of medical tests, and one or more types of neuroimaging procedures, including MRI, CT scanning, angiography (imaging the brain's blood vessels) and ventriculography (imaging the brain's ventricles). On the day of the surgery, the stereotactic frame is fixed to the patient's head. A local anesthetic is used at the four sites where the frame's pins contact the head; there may nonetheless be some initial discomfort. A final MRI is done with the frame in place, to set the coordinates of the targeted area of the brain in relation to the frame.

The patient will receive a mild sedative to ease the anxiety of the procedure. Once the electrodes are positioned, the patient receives general anesthetic to implant the pulse generator.


Aftercare

The procedure is lengthy, and the patient will require a short hospital stay afterward to recover from the surgery. Following the procedure itself, the patient meets several times with the neurologist to adjust the stimulation. The pulse generator is programmable, and can be fine-tuned to the patient's particular needs. This can provide a higher degree of symptom relief than lesioning surgeries, but requires repeated visits to the neurologist. Pulse generator batteries must be replaced every three to five years. This is done with a small incision as an outpatient procedure. Since the generator is in the chest area, no additional brain surgery is required.

The patient's medications are adjusted after surgery, with a reduction in levodopa likely in most patients who receive DBS of the subthalamic nucleus.


Risks

Deep brain stimulation entails several risks. There are acute surgical risks, including hemorrhage and infection, and the risks of general anesthesia. The electrodes can be placed too close to other brain regions, which can lead to visual defects, speech problems, and other complications. These may be partially avoided by adjusting the stimulation settings after the procedure. Because a device is left implanted under the skin, there is the risk of breakage or malfunction, which requires surgical removal.

A patient with implanted electrodes must not receive diathermy therapy. Diathermy is the passage of radiowaves through the tissue to heat it, and is used as a physical therapy for muscle pain and other applications. Diathermy poses a risk of death in a patient with DBS electrodes.

Patients who are cognitively impaired may become more so after surgery, and cognitive impairment usually prevents a patient from undergoing surgery.


Normal results

Deep brain stimulation improves the movement disorder symptoms of Parkinson's disease by 2575%, depending on the care of the placement and the ability to find the optimum settings. These improvements are seen most while off levodopa; DBS does little to improve the best response to levodopa treatment. Levodopa dose will likely be reduced, leading to a significant reduction in dyskinesias.


Morbidity and mortality rates

The rate of complications depends highly on the skill and experience of the surgical team performing the procedure. Rates from one of the most experienced teams, in a study of over 200 patients, were as follows.

Post-operative complications:

  • asymptomatic intracranial bleed (10% of procedures)
  • symptomatic intracranial bleed (2%)
  • seizures (3%)
  • headache (25%)
  • infection (6%)

Device-related complications:

  • lead replacements (9%)
  • lead repositionings (8%)
  • extension wire replacements (6%)
  • implantable pulse generator replacements (17%), approximately half of which were due to malfunction

The risk of death is less than 1%.


Alternatives

Patients who are candidates for deep brain stimulation have usually been judged to require surgery for effective treatment of their symptoms. Other surgical alternatives for Parkinson's disease include pallidotomy and thalamotomy, which destroy brain tissue to achieve the same effect as the stimulation. Pallidotomy is rarely performed for Parkinson's disease, unless tremor is the only debilitating symptom. It is common in essential tremor. DBS for dystonia is the only really promising neurosurgical treatment for this condition. Some peripheral surgeries may be appropriate for selected patients.

Resources

books

jahanshahi, m., and c. d. marsden. parkinson's disease: a self-help guide. new york: demos medical press, 2000.

organizations

national parkinson's disease foundation. bob hope parkinson research center, 1501 n.w. 9th avenue, bob hope road, miami, fl 33136-1494. (305) 547-6666. (800) 327-4545. fax: (305) 243-4403. <http://www.parkinson.org>.

we move, worldwide education and awareness for movement disorders. 204 west 84th street, new york, ny 10024. (800) 437-mov2, fax: (212) 875-8389. <http://www.wemove.org>.


Richard Robinson

WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?


Deep brain stimulation is performed by a neurosurgeon in a hospital.

QUESTIONS TO ASK THE DOCTOR


  • How many electrode implantations has the neurosurgeon performed?
  • What is his own rate of serious complications?
  • Would pallidotomy be appropriate for me?
  • How will my medications change after the operation?

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"Deep Brain Stimulation." Gale Encyclopedia of Surgery: A Guide for Patients and Caregivers. . Retrieved April 26, 2017 from Encyclopedia.com: http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/deep-brain-stimulation

Deep Brain Stimulation

Deep brain stimulation

Definition

In deep brain stimulation (DBS), electrodes are implanted within the brain to deliver a continuous low electric current to the target area. The current is passed to the electrodes through a wire running under the scalp and skin to a battery-powered pulse generator implanted in the chest wall.

Purpose

DBS is used to treat Parkinson's disease (PD) and essential tremor (ET). It has also been used to treat dystonia , chronic pain , and several other conditions

The movement disorders of PD and ET are due to loss of regulation in complex circuits within the brain that control movement. While the cause of the two diseases differ, in both cases, certain parts of the brain become overactive. Surgical treatment can include destruction of part of the overactive portion, thus rebalancing the regulation within the circuit. It was discovered that the same effect could be obtained by electrically stimulating the same areas, which is presumed to shut down the cells without killing them.

DBS may be appropriate for patients with PD or ET whose symptoms are not adequately controlled by medications. In PD, this may occur after five to ten years of successful treatment. Continued disease progression leads to decreased effectiveness of the main treatment for PD, levodopa. Increasing doses are needed to control symptoms, and over time, this leads to development of unwanted movements, or dyskinesias. Successful DBS allows a reduction in levodopa, diminishing dyskinesias.

For PD, deep brain stimulation is performed on either the globus pallidus internus (GPi) or the subthalamic nucleus (STN). Treatment of essential tremor usually targets the thalamus. Each of these brain regions has two halves, which control movement on the opposite side of the body: right controls left, and left controls right. Unilateral (onesided) DBS may be used if the symptoms are much more severe on one side. Bilateral DBS is used to treat symptoms on both sides.

Precautions

DBS is major brain surgery. Bleeding is a risk, and patients with bleeding disorders or who are taking blood thinning agents may require special management. DBS leaves metal electrodes implanted in the head, and patients are advised not to undergo diathermy (tissue heating) due to the risk of severe complications or death. Diathermy is used to treat chronic pain and other conditions. Special cautions are required for patients undergoing MRI after implantation.

Description

In DBS, a long thin electrode is planted deep within the brain, through a hole in the top of the skull. To make sure the electrode is planted in the proper location, a rigid "stereotactic frame" is attached to the patient's head before surgery. This device provides a three-dimensional coordinate system, used to locate the target tissue and to track the placing of the electrodes.

A single "burr hole" is made in the top of the skull for a unilateral procedure. Two holes are made for a bilateral procedure. This requires a topical anesthetic. General anesthesia is not used, for two reasons. First, the brain does not feel any pain. Second, the patient must be awake and responsive in order to respond to the neurosurgical team as they monitor the placement of the electrode. The target structures are close to several nerve tracts that carry information throughout the brain. Abnormalities in vision, speech, or other cognitive areas may indicate that the electrode is too close to one of these regions, and thus needs repositioning.

Other procedures may be used to ensure precise placement of the electrode, including electrical recording and injection of a contrast dye into the spinal fluid. The electrical recording can cause some minor odd sensations, but is harmless.

The electrode is connected by a wire to an implanted pulse generator. This wire is placed under the scalp and skin. A small incision is made in the area of the collarbone, and the pulse generator is placed there. This portion of the procedure is performed under general anesthesia.

Preparation

A variety of medical tests are needed before the day of surgery to properly locate the target (GPi, thalamus, or STN), and fit the frame. These may include CT scans, MRI, and injection of dyes into the spinal fluid or ventricles of the brain. The frame is attached to the head on the day of surgery, which may be somewhat painful, although the pain is lessened by local anesthetic. A mild sedative is given to ease anxiety.

Aftercare

Implantation of the electrodes, wire, and pulse generator is a lengthy procedure, and the patient will require a short hospital stay afterward to recovery from the surgery. Following this, the patient will meet several times with the neurologist to adjust the stimulator settings, in order to get maximum symptomatic improvement. The batteries in the pulse generator must be replaced every three to five years. This is done with a small incision as an outpatient procedure.

The patient's medications are adjusted after surgery. Most PD patients will need less levodopa after surgery, especially those who receive DBS of the STN.

Risks

Risks from DBS include the surgical risks or hemorrhage and infection, as well as the risks of general anesthesia. Patients who are cognitively impaired may become more so after surgery. Electrodes can be placed too close to other brain regions, which can lead to visual defects, speech problems, and other complications. If these occur, they may be partially reduced by adjusting the stimulation settings. DBS leaves significant hardware in place under the skin, which can malfunction or break, requiring removal or replacement.

Normal results

Deep brain stimulation improves the movement symptoms of PD by 2575%, depending on how carefully the electrodes are placed in the optimal target area, and how effectively the settings can be adjusted. These improvements are seen most while off levodopa; DBS does little to improve the best response to levodopa treatment. DBS does allow a reduction in levodopa dose, which usually reduces dyskinesias by 50% or more. This is especially true for DBS of the STN; DBS of the GPi may lead to a smaller reduction. Levodopa dose will likely be reduced, leading to a significant reduction in dyskinesias.

DBS in essential tremor may reduce tremor in the side opposite the electrode by up to 80%.

Resources

BOOKS

Jahanshahi, M., and C. D. Marsden. Parkinson's Disease: A Self-Help Guide. New York: Demos Medical Press, 2000.

WEBSITES

National Parkinson's Disease Foundation. (December 4, 2003). <www.npf.org>.

WE MOVE. (December 4, 2003). <www.wemove.org>.

ORGANIZATIONS

International Essential Tremor Foundation. P.O. Box 14005, Lenexa, Kansas 66285-4005. 913-341-3880 or 888-387-3667; Fax: 913-341-1296. staff@essentialtremor.org. <http://www.essentialtremor.org/>.

Richard Robinson

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Deep Brain Stimulation." Gale Encyclopedia of Neurological Disorders. . Encyclopedia.com. 26 Apr. 2017 <http://www.encyclopedia.com>.

"Deep Brain Stimulation." Gale Encyclopedia of Neurological Disorders. . Encyclopedia.com. (April 26, 2017). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/deep-brain-stimulation

"Deep Brain Stimulation." Gale Encyclopedia of Neurological Disorders. . Retrieved April 26, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/deep-brain-stimulation