Deep brain stimulation (DBS) is a neurosurgical procedure involving the implantation of a medical device called a neurostimulator(sometimes referred to as a 'brain pacemaker'), which sends electrical impulses, through implanted electrodes, to specific targets in the brain (brain nuclei) for the treatment of movement and neuropsychiatric disorders. DBS in select brain regions has provided therapeutic benefits for otherwise-treatment-resistant disorders such as Parkinson's disease, essential tremor, dystonia, chronic pain, major depression and obsessive–compulsive disorder (OCD). DBS directly changes brain activity in a controlled manner, its effects are reversible (unlike those of lesioning techniques).
DBS is also used in research studies to treat chronic pain, PTSD, and has been used to treat various affective disorders, including major depression. While DBS has proven to be effective for some patients, potential for serious complications and side effects exists.
Components and placement
A deep brain stimulator system has three parts that are implanted inside the body:
- Neurostimulator – a programmable battery-powered pacemaker device that creates electric pulses. It is placed under the skin of the chest below the collarbone or in the abdomen.
- Lead – a coated wire with a number of electrodes at the tip that deliver electric pulses to the brain tissue. It is placed inside the brain and connects to an extension wire through a small hole in the skull.
- Extension – an insulated wire that connects the lead to the neurostimulator. It is placed under the skin and runs from scalp, behind the ear, down the neck, and to the chest.
The patient uses a handheld controller to turn the DBS system on and off. The doctor programs the stimulator settings with a wireless device. The stimulation settings can be adjusted as a patient's condition changes over time. Unlike other surgeries, such as pallidotomy or thalamotomy, DBS does not damage the brain tissue. Thus, if better treatments develop in the future, the DBS procedure can be reversed.
DBS is very effective at reducing dyskinesias, the uncontrolled wiggling movements caused by high doses of levadopa medication. Typically, DBS will help make your symptoms less severe so that lower medication doses may be used.
In Parkinson’s, parts of the basal ganglia are either under- or over-stimulated. Normal movement is replaced by tremor, rigidity and stiffness. DBS of specific ganglia alters the abnormal electrical circuits and helps stabilize the feedback loops, thus reducing symptoms.
Electrodes can be placed in the following brain areas :
- Subthalamic nucleus (STN) – effective for tremor, slowness, rigidity, dystonia and dyskinesia. Most commonly used to treat Parkinson's disease.
- Thalamus (VIM) – effective for tremor. It is often used to treat essential tremor.
- Globus pallidus (GPi) – effective for tremor, slowness, rigidity, dystonia and dyskinesia. It is used to treat dystonia and Parkinson's disease.
All three components are surgically implanted inside the body. Lead implantation may take place under local anesthesia or with the patient under general anesthesia ("asleep DBS") such as for dystonia. A hole about 14 mm in diameter is drilled in the skull and the probe electrode is inserted stereotactically. During the awake procedure with local anesthesia, feedback from the patient is used to determine the optimal placement of the permanent electrode. During the asleep procedure, intraoperative MRI guidance is used for direct visualization of brain tissue and device. The installation of the IPG and extension leads occurs under general anesthesia. The right side of the brain is stimulated to address symptoms on the left side of the body and vice versa.
Who is a candidate?
You may be a candidate for DBS if you have:
- A movement disorder with debilitating symptoms (tremor, stiffness) and your medications have begun to lose effectiveness.
- troubling "off" periods when your medication wears off before the next dose can be taken.
- troubling "on" periods when you develop medication-induced dyskinesias (excessive wiggling of the torso, head, and/or limbs).
DBS may not be an option if you have severe untreated depression, advanced dementia, or if you have symptoms that are not typical for Parkinson's disease.
DBS can help treat many of the symptoms caused by the following movement disorders:
- Parkinson's disease: tremor, rigidity, and slowness of movement caused by the death of dopamine-producing nerve cells responsible for relaying messages that control body movement.
- Essential tremor: involuntary rhythmic tremors of the hands and arms, occurring both at rest and during purposeful movement. Also may affect the head in a "no-no" motion.
- Dystonia: involuntary movements and prolonged muscle contraction, resulting in twisting or writhing body motions, tremor, and abnormal posture. May involve the entire body, or only an isolated area. Spasms can often be suppressed by "sensory tricks," such as touching the face, eyebrows, or hands.
What are the risks?
Deep brain stimulation involves creating small holes in the skull to implant the electrodes, and surgery to implant the device that contains the batteries under the skin in the chest.
Complications of surgery may include:
• Bleeding in the brain
• Breathing problems
• Heart problems
Possible side effects after surgery
Side effects associated with deep brain stimulation may include:
• Hardware complications, such as an eroded lead wire
• Temporary pain and swelling at the implantation site
A few weeks after the surgery, the device will be turned on and the process of finding the best settings for you begins. Some settings may cause side effects, but these often improve with further adjustments of your device.
Possible side effects of stimulation
• Numbness or tingling sensations
• Muscle tightness of the face or arm
• Speech problems
• Balance problems
• Unwanted mood changes, such as mania and depression
What are the results?
Successful DBS is related to 1) appropriate patient selection, 2) appropriate selection of the brain area for stimulation, 3) precise positioning of the electrode during surgery, and 4) experienced programming and medication management.
For Parkinson's disease, DBS of the subthalamic nucleus improves the symptoms of slowness, tremor, and rigidity in about 70% of patients. Most people are able to reduce their medications and lessen their side effects, including dyskinesias. It has also been shown to be superior in long term management of symptoms than medications.
For essential tremor, DBS of the thalamus may significantly reduce hand tremor in 60 to 90% of patients and may improve head and voice tremor.
DBS of the globus pallidus (GPi) is most useful in treatment of dyskinesias (involuntary wiggly movements), dystonias, as well as other tremors. For dystonia, DBS of the GPi may be the only effective treatment for debilitating symptoms. Though recent studies show little difference between GPi-DBS and STN-DBS.
Patients report other benefits of DBS. For example, better sleep, more involvement in physical activity, and improved quality of life.
Recent research in animals suggest that DBS may "protect" or slow the death of dopamine nerve cells. While the scientific data is inconclusive, observation of DBS patients show potential slowing of the disease relative to their pre-DBS condition.