Currently, the most common surgical treatment for ET is deep brain stimulation (DBS). With DBS, electrical stimulation is delivered to the brain through an electrode implanted deep into the VIM nucleus of the thalamus. It is the most effective treatment for tremor, with the greatest effect on hand and arm tremor, but it may also be helpful in controlling head, voice, and leg tremor.
DBS can be done on either one (unilateral) or both sides (bilateral) of the brain; however, there is an increased risk of speech and balance problems with bilateral procedures. So, if tremor significantly affects both hands, the dominant hand is typically targeted and in some cases, bilateral procedures may be considered. The implanted electrode(s) in the brain is connected to a neurostimulator (battery) which provides the appropriate amount of electrical stimulation to control tremor. Although DBS can significantly reduce tremor, it is important to remember it is not a cure for ET.
There are three DBS systems receiving FDA approval or the CE Mark (in Europe) for the treatment of ET, both of which have been shown to significantly reduce tremor. In general, the systems are similar, but they each have specific features that make them unique. If you choose to receive DBS, you should discuss with your neurologist and neurosurgeon which device would be best for you. Learn more about the Medtronic, Abbott and Boston Scientific systems.
A specially trained neurosurgeon uses state-of-the-art equipment to take several images of the brain, in order to pinpoint the correct location for electrode placement. In one surgical approach, a stereotactic frame is attached to the individual’s head to hold it still during surgery. The frame is attached with four small screws. Local anesthesia is used to numb the area where the screws are placed. Alternatively, some surgical centers use a frameless (mini-frame) procedure which does not require the use of the head frame. Instead, small fixation screws are placed on the head and are used to assist in determining the exact area to target for surgery.
After the frame or frameless markers are attached, the patient undergoes a brain scan such as a CT or MRI which provides detailed pictures of the brain. The neurosurgeon uses these images to help determine the exact location of the VIM nucleus, the target location within the thalamus. Then a small area on the top of the head is cleaned and shaved. After local anesthesia, a small hole, called a burr hole, about the size of a nickel is made in the skull.
Most patients go through lead placement while fully awake. The brain itself does not contain nerve endings, so there is no pain. Actually, you don’t feel anything at all. And although it is not required you be awake for this surgery, it is helpful if you are so the surgical team is able to see the effects of the stimulation on your tremor, as well as any side effects that may occur. They will often have the individual do a task, such as draw a spiral or hold a cup against gravity, to measure the effectiveness of the placement. They know when they find the correct spot because the tremor will be suddenly and significantly reduced. This also allows them to observe any side effects of the stimulation so they can be resolved during surgery.
Once the neurosurgeon is satisfied with the placement of the electrode, the implantation is complete. Either on the same day or about a week later, the neurostimulator (battery) is placed, typically in the individual’s chest, and connected to the electrode by an extension wire, tunneled from the chest to the brain through the side of the neck. Neither the wires or the battery are visible. The complete procedure usually takes three to four hours to complete.
Although it can vary at different centers, a few weeks or a month after the surgery is completed, the physician or nurse programmer will turn the device on and program the settings to optimally control tremor. Most people don’t feel the stimulation, although some may feel a brief tingling when the stimulation is first turned on. Getting the initial settings right may take several programming sessions.
DBS is surgery and there is downtime immediately after the procedure. Patients will usually stay overnight after surgery and are asked to take it easy when they are released from the hospital the next day. But within a few weeks after the procedure, you can go back to your normal daily activities. Always follow your doctor’s instructions, but usually, you can gradually try activities that had become difficult for you because of your ET.
DBS involves physically going into the brain and implanting foreign objects, increasing the risk of infection and other complications. The most serious risks include infection, bleeding inside the brain, and seizures, but these occur in less than five percent of people. Some of these complications can be serious and, although rare, may be fatal.
Although it is fairly uncommon, once implanted, the system may become infected, parts may wear through the skin, or the device may malfunction. Any of these situations may require additional surgery or cause your ET symptoms to return. When implanted on both sides of the brain, DBS may also cause speech and language impairments. In addition, the system’s battery will need to be replaced every 3-7 years depending on the stimulation settings used. Battery replacement is an outpatient procedure. There are also rechargeable systems available.
Patients with DBS should avoid receiving diathermy, which is the use of electric currents to generate heat in tissue. It is often used during various surgeries, physical therapy for pain, and dentistry. The heat from the diathermy can be transferred to the brain through the DBS electrode resulting in brain damage and rarely death. In addition, if it is necessary to receive an MRI after the DBS system is implanted, it is important to contact the surgical center. MRIs can lead to heating of the DBS system which can cause damage to the brain. They can generally be performed without any problems as long as the proper safety measures are followed.
Finally, if the device is not effective or if a new treatment option becomes available, the device can be removed without any destruction of brain tissue.
Several reports have demonstrated DBS has a comparable improvement in tremor to thalamotomy, but with fewer complications. The majority of studies have reported improvements in tremor in 90% of patients. Long-term studies have shown the improvement in tremor is maintained in the majority of patients up to at least 7-10 years after the surgery; however, the magnitude of the benefit may reduce over time. Multiple studies have demonstrated the immediate and long-term benefits of DBS in controlling tremor with improvements in hand tremor of approximately 90%, and improvements in functional ability and performance of activities of daily living of approximately 85%. Although all of the large studies have targeted patients with disabling hand tremor, in these studies head and voice tremor have had some improvement. The greatest improvements in head and voice tremor were seen with bilateral procedures.
DBS is used to treat a number of neurological conditions, such as Parkinson’s disease, dystonia, and obsessive-compulsive disorder. It is also being studied as a treatment option for severe depression, epilepsy, Tourette’s syndrome, stroke, addiction, and dementia.