Movement Disorders Surgery Program

Inability to achieve normal control of body movement is among the most distressing of neurological illnesses. Parkinson's disease and related syndromes, which are examples of such disorders, affect 1 percent of the U.S. population over age 50, but may also affect younger people. While this is the most common movement disorder, familial tremor, dystonia, and other syndromes affect many other people.

Recent decades have seen improvement in our ability to treat some of these problems with medication. Some, however, are either resistant to medication from the outset or become so with time. Medications may also produce side effects which are unacceptable. When medical therapy proves unsatisfactory, surgical procedures may be considered for relief of movement problems.

Movement disorders are classified into two major categories: those associated with decreased ability to move and those associated with increased or involuntary movements. Some syndromes, such as Parkinson's, fit into both categories. Surgical procedures exist to treat both but are much more likely to be effective in some circumstances than in others. People affected by movement disorder syndromes should therefore discuss with their physician or neurologist whether surgical treatment is appropriate. Northwestern Memorial Hospital offers a comprehensive program for the treatment of movement disorders, including both medical and surgical options.

The two most frequently used surgical procedures for treating movement disorders are called pallidotomy and thalamotomy. The difference between these two procedures is described below, but the method of surgery is similar.

Many different pathways within the brain and nervous system are simultaneously involved in the control of movement. Some of these pathways are feedback circuits which are designed to fine tune movements, and others are related to the ability to switch on a series of movements. When these auxiliary circuits malfunction, they may interfere with normal, voluntary movement activities. This is believed to be the explanation for many movement disorders. Surgery improves control of voluntary movement by interrupting the malfunctioning circuit. Usually this involves the use of radiofrequency electromagnetic energy to cauterize a tiny volume of brain tissue which is involved in the circuit. More recently, devices have become available which use electrical stimulation to interrupt the abnormal activity in the circuit.

The place in which this circuit is interrupted must be determined precisely so that the process is both safe and effective. Because the brain is as different from person to person as are facial features, finding the exact target which will safely interrupt the malfunctioning circuit can be difficult. We believe, as do many other centers, that a technique called microelectrode recording is essential for this purpose. This technique was used for the first time in 1958 at Northwestern University, and it has been continually improved and refined with advances in technology.

The surgery starts with application to the head of a special device called a stereotactic frame. This is done with local anesthesia. A CT or MRI scan of the head is then obtained with the frame in place. Afterward, the surgeon is able to select the approximate area of the target by looking at the scan pictures and can measure the precise distance between the markers on the frame and the target. Once this information is obtained, the patient is brought to the operating room. Some sedatives may be given, but the operation must be done with the patient awake, as his or her cooperation is crucial to the success of the surgery.  The surgery is not painful, but may last for several hours. The stereotactic frame is attached to a rigid base, and the patient is made as comfortable as possible. Then a small hole is drilled in the skull, again using local anesthesia. Tiny electrodes are then lowered into the brain to approach the target identified on the CT or MR scan. Monitoring of electrical signals in the brain, using these electrodes, allows the surgeon to find the precise location in which to perform the cauterization or stimulator implant. Usually several recordings need to be made with the electrode in slightly different positions. During this time the patient's hands, arms, and legs may be moved by one of the team physicians or the patient may be asked to move them. Gentle touches with cotton swabs, and flashlights shone at the eyes may also be used during the monitoring. Once the proper target is identified, performing the cauterization or stimulator probe placement takes only a few minutes. Then, sutures are used to close the small scalp incision, the stereotactic frame is removed, and the patient returns to his or her room for overnight monitoring. The effect of the surgery is usually apparent immediately and most people return home the next day.

This surgery is reserved for people whose movement disorders are not controlled by adequate trials of medical therapy, or who cannot tolerate the medication due to side effects. Generally, people over age 80 or with significant high blood pressure or other serious health problems are not considered for surgery, though individual exceptions may be made. Tremor responds best to thalamotomy or thalamic stimulation, and these procedures are used with good results in people with familial (essential) tremor and in people with Parkinson's disease whose predominant symptom is disabling tremor. Rigidity, slowness of movement, and dyskinesia (the abnormal movements which may result from long-term medical treatment of Parkinson's disease) appear to respond well to pallidotomy. The indications for pallidotomy are still being explored. Other types of movement disorders, such as dystonias, do not respond as well to surgery.

Several new surgical treatments for movement disorders are now being used or investigated. Placement of thalamic stimulating electrodes has recently received FDA approval and is now our most requested procedure for tremor control at Northwestern. The electrodes are attached to a "pacemaker" which is implanted under the skin. Adjustment of the stimulation parameters allows finer control of the effects of the surgery with lower risk, although permanent implantation of hardware is required. We recommend this procedure for people with tremor affecting one side of the body only, as a treatment for the second side in those who have had a successful thalamotomy on one side, and for younger people where the device can be adjusted to control new tremor should it recur. An even more ideal placement of stimulators in Parkinson's patients will be in the subthalamic nucleus (STN), where European studies have shown that all the major symptoms of Parkinson's disease can be relieved. FDA approval for this procedure is expected soon in the United States.

The Northwestern Memorial Hospital Movement Disorder Surgery program helped pioneer the use of computerized trajectory guidance for the insertion of stimulators and placement of lesions. This specialized technique improves the speed and accuracy of movement disorder surgery.

Other exciting therapies for Parkinson's Disease are expected in the near future. Some may involve the use of genetically engineered cells to replace or assist those which have been altered by the disease process. The next few years may be a turning point in our surgical treatment of this and similar illnesses.

No surgical procedure is risk-free. Movement disorder procedures are considered major surgery, and the potential risks include those of any major surgery, those of brain surgery, and those pertaining to movement disorder surgery in particular. The experience of many surgical centers over many years shows that the combined risk of mortality or major disability resulting from this type of surgery is under 1 percent (such disability is usually caused by a stroke). While these numbers mean that 99 percent of such operations do not result in these outcomes, the risk is not zero. Transient problems resulting from surgery are more common, and include temporary weakness, tingling sensations, speech difficulty, and behavioral changes. These probably occur in about 5–10 percent of patients undergoing thalamotomy. Tingling sensations may be more common after stimulator implants, but the difficulties with speech are fewer. Additional risk may be encountered if the procedure is done on both sides at once, and for this reason most surgeons prefer to wait several months between procedures if bilateral surgery is contemplated.

Most patients who undergo surgery for movement disorders are very pleased with the results, which are immediate and often dramatic. When offered to properly selected patients and performed under carefully controlled conditions, the surgery is both safe and effective. Future developments promise continuing improvements in this field. Northwestern remains committed to the complete and comprehensive care of movement disorder patients, and we welcome inquiries about our surgical and medical programs.

For further information or to schedule a consultation please call 312/695-8143 (at Northwestern Memorial Hospital) or 847/570-1446 (at Evanston Hospital). Send e-mail to jrosenow@nmff.org for more information.

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