(Parkinson's, Tremors)
PROGRAM DESCRIPTION
Washington University neurosurgeons offer the only surgical program for movement disorders in Missouri. Our surgeons provide a full range of services, including subthalamic deep brain stimulation for Parkinson’s disease and thalamic deep brain stimulation for essential tremor. In both cases, surgeons use stereotactic techniques — combining a three-dimensional framing system with imaging modalities — to precisely locate targets deep within the brain. In some cases, microelectrode recording helps verify the target. A less invasive option is Gamma Knife radiosurgery, in which radiation beams precisely target the desired area of the brain to create a lesion without incisions.
For many patients with Parkinson’s disease or essential tremor, medications are often inadequate to control disabling symptoms. Some of these patients may benefit from stereotactic neurosurgical procedures to improve their function. The most common neurosurgical procedures performed for movement disorders by neurosurgeons at Washington University School of Medicine and Barnes-Jewish Hospital in St. Louis are pallidotomy, thalamotomy, thalamic deep brain stimulation and subthalamic deep brain stimulation.
CONDITIONS & TREATMENTS
Parkinson’s disease
Parkinson’s disease is a chronic, progressive and often disabling disease of the nervous system characterized by rigidity (stiffness), bradykinesia (slowness of movement) and tremor (shaking). Medications are used to treat the symptoms; the most commonly prescribed drug is a levodopa/carbidopa combination (Sinemet). One unfortunate side effect of levodopa is the development of dyskinesias — abnormal, involuntary movements. Dyskinesias can become a significantly disabling feature of Parkinson’s disease. As Parkinson’s disease progresses, the symptoms become less responsive to medical therapy. Patients often suffer from the on-off phenomenon, in which their mobility abruptly changes from good (on) to severely impaired (off). For these patients who continue to be severely disabled in spite of optimal medical therapy, surgical intervention should be considered. Pallidotomy and subthalamic deep brain stimulation are usually the best surgical options for Parkinson’s disease. For patients in whom tremor is the predominant and most disabling symptom, thalamotomy and thalamic deep brain stimulation are also options.
Essential tremor
Essential tremor is a neurological disorder characterized by rhythmic shaking of part or all of the body. This disorder often is inherited, in which case it is termed familial tremor. Unlike the tremor of Parkinson’s disease, essential tremor is not accompanied by rigidity or bradykinesia. The tremor most commonly affects the hands and arms but may also affect the voice, head, trunk or legs. The tremor is predominantly an action tremor, meaning it becomes most prominent during the active movement of the limb, such as while eating or drinking from a cup. Essential tremor often responds well to medications, such as propanolol. Many patients will also notice improvement in their symptoms after consumption of an alcoholic beverage. For patients whose tremor no longer responds adequately to medication, surgical treatment can provide a dramatic restoration of function. Both thalamotomy and thalamic deep brain stimulation can provide excellent relief from disabling tremor.
Stereotactic neurosurgical procedures
Because the specific structures involved in the neurosurgical treatment of movement disorders are deep within the brain, stereotactic techniques are required to locate these targets. The term stereotactic refers to the use of a three-dimensional coordinate system combined with an imaging technique, such as computed tomography (CT) scanning or magnetic resonance imaging (MRI), to precisely locate targets deep within the brain. These techniques are also commonly used in other neurosurgical procedures, such as the biopsy of deep brain tumors. All of the procedures described below are performed using stereotactic techniques. The patient is awake during most or all of the procedure in order to monitor the response of the symptoms to the intervention, as well as to ensure that no undesired side effects are being produced. In spite of being awake, patients generally tolerate the procedure well. A stereotactic head frame is employed to provide reference points for targeting. At the beginning of the procedure, the frame is attached to the patient’s head using local anesthetic to numb the scalp. An indicator box is then attached to the head frame, and an MRI or CT scan is obtained. Because of the indicator box, reference points, called fiducials, will surround the images of the brain and are used for precise targeting. After the calculations of the target coordinates have been completed, the patient is returned to the operating room for the remainder of the procedure. In the operating room the patient is made as comfortable as possible on the operating bed. An incision is planned and anesthetized with local anesthetic. After the incision is made, the targeting arc is attached to the head frame. The combination of the targeting arc and head frame allows the precise localization of targets deep within the brain. A small hole is drilled through the skull, and a probe is directed towards the target. For pallidotomy and subthalamic deep brain stimulation, microelectrode recording is performed to help verify the target. Microelectrode recording involves the insertion of a very thin electrode to monitor the electrical activity of neurons (nerve cells). The pattern of electrical activity is different within different structures of the brain, and therefore can provide confirmation that the electrode is within the desired structure. For tremor surgeries like thalamotomy and thalamic deep brain stimulation, the effect of electrical stimulation on the patient’s tremor is usually dramatic and provides adequate confirmation of the target. Once the target has been confirmed, a small area of tissue may be destroyed, as in the case of thalamotomy and pallidotomy, or an electrode may be inserted, as with thalamic or subthalamic deep brain stimulation.
Tremor Surgeries
Thalamotomy involves the creation of a lesion within an area of the brain’s thalamus called the nucleus ventralis intermedius (Vim). Although the precise physiology of tremor is not yet fully understood, this nucleus appears to serve as a relay between brain pathways responsible for smooth, coordinated movements. Microelectrode recording of neurons within this nucleus in patients with tremor demonstrates electrical activity that is synchronized with the tremor itself. Thalamotomy destroys these neurons and eliminates tremor. A thalamotomy on one side of the brain will only control the tremor on the opposite side of the body. In patients with essential tremor or Parkinson’s disease, thalamotomy is approximately 90 percent effective in controlling tremor initially, with about 80 percent of patients experiencing effective control over the long term. For other types of tremor, such as intention tremor as a result of brain injury, stroke or multiple sclerosis, the overall rate of effectiveness is much lower, although some of these patients may still benefit from the procedure. Potential complications of thalamotomy include weakness, clumsiness, difficulty swallowing and slurred speech. With unilateral (single-sided) thalamotomy, the risks are low, making thalamotomy an attractive option for treating tremor on one side. Since many patients will be satisfied with the restoration of function to their dominant hand, single-sided treatment is often adequate. Patients with severe bilateral or midline (head, trunk or voice) tremor will usually want treatment on both sides. When thalamotomy is performed on the second side, the risk of complications, especially speech or swallowing problems, is somewhat higher. Also, because thalamotomy involves destruction of brain tissue, any undesired side effects of surgery may be permanent.
Thalamic deep brain stimulation provides a nondestructive alternative to thalamotomy. In this procedure, instead of creating a lesion, a stimulating electrode is implanted within the nucleus ventralis intermedius (Vim) of the thalamus. This electrode is connected to a pacemaker-like device called an implantable pulse generator, which is capable of delivering an electrical current to the electrode. The electrical current shuts down the surrounding brain tissue, producing the same beneficial effect on tremor as a thalamotomy. Potential side effects are similar to those seen with thalamotomy; however, the pulse generator can be programmed with different electrode combinations and stimulation parameters to maximize the suppression of tremor and minimize these side effects. More importantly, the effect is reversible, occurring only when the pulse generator is on. For this reason, thalamic stimulation is safer for treatment of both sides than bilateral thalamotomy.
Surgeries for Parkinson’s disease
Pallidotomy refers to the creation of a lesion within a structure of the brain called the globus pallidus interna (Gpi). In Parkinson’s disease, Gpi is hyperactive and produces signals within the brain that inhibit movement, thereby causing rigidity and bradykinesia (slowness of movement). By destroying part of the Gpi, a pallidotomy reduces the signals inhibiting movement and can relieve some of the symptoms of Parkinson’s disease. Rigidity and bradykinesia usually improve significantly following pallidotomy. Tremor improves somewhat; however, if tremor is the dominant symptom, thalamotomy or thalamic deep brain stimulation may be more effective. Pallidotomy is especially effective in reducing drug-induced dyskinesias. As a result, many patients will actually increase their dose of Sinemet postoperatively since they are able to tolerate the higher dosing without dyskinesias. The risks of pallidotomy, like those of thalamotomy, are low when only one side is treated but are higher with bilateral treatment.
Subthalamic nucleus stimulation (bilateral) is a nondestructive technique for treating Parkinson’s disease. In this procedure, electrodes are implanted into the subthalamic nucleus for chronic stimulation. The stimulation suppresses the hyperactive signals from this nucleus that contribute to the symptoms of Parkinson’s disease. Bilateral subthalamic nucleus stimulation is effective in reducing rigidity, bradykinesia, tremor, on-off fluctuations and freezing. Patients are usually able to reduce their medication, which often eliminates problems with drug-induced dyskinesias. As with thalamic deep brain stimulation, adjustments can usually be made to minimize side effects.
Gamma Knife radiosurgery for movement disorders
Although the lesions of pallidotomy and thalamotomy are usually created using an electrode inserted into the brain using standard stereotactic technique, these lesions can also be created with the technique of Gamma Knife radiosurgery. This technique also involves the placement of a head frame with subsequent MRI or CT imaging to identify the target. Instead of inserting an electrode for lesion placement, the Gamma Knife directs focused radiation to the target. This creates an effective lesion for either thalamotomy or pallidotomy. The advantage of this technique is that it is relatively noninvasive and can therefore be performed on patients whose medical condition might preclude a more invasive procedure. The disadvantage of placing lesions with Gamma Knife is the inability to perform intraoperative stimulation or microelectrode recording to verify the target. Also, there is a significant delay, ranging from months to years, in the onset of benefit. Nevertheless, in selected patients, Gamma Knife radiosurgery is an important tool in the surgical treatment of movement disorders.
FACULTY
Neurosurgery Providers
Joshua M. Dowling, MD
Keith M. Rich, MD
Neurology Providers
James E. Galvin, MD
Joel S. Perlmutter, MD
Brad A. Racette, MD
Samer D. Tabbal, MD
MAKE AN APPOINTMENT
Movement disorder patients should be referred to the Movement Disorders Center in the Department of Neurology for initial evaluation. Please call (314) 362-6908.
PATIENT OFFICE LOCATIONS
Adult Patients
Neuroscience Center
Center for Advanced Medicine
4921 Parkview Place, Suite 6C
St. Louis, Missouri 63110
Helpful Maps
SPECIALTY LINKS
National Parkinson Foundation
American Parkinson Disease Association