Diann Shaddox Foundation for Essential Tremor
Deep Brain Stimulation for Movement Disorders
The time to consider Deep Brain Stimulation
(DBS) surgery is when quality of life is no longer acceptable on optimal medical therapy as administered by a movement disorders neurologist. The major risks are a 2% risk of stroke, due to bleeding in the brain, and a 5% chance of infection. DBS is a relatively complex therapy that requires regular neurological follow-up and battery changes every 3-4 years.
DBS surgery offers important symptomatic relief in patients with moderate disability from Parkinson's disease who still retain some benefit from antiparkinsonian medications and who are cognitively intact. Patients who fluctuate between "ON” and “OFF” medication states are usually good surgical candidates, as are those who have troublesome dyskinesias.
DBS surgery does not cure dystonia but can decrease the abnormal movements and postures of dystonia. The degree of benefit appears to vary with both the type of dystonia and the duration of the symptoms. Adolescents and young adults with inherited forms of primary dystonia appear to get very significant benefit. For patients with secondary dystonia due to stroke or head trauma, the benefit may be mild. Adults who have had dystonia for many years probably have less improvement than those with more recent onset of symptoms.
Also known as oral-facial dystonia, this syndrome is a combination of two forms of dystonia: blepharospasm and oromandibular dystonia.
DBS is a highly effective therapy for patients with essential tremor, often resulting in an 80% decrease in tremor that lasts for several years. Patients with a tremor secondary to stroke, traumatic brain injury or multiple sclerosis are less likely to benefit from DBS.
Who should get Deep Brain Stimulation (DBS)?This is a common question with a surprisingly simple answer: Anyone who would get significant benefit from the treatment and can undergo the operation with minimal risk. It is not necessary to suffer for years after diagnosis with a movement disorder, trying every known combination of medicine, before DBS can be considered. DBS is a surgical option that is known to improve quality of life for movement disorder patients, so when one’s quality of life is dramatically affected by the disease or by medication side effects, it’s time to consider DBS.
What is DBS?DBS surgery involves placing a thin metal electrode (about the diameter of a piece of spaghetti) into one of several possible brain targets and attaching it to a computerized pulse generator, which is implanted under the skin in the chest below the collarbone. All parts of the stimulator system are internal; there are no wires coming out through the skin. A programming computer held next to the skin over the pulse generator is used during routine office visits to adjust the settings for optimal symptom control. Unlike older lesioning procedures or gamma knife radiosurgery, DBS does not destroy brain tissue. Instead, it reversibly alters the abnormal function of the brain tissue in the region of the stimulating electrode. It is important to note that DBS therapy may demand considerable time and patience before its effects are optimized.
How does DBS work?DBS is not a cure for movement disorders, but it can successfully treat symptoms by disrupting the abnormal patterns of brain activity that become prominent in these diseases. DBS is often described as a brain “pacemaker” because constant pulses of electrical charge are delivered at settings that are thought to restore normal brain rhythms, allowing the restoration of more normal movements. The exact mechanisms of this neuromodulation are still unknown.
How is the surgery performed?
Awake Microelectrode-guided DBSDBS electrode placement in the awake patient using a stereotactic frame has been the gold-standard for the past fifteen years.
The basic surgical method is called frame-based stereotaxis, which is the traditional method for approaching deep brain targets though a small skull opening. A rigid frame is attached to the patient's head just before surgery, after the skin is anesthetized with local anesthetic. A brain imaging study is obtained with the frame in place. The images of the brain and frame are used to calculate the position of the desired brain target and guide instruments to that target with minimal trauma to the brain. In the operating room, an intravenous sedative is given, a Foley catheter is placed in the bladder, the stereotactic frame is rigidly fixed to the operating table, a patch of hair on top of the head is shaved, and the scalp is washed. After making the scalp completely numb, an incision is made on top of the head behind the hairline and a small opening, less than the size of a quarter, is made in the skull. If both sides of the brain are to be implanted, the skull opening is made on both sides before sedation is stopped and the patient is fully awoken.
For Parkinson and Dystonia patients, brain mapping using hair-thin microelectrodes is then used to record brain cell activity in the region of the intended target to confirm that it is correct, or to make very fine adjustments of 2 millimeters in the intended brain target to try and find the optimal location. The patient must be calm, cooperative, and silent during the mapping or else the procedure must be stopped. The brain's electrical signals are played over a speaker so that the surgical team can listen for distinctive patterns of neuronal activity that indicate the location of the recording electrode. Since each person's brain is different, the time it takes for the mapping varies from about 30 minutes to up to 2 hours for each side of the brain.
When the correct target site is confirmed with the microelectrode, the permanent DBS electrode is inserted and tested for about 20 minutes. The testing does not focus on relief of motor symptoms but rather on unwanted stimulation-induced side effects. This is because the beneficial effects of stimulation may take hours or days to develop, whereas any unwanted effects will be present immediately. For the testing, we deliberately turn the device up to a higher intensity than is normally used, in order to deliberately produce unwanted stimulation-induced side effects (such as tingling in the arm or leg, difficulty speaking, a pulling sensation in the tongue or face, or flashing lights). The sensations produced at high intensities of stimulation during this testing are experienced as strange but not painful.
Tremor patients, although typically awake in the operating room, do not require the brain mapping procedure described above, and proceed directly to implantation and testing of the stimulating electrode; however in this case it is important to see some benefit of stimulation on tremor symptoms, in addition to the absence of unwanted side effects, at appropriate stimulation parameters.
• Asleep Interventional-MRI-guided (iMRI) DBSOur department recently became one of the first ten programs in the world to offer a procedure that allows DBS electrodes to be implanted with the patient asleep in an MRI scanner instead of awake in the operating room. Parkinson’s and dystonia patients may now undergo surgery without having a frame placed on their heads and without having to be awake. This new procedure is potentially appropriate for:
How is asleep DBS different from awake DBS?Standard DBS is performed with the patient awake, secured in a head-frame, and off medication. Brain mapping through microelectrode recording is used to determine when the electrode is in the optimal location, along with turning on the stimulating electrode to test for efficacy and to evaluate for side effects. Local anesthetic is used to numb the skin where the incision is made, and mild sedatives are administered to ward off anxiety.
The prospect of being awake during brain surgery concerns some patients, as does the requirement to be off medication. Asleep DBS eliminates the need for awake brain mapping because real-time MRI scanning is used to locate the target, determine the correct implantation trajectory and confirm final electrode placement. Additionally, Parkinson’s patients continue to take their medications on the day of surgery.
For patients that are not candidates for awake or asleep-DBS, Gamma Knife surgery may be used to create a thalamotomy (lesion of the thalamus) for the management of tremor. The tremor can be from essential tremor, Parkinson’s disease or multiple sclerosis. Gamma knife radiosurgery is mainly performed in patients who have medical risks that make open surgery hazardous or those with very advanced age.
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