# Deep Brain Stimulation for Movement Disorders

## What is deep brain stimulation for movement disorders?

Deep brain stimulation (DBS) is a surgical procedure used to treat disabling symptoms of neurological disorders, including dystonia, epilepsy, essential tremor, and Parkinson's disease. DBS uses a surgically implanted, battery-operated medical device called an implantable pulse generator (IPG)—similar to a heart pacemaker—to deliver electrical stimulation to specific areas in the brain that control movement, which blocks the abnormal nerve signals that cause symptoms.

The DBS system features three components:
              - The lead (also known as an electrode) is a thin, insulated wire that is inserted through a small opening made in the skull and implanted in the brain. The tip of the electrode is positioned within a specific brain area, depending on the disorder.
              - The extension is an insulated wire that is passed under the skin of the head, neck, and shoulder, connecting the lead to the implantable pulse generator.  
              - The implantable pulse generator (IPG), also known as the "battery pack," is usually implanted under the skin near the collarbone. In some cases, it may be implanted lower in the chest or under the skin over the abdomen.

Once the system is in place, and after a period of healing post-surgery, the device is programmed to see what works best for each person through several visits with a neurologist. The therapy works by delivering electrical pulses from the IPG along the extension wire and the lead and into the brain. These pulses change the brain's electrical activity pattern at the target site to reduce motor symptoms.

Before the procedure, a neurosurgeon uses noninvasive diagnostic imaging—either magnetic resonance imaging (MRI) or computed tomography (CT) scanning—to identify and locate the exact target in the brain for the surgery. Most surgeons use microelectrode recording—which involves insertion of a tiny wire that monitors the activity of nerve cells—to more specifically identify the precise brain area that will be stimulated. 

For treatment of Parkinson's disease, DBS targets parts of the brain that play a role in the control of movement, such as: 
              - Thalamus (relays and integrates sensory and motor information)
              - Subthalamic nucleus (helps direct movement preparation)
              - Globus pallidus (helps regulate intended movement)

DBS for dystonia specifically targets the globus pallidus interna (involved in the regulation of voluntary movement), whereas DBS for essential tremor targets the thalamus. Different areas of the brain may be targeted for individuals with epilepsy who do not respond well to other therapies.

**How DBS is used to treat movement disorders**

Parkinson's Disease—DBS is used to treat the most commonly debilitating motor symptoms of Parkinson's disease (PD) such as rigidity, slowed movement, stiffness, tremor, and problems walking. It is used only for individuals whose symptoms cannot be adequately controlled with medication. However, only people who improve to some degree after taking medication for Parkinson's benefit from DBS. A variety of conditions may mimic PD but do not respond to medication or DBS.

Most people with PD still need to take medicine after undergoing DBS, but many people experience considerable reduction of their motor symptoms and may be able to reduce their medications. The degree of reduction varies by individual but can lead to a significant improvement in side effects such as dyskinesia (involuntary movements caused by long-term use of levodopa). In some cases, the stimulation itself can suppress dyskinesia without a reduction in medication. DBS does not improve cognitive symptoms in PD and may worsen them. Therefore, it is not generally used if there are signs of dementia. DBS does not slow the progression of the neurodegeneration.

Dystonia—For individuals with dystonia, DBS may reduce the disorder's characteristic involuntary muscle contractions that cause such symptoms as abnormal posture, repetitive movements, or twisting. DBS has been shown to reduce both the severity of symptoms caused by dystonia and the level of disability they may cause.  

People with dystonia may respond better to DBS than medication; therefore, DBS may be an appropriate option for people who have found little or no improvement of symptoms after botulinum toxin injections (often the most effective treatment for some dystonia). DBS may be quicker to reduce symptoms of dystonia that migrate from place to place in the body than dystonia that remains fixed in a single body site, although both groups are likely to see improvement.

Essential Tremor—DBS targeting the thalamus can improve the involuntary movement of the arms, hands, and head that is associated with essential tremor. 

Epilepsy—Brain stimulation for focal epilepsy (seizures that originate in just one part of the brain) may reduce the number of seizures over time. It is not a single therapy but is used along with anti-epileptic drugs. DBS has been approved as add-on therapy for adults with focal epilepsy. Another form of treatment, called neurostimulation, uses an implanted monitor in the skull and tiny wires to give small pulses of stimulation to the brain when electrical activity in the brain looks like a seizure.

**Advantages of DBS**

DBS involves minimal permanent surgical changes to the brain. If DBS causes unwanted side effects or more promising treatments develop in the future, the IPG can be removed and the DBS procedure can be halted. Also, stimulation from the IPG is easily adjustable—without further surgery—if the person's condition changes. Some people describe the pulse generator adjustments as "programming."

**Risks associated with DBS**

Although minimally invasive, DBS is a surgical procedure and therefore carries some associated risk. There is a low chance that placement of the stimulator may cause bleeding or infection in the brain. Complications of DBS, such as bleeding and swelling of brain tissue, may result from mechanical stress from the device but are generally reversible. Other complications may include headache, seizures, and temporary pain following surgery. Also, the hardware may erode or break down with use, requiring surgery to replace parts of the device.

Side effects of the stimulation may include numbness or tingling sensations, behavioral changes, as well as balance or speech problems.

## What are the latest updates on deep brain stimulation for movement disorders? 

The mission of the National Institute of Neurological Disorders and Stroke (NINDS) is to seek fundamental knowledge of the brain and nervous system and to use that knowledge to reduce the burden of neurological disease. 

NINDS supports research on DBS to determine its safety, reliability, and effectiveness as a treatment for neurological disorders. NINDS-supported research on brain circuitry was critical to the development of DBS. Researchers are continuing to study DBS and to develop ways of improving it.

In one NINDS clinical study, researchers are monitoring the progress of participants over a two-year period who receive DBS for either Parkinson's disease, dystonia, or essential tremor. Participants will return periodically and will be examined and answer questions, their DBS placement will be evaluated with MRI, and their neurostimulator will be programmed. The monitoring will include tests of movements, thinking, and memory.    

Other NINDS researchers are collecting data on the physiology and effectiveness of DBS therapy and motor and cognitive function in people with either Parkinson's disease, dystonia, or essential tremor who do not respond to other treatment. Data will include the change in motor symptoms measured before and three months after treatment. Intra-operative electrode recordings will investigate the neurophysiological mechanisms of DBS and explore the neural circuits essential for motor and cognitive processing in the basal ganglia.           

NINDS-supported researchers are developing and testing improved implantable pulse generators and new devices, and conducting studies to better understand and optimize the therapeutic effect of neurostimulation on neural circuitry and brain regions affected in neurological disease. Several research directions combine other tools like complex imaging of the brain with DBS. 

The Brain Research through Advancing Innovative Neurotechnologies (BRAIN) Initiative supports research to unlock the mysteries of the brain and accelerate the development of research and technologies to treat neurological disorders such as Parkinson's disease, essential tremor, and dystonia. For example, in one project aimed at treating essential tremor, researchers are using DBS devices that are capable of recording and stimulating simultaneously, to continuously monitor brain activity and deliver stimulation only when necessary to control tremor. This work may provide proof-of-concept for a first of its kind DBS system to treat essential tremor. 

More information about DBS research for movement disorders can be found using NIH RePORTER, a searchable database of current and past research projects supported by NIH and other federal agencies. It includes links to publications and resources from these projects.

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## How can I or my loved one help improve care for people with movement disorders?

Consider participating in a clinical trial so clinicians and scientists can learn more about DBS and movement disorders. Clinical research uses human volunteers to help researchers learn more about a disorder and perhaps find better ways to safely detect, treat, or prevent disease. 

All types of volunteers are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races, and ethnicities to ensure that study results apply to as many people as possible, and that treatments will be safe and effective for everyone who will use them. 

For information about participating in clinical research visit NIH Clinical Research Trials and You. Learn about clinical trials using DBS for movement disorders at Clinicaltrials.gov.
> Where can I find more information about deep brain stimulation for movement disorders?
Information may be available from the following organizations and resources:

**Parkinson's disease**

American Parkinson Disease AssociationPhone: 718-981-8001; 800-223-2732

Davis Phinney FoundationPhone: 303-733-3340 or 866-358-0285

Michael J. Fox Foundation for Parkinson's ResearchPhone: 212-509-0995

Parkinson AlliancePhone: 609-688-0870 or 800-579-8440

Parkinson's FoundationPhone: 800-473-4636

Parkinson's Resource OrganizationPhone: 760-773-5628 or 877-775-4111

**Dystonia**

The Bachmann-Strauss Dystonia & Parkinson FoundationPhone: 212-509-0995

Dystonia Medical Research FoundationPhone: 312-755-0198 or 800-377-3978

**Essential Tremor**

International Essential Tremor FoundationPhone: 913-341-3880 or 888-387-3667

HopeNetPhone: 703-543-8131

Tremor Action NetworkPhone: 510-681-6565

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