Deep Brain Stimulation
Frequently Asked Questions
What is Deep Brain Stimulation (DBS) and how does it work?
Deep brain stimulation (DBS) is a surgical procedure used to treat certain neurologic conditions. In this type of treatment, an electrode is implanted surgically into the deep brain structures that influence movement. The electrode is connected by wires under the skin to a pacemaker-like device in the chest area, called an implantable pulse generator (IPG, or battery pack). Electrical signals delivered from the IPG and conducted through the electrode tip to surrounding brain tissues help modulate movement in patients with neurologic conditions such as Parkinson’s disease, essential tremor and dystonia. In these conditions, the DBS electrode serves to “normalize” the misfiring brain circuits that produce abnormal movements. In order to do this, the IPG can be programmed very easily in a variety of ways using a handheld device held up to the skin. In this manner, individualized settings can be created for each patient’s unique symptoms.
DBS offers the advantage of adjustable settings over time. The DBS electrode itself may last a number of years without needing replacement. The IPG may need replacement via a simple outpatient procedure every three to five years (for the typical patient with Parkinson’s disease) or less, and depends on the amount of current delivered through the electrode. Thus, higher settings result in a shorter battery life.
What conditions may be treated with DBS?
The conditions most commonly treated with DBS are Parkinson’s disease and essential tremor. Genetic forms of dystonia and certain focal dystonias can also be treated with DBS. Other neurologic and neuropsychological conditions such as Tourette syndrome, obsessive-compulsive disorder, depression and migraines are currently being studied. Generally, patients with these conditions are considered for DBS when their disease is advanced and does not respond to usual medical treatments.
Who qualifies for DBS?
Not all patients are candidates for DBS. When and whether patients are considered for placement of DBS depends on the condition being treated.
In Parkinson’s disease, patients who have advanced symptoms complicated by dyskinesias (too much movement created by medications) and motor fluctuations (wearing on and wearing off of medications) are considered candidates. Occasionally, patients with Parkinson’s disease who have severe, medication-refractory tremor may also be referred for DBS surgery. The presence of certain features such as dementia, advanced age, or associated medical conditions may indicate the potential for worsening after surgery, and should be carefully screened for. Accordingly, all patients with Parkinson’s disease undergo pre-operative evaluations by a Neurologist and Neuropsychologist before determining if DBS is right for them.
It is important to remember that DBS in Parkinson’s disease does not result in a greater degree of symptom control than medications alone. Other than tremor, DBS will not treat symptoms that have not also improved with medications. Rather, DBS in Parkinson’s disease is a way to eliminate the complications of medical therapy, possibly with an accompanying reduction in medication dosages. Largely due to these effects, several studies have shown that DBS improves the quality of life of patients with Parkinson’s disease. To help with patient selection and to better guide expectations of outcome, all patients will undergo an evaluation both “on” and “off” their Parkinson’s disease medications by a Neurologist prior to being referred for DBS surgery, and the Neurologist may recommend further medication adjustment prior to referral.
In essential tremor, patients whose symptoms are severely disabling and have not responded well to usual medication trials or botulinum toxin injections may be referred for DBS. Surgeries may be performed on one or both sides of the brain.
Patients who have genetic and/or generalized forms of dystonia, as in the case of DYT-1 dystonia (also known as idiopathic torsion dystonia), do best amongst all patients with dystonia referred for DBS. Some patients with cervical dystonia whose symptoms have not responded well enough or have stopped responding to botulinum toxin injections may also experience improvement after DBS.
What risks are associated with DBS?
Several factors influence the risks associated with DBS, relating to the surgical procedure itself, the chosen target in the brain, or to programming. Surgical risks include bleeding, infection, headache, confusion, seizures and others. Target-related risks include whether unilateral (one-sided) or bilateral (both sides) stimulators are placed, and whether the electrode(s) placement is optimal. The Neurosurgeon typically takes measures before and during the surgery to ensure that the electrodes are situated in the most ideal location for each individual patient. Nevertheless, in a minority of cases, the electrode may migrate from its intended position, resulting in side effects when the stimulator is turned on. Stimulation related side effects can include tingling or shock-like sensations, visual changes, slurred speech, dizziness, involuntary movements, gait imbalance, psychiatric or behavioral changes and declines in some memory tasks. These potential side effects vary with the site in the brain being stimulated, some may be temporary, and some can be eliminated with re-programming of the electrode(s). The potential for any side effects should be discussed with your Neurologist prior to pursuing DBS.
How is a person evaluated for consideration of treatment with DBS?
Patients seeking consideration for DBS placement at Scott & White should first be evaluated by Joohi Jimenez-Shahed, M.D., a Neurologist and Movement Disorders Specialist based at Scott & White Healthcare - Round Rock. Appointments can be made by calling 512-509-0200. After an initial evaluation, appropriate patients will be scheduled for the remainder of the required pre-operative evaluations, which vary depending on the condition being treated.
The DBS Team meets after all pre-operative evaluations are complete to collectively recommend whether DBS is the best option for any given patient. Recommendations regarding the location of stimulation and whether unilateral (one-sided) or bilateral (both sides) procedures are also made. The Neurologist will contact each patient to let them know if they have been considered a suitable candidate for DBS. Patients meeting all criteria for DBS will then be referred to the Neurosurgeon to begin the arrangements for pre-operative medical clearance, laboratory testing, brain MRI scans and ultimately scheduling the surgery.
What happens during the DBS surgery itself?
At Scott & White, DBS surgery is performed using a frameless technique. In this type of approach, markers are attached to the patient’s skull before a MRI is performed. Specialized software is then used to compare the location of these markers to the intended target based on the MRI, and the location of insertion is identified. Other centers may use an actual frame (often called a “halo”) attached to the patient’s skull instead of individual markers. Frames can be uncomfortable for the patient because they limit movement, and patients who have undergone DBS surgery often identify this as the most uncomfortable part of the entire procedure. On the other hand, surgeries performed using frameless methods allow the patient to move freely when needed. Studies have shown the frameless technique to result in similar outcomes as frame-based procedures.
After the MRI, patients are taken to the operating room and are positioned for the surgery. Local anesthesia and sedatives are administered to keep the patient comfortable while the Neurosurgeon makes a small hole in the skull and opens up the lining of the brain. A guidewire is then slowly advanced according to the planned trajectory while recordings are made of the electrical signals within the brain. The recordings are an extra measure to help identify the correct brain structure. Once the guidewire tip reaches the target, the patient’s sedatives and recordings are stopped, and electrical impulses are sent through the wire. The patient is tested to determine if effects or side effects occur during stimulation. More than one attempt at positioning may be required, with the “best” location being the one with most symptomatic benefit and least side effects.
Once the optimal location is identified, the actual electrode is inserted through the guidewire and is anchored to the patient’s skull while the guidewire itself is removed. The Neurosurgeon can then proceed to the other side if bilateral (both sides) electrodes were planned. The patient recovers overnight in the hospital for observation and is often discharged home the next day.
In a separate procedure, the Neurosurgeon connects the electrode to the IPG. This procedure requires general anesthesia. The wiring is tunneled under the skin to a point on the chest wall, outside the ribcage and usually just under the collarbone. The IPG is secured in place here, and the entire system is connected, but not turned on. The first programming session typically occurs one to two weeks later in the Neurologist’s office.