Doctors find them useful in treating range of illnesses
Feb. 16 — The era of electrical pacemakers for the brain is dawning.
NEUROLOGISTS and neurosurgeons are finding that small electrical currents applied to central regions deep in the brain can be useful in treating a wide range of neurological and mental illnesses.
Already, neurological devices implanted in patients are used to treat tremors associated with Parkinson’s disease and give relief to those with severe pain. Now doctors have begun to explore uses of electrical brain stimulation for epilepsy, for mental illnesses such as obsessive-compulsive disorder and even for depression and addiction.
Medtronic Inc. of Minneapolis, the world leader in cardiac pacing, is expected to win approval soon from the Food and Drug Administration to use its neurological pacemaker to treat more symptoms of Parkinson’s disease, such as the rigidity, falling spells and uncontrollable twisting motions. Small medical studies are also under way for treating epilepsy and OCD with the Medtronic device, known as the Soletra. Doctors also are considering the possibility of trials for patients with depression and addiction.
Typically, the brain pacemaker is placed in the patient’s chest, with a wire surgically threaded through a 3/4-inch hole in the skull, deep into the brain. For now, the device delivers a small impulse of electricity, either in occasional bursts or steady current, to a particular region of the brain. Medtronic hopes to develop machines that will sense abnormal electrical activity in the brain, and respond with appropriate therapy. That prospect is sparking doctors’ hope the devices’ use can be expanded.
“We’re at the cusp of a new era,” says neurologist Erwin B. Montgomery of the Cleveland Clinic, who soon will begin treating obsessive-compulsive patients with the electrical devices. “Basically the brain is an electrical device, and there is growing awareness that OCD and several other conditions are related to abnormalities of electrical circuits.”
Of course, this is brain surgery. Implanting the devices can have dangerous side effects including postsurgical bleeding in about 2 percent of patients, which can lead to fatal strokes in rare instances. So the devices are intended only for patients who are suffering severe symptoms and who haven’t been helped by drugs. With OCD, about 70 percent of patients improve with antidepressant treatment. But there are at least hundreds of thousands of such patients whom drugs don’t help.
For depression sufferers, the stimulation would be a subtler means of interfering with brain signals than electric-shock treatment. And Nicolas Schiff, a neurologist at Cornell University’s Weill Medical College, envisions electrical brain stimulation helping revive semivegetative patients who have survived strokes and major trauma. “What deep brain stimulation does is push people into a better state and keep them there longer,” he says. “And these are patients who are likely to be completely overlooked.” He hopes to conduct a U.S. clinical study.
Dee Silver, medical director of the San Diego chapter of the American Parkinson Disease Association, says the Medtronic devices can lead to “dramatic improvement.”
Some doctors are taking a wait-and-see attitude. “These devices are just the first step toward more sophisticated devices,” says John G. Milton, a neurology professor at the University of Chicago Hospitals. “It works for some people, but that doesn’t mean it will work for all.” He says that a next generation of devices that are able to sense what the brain is doing “could lead to something very important.”
The first breakthroughs about treating Parkinson’s tremors with electrical currents occurred in France. In 1987, Alim-Louis Benabid, a neurosurgeon in Grenoble, discovered accidentally that electricity applied to the thalamus, in the center of the brain, could stop Parkinson’s tremors. At the time, he was using an electrical probe during surgery on an awake patient to “map” the functions of different brain regions. When an electrical current touched the thalamus, Dr. Benabid feared he had injured the patient, and apologized. The startled patient asked why, since the tremors had ceased. Soon after, Dr. Benabid began implanting neurological pacemakers for Parkinson’s tremors. Many patients who were shaking so uncontrollably that they couldn’t hold a teacup began to experience relatively normal lives.
Dr. Benabid has worked with Medtronic ever since, and now is using the technique on multiple sclerosis and other diseases that involve tremors. He has also had success treating patients with refractory epilepsy.
More recently, doctors have found that other Parkinson’s symptoms can be controlled with electricity applied to nearby brain structures, the subthalamic nucleus and the globus pallidus. Ali Rezai, a neurosurgeon at the Cleveland Clinic, says deep brain stimulation reduces tremors by more than 90% and other Parkinson’s symptoms like rigidity and writhing motions by about 60%. “As far as helping these patients, this is a dramatic advance,” he says. He describes similar improvement in patients with debilitating pain from strokes and nerve-crushing injuries.
Medtronic first began about 30 years ago to apply some of this electrical-stimulation technology to the central nervous system, stimulating the spinal cords of patients with severe pain. It has the field essentially to itself now, though Cyberonics Inc. of Houston treats epilepsy with electrical stimulation to a nerve in the neck.
Doctors have particularly high hopes for treating epilepsy with neurological pacemakers, though that use is still being investigated.
“Epilepsy is an electrical storm in the brain, and it should be possible in theory to disrupt seizures by changing the epileptic electrical pattern,” says neurologist Robert S. Fisher of Stanford University Medical Center. Though drugs and other surgery help many patients, “We have about half a million people in the U.S. alone for whom no existing treatment really works,” Dr. Fisher says.
Many such patients cannot get through an hour of their lives without a seizure. So far, 10 patients with electrical devices have been followed for several months at hospitals like Johns Hopkins in Baltimore and the University of Pennsylvania. “People seem to have about a 75 percent reduction in seizure frequency,” says Dr. Fisher, who is heading a study of the treatment. He says the “most exciting” hope for electrical therapy will occur when devices are able to detect an oncoming seizure and respond to it with the proper current.
Steven Rasmussen, a psychiatry professor at Brown University Medical School in Providence, R.I., says about 375,000 Americans with progressive and debilitating obsessive-compulsive disorder are candidates for surgery, including the installation of an electrical device.
In a small pilot study so far, says Dr. Rasmussen, about 50% of patients who fail to respond to other treatment, improve with deep brain stimulation. Because of the public furor over lobotomies in the past, doctors are going slowly with surgical techniques. But because electrical stimulation is both adjustable and reversible, there are fewer concerns regarding this therapy.
Even so, only a handful of leading hospitals are trying it in obsessive-compulsive patients. Brown University is one, and the Cleveland Clinic soon will begin such treatment. Cleveland Clinic neurosurgeon Dr. Rezai notes these patients are often unable to work or go to school; he says they can take eight hours to wash up, or check the locks in their houses hundreds of times and be unable to stop doing so.
Beyond OCD, Dr. Rasmussen predicts that there are a number of other opportunities in the psychiatric field for the use of electrical devices-including addictions that can’t be controlled by drugs. “There is undoubtedly a neurocircuitry in these psychiatric conditions,” he says.
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