Now, neurologists and neurosurgeons at the Medical School and at Northwestern Memorial Hospital have developed a comprehensive program that uses both medical and surgical options to treat movement disorders, including Parkinson's disease and essential tremor.
Tremor is a rhythmic, shaking movement of the limbs, head or voice produced by involuntary muscle contraction and relaxation. Essential, or familial, tremor and tremor associated with Parkinson"s disease affect more than 1.5 million Americans. Researchers believe the number may be even higher, because essential tremor is often misdiagnosed or ignored as simply a symptom of aging. It is a progressive disease that tends to run in families (hence, the designation "familial"). It can afflict persons of any age or gender and is the most common movement disorder. Many physicians identify abnormal activity of brain cells as the suspected mechanism of the tremor.
Essential tremor is frequently confused with parkinsonism, but patients with essential tremor have no symptoms other than tremor. They generally experience action tremor, which occurs when a limb is in use, or postural tremor, which occurs when a limb is outstretched. The tremor is usually absent at rest and often affects the head and voice.
For essential tremor, certain drugs, such as beta blockers and the anticonvulsant primidone used alone or in combination, have been found effective, but these treatments are associated with side effects. Beta blockers can cause impotence and dizziness, as well as blood pressure changes. Primidone can cause excessive sedation and confusion.
Parkinson's disease, also classified as a movement disorder, is a progressive and degenerative neurological disease with tremor. In Parkinson's disease, nerve cells in a tiny section of the brain called the substantia nigra stop producing dopamine, a neurotransmitter or chemical "messenger" that plays an important role in controlling normal muscle movement. As the dopamine-producing brain cells, or basal ganglia, slowly degenerate, the disease progressively worsens.
After Alzheimer's disease, Parkinson's disease is the second most common neurodegenerative disease, affecting one percent of those older than 50. There are about 400,000 patients with Parkinson's disease in the U.S. The first symptom of Parkinson's disease is involuntary trembling, often in a hand or limb. Patients eventually develop a stooped posture and a shuffling walk and have difficulty standing. As the disease progresses, the muscles become stiffer and the face loses all expression. Many patients cannot communicate well because the tremors interfere with their speech. In about 40 percent of cases of Parkinson's disease, mental abilities also are affected.
Parkinson's is often treated with the drug levadopa, which replaces the missing natural dopamine, but response to levadopa declines over time. As larger doses are required, undesirable side effects, such as nausea, confusion, hallucinations and sleep disturbances, may develop. Prolonged use of levadopa also can cause involuntary movements of the limbs. In severe cases, the patient is eventually disabled by a combination of the disease and side effects of treatment.
If physicians in the Northwestern program determine that surgery is the more appropriate therapy in a particular patient, they may choose to cauterize certain portions of the brain associated with movement to interrupt malfunctioning neurocircuitry. Thalamotomy is cauterization of an areain the thalamus, the brain's message relay center, and pallidotomy is cauterization of a portion of the globus pallidus in the brain. Thalamotomy is used for essential tremor and tremor associated with Parkinson's disease. Pallidotomy treats those who develop symptoms from drugs, such as the jerky movements from levadopa, as well as rigidity and slowness of movement.
With the aid of "brain mapping" using a stereotactic head frame and imaging technology, surgeons can localize the precise area in the patient's brain to be cauterized. During the four- to five-hour procedure, the patient remains awake and able to communicate with the surgeon about various stimuli applied to different areas in the patient's brain. This allows the surgeon to correlate precisely the areas of the brain to the limb and body motions they control.
With both movement disorders and epilepsy, the overriding criterion for surgery is that the disease cannot be treated satisfactorily with medication alone. It also should be noted that surgery may treat these symptoms, but it is not a cure. In addition, both thalamotomy and pallidotomy are irreversible.
For those whose tremor is not controlled with drugs or who are not candidates for the cauterization procedure, deep-brain stimulation (thallamic stimulation) is an alternative surgical option that recently was approved by the Food and Drug Administration for treatment of both essential tremor and Parkinsonian tremor.
Unlike thalamotomy or pallidotomy, the implantable system leaves no scar on the brain. And clinical studies of this system have shown that more than 80 percent of patients with essential tremor or Parkinsonian tremor had total or significant suppression of their tremor.
The system includes an insulated wire lead that is surgically implanted deep within the thalamus and delivers mild electrical stimulation to block the brain signals that cause tremor. The lead is connected by an extension wire passed under the skin to a pulse generator, similar to an advanced cardiac pacemaker, which is implanted near the collarbone. Following surgery, the "pacemaker" is adjusted to allow individual "fine tuning" of the stimulating signal.
Patients control the stimulation by passing a hand-held magnet over the implanted pulse generator to turn it on or off, or to increase or decrease stimulation depending on their tremor suppression needs. Within hours of surgery, these patients are sipping tea from a cup and eating peas with a fork, with no signs of their disability.
The Northwestern movement disorders program is co-directed by Jeffrey Schweitzer, M.D., assistant professor of surgery, Albert Ehle, M.D., professor of neurology, and Onur Melen, M.D., assistant professor of neurology and of ophthalmology,