The Food and Drug Administration on Monday approved a bold, “deep brain” implant that promises to ease the uncontrollable tremors experienced by thousands of patients with Parkinson’s disease and another, equally disabling disorder called “essential tremor.”
The deep brain stimulator, which has been available in Europe for several years, has enabled many patients once again to eat, drink, write and perform an array of daily living activities by themselves, said Dr. Michael J. Friedman, acting FDA commissioner.
The device, an electrode that emits a steady stream of electrical pulses, has proved particularly effective for patients with severe essential tremor.
It has also significantly reduced tremors among Parkinson’s patients, but because it does not treat the other symptoms of the disease, it produced less dramatic effects on their quality of life, according to the FDA and a spokesman for Medtronics Corp., the device’s Minneapolis-based manufacturer.
Approval of the deep brain stimulator follows by one month the FDA’s go-ahead for a new Parkinson’s medication called Mirapex. The approvals mark the end of a period of little activity on medications and procedures to treat Parkinson’s, according to an FDA spokesman.
The deep brain stimulator, like the new drug, treats the symptoms of Parkinson’s but not the cause, which is the death of the brain cells that produce a chemical called dopamine. Dopamine is one of the brain’s “neurotransmitters,” which carry the nervous impulses that enable thought and control the body.
The closest thing to a cure for Parkinson’s generally available now is a transplant of fetal brain cells to replace the cells that have died in the diseased brain.
The cause of Parkinson’s disease remains unknown, although researchers recently announced they had located a faulty gene that seemed to be responsible in a family that has experienced an unusually high incidence of Parkinson’s over several generations.
The deep brain stimulator, the latest device to combat the disease, won FDA approval for use only on one side of a patient’s brain - to help control the tremor on the other side of the body. Parkinson’s typically affects one side of the body more than the other.
Studies are still under way to evaluate the safety of implanted electrodes on both sides of the brain, and no results will be available for several more months, the FDA said.
About 2 million Americans experience “essential tremor,” a little understood neurological disorder that usually runs in families. It can cause severe shaking, but few other symptoms.
Parkinson’s affects an estimated 500,000 to 1 million Americans, causing tremors, rigidity, slowness or difficulty in moving about and, in some, mental deterioration.
To implant the $25,000 “Activa Tremor Control System,” surgeons place an electrode into the thalamus, a walnut-sized region deep in the brain.
It is then connected by wire under the skin to a pacemaker implanted in the chest. Upon activation, the pacemaker sends a steady stream of tiny electrical pulses to the brain, blocking the tremor. It can be controlled by the patient, who can turn it on or off simply by placing a hand-held magnet over it. Some patients undergo dangerous surgery to destroy a small part of their brain that causes the trembling. But the surgery can cause permanent problems with speech, movement and swallowing.
FDA’s approval of the stimulator was based on a review of clinical studies conducted at about 20 medical centers in the United States and Europe.
In the U.S. studies, the device was implanted in 113 people with Parkinson’s, and 67 percent showed decreased tremors as a result. Of the 83 people with “essential tremor,” 58 percent showed improvements. The FDA said the European results were similar.
The agency is requiring the device’s maker, Medtronics Corp., of Minneapolis, to conduct additional studies to ascertain the device’s overall, long-term safety and efficacy, including the effects on patients when the lead wires break and must be replaced.
Medtronics also is to study the long-term effects of electrical stimulation on brain tissues.
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